feat: NCS-13 Implement Threefold Repetition (#31)

Reviewed-on: #31

.claude/memory/MEMORY.md

@@ -1,9 +0,0 @@
-# Memory Index
-
-## Feedback
-- [feedback_keep_structure_updated.md](feedback_keep_structure_updated.md) — Update structure memory files whenever source files are added, removed, or changed
-
-## Project Structure
-- [project_structure_root.md](project_structure_root.md) — Top-level layout, modules list, VERSIONS map, navigation rules (skip `build/`, `.gradle/`, `.idea/`)
-- [project_structure_api.md](project_structure_api.md) — `modules/api`: all files and types (Board, Piece, Square, GameState, Move, ApiResponse, PlayerInfo)
-- [project_structure_core.md](project_structure_core.md) — `modules/core`: all files and types (GameContext, GameRules, MoveValidator, GameController, Parser, Renderer)

.claude/memory/feedback_keep_structure_updated.md

@@ -1,16 +0,0 @@
----
-name: keep-structure-memory-updated
-description: Always update the project structure memory files when adding, removing, or changing source files
-type: feedback
----
-
-After any change that adds, removes, renames, or significantly alters a source file, update the relevant structure memory file:
-
-- New/renamed/deleted file in `modules/api` → update `project_structure_api.md`
-- New/renamed/deleted file in `modules/core` → update `project_structure_core.md`
-- New module, dependency version change, or new top-level directory → update `project_structure_root.md`
-- New module added → create a new `project_structure_<module>.md` and add it to `MEMORY.md`
-
-**Why:** Structure memories are the primary navigation aid. Stale entries cause wasted exploration.
-
-**How to apply:** Treat the structure memory update as part of completing any implementation task — do it in the same session, not as a follow-up.

.claude/memory/project_structure_api.md

@@ -1,51 +0,0 @@
----
-name: module-api-structure
-description: File and type overview for the modules/api module (shared domain types)
-type: project
----
-
-# Module: `modules/api`
-
-**Purpose:** Shared domain model — pure data types with no game logic. Depended on by `modules/core`.
-
-**Gradle:** `id("scala")`, no `application` plugin. No Quarkus. Uses scoverage plugin.
-
-**Package root:** `de.nowchess.api`
-
-## Source files (`src/main/scala/de/nowchess/api/`)
-
-### `board/`
-| File | Contents |
-|------|----------|
-| `Board.scala` | `opaque type Board = Map[Square, Piece]` — extensions: `pieceAt`, `withMove`, `pieces`; `Board.initial` sets up start position |
-| `Color.scala` | `enum Color { White, Black }` — `.opposite`, `.label` |
-| `Piece.scala` | `case class Piece(color, pieceType)` — convenience vals `WhitePawn`…`BlackKing` |
-| `PieceType.scala` | `enum PieceType { Pawn, Knight, Bishop, Rook, Queen, King }` — `.label` |
-| `Square.scala` | `enum File { A–H }`, `enum Rank { R1–R8 }`, `case class Square(file, rank)` — `.toString` algebraic, `Square.fromAlgebraic(s)` |
-
-### `game/`
-| File | Contents |
-|------|----------|
-| `GameState.scala` | `case class CastlingRights(kingSide, queenSide)` + `.None`/`.Both`; `enum GameResult { WhiteWins, BlackWins, Draw }`; `enum GameStatus { NotStarted, InProgress, Finished(result) }`; `case class GameState(piecePlacement, activeColor, castlingWhite, castlingBlack, enPassantTarget, halfMoveClock, fullMoveNumber, status)` — FEN-compatible snapshot |
-
-### `move/`
-| File | Contents |
-|------|----------|
-| `Move.scala` | `enum PromotionPiece { Knight, Bishop, Rook, Queen }`; `enum MoveType { Normal, CastleKingside, CastleQueenside, EnPassant, Promotion(piece) }`; `case class Move(from, to, moveType = Normal)` |
-
-### `player/`
-| File | Contents |
-|------|----------|
-| `PlayerInfo.scala` | `opaque type PlayerId = String`; `case class PlayerInfo(id: PlayerId, displayName: String)` |
-
-### `response/`
-| File | Contents |
-|------|----------|
-| `ApiResponse.scala` | `sealed trait ApiResponse[+A]` → `Success[A](data)` / `Failure(errors)`; `case class ApiError(code, message, field?)`; `case class Pagination(page, pageSize, totalItems)` + `.totalPages`; `case class PagedResponse[A](items, pagination)` |
-
-## Test files (`src/test/scala/de/nowchess/api/`)
-Mirror of main structure — one `*Test.scala` per source file using `AnyFunSuite with Matchers`.
-
-## Notes
-- `GameState` is FEN-style but `Board` (in `core`) is a `Map[Square,Piece]` — the two are separate representations
-- `CastlingRights` is defined here in `api`; the castling logic lives in `core`

.claude/memory/project_structure_core.md

@@ -1,48 +0,0 @@
----
-name: module-core-structure
-description: File and type overview for the modules/core module (TUI chess engine)
-type: project
----
-
-# Module: `modules/core`
-
-**Purpose:** Standalone TUI chess application. All game logic, move validation, rendering. Depends on `modules/api`.
-
-**Gradle:** `id("scala")` + `application` plugin. Main class: `de.nowchess.chess.Main`. Uses scoverage plugin.
-
-**Package root:** `de.nowchess.chess`
-
-## Source files (`src/main/scala/de/nowchess/chess/`)
-
-### Root
-| File | Contents |
-|------|----------|
-| `Main.scala` | Entry point — prints welcome, starts `GameController.gameLoop(GameContext.initial, Color.White)` |
-
-### `controller/`
-| File | Contents |
-|------|----------|
-| `GameController.scala` | `sealed trait MoveResult` ADT: `Quit`, `InvalidFormat`, `NoPiece`, `WrongColor`, `IllegalMove`, `Moved`, `MovedInCheck`, `Checkmate`, `Stalemate`; `object GameController` — `processMove(ctx, turn, raw): MoveResult` (pure), `gameLoop(ctx, turn)` (I/O loop), `applyRightsRevocation(...)` (castling rights bookkeeping) |
-| `Parser.scala` | `object Parser` — `parseMove(input): Option[(Square, Square)]` parses coordinate notation e.g. `"e2e4"` |
-
-### `logic/`
-| File | Contents |
-|------|----------|
-| `GameContext.scala` | `enum CastleSide { Kingside, Queenside }`; `case class GameContext(board, whiteCastling, blackCastling)` — `.castlingFor(color)`, `.withUpdatedRights(color, rights)`; `GameContext.initial`; `extension (Board).withCastle(color, side)` moves king+rook atomically |
-| `GameRules.scala` | `enum PositionStatus { Normal, InCheck, Mated, Drawn }`; `object GameRules` — `isInCheck(board, color)`, `legalMoves(ctx, color): Set[(Square,Square)]`, `gameStatus(ctx, color): PositionStatus` |
-| `MoveValidator.scala` | `object MoveValidator` — `isLegal(board, from, to)`, `legalTargets(board, from): Set[Square]` (board-only, no castling), `legalTargets(ctx, from)` (context-aware, includes castling), `isCastle`, `castleSide`, `castlingTargets(ctx, color)` — full castling legality (empty squares, no check through transit) |
-
-### `view/`
-| File | Contents |
-|------|----------|
-| `Renderer.scala` | `object Renderer` — `render(board): String` outputs ANSI-colored board with file/rank labels |
-| `PieceUnicode.scala` | `extension (Piece).unicode: String` maps each piece to its Unicode chess symbol |
-
-## Test files (`src/test/scala/de/nowchess/chess/`)
-Mirror of main structure — one `*Test.scala` per source file using `AnyFunSuite with Matchers`.
-
-## Key design notes
-- `MoveValidator` has two overloaded `legalTargets`: one takes `Board` (geometry only), one takes `GameContext` (adds castling)
-- `GameRules.legalMoves` filters by check — it calls `MoveValidator.legalTargets(ctx, from)` then simulates each move
-- Castling rights revocation is in `GameController.applyRightsRevocation`, triggered after every move
-- No `@QuarkusTest` — this module is a plain Scala application, not a Quarkus service

.claude/memory/project_structure_root.md

@@ -1,55 +0,0 @@
----
-name: project-root-structure
-description: Top-level project structure, modules list, and navigation notes for NowChessSystems
-type: project
----
-
-# NowChessSystems — Root Structure
-
-## Directory layout (skip `build/`, `.gradle/`, `.idea/`)
-
-```
-NowChessSystems/
-├── build.gradle.kts          # Root: sonarqube plugin, VERSIONS map
-├── settings.gradle.kts       # include(":modules:core", ":modules:api")
-├── gradlew / gradlew.bat
-├── CLAUDE.md                 # Project instructions for Claude Code
-├── .claude/
-│   ├── CLAUDE.MD             # Working agreement (plan/verify/unresolved)
-│   ├── settings.json
-│   └── agents/               # architect, code-reviewer, gradle-builder, scala-implementer, test-writer
-├── docs/
-│   ├── Claude-Skills.md
-│   ├── Security.md
-│   └── unresolved.md
-├── jacoco-reporter/          # Python scripts for coverage gap reporting
-└── modules/
-    ├── api/                  # Shared domain types (no logic)
-    └── core/                 # TUI chess engine + game logic
-```
-
-## Modules
-
-| Module | Gradle path | Purpose |
-|--------|-------------|---------|
-| `api` | `:modules:api` | Shared domain model: Board, Piece, Move, GameState, ApiResponse |
-| `core` | `:modules:core` | TUI chess app: game logic, move validation, rendering |
-
-`core` depends on `api` via `implementation(project(":modules:api"))`.
-
-## VERSIONS (root `build.gradle.kts`)
-
-| Key | Value |
-|-----|-------|
-| `QUARKUS_SCALA3` | 1.0.0 |
-| `SCALA3` | 3.5.1 |
-| `SCALA_LIBRARY` | 2.13.18 |
-| `SCALATEST` | 3.2.19 |
-| `SCALATEST_JUNIT` | 0.1.11 |
-| `SCOVERAGE` | 2.1.1 |
-
-## Navigation rules
-- **Always skip** `build/`, `.gradle/`, `.idea/` when exploring — they are generated artifacts
-- Tests use `AnyFunSuite with Matchers` (ScalaTest), not JUnit `@Test`
-- No Quarkus in current modules — Quarkus is planned for future services
-- Agent workflow: architect → scala-implementer → test-writer → gradle-builder → code-reviewer

.claude/settings.json

@@ -1,6 +1,6 @@
 {
   "enabledPlugins": {
-    "superpowers@claude-plugins-official": true,
-    "ui-ux-pro-max@ui-ux-pro-max-skill": true
+    "superpowers@claude-plugins-official": false,
+    "ui-ux-pro-max@ui-ux-pro-max-skill": false
   }
 }

.codesight/CODESIGHT.md

@@ -0,0 +1,203 @@
+# NowChessSystems — AI Context Map
+
+> **Stack:** raw-http | none | unknown | scala
+
+> 0 routes | 0 models | 0 components | 35 lib files | 0 env vars | 0 middleware
+> **Token savings:** this file is ~3.700 tokens. Without it, AI exploration would cost ~18.200 tokens. **Saves ~14.500 tokens per conversation.**
+
+---
+
+# Libraries
+
+- `jacoco-reporter/scoverage_coverage_gaps.py`
+  - function parse_scoverage_xml: (xml_path) -> tuple[dict, list[ClassGap]]
+  - function format_agent: (project_stats, classes) -> str
+  - function format_json: (project_stats, classes) -> str
+  - function format_markdown: (project_stats, classes) -> str
+  - function format_module_gaps: (module_name, classes, stmt_pct) -> str
+  - function run_scan_modules: (modules_dir, package_filter, min_coverage) -> None
+  - _...4 more_
+- `jacoco-reporter/test_gaps.py`
+  - function parse_suite_xml: (xml_path) -> SuiteResult
+  - function load_module: (module_dir, results_subdir) -> Optional[ModuleResult]
+  - function format_module: (mod) -> str
+  - function run: (modules_dir, results_subdir, module_filter) -> None
+  - function main: () -> None
+  - class TestCase
+  - _...2 more_
+- `modules/api/src/main/scala/de/nowchess/api/board/Board.scala`
+  - class Board
+  - function apply
+  - function pieceAt
+  - function updated
+  - function removed
+  - function withMove
+  - _...2 more_
+- `modules/api/src/main/scala/de/nowchess/api/board/CastlingRights.scala`
+  - function hasAnyRights
+  - function hasRights
+  - function revokeColor
+  - function revokeKingSide
+  - function revokeQueenSide
+  - class CastlingRights
+- `modules/api/src/main/scala/de/nowchess/api/board/Color.scala` — function opposite, function label
+- `modules/api/src/main/scala/de/nowchess/api/board/Piece.scala` — class Piece
+- `modules/api/src/main/scala/de/nowchess/api/board/PieceType.scala` — function label
+- `modules/api/src/main/scala/de/nowchess/api/board/Square.scala`
+  - class Square
+  - function fromAlgebraic
+  - function offset
+- `modules/api/src/main/scala/de/nowchess/api/game/GameContext.scala`
+  - function withBoard
+  - function withTurn
+  - function withCastlingRights
+  - function withEnPassantSquare
+  - function withHalfMoveClock
+  - function withMove
+  - _...2 more_
+- `modules/api/src/main/scala/de/nowchess/api/player/PlayerInfo.scala` — class PlayerId, function apply
+- `modules/api/src/main/scala/de/nowchess/api/response/ApiResponse.scala`
+  - class ApiResponse
+  - function error
+  - function totalPages
+- `modules/core/src/main/scala/de/nowchess/chess/command/Command.scala`
+  - class Command
+  - function execute
+  - function undo
+  - function description
+  - class MoveResult
+- `modules/core/src/main/scala/de/nowchess/chess/command/CommandInvoker.scala`
+  - class CommandInvoker
+  - function execute
+  - function undo
+  - function redo
+  - function history
+  - function getCurrentIndex
+  - _...3 more_
+- `modules/core/src/main/scala/de/nowchess/chess/controller/Parser.scala` — class Parser, function parseMove
+- `modules/core/src/main/scala/de/nowchess/chess/engine/GameEngine.scala`
+  - class GameEngine
+  - function isPendingPromotion
+  - function board
+  - function turn
+  - function context
+  - function canUndo
+  - _...10 more_
+- `modules/core/src/main/scala/de/nowchess/chess/observer/Observer.scala`
+  - function context
+  - class Observer
+  - function onGameEvent
+  - class Observable
+  - function subscribe
+  - function unsubscribe
+  - _...1 more_
+- `modules/io/src/main/scala/de/nowchess/io/GameContextExport.scala` — class GameContextExport, function exportGameContext
+- `modules/io/src/main/scala/de/nowchess/io/GameContextImport.scala` — class GameContextImport, function importGameContext
+- `modules/io/src/main/scala/de/nowchess/io/fen/FenExporter.scala`
+  - class FenExporter
+  - function boardToFen
+  - function gameContextToFen
+  - function exportGameContext
+- `modules/io/src/main/scala/de/nowchess/io/fen/FenParser.scala`
+  - class FenParser
+  - function parseFen
+  - function importGameContext
+  - function parseBoard
+- `modules/io/src/main/scala/de/nowchess/io/fen/FenParserCombinators.scala`
+  - class FenParserCombinators
+  - function parseFen
+  - function parseBoard
+  - function importGameContext
+- `modules/io/src/main/scala/de/nowchess/io/fen/FenParserFastParse.scala`
+  - class FenParserFastParse
+  - function parseFen
+  - function parseBoard
+  - function importGameContext
+- `modules/io/src/main/scala/de/nowchess/io/fen/FenParserSupport.scala` — function buildSquares
+- `modules/io/src/main/scala/de/nowchess/io/pgn/PgnExporter.scala`
+  - class PgnExporter
+  - function exportGameContext
+  - function exportGame
+- `modules/io/src/main/scala/de/nowchess/io/pgn/PgnParser.scala`
+  - class PgnParser
+  - function validatePgn
+  - function importGameContext
+  - function parsePgn
+  - function parseAlgebraicMove
+- `modules/rule/src/main/scala/de/nowchess/rules/RuleSet.scala`
+  - class RuleSet
+  - function candidateMoves
+  - function legalMoves
+  - function allLegalMoves
+  - function isCheck
+  - function isCheckmate
+  - _...4 more_
+- `modules/rule/src/main/scala/de/nowchess/rules/sets/DefaultRules.scala`
+  - class DefaultRules
+  - function loop
+  - function toMoves
+  - function loop
+- `modules/ui/src/main/scala/de/nowchess/ui/Main.scala` — class Main, function main
+- `modules/ui/src/main/scala/de/nowchess/ui/gui/ChessBoardView.scala`
+  - class ChessBoardView
+  - function updateBoard
+  - function updateUndoRedoButtons
+  - function showMessage
+  - function showPromotionDialog
+- `modules/ui/src/main/scala/de/nowchess/ui/gui/ChessGUI.scala`
+  - class ChessGUIApp
+  - class ChessGUILauncher
+  - function getEngine
+  - function launch
+- `modules/ui/src/main/scala/de/nowchess/ui/gui/GUIObserver.scala` — class GUIObserver
+- `modules/ui/src/main/scala/de/nowchess/ui/gui/PieceSprites.scala`
+  - class PieceSprites
+  - function loadPieceImage
+  - class SquareColors
+- `modules/ui/src/main/scala/de/nowchess/ui/terminal/TerminalUI.scala` — class TerminalUI, function start
+- `modules/ui/src/main/scala/de/nowchess/ui/utils/PieceUnicode.scala` — function unicode
+- `modules/ui/src/main/scala/de/nowchess/ui/utils/Renderer.scala` — class Renderer, function render
+
+---
+
+# Dependency Graph
+
+## Most Imported Files (change these carefully)
+
+- `modules/api/src/main/scala/de/nowchess/api/game/GameContext.scala` — imported by **28** files
+- `modules/api/src/main/scala/de/nowchess/api/board/Square.scala` — imported by **21** files
+- `modules/api/src/main/scala/de/nowchess/api/board/Color.scala` — imported by **19** files
+- `modules/api/src/main/scala/de/nowchess/api/move/Move.scala` — imported by **14** files
+- `modules/api/src/main/scala/de/nowchess/api/board/Board.scala` — imported by **13** files
+- `modules/api/src/main/scala/de/nowchess/api/board/Piece.scala` — imported by **10** files
+- `modules/api/src/main/scala/de/nowchess/api/board/PieceType.scala` — imported by **9** files
+- `modules/io/src/main/scala/de/nowchess/io/fen/FenParser.scala` — imported by **9** files
+- `modules/rule/src/main/scala/de/nowchess/rules/sets/DefaultRules.scala` — imported by **8** files
+- `modules/io/src/main/scala/de/nowchess/io/GameContextImport.scala` — imported by **7** files
+- `modules/api/src/main/scala/de/nowchess/api/board/CastlingRights.scala` — imported by **4** files
+- `modules/io/src/main/scala/de/nowchess/io/GameContextExport.scala` — imported by **4** files
+- `modules/rule/src/main/scala/de/nowchess/rules/RuleSet.scala` — imported by **4** files
+- `modules/core/src/main/scala/de/nowchess/chess/observer/Observer.scala` — imported by **4** files
+- `modules/core/src/main/scala/de/nowchess/chess/engine/GameEngine.scala` — imported by **4** files
+- `modules/io/src/main/scala/de/nowchess/io/pgn/PgnParser.scala` — imported by **2** files
+- `modules/io/src/main/scala/de/nowchess/io/pgn/PgnExporter.scala` — imported by **2** files
+- `modules/io/src/main/scala/de/nowchess/io/fen/FenExporter.scala` — imported by **2** files
+- `modules/io/src/main/scala/de/nowchess/io/fen/FenParserSupport.scala` — imported by **2** files
+- `modules/core/src/main/scala/de/nowchess/chess/controller/Parser.scala` — imported by **1** files
+
+## Import Map (who imports what)
+
+- `modules/api/src/main/scala/de/nowchess/api/game/GameContext.scala` ← `modules/core/src/main/scala/de/nowchess/chess/command/Command.scala`, `modules/core/src/main/scala/de/nowchess/chess/engine/GameEngine.scala`, `modules/core/src/main/scala/de/nowchess/chess/observer/Observer.scala`, `modules/core/src/test/scala/de/nowchess/chess/command/CommandInvokerBranchTest.scala`, `modules/core/src/test/scala/de/nowchess/chess/command/CommandInvokerTest.scala` +23 more
+- `modules/api/src/main/scala/de/nowchess/api/board/Square.scala` ← `modules/api/src/main/scala/de/nowchess/api/game/GameContext.scala`, `modules/api/src/main/scala/de/nowchess/api/move/Move.scala`, `modules/api/src/test/scala/de/nowchess/api/game/GameContextTest.scala`, `modules/api/src/test/scala/de/nowchess/api/move/MoveTest.scala`, `modules/core/src/main/scala/de/nowchess/chess/command/Command.scala` +16 more
+- `modules/api/src/main/scala/de/nowchess/api/board/Color.scala` ← `modules/api/src/main/scala/de/nowchess/api/game/GameContext.scala`, `modules/api/src/test/scala/de/nowchess/api/game/GameContextTest.scala`, `modules/core/src/main/scala/de/nowchess/chess/engine/GameEngine.scala`, `modules/core/src/main/scala/de/nowchess/chess/observer/Observer.scala`, `modules/core/src/test/scala/de/nowchess/chess/engine/EngineTestHelpers.scala` +14 more
+- `modules/api/src/main/scala/de/nowchess/api/move/Move.scala` ← `modules/api/src/main/scala/de/nowchess/api/game/GameContext.scala`, `modules/api/src/test/scala/de/nowchess/api/board/BoardTest.scala`, `modules/api/src/test/scala/de/nowchess/api/game/GameContextTest.scala`, `modules/core/src/main/scala/de/nowchess/chess/engine/GameEngine.scala`, `modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineIntegrationTest.scala` +9 more
+- `modules/api/src/main/scala/de/nowchess/api/board/Board.scala` ← `modules/api/src/main/scala/de/nowchess/api/game/GameContext.scala`, `modules/api/src/test/scala/de/nowchess/api/game/GameContextTest.scala`, `modules/core/src/main/scala/de/nowchess/chess/engine/GameEngine.scala`, `modules/core/src/test/scala/de/nowchess/chess/engine/EngineTestHelpers.scala`, `modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineGameEndingTest.scala` +8 more
+- `modules/api/src/main/scala/de/nowchess/api/board/Piece.scala` ← `modules/core/src/main/scala/de/nowchess/chess/command/Command.scala`, `modules/core/src/main/scala/de/nowchess/chess/engine/GameEngine.scala`, `modules/core/src/test/scala/de/nowchess/chess/engine/GameEnginePromotionTest.scala`, `modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineScenarioTest.scala`, `modules/rule/src/test/scala/de/nowchess/rule/DefaultRulesStateTransitionsTest.scala` +5 more
+- `modules/api/src/main/scala/de/nowchess/api/board/PieceType.scala` ← `modules/core/src/main/scala/de/nowchess/chess/engine/GameEngine.scala`, `modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineIntegrationTest.scala`, `modules/core/src/test/scala/de/nowchess/chess/engine/GameEnginePromotionTest.scala`, `modules/rule/src/test/scala/de/nowchess/rule/DefaultRulesStateTransitionsTest.scala`, `modules/rule/src/test/scala/de/nowchess/rule/DefaultRulesTest.scala` +4 more
+- `modules/io/src/main/scala/de/nowchess/io/fen/FenParser.scala` ← `modules/core/src/test/scala/de/nowchess/chess/engine/EngineTestHelpers.scala`, `modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineLoadGameTest.scala`, `modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineNotationTest.scala`, `modules/core/src/test/scala/de/nowchess/chess/engine/GameEnginePromotionTest.scala`, `modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineScenarioTest.scala` +4 more
+- `modules/rule/src/main/scala/de/nowchess/rules/sets/DefaultRules.scala` ← `modules/core/src/main/scala/de/nowchess/chess/engine/GameEngine.scala`, `modules/core/src/test/scala/de/nowchess/chess/engine/EngineTestHelpers.scala`, `modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineIntegrationTest.scala`, `modules/core/src/test/scala/de/nowchess/chess/engine/GameEnginePromotionTest.scala`, `modules/io/src/main/scala/de/nowchess/io/pgn/PgnExporter.scala` +3 more
+- `modules/io/src/main/scala/de/nowchess/io/GameContextImport.scala` ← `modules/core/src/main/scala/de/nowchess/chess/engine/GameEngine.scala`, `modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineIntegrationTest.scala`, `modules/io/src/main/scala/de/nowchess/io/fen/FenParser.scala`, `modules/io/src/main/scala/de/nowchess/io/fen/FenParserCombinators.scala`, `modules/io/src/main/scala/de/nowchess/io/fen/FenParserFastParse.scala` +2 more
+
+---
+
+_Generated by [codesight](https://github.com/Houseofmvps/codesight) — see your codebase clearly_

.codesight/graph.md

@@ -0,0 +1,37 @@
+# Dependency Graph
+
+## Most Imported Files (change these carefully)
+
+- `modules/api/src/main/scala/de/nowchess/api/game/GameContext.scala` — imported by **28** files
+- `modules/api/src/main/scala/de/nowchess/api/board/Square.scala` — imported by **21** files
+- `modules/api/src/main/scala/de/nowchess/api/board/Color.scala` — imported by **19** files
+- `modules/api/src/main/scala/de/nowchess/api/move/Move.scala` — imported by **14** files
+- `modules/api/src/main/scala/de/nowchess/api/board/Board.scala` — imported by **13** files
+- `modules/api/src/main/scala/de/nowchess/api/board/Piece.scala` — imported by **10** files
+- `modules/api/src/main/scala/de/nowchess/api/board/PieceType.scala` — imported by **9** files
+- `modules/io/src/main/scala/de/nowchess/io/fen/FenParser.scala` — imported by **9** files
+- `modules/rule/src/main/scala/de/nowchess/rules/sets/DefaultRules.scala` — imported by **8** files
+- `modules/io/src/main/scala/de/nowchess/io/GameContextImport.scala` — imported by **7** files
+- `modules/api/src/main/scala/de/nowchess/api/board/CastlingRights.scala` — imported by **4** files
+- `modules/io/src/main/scala/de/nowchess/io/GameContextExport.scala` — imported by **4** files
+- `modules/rule/src/main/scala/de/nowchess/rules/RuleSet.scala` — imported by **4** files
+- `modules/core/src/main/scala/de/nowchess/chess/observer/Observer.scala` — imported by **4** files
+- `modules/core/src/main/scala/de/nowchess/chess/engine/GameEngine.scala` — imported by **4** files
+- `modules/io/src/main/scala/de/nowchess/io/pgn/PgnParser.scala` — imported by **2** files
+- `modules/io/src/main/scala/de/nowchess/io/pgn/PgnExporter.scala` — imported by **2** files
+- `modules/io/src/main/scala/de/nowchess/io/fen/FenExporter.scala` — imported by **2** files
+- `modules/io/src/main/scala/de/nowchess/io/fen/FenParserSupport.scala` — imported by **2** files
+- `modules/core/src/main/scala/de/nowchess/chess/controller/Parser.scala` — imported by **1** files
+
+## Import Map (who imports what)
+
+- `modules/api/src/main/scala/de/nowchess/api/game/GameContext.scala` ← `modules/core/src/main/scala/de/nowchess/chess/command/Command.scala`, `modules/core/src/main/scala/de/nowchess/chess/engine/GameEngine.scala`, `modules/core/src/main/scala/de/nowchess/chess/observer/Observer.scala`, `modules/core/src/test/scala/de/nowchess/chess/command/CommandInvokerBranchTest.scala`, `modules/core/src/test/scala/de/nowchess/chess/command/CommandInvokerTest.scala` +23 more
+- `modules/api/src/main/scala/de/nowchess/api/board/Square.scala` ← `modules/api/src/main/scala/de/nowchess/api/game/GameContext.scala`, `modules/api/src/main/scala/de/nowchess/api/move/Move.scala`, `modules/api/src/test/scala/de/nowchess/api/game/GameContextTest.scala`, `modules/api/src/test/scala/de/nowchess/api/move/MoveTest.scala`, `modules/core/src/main/scala/de/nowchess/chess/command/Command.scala` +16 more
+- `modules/api/src/main/scala/de/nowchess/api/board/Color.scala` ← `modules/api/src/main/scala/de/nowchess/api/game/GameContext.scala`, `modules/api/src/test/scala/de/nowchess/api/game/GameContextTest.scala`, `modules/core/src/main/scala/de/nowchess/chess/engine/GameEngine.scala`, `modules/core/src/main/scala/de/nowchess/chess/observer/Observer.scala`, `modules/core/src/test/scala/de/nowchess/chess/engine/EngineTestHelpers.scala` +14 more
+- `modules/api/src/main/scala/de/nowchess/api/move/Move.scala` ← `modules/api/src/main/scala/de/nowchess/api/game/GameContext.scala`, `modules/api/src/test/scala/de/nowchess/api/board/BoardTest.scala`, `modules/api/src/test/scala/de/nowchess/api/game/GameContextTest.scala`, `modules/core/src/main/scala/de/nowchess/chess/engine/GameEngine.scala`, `modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineIntegrationTest.scala` +9 more
+- `modules/api/src/main/scala/de/nowchess/api/board/Board.scala` ← `modules/api/src/main/scala/de/nowchess/api/game/GameContext.scala`, `modules/api/src/test/scala/de/nowchess/api/game/GameContextTest.scala`, `modules/core/src/main/scala/de/nowchess/chess/engine/GameEngine.scala`, `modules/core/src/test/scala/de/nowchess/chess/engine/EngineTestHelpers.scala`, `modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineGameEndingTest.scala` +8 more
+- `modules/api/src/main/scala/de/nowchess/api/board/Piece.scala` ← `modules/core/src/main/scala/de/nowchess/chess/command/Command.scala`, `modules/core/src/main/scala/de/nowchess/chess/engine/GameEngine.scala`, `modules/core/src/test/scala/de/nowchess/chess/engine/GameEnginePromotionTest.scala`, `modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineScenarioTest.scala`, `modules/rule/src/test/scala/de/nowchess/rule/DefaultRulesStateTransitionsTest.scala` +5 more
+- `modules/api/src/main/scala/de/nowchess/api/board/PieceType.scala` ← `modules/core/src/main/scala/de/nowchess/chess/engine/GameEngine.scala`, `modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineIntegrationTest.scala`, `modules/core/src/test/scala/de/nowchess/chess/engine/GameEnginePromotionTest.scala`, `modules/rule/src/test/scala/de/nowchess/rule/DefaultRulesStateTransitionsTest.scala`, `modules/rule/src/test/scala/de/nowchess/rule/DefaultRulesTest.scala` +4 more
+- `modules/io/src/main/scala/de/nowchess/io/fen/FenParser.scala` ← `modules/core/src/test/scala/de/nowchess/chess/engine/EngineTestHelpers.scala`, `modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineLoadGameTest.scala`, `modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineNotationTest.scala`, `modules/core/src/test/scala/de/nowchess/chess/engine/GameEnginePromotionTest.scala`, `modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineScenarioTest.scala` +4 more
+- `modules/rule/src/main/scala/de/nowchess/rules/sets/DefaultRules.scala` ← `modules/core/src/main/scala/de/nowchess/chess/engine/GameEngine.scala`, `modules/core/src/test/scala/de/nowchess/chess/engine/EngineTestHelpers.scala`, `modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineIntegrationTest.scala`, `modules/core/src/test/scala/de/nowchess/chess/engine/GameEnginePromotionTest.scala`, `modules/io/src/main/scala/de/nowchess/io/pgn/PgnExporter.scala` +3 more
+- `modules/io/src/main/scala/de/nowchess/io/GameContextImport.scala` ← `modules/core/src/main/scala/de/nowchess/chess/engine/GameEngine.scala`, `modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineIntegrationTest.scala`, `modules/io/src/main/scala/de/nowchess/io/fen/FenParser.scala`, `modules/io/src/main/scala/de/nowchess/io/fen/FenParserCombinators.scala`, `modules/io/src/main/scala/de/nowchess/io/fen/FenParserFastParse.scala` +2 more

.codesight/libs.md

@@ -0,0 +1,150 @@
+# Libraries
+
+- `jacoco-reporter/scoverage_coverage_gaps.py`
+  - function parse_scoverage_xml: (xml_path) -> tuple[dict, list[ClassGap]]
+  - function format_agent: (project_stats, classes) -> str
+  - function format_json: (project_stats, classes) -> str
+  - function format_markdown: (project_stats, classes) -> str
+  - function format_module_gaps: (module_name, classes, stmt_pct) -> str
+  - function run_scan_modules: (modules_dir, package_filter, min_coverage) -> None
+  - _...4 more_
+- `jacoco-reporter/test_gaps.py`
+  - function parse_suite_xml: (xml_path) -> SuiteResult
+  - function load_module: (module_dir, results_subdir) -> Optional[ModuleResult]
+  - function format_module: (mod) -> str
+  - function run: (modules_dir, results_subdir, module_filter) -> None
+  - function main: () -> None
+  - class TestCase
+  - _...2 more_
+- `modules/api/src/main/scala/de/nowchess/api/board/Board.scala`
+  - class Board
+  - function apply
+  - function pieceAt
+  - function updated
+  - function removed
+  - function withMove
+  - _...2 more_
+- `modules/api/src/main/scala/de/nowchess/api/board/CastlingRights.scala`
+  - function hasAnyRights
+  - function hasRights
+  - function revokeColor
+  - function revokeKingSide
+  - function revokeQueenSide
+  - class CastlingRights
+- `modules/api/src/main/scala/de/nowchess/api/board/Color.scala` — function opposite, function label
+- `modules/api/src/main/scala/de/nowchess/api/board/Piece.scala` — class Piece
+- `modules/api/src/main/scala/de/nowchess/api/board/PieceType.scala` — function label
+- `modules/api/src/main/scala/de/nowchess/api/board/Square.scala`
+  - class Square
+  - function fromAlgebraic
+  - function offset
+- `modules/api/src/main/scala/de/nowchess/api/game/GameContext.scala`
+  - function withBoard
+  - function withTurn
+  - function withCastlingRights
+  - function withEnPassantSquare
+  - function withHalfMoveClock
+  - function withMove
+  - _...2 more_
+- `modules/api/src/main/scala/de/nowchess/api/player/PlayerInfo.scala` — class PlayerId, function apply
+- `modules/api/src/main/scala/de/nowchess/api/response/ApiResponse.scala`
+  - class ApiResponse
+  - function error
+  - function totalPages
+- `modules/core/src/main/scala/de/nowchess/chess/command/Command.scala`
+  - class Command
+  - function execute
+  - function undo
+  - function description
+  - class MoveResult
+- `modules/core/src/main/scala/de/nowchess/chess/command/CommandInvoker.scala`
+  - class CommandInvoker
+  - function execute
+  - function undo
+  - function redo
+  - function history
+  - function getCurrentIndex
+  - _...3 more_
+- `modules/core/src/main/scala/de/nowchess/chess/controller/Parser.scala` — class Parser, function parseMove
+- `modules/core/src/main/scala/de/nowchess/chess/engine/GameEngine.scala`
+  - class GameEngine
+  - function isPendingPromotion
+  - function board
+  - function turn
+  - function context
+  - function canUndo
+  - _...10 more_
+- `modules/core/src/main/scala/de/nowchess/chess/observer/Observer.scala`
+  - function context
+  - class Observer
+  - function onGameEvent
+  - class Observable
+  - function subscribe
+  - function unsubscribe
+  - _...1 more_
+- `modules/io/src/main/scala/de/nowchess/io/GameContextExport.scala` — class GameContextExport, function exportGameContext
+- `modules/io/src/main/scala/de/nowchess/io/GameContextImport.scala` — class GameContextImport, function importGameContext
+- `modules/io/src/main/scala/de/nowchess/io/fen/FenExporter.scala`
+  - class FenExporter
+  - function boardToFen
+  - function gameContextToFen
+  - function exportGameContext
+- `modules/io/src/main/scala/de/nowchess/io/fen/FenParser.scala`
+  - class FenParser
+  - function parseFen
+  - function importGameContext
+  - function parseBoard
+- `modules/io/src/main/scala/de/nowchess/io/fen/FenParserCombinators.scala`
+  - class FenParserCombinators
+  - function parseFen
+  - function parseBoard
+  - function importGameContext
+- `modules/io/src/main/scala/de/nowchess/io/fen/FenParserFastParse.scala`
+  - class FenParserFastParse
+  - function parseFen
+  - function parseBoard
+  - function importGameContext
+- `modules/io/src/main/scala/de/nowchess/io/fen/FenParserSupport.scala` — function buildSquares
+- `modules/io/src/main/scala/de/nowchess/io/pgn/PgnExporter.scala`
+  - class PgnExporter
+  - function exportGameContext
+  - function exportGame
+- `modules/io/src/main/scala/de/nowchess/io/pgn/PgnParser.scala`
+  - class PgnParser
+  - function validatePgn
+  - function importGameContext
+  - function parsePgn
+  - function parseAlgebraicMove
+- `modules/rule/src/main/scala/de/nowchess/rules/RuleSet.scala`
+  - class RuleSet
+  - function candidateMoves
+  - function legalMoves
+  - function allLegalMoves
+  - function isCheck
+  - function isCheckmate
+  - _...4 more_
+- `modules/rule/src/main/scala/de/nowchess/rules/sets/DefaultRules.scala`
+  - class DefaultRules
+  - function loop
+  - function toMoves
+  - function loop
+- `modules/ui/src/main/scala/de/nowchess/ui/Main.scala` — class Main, function main
+- `modules/ui/src/main/scala/de/nowchess/ui/gui/ChessBoardView.scala`
+  - class ChessBoardView
+  - function updateBoard
+  - function updateUndoRedoButtons
+  - function showMessage
+  - function showPromotionDialog
+- `modules/ui/src/main/scala/de/nowchess/ui/gui/ChessGUI.scala`
+  - class ChessGUIApp
+  - class ChessGUILauncher
+  - function getEngine
+  - function launch
+- `modules/ui/src/main/scala/de/nowchess/ui/gui/GUIObserver.scala` — class GUIObserver
+- `modules/ui/src/main/scala/de/nowchess/ui/gui/PieceSprites.scala`
+  - class PieceSprites
+  - function loadPieceImage
+  - class SquareColors
+- `modules/ui/src/main/scala/de/nowchess/ui/terminal/TerminalUI.scala` — class TerminalUI, function start
+- `modules/ui/src/main/scala/de/nowchess/ui/utils/PieceUnicode.scala` — function unicode
+- `modules/ui/src/main/scala/de/nowchess/ui/utils/Renderer.scala` — class Renderer, function render

.codesight/wiki/index.md

@@ -0,0 +1,44 @@
+# NowChessSystems — Wiki
+
+_Generated 2026-04-12 — re-run `npx codesight --wiki` if the codebase has changed._
+
+Structural map compiled from source code via AST. No LLM — deterministic, 200ms.
+
+> **How to use safely:** These articles tell you WHERE things live and WHAT exists. They do not show full implementation logic. Always read the actual source files before implementing new features or making changes. Never infer how a function works from the wiki alone.
+
+## Articles
+
+- [Overview](./overview.md)
+
+## Quick Stats
+
+- Routes: **0**
+- Models: **0**
+- Components: **0**
+- Env vars: **0** required, **0** with defaults
+
+## How to Use
+
+- **New session:** read `index.md` (this file) for orientation — WHERE things are
+- **Architecture question:** read `overview.md` (~500 tokens)
+- **Domain question:** read the relevant article, then **read those source files**
+- **Database question:** read `database.md`, then read the actual schema files
+- **Before implementing anything:** read the source files listed in the article
+- **Full source context:** read `.codesight/CODESIGHT.md`
+
+## What the Wiki Does Not Cover
+
+These exist in your codebase but are **not** reflected in wiki articles:
+- Routes registered dynamically at runtime (loops, plugin factories, `app.use(dynamicRouter)`)
+- Internal routes from npm packages (e.g. Better Auth's built-in `/api/auth/*` endpoints)
+- WebSocket and SSE handlers
+- Raw SQL tables not declared through an ORM
+- Computed or virtual fields absent from schema declarations
+- TypeScript types that are not actual database columns
+- Routes marked `[inferred]` were detected via regex and may have lower precision
+- gRPC, tRPC, and GraphQL resolvers may be partially captured
+
+When in doubt, search the source. The wiki is a starting point, not a complete inventory.
+
+---
+_Last compiled: 2026-04-12 · 2 articles · [codesight](https://github.com/Houseofmvps/codesight)_

.codesight/wiki/log.md

@@ -0,0 +1,5 @@
+# Wiki Log
+
+History of `npx codesight --wiki` runs. Capped at 20 entries.
+
+## [2026-04-12 14:34:19] scan | 0 routes, 0 models, 0 components → 2 articles

.codesight/wiki/overview.md

@@ -0,0 +1,19 @@
+# NowChessSystems — Overview
+
+> **Navigation aid.** This article shows WHERE things live (routes, models, files). Read actual source files before implementing new features or making changes.
+
+**NowChessSystems** is a scala project built with raw-http.
+
+## High-Impact Files
+
+Changes to these files have the widest blast radius across the codebase:
+
+- `modules/api/src/main/scala/de/nowchess/api/game/GameContext.scala` — imported by **28** files
+- `modules/api/src/main/scala/de/nowchess/api/board/Square.scala` — imported by **21** files
+- `modules/api/src/main/scala/de/nowchess/api/board/Color.scala` — imported by **19** files
+- `modules/api/src/main/scala/de/nowchess/api/move/Move.scala` — imported by **14** files
+- `modules/api/src/main/scala/de/nowchess/api/board/Board.scala` — imported by **13** files
+- `modules/api/src/main/scala/de/nowchess/api/board/Piece.scala` — imported by **10** files
+
+---
+_Back to [index.md](./index.md) · Generated 2026-04-12_

.gitattributes

@@ -0,0 +1,41 @@
+# Normalize text files in the repo
+* text=auto eol=lf
+
+# Keep Windows command scripts in CRLF
+*.bat text eol=crlf
+*.cmd text eol=crlf
+
+# Keep Unix shell scripts in LF
+*.sh text eol=lf
+
+# Binary assets (no EOL normalization / textual diff)
+*.png binary
+*.jpg binary
+*.jpeg binary
+*.gif binary
+*.webp binary
+*.bmp binary
+*.ico binary
+
+# ML / model / numeric artifacts
+*.bin binary
+*.pt binary
+*.pth binary
+*.onnx binary
+*.h5 binary
+*.hdf5 binary
+*.pb binary
+*.tflite binary
+*.npy binary
+*.npz binary
+*.safetensors binary
+
+# Firmware / hex-like artifacts
+*.hex binary
+
+# Packaged binaries
+*.jar binary
+*.zip binary
+*.7z binary
+*.gz binary
+

.gitignore

@@ -38,6 +38,8 @@ bin/
 
 ### VS Code ###
 .vscode/
+graphify-out/
+.graphify_*.json
 
 ### Mac OS ###
 .DS_Store

.idea/gradle.xml

@@ -12,6 +12,8 @@
             <option value="$PROJECT_DIR$/modules" />
             <option value="$PROJECT_DIR$/modules/api" />
             <option value="$PROJECT_DIR$/modules/core" />
+            <option value="$PROJECT_DIR$/modules/io" />
+            <option value="$PROJECT_DIR$/modules/rule" />
             <option value="$PROJECT_DIR$/modules/ui" />
           </set>
         </option>

.idea/scala_compiler.xml

@@ -5,7 +5,7 @@
       <option name="deprecationWarnings" value="true" />
       <option name="uncheckedWarnings" value="true" />
     </profile>
-    <profile name="Gradle 2" modules="NowChessSystems.modules.core.main,NowChessSystems.modules.core.scoverage,NowChessSystems.modules.core.test,NowChessSystems.modules.ui.main,NowChessSystems.modules.ui.scoverage,NowChessSystems.modules.ui.test">
+    <profile name="Gradle 2" modules="NowChessSystems.modules.core.main,NowChessSystems.modules.core.scoverage,NowChessSystems.modules.core.test,NowChessSystems.modules.io.main,NowChessSystems.modules.io.scoverage,NowChessSystems.modules.io.test,NowChessSystems.modules.rule.main,NowChessSystems.modules.rule.scoverage,NowChessSystems.modules.rule.test,NowChessSystems.modules.ui.main,NowChessSystems.modules.ui.scoverage,NowChessSystems.modules.ui.test">
       <option name="deprecationWarnings" value="true" />
       <option name="uncheckedWarnings" value="true" />
       <parameters>

.scalafix.conf

@@ -0,0 +1,15 @@
+rules = [
+  DisableSyntax,
+  LeakingImplicitClassVal,
+  NoValInForComprehension,
+  ProcedureSyntax,
+]
+
+DisableSyntax.noVars        = true
+DisableSyntax.noThrows      = true
+DisableSyntax.noNulls       = true
+DisableSyntax.noReturns     = true
+DisableSyntax.noAsInstanceOf = true
+DisableSyntax.noIsInstanceOf = true
+DisableSyntax.noXml         = true
+DisableSyntax.noFinalize    = true

.scalafmt.conf

@@ -0,0 +1,8 @@
+version = 3.8.1
+runner.dialect = scala3
+maxColumn = 120
+indent.main = 2
+align.preset = more
+trailingCommas = always
+rewrite.rules = [SortImports, RedundantBraces]
+rewrite.scala3.convertToNewSyntax = true

AGENTS.md

@@ -0,0 +1,21 @@
+# Project Context
+
+This is a scala project using raw-http.
+
+Middleware includes: custom.
+
+High-impact files (most imported, changes here affect many other files):
+- modules/api/src/main/scala/de/nowchess/api/game/GameContext.scala (imported by 50 files)
+- modules/api/src/main/scala/de/nowchess/api/board/Square.scala (imported by 33 files)
+- modules/api/src/main/scala/de/nowchess/api/board/Color.scala (imported by 30 files)
+- modules/api/src/main/scala/de/nowchess/api/move/Move.scala (imported by 29 files)
+- modules/api/src/main/scala/de/nowchess/api/board/Board.scala (imported by 19 files)
+- modules/api/src/main/scala/de/nowchess/api/board/PieceType.scala (imported by 18 files)
+- modules/rule/src/main/scala/de/nowchess/rules/sets/DefaultRules.scala (imported by 17 files)
+- modules/api/src/main/scala/de/nowchess/api/board/Piece.scala (imported by 15 files)
+
+Required environment variables (no defaults):
+- STOCKFISH_PATH (modules/bot/python/nnue.py)
+
+Read .codesight/wiki/index.md for orientation (WHERE things live). Then read actual source files before implementing. Wiki articles are navigation aids, not implementation guides.
+Read .codesight/CODESIGHT.md for the complete AI context map including all routes, schema, components, libraries, config, middleware, and dependency graph.

ARABIAN CHESS/license.txt

@@ -1,7 +1,7 @@
-YOU CAN:
-- Edit and use the asset in any commercial  or non commercial project 
-- Use the asset in any commercial  or non commercial project
-
-YOU CAN'T:
-- Resell or distribute the asset to others
+YOU CAN:
+- Edit and use the asset in any commercial  or non commercial project 
+- Use the asset in any commercial  or non commercial project
+
+YOU CAN'T:
+- Resell or distribute the asset to others
 - Edit and resell the asset to others - - Credits required using This link: https://fatman200.itch.io/

CLAUDE.md

@@ -1,58 +1,95 @@
-# CLAUDE.md — NowChessSystems
+# Now-Chess
 
-## Stack
-Scala 3.5.x · Quarkus + quarkus-scala3 · Hibernate/Jakarta · Lanterna TUI · K8s + ArgoCD + Kargo · Frontend TBD (Vite/React/Angular/Vue)
-
-### Memory
-
-Your memory is saved under .claude/memory/MEMORY.md.
-
-## Structure
-```
-build.gradle.kts / settings.gradle.kts   # root; include(":modules:<svc>") per service
-modules/<svc>/build.gradle.kts + src/
-docs/adr/  docs/api/  docs/unresolved.md
-```
-Versions in root `extra["VERSIONS"]`; modules read via `rootProject.extra["VERSIONS"] as Map<String,String>`.
+Scala 3.5.1 · Gradle 9
 
 ## Commands
-```bash
-./gradlew build
-./gradlew :modules:<svc>:build|test
-./gradlew :modules:<svc>:test --tests "de.nowchess.<svc>.<Class>"
+
 ```
-
-## Workflow
-1. **Plan** — restate requirement, list files, flag risks. Proceed unless genuine ambiguity.
-2. **Tests first** — cover only new behaviour.
-3. **Implement** — no scope creep.
-4. **Verify** — check each requirement; confirm green build.
-
-## Scala/Quarkus Rules
-- `given`/`using` only (no `implicit`); `Option`/`Either`/`Try` (no `null`/`.get`)
-- `jakarta.*` only; reactive I/O (`Uni`/`Multi`), no blocking on event loop
-- Always exclude `org.scala-lang:scala-library` from Quarkus BOM
-- Unit tests: `extends AnyFunSuite with Matchers` — no `@Test`, no `: Unit`
-- Integration tests: `@QuarkusTest` + JUnit 5 — `@Test` methods need explicit `: Unit`
-
-## Coverage
-Line = 100% · Branch = 100% · Method = 100% · Regression tests · document exceptions
-Check: `jacoco-reporter/scoverage_coverage_gaps.py modules/{svc}/build/reports/scoverageTest/scoverage.xml`
-⚠️ Use `scoverageTest/`, NOT `scoverage/`.
-
-## Bug Fixing
-Fix failures immediately without asking. After 3 failed attempts → log in `docs/unresolved.md` + surface summary.
-
-## Agents (new service)
-Sequential: architect → scala-implementer → test-writer → gradle-builder → code-reviewer (review only, no self-fix)
-Parallel: only when services are fully independent (no shared contracts/state).
-
-## Unresolved (`docs/unresolved.md`)
-Append only, never delete:
-```
-## [YYYY-MM-DD] <title>
-**Requirement/Bug:** **Root Cause:** **Attempted Fixes:** **Next Step:**
+./clean      # Clear build dirs — only when necessary
+./compile    # Compile all modules — always run
+./test       # Run all tests
+./coverage   # Check coverage
 ```
+Try to stick to these commands for consistency.
 
-## Done Checklist
-- [ ] Plan written · files created/modified · tests green · requirements verified · unresolved logged
+## Modules
+
+| Module | Role | Depends on |
+|--------|------|-----------|
+| `api`  | Model / shared types | (none) |
+| `core` | Primary business logic | api, rule |
+| `rule` | Game rules | api |
+| `io`   | Export formats | api, core |
+| `ui`   | Entrypoint & UI | core, io |
+
+## Style
+
+- Use immutable data and pure functions.
+- Keep functions under 30 lines. If you need "and" to describe it, split it.
+- Keep cyclomatic complexity under 15.
+- Avoid comments. Let names carry intent; comment only non-obvious algorithms.
+- Scan for duplicated logic before finishing. Extract it.
+- Follow default Sonar style for Scala.
+- Use `Option` or `Either` for fallible operations; avoid exceptions for control flow.
+- Naming: types are PascalCase, functions/values are camelCase.
+
+## Code Quality
+
+- **Coverage:** 100% condition coverage required in `api`, `core`, `rule`, `io` (mandatory); `ui` exempt.
+
+### Linters
+
+- **scalafmt** — enforces formatting; run `./gradlew spotlessScalaCheck` to check and `./gradlew spotlessScalaApply` to refactor.
+- **scalafix** — enforces style and detects unused imports/code; run `./gradlew scalafix` to apply rules.
+
+## Architecture Decisions
+
+- **Immutable state as primary model:** GameContext (api) holds board, history, player state — immutable, passed through the system. Each move creates a new GameContext, enabling undo/redo without side effects.
+- **Observer pattern for UI decoupling:** GameEngine publishes move/state events; CommandInvoker queues moves; UI listens to events, not polling. GameEngine never imports UI code.
+- **RuleSet trait encapsulates rules:** Move generation, check, castling, en passant all in RuleSet impl. GameEngine calls rules as a black box; rules don't know about the rest of core.
+
+## Rules
+
+- **Tests are the spec.** Never modify tests to pass; modify requirements or code. Update tests only if requirements change.
+- Never read build folders. Ask permission if needed.
+- Keep this file up to date with any important decisions or conventions.
+
+---
+
+## Instructions for Claude Code
+
+### Two-Step Rule (mandatory)
+**Step 1 — Orient:** Use wiki articles to find WHERE things live.
+**Step 2 — Verify:** Read the actual source files listed in the wiki article BEFORE writing any code.
+
+Wiki articles are structural summaries extracted by AST. They show routes, models, and file locations.
+They do NOT show full function logic, middleware internals, or dynamic runtime behavior.
+**Never write or modify code based solely on wiki content — always read source files first.**
+
+Read in order at session start:
+1. `.codesight/wiki/index.md` — orientation map (~200 tokens)
+2. `.codesight/wiki/overview.md` — architecture overview (~500 tokens)
+3. Domain article (e.g. `.codesight/wiki/auth.md`) → check "Source Files" section → read those files
+4. `.codesight/CODESIGHT.md` — full context map for deep exploration
+
+Routes marked `[inferred]` in wiki articles were detected via regex — verify against source before trusting.
+If any source file shows ⚠ in the wiki, re-run `codesight --wiki` before proceeding.
+
+Or use the codesight MCP server for on-demand queries:
+- `codesight_get_wiki_article` — read a specific wiki article by name
+- `codesight_get_wiki_index` — get the wiki index
+- `codesight_get_summary` — quick project overview
+- `codesight_get_routes --prefix /api/users` — filtered routes
+- `codesight_get_blast_radius --file src/lib/db.ts` — impact analysis before changes
+- `codesight_get_schema --model users` — specific model details
+
+Only open specific files after consulting codesight context. This saves ~16.893 tokens per conversation.
+
+## graphify
+
+This project has a graphify knowledge graph at graphify-out/.
+
+Rules:
+- Before answering architecture or codebase questions, read graphify-out/GRAPH_REPORT.md for god nodes and community structure
+- If graphify-out/wiki/index.md exists, navigate it instead of reading raw files
+- After modifying code files in this session, run `python3 -c "from graphify.watch import _rebuild_code; from pathlib import Path; _rebuild_code(Path('.'))"` to keep the graph current

build.gradle.kts

@@ -1,6 +1,8 @@
 plugins {
     id("org.sonarqube") version "7.2.3.7755"
     id("org.scoverage") version "8.1" apply false
+    id("com.diffplug.spotless") version "8.4.0" apply false
+    id("io.github.cosmicsilence.scalafix") version "0.2.6" apply false
 }
 
 group = "de.nowchess"
@@ -32,7 +34,35 @@ val versions = mapOf(
     "SCOVERAGE"             to "2.1.1",
     "SCALAFX"               to "21.0.0-R32",
     "JAVAFX"                to "21.0.1",
-    "JUNIT_BOM"             to "5.13.4"
+    "JUNIT_BOM"             to "5.13.4",
+    "SCALA_PARSER_COMBINATORS" to "2.4.0",
+    "FASTPARSE"             to "3.0.2",
+    "JACKSON"               to "2.17.2",
+    "JACKSON_SCALA"         to "2.17.2"
 )
 extra["VERSIONS"] = versions
 
+subprojects {
+    apply(plugin = "com.diffplug.spotless")
+
+    pluginManager.withPlugin("scala") {
+        configure<com.diffplug.gradle.spotless.SpotlessExtension> {
+            scala {
+                scalafmt().configFile(rootProject.file(".scalafmt.conf"))
+            }
+        }
+
+        apply(plugin = "io.github.cosmicsilence.scalafix")
+        configure<io.github.cosmicsilence.scalafix.ScalafixExtension> {
+            configFile.set(rootProject.file(".scalafix.conf"))
+        }
+
+        // Disable SemanticDB config for the scoverage source set — it sets -sourceroot to
+        // the root project dir, which conflicts with scoverage's own -sourceroot and causes
+        // reportTestScoverage to fail with "No source root found".
+        tasks.matching { it.name in setOf("configSemanticDBScoverage", "checkScalafixScoverage", "checkScalafixTest") }.configureEach {
+            enabled = false
+        }
+    }
+}
+

docs/api-spec.yaml

@@ -0,0 +1,776 @@
+openapi: 3.0.3
+info:
+  title: NowChess API
+  description: |
+    REST API for the NowChess application. Designed to feel familiar to users
+    of the [lichess API](https://lichess.org/api).
+
+    ## Authentication
+    Most endpoints require a Bearer token:
+    ```
+    Authorization: Bearer <token>
+    ```
+    Authentication is reserved for future implementation — endpoints are currently
+    open unless noted otherwise.
+
+    ## Move notation
+    Moves are expressed in **UCI notation**: `{from}{to}[promotion]`
+    - Normal move: `e2e4`
+    - Capture: `d5e6`
+    - Promotion: `e7e8q` (q=queen, r=rook, b=bishop, n=knight)
+    - Castling: `e1g1` (kingside white), `e1c1` (queenside white)
+
+    ## Streaming
+    Endpoints that support streaming return **NDJSON** (newline-delimited JSON).
+    Request them with:
+    ```
+    Accept: application/x-ndjson
+    ```
+    Each line of the response is a complete JSON object. Empty lines are
+    keep-alive heartbeats.
+
+    ## Rate limiting
+    Requests that exceed the rate limit receive `429 Too Many Requests`.
+    Honour the `Retry-After` response header and wait before retrying.
+  version: 1.0.0
+  contact:
+    name: NowChess
+  license:
+    name: MIT
+
+servers:
+  - url: http://localhost:8080
+    description: Local development server
+
+tags:
+  - name: game
+    description: Create and manage chess games
+  - name: move
+    description: Make moves and navigate game history
+  - name: draw
+    description: Draw offers and claims
+  - name: import
+    description: Load a game from FEN or PGN
+  - name: export
+    description: Export a game as FEN or PGN
+
+paths:
+
+  # ---------------------------------------------------------------------------
+  # Game lifecycle
+  # ---------------------------------------------------------------------------
+
+  /api/board/game:
+    post:
+      operationId: createGame
+      tags: [game]
+      summary: Create a new game
+      description: |
+        Creates a new chess game starting from the initial position.
+        Returns the full game state including the generated `gameId`.
+      security:
+        - bearerAuth: []
+      requestBody:
+        required: false
+        content:
+          application/json:
+            schema:
+              $ref: '#/components/schemas/CreateGameRequest'
+      responses:
+        '201':
+          description: Game created
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/GameFull'
+        '400':
+          $ref: '#/components/responses/BadRequest'
+        '401':
+          $ref: '#/components/responses/Unauthorized'
+        '429':
+          $ref: '#/components/responses/TooManyRequests'
+
+  /api/board/game/{gameId}:
+    get:
+      operationId: getGame
+      tags: [game]
+      summary: Get game state
+      description: Returns the full current state of a game.
+      security:
+        - bearerAuth: []
+      parameters:
+        - $ref: '#/components/parameters/gameId'
+      responses:
+        '200':
+          description: Current game state
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/GameFull'
+        '404':
+          $ref: '#/components/responses/NotFound'
+        '429':
+          $ref: '#/components/responses/TooManyRequests'
+
+  /api/board/game/{gameId}/stream:
+    get:
+      operationId: streamGame
+      tags: [game]
+      summary: Stream game events
+      description: |
+        Opens a persistent NDJSON stream for a game. The first object sent is
+        a `gameFull` event containing the complete game state. Subsequent
+        objects are `gameState` events sent whenever the game changes (move
+        made, draw offered, game over, etc.).
+
+        Empty lines are heartbeats to keep the connection alive.
+
+        Connect with:
+        ```
+        Accept: application/x-ndjson
+        ```
+      security:
+        - bearerAuth: []
+      parameters:
+        - $ref: '#/components/parameters/gameId'
+      responses:
+        '200':
+          description: NDJSON event stream
+          content:
+            application/x-ndjson:
+              schema:
+                oneOf:
+                  - $ref: '#/components/schemas/GameFullEvent'
+                  - $ref: '#/components/schemas/GameStateEvent'
+                  - $ref: '#/components/schemas/ErrorEvent'
+        '404':
+          $ref: '#/components/responses/NotFound'
+        '429':
+          $ref: '#/components/responses/TooManyRequests'
+
+  /api/board/game/{gameId}/resign:
+    post:
+      operationId: resignGame
+      tags: [game]
+      summary: Resign the game
+      description: The active player resigns. The game ends immediately.
+      security:
+        - bearerAuth: []
+      parameters:
+        - $ref: '#/components/parameters/gameId'
+      responses:
+        '200':
+          description: Resignation accepted
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/OkResponse'
+        '400':
+          $ref: '#/components/responses/BadRequest'
+        '404':
+          $ref: '#/components/responses/NotFound'
+        '429':
+          $ref: '#/components/responses/TooManyRequests'
+
+  # ---------------------------------------------------------------------------
+  # Move-making
+  # ---------------------------------------------------------------------------
+
+  /api/board/game/{gameId}/move/{uci}:
+    post:
+      operationId: makeMove
+      tags: [move]
+      summary: Make a move
+      description: |
+        Submit a move in UCI notation. The move must be legal for the side
+        currently to move.
+
+        For promotion moves include the target piece as the fifth character:
+        `e7e8q`, `a2a1r`, etc.
+
+        If the move results in a pawn reaching the back rank and no promotion
+        character is supplied, the game enters `promotionPending` status and
+        the move is not yet applied — resubmit with the promotion character.
+      security:
+        - bearerAuth: []
+      parameters:
+        - $ref: '#/components/parameters/gameId'
+        - name: uci
+          in: path
+          required: true
+          description: Move in UCI notation (e.g. `e2e4`, `e7e8q`)
+          schema:
+            type: string
+            pattern: '^[a-h][1-8][a-h][1-8][qrbn]?$'
+            example: e2e4
+      responses:
+        '200':
+          description: Move applied — returns updated game state
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/GameState'
+        '400':
+          $ref: '#/components/responses/BadRequest'
+        '404':
+          $ref: '#/components/responses/NotFound'
+        '429':
+          $ref: '#/components/responses/TooManyRequests'
+
+  /api/board/game/{gameId}/moves:
+    get:
+      operationId: getLegalMoves
+      tags: [move]
+      summary: Get legal moves
+      description: |
+        Returns all legal moves for the side currently to move.
+        Optionally filter to moves originating from a single square.
+      security:
+        - bearerAuth: []
+      parameters:
+        - $ref: '#/components/parameters/gameId'
+        - name: square
+          in: query
+          required: false
+          description: Filter to moves from this square (e.g. `e2`)
+          schema:
+            type: string
+            pattern: '^[a-h][1-8]$'
+            example: e2
+      responses:
+        '200':
+          description: List of legal moves
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/LegalMovesResponse'
+        '404':
+          $ref: '#/components/responses/NotFound'
+        '429':
+          $ref: '#/components/responses/TooManyRequests'
+
+  /api/board/game/{gameId}/undo:
+    post:
+      operationId: undoMove
+      tags: [move]
+      summary: Undo the last move
+      description: Reverts the most recent move. Returns the updated game state.
+      security:
+        - bearerAuth: []
+      parameters:
+        - $ref: '#/components/parameters/gameId'
+      responses:
+        '200':
+          description: Move undone
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/GameState'
+        '400':
+          description: No moves to undo
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/ApiError'
+        '404':
+          $ref: '#/components/responses/NotFound'
+        '429':
+          $ref: '#/components/responses/TooManyRequests'
+
+  /api/board/game/{gameId}/redo:
+    post:
+      operationId: redoMove
+      tags: [move]
+      summary: Redo a previously undone move
+      description: Re-applies the next move in the undo stack. Returns the updated game state.
+      security:
+        - bearerAuth: []
+      parameters:
+        - $ref: '#/components/parameters/gameId'
+      responses:
+        '200':
+          description: Move redone
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/GameState'
+        '400':
+          description: No moves to redo
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/ApiError'
+        '404':
+          $ref: '#/components/responses/NotFound'
+        '429':
+          $ref: '#/components/responses/TooManyRequests'
+
+  # ---------------------------------------------------------------------------
+  # Draw handling
+  # ---------------------------------------------------------------------------
+
+  /api/board/game/{gameId}/draw/{action}:
+    post:
+      operationId: drawAction
+      tags: [draw]
+      summary: Offer, accept, decline, or claim a draw
+      description: |
+        Perform a draw-related action:
+
+        | Action    | Description |
+        |-----------|-------------|
+        | `offer`   | Offer a draw to the opponent |
+        | `accept`  | Accept the opponent's draw offer |
+        | `decline` | Decline the opponent's draw offer |
+        | `claim`   | Claim a draw under the fifty-move rule (only valid when `status` is `fiftyMoveAvailable`) |
+      security:
+        - bearerAuth: []
+      parameters:
+        - $ref: '#/components/parameters/gameId'
+        - name: action
+          in: path
+          required: true
+          schema:
+            type: string
+            enum: [offer, accept, decline, claim]
+      responses:
+        '200':
+          description: Action accepted
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/OkResponse'
+        '400':
+          $ref: '#/components/responses/BadRequest'
+        '404':
+          $ref: '#/components/responses/NotFound'
+        '429':
+          $ref: '#/components/responses/TooManyRequests'
+
+  # ---------------------------------------------------------------------------
+  # Import
+  # ---------------------------------------------------------------------------
+
+  /api/board/game/import/fen:
+    post:
+      operationId: importFen
+      tags: [import]
+      summary: Load a position from FEN
+      description: |
+        Creates a new game from a FEN string. The game starts at the position
+        described by the FEN; move history prior to that position is not
+        available.
+      security:
+        - bearerAuth: []
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              $ref: '#/components/schemas/ImportFenRequest'
+      responses:
+        '201':
+          description: Game created from FEN
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/GameFull'
+        '400':
+          $ref: '#/components/responses/BadRequest'
+        '429':
+          $ref: '#/components/responses/TooManyRequests'
+
+  /api/board/game/import/pgn:
+    post:
+      operationId: importPgn
+      tags: [import]
+      summary: Load a game from PGN
+      description: |
+        Creates a new game by replaying all moves in a PGN string. The game
+        starts at the position after the final move in the PGN; undo is
+        available for every replayed move.
+      security:
+        - bearerAuth: []
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              $ref: '#/components/schemas/ImportPgnRequest'
+      responses:
+        '201':
+          description: Game created from PGN
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/GameFull'
+        '400':
+          $ref: '#/components/responses/BadRequest'
+        '429':
+          $ref: '#/components/responses/TooManyRequests'
+
+  # ---------------------------------------------------------------------------
+  # Export
+  # ---------------------------------------------------------------------------
+
+  /api/board/game/{gameId}/export/fen:
+    get:
+      operationId: exportFen
+      tags: [export]
+      summary: Export current position as FEN
+      description: Returns the FEN string representing the current board position.
+      security:
+        - bearerAuth: []
+      parameters:
+        - $ref: '#/components/parameters/gameId'
+      responses:
+        '200':
+          description: FEN string
+          content:
+            text/plain:
+              schema:
+                type: string
+                example: rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq e3 0 1
+        '404':
+          $ref: '#/components/responses/NotFound'
+        '429':
+          $ref: '#/components/responses/TooManyRequests'
+
+  /api/board/game/{gameId}/export/pgn:
+    get:
+      operationId: exportPgn
+      tags: [export]
+      summary: Export game as PGN
+      description: Returns the full PGN for the game including headers and move text.
+      security:
+        - bearerAuth: []
+      parameters:
+        - $ref: '#/components/parameters/gameId'
+      responses:
+        '200':
+          description: PGN text
+          content:
+            application/x-chess-pgn:
+              schema:
+                type: string
+                example: |
+                  [Event "NowChess game"]
+                  [White "Player1"]
+                  [Black "Player2"]
+                  [Result "*"]
+
+                  1. e4 e5 2. Nf3 *
+        '404':
+          $ref: '#/components/responses/NotFound'
+        '429':
+          $ref: '#/components/responses/TooManyRequests'
+
+# =============================================================================
+# Components
+# =============================================================================
+
+components:
+
+  securitySchemes:
+    bearerAuth:
+      type: http
+      scheme: bearer
+      description: 'Personal access token — `Authorization: Bearer <token>`'
+
+  parameters:
+    gameId:
+      name: gameId
+      in: path
+      required: true
+      description: 8-character alphanumeric game ID (e.g. `Qa7FJNk2`)
+      schema:
+        type: string
+        pattern: '^[A-Za-z0-9]{8}$'
+        example: Qa7FJNk2
+
+  responses:
+    BadRequest:
+      description: Invalid input
+      content:
+        application/json:
+          schema:
+            $ref: '#/components/schemas/ApiError'
+    Unauthorized:
+      description: Missing or invalid authentication token
+      content:
+        application/json:
+          schema:
+            $ref: '#/components/schemas/ApiError'
+    NotFound:
+      description: Game not found
+      content:
+        application/json:
+          schema:
+            $ref: '#/components/schemas/ApiError'
+    TooManyRequests:
+      description: Rate limit exceeded — see `Retry-After` header
+      headers:
+        Retry-After:
+          description: Seconds to wait before retrying
+          schema:
+            type: integer
+      content:
+        application/json:
+          schema:
+            $ref: '#/components/schemas/ApiError'
+
+  schemas:
+
+    # -------------------------------------------------------------------------
+    # Requests
+    # -------------------------------------------------------------------------
+
+    CreateGameRequest:
+      type: object
+      description: Parameters for creating a new game. All fields are optional.
+      properties:
+        white:
+          $ref: '#/components/schemas/PlayerInfo'
+        black:
+          $ref: '#/components/schemas/PlayerInfo'
+
+    ImportFenRequest:
+      type: object
+      required: [fen]
+      properties:
+        fen:
+          type: string
+          description: Complete FEN string (6 fields)
+          example: rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1
+        white:
+          $ref: '#/components/schemas/PlayerInfo'
+        black:
+          $ref: '#/components/schemas/PlayerInfo'
+
+    ImportPgnRequest:
+      type: object
+      required: [pgn]
+      properties:
+        pgn:
+          type: string
+          description: PGN text (headers and move list)
+          example: "1. e4 e5 2. Nf3 Nc6 *"
+
+    # -------------------------------------------------------------------------
+    # Game state
+    # -------------------------------------------------------------------------
+
+    GameFull:
+      type: object
+      description: Complete game information including players and current state.
+      required: [gameId, white, black, state]
+      properties:
+        gameId:
+          type: string
+          description: Unique 8-character game identifier
+          example: Qa7FJNk2
+        white:
+          $ref: '#/components/schemas/PlayerInfo'
+        black:
+          $ref: '#/components/schemas/PlayerInfo'
+        state:
+          $ref: '#/components/schemas/GameState'
+
+    GameState:
+      type: object
+      description: |
+        The current game state. Included in `GameFull` and returned by move
+        endpoints and stream events.
+      required: [fen, pgn, turn, status, moves, undoAvailable, redoAvailable]
+      properties:
+        fen:
+          type: string
+          description: FEN string for the current position
+          example: rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq e3 0 1
+        pgn:
+          type: string
+          description: PGN move text for the full game so far
+          example: "1. e4"
+        turn:
+          type: string
+          enum: [white, black]
+          description: The side to move
+        status:
+          $ref: '#/components/schemas/GameStatus'
+        winner:
+          type: string
+          enum: [white, black]
+          description: Set when `status` is `checkmate` or `resign`
+          nullable: true
+        moves:
+          type: array
+          description: All moves played so far, in UCI notation
+          items:
+            type: string
+          example: [e2e4, e7e5, g1f3]
+        undoAvailable:
+          type: boolean
+          description: Whether `POST /undo` is currently valid
+        redoAvailable:
+          type: boolean
+          description: Whether `POST /redo` is currently valid
+
+    GameStatus:
+      type: string
+      description: |
+        Current game status:
+
+        | Value | Meaning |
+        |-------|---------|
+        | `started` | Game in progress, no special condition |
+        | `check` | Side to move is in check |
+        | `checkmate` | Side to move is checkmated — game over |
+        | `stalemate` | Side to move has no legal moves, not in check — game over (draw) |
+        | `resign` | A player resigned — game over |
+        | `draw` | Draw agreed or claimed — game over |
+        | `drawOffered` | Waiting for the opponent to accept or decline a draw offer |
+        | `fiftyMoveAvailable` | Fifty-move rule threshold reached; active player may claim draw |
+        | `promotionPending` | A pawn reached the back rank; awaiting promotion piece selection |
+        | `insufficientMaterial` | Neither side has enough pieces to deliver checkmate — game over (draw) |
+      enum:
+        - started
+        - check
+        - checkmate
+        - stalemate
+        - resign
+        - draw
+        - drawOffered
+        - fiftyMoveAvailable
+        - promotionPending
+        - insufficientMaterial
+
+    # -------------------------------------------------------------------------
+    # Moves
+    # -------------------------------------------------------------------------
+
+    LegalMovesResponse:
+      type: object
+      required: [moves]
+      properties:
+        moves:
+          type: array
+          items:
+            $ref: '#/components/schemas/LegalMove'
+
+    LegalMove:
+      type: object
+      required: [from, to, uci, moveType]
+      properties:
+        from:
+          type: string
+          description: Origin square in algebraic notation
+          example: e2
+        to:
+          type: string
+          description: Destination square in algebraic notation
+          example: e4
+        uci:
+          type: string
+          description: Full move in UCI notation
+          example: e2e4
+        moveType:
+          $ref: '#/components/schemas/MoveType'
+        promotion:
+          type: string
+          enum: [queen, rook, bishop, knight]
+          description: Target piece for promotion moves
+          nullable: true
+
+    MoveType:
+      type: string
+      description: Classification of the move
+      enum:
+        - normal
+        - capture
+        - castleKingside
+        - castleQueenside
+        - enPassant
+        - promotion
+
+    # -------------------------------------------------------------------------
+    # Streaming events
+    # -------------------------------------------------------------------------
+
+    GameFullEvent:
+      type: object
+      description: |
+        First event on a game stream. Contains the complete game snapshot.
+      required: [type, game]
+      properties:
+        type:
+          type: string
+          enum: [gameFull]
+        game:
+          $ref: '#/components/schemas/GameFull'
+
+    GameStateEvent:
+      type: object
+      description: |
+        Emitted on a game stream whenever the game state changes (move played,
+        draw offered, game over, etc.).
+      required: [type, state]
+      properties:
+        type:
+          type: string
+          enum: [gameState]
+        state:
+          $ref: '#/components/schemas/GameState'
+
+    ErrorEvent:
+      type: object
+      description: Emitted on a game stream when an error occurs.
+      required: [type, error]
+      properties:
+        type:
+          type: string
+          enum: [error]
+        error:
+          $ref: '#/components/schemas/ApiError'
+
+    # -------------------------------------------------------------------------
+    # Shared types
+    # -------------------------------------------------------------------------
+
+    PlayerInfo:
+      type: object
+      required: [id, displayName]
+      properties:
+        id:
+          type: string
+          description: Unique player identifier
+          example: player1
+        displayName:
+          type: string
+          description: Human-readable display name
+          example: Alice
+
+    OkResponse:
+      type: object
+      required: [ok]
+      properties:
+        ok:
+          type: boolean
+          enum: [true]
+
+    ApiError:
+      type: object
+      required: [code, message]
+      properties:
+        code:
+          type: string
+          description: Machine-readable error code
+          example: INVALID_MOVE
+        message:
+          type: string
+          description: Human-readable error description
+          example: e2e5 is not a legal move
+        field:
+          type: string
+          description: Request field that caused the error, if applicable
+          example: uci
+          nullable: true

docs/unresolved.md

@@ -1,20 +0,0 @@
-## [2026-03-31] Unreachable code blocking 100% statement coverage
-
-**Requirement/Bug:** Reach 100% statement coverage in core module.
-
-**Root Cause:** 4 remaining uncovered statements (99.6% coverage) are unreachable code:
-1. **PgnParser.scala:160** (`case _ => None` in extractPromotion) - Regex `=([QRBN])` only matches those 4 characters; fallback case can never execute
-2. **GameHistory.scala:29** (`addMove$default$4` compiler-generated method) - Method overload 3 without defaults shadows the 4-param version, making promotionPiece default accessor unreachable
-3. **GameEngine.scala:201-202** (`case _` in completePromotion) - GameController.completePromotion always returns one of 4 expected MoveResult types; catch-all is defensive code
-
-**Attempted Fixes:**
-1. Added comprehensive PGN parsing tests (all 4 promotion types) - PgnParser improved from 95.8% to 99.4%
-2. Added GameHistory tests using named parameters - hit `addMove$default$3` (castleSide) but not `$default$4` (promotionPiece)
-3. Named parameter approach: `addMove(from=..., to=..., promotionPiece=...)` triggers 4-param with castleSide default ✓
-4. Positional approach: `addMove(f, t, None, None)` requires all 4 args (explicit, no defaults used) - doesn't hit $default$4
-5. Root issue: Scala's overload resolution prefers more-specific non-default overloads (2-param, 3-param) over the 4-param with defaults
-
-**Recommendation:** 99.6% (1029/1033) is maximum achievable without refactoring method overloads. Unreachable code design patterns:
-- **Pattern 1 (unreachable regex fallback):** Defensive pattern match against exhaustive regex
-- **Pattern 2 (overshadowed defaults):** Method overloads shadow default parameters in parent signature
-- **Pattern 3 (defensive catch-all):** Error handling for impossible external API returns

jacoco-reporter/test_counter.py

@@ -0,0 +1,12 @@
+import glob,re
+mods=['api','core','io','rule','ui']
+tot=0
+for m in mods:
+ s=0
+ for f in glob.glob(f'modules/{m}/build/test-results/test/TEST-*.xml'):
+  txt=open(f,encoding='utf-8').read(300)
+  m2=re.search(r'tests="(\d+)"',txt)
+  if m2:s+=int(m2.group(1))
+ print(f'{m}: {s}')
+ tot+=s
+print('overall:',tot)

modules/api/CHANGELOG.md

@@ -11,3 +11,26 @@
 ### Features
 
 * NCS-21 Write Scripts to automate certain tasks ([#15](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/15)) ([8051871](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/80518719d536a087d339fe02530825dc07f8b388))
+##  (2026-04-03)
+
+### Features
+
+* NCS-21 Write Scripts to automate certain tasks ([#15](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/15)) ([8051871](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/80518719d536a087d339fe02530825dc07f8b388))
+##  (2026-04-07)
+
+### Features
+
+* NCS-21 Write Scripts to automate certain tasks ([#15](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/15)) ([8051871](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/80518719d536a087d339fe02530825dc07f8b388))
+##  (2026-04-12)
+
+### Features
+
+* NCS-21 Write Scripts to automate certain tasks ([#15](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/15)) ([8051871](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/80518719d536a087d339fe02530825dc07f8b388))
+* NCS-25 Add linters to keep quality up ([#27](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/27)) ([fd4e67d](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/fd4e67d4f782a7e955822d90cb909d0a81676fb2))
+##  (2026-04-14)
+
+### Features
+
+* NCS-14 implemented insufficient moves rule ([#30](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/30)) ([b0399a4](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/b0399a4e489950083066c9538df9a84dcc7a4613))
+* NCS-21 Write Scripts to automate certain tasks ([#15](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/15)) ([8051871](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/80518719d536a087d339fe02530825dc07f8b388))
+* NCS-25 Add linters to keep quality up ([#27](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/27)) ([fd4e67d](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/fd4e67d4f782a7e955822d90cb909d0a81676fb2))

modules/api/src/main/scala/de/nowchess/api/board/Board.scala

@@ -7,19 +7,28 @@ object Board:
   def apply(pieces: Map[Square, Piece]): Board = pieces
 
   extension (b: Board)
-    def pieceAt(sq: Square): Option[Piece] = b.get(sq)
+    def pieceAt(sq: Square): Option[Piece]       = b.get(sq)
     def updated(sq: Square, piece: Piece): Board = b.updated(sq, piece)
-    def removed(sq: Square): Board = b.removed(sq)
+    def removed(sq: Square): Board               = b.removed(sq)
     def withMove(from: Square, to: Square): (Board, Option[Piece]) =
-      val captured = b.get(to)
+      val captured     = b.get(to)
       val updatedBoard = b.removed(from).updated(to, b(from))
       (updatedBoard, captured)
+    def applyMove(move: de.nowchess.api.move.Move): Board =
+      val (updatedBoard, _) = b.withMove(move.from, move.to)
+      updatedBoard
     def pieces: Map[Square, Piece] = b
 
   val initial: Board =
     val backRank: Vector[PieceType] = Vector(
-      PieceType.Rook, PieceType.Knight, PieceType.Bishop, PieceType.Queen,
-      PieceType.King, PieceType.Bishop, PieceType.Knight, PieceType.Rook
+      PieceType.Rook,
+      PieceType.Knight,
+      PieceType.Bishop,
+      PieceType.Queen,
+      PieceType.King,
+      PieceType.Bishop,
+      PieceType.Knight,
+      PieceType.Rook,
     )
     val entries = for
       fileIdx <- 0 until 8
@@ -27,7 +36,7 @@ object Board:
         (Color.White, Rank.R1, backRank(fileIdx)),
         (Color.White, Rank.R2, PieceType.Pawn),
         (Color.Black, Rank.R8, backRank(fileIdx)),
-        (Color.Black, Rank.R7, PieceType.Pawn)
+        (Color.Black, Rank.R7, PieceType.Pawn),
       )
     yield Square(File.values(fileIdx), rank) -> Piece(color, pieceType)
     Board(entries.toMap)

modules/api/src/main/scala/de/nowchess/api/board/CastlingRights.scala

@@ -0,0 +1,68 @@
+package de.nowchess.api.board
+
+/** Unified castling rights tracker for all four sides. Tracks whether castling is still available for each side and
+  * direction.
+  *
+  * @param whiteKingSide
+  *   White's king-side castling (0-0) still legally available
+  * @param whiteQueenSide
+  *   White's queen-side castling (0-0-0) still legally available
+  * @param blackKingSide
+  *   Black's king-side castling (0-0) still legally available
+  * @param blackQueenSide
+  *   Black's queen-side castling (0-0-0) still legally available
+  */
+final case class CastlingRights(
+    whiteKingSide: Boolean,
+    whiteQueenSide: Boolean,
+    blackKingSide: Boolean,
+    blackQueenSide: Boolean,
+):
+  /** Check if either side has any castling rights remaining.
+    */
+  def hasAnyRights: Boolean =
+    whiteKingSide || whiteQueenSide || blackKingSide || blackQueenSide
+
+  /** Check if a specific color has any castling rights remaining.
+    */
+  def hasRights(color: Color): Boolean = color match
+    case Color.White => whiteKingSide || whiteQueenSide
+    case Color.Black => blackKingSide || blackQueenSide
+
+  /** Revoke all castling rights for a specific color.
+    */
+  def revokeColor(color: Color): CastlingRights = color match
+    case Color.White => copy(whiteKingSide = false, whiteQueenSide = false)
+    case Color.Black => copy(blackKingSide = false, blackQueenSide = false)
+
+  /** Revoke a specific castling right.
+    */
+  def revokeKingSide(color: Color): CastlingRights = color match
+    case Color.White => copy(whiteKingSide = false)
+    case Color.Black => copy(blackKingSide = false)
+
+  /** Revoke a specific castling right.
+    */
+  def revokeQueenSide(color: Color): CastlingRights = color match
+    case Color.White => copy(whiteQueenSide = false)
+    case Color.Black => copy(blackQueenSide = false)
+
+object CastlingRights:
+  /** No castling rights for any side. */
+  val None: CastlingRights = CastlingRights(
+    whiteKingSide = false,
+    whiteQueenSide = false,
+    blackKingSide = false,
+    blackQueenSide = false,
+  )
+
+  /** All castling rights available. */
+  val All: CastlingRights = CastlingRights(
+    whiteKingSide = true,
+    whiteQueenSide = true,
+    blackKingSide = true,
+    blackQueenSide = true,
+  )
+
+  /** Standard starting position castling rights (both sides can castle both ways). */
+  val Initial: CastlingRights = All

modules/api/src/main/scala/de/nowchess/api/board/Piece.scala

@@ -5,16 +5,16 @@ final case class Piece(color: Color, pieceType: PieceType)
 
 object Piece:
   // Convenience constructors
-  val WhitePawn:   Piece = Piece(Color.White, PieceType.Pawn)
+  val WhitePawn: Piece   = Piece(Color.White, PieceType.Pawn)
   val WhiteKnight: Piece = Piece(Color.White, PieceType.Knight)
   val WhiteBishop: Piece = Piece(Color.White, PieceType.Bishop)
-  val WhiteRook:   Piece = Piece(Color.White, PieceType.Rook)
-  val WhiteQueen:  Piece = Piece(Color.White, PieceType.Queen)
-  val WhiteKing:   Piece = Piece(Color.White, PieceType.King)
+  val WhiteRook: Piece   = Piece(Color.White, PieceType.Rook)
+  val WhiteQueen: Piece  = Piece(Color.White, PieceType.Queen)
+  val WhiteKing: Piece   = Piece(Color.White, PieceType.King)
 
-  val BlackPawn:   Piece = Piece(Color.Black, PieceType.Pawn)
+  val BlackPawn: Piece   = Piece(Color.Black, PieceType.Pawn)
   val BlackKnight: Piece = Piece(Color.Black, PieceType.Knight)
   val BlackBishop: Piece = Piece(Color.Black, PieceType.Bishop)
-  val BlackRook:   Piece = Piece(Color.Black, PieceType.Rook)
-  val BlackQueen:  Piece = Piece(Color.Black, PieceType.Queen)
-  val BlackKing:   Piece = Piece(Color.Black, PieceType.King)
+  val BlackRook: Piece   = Piece(Color.Black, PieceType.Rook)
+  val BlackQueen: Piece  = Piece(Color.Black, PieceType.Queen)
+  val BlackKing: Piece   = Piece(Color.Black, PieceType.King)

modules/api/src/main/scala/de/nowchess/api/board/Square.scala

@@ -1,41 +1,53 @@
 package de.nowchess.api.board
 
-/**
- * A file (column) on the chess board, a–h.
- * Ordinal values 0–7 correspond to a–h.
- */
+/** A file (column) on the chess board, a–h. Ordinal values 0–7 correspond to a–h.
+  */
 enum File:
   case A, B, C, D, E, F, G, H
 
-/**
- * A rank (row) on the chess board, 1–8.
- * Ordinal values 0–7 correspond to ranks 1–8.
- */
+/** A rank (row) on the chess board, 1–8. Ordinal values 0–7 correspond to ranks 1–8.
+  */
 enum Rank:
   case R1, R2, R3, R4, R5, R6, R7, R8
 
-/**
- * A unique square on the board, identified by its file and rank.
- *
- * @param file the column, a–h
- * @param rank the row, 1–8
- */
+/** A unique square on the board, identified by its file and rank.
+  *
+  * @param file
+  *   the column, a–h
+  * @param rank
+  *   the row, 1–8
+  */
 final case class Square(file: File, rank: Rank):
   /** Algebraic notation string, e.g. "e4". */
   override def toString: String =
     s"${file.toString.toLowerCase}${rank.ordinal + 1}"
 
 object Square:
-  /** Parse a square from algebraic notation (e.g. "e4").
-   *  Returns None if the input is not a valid square name. */
+  /** Parse a square from algebraic notation (e.g. "e4"). Returns None if the input is not a valid square name.
+    */
   def fromAlgebraic(s: String): Option[Square] =
     if s.length != 2 then None
     else
       val fileChar = s.charAt(0)
       val rankChar = s.charAt(1)
-      val fileOpt = File.values.find(_.toString.equalsIgnoreCase(fileChar.toString))
+      val fileOpt  = File.values.find(_.toString.equalsIgnoreCase(fileChar.toString))
       val rankOpt =
-        rankChar.toString.toIntOption.flatMap(n =>
-          if n >= 1 && n <= 8 then Some(Rank.values(n - 1)) else None
-        )
+        rankChar.toString.toIntOption.flatMap(n => if n >= 1 && n <= 8 then Some(Rank.values(n - 1)) else None)
       for f <- fileOpt; r <- rankOpt yield Square(f, r)
+
+  val all: IndexedSeq[Square] =
+    for
+      r <- Rank.values.toIndexedSeq
+      f <- File.values.toIndexedSeq
+    yield Square(f, r)
+
+  /** Compute a target square by offsetting file and rank. Returns None if the resulting square is outside the board
+    * (0-7 range).
+    */
+  extension (sq: Square)
+    def offset(fileDelta: Int, rankDelta: Int): Option[Square] =
+      val newFileOrd = sq.file.ordinal + fileDelta
+      val newRankOrd = sq.rank.ordinal + rankDelta
+      if newFileOrd >= 0 && newFileOrd < 8 && newRankOrd >= 0 && newRankOrd < 8 then
+        Some(Square(File.values(newFileOrd), Rank.values(newRankOrd)))
+      else None

modules/api/src/main/scala/de/nowchess/api/game/DrawReason.scala

@@ -0,0 +1,9 @@
+package de.nowchess.api.game
+
+/** Reason why a game ended in a draw. */
+enum DrawReason:
+  case Stalemate
+  case InsufficientMaterial
+  case FiftyMoveRule
+  case ThreefoldRepetition
+  case Agreement

modules/api/src/main/scala/de/nowchess/api/game/GameContext.scala

@@ -0,0 +1,48 @@
+package de.nowchess.api.game
+
+import de.nowchess.api.board.{Board, CastlingRights, Color, Square}
+import de.nowchess.api.move.Move
+
+/** Immutable bundle of complete game state. All state changes produce new GameContext instances.
+  */
+case class GameContext(
+    board: Board,
+    turn: Color,
+    castlingRights: CastlingRights,
+    enPassantSquare: Option[Square],
+    halfMoveClock: Int,
+    moves: List[Move],
+    result: Option[GameResult] = None,
+    initialBoard: Board = Board.initial,
+):
+  /** Create new context with updated board. */
+  def withBoard(newBoard: Board): GameContext = copy(board = newBoard)
+
+  /** Create new context with updated turn. */
+  def withTurn(newTurn: Color): GameContext = copy(turn = newTurn)
+
+  /** Create new context with updated castling rights. */
+  def withCastlingRights(newRights: CastlingRights): GameContext = copy(castlingRights = newRights)
+
+  /** Create new context with updated en passant square. */
+  def withEnPassantSquare(newSq: Option[Square]): GameContext = copy(enPassantSquare = newSq)
+
+  /** Create new context with updated half-move clock. */
+  def withHalfMoveClock(newClock: Int): GameContext = copy(halfMoveClock = newClock)
+
+  /** Create new context with move appended to history. */
+  def withMove(move: Move): GameContext = copy(moves = moves :+ move)
+
+  /** Create new context with updated result. */
+  def withResult(newResult: Option[GameResult]): GameContext = copy(result = newResult)
+
+object GameContext:
+  /** Initial position: white to move, all castling rights, no en passant. */
+  def initial: GameContext = GameContext(
+    board = Board.initial,
+    turn = Color.White,
+    castlingRights = CastlingRights.Initial,
+    enPassantSquare = None,
+    halfMoveClock = 0,
+    moves = List.empty,
+  )

modules/api/src/main/scala/de/nowchess/api/game/GameResult.scala

@@ -0,0 +1,8 @@
+package de.nowchess.api.game
+
+import de.nowchess.api.board.Color
+
+/** Outcome of a finished game. */
+enum GameResult:
+  case Win(color: Color)
+  case Draw(reason: DrawReason)

modules/api/src/main/scala/de/nowchess/api/game/GameState.scala

@@ -1,67 +0,0 @@
-package de.nowchess.api.game
-
-import de.nowchess.api.board.{Color, Square}
-
-/**
- * Castling availability flags for one side.
- *
- * @param kingSide  king-side castling still legally available
- * @param queenSide queen-side castling still legally available
- */
-final case class CastlingRights(kingSide: Boolean, queenSide: Boolean)
-
-object CastlingRights:
-  val None: CastlingRights = CastlingRights(kingSide = false, queenSide = false)
-  val Both: CastlingRights = CastlingRights(kingSide = true, queenSide = true)
-
-/** Outcome of a finished game. */
-enum GameResult:
-  case WhiteWins
-  case BlackWins
-  case Draw
-
-/** Lifecycle state of a game. */
-enum GameStatus:
-  case NotStarted
-  case InProgress
-  case Finished(result: GameResult)
-
-/**
- * A FEN-compatible snapshot of board and game state.
- *
- * The board is represented as a FEN piece-placement string (rank 8 to rank 1,
- * separated by '/').  All other fields mirror standard FEN fields.
- *
- * @param piecePlacement  FEN piece-placement field, e.g.
- *                        "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR"
- * @param activeColor     side to move
- * @param castlingWhite   castling rights for White
- * @param castlingBlack   castling rights for Black
- * @param enPassantTarget square behind the double-pushed pawn, if any
- * @param halfMoveClock   plies since last capture or pawn advance (50-move rule)
- * @param fullMoveNumber  increments after Black's move, starts at 1
- * @param status          current lifecycle status of the game
- */
-final case class GameState(
-  piecePlacement: String,
-  activeColor: Color,
-  castlingWhite: CastlingRights,
-  castlingBlack: CastlingRights,
-  enPassantTarget: Option[Square],
-  halfMoveClock: Int,
-  fullMoveNumber: Int,
-  status: GameStatus
-)
-
-object GameState:
-  /** Standard starting position. */
-  val initial: GameState = GameState(
-    piecePlacement  = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR",
-    activeColor     = Color.White,
-    castlingWhite   = CastlingRights.Both,
-    castlingBlack   = CastlingRights.Both,
-    enPassantTarget = None,
-    halfMoveClock   = 0,
-    fullMoveNumber  = 1,
-    status          = GameStatus.InProgress
-  )

modules/api/src/main/scala/de/nowchess/api/move/Move.scala

@@ -9,25 +9,31 @@ enum PromotionPiece:
 /** Classifies special move semantics beyond a plain quiet move or capture. */
 enum MoveType:
   /** A normal move or capture with no special rule. */
-  case Normal
+  case Normal(isCapture: Boolean = false)
+
   /** Kingside castling (O-O). */
   case CastleKingside
+
   /** Queenside castling (O-O-O). */
   case CastleQueenside
+
   /** En-passant pawn capture. */
   case EnPassant
+
   /** Pawn promotion; carries the chosen promotion piece. */
   case Promotion(piece: PromotionPiece)
 
-/**
- * A half-move (ply) in a chess game.
- *
- * @param from     origin square
- * @param to       destination square
- * @param moveType special semantics; defaults to Normal
- */
+/** A half-move (ply) in a chess game.
+  *
+  * @param from
+  *   origin square
+  * @param to
+  *   destination square
+  * @param moveType
+  *   special semantics; defaults to Normal
+  */
 final case class Move(
-  from: Square,
-  to: Square,
-  moveType: MoveType = MoveType.Normal
+    from: Square,
+    to: Square,
+    moveType: MoveType = MoveType.Normal(),
 )

modules/api/src/main/scala/de/nowchess/api/player/PlayerInfo.scala

@@ -1,27 +1,26 @@
 package de.nowchess.api.player
 
-/**
- * An opaque player identifier.
- *
- * Wraps a plain String so that IDs are not accidentally interchanged with
- * other String values at compile time.
- */
+/** An opaque player identifier.
+  *
+  * Wraps a plain String so that IDs are not accidentally interchanged with other String values at compile time.
+  */
 opaque type PlayerId = String
 
 object PlayerId:
-  def apply(value: String): PlayerId = value
+  def apply(value: String): PlayerId         = value
   extension (id: PlayerId) def value: String = id
 
-/**
- * The minimal cross-service identity stub for a player.
- *
- * Full profile data (email, rating history, etc.) lives in the user-management
- * service.  Only what every service needs is held here.
- *
- * @param id          unique identifier
- * @param displayName human-readable name shown in the UI
- */
+/** The minimal cross-service identity stub for a player.
+  *
+  * Full profile data (email, rating history, etc.) lives in the user-management service. Only what every service needs
+  * is held here.
+  *
+  * @param id
+  *   unique identifier
+  * @param displayName
+  *   human-readable name shown in the UI
+  */
 final case class PlayerInfo(
-  id: PlayerId,
-  displayName: String
+    id: PlayerId,
+    displayName: String,
 )

modules/api/src/main/scala/de/nowchess/api/response/ApiResponse.scala

@@ -1,13 +1,12 @@
 package de.nowchess.api.response
 
-/**
- * A standardised envelope for every API response.
- *
- * Success and failure are modelled as subtypes so that callers
- * can pattern-match exhaustively.
- *
- * @tparam A the payload type for a successful response
- */
+/** A standardised envelope for every API response.
+  *
+  * Success and failure are modelled as subtypes so that callers can pattern-match exhaustively.
+  *
+  * @tparam A
+  *   the payload type for a successful response
+  */
 sealed trait ApiResponse[+A]
 
 object ApiResponse:
@@ -20,43 +19,49 @@ object ApiResponse:
   /** Convenience constructor for a single-error failure. */
   def error(err: ApiError): Failure = Failure(List(err))
 
-/**
- * A structured error descriptor.
- *
- * @param code    machine-readable error code (e.g. "INVALID_MOVE", "NOT_FOUND")
- * @param message human-readable explanation
- * @param field   optional field name when the error relates to a specific input
- */
+/** A structured error descriptor.
+  *
+  * @param code
+  *   machine-readable error code (e.g. "INVALID_MOVE", "NOT_FOUND")
+  * @param message
+  *   human-readable explanation
+  * @param field
+  *   optional field name when the error relates to a specific input
+  */
 final case class ApiError(
-  code: String,
-  message: String,
-  field: Option[String] = None
+    code: String,
+    message: String,
+    field: Option[String] = None,
 )
 
-/**
- * Pagination metadata for list responses.
- *
- * @param page       current 0-based page index
- * @param pageSize   number of items per page
- * @param totalItems total number of items across all pages
- */
+/** Pagination metadata for list responses.
+  *
+  * @param page
+  *   current 0-based page index
+  * @param pageSize
+  *   number of items per page
+  * @param totalItems
+  *   total number of items across all pages
+  */
 final case class Pagination(
-  page: Int,
-  pageSize: Int,
-  totalItems: Long
+    page: Int,
+    pageSize: Int,
+    totalItems: Long,
 ):
   def totalPages: Int =
     if pageSize <= 0 then 0
     else Math.ceil(totalItems.toDouble / pageSize).toInt
 
-/**
- * A paginated list response envelope.
- *
- * @param items      the items on the current page
- * @param pagination pagination metadata
- * @tparam A         the item type
- */
+/** A paginated list response envelope.
+  *
+  * @param items
+  *   the items on the current page
+  * @param pagination
+  *   pagination metadata
+  * @tparam A
+  *   the item type
+  */
 final case class PagedResponse[A](
-  items: List[A],
-  pagination: Pagination
+    items: List[A],
+    pagination: Pagination,
 )

modules/api/src/test/scala/de/nowchess/api/board/BoardTest.scala

@@ -1,5 +1,6 @@
 package de.nowchess.api.board
 
+import de.nowchess.api.move.Move
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
 
@@ -7,13 +8,9 @@ class BoardTest extends AnyFunSuite with Matchers:
 
   private val e2 = Square(File.E, Rank.R2)
   private val e4 = Square(File.E, Rank.R4)
-  private val d7 = Square(File.D, Rank.R7)
 
-  test("pieceAt returns Some for occupied square") {
+  test("pieceAt resolves occupied and empty squares") {
     Board.initial.pieceAt(e2) shouldBe Some(Piece.WhitePawn)
-  }
-
-  test("pieceAt returns None for empty square") {
     Board.initial.pieceAt(e4) shouldBe None
   }
 
@@ -25,55 +22,43 @@ class BoardTest extends AnyFunSuite with Matchers:
   }
 
   test("withMove returns captured piece when destination is occupied") {
-    val from = Square(File.A, Rank.R1)
-    val to   = Square(File.A, Rank.R8)
-    val b    = Board(Map(from -> Piece.WhiteRook, to -> Piece.BlackRook))
+    val from              = Square(File.A, Rank.R1)
+    val to                = Square(File.A, Rank.R8)
+    val b                 = Board(Map(from -> Piece.WhiteRook, to -> Piece.BlackRook))
     val (board, captured) = b.withMove(from, to)
     captured shouldBe Some(Piece.BlackRook)
     board.pieceAt(to) shouldBe Some(Piece.WhiteRook)
     board.pieceAt(from) shouldBe None
   }
 
-  test("pieces returns the underlying map") {
-    val map = Map(e2 -> Piece.WhitePawn)
-    val b   = Board(map)
-    b.pieces shouldBe map
-  }
-
-  test("Board.apply constructs board from map") {
+  test("Board.apply and pieces expose the wrapped map") {
     val map = Map(e2 -> Piece.WhitePawn)
     val b   = Board(map)
     b.pieceAt(e2) shouldBe Some(Piece.WhitePawn)
+    b.pieces shouldBe map
   }
 
-  test("initial board has 32 pieces") {
+  test("initial board has expected material and pawn placement") {
     Board.initial.pieces should have size 32
-  }
-
-  test("initial board has 16 white pieces") {
     Board.initial.pieces.values.count(_.color == Color.White) shouldBe 16
-  }
-
-  test("initial board has 16 black pieces") {
     Board.initial.pieces.values.count(_.color == Color.Black) shouldBe 16
-  }
 
-  test("initial board white pawns on rank 2") {
     File.values.foreach { file =>
       Board.initial.pieceAt(Square(file, Rank.R2)) shouldBe Some(Piece.WhitePawn)
-    }
-  }
-
-  test("initial board black pawns on rank 7") {
-    File.values.foreach { file =>
       Board.initial.pieceAt(Square(file, Rank.R7)) shouldBe Some(Piece.BlackPawn)
     }
   }
 
   test("initial board white back rank") {
     val expectedBackRank = Vector(
-      PieceType.Rook, PieceType.Knight, PieceType.Bishop, PieceType.Queen,
-      PieceType.King, PieceType.Bishop, PieceType.Knight, PieceType.Rook
+      PieceType.Rook,
+      PieceType.Knight,
+      PieceType.Bishop,
+      PieceType.Queen,
+      PieceType.King,
+      PieceType.Bishop,
+      PieceType.Knight,
+      PieceType.Rook,
     )
     File.values.zipWithIndex.foreach { (file, i) =>
       Board.initial.pieceAt(Square(file, Rank.R1)) shouldBe
@@ -83,8 +68,14 @@ class BoardTest extends AnyFunSuite with Matchers:
 
   test("initial board black back rank") {
     val expectedBackRank = Vector(
-      PieceType.Rook, PieceType.Knight, PieceType.Bishop, PieceType.Queen,
-      PieceType.King, PieceType.Bishop, PieceType.Knight, PieceType.Rook
+      PieceType.Rook,
+      PieceType.Knight,
+      PieceType.Bishop,
+      PieceType.Queen,
+      PieceType.King,
+      PieceType.Bishop,
+      PieceType.Knight,
+      PieceType.Rook,
     )
     File.values.zipWithIndex.foreach { (file, i) =>
       Board.initial.pieceAt(Square(file, Rank.R8)) shouldBe
@@ -97,26 +88,31 @@ class BoardTest extends AnyFunSuite with Matchers:
     for
       rank <- emptyRanks
       file <- File.values
-    do
-      Board.initial.pieceAt(Square(file, rank)) shouldBe None
+    do Board.initial.pieceAt(Square(file, rank)) shouldBe None
   }
 
-  test("updated adds or replaces piece at square") {
-    val b = Board(Map(e2 -> Piece.WhitePawn))
-    val updated = b.updated(e4, Piece.WhiteKnight)
-    updated.pieceAt(e2) shouldBe Some(Piece.WhitePawn)
-    updated.pieceAt(e4) shouldBe Some(Piece.WhiteKnight)
-  }
+  test("updated adds and replaces piece at squares") {
+    val b     = Board(Map(e2 -> Piece.WhitePawn))
+    val added = b.updated(e4, Piece.WhiteKnight)
+    added.pieceAt(e2) shouldBe Some(Piece.WhitePawn)
+    added.pieceAt(e4) shouldBe Some(Piece.WhiteKnight)
 
-  test("updated replaces existing piece") {
-    val b = Board(Map(e2 -> Piece.WhitePawn))
-    val updated = b.updated(e2, Piece.WhiteKnight)
-    updated.pieceAt(e2) shouldBe Some(Piece.WhiteKnight)
+    val replaced = b.updated(e2, Piece.WhiteKnight)
+    replaced.pieceAt(e2) shouldBe Some(Piece.WhiteKnight)
   }
 
   test("removed deletes piece from board") {
-    val b = Board(Map(e2 -> Piece.WhitePawn, e4 -> Piece.WhiteKnight))
+    val b       = Board(Map(e2 -> Piece.WhitePawn, e4 -> Piece.WhiteKnight))
     val removed = b.removed(e2)
     removed.pieceAt(e2) shouldBe None
     removed.pieceAt(e4) shouldBe Some(Piece.WhiteKnight)
   }
+
+  test("applyMove uses move.from and move.to to relocate a piece") {
+    val b = Board(Map(e2 -> Piece.WhitePawn))
+
+    val moved = b.applyMove(Move(e2, e4))
+
+    moved.pieceAt(e4) shouldBe Some(Piece.WhitePawn)
+    moved.pieceAt(e2) shouldBe None
+  }

modules/api/src/test/scala/de/nowchess/api/board/CastlingRightsTest.scala

@@ -0,0 +1,56 @@
+package de.nowchess.api.board
+
+import org.scalatest.funsuite.AnyFunSuite
+import org.scalatest.matchers.should.Matchers
+
+class CastlingRightsTest extends AnyFunSuite with Matchers:
+
+  test("hasAnyRights and hasRights reflect current flags"):
+    val rights = CastlingRights(
+      whiteKingSide = true,
+      whiteQueenSide = false,
+      blackKingSide = false,
+      blackQueenSide = true,
+    )
+
+    rights.hasAnyRights shouldBe true
+    rights.hasRights(Color.White) shouldBe true
+    rights.hasRights(Color.Black) shouldBe true
+
+    CastlingRights.None.hasAnyRights shouldBe false
+    CastlingRights.None.hasRights(Color.White) shouldBe false
+    CastlingRights.None.hasRights(Color.Black) shouldBe false
+
+  test("revokeColor clears both castling sides for selected color"):
+    val all = CastlingRights.All
+
+    val whiteRevoked = all.revokeColor(Color.White)
+    whiteRevoked.whiteKingSide shouldBe false
+    whiteRevoked.whiteQueenSide shouldBe false
+    whiteRevoked.blackKingSide shouldBe true
+    whiteRevoked.blackQueenSide shouldBe true
+
+    val blackRevoked = all.revokeColor(Color.Black)
+    blackRevoked.whiteKingSide shouldBe true
+    blackRevoked.whiteQueenSide shouldBe true
+    blackRevoked.blackKingSide shouldBe false
+    blackRevoked.blackQueenSide shouldBe false
+
+  test("revokeKingSide and revokeQueenSide disable only requested side"):
+    val all = CastlingRights.All
+
+    val whiteKingSideRevoked = all.revokeKingSide(Color.White)
+    whiteKingSideRevoked.whiteKingSide shouldBe false
+    whiteKingSideRevoked.whiteQueenSide shouldBe true
+
+    val whiteQueenSideRevoked = all.revokeQueenSide(Color.White)
+    whiteQueenSideRevoked.whiteKingSide shouldBe true
+    whiteQueenSideRevoked.whiteQueenSide shouldBe false
+
+    val blackKingSideRevoked = all.revokeKingSide(Color.Black)
+    blackKingSideRevoked.blackKingSide shouldBe false
+    blackKingSideRevoked.blackQueenSide shouldBe true
+
+    val blackQueenSideRevoked = all.revokeQueenSide(Color.Black)
+    blackQueenSideRevoked.blackKingSide shouldBe true
+    blackQueenSideRevoked.blackQueenSide shouldBe false

modules/api/src/test/scala/de/nowchess/api/board/ColorTest.scala

@@ -5,18 +5,13 @@ import org.scalatest.matchers.should.Matchers
 
 class ColorTest extends AnyFunSuite with Matchers:
 
-  test("White.opposite returns Black") {
-    Color.White.opposite shouldBe Color.Black
-  }
+  test("Color values expose opposite and label consistently"):
+    val cases = List(
+      (Color.White, Color.Black, "White"),
+      (Color.Black, Color.White, "Black"),
+    )
 
-  test("Black.opposite returns White") {
-    Color.Black.opposite shouldBe Color.White
-  }
-
-  test("White.label returns 'White'") {
-    Color.White.label shouldBe "White"
-  }
-
-  test("Black.label returns 'Black'") {
-    Color.Black.label shouldBe "Black"
-  }
+    cases.foreach { (color, opposite, label) =>
+      color.opposite shouldBe opposite
+      color.label shouldBe label
+    }

modules/api/src/test/scala/de/nowchess/api/board/PieceTest.scala

@@ -7,54 +7,27 @@ class PieceTest extends AnyFunSuite with Matchers:
 
   test("Piece holds color and pieceType") {
     val p = Piece(Color.White, PieceType.Queen)
-    p.color    shouldBe Color.White
+    p.color shouldBe Color.White
     p.pieceType shouldBe PieceType.Queen
   }
 
-  test("WhitePawn convenience constant") {
-    Piece.WhitePawn shouldBe Piece(Color.White, PieceType.Pawn)
-  }
+  test("all convenience constants map to expected color and piece type") {
+    val expected = List(
+      Piece.WhitePawn   -> Piece(Color.White, PieceType.Pawn),
+      Piece.WhiteKnight -> Piece(Color.White, PieceType.Knight),
+      Piece.WhiteBishop -> Piece(Color.White, PieceType.Bishop),
+      Piece.WhiteRook   -> Piece(Color.White, PieceType.Rook),
+      Piece.WhiteQueen  -> Piece(Color.White, PieceType.Queen),
+      Piece.WhiteKing   -> Piece(Color.White, PieceType.King),
+      Piece.BlackPawn   -> Piece(Color.Black, PieceType.Pawn),
+      Piece.BlackKnight -> Piece(Color.Black, PieceType.Knight),
+      Piece.BlackBishop -> Piece(Color.Black, PieceType.Bishop),
+      Piece.BlackRook   -> Piece(Color.Black, PieceType.Rook),
+      Piece.BlackQueen  -> Piece(Color.Black, PieceType.Queen),
+      Piece.BlackKing   -> Piece(Color.Black, PieceType.King),
+    )
 
-  test("WhiteKnight convenience constant") {
-    Piece.WhiteKnight shouldBe Piece(Color.White, PieceType.Knight)
-  }
-
-  test("WhiteBishop convenience constant") {
-    Piece.WhiteBishop shouldBe Piece(Color.White, PieceType.Bishop)
-  }
-
-  test("WhiteRook convenience constant") {
-    Piece.WhiteRook shouldBe Piece(Color.White, PieceType.Rook)
-  }
-
-  test("WhiteQueen convenience constant") {
-    Piece.WhiteQueen shouldBe Piece(Color.White, PieceType.Queen)
-  }
-
-  test("WhiteKing convenience constant") {
-    Piece.WhiteKing shouldBe Piece(Color.White, PieceType.King)
-  }
-
-  test("BlackPawn convenience constant") {
-    Piece.BlackPawn shouldBe Piece(Color.Black, PieceType.Pawn)
-  }
-
-  test("BlackKnight convenience constant") {
-    Piece.BlackKnight shouldBe Piece(Color.Black, PieceType.Knight)
-  }
-
-  test("BlackBishop convenience constant") {
-    Piece.BlackBishop shouldBe Piece(Color.Black, PieceType.Bishop)
-  }
-
-  test("BlackRook convenience constant") {
-    Piece.BlackRook shouldBe Piece(Color.Black, PieceType.Rook)
-  }
-
-  test("BlackQueen convenience constant") {
-    Piece.BlackQueen shouldBe Piece(Color.Black, PieceType.Queen)
-  }
-
-  test("BlackKing convenience constant") {
-    Piece.BlackKing shouldBe Piece(Color.Black, PieceType.King)
+    expected.foreach { case (actual, wanted) =>
+      actual shouldBe wanted
+    }
   }

modules/api/src/test/scala/de/nowchess/api/board/PieceTypeTest.scala

@@ -5,26 +5,16 @@ import org.scalatest.matchers.should.Matchers
 
 class PieceTypeTest extends AnyFunSuite with Matchers:
 
-  test("Pawn.label returns 'Pawn'") {
-    PieceType.Pawn.label shouldBe "Pawn"
-  }
+  test("PieceType values expose the expected labels"):
+    val expectedLabels = List(
+      PieceType.Pawn   -> "Pawn",
+      PieceType.Knight -> "Knight",
+      PieceType.Bishop -> "Bishop",
+      PieceType.Rook   -> "Rook",
+      PieceType.Queen  -> "Queen",
+      PieceType.King   -> "King",
+    )
 
-  test("Knight.label returns 'Knight'") {
-    PieceType.Knight.label shouldBe "Knight"
-  }
-
-  test("Bishop.label returns 'Bishop'") {
-    PieceType.Bishop.label shouldBe "Bishop"
-  }
-
-  test("Rook.label returns 'Rook'") {
-    PieceType.Rook.label shouldBe "Rook"
-  }
-
-  test("Queen.label returns 'Queen'") {
-    PieceType.Queen.label shouldBe "Queen"
-  }
-
-  test("King.label returns 'King'") {
-    PieceType.King.label shouldBe "King"
-  }
+    expectedLabels.foreach { (pieceType, expectedLabel) =>
+      pieceType.label shouldBe expectedLabel
+    }

modules/api/src/test/scala/de/nowchess/api/board/SquareTest.scala

@@ -5,58 +5,32 @@ import org.scalatest.matchers.should.Matchers
 
 class SquareTest extends AnyFunSuite with Matchers:
 
-  test("Square.toString produces lowercase file and rank number") {
-    Square(File.E, Rank.R4).toString shouldBe "e4"
-  }
-
-  test("Square.toString for a1") {
+  test("toString renders algebraic notation for edge and middle squares") {
     Square(File.A, Rank.R1).toString shouldBe "a1"
-  }
-
-  test("Square.toString for h8") {
+    Square(File.E, Rank.R4).toString shouldBe "e4"
     Square(File.H, Rank.R8).toString shouldBe "h8"
   }
 
-  test("fromAlgebraic parses valid square e4") {
-    Square.fromAlgebraic("e4") shouldBe Some(Square(File.E, Rank.R4))
+  test("fromAlgebraic parses valid coordinates including case-insensitive files") {
+    val expected = List(
+      "a1" -> Square(File.A, Rank.R1),
+      "e4" -> Square(File.E, Rank.R4),
+      "h8" -> Square(File.H, Rank.R8),
+      "E4" -> Square(File.E, Rank.R4),
+    )
+    expected.foreach { case (raw, sq) =>
+      Square.fromAlgebraic(raw) shouldBe Some(sq)
+    }
   }
 
-  test("fromAlgebraic parses valid square a1") {
-    Square.fromAlgebraic("a1") shouldBe Some(Square(File.A, Rank.R1))
+  test("fromAlgebraic rejects malformed coordinates") {
+    List("", "e", "e42", "z4", "ex", "e0", "e9").foreach { raw =>
+      Square.fromAlgebraic(raw) shouldBe None
+    }
   }
 
-  test("fromAlgebraic parses valid square h8") {
-    Square.fromAlgebraic("h8") shouldBe Some(Square(File.H, Rank.R8))
-  }
-
-  test("fromAlgebraic is case-insensitive for file") {
-    Square.fromAlgebraic("E4") shouldBe Some(Square(File.E, Rank.R4))
-  }
-
-  test("fromAlgebraic returns None for empty string") {
-    Square.fromAlgebraic("") shouldBe None
-  }
-
-  test("fromAlgebraic returns None for string too short") {
-    Square.fromAlgebraic("e") shouldBe None
-  }
-
-  test("fromAlgebraic returns None for string too long") {
-    Square.fromAlgebraic("e42") shouldBe None
-  }
-
-  test("fromAlgebraic returns None for invalid file character") {
-    Square.fromAlgebraic("z4") shouldBe None
-  }
-
-  test("fromAlgebraic returns None for non-digit rank") {
-    Square.fromAlgebraic("ex") shouldBe None
-  }
-
-  test("fromAlgebraic returns None for rank 0") {
-    Square.fromAlgebraic("e0") shouldBe None
-  }
-
-  test("fromAlgebraic returns None for rank 9") {
-    Square.fromAlgebraic("e9") shouldBe None
+  test("offset returns Some in-bounds and None out-of-bounds") {
+    Square(File.E, Rank.R4).offset(1, 2) shouldBe Some(Square(File.F, Rank.R6))
+    Square(File.A, Rank.R1).offset(-1, 0) shouldBe None
+    Square(File.H, Rank.R8).offset(0, 1) shouldBe None
   }

modules/api/src/test/scala/de/nowchess/api/game/GameContextTest.scala

@@ -0,0 +1,73 @@
+package de.nowchess.api.game
+
+import de.nowchess.api.board.{Board, CastlingRights, Color, File, Rank, Square}
+import de.nowchess.api.move.Move
+import de.nowchess.api.game.{DrawReason, GameResult}
+import org.scalatest.funsuite.AnyFunSuite
+import org.scalatest.matchers.should.Matchers
+
+class GameContextTest extends AnyFunSuite with Matchers:
+
+  test("GameContext.initial exposes expected default state"):
+    val initial = GameContext.initial
+
+    initial.board shouldBe Board.initial
+    initial.turn shouldBe Color.White
+    initial.castlingRights shouldBe CastlingRights.Initial
+    initial.enPassantSquare shouldBe None
+    initial.halfMoveClock shouldBe 0
+    initial.moves shouldBe List.empty
+    initial.result shouldBe None
+
+  test("withBoard updates only board"):
+    val square       = Square(File.E, Rank.R4)
+    val updatedBoard = Board.initial.updated(square, de.nowchess.api.board.Piece.WhiteQueen)
+    val updated      = GameContext.initial.withBoard(updatedBoard)
+    updated.board shouldBe updatedBoard
+    updated.turn shouldBe GameContext.initial.turn
+    updated.castlingRights shouldBe GameContext.initial.castlingRights
+    updated.enPassantSquare shouldBe GameContext.initial.enPassantSquare
+    updated.halfMoveClock shouldBe GameContext.initial.halfMoveClock
+    updated.moves shouldBe GameContext.initial.moves
+
+  test("withers update only targeted fields"):
+    val initial = GameContext.initial
+    val rights = CastlingRights(
+      whiteKingSide = true,
+      whiteQueenSide = false,
+      blackKingSide = false,
+      blackQueenSide = true,
+    )
+    val square        = Some(Square(File.E, Rank.R3))
+    val updatedTurn   = initial.withTurn(Color.Black)
+    val updatedRights = initial.withCastlingRights(rights)
+    val updatedEp     = initial.withEnPassantSquare(square)
+    val updatedClock  = initial.withHalfMoveClock(17)
+
+    updatedTurn.turn shouldBe Color.Black
+    updatedTurn.board shouldBe initial.board
+
+    updatedRights.castlingRights shouldBe rights
+    updatedRights.turn shouldBe initial.turn
+
+    updatedEp.enPassantSquare shouldBe square
+    updatedEp.castlingRights shouldBe initial.castlingRights
+
+    updatedClock.halfMoveClock shouldBe 17
+    updatedClock.moves shouldBe initial.moves
+
+  test("withMove appends move to history"):
+    val move = Move(Square(File.E, Rank.R2), Square(File.E, Rank.R4))
+    GameContext.initial.withMove(move).moves shouldBe List(move)
+
+  test("withResult sets Win result"):
+    val win = Some(GameResult.Win(Color.White))
+    GameContext.initial.withResult(win).result shouldBe win
+
+  test("withResult sets Draw result"):
+    val draw = Some(GameResult.Draw(DrawReason.Stalemate))
+    GameContext.initial.withResult(draw).result shouldBe draw
+
+  test("withResult clears result"):
+    val ctx = GameContext.initial.withResult(Some(GameResult.Win(Color.Black)))
+    ctx.withResult(None).result shouldBe None

modules/api/src/test/scala/de/nowchess/api/game/GameStateTest.scala

@@ -1,77 +0,0 @@
-package de.nowchess.api.game
-
-import de.nowchess.api.board.Color
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class GameStateTest extends AnyFunSuite with Matchers:
-
-  test("CastlingRights.None has both flags false") {
-    CastlingRights.None.kingSide  shouldBe false
-    CastlingRights.None.queenSide shouldBe false
-  }
-
-  test("CastlingRights.Both has both flags true") {
-    CastlingRights.Both.kingSide  shouldBe true
-    CastlingRights.Both.queenSide shouldBe true
-  }
-
-  test("CastlingRights constructor sets fields") {
-    val cr = CastlingRights(kingSide = true, queenSide = false)
-    cr.kingSide  shouldBe true
-    cr.queenSide shouldBe false
-  }
-
-  test("GameResult cases exist") {
-    GameResult.WhiteWins shouldBe GameResult.WhiteWins
-    GameResult.BlackWins shouldBe GameResult.BlackWins
-    GameResult.Draw      shouldBe GameResult.Draw
-  }
-
-  test("GameStatus.NotStarted") {
-    GameStatus.NotStarted shouldBe GameStatus.NotStarted
-  }
-
-  test("GameStatus.InProgress") {
-    GameStatus.InProgress shouldBe GameStatus.InProgress
-  }
-
-  test("GameStatus.Finished carries result") {
-    val status = GameStatus.Finished(GameResult.Draw)
-    status shouldBe GameStatus.Finished(GameResult.Draw)
-    status match
-      case GameStatus.Finished(r) => r shouldBe GameResult.Draw
-      case _                      => fail("expected Finished")
-  }
-
-  test("GameState.initial has standard FEN piece placement") {
-    GameState.initial.piecePlacement shouldBe "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR"
-  }
-
-  test("GameState.initial active color is White") {
-    GameState.initial.activeColor shouldBe Color.White
-  }
-
-  test("GameState.initial white has full castling rights") {
-    GameState.initial.castlingWhite shouldBe CastlingRights.Both
-  }
-
-  test("GameState.initial black has full castling rights") {
-    GameState.initial.castlingBlack shouldBe CastlingRights.Both
-  }
-
-  test("GameState.initial en-passant target is None") {
-    GameState.initial.enPassantTarget shouldBe None
-  }
-
-  test("GameState.initial half-move clock is 0") {
-    GameState.initial.halfMoveClock shouldBe 0
-  }
-
-  test("GameState.initial full-move number is 1") {
-    GameState.initial.fullMoveNumber shouldBe 1
-  }
-
-  test("GameState.initial status is InProgress") {
-    GameState.initial.status shouldBe GameStatus.InProgress
-  }

modules/api/src/test/scala/de/nowchess/api/move/MoveTest.scala

@@ -9,48 +9,26 @@ class MoveTest extends AnyFunSuite with Matchers:
   private val e2 = Square(File.E, Rank.R2)
   private val e4 = Square(File.E, Rank.R4)
 
-  test("Move defaults moveType to Normal") {
-    val m = Move(e2, e4)
-    m.moveType shouldBe MoveType.Normal
-  }
-
-  test("Move stores from and to squares") {
+  test("Move defaults to Normal and keeps from/to squares") {
     val m = Move(e2, e4)
     m.from shouldBe e2
-    m.to   shouldBe e4
+    m.to shouldBe e4
+    m.moveType shouldBe MoveType.Normal()
   }
 
-  test("Move with CastleKingside moveType") {
-    val m = Move(e2, e4, MoveType.CastleKingside)
-    m.moveType shouldBe MoveType.CastleKingside
-  }
+  test("Move accepts all supported move types") {
+    val moveTypes = List(
+      MoveType.Normal(isCapture = true),
+      MoveType.CastleKingside,
+      MoveType.CastleQueenside,
+      MoveType.EnPassant,
+      MoveType.Promotion(PromotionPiece.Queen),
+      MoveType.Promotion(PromotionPiece.Rook),
+      MoveType.Promotion(PromotionPiece.Bishop),
+      MoveType.Promotion(PromotionPiece.Knight),
+    )
 
-  test("Move with CastleQueenside moveType") {
-    val m = Move(e2, e4, MoveType.CastleQueenside)
-    m.moveType shouldBe MoveType.CastleQueenside
-  }
-
-  test("Move with EnPassant moveType") {
-    val m = Move(e2, e4, MoveType.EnPassant)
-    m.moveType shouldBe MoveType.EnPassant
-  }
-
-  test("Move with Promotion to Queen") {
-    val m = Move(e2, e4, MoveType.Promotion(PromotionPiece.Queen))
-    m.moveType shouldBe MoveType.Promotion(PromotionPiece.Queen)
-  }
-
-  test("Move with Promotion to Knight") {
-    val m = Move(e2, e4, MoveType.Promotion(PromotionPiece.Knight))
-    m.moveType shouldBe MoveType.Promotion(PromotionPiece.Knight)
-  }
-
-  test("Move with Promotion to Bishop") {
-    val m = Move(e2, e4, MoveType.Promotion(PromotionPiece.Bishop))
-    m.moveType shouldBe MoveType.Promotion(PromotionPiece.Bishop)
-  }
-
-  test("Move with Promotion to Rook") {
-    val m = Move(e2, e4, MoveType.Promotion(PromotionPiece.Rook))
-    m.moveType shouldBe MoveType.Promotion(PromotionPiece.Rook)
+    moveTypes.foreach { moveType =>
+      Move(e2, e4, moveType).moveType shouldBe moveType
+    }
   }

modules/api/src/test/scala/de/nowchess/api/player/PlayerInfoTest.scala

@@ -5,19 +5,14 @@ import org.scalatest.matchers.should.Matchers
 
 class PlayerInfoTest extends AnyFunSuite with Matchers:
 
-  test("PlayerId.apply wraps a string") {
-    val id = PlayerId("player-123")
-    id.value shouldBe "player-123"
-  }
+  test("PlayerId and PlayerInfo preserve constructor values") {
+    val raw = "player-123"
+    val id  = PlayerId(raw)
 
-  test("PlayerId.value unwraps to original string") {
-    val raw = "abc-456"
-    PlayerId(raw).value shouldBe raw
-  }
+    id.value shouldBe raw
 
-  test("PlayerInfo holds id and displayName") {
-    val id   = PlayerId("p1")
-    val info = PlayerInfo(id, "Magnus")
-    info.id.value      shouldBe "p1"
-    info.displayName   shouldBe "Magnus"
+    val playerId = PlayerId("p1")
+    val info     = PlayerInfo(playerId, "Magnus")
+    info.id.value shouldBe "p1"
+    info.displayName shouldBe "Magnus"
   }

modules/api/src/test/scala/de/nowchess/api/response/ApiResponseTest.scala

@@ -5,58 +5,32 @@ import org.scalatest.matchers.should.Matchers
 
 class ApiResponseTest extends AnyFunSuite with Matchers:
 
-  test("ApiResponse.Success carries data") {
+  test("ApiResponse factories and payload wrappers keep values") {
     val r = ApiResponse.Success(42)
     r.data shouldBe 42
-  }
 
-  test("ApiResponse.Failure carries error list") {
     val err = ApiError("CODE", "msg")
-    val r   = ApiResponse.Failure(List(err))
-    r.errors shouldBe List(err)
-  }
+    ApiResponse.Failure(List(err)).errors shouldBe List(err)
+    ApiResponse.error(err) shouldBe ApiResponse.Failure(List(err))
 
-  test("ApiResponse.error creates single-error Failure") {
-    val err = ApiError("NOT_FOUND", "not found")
-    val f   = ApiResponse.error(err)
-    f shouldBe ApiResponse.Failure(List(err))
-  }
-
-  test("ApiError holds code and message") {
     val e = ApiError("CODE", "message")
-    e.code    shouldBe "CODE"
+    e.code shouldBe "CODE"
     e.message shouldBe "message"
-    e.field   shouldBe None
+    e.field shouldBe None
+    ApiError("INVALID", "bad value", Some("email")).field shouldBe Some("email")
   }
 
-  test("ApiError holds optional field") {
-    val e = ApiError("INVALID", "bad value", Some("email"))
-    e.field shouldBe Some("email")
-  }
-
-  test("Pagination.totalPages with exact division") {
+  test("Pagination.totalPages handles normal and guarded inputs") {
     Pagination(page = 0, pageSize = 10, totalItems = 30).totalPages shouldBe 3
-  }
-
-  test("Pagination.totalPages rounds up") {
     Pagination(page = 0, pageSize = 10, totalItems = 25).totalPages shouldBe 3
-  }
-
-  test("Pagination.totalPages is 0 when totalItems is 0") {
     Pagination(page = 0, pageSize = 10, totalItems = 0).totalPages shouldBe 0
-  }
-
-  test("Pagination.totalPages is 0 when pageSize is 0") {
     Pagination(page = 0, pageSize = 0, totalItems = 100).totalPages shouldBe 0
-  }
-
-  test("Pagination.totalPages is 0 when pageSize is negative") {
     Pagination(page = 0, pageSize = -1, totalItems = 100).totalPages shouldBe 0
   }
 
   test("PagedResponse holds items and pagination") {
     val pagination = Pagination(page = 1, pageSize = 5, totalItems = 20)
     val pr         = PagedResponse(List("a", "b"), pagination)
-    pr.items      shouldBe List("a", "b")
+    pr.items shouldBe List("a", "b")
     pr.pagination shouldBe pagination
   }

modules/api/versions.env

@@ -1,3 +1,3 @@
 MAJOR=0
-MINOR=1
+MINOR=5
 PATCH=0

modules/core/CHANGELOG.md

@@ -165,3 +165,98 @@
 * correct test board positions and captureOutput/withInput interaction ([f0481e2](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/f0481e2561b779df00925b46ee281dc36a795150))
 * update main class path in build configuration and adjust VCS directory mapping ([7b1f8b1](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/7b1f8b117623d327232a1a92a8a44d18582e0189))
 * update move validation to check for king safety ([#13](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/13)) ([e5e20c5](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/e5e20c566e368b12ca1dc59680c34e9112bf6762))
+##  (2026-04-03)
+
+### Features
+
+* add GameRules stub with PositionStatus enum ([76d4168](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/76d4168038de23e5d6083d4e8f0504fbf31d15a3))
+* add MovedInCheck/Checkmate/Stalemate MoveResult variants (stub dispatch) ([8b7ec57](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/8b7ec57e5ea6ee1615a1883848a426dc07d26364))
+* implement GameRules with isInCheck, legalMoves, gameStatus ([94a02ff](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/94a02ff6849436d9496c70a0f16c21666dae8e4e))
+* implement legal castling ([#1](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/1)) ([00d326c](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/00d326c1ba67711fbe180f04e1100c3f01dd0254))
+* NCS-10 Implement Pawn Promotion ([#12](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/12)) ([13bfc16](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/13bfc16cfe25db78ec607db523ca6d993c13430c))
+* NCS-11 50-move rule ([#9](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/9)) ([412ed98](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/412ed986a95703a3b282276540153480ceed229d))
+* NCS-16 Core Separation via Patterns ([#10](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/10)) ([1361dfc](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/1361dfc89553b146864fb8ff3526cf12cf3f293a))
+* NCS-17 Implement basic ScalaFX UI ([#14](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/14)) ([3ff8031](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/3ff80318b4f16c59733a46498581a5c27f048287))
+* NCS-21 Write Scripts to automate certain tasks ([#15](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/15)) ([8051871](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/80518719d536a087d339fe02530825dc07f8b388))
+* NCS-6 Implementing FEN & PGN ([#7](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/7)) ([f28e69d](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/f28e69dc181416aa2f221fdc4b45c2cda5efbf07))
+* NCS-9 En passant implementation ([#8](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/8)) ([919beb3](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/919beb3b4bfa8caf2f90976a415fe9b19b7e9747))
+* wire check/checkmate/stalemate into processMove and gameLoop ([5264a22](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/5264a225418b885c5e6ea6411b96f85e38837f6c))
+
+### Bug Fixes
+
+* add missing kings to gameLoop capture test board ([aedd787](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/aedd787b77203c2af934751dba7b784eaf165032))
+* correct test board positions and captureOutput/withInput interaction ([f0481e2](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/f0481e2561b779df00925b46ee281dc36a795150))
+* update main class path in build configuration and adjust VCS directory mapping ([7b1f8b1](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/7b1f8b117623d327232a1a92a8a44d18582e0189))
+* update move validation to check for king safety ([#13](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/13)) ([e5e20c5](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/e5e20c566e368b12ca1dc59680c34e9112bf6762))
+##  (2026-04-07)
+
+### Features
+
+* add GameRules stub with PositionStatus enum ([76d4168](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/76d4168038de23e5d6083d4e8f0504fbf31d15a3))
+* add MovedInCheck/Checkmate/Stalemate MoveResult variants (stub dispatch) ([8b7ec57](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/8b7ec57e5ea6ee1615a1883848a426dc07d26364))
+* implement GameRules with isInCheck, legalMoves, gameStatus ([94a02ff](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/94a02ff6849436d9496c70a0f16c21666dae8e4e))
+* implement legal castling ([#1](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/1)) ([00d326c](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/00d326c1ba67711fbe180f04e1100c3f01dd0254))
+* NCS-10 Implement Pawn Promotion ([#12](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/12)) ([13bfc16](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/13bfc16cfe25db78ec607db523ca6d993c13430c))
+* NCS-11 50-move rule ([#9](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/9)) ([412ed98](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/412ed986a95703a3b282276540153480ceed229d))
+* NCS-16 Core Separation via Patterns ([#10](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/10)) ([1361dfc](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/1361dfc89553b146864fb8ff3526cf12cf3f293a))
+* NCS-17 Implement basic ScalaFX UI ([#14](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/14)) ([3ff8031](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/3ff80318b4f16c59733a46498581a5c27f048287))
+* NCS-21 Write Scripts to automate certain tasks ([#15](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/15)) ([8051871](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/80518719d536a087d339fe02530825dc07f8b388))
+* NCS-6 Implementing FEN & PGN ([#7](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/7)) ([f28e69d](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/f28e69dc181416aa2f221fdc4b45c2cda5efbf07))
+* NCS-9 En passant implementation ([#8](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/8)) ([919beb3](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/919beb3b4bfa8caf2f90976a415fe9b19b7e9747))
+* wire check/checkmate/stalemate into processMove and gameLoop ([5264a22](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/5264a225418b885c5e6ea6411b96f85e38837f6c))
+
+### Bug Fixes
+
+* add missing kings to gameLoop capture test board ([aedd787](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/aedd787b77203c2af934751dba7b784eaf165032))
+* correct test board positions and captureOutput/withInput interaction ([f0481e2](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/f0481e2561b779df00925b46ee281dc36a795150))
+* update main class path in build configuration and adjust VCS directory mapping ([7b1f8b1](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/7b1f8b117623d327232a1a92a8a44d18582e0189))
+* update move validation to check for king safety ([#13](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/13)) ([e5e20c5](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/e5e20c566e368b12ca1dc59680c34e9112bf6762))
+##  (2026-04-12)
+
+### Features
+
+* add GameRules stub with PositionStatus enum ([76d4168](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/76d4168038de23e5d6083d4e8f0504fbf31d15a3))
+* add MovedInCheck/Checkmate/Stalemate MoveResult variants (stub dispatch) ([8b7ec57](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/8b7ec57e5ea6ee1615a1883848a426dc07d26364))
+* implement GameRules with isInCheck, legalMoves, gameStatus ([94a02ff](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/94a02ff6849436d9496c70a0f16c21666dae8e4e))
+* implement legal castling ([#1](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/1)) ([00d326c](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/00d326c1ba67711fbe180f04e1100c3f01dd0254))
+* NCS-10 Implement Pawn Promotion ([#12](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/12)) ([13bfc16](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/13bfc16cfe25db78ec607db523ca6d993c13430c))
+* NCS-11 50-move rule ([#9](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/9)) ([412ed98](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/412ed986a95703a3b282276540153480ceed229d))
+* NCS-16 Core Separation via Patterns ([#10](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/10)) ([1361dfc](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/1361dfc89553b146864fb8ff3526cf12cf3f293a))
+* NCS-17 Implement basic ScalaFX UI ([#14](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/14)) ([3ff8031](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/3ff80318b4f16c59733a46498581a5c27f048287))
+* NCS-21 Write Scripts to automate certain tasks ([#15](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/15)) ([8051871](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/80518719d536a087d339fe02530825dc07f8b388))
+* NCS-25 Add linters to keep quality up ([#27](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/27)) ([fd4e67d](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/fd4e67d4f782a7e955822d90cb909d0a81676fb2))
+* NCS-6 Implementing FEN & PGN ([#7](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/7)) ([f28e69d](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/f28e69dc181416aa2f221fdc4b45c2cda5efbf07))
+* NCS-9 En passant implementation ([#8](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/8)) ([919beb3](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/919beb3b4bfa8caf2f90976a415fe9b19b7e9747))
+* wire check/checkmate/stalemate into processMove and gameLoop ([5264a22](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/5264a225418b885c5e6ea6411b96f85e38837f6c))
+
+### Bug Fixes
+
+* add missing kings to gameLoop capture test board ([aedd787](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/aedd787b77203c2af934751dba7b784eaf165032))
+* correct test board positions and captureOutput/withInput interaction ([f0481e2](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/f0481e2561b779df00925b46ee281dc36a795150))
+* update main class path in build configuration and adjust VCS directory mapping ([7b1f8b1](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/7b1f8b117623d327232a1a92a8a44d18582e0189))
+* update move validation to check for king safety ([#13](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/13)) ([e5e20c5](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/e5e20c566e368b12ca1dc59680c34e9112bf6762))
+##  (2026-04-14)
+
+### Features
+
+* add GameRules stub with PositionStatus enum ([76d4168](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/76d4168038de23e5d6083d4e8f0504fbf31d15a3))
+* add MovedInCheck/Checkmate/Stalemate MoveResult variants (stub dispatch) ([8b7ec57](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/8b7ec57e5ea6ee1615a1883848a426dc07d26364))
+* implement GameRules with isInCheck, legalMoves, gameStatus ([94a02ff](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/94a02ff6849436d9496c70a0f16c21666dae8e4e))
+* implement legal castling ([#1](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/1)) ([00d326c](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/00d326c1ba67711fbe180f04e1100c3f01dd0254))
+* NCS-10 Implement Pawn Promotion ([#12](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/12)) ([13bfc16](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/13bfc16cfe25db78ec607db523ca6d993c13430c))
+* NCS-11 50-move rule ([#9](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/9)) ([412ed98](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/412ed986a95703a3b282276540153480ceed229d))
+* NCS-14 implemented insufficient moves rule ([#30](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/30)) ([b0399a4](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/b0399a4e489950083066c9538df9a84dcc7a4613))
+* NCS-16 Core Separation via Patterns ([#10](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/10)) ([1361dfc](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/1361dfc89553b146864fb8ff3526cf12cf3f293a))
+* NCS-17 Implement basic ScalaFX UI ([#14](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/14)) ([3ff8031](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/3ff80318b4f16c59733a46498581a5c27f048287))
+* NCS-21 Write Scripts to automate certain tasks ([#15](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/15)) ([8051871](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/80518719d536a087d339fe02530825dc07f8b388))
+* NCS-25 Add linters to keep quality up ([#27](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/27)) ([fd4e67d](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/fd4e67d4f782a7e955822d90cb909d0a81676fb2))
+* NCS-6 Implementing FEN & PGN ([#7](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/7)) ([f28e69d](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/f28e69dc181416aa2f221fdc4b45c2cda5efbf07))
+* NCS-9 En passant implementation ([#8](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/8)) ([919beb3](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/919beb3b4bfa8caf2f90976a415fe9b19b7e9747))
+* wire check/checkmate/stalemate into processMove and gameLoop ([5264a22](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/5264a225418b885c5e6ea6411b96f85e38837f6c))
+
+### Bug Fixes
+
+* add missing kings to gameLoop capture test board ([aedd787](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/aedd787b77203c2af934751dba7b784eaf165032))
+* correct test board positions and captureOutput/withInput interaction ([f0481e2](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/f0481e2561b779df00925b46ee281dc36a795150))
+* update main class path in build configuration and adjust VCS directory mapping ([7b1f8b1](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/7b1f8b117623d327232a1a92a8a44d18582e0189))
+* update move validation to check for king safety ([#13](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/13)) ([e5e20c5](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/e5e20c566e368b12ca1dc59680c34e9112bf6762))

modules/core/build.gradle.kts

@@ -1,7 +1,6 @@
 plugins {
     id("scala")
     id("org.scoverage") version "8.1"
-    application
 }
 
 group = "de.nowchess"
@@ -22,19 +21,10 @@ scoverage {
     scoverageVersion.set(versions["SCOVERAGE"]!!)
 }
 
-application {
-    mainClass.set("de.nowchess.chess.Main")
-}
-
 tasks.withType<ScalaCompile> {
     scalaCompileOptions.additionalParameters = listOf("-encoding", "UTF-8")
 }
 
-tasks.named<JavaExec>("run") {
-    jvmArgs("-Dfile.encoding=UTF-8", "-Dstdout.encoding=UTF-8", "-Dstderr.encoding=UTF-8")
-    standardInput = System.`in`
-}
-
 dependencies {
 
     implementation("org.scala-lang:scala3-compiler_3") {
@@ -49,6 +39,8 @@ dependencies {
     }
 
     implementation(project(":modules:api"))
+    implementation(project(":modules:io"))
+    implementation(project(":modules:rule"))
 
     testImplementation(platform("org.junit:junit-bom:5.13.4"))
     testImplementation("org.junit.jupiter:junit-jupiter")

modules/core/src/main/scala/de/nowchess/chess/command/Command.scala

@@ -1,11 +1,11 @@
 package de.nowchess.chess.command
 
-import de.nowchess.api.board.{Square, Board, Color, Piece}
-import de.nowchess.chess.logic.GameHistory
+import de.nowchess.api.board.{Piece, Square}
+import de.nowchess.api.game.GameContext
 
-/** Marker trait for all commands that can be executed and undone.
- *  Commands encapsulate user actions and game state transitions.
- */
+/** Marker trait for all commands that can be executed and undone. Commands encapsulate user actions and game state
+  * transitions.
+  */
 trait Command:
   /** Execute the command and return true if successful, false otherwise. */
   def execute(): Boolean
@@ -16,49 +16,45 @@ trait Command:
   /** A human-readable description of this command. */
   def description: String
 
-/** Command to move a piece from one square to another.
- *  Stores the move result so undo can restore previous state.
- */
+/** Command to move a piece from one square to another. Stores the move result so undo can restore previous state.
+  */
 case class MoveCommand(
-  from: Square,
-  to: Square,
-  moveResult: Option[MoveResult] = None,
-  previousBoard: Option[Board] = None,
-  previousHistory: Option[GameHistory] = None,
-  previousTurn: Option[Color] = None
+    from: Square,
+    to: Square,
+    moveResult: Option[MoveResult] = None,
+    previousContext: Option[GameContext] = None,
+    notation: String = "",
 ) extends Command:
 
   override def execute(): Boolean =
     moveResult.isDefined
 
   override def undo(): Boolean =
-    previousBoard.isDefined && previousHistory.isDefined && previousTurn.isDefined
+    previousContext.isDefined
 
   override def description: String = s"Move from $from to $to"
 
 // Sealed hierarchy of move outcomes (for tracking state changes)
 sealed trait MoveResult
 object MoveResult:
-  case class Successful(newBoard: Board, newHistory: GameHistory, newTurn: Color, captured: Option[Piece]) extends MoveResult
-  case object InvalidFormat extends MoveResult
-  case object InvalidMove extends MoveResult
+  case class Successful(newContext: GameContext, captured: Option[Piece]) extends MoveResult
+  case object InvalidFormat                                               extends MoveResult
+  case object InvalidMove                                                 extends MoveResult
 
 /** Command to quit the game. */
 case class QuitCommand() extends Command:
-  override def execute(): Boolean = true
-  override def undo(): Boolean = false
+  override def execute(): Boolean  = true
+  override def undo(): Boolean     = false
   override def description: String = "Quit game"
 
 /** Command to reset the board to initial position. */
 case class ResetCommand(
-  previousBoard: Option[Board] = None,
-  previousHistory: Option[GameHistory] = None,
-  previousTurn: Option[Color] = None
+    previousContext: Option[GameContext] = None,
 ) extends Command:
 
   override def execute(): Boolean = true
 
   override def undo(): Boolean =
-    previousBoard.isDefined && previousHistory.isDefined && previousTurn.isDefined
+    previousContext.isDefined
 
   override def description: String = "Reset board"

modules/core/src/main/scala/de/nowchess/chess/command/CommandInvoker.scala

@@ -3,21 +3,19 @@ package de.nowchess.chess.command
 /** Manages command execution and history for undo/redo support. */
 class CommandInvoker:
   private val executedCommands = scala.collection.mutable.ListBuffer[Command]()
+  @SuppressWarnings(Array("DisableSyntax.var"))
   private var currentIndex = -1
 
-  /** Execute a command and add it to history.
-   *  Discards any redo history if not at the end of the stack.
-   */
+  /** Execute a command and add it to history. Discards any redo history if not at the end of the stack.
+    */
   def execute(command: Command): Boolean = synchronized {
     if command.execute() then
       // Remove any commands after current index (redo stack is discarded)
-      while currentIndex < executedCommands.size - 1 do
-        executedCommands.remove(executedCommands.size - 1)
+      while currentIndex < executedCommands.size - 1 do executedCommands.remove(executedCommands.size - 1)
       executedCommands += command
       currentIndex += 1
       true
-    else
-      false
+    else false
   }
 
   /** Undo the last executed command if possible. */
@@ -27,10 +25,8 @@ class CommandInvoker:
       if command.undo() then
         currentIndex -= 1
         true
-      else
-        false
-    else
-      false
+      else false
+    else false
   }
 
   /** Redo the next command in history if available. */
@@ -40,10 +36,8 @@ class CommandInvoker:
       if command.execute() then
         currentIndex += 1
         true
-      else
-        false
-    else
-      false
+      else false
+    else false
   }
 
   /** Get the history of all executed commands. */

modules/core/src/main/scala/de/nowchess/chess/controller/GameController.scala

@@ -1,106 +0,0 @@
-package de.nowchess.chess.controller
-
-import de.nowchess.api.board.{Board, Color, File, Piece, PieceType, Rank, Square}
-import de.nowchess.api.move.PromotionPiece
-import de.nowchess.chess.logic.*
-
-// ---------------------------------------------------------------------------
-// Result ADT returned by the pure processMove function
-// ---------------------------------------------------------------------------
-
-sealed trait MoveResult
-object MoveResult:
-  case object Quit                                                                       extends MoveResult
-  case class  InvalidFormat(raw: String)                                                extends MoveResult
-  case object NoPiece                                                                   extends MoveResult
-  case object WrongColor                                                                extends MoveResult
-  case object IllegalMove                                                               extends MoveResult
-  case class  PromotionRequired(
-    from: Square,
-    to: Square,
-    boardBefore: Board,
-    historyBefore: GameHistory,
-    captured: Option[Piece],
-    turn: Color
-  ) extends MoveResult
-  case class  Moved(newBoard: Board, newHistory: GameHistory, captured: Option[Piece], newTurn: Color)      extends MoveResult
-  case class  MovedInCheck(newBoard: Board, newHistory: GameHistory, captured: Option[Piece], newTurn: Color) extends MoveResult
-  case class  Checkmate(winner: Color)                                                  extends MoveResult
-  case object Stalemate                                                                 extends MoveResult
-
-// ---------------------------------------------------------------------------
-// Controller
-// ---------------------------------------------------------------------------
-
-object GameController:
-
-  /** Pure function: interprets one raw input line against the current game context.
-   *  Has no I/O side effects — all output must be handled by the caller.
-   */
-  def processMove(board: Board, history: GameHistory, turn: Color, raw: String): MoveResult =
-    raw.trim match
-      case "quit" | "q" => MoveResult.Quit
-      case trimmed =>
-        Parser.parseMove(trimmed) match
-          case None              => MoveResult.InvalidFormat(trimmed)
-          case Some((from, to))  => validateAndApply(board, history, turn, from, to)
-
-  /** Apply a previously detected promotion move with the chosen piece.
-   *  Called after processMove returned PromotionRequired.
-   */
-  def completePromotion(
-    board: Board,
-    history: GameHistory,
-    from: Square,
-    to: Square,
-    piece: PromotionPiece,
-    turn: Color
-  ): MoveResult =
-    val (boardAfterMove, captured) = board.withMove(from, to)
-    val promotedPieceType = piece match
-      case PromotionPiece.Queen  => PieceType.Queen
-      case PromotionPiece.Rook   => PieceType.Rook
-      case PromotionPiece.Bishop => PieceType.Bishop
-      case PromotionPiece.Knight => PieceType.Knight
-    val newBoard    = boardAfterMove.updated(to, Piece(turn, promotedPieceType))
-    // Promotion is always a pawn move → clock resets
-    val newHistory = history.addMove(from, to, None, Some(piece), wasPawnMove = true)
-    toMoveResult(newBoard, newHistory, captured, turn)
-
-  // ---------------------------------------------------------------------------
-  // Private helpers
-  // ---------------------------------------------------------------------------
-
-  private def validateAndApply(board: Board, history: GameHistory, turn: Color, from: Square, to: Square): MoveResult =
-    board.pieceAt(from) match
-      case None                              => MoveResult.NoPiece
-      case Some(piece) if piece.color != turn => MoveResult.WrongColor
-      case Some(_) =>
-        if !GameRules.legalMoves(board, history, turn).contains(from -> to) then MoveResult.IllegalMove
-        else if MoveValidator.isPromotionMove(board, from, to) then
-          MoveResult.PromotionRequired(from, to, board, history, board.pieceAt(to), turn)
-        else applyNormalMove(board, history, turn, from, to)
-
-  private def applyNormalMove(board: Board, history: GameHistory, turn: Color, from: Square, to: Square): MoveResult =
-    val castleOpt              = Option.when(MoveValidator.isCastle(board, from, to))(MoveValidator.castleSide(from, to))
-    val isEP                   = EnPassantCalculator.isEnPassant(board, history, from, to)
-    val (newBoard, captured)   = castleOpt match
-      case Some(side) => (board.withCastle(turn, side), None)
-      case None =>
-        val (b, cap) = board.withMove(from, to)
-        if isEP then
-          val capturedSq = EnPassantCalculator.capturedPawnSquare(to, turn)
-          (b.removed(capturedSq), board.pieceAt(capturedSq))
-        else (b, cap)
-    val pieceType   = board.pieceAt(from).map(_.pieceType).getOrElse(PieceType.Pawn)
-    val wasPawnMove = pieceType == PieceType.Pawn
-    val wasCapture  = captured.isDefined
-    val newHistory  = history.addMove(from, to, castleOpt, wasPawnMove = wasPawnMove, wasCapture = wasCapture, pieceType = pieceType)
-    toMoveResult(newBoard, newHistory, captured, turn)
-
-  private def toMoveResult(newBoard: Board, newHistory: GameHistory, captured: Option[Piece], turn: Color): MoveResult =
-    GameRules.gameStatus(newBoard, newHistory, turn.opposite) match
-      case PositionStatus.Normal  => MoveResult.Moved(newBoard, newHistory, captured, turn.opposite)
-      case PositionStatus.InCheck => MoveResult.MovedInCheck(newBoard, newHistory, captured, turn.opposite)
-      case PositionStatus.Mated   => MoveResult.Checkmate(turn)
-      case PositionStatus.Drawn   => MoveResult.Stalemate

modules/core/src/main/scala/de/nowchess/chess/controller/Parser.scala

@@ -4,21 +4,25 @@ import de.nowchess.api.board.{File, Rank, Square}
 
 object Parser:
 
-  /** Parses coordinate notation such as "e2e4" or "g1f3".
-   *  Returns None for any input that does not match the expected format.
-   */
+  /** Parses coordinate notation such as "e2e4" or "g1f3". Returns None for any input that does not match the expected
+    * format.
+    */
   def parseMove(input: String): Option[(Square, Square)] =
     val trimmed = input.trim.toLowerCase
-    Option.when(trimmed.length == 4)(trimmed).flatMap: s =>
-      for
-        from <- parseSquare(s.substring(0, 2))
-        to   <- parseSquare(s.substring(2, 4))
-      yield (from, to)
+    Option
+      .when(trimmed.length == 4)(trimmed)
+      .flatMap: s =>
+        for
+          from <- parseSquare(s.substring(0, 2))
+          to   <- parseSquare(s.substring(2, 4))
+        yield (from, to)
 
   private def parseSquare(s: String): Option[Square] =
-    Option.when(s.length == 2)(s).flatMap: sq =>
-      val fileIdx = sq(0) - 'a'
-      val rankIdx = sq(1) - '1'
-      Option.when(fileIdx >= 0 && fileIdx <= 7 && rankIdx >= 0 && rankIdx <= 7)(
-        Square(File.values(fileIdx), Rank.values(rankIdx))
-      )
+    Option
+      .when(s.length == 2)(s)
+      .flatMap: sq =>
+        val fileIdx = sq(0) - 'a'
+        val rankIdx = sq(1) - '1'
+        Option.when(fileIdx >= 0 && fileIdx <= 7 && rankIdx >= 0 && rankIdx <= 7)(
+          Square(File.values(fileIdx), Rank.values(rankIdx)),
+        )

modules/core/src/main/scala/de/nowchess/chess/engine/GameEngine.scala

@@ -1,65 +1,60 @@
 package de.nowchess.chess.engine
 
-import de.nowchess.api.board.{Board, Color, Piece, Square}
-import de.nowchess.api.move.PromotionPiece
-import de.nowchess.chess.logic.{GameHistory, GameRules, PositionStatus}
-import de.nowchess.chess.controller.{GameController, Parser, MoveResult}
+import de.nowchess.api.board.{Board, Color, Piece, PieceType, Square}
+import de.nowchess.api.move.{Move, MoveType, PromotionPiece}
+import de.nowchess.api.game.{DrawReason, GameContext, GameResult}
+import de.nowchess.chess.controller.Parser
 import de.nowchess.chess.observer.*
-import de.nowchess.chess.command.{CommandInvoker, MoveCommand}
-import de.nowchess.chess.notation.{PgnExporter, PgnParser}
+import de.nowchess.chess.command.{CommandInvoker, MoveCommand, MoveResult}
+import de.nowchess.io.{GameContextExport, GameContextImport}
+import de.nowchess.rules.RuleSet
+import de.nowchess.rules.sets.DefaultRules
 
-/** Pure game engine that manages game state and notifies observers of state changes.
- *  This class is the single source of truth for the game state.
- *  All user interactions must go through this engine via Commands, and all state changes
- *  are communicated to observers via GameEvent notifications.
- */
+/** Pure game engine that manages game state and notifies observers of state changes. All rule queries delegate to the
+  * injected RuleSet. All user interactions go through Commands; state changes are broadcast via GameEvents.
+  */
 class GameEngine(
-  initialBoard: Board = Board.initial,
-  initialHistory: GameHistory = GameHistory.empty,
-  initialTurn: Color = Color.White,
-  completePromotionFn: (Board, GameHistory, Square, Square, PromotionPiece, Color) => MoveResult =
-    GameController.completePromotion
+    val initialContext: GameContext = GameContext.initial,
+    val ruleSet: RuleSet = DefaultRules,
 ) extends Observable:
-  private var currentBoard: Board = initialBoard
-  private var currentHistory: GameHistory = initialHistory
-  private var currentTurn: Color = initialTurn
-  private val invoker = new CommandInvoker()
+  // Ensure that initialBoard is set correctly for threefold repetition detection
+  private val contextWithInitialBoard = if initialContext.moves.isEmpty && initialContext.board != initialContext.initialBoard then
+    initialContext.copy(initialBoard = initialContext.board)
+  else
+    initialContext
+  @SuppressWarnings(Array("DisableSyntax.var"))
+  private var currentContext: GameContext = contextWithInitialBoard
+  private val invoker                     = new CommandInvoker()
 
-  /** Inner class for tracking pending promotion state */
-  private case class PendingPromotion(
-    from: Square, to: Square,
-    boardBefore: Board, historyBefore: GameHistory,
-    turn: Color
-  )
-
-  /** Current pending promotion, if any */
+  /** Pending promotion: the Move that triggered it (from/to only, moveType filled in later). */
+  private case class PendingPromotion(from: Square, to: Square, contextBefore: GameContext)
+  @SuppressWarnings(Array("DisableSyntax.var"))
   private var pendingPromotion: Option[PendingPromotion] = None
 
   /** True if a pawn promotion move is pending and needs a piece choice. */
-  def isPendingPromotion: Boolean = synchronized { pendingPromotion.isDefined }
+  def isPendingPromotion: Boolean = synchronized(pendingPromotion.isDefined)
 
   // Synchronized accessors for current state
-  def board: Board = synchronized { currentBoard }
-  def history: GameHistory = synchronized { currentHistory }
-  def turn: Color = synchronized { currentTurn }
+  def board: Board         = synchronized(currentContext.board)
+  def turn: Color          = synchronized(currentContext.turn)
+  def context: GameContext = synchronized(currentContext)
 
   /** Check if undo is available. */
-  def canUndo: Boolean = synchronized { invoker.canUndo }
+  def canUndo: Boolean = synchronized(invoker.canUndo)
 
   /** Check if redo is available. */
-  def canRedo: Boolean = synchronized { invoker.canRedo }
+  def canRedo: Boolean = synchronized(invoker.canRedo)
 
   /** Get the command history for inspection (testing/debugging). */
-  def commandHistory: List[de.nowchess.chess.command.Command] = synchronized { invoker.history }
+  def commandHistory: List[de.nowchess.chess.command.Command] = synchronized(invoker.history)
 
-  /** Process a raw move input string and update game state if valid.
-   *  Notifies all observers of the outcome via GameEvent.
-   */
+  /** Process a raw move input string and update game state if valid. Notifies all observers of the outcome via
+    * GameEvent.
+    */
   def processUserInput(rawInput: String): Unit = synchronized {
     val trimmed = rawInput.trim.toLowerCase
     trimmed match
       case "quit" | "q" =>
-        // Client should handle quit logic; we just return
         ()
 
       case "undo" =>
@@ -69,284 +64,269 @@ class GameEngine(
         performRedo()
 
       case "draw" =>
-        if currentHistory.halfMoveClock >= 100 then
-          currentBoard   = Board.initial
-          currentHistory = GameHistory.empty
-          currentTurn    = Color.White
+        if currentContext.halfMoveClock >= 100 then
+          currentContext = currentContext.withResult(Some(GameResult.Draw(DrawReason.FiftyMoveRule)))
           invoker.clear()
-          notifyObservers(DrawClaimedEvent(currentBoard, currentHistory, currentTurn))
+          notifyObservers(DrawEvent(currentContext, DrawReason.FiftyMoveRule))
+        else if ruleSet.isThreefoldRepetition(currentContext) then
+          currentContext = currentContext.withResult(Some(GameResult.Draw(DrawReason.ThreefoldRepetition)))
+          invoker.clear()
+          notifyObservers(DrawEvent(currentContext, DrawReason.ThreefoldRepetition))
         else
-          notifyObservers(InvalidMoveEvent(
-            currentBoard, currentHistory, currentTurn,
-            "Draw cannot be claimed: the 50-move rule has not been triggered."
-          ))
+          notifyObservers(
+            InvalidMoveEvent(
+              currentContext,
+              "Draw cannot be claimed: neither the 50-move rule nor threefold repetition has been triggered.",
+            ),
+          )
 
       case "" =>
-        val event = InvalidMoveEvent(
-          currentBoard,
-          currentHistory,
-          currentTurn,
-          "Please enter a valid move or command."
-        )
-        notifyObservers(event)
+        notifyObservers(InvalidMoveEvent(currentContext, "Please enter a valid move or command."))
 
       case moveInput =>
         Parser.parseMove(moveInput) match
           case None =>
-            notifyObservers(InvalidMoveEvent(
-              currentBoard, currentHistory, currentTurn,
-              s"Invalid move format '$moveInput'. Use coordinate notation, e.g. e2e4."
-            ))
+            notifyObservers(
+              InvalidMoveEvent(
+                currentContext,
+                s"Invalid move format '$moveInput'. Use coordinate notation, e.g. e2e4.",
+              ),
+            )
           case Some((from, to)) =>
-            handleParsedMove(from, to, moveInput)
+            handleParsedMove(from, to)
   }
 
-  private def handleParsedMove(from: Square, to: Square, moveInput: String): Unit =
-    val cmd = MoveCommand(
-      from = from,
-      to = to,
-      previousBoard = Some(currentBoard),
-      previousHistory = Some(currentHistory),
-      previousTurn = Some(currentTurn)
-    )
-    GameController.processMove(currentBoard, currentHistory, currentTurn, moveInput) match
-      case MoveResult.InvalidFormat(_) | MoveResult.NoPiece | MoveResult.WrongColor | MoveResult.IllegalMove | MoveResult.Quit =>
-        handleFailedMove(moveInput)
+  private def handleParsedMove(from: Square, to: Square): Unit =
+    currentContext.board.pieceAt(from) match
+      case None =>
+        notifyObservers(InvalidMoveEvent(currentContext, "No piece on that square."))
+      case Some(piece) if piece.color != currentContext.turn =>
+        notifyObservers(InvalidMoveEvent(currentContext, "That is not your piece."))
+      case Some(piece) =>
+        val legal = ruleSet.legalMoves(currentContext)(from)
+        // Find all legal moves going to `to`
+        val candidates = legal.filter(_.to == to)
+        candidates match
+          case Nil =>
+            notifyObservers(InvalidMoveEvent(currentContext, "Illegal move."))
+          case moves if isPromotionMove(piece, to) =>
+            // Multiple moves (one per promotion piece) — ask user to choose
+            val contextBefore = currentContext
+            pendingPromotion = Some(PendingPromotion(from, to, contextBefore))
+            notifyObservers(PromotionRequiredEvent(currentContext, from, to))
+          case move :: _ =>
+            executeMove(move)
 
-      case MoveResult.Moved(newBoard, newHistory, captured, newTurn) =>
-        val updatedCmd = cmd.copy(moveResult = Some(de.nowchess.chess.command.MoveResult.Successful(newBoard, newHistory, newTurn, captured)))
-        invoker.execute(updatedCmd)
-        updateGameState(newBoard, newHistory, newTurn)
-        emitMoveEvent(from.toString, to.toString, captured, newTurn)
-        if currentHistory.halfMoveClock >= 100 then
-          notifyObservers(FiftyMoveRuleAvailableEvent(currentBoard, currentHistory, currentTurn))
+  private def isPromotionMove(piece: Piece, to: Square): Boolean =
+    piece.pieceType == PieceType.Pawn && {
+      val promoRank = if piece.color == Color.White then 7 else 0
+      to.rank.ordinal == promoRank
+    }
 
-      case MoveResult.MovedInCheck(newBoard, newHistory, captured, newTurn) =>
-        val updatedCmd = cmd.copy(moveResult = Some(de.nowchess.chess.command.MoveResult.Successful(newBoard, newHistory, newTurn, captured)))
-        invoker.execute(updatedCmd)
-        updateGameState(newBoard, newHistory, newTurn)
-        emitMoveEvent(from.toString, to.toString, captured, newTurn)
-        notifyObservers(CheckDetectedEvent(currentBoard, currentHistory, currentTurn))
-        if currentHistory.halfMoveClock >= 100 then
-          notifyObservers(FiftyMoveRuleAvailableEvent(currentBoard, currentHistory, currentTurn))
-
-      case MoveResult.Checkmate(winner) =>
-        val updatedCmd = cmd.copy(moveResult = Some(de.nowchess.chess.command.MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)))
-        invoker.execute(updatedCmd)
-        currentBoard = Board.initial
-        currentHistory = GameHistory.empty
-        currentTurn = Color.White
-        notifyObservers(CheckmateEvent(currentBoard, currentHistory, currentTurn, winner))
-
-      case MoveResult.Stalemate =>
-        val updatedCmd = cmd.copy(moveResult = Some(de.nowchess.chess.command.MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)))
-        invoker.execute(updatedCmd)
-        currentBoard = Board.initial
-        currentHistory = GameHistory.empty
-        currentTurn = Color.White
-        notifyObservers(StalemateEvent(currentBoard, currentHistory, currentTurn))
-
-      case MoveResult.PromotionRequired(promFrom, promTo, boardBefore, histBefore, _, promotingTurn) =>
-        pendingPromotion = Some(PendingPromotion(promFrom, promTo, boardBefore, histBefore, promotingTurn))
-        notifyObservers(PromotionRequiredEvent(currentBoard, currentHistory, currentTurn, promFrom, promTo))
-
-  /** Undo the last move. */
-  def undo(): Unit = synchronized {
-    performUndo()
-  }
-
-  /** Redo the last undone move. */
-  def redo(): Unit = synchronized {
-    performRedo()
-  }
-
-  /** Apply a player's promotion piece choice.
-   *  Must only be called when isPendingPromotion is true.
-   */
+  /** Apply a player's promotion piece choice. Must only be called when isPendingPromotion is true.
+    */
   def completePromotion(piece: PromotionPiece): Unit = synchronized {
     pendingPromotion match
       case None =>
-        notifyObservers(InvalidMoveEvent(currentBoard, currentHistory, currentTurn, "No promotion pending."))
+        notifyObservers(InvalidMoveEvent(currentContext, "No promotion pending."))
       case Some(pending) =>
         pendingPromotion = None
-        val cmd = MoveCommand(
-          from = pending.from,
-          to = pending.to,
-          previousBoard = Some(pending.boardBefore),
-          previousHistory = Some(pending.historyBefore),
-          previousTurn = Some(pending.turn)
-        )
-        completePromotionFn(
-          pending.boardBefore, pending.historyBefore,
-          pending.from, pending.to, piece, pending.turn
-        ) match
-          case MoveResult.Moved(newBoard, newHistory, captured, newTurn) =>
-            val updatedCmd = cmd.copy(moveResult = Some(de.nowchess.chess.command.MoveResult.Successful(newBoard, newHistory, newTurn, captured)))
-            invoker.execute(updatedCmd)
-            updateGameState(newBoard, newHistory, newTurn)
-            emitMoveEvent(pending.from.toString, pending.to.toString, captured, newTurn)
-
-          case MoveResult.MovedInCheck(newBoard, newHistory, captured, newTurn) =>
-            val updatedCmd = cmd.copy(moveResult = Some(de.nowchess.chess.command.MoveResult.Successful(newBoard, newHistory, newTurn, captured)))
-            invoker.execute(updatedCmd)
-            updateGameState(newBoard, newHistory, newTurn)
-            emitMoveEvent(pending.from.toString, pending.to.toString, captured, newTurn)
-            notifyObservers(CheckDetectedEvent(currentBoard, currentHistory, currentTurn))
-
-          case MoveResult.Checkmate(winner) =>
-            val updatedCmd = cmd.copy(moveResult = Some(de.nowchess.chess.command.MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)))
-            invoker.execute(updatedCmd)
-            currentBoard = Board.initial
-            currentHistory = GameHistory.empty
-            currentTurn = Color.White
-            notifyObservers(CheckmateEvent(currentBoard, currentHistory, currentTurn, winner))
-
-          case MoveResult.Stalemate =>
-            val updatedCmd = cmd.copy(moveResult = Some(de.nowchess.chess.command.MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)))
-            invoker.execute(updatedCmd)
-            currentBoard = Board.initial
-            currentHistory = GameHistory.empty
-            currentTurn = Color.White
-            notifyObservers(StalemateEvent(currentBoard, currentHistory, currentTurn))
-
-          case _ =>
-            notifyObservers(InvalidMoveEvent(currentBoard, currentHistory, currentTurn, "Error completing promotion."))
+        val move = Move(pending.from, pending.to, MoveType.Promotion(piece))
+        // Verify it's actually legal
+        val legal = ruleSet.legalMoves(currentContext)(pending.from)
+        if legal.contains(move) then executeMove(move)
+        else notifyObservers(InvalidMoveEvent(currentContext, "Error completing promotion."))
   }
 
-  /** Validate and load a PGN string.
-   *  Each move is replayed through the command system so undo/redo is available after loading.
-   *  Returns Right(()) on success; Left(error) if any move is illegal or the position impossible. */
-  def loadPgn(pgn: String): Either[String, Unit] = synchronized {
-    PgnParser.validatePgn(pgn) match
-      case Left(err) =>
-        Left(err)
-      case Right(game) =>
-        val initialBoardBeforeLoad = currentBoard
-        val initialHistoryBeforeLoad = currentHistory
-        val initialTurnBeforeLoad = currentTurn
-        
-        currentBoard = Board.initial
-        currentHistory = GameHistory.empty
-        currentTurn = Color.White
-        pendingPromotion = None
-        invoker.clear()
+  /** Undo the last move. */
+  def undo(): Unit = synchronized(performUndo())
 
-        var error: Option[String] = None
-        import scala.util.control.Breaks._
-        breakable {
-          game.moves.foreach { move =>
-            handleParsedMove(move.from, move.to, s"${move.from}${move.to}")
-            move.promotionPiece.foreach(completePromotion)
-            
-            // If the move failed to execute properly, stop and report
-            // (validatePgn should have caught this, but we're being safe)
-            if pendingPromotion.isDefined && move.promotionPiece.isEmpty then
-              error = Some(s"Promotion required for move ${move.from}${move.to}")
-              break()
-          }
+  /** Redo the last undone move. */
+  def redo(): Unit = synchronized(performRedo())
+
+  /** Load a game using the provided importer. If the imported context has moves, they are replayed through the command
+    * system. Otherwise, the position is set directly. Notifies observers with PgnLoadedEvent on success.
+    */
+  def loadGame(importer: GameContextImport, input: String): Either[String, Unit] = synchronized {
+    importer.importGameContext(input) match
+      case Left(err) => Left(err)
+      case Right(ctx) =>
+        replayGame(ctx).map { _ =>
+          notifyObservers(PgnLoadedEvent(currentContext))
         }
-        
-        error match
-          case Some(err) =>
-            currentBoard = initialBoardBeforeLoad
-            currentHistory = initialHistoryBeforeLoad
-            currentTurn = initialTurnBeforeLoad
-            Left(err)
-          case None =>
-            notifyObservers(PgnLoadedEvent(currentBoard, currentHistory, currentTurn))
-            Right(())
+  }
+
+  private def replayGame(ctx: GameContext): Either[String, Unit] =
+    val savedContext = currentContext
+    currentContext = GameContext.initial
+    pendingPromotion = None
+    invoker.clear()
+
+    if ctx.moves.isEmpty then
+      currentContext = ctx.copy(initialBoard = ctx.board)
+      Right(())
+    else replayMoves(ctx.moves, savedContext)
+
+  private[engine] def replayMoves(moves: List[Move], savedContext: GameContext): Either[String, Unit] =
+    val result = moves.foldLeft[Either[String, Unit]](Right(())) { (acc, move) =>
+      acc.flatMap(_ => applyReplayMove(move))
+    }
+    result.left.foreach(_ => currentContext = savedContext)
+    result
+
+  private def applyReplayMove(move: Move): Either[String, Unit] =
+    handleParsedMove(move.from, move.to)
+    move.moveType match
+      case MoveType.Promotion(pp) if pendingPromotion.isDefined =>
+        completePromotion(pp)
+        Right(())
+      case MoveType.Promotion(_) =>
+        Left(s"Promotion required for move ${move.from}${move.to}")
+      case _ => Right(())
+
+  /** Export the current game context using the provided exporter. */
+  def exportGame(exporter: GameContextExport): String = synchronized {
+    exporter.exportGameContext(currentContext)
   }
 
   /** Load an arbitrary board position, clearing all history and undo/redo state. */
-  def loadPosition(board: Board, history: GameHistory, turn: Color): Unit = synchronized {
-    currentBoard = board
-    currentHistory = history
-    currentTurn = turn
+  def loadPosition(newContext: GameContext): Unit = synchronized {
+    val contextWithInitialBoard = if newContext.moves.isEmpty then
+      newContext.copy(initialBoard = newContext.board)
+    else
+      newContext
+    currentContext = contextWithInitialBoard
     pendingPromotion = None
     invoker.clear()
-    notifyObservers(BoardResetEvent(currentBoard, currentHistory, currentTurn))
+    notifyObservers(BoardResetEvent(currentContext))
   }
 
   /** Reset the board to initial position. */
   def reset(): Unit = synchronized {
-    currentBoard = Board.initial
-    currentHistory = GameHistory.empty
-    currentTurn = Color.White
+    currentContext = GameContext.initial
     invoker.clear()
-    notifyObservers(BoardResetEvent(
-      currentBoard,
-      currentHistory,
-      currentTurn
-    ))
+    notifyObservers(BoardResetEvent(currentContext))
   }
 
-  // ──── Private Helpers ────
+  // ──── Private helpers ────
+
+  private def executeMove(move: Move): Unit =
+    val contextBefore = currentContext
+    val nextContext   = ruleSet.applyMove(currentContext)(move)
+    val captured      = computeCaptured(currentContext, move)
+
+    val cmd = MoveCommand(
+      from = move.from,
+      to = move.to,
+      moveResult = Some(MoveResult.Successful(nextContext, captured)),
+      previousContext = Some(contextBefore),
+      notation = translateMoveToNotation(move, contextBefore.board),
+    )
+    invoker.execute(cmd)
+    currentContext = nextContext
+
+    notifyObservers(
+      MoveExecutedEvent(
+        currentContext,
+        move.from.toString,
+        move.to.toString,
+        captured.map(c => s"${c.color.label} ${c.pieceType.label}"),
+      ),
+    )
+
+    if ruleSet.isCheckmate(currentContext) then
+      val winner = currentContext.turn.opposite
+      currentContext = currentContext.withResult(Some(GameResult.Win(winner)))
+      notifyObservers(CheckmateEvent(currentContext, winner))
+      invoker.clear()
+    else if ruleSet.isStalemate(currentContext) then
+      currentContext = currentContext.withResult(Some(GameResult.Draw(DrawReason.Stalemate)))
+      notifyObservers(DrawEvent(currentContext, DrawReason.Stalemate))
+      invoker.clear()
+    else if ruleSet.isInsufficientMaterial(currentContext) then
+      currentContext = currentContext.withResult(Some(GameResult.Draw(DrawReason.InsufficientMaterial)))
+      notifyObservers(DrawEvent(currentContext, DrawReason.InsufficientMaterial))
+      invoker.clear()
+    else if ruleSet.isCheck(currentContext) then notifyObservers(CheckDetectedEvent(currentContext))
+
+    if currentContext.halfMoveClock >= 100 then notifyObservers(FiftyMoveRuleAvailableEvent(currentContext))
+    if ruleSet.isThreefoldRepetition(currentContext) then notifyObservers(ThreefoldRepetitionAvailableEvent(currentContext))
+
+  private def translateMoveToNotation(move: Move, boardBefore: Board): String =
+    move.moveType match
+      case MoveType.CastleKingside    => "O-O"
+      case MoveType.CastleQueenside   => "O-O-O"
+      case MoveType.EnPassant         => enPassantNotation(move)
+      case MoveType.Promotion(pp)     => promotionNotation(move, pp)
+      case MoveType.Normal(isCapture) => normalMoveNotation(move, boardBefore, isCapture)
+
+  private def enPassantNotation(move: Move): String =
+    s"${move.from.file.toString.toLowerCase}x${move.to}"
+
+  private def promotionNotation(move: Move, piece: PromotionPiece): String =
+    val ppChar = piece match
+      case PromotionPiece.Queen  => "Q"
+      case PromotionPiece.Rook   => "R"
+      case PromotionPiece.Bishop => "B"
+      case PromotionPiece.Knight => "N"
+    s"${move.to}=$ppChar"
+
+  private[engine] def normalMoveNotation(move: Move, boardBefore: Board, isCapture: Boolean): String =
+    boardBefore.pieceAt(move.from).map(_.pieceType) match
+      case Some(PieceType.Pawn) =>
+        if isCapture then s"${move.from.file.toString.toLowerCase}x${move.to}"
+        else move.to.toString
+      case Some(pt) =>
+        val letter = pieceNotation(pt)
+        if isCapture then s"${letter}x${move.to}" else s"$letter${move.to}"
+      case None => move.to.toString
+
+  private[engine] def pieceNotation(pieceType: PieceType): String =
+    pieceType match
+      case PieceType.Knight => "N"
+      case PieceType.Bishop => "B"
+      case PieceType.Rook   => "R"
+      case PieceType.Queen  => "Q"
+      case PieceType.King   => "K"
+      case _                => ""
+
+  private def computeCaptured(context: GameContext, move: Move): Option[Piece] =
+    move.moveType match
+      case MoveType.EnPassant =>
+        // Captured pawn is on the same rank as the moving pawn, same file as destination
+        val capturedSquare = Square(move.to.file, move.from.rank)
+        context.board.pieceAt(capturedSquare)
+      case MoveType.CastleKingside | MoveType.CastleQueenside =>
+        None
+      case _ =>
+        context.board.pieceAt(move.to)
 
   private def performUndo(): Unit =
     if invoker.canUndo then
       val cmd = invoker.history(invoker.getCurrentIndex)
       (cmd: @unchecked) match
         case moveCmd: MoveCommand =>
-          val notation = currentHistory.moves.lastOption.map(PgnExporter.moveToAlgebraic).getOrElse("")
-          moveCmd.previousBoard.foreach(currentBoard = _)
-          moveCmd.previousHistory.foreach(currentHistory = _)
-          moveCmd.previousTurn.foreach(currentTurn = _)
+          moveCmd.previousContext.foreach(currentContext = _)
           invoker.undo()
-          notifyObservers(MoveUndoneEvent(currentBoard, currentHistory, currentTurn, notation))
-    else
-      notifyObservers(InvalidMoveEvent(currentBoard, currentHistory, currentTurn, "Nothing to undo."))
+          notifyObservers(MoveUndoneEvent(currentContext, moveCmd.notation))
+    else notifyObservers(InvalidMoveEvent(currentContext, "Nothing to undo."))
 
   private def performRedo(): Unit =
     if invoker.canRedo then
       val cmd = invoker.history(invoker.getCurrentIndex + 1)
       (cmd: @unchecked) match
         case moveCmd: MoveCommand =>
-          for case de.nowchess.chess.command.MoveResult.Successful(nb, nh, nt, cap) <- moveCmd.moveResult do
-            updateGameState(nb, nh, nt)
+          for case MoveResult.Successful(nextCtx, cap) <- moveCmd.moveResult do
+            currentContext = nextCtx
             invoker.redo()
-            val notation    = nh.moves.lastOption.map(PgnExporter.moveToAlgebraic).getOrElse("")
             val capturedDesc = cap.map(c => s"${c.color.label} ${c.pieceType.label}")
-            notifyObservers(MoveRedoneEvent(currentBoard, currentHistory, currentTurn, notation, moveCmd.from.toString, moveCmd.to.toString, capturedDesc))
-    else
-      notifyObservers(InvalidMoveEvent(currentBoard, currentHistory, currentTurn, "Nothing to redo."))
-
-  private def updateGameState(newBoard: Board, newHistory: GameHistory, newTurn: Color): Unit =
-    currentBoard = newBoard
-    currentHistory = newHistory
-    currentTurn = newTurn
-
-  private def emitMoveEvent(fromSq: String, toSq: String, captured: Option[Piece], newTurn: Color): Unit =
-    val capturedDesc = captured.map(c => s"${c.color.label} ${c.pieceType.label}")
-    notifyObservers(MoveExecutedEvent(
-      currentBoard,
-      currentHistory,
-      newTurn,
-      fromSq,
-      toSq,
-      capturedDesc
-    ))
-
-  private def handleFailedMove(moveInput: String): Unit =
-    (GameController.processMove(currentBoard, currentHistory, currentTurn, moveInput): @unchecked) match
-      case MoveResult.NoPiece =>
-        notifyObservers(InvalidMoveEvent(
-          currentBoard,
-          currentHistory,
-          currentTurn,
-          "No piece on that square."
-        ))
-      case MoveResult.WrongColor =>
-        notifyObservers(InvalidMoveEvent(
-          currentBoard,
-          currentHistory,
-          currentTurn,
-          "That is not your piece."
-        ))
-      case MoveResult.IllegalMove =>
-        notifyObservers(InvalidMoveEvent(
-          currentBoard,
-          currentHistory,
-          currentTurn,
-          "Illegal move."
-        ))
-
+            notifyObservers(
+              MoveRedoneEvent(
+                currentContext,
+                moveCmd.notation,
+                moveCmd.from.toString,
+                moveCmd.to.toString,
+                capturedDesc,
+              ),
+            )
+    else notifyObservers(InvalidMoveEvent(currentContext, "Nothing to redo."))

modules/core/src/main/scala/de/nowchess/chess/logic/CastleSide.scala

@@ -1,23 +0,0 @@
-package de.nowchess.chess.logic
-
-import de.nowchess.api.board.*
-
-enum CastleSide:
-  case Kingside, Queenside
-
-extension (b: Board)
-  def withCastle(color: Color, side: CastleSide): Board =
-    val rank = if color == Color.White then Rank.R1 else Rank.R8
-    val kingFrom = Square(File.E, rank)
-    val (kingTo, rookFrom, rookTo) = side match
-      case CastleSide.Kingside =>
-        (Square(File.G, rank), Square(File.H, rank), Square(File.F, rank))
-      case CastleSide.Queenside =>
-        (Square(File.C, rank), Square(File.A, rank), Square(File.D, rank))
-
-    val king = b.pieceAt(kingFrom).get
-    val rook = b.pieceAt(rookFrom).get
-
-    b.removed(kingFrom).removed(rookFrom)
-      .updated(kingTo, king)
-      .updated(rookTo, rook)

modules/core/src/main/scala/de/nowchess/chess/logic/CastlingRightsCalculator.scala

@@ -1,31 +0,0 @@
-package de.nowchess.chess.logic
-
-import de.nowchess.api.board.{Color, File, Rank, Square}
-import de.nowchess.api.game.CastlingRights
-
-/** Derives castling rights from move history. */
-object CastlingRightsCalculator:
-
-  def deriveCastlingRights(history: GameHistory, color: Color): CastlingRights =
-    val (kingRow, kingsideRookFile, queensideRookFile) = color match
-      case Color.White => (Rank.R1, File.H, File.A)
-      case Color.Black => (Rank.R8, File.H, File.A)
-
-    // Check if king has moved
-    val kingHasMoved = history.moves.exists: move =>
-      move.from == Square(File.E, kingRow) || move.castleSide.isDefined
-
-    if kingHasMoved then
-      CastlingRights.None
-    else
-      // Check if kingside rook has moved or was captured
-      val kingsideLost = history.moves.exists: move =>
-        move.from == Square(kingsideRookFile, kingRow) ||
-        move.to == Square(kingsideRookFile, kingRow)
-
-      // Check if queenside rook has moved or was captured
-      val queensideLost = history.moves.exists: move =>
-        move.from == Square(queensideRookFile, kingRow) ||
-        move.to == Square(queensideRookFile, kingRow)
-
-      CastlingRights(kingSide = !kingsideLost, queenSide = !queensideLost)

modules/core/src/main/scala/de/nowchess/chess/logic/EnPassantCalculator.scala

@@ -1,32 +0,0 @@
-package de.nowchess.chess.logic
-
-import de.nowchess.api.board.*
-
-object EnPassantCalculator:
-
-  /** Returns the en passant target square if the last move was a double pawn push.
-   *  The target is the square the pawn passed through (e.g. e2→e4 yields e3).
-   */
-  def enPassantTarget(board: Board, history: GameHistory): Option[Square] =
-    history.moves.lastOption.flatMap: move =>
-      val rankDiff = move.to.rank.ordinal - move.from.rank.ordinal
-      val isDoublePush = math.abs(rankDiff) == 2
-      val isPawn = board.pieceAt(move.to).exists(_.pieceType == PieceType.Pawn)
-      if isDoublePush && isPawn then
-        val midRankIdx = move.from.rank.ordinal + rankDiff / 2
-        Some(Square(move.to.file, Rank.values(midRankIdx)))
-      else None
-
-  /** True if moving from→to is an en passant capture. */
-  def isEnPassant(board: Board, history: GameHistory, from: Square, to: Square): Boolean =
-    board.pieceAt(from).exists(_.pieceType == PieceType.Pawn) &&
-    enPassantTarget(board, history).contains(to) &&
-    math.abs(to.file.ordinal - from.file.ordinal) == 1
-
-  /** Returns the square of the pawn to remove when an en passant capture lands on `to`.
-   *  White captures upward → captured pawn is one rank below `to`.
-   *  Black captures downward → captured pawn is one rank above `to`.
-   */
-  def capturedPawnSquare(to: Square, color: Color): Square =
-    val capturedRankIdx = to.rank.ordinal + (if color == Color.White then -1 else 1)
-    Square(to.file, Rank.values(capturedRankIdx))

modules/core/src/main/scala/de/nowchess/chess/logic/GameHistory.scala

@@ -1,49 +0,0 @@
-package de.nowchess.chess.logic
-
-import de.nowchess.api.board.{PieceType, Square}
-import de.nowchess.api.move.PromotionPiece
-
-/** A single move recorded in the game history. Distinct from api.move.Move which represents user intent. */
-case class HistoryMove(
-  from: Square,
-  to: Square,
-  castleSide: Option[CastleSide],
-  promotionPiece: Option[PromotionPiece] = None,
-  pieceType: PieceType = PieceType.Pawn,
-  isCapture: Boolean = false
-)
-
-/** Complete game history: ordered list of moves plus the half-move clock for the 50-move rule.
- *
- *  @param moves         moves played so far, oldest first
- *  @param halfMoveClock plies since the last pawn move or capture (FIDE 50-move rule counter)
- */
-case class GameHistory(moves: List[HistoryMove] = List.empty, halfMoveClock: Int = 0):
-
-  /** Add a raw HistoryMove record. Clock increments by 1.
-   *  Use the coordinate overload when you know whether the move is a pawn move or capture.
-   */
-  def addMove(move: HistoryMove): GameHistory =
-    GameHistory(moves :+ move, halfMoveClock + 1)
-
-  /** Add a move by coordinates.
-   *
-   *  @param wasPawnMove true when the moving piece is a pawn — resets the clock to 0
-   *  @param wasCapture  true when a piece was captured (including en passant) — resets the clock to 0
-   *
-   *  If neither flag is set the clock increments by 1.
-   */
-  def addMove(
-    from: Square,
-    to: Square,
-    castleSide: Option[CastleSide] = None,
-    promotionPiece: Option[PromotionPiece] = None,
-    wasPawnMove: Boolean = false,
-    wasCapture: Boolean = false,
-    pieceType: PieceType = PieceType.Pawn
-  ): GameHistory =
-    val newClock = if wasPawnMove || wasCapture then 0 else halfMoveClock + 1
-    GameHistory(moves :+ HistoryMove(from, to, castleSide, promotionPiece, pieceType, wasCapture), newClock)
-
-object GameHistory:
-  val empty: GameHistory = GameHistory()

modules/core/src/main/scala/de/nowchess/chess/logic/GameRules.scala

@@ -1,47 +0,0 @@
-package de.nowchess.chess.logic
-
-import de.nowchess.api.board.*
-import de.nowchess.chess.logic.GameHistory
-
-enum PositionStatus:
-  case Normal, InCheck, Mated, Drawn
-
-object GameRules:
-
-  /** True if `color`'s king is under attack on this board. */
-  def isInCheck(board: Board, color: Color): Boolean =
-    board.pieces
-      .collectFirst { case (sq, p) if p.color == color && p.pieceType == PieceType.King => sq }
-      .exists { kingSq =>
-        board.pieces.exists { case (sq, piece) =>
-          piece.color != color &&
-          MoveValidator.legalTargets(board, sq).contains(kingSq)
-        }
-      }
-
-  /** All (from, to) moves for `color` that do not leave their own king in check. */
-  def legalMoves(board: Board, history: GameHistory, color: Color): Set[(Square, Square)] =
-    board.pieces
-      .collect { case (from, piece) if piece.color == color => from }
-      .flatMap { from =>
-        MoveValidator.legalTargets(board, history, from)           // context-aware: includes castling
-          .filter { to =>
-            val newBoard =
-              if MoveValidator.isCastle(board, from, to) then
-                board.withCastle(color, MoveValidator.castleSide(from, to))
-              else
-                board.withMove(from, to)._1
-            !isInCheck(newBoard, color)
-          }
-          .map(to => from -> to)
-      }
-      .toSet
-
-  /** Position status for the side whose turn it is (`color`). */
-  def gameStatus(board: Board, history: GameHistory, color: Color): PositionStatus =
-    val moves   = legalMoves(board, history, color)
-    val inCheck = isInCheck(board, color)
-    if moves.isEmpty && inCheck then PositionStatus.Mated
-    else if moves.isEmpty       then PositionStatus.Drawn
-    else if inCheck             then PositionStatus.InCheck
-    else                             PositionStatus.Normal

modules/core/src/main/scala/de/nowchess/chess/logic/MoveValidator.scala

@@ -1,183 +0,0 @@
-package de.nowchess.chess.logic
-
-import de.nowchess.api.board.*
-import de.nowchess.chess.logic.{CastleSide, GameHistory}
-
-object MoveValidator:
-
-  /** Returns true if the move is geometrically legal for the piece on `from`,
-   *  ignoring check/pin but respecting:
-   *  - correct movement pattern for the piece type
-   *  - cannot capture own pieces
-   *  - sliding pieces (bishop, rook, queen) are blocked by intervening pieces
-   */
-  def isLegal(board: Board, from: Square, to: Square): Boolean =
-    legalTargets(board, from).contains(to)
-
-  /** All squares a piece on `from` can legally move to (same rules as isLegal). */
-  def legalTargets(board: Board, from: Square): Set[Square] =
-    board.pieceAt(from) match
-      case None        => Set.empty
-      case Some(piece) =>
-        piece.pieceType match
-          case PieceType.Pawn   => pawnTargets(board, from, piece.color)
-          case PieceType.Knight => knightTargets(board, from, piece.color)
-          case PieceType.Bishop => slide(board, from, piece.color, diagonalDeltas)
-          case PieceType.Rook   => slide(board, from, piece.color, orthogonalDeltas)
-          case PieceType.Queen  => slide(board, from, piece.color, diagonalDeltas ++ orthogonalDeltas)
-          case PieceType.King   => kingTargets(board, from, piece.color)
-
-  // ── helpers ────────────────────────────────────────────────────────────────
-
-  private val diagonalDeltas:    List[(Int, Int)] = List((1, 1), (1, -1), (-1, 1), (-1, -1))
-  private val orthogonalDeltas:  List[(Int, Int)] = List((1, 0), (-1, 0), (0, 1), (0, -1))
-  private val knightDeltas:      List[(Int, Int)] =
-    List((1, 2), (1, -2), (-1, 2), (-1, -2), (2, 1), (2, -1), (-2, 1), (-2, -1))
-
-  /** Try to construct a Square from integer file/rank indices (0-based). */
-  private def squareAt(fileIdx: Int, rankIdx: Int): Option[Square] =
-    Option.when(fileIdx >= 0 && fileIdx <= 7 && rankIdx >= 0 && rankIdx <= 7)(
-      Square(File.values(fileIdx), Rank.values(rankIdx))
-    )
-
-  /** True when `sq` is occupied by a piece of `color`. */
-  private def isOwnPiece(board: Board, sq: Square, color: Color): Boolean =
-    board.pieceAt(sq).exists(_.color == color)
-
-  /** True when `sq` is occupied by a piece of the opposite color. */
-  private def isEnemyPiece(board: Board, sq: Square, color: Color): Boolean =
-    board.pieceAt(sq).exists(_.color != color)
-
-  /** Sliding move generation along a list of direction deltas.
-   *  Each direction continues until the board edge, an own piece, or the first
-   *  enemy piece (which is included as a capture target).
-   */
-  private def slide(board: Board, from: Square, color: Color, deltas: List[(Int, Int)]): Set[Square] =
-    val fi = from.file.ordinal
-    val ri = from.rank.ordinal
-    deltas.flatMap: (df, dr) =>
-      Iterator
-        .iterate((fi + df, ri + dr)) { case (f, r) => (f + df, r + dr) }
-        .takeWhile { case (f, r) => f >= 0 && f <= 7 && r >= 0 && r <= 7 }
-        .map { case (f, r) => Square(File.values(f), Rank.values(r)) }
-        .foldLeft((List.empty[Square], false)):
-          case ((acc, stopped), sq) =>
-            if stopped then (acc, true)
-            else if isOwnPiece(board, sq, color) then (acc, true)          // blocked — stop, no capture
-            else if isEnemyPiece(board, sq, color) then (acc :+ sq, true)  // capture — stop after
-            else (acc :+ sq, false)                                        // empty — continue
-        ._1
-    .toSet
-
-  private def pawnTargets(board: Board, from: Square, color: Color): Set[Square] =
-    val fi       = from.file.ordinal
-    val ri       = from.rank.ordinal
-    val dir      = if color == Color.White then 1 else -1
-    val startRank = if color == Color.White then Rank.R2.ordinal else Rank.R7.ordinal
-
-    val oneStep = squareAt(fi, ri + dir)
-
-    // Forward one square (only if empty)
-    val forward1: Set[Square] = oneStep match
-      case Some(sq) if board.pieceAt(sq).isEmpty => Set(sq)
-      case _                                     => Set.empty
-
-    // Forward two squares from starting rank (only if both intermediate squares are empty)
-    val forward2: Set[Square] =
-      if ri == startRank && forward1.nonEmpty then
-        squareAt(fi, ri + 2 * dir) match
-          case Some(sq) if board.pieceAt(sq).isEmpty => Set(sq)
-          case _                                     => Set.empty
-      else Set.empty
-
-    // Diagonal captures (only if enemy piece present)
-    val captures: Set[Square] =
-      List(-1, 1).flatMap: df =>
-        squareAt(fi + df, ri + dir).filter(sq => isEnemyPiece(board, sq, color))
-      .toSet
-
-    forward1 ++ forward2 ++ captures
-
-  private def knightTargets(board: Board, from: Square, color: Color): Set[Square] =
-    val fi = from.file.ordinal
-    val ri = from.rank.ordinal
-    knightDeltas.flatMap: (df, dr) =>
-      squareAt(fi + df, ri + dr).filterNot(sq => isOwnPiece(board, sq, color))
-    .toSet
-
-  private def kingTargets(board: Board, from: Square, color: Color): Set[Square] =
-    val fi = from.file.ordinal
-    val ri = from.rank.ordinal
-    (diagonalDeltas ++ orthogonalDeltas).flatMap: (df, dr) =>
-      squareAt(fi + df, ri + dr).filterNot(sq => isOwnPiece(board, sq, color))
-    .toSet
-
-  // ── Castling helpers ────────────────────────────────────────────────────────
-
-  private def isAttackedBy(board: Board, sq: Square, attackerColor: Color): Boolean =
-    board.pieces.exists { case (from, piece) =>
-      piece.color == attackerColor && legalTargets(board, from).contains(sq)
-    }
-
-  def isCastle(board: Board, from: Square, to: Square): Boolean =
-    board.pieceAt(from).exists(_.pieceType == PieceType.King) &&
-    math.abs(to.file.ordinal - from.file.ordinal) == 2
-
-  def castleSide(from: Square, to: Square): CastleSide =
-    if to.file.ordinal > from.file.ordinal then CastleSide.Kingside else CastleSide.Queenside
-
-  def castlingTargets(board: Board, history: GameHistory, color: Color): Set[Square] =
-    val rights = CastlingRightsCalculator.deriveCastlingRights(history, color)
-    val rank   = if color == Color.White then Rank.R1 else Rank.R8
-    val kingSq = Square(File.E, rank)
-    val enemy  = color.opposite
-
-    if !board.pieceAt(kingSq).contains(Piece(color, PieceType.King)) ||
-       GameRules.isInCheck(board, color) then Set.empty
-    else
-      val kingsideSq = Option.when(
-        rights.kingSide &&
-        board.pieceAt(Square(File.H, rank)).contains(Piece(color, PieceType.Rook)) &&
-        List(Square(File.F, rank), Square(File.G, rank)).forall(s => board.pieceAt(s).isEmpty) &&
-        !List(Square(File.F, rank), Square(File.G, rank)).exists(s => isAttackedBy(board, s, enemy))
-      )(Square(File.G, rank))
-
-      val queensideSq = Option.when(
-        rights.queenSide &&
-        board.pieceAt(Square(File.A, rank)).contains(Piece(color, PieceType.Rook)) &&
-        List(Square(File.B, rank), Square(File.C, rank), Square(File.D, rank)).forall(s => board.pieceAt(s).isEmpty) &&
-        !List(Square(File.D, rank), Square(File.C, rank)).exists(s => isAttackedBy(board, s, enemy))
-      )(Square(File.C, rank))
-
-      kingsideSq.toSet ++ queensideSq.toSet
-
-  def legalTargets(board: Board, history: GameHistory, from: Square): Set[Square] =
-    board.pieceAt(from) match
-      case Some(piece) if piece.pieceType == PieceType.King =>
-        legalTargets(board, from) ++ castlingTargets(board, history, piece.color)
-      case Some(piece) if piece.pieceType == PieceType.Pawn =>
-        pawnTargets(board, history, from, piece.color)
-      case _ =>
-        legalTargets(board, from)
-
-  private def pawnTargets(board: Board, history: GameHistory, from: Square, color: Color): Set[Square] =
-    val existing = pawnTargets(board, from, color)
-    val fi  = from.file.ordinal
-    val ri  = from.rank.ordinal
-    val dir = if color == Color.White then 1 else -1
-    val epCapture: Set[Square] =
-      EnPassantCalculator.enPassantTarget(board, history).filter: target =>
-        squareAt(fi - 1, ri + dir).contains(target) || squareAt(fi + 1, ri + dir).contains(target)
-      .toSet
-    existing ++ epCapture
-
-  def isLegal(board: Board, history: GameHistory, from: Square, to: Square): Boolean =
-    legalTargets(board, history, from).contains(to)
-
-  /** Returns true if the piece on `from` is a pawn moving to its back rank (promotion). */
-  def isPromotionMove(board: Board, from: Square, to: Square): Boolean =
-    board.pieceAt(from) match
-      case Some(Piece(_, PieceType.Pawn)) =>
-        (from.rank == Rank.R7 && to.rank == Rank.R8) ||
-        (from.rank == Rank.R2 && to.rank == Rank.R1)
-      case _ => false

modules/core/src/main/scala/de/nowchess/chess/notation/FenExporter.scala

@@ -1,60 +0,0 @@
-package de.nowchess.chess.notation
-
-import de.nowchess.api.board.*
-import de.nowchess.api.game.{CastlingRights, GameState}
-import de.nowchess.api.board.Color
-
-object FenExporter:
-
-  /** Convert a Board to FEN piece-placement string (rank 8 to rank 1, separated by '/'). */
-  def boardToFen(board: Board): String =
-    Rank.values.reverse
-      .map(rank => buildRankString(board, rank))
-      .mkString("/")
-
-  /** Build the FEN representation for a single rank. */
-  private def buildRankString(board: Board, rank: Rank): String =
-    val rankSquares = File.values.map(file => Square(file, rank))
-    val rankChars = scala.collection.mutable.ListBuffer[Char]()
-    var emptyCount = 0
-
-    for square <- rankSquares do
-      board.pieceAt(square) match
-        case Some(piece) =>
-          if emptyCount > 0 then
-            rankChars += emptyCount.toString.charAt(0)
-            emptyCount = 0
-          rankChars += pieceToPgnChar(piece)
-        case None =>
-          emptyCount += 1
-
-    if emptyCount > 0 then rankChars += emptyCount.toString.charAt(0)
-    rankChars.mkString
-
-  /** Convert a GameState to a complete FEN string. */
-  def gameStateToFen(state: GameState): String =
-    val piecePlacement = state.piecePlacement
-    val activeColor = if state.activeColor == Color.White then "w" else "b"
-    val castling = castlingString(state.castlingWhite, state.castlingBlack)
-    val enPassant = state.enPassantTarget.map(_.toString).getOrElse("-")
-    s"$piecePlacement $activeColor $castling $enPassant ${state.halfMoveClock} ${state.fullMoveNumber}"
-
-  /** Convert castling rights to FEN notation. */
-  private def castlingString(white: CastlingRights, black: CastlingRights): String =
-    val wk = if white.kingSide then "K" else ""
-    val wq = if white.queenSide then "Q" else ""
-    val bk = if black.kingSide then "k" else ""
-    val bq = if black.queenSide then "q" else ""
-    val result = s"$wk$wq$bk$bq"
-    if result.isEmpty then "-" else result
-
-  /** Convert a Piece to its FEN character (uppercase = White, lowercase = Black). */
-  private def pieceToPgnChar(piece: Piece): Char =
-    val base = piece.pieceType match
-      case PieceType.Pawn   => 'p'
-      case PieceType.Knight => 'n'
-      case PieceType.Bishop => 'b'
-      case PieceType.Rook   => 'r'
-      case PieceType.Queen  => 'q'
-      case PieceType.King   => 'k'
-    if piece.color == Color.White then base.toUpper else base

modules/core/src/main/scala/de/nowchess/chess/notation/FenParser.scala

@@ -1,103 +0,0 @@
-package de.nowchess.chess.notation
-
-import de.nowchess.api.board.*
-import de.nowchess.api.game.{CastlingRights, GameState, GameStatus}
-
-object FenParser:
-
-  /** Parse a complete FEN string into a GameState.
-   *  Returns None if the format is invalid. */
-  def parseFen(fen: String): Option[GameState] =
-    val parts = fen.trim.split("\\s+")
-    Option.when(parts.length == 6)(parts).flatMap: parts =>
-      for
-        _ <- parseBoard(parts(0))
-        activeColor <- parseColor(parts(1))
-        castlingRights <- parseCastling(parts(2))
-        enPassant <- parseEnPassant(parts(3))
-        halfMoveClock <- parts(4).toIntOption
-        fullMoveNumber <- parts(5).toIntOption
-        if halfMoveClock >= 0 && fullMoveNumber >= 1
-      yield GameState(
-        piecePlacement = parts(0),
-        activeColor = activeColor,
-        castlingWhite = castlingRights._1,
-        castlingBlack = castlingRights._2,
-        enPassantTarget = enPassant,
-        halfMoveClock = halfMoveClock,
-        fullMoveNumber = fullMoveNumber,
-        status = GameStatus.InProgress
-      )
-
-  /** Parse active color ("w" or "b"). */
-  private def parseColor(s: String): Option[Color] =
-    if s == "w" then Some(Color.White)
-    else if s == "b" then Some(Color.Black)
-    else None
-
-  /** Parse castling rights string (e.g. "KQkq", "K", "-") into rights for White and Black. */
-  private def parseCastling(s: String): Option[(CastlingRights, CastlingRights)] =
-    if s == "-" then
-      Some((CastlingRights.None, CastlingRights.None))
-    else if s.length <= 4 && s.forall(c => "KQkq".contains(c)) then
-      val white = CastlingRights(kingSide = s.contains('K'), queenSide = s.contains('Q'))
-      val black = CastlingRights(kingSide = s.contains('k'), queenSide = s.contains('q'))
-      Some((white, black))
-    else
-      None
-
-  /** Parse en passant target square ("-" for none, or algebraic like "e3"). */
-  private def parseEnPassant(s: String): Option[Option[Square]] =
-    if s == "-" then Some(None)
-    else Square.fromAlgebraic(s).map(Some(_))
-
-  /** Parses a FEN piece-placement string (rank 8 to rank 1, separated by '/') into a Board.
-   *  Returns None if the format is invalid. */
-  def parseBoard(fen: String): Option[Board] =
-    val rankStrings = fen.split("/", -1)
-    if rankStrings.length != 8 then None
-    else
-      // Parse each rank, collecting all (Square, Piece) pairs or failing on the first error
-      val parsedRanks: Option[List[List[(Square, Piece)]]] =
-        rankStrings.zipWithIndex.foldLeft(Option(List.empty[List[(Square, Piece)]])):
-          case (None, _) => None
-          case (Some(acc), (rankStr, rankIdx)) =>
-            val rank = Rank.values(7 - rankIdx) // ranks go 8→1, so reverse
-            parsePieceRank(rankStr, rank).map(squares => acc :+ squares)
-      parsedRanks.map(ranks => Board(ranks.flatten.toMap))
-
-  /** Parse a single rank string (e.g. "rnbqkbnr" or "p3p3") into a list of (Square, Piece) pairs.
-   *  Returns None if the rank string contains invalid characters or the wrong number of files. */
-  private def parsePieceRank(rankStr: String, rank: Rank): Option[List[(Square, Piece)]] =
-    var fileIdx = 0
-    val squares = scala.collection.mutable.ListBuffer[(Square, Piece)]()
-    var failed = false
-
-    for c <- rankStr if !failed do
-      if fileIdx > 7 then
-        failed = true
-      else if c.isDigit then
-        fileIdx += c.asDigit
-      else
-        charToPiece(c) match
-          case None => failed = true
-          case Some(piece) =>
-            val file = File.values(fileIdx)
-            squares += (Square(file, rank) -> piece)
-            fileIdx += 1
-
-    if failed || fileIdx != 8 then None
-    else Some(squares.toList)
-
-  /** Convert a FEN piece character to a Piece. Uppercase = White, lowercase = Black. */
-  private def charToPiece(c: Char): Option[Piece] =
-    val color = if Character.isUpperCase(c) then Color.White else Color.Black
-    val pieceTypeOpt = c.toLower match
-      case 'p' => Some(PieceType.Pawn)
-      case 'n' => Some(PieceType.Knight)
-      case 'b' => Some(PieceType.Bishop)
-      case 'r' => Some(PieceType.Rook)
-      case 'q' => Some(PieceType.Queen)
-      case 'k' => Some(PieceType.King)
-      case _   => None
-    pieceTypeOpt.map(pt => Piece(color, pt))

modules/core/src/main/scala/de/nowchess/chess/notation/PgnExporter.scala

@@ -1,54 +0,0 @@
-package de.nowchess.chess.notation
-
-import de.nowchess.api.board.{PieceType, *}
-import de.nowchess.api.move.PromotionPiece
-import de.nowchess.chess.logic.{CastleSide, GameHistory, HistoryMove}
-
-object PgnExporter:
-
-  /** Export a game with headers and history to PGN format. */
-  def exportGame(headers: Map[String, String], history: GameHistory): String =
-    val headerLines = headers.map { case (key, value) =>
-      s"""[$key "$value"]"""
-    }.mkString("\n")
-
-    val moveText = if history.moves.isEmpty then ""
-    else
-      val groupedMoves = history.moves.zipWithIndex.groupBy(_._2 / 2)
-      val moveLines = for (moveNumber, movePairs) <- groupedMoves.toList.sortBy(_._1) yield
-        val moveNum = moveNumber + 1
-        val whiteMoveStr = movePairs.find(_._2 % 2 == 0).map(p => moveToAlgebraic(p._1)).getOrElse("")
-        val blackMoveStr = movePairs.find(_._2 % 2 == 1).map(p => moveToAlgebraic(p._1)).getOrElse("")
-        if blackMoveStr.isEmpty then s"$moveNum. $whiteMoveStr"
-        else s"$moveNum. $whiteMoveStr $blackMoveStr"
-
-      val termination = headers.getOrElse("Result", "*")
-      moveLines.mkString(" ") + s" $termination"
-
-    if headerLines.isEmpty then moveText
-    else if moveText.isEmpty then headerLines
-    else s"$headerLines\n\n$moveText"
-
-  /** Convert a HistoryMove to Standard Algebraic Notation. */
-  def moveToAlgebraic(move: HistoryMove): String =
-    move.castleSide match
-      case Some(CastleSide.Kingside)  => "O-O"
-      case Some(CastleSide.Queenside) => "O-O-O"
-      case None =>
-        val dest       = move.to.toString
-        val capStr     = if move.isCapture then "x" else ""
-        val promSuffix = move.promotionPiece match
-          case Some(PromotionPiece.Queen)  => "=Q"
-          case Some(PromotionPiece.Rook)   => "=R"
-          case Some(PromotionPiece.Bishop) => "=B"
-          case Some(PromotionPiece.Knight) => "=N"
-          case None                        => ""
-        move.pieceType match
-          case PieceType.Pawn =>
-            if move.isCapture then s"${move.from.file.toString.toLowerCase}x$dest$promSuffix"
-            else s"$dest$promSuffix"
-          case PieceType.Knight => s"N$capStr$dest$promSuffix"
-          case PieceType.Bishop => s"B$capStr$dest$promSuffix"
-          case PieceType.Rook   => s"R$capStr$dest$promSuffix"
-          case PieceType.Queen  => s"Q$capStr$dest$promSuffix"
-          case PieceType.King   => s"K$capStr$dest$promSuffix"

modules/core/src/main/scala/de/nowchess/chess/notation/PgnParser.scala

@@ -1,267 +0,0 @@
-package de.nowchess.chess.notation
-
-import de.nowchess.api.board.*
-import de.nowchess.api.move.PromotionPiece
-import de.nowchess.chess.logic.{CastleSide, GameHistory, HistoryMove, GameRules, MoveValidator, withCastle}
-
-/** A parsed PGN game containing headers and the resolved move list. */
-case class PgnGame(
-  headers: Map[String, String],
-  moves: List[HistoryMove]
-)
-
-object PgnParser:
-
-  /** Strictly validate a PGN text.
-   *  Returns Right(PgnGame) if every move token is a legal move in the evolving position.
-   *  Returns Left(error message) on the first illegal or impossible move, or any unrecognised token. */
-  def validatePgn(pgn: String): Either[String, PgnGame] =
-    val lines = pgn.split("\n").map(_.trim)
-    val (headerLines, rest) = lines.span(_.startsWith("["))
-    val headers  = parseHeaders(headerLines)
-    val moveText = rest.mkString(" ")
-    validateMovesText(moveText).map(moves => PgnGame(headers, moves))
-
-  /** Parse a complete PGN text into a PgnGame with headers and moves.
-   *  Always succeeds (returns Some); malformed tokens are silently skipped. */
-  def parsePgn(pgn: String): Option[PgnGame] =
-    val lines = pgn.split("\n").map(_.trim)
-    val (headerLines, rest) = lines.span(_.startsWith("["))
-
-    val headers  = parseHeaders(headerLines)
-    val moveText = rest.mkString(" ")
-    val moves    = parseMovesText(moveText)
-
-    Some(PgnGame(headers, moves))
-
-  /** Parse PGN header lines of the form [Key "Value"]. */
-  private def parseHeaders(lines: Array[String]): Map[String, String] =
-    val pattern = """^\[(\w+)\s+"([^"]*)"\s*\]$""".r
-    lines.flatMap(line => pattern.findFirstMatchIn(line).map(m => m.group(1) -> m.group(2))).toMap
-
-  /** Parse the move-text section (e.g. "1. e4 e5 2. Nf3") into resolved HistoryMoves. */
-  private def parseMovesText(moveText: String): List[HistoryMove] =
-    val tokens = moveText.split("\\s+").filter(_.nonEmpty)
-
-    // Fold over tokens, threading (board, history, currentColor, accumulator)
-    val (_, _, _, moves) = tokens.foldLeft(
-      (Board.initial, GameHistory.empty, Color.White, List.empty[HistoryMove])
-    ):
-      case (state @ (board, history, color, acc), token) =>
-        // Skip move-number markers (e.g. "1.", "2.") and result tokens
-        if isMoveNumberOrResult(token) then state
-        else
-          parseAlgebraicMove(token, board, history, color) match
-            case None       => state  // unrecognised token — skip silently
-            case Some(move) =>
-              val newBoard   = applyMoveToBoard(board, move, color)
-              val newHistory = history.addMove(move)
-              (newBoard, newHistory, color.opposite, acc :+ move)
-
-    moves
-
-  /** Apply a single HistoryMove to a Board, handling castling and promotion. */
-  private def applyMoveToBoard(board: Board, move: HistoryMove, color: Color): Board =
-    move.castleSide match
-      case Some(side) => board.withCastle(color, side)
-      case None =>
-        val (boardAfterMove, _) = board.withMove(move.from, move.to)
-        move.promotionPiece match
-          case Some(pp) =>
-            val pieceType = pp match
-              case PromotionPiece.Queen  => PieceType.Queen
-              case PromotionPiece.Rook   => PieceType.Rook
-              case PromotionPiece.Bishop => PieceType.Bishop
-              case PromotionPiece.Knight => PieceType.Knight
-            boardAfterMove.updated(move.to, Piece(color, pieceType))
-          case None => boardAfterMove
-
-  /** True for move-number tokens ("1.", "12.") and PGN result tokens. */
-  private def isMoveNumberOrResult(token: String): Boolean =
-    token.matches("""\d+\.""") ||
-    token == "*"               ||
-    token == "1-0"             ||
-    token == "0-1"             ||
-    token == "1/2-1/2"
-
-  /** Parse a single algebraic notation token into a HistoryMove, given the current board state. */
-  def parseAlgebraicMove(notation: String, board: Board, history: GameHistory, color: Color): Option[HistoryMove] =
-    notation match
-      case "O-O" | "O-O+" | "O-O#" =>
-        val rank = if color == Color.White then Rank.R1 else Rank.R8
-        Some(HistoryMove(Square(File.E, rank), Square(File.G, rank), Some(CastleSide.Kingside), pieceType = PieceType.King))
-
-      case "O-O-O" | "O-O-O+" | "O-O-O#" =>
-        val rank = if color == Color.White then Rank.R1 else Rank.R8
-        Some(HistoryMove(Square(File.E, rank), Square(File.C, rank), Some(CastleSide.Queenside), pieceType = PieceType.King))
-
-      case _ =>
-        parseRegularMove(notation, board, history, color)
-
-  /** Parse regular algebraic notation (pawn moves, piece moves, captures, disambiguation). */
-  private def parseRegularMove(notation: String, board: Board, history: GameHistory, color: Color): Option[HistoryMove] =
-    // Strip check/mate/capture indicators and promotion suffix (e.g. =Q)
-    val clean = notation
-      .replace("+", "")
-      .replace("#", "")
-      .replace("x", "")
-      .replaceAll("=[NBRQ]$", "")
-
-    // The destination square is always the last two characters
-    if clean.length < 2 then None
-    else
-      val destStr = clean.takeRight(2)
-      Square.fromAlgebraic(destStr).flatMap: toSquare =>
-        val disambig = clean.dropRight(2) // "" | "N"|"B"|"R"|"Q"|"K" | file | rank | file+rank
-
-        // Determine required piece type: upper-case first char = piece letter; else pawn
-        val requiredPieceType: Option[PieceType] =
-          if disambig.nonEmpty && disambig.head.isUpper then charToPieceType(disambig.head)
-          else if clean.head.isUpper then charToPieceType(clean.head)
-          else Some(PieceType.Pawn)
-
-        // Collect the disambiguation hint that remains after stripping the piece letter
-        val hint =
-          if disambig.nonEmpty && disambig.head.isUpper then disambig.tail
-          else disambig  // hint is file/rank info or empty
-
-        // Candidate source squares: pieces of `color` that can geometrically reach `toSquare`.
-        // We prefer pieces that can actually reach the target; if none can (positionally illegal
-        // PGN input), fall back to any piece of the matching type belonging to `color`.
-        val reachable: Set[Square] =
-          board.pieces.collect {
-            case (from, piece) if piece.color == color &&
-              MoveValidator.legalTargets(board, from).contains(toSquare) => from
-          }.toSet
-
-        val candidates: Set[Square] =
-          if reachable.nonEmpty then reachable
-          else
-            // Fallback for positionally-illegal but syntactically valid PGN notation:
-            // find any piece of `color` with the correct piece type on the board.
-            board.pieces.collect {
-              case (from, piece) if piece.color == color => from
-            }.toSet
-
-        // Filter by required piece type
-        val byPiece = candidates.filter(from =>
-          requiredPieceType.forall(pt => board.pieceAt(from).exists(_.pieceType == pt))
-        )
-
-        // Apply disambiguation hint (file letter or rank digit)
-        val disambiguated =
-          if hint.isEmpty then byPiece
-          else byPiece.filter(from => matchesHint(from, hint))
-
-        val promotion     = extractPromotion(notation)
-        val movePieceType = requiredPieceType.getOrElse(PieceType.Pawn)
-        val moveIsCapture = notation.contains('x')
-        disambiguated.headOption.map(from => HistoryMove(from, toSquare, None, promotion, movePieceType, moveIsCapture))
-
-  /** True if `sq` matches a disambiguation hint (file letter, rank digit, or both). */
-  private def matchesHint(sq: Square, hint: String): Boolean =
-    hint.forall(c => if c >= 'a' && c <= 'h' then sq.file.toString.equalsIgnoreCase(c.toString)
-    else if c >= '1' && c <= '8' then sq.rank.ordinal == (c - '1')
-    else true)
-
-  /** Extract a promotion piece from a notation string containing =Q/=R/=B/=N. */
-  private[notation] def extractPromotion(notation: String): Option[PromotionPiece] =
-    val promotionPattern = """=([A-Z])""".r
-    promotionPattern.findFirstMatchIn(notation).flatMap { m =>
-      m.group(1) match
-        case "Q" => Some(PromotionPiece.Queen)
-        case "R" => Some(PromotionPiece.Rook)
-        case "B" => Some(PromotionPiece.Bishop)
-        case "N" => Some(PromotionPiece.Knight)
-        case _   => None
-    }
-
-  /** Convert a piece-letter character to a PieceType. */
-  private def charToPieceType(c: Char): Option[PieceType] =
-    c match
-      case 'N' => Some(PieceType.Knight)
-      case 'B' => Some(PieceType.Bishop)
-      case 'R' => Some(PieceType.Rook)
-      case 'Q' => Some(PieceType.Queen)
-      case 'K' => Some(PieceType.King)
-      case _   => None
-
-  // ── Strict validation helpers ─────────────────────────────────────────────
-
-  /** Walk all move tokens, failing immediately on any unresolvable or illegal move. */
-  private def validateMovesText(moveText: String): Either[String, List[HistoryMove]] =
-    val tokens = moveText.split("\\s+").filter(_.nonEmpty)
-    tokens.foldLeft(Right((Board.initial, GameHistory.empty, Color.White, List.empty[HistoryMove])): Either[String, (Board, GameHistory, Color, List[HistoryMove])]) {
-      case (acc, token) =>
-        acc.flatMap { case (board, history, color, moves) =>
-          if isMoveNumberOrResult(token) then Right((board, history, color, moves))
-          else
-            strictParseAlgebraicMove(token, board, history, color) match
-              case None       => Left(s"Illegal or impossible move: '$token'")
-              case Some(move) =>
-                val newBoard   = applyMoveToBoard(board, move, color)
-                val newHistory = history.addMove(move)
-                Right((newBoard, newHistory, color.opposite, moves :+ move))
-        }
-    }.map(_._4)
-
-  /** Strict algebraic move parse — no fallback to positionally-illegal moves. */
-  private def strictParseAlgebraicMove(notation: String, board: Board, history: GameHistory, color: Color): Option[HistoryMove] =
-    val rank = if color == Color.White then Rank.R1 else Rank.R8
-    notation match
-      case "O-O" | "O-O+" | "O-O#" =>
-        val dest = Square(File.G, rank)
-        Option.when(MoveValidator.castlingTargets(board, history, color).contains(dest))(
-          HistoryMove(Square(File.E, rank), dest, Some(CastleSide.Kingside), pieceType = PieceType.King)
-        )
-      case "O-O-O" | "O-O-O+" | "O-O-O#" =>
-        val dest = Square(File.C, rank)
-        Option.when(MoveValidator.castlingTargets(board, history, color).contains(dest))(
-          HistoryMove(Square(File.E, rank), dest, Some(CastleSide.Queenside), pieceType = PieceType.King)
-        )
-      case _ =>
-        strictParseRegularMove(notation, board, history, color)
-
-  /** Strict regular move parse — uses only legally reachable squares, no fallback. */
-  private def strictParseRegularMove(notation: String, board: Board, history: GameHistory, color: Color): Option[HistoryMove] =
-    val clean = notation
-      .replace("+", "")
-      .replace("#", "")
-      .replace("x", "")
-      .replaceAll("=[NBRQ]$", "")
-
-    if clean.length < 2 then None
-    else
-      val destStr = clean.takeRight(2)
-      Square.fromAlgebraic(destStr).flatMap { toSquare =>
-        val disambig = clean.dropRight(2)
-
-        val requiredPieceType: Option[PieceType] =
-          if disambig.nonEmpty && disambig.head.isUpper then charToPieceType(disambig.head)
-          else if clean.head.isUpper then charToPieceType(clean.head)
-          else Some(PieceType.Pawn)
-
-        val hint =
-          if disambig.nonEmpty && disambig.head.isUpper then disambig.tail
-          else disambig
-
-        // Strict: only squares from which a legal move (including en passant/castling awareness) exists.
-        val reachable: Set[Square] =
-          board.pieces.collect {
-            case (from, piece) if piece.color == color &&
-              MoveValidator.legalTargets(board, history, from).contains(toSquare) => from
-          }.toSet
-
-        val byPiece = reachable.filter(from =>
-          requiredPieceType.forall(pt => board.pieceAt(from).exists(_.pieceType == pt))
-        )
-
-        val disambiguated =
-          if hint.isEmpty then byPiece
-          else byPiece.filter(from => matchesHint(from, hint))
-
-        val promotion     = extractPromotion(notation)
-        val movePieceType = requiredPieceType.getOrElse(PieceType.Pawn)
-        val moveIsCapture = notation.contains('x')
-        disambiguated.headOption.map(from => HistoryMove(from, toSquare, None, promotion, movePieceType, moveIsCapture))
-      }

modules/core/src/main/scala/de/nowchess/chess/observer/Observer.scala

@@ -1,110 +1,84 @@
 package de.nowchess.chess.observer
 
-import de.nowchess.api.board.{Board, Color, Square}
-import de.nowchess.chess.logic.GameHistory
+import de.nowchess.api.board.{Color, Square}
+import de.nowchess.api.game.{DrawReason, GameContext}
 
-/** Base trait for all game state events.
- *  Events are immutable snapshots of game state changes.
- */
+/** Base trait for all game state events. Events are immutable snapshots of game state changes.
+  */
 sealed trait GameEvent:
-  def board: Board
-  def history: GameHistory
-  def turn: Color
+  def context: GameContext
 
 /** Fired when a move is successfully executed. */
 case class MoveExecutedEvent(
-  board: Board,
-  history: GameHistory,
-  turn: Color,
-  fromSquare: String,
-  toSquare: String,
-  capturedPiece: Option[String]
+    context: GameContext,
+    fromSquare: String,
+    toSquare: String,
+    capturedPiece: Option[String],
 ) extends GameEvent
 
 /** Fired when the current player is in check. */
 case class CheckDetectedEvent(
-  board: Board,
-  history: GameHistory,
-  turn: Color
+    context: GameContext,
 ) extends GameEvent
 
 /** Fired when the game reaches checkmate. */
 case class CheckmateEvent(
-  board: Board,
-  history: GameHistory,
-  turn: Color,
-  winner: Color
+    context: GameContext,
+    winner: Color,
 ) extends GameEvent
 
-/** Fired when the game reaches stalemate. */
-case class StalemateEvent(
-  board: Board,
-  history: GameHistory,
-  turn: Color
+/** Fired when the game ends in a draw. */
+case class DrawEvent(
+    context: GameContext,
+    reason: DrawReason,
 ) extends GameEvent
 
 /** Fired when a move is invalid. */
 case class InvalidMoveEvent(
-  board: Board,
-  history: GameHistory,
-  turn: Color,
-  reason: String
+    context: GameContext,
+    reason: String,
 ) extends GameEvent
 
 /** Fired when a pawn reaches the back rank and the player must choose a promotion piece. */
 case class PromotionRequiredEvent(
-  board: Board,
-  history: GameHistory,
-  turn: Color,
-  from: Square,
-  to: Square
+    context: GameContext,
+    from: Square,
+    to: Square,
 ) extends GameEvent
 
 /** Fired when the board is reset. */
 case class BoardResetEvent(
-  board: Board,
-  history: GameHistory,
-  turn: Color
+    context: GameContext,
 ) extends GameEvent
 
 /** Fired after any move where the half-move clock reaches 100 — the 50-move rule is now claimable. */
 case class FiftyMoveRuleAvailableEvent(
-  board: Board,
-  history: GameHistory,
-  turn: Color
+    context: GameContext,
 ) extends GameEvent
 
-/** Fired when a player successfully claims a draw under the 50-move rule. */
-case class DrawClaimedEvent(
-  board: Board,
-  history: GameHistory,
-  turn: Color
+/** Fired after any move where the same position occurs for the third time — threefold repetition is now claimable. */
+case class ThreefoldRepetitionAvailableEvent(
+    context: GameContext,
 ) extends GameEvent
 
 /** Fired when a move is undone, carrying PGN notation of the reversed move. */
 case class MoveUndoneEvent(
-  board: Board,
-  history: GameHistory,
-  turn: Color,
-  pgnNotation: String
+    context: GameContext,
+    pgnNotation: String,
 ) extends GameEvent
 
 /** Fired when a previously undone move is redone, carrying PGN notation of the replayed move. */
 case class MoveRedoneEvent(
-  board: Board,
-  history: GameHistory,
-  turn: Color,
-  pgnNotation: String,
-  fromSquare: String,
-  toSquare: String,
-  capturedPiece: Option[String]
+    context: GameContext,
+    pgnNotation: String,
+    fromSquare: String,
+    toSquare: String,
+    capturedPiece: Option[String],
 ) extends GameEvent
 
 /** Fired after a PGN string is successfully loaded and all moves are replayed into history. */
 case class PgnLoadedEvent(
-  board: Board,
-  history: GameHistory,
-  turn: Color
+    context: GameContext,
 ) extends GameEvent
 
 /** Observer trait: implement to receive game state updates. */

modules/core/src/main/scala/de/nowchess/chess/view/Renderer.scala

@@ -1,28 +0,0 @@
-package de.nowchess.chess.view
-
-import de.nowchess.api.board.{Board, Color, File, Rank, Square}
-
-object Renderer:
-
-  private val AnsiReset       = "\u001b[0m"
-  private val AnsiLightSquare = "\u001b[48;5;223m"  // warm beige
-  private val AnsiDarkSquare  = "\u001b[48;5;130m"  // brown
-  private val AnsiWhitePiece  = "\u001b[97m"         // bright white text
-  private val AnsiBlackPiece  = "\u001b[30m"         // black text
-
-  def render(board: Board): String =
-    val rows = (0 until 8).reverse.map { rank =>
-      val cells = (0 until 8).map { file =>
-        val sq        = Square(File.values(file), Rank.values(rank))
-        val isLightSq = (file + rank) % 2 != 0
-        val bgColor   = if isLightSq then AnsiLightSquare else AnsiDarkSquare
-        board.pieceAt(sq) match
-          case Some(piece) =>
-            val fgColor = if piece.color == Color.White then AnsiWhitePiece else AnsiBlackPiece
-            s"$bgColor$fgColor ${piece.unicode} $AnsiReset"
-          case None =>
-            s"$bgColor   $AnsiReset"
-      }.mkString
-      s"${rank + 1} $cells ${rank + 1}"
-    }.mkString("\n")
-    s"  a  b  c  d  e  f  g  h\n$rows\n  a  b  c  d  e  f  g  h\n"

modules/core/src/test/scala/de/nowchess/chess/command/CommandInvokerBranchTest.scala

@@ -1,216 +1,153 @@
 package de.nowchess.chess.command
 
-import de.nowchess.api.board.{Square, File, Rank, Board, Color}
-import de.nowchess.chess.logic.GameHistory
+import de.nowchess.api.board.{File, Rank, Square}
+import de.nowchess.api.game.GameContext
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
 
 class CommandInvokerBranchTest extends AnyFunSuite with Matchers:
-  
+
   private def sq(f: File, r: Rank): Square = Square(f, r)
 
-  // ──── Helper: Command that always fails ────
   private case class FailingCommand() extends Command:
-    override def execute(): Boolean = false
-    override def undo(): Boolean = false
+    override def execute(): Boolean  = false
+    override def undo(): Boolean     = false
     override def description: String = "Failing command"
 
-  // ──── Helper: Command that conditionally fails on undo or execute ────
-  private case class ConditionalFailCommand(var shouldFailOnUndo: Boolean = false, var shouldFailOnExecute: Boolean = false) extends Command:
-    override def execute(): Boolean = !shouldFailOnExecute
-    override def undo(): Boolean = !shouldFailOnUndo
+  private class ConditionalFailCommand(
+      initialShouldFailOnUndo: Boolean = false,
+      initialShouldFailOnExecute: Boolean = false,
+  ) extends Command:
+    val shouldFailOnUndo    = new java.util.concurrent.atomic.AtomicBoolean(initialShouldFailOnUndo)
+    val shouldFailOnExecute = new java.util.concurrent.atomic.AtomicBoolean(initialShouldFailOnExecute)
+    override def execute(): Boolean  = !shouldFailOnExecute.get()
+    override def undo(): Boolean     = !shouldFailOnUndo.get()
     override def description: String = "Conditional fail"
 
   private def createMoveCommand(from: Square, to: Square, executeSucceeds: Boolean = true): MoveCommand =
-    val cmd = MoveCommand(
+    MoveCommand(
       from = from,
       to = to,
-      moveResult = if executeSucceeds then Some(MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)) else None,
-      previousBoard = Some(Board.initial),
-      previousHistory = Some(GameHistory.empty),
-      previousTurn = Some(Color.White)
+      moveResult = if executeSucceeds then Some(MoveResult.Successful(GameContext.initial, None)) else None,
+      previousContext = Some(GameContext.initial),
     )
-    cmd
 
-  // ──── BRANCH: execute() returns false ────
-  test("CommandInvoker.execute() with failing command returns false"):
+  test("execute rejects failing commands and keeps history unchanged"):
     val invoker = new CommandInvoker()
-    val cmd = FailingCommand()
+    val cmd     = FailingCommand()
     invoker.execute(cmd) shouldBe false
     invoker.history.size shouldBe 0
     invoker.getCurrentIndex shouldBe -1
 
-  test("CommandInvoker.execute() does not add failed command to history"):
-    val invoker = new CommandInvoker()
     val failingCmd = FailingCommand()
     val successCmd = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    
     invoker.execute(failingCmd) shouldBe false
     invoker.history.size shouldBe 0
-    
     invoker.execute(successCmd) shouldBe true
     invoker.history.size shouldBe 1
-    invoker.history(0) shouldBe successCmd
+    invoker.history.head shouldBe successCmd
 
-  // ──── BRANCH: undo() with invalid index (currentIndex < 0) ────
-  test("CommandInvoker.undo() returns false when currentIndex < 0"):
-    val invoker = new CommandInvoker()
-    // currentIndex starts at -1
-    invoker.undo() shouldBe false
+  test("undo redo and history trimming cover all command state transitions"):
+    {
+      val invoker = new CommandInvoker()
+      invoker.undo() shouldBe false
+      invoker.canUndo shouldBe false
+      invoker.undo() shouldBe false
+    }
 
-  test("CommandInvoker.undo() returns false when empty history"):
-    val invoker = new CommandInvoker()
-    invoker.canUndo shouldBe false
-    invoker.undo() shouldBe false
+    {
+      val invoker = new CommandInvoker()
+      val cmd1    = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
+      val cmd2    = createMoveCommand(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
+      invoker.execute(cmd1)
+      invoker.execute(cmd2)
+      invoker.undo()
+      invoker.undo()
+      invoker.undo() shouldBe false
+    }
 
-  // ──── BRANCH: undo() with invalid index (currentIndex >= size) ────
-  test("CommandInvoker.undo() returns false when currentIndex >= history size"):
-    val invoker = new CommandInvoker()
-    val cmd1 = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    val cmd2 = createMoveCommand(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
-    
-    invoker.execute(cmd1)
-    invoker.execute(cmd2)
-    // currentIndex now = 1, history.size = 2
-    
-    invoker.undo()  // currentIndex becomes 0
-    invoker.undo()  // currentIndex becomes -1
-    invoker.undo()  // currentIndex still -1, should fail
+    {
+      val invoker        = new CommandInvoker()
+      val failingUndoCmd = ConditionalFailCommand(initialShouldFailOnUndo = true)
+      invoker.execute(failingUndoCmd) shouldBe true
+      invoker.canUndo shouldBe true
+      invoker.undo() shouldBe false
+      invoker.getCurrentIndex shouldBe 0
+    }
 
-  // ──── BRANCH: undo() command returns false ────
-  test("CommandInvoker.undo() returns false when command.undo() fails"):
-    val invoker = new CommandInvoker()
-    val failingCmd = ConditionalFailCommand(shouldFailOnUndo = true)
-    
-    invoker.execute(failingCmd) shouldBe true
-    invoker.canUndo shouldBe true
-    
-    invoker.undo() shouldBe false
-    // Index should not change when undo fails
-    invoker.getCurrentIndex shouldBe 0
+    {
+      val invoker        = new CommandInvoker()
+      val successUndoCmd = ConditionalFailCommand()
+      invoker.execute(successUndoCmd) shouldBe true
+      invoker.undo() shouldBe true
+      invoker.getCurrentIndex shouldBe -1
+    }
 
-  test("CommandInvoker.undo() returns true when command.undo() succeeds"):
-    val invoker = new CommandInvoker()
-    val successCmd = ConditionalFailCommand(shouldFailOnUndo = false)
-    
-    invoker.execute(successCmd) shouldBe true
-    invoker.undo() shouldBe true
-    invoker.getCurrentIndex shouldBe -1
+    {
+      val invoker = new CommandInvoker()
+      invoker.redo() shouldBe false
+    }
 
-  // ──── BRANCH: redo() with invalid index (currentIndex + 1 >= size) ────
-  test("CommandInvoker.redo() returns false when nothing to redo"):
-    val invoker = new CommandInvoker()
-    invoker.redo() shouldBe false
+    {
+      val invoker = new CommandInvoker()
+      val cmd     = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
+      invoker.execute(cmd)
+      invoker.canRedo shouldBe false
+      invoker.redo() shouldBe false
+    }
 
-  test("CommandInvoker.redo() returns false when at end of history"):
-    val invoker = new CommandInvoker()
-    val cmd = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    
-    invoker.execute(cmd)
-    // currentIndex = 0, history.size = 1
-    invoker.canRedo shouldBe false
-    invoker.redo() shouldBe false
+    {
+      val invoker     = new CommandInvoker()
+      val cmd1        = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
+      val redoFailCmd = ConditionalFailCommand()
+      invoker.execute(cmd1)
+      invoker.execute(redoFailCmd)
+      invoker.undo()
+      invoker.canRedo shouldBe true
+      redoFailCmd.shouldFailOnExecute.set(true)
+      invoker.redo() shouldBe false
+      invoker.getCurrentIndex shouldBe 0
+    }
 
-  test("CommandInvoker.redo() returns false when currentIndex + 1 >= size"):
-    val invoker = new CommandInvoker()
-    val cmd1 = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    val cmd2 = createMoveCommand(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
-    
-    invoker.execute(cmd1)
-    invoker.execute(cmd2)
-    // currentIndex = 1, size = 2, currentIndex + 1 = 2, so 2 < 2 is false
-    invoker.canRedo shouldBe false
-    invoker.redo() shouldBe false
+    {
+      val invoker = new CommandInvoker()
+      val cmd     = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
+      invoker.execute(cmd) shouldBe true
+      invoker.undo() shouldBe true
+      invoker.redo() shouldBe true
+      invoker.getCurrentIndex shouldBe 0
+    }
 
-  // ──── BRANCH: redo() command returns false ────
-  test("CommandInvoker.redo() returns false when command.execute() fails"):
-    val invoker = new CommandInvoker()
-    val cmd1 = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    val redoFailCmd = ConditionalFailCommand(shouldFailOnExecute = false)  // Succeeds on first execute
-    
-    invoker.execute(cmd1)
-    invoker.execute(redoFailCmd)  // Succeeds and added to history
-    
-    invoker.undo()
-    // currentIndex = 0, redoFailCmd is at index 1
-    invoker.canRedo shouldBe true
-    
-    // Now modify to fail on next execute (redo)
-    redoFailCmd.shouldFailOnExecute = true
-    invoker.redo() shouldBe false
-    // currentIndex should not change
-    invoker.getCurrentIndex shouldBe 0
-
-  test("CommandInvoker.redo() returns true when command.execute() succeeds"):
-    val invoker = new CommandInvoker()
-    val cmd = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    
-    invoker.execute(cmd) shouldBe true
-    invoker.undo() shouldBe true
-    invoker.redo() shouldBe true
-    invoker.getCurrentIndex shouldBe 0
-
-  // ──── BRANCH: execute() with redo history discarding (while loop) ────
-  test("CommandInvoker.execute() discards redo history via while loop"):
-    val invoker = new CommandInvoker()
-    val cmd1 = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    val cmd2 = createMoveCommand(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
-    val cmd3 = createMoveCommand(sq(File.D, Rank.R2), sq(File.D, Rank.R4))
-    
-    invoker.execute(cmd1)
-    invoker.execute(cmd2)
-    // currentIndex = 1, size = 2
-    
-    invoker.undo()
-    // currentIndex = 0, size = 2
-    // Redo history exists: cmd2 is at index 1
-    invoker.canRedo shouldBe true
-    
-    invoker.execute(cmd3)
-    // while loop should discard cmd2
-    invoker.canRedo shouldBe false
-    invoker.history.size shouldBe 2
-    invoker.history(1) shouldBe cmd3
-
-  test("CommandInvoker.execute() discards multiple redo commands"):
-    val invoker = new CommandInvoker()
-    val cmd1 = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    val cmd2 = createMoveCommand(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
-    val cmd3 = createMoveCommand(sq(File.G, Rank.R1), sq(File.F, Rank.R3))
-    val cmd4 = createMoveCommand(sq(File.D, Rank.R2), sq(File.D, Rank.R4))
-    
-    invoker.execute(cmd1)
-    invoker.execute(cmd2)
-    invoker.execute(cmd3)
-    invoker.execute(cmd4)
-    // currentIndex = 3, size = 4
-    
-    invoker.undo()
-    invoker.undo()
-    // currentIndex = 1, size = 4
-    // Redo history: cmd3 (idx 2), cmd4 (idx 3)
-    invoker.canRedo shouldBe true
-    
-    val newCmd = createMoveCommand(sq(File.B, Rank.R2), sq(File.B, Rank.R4))
-    invoker.execute(newCmd)
-    // While loop should discard indices 2 and 3 (cmd3 and cmd4)
-    invoker.history.size shouldBe 3
-    invoker.canRedo shouldBe false
-
-  // ──── BRANCH: execute() with no redo history to discard ────
-  test("CommandInvoker.execute() with no redo history (while condition false)"):
-    val invoker = new CommandInvoker()
-    val cmd1 = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    val cmd2 = createMoveCommand(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
-    
-    invoker.execute(cmd1)
-    invoker.execute(cmd2)
-    // currentIndex = 1, size = 2
-    // currentIndex < size - 1 is 1 < 1 which is false, so while loop doesn't run
-    
-    invoker.canRedo shouldBe false
-    
-    val cmd3 = createMoveCommand(sq(File.D, Rank.R2), sq(File.D, Rank.R4))
-    invoker.execute(cmd3)  // While loop condition should be false, no iterations
-    invoker.history.size shouldBe 3
+    {
+      val invoker = new CommandInvoker()
+      val cmd1    = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
+      val cmd2    = createMoveCommand(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
+      val cmd3    = createMoveCommand(sq(File.D, Rank.R2), sq(File.D, Rank.R4))
+      invoker.execute(cmd1)
+      invoker.execute(cmd2)
+      invoker.undo()
+      invoker.canRedo shouldBe true
+      invoker.execute(cmd3)
+      invoker.canRedo shouldBe false
+      invoker.history.size shouldBe 2
+      invoker.history(1) shouldBe cmd3
+    }
 
+    {
+      val invoker = new CommandInvoker()
+      val cmd1    = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
+      val cmd2    = createMoveCommand(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
+      val cmd3    = createMoveCommand(sq(File.G, Rank.R1), sq(File.F, Rank.R3))
+      val cmd4    = createMoveCommand(sq(File.D, Rank.R2), sq(File.D, Rank.R4))
+      invoker.execute(cmd1)
+      invoker.execute(cmd2)
+      invoker.execute(cmd3)
+      invoker.execute(cmd4)
+      invoker.undo()
+      invoker.undo()
+      invoker.canRedo shouldBe true
+      val newCmd = createMoveCommand(sq(File.B, Rank.R2), sq(File.B, Rank.R4))
+      invoker.execute(newCmd)
+      invoker.history.size shouldBe 3
+      invoker.canRedo shouldBe false
+    }

modules/core/src/test/scala/de/nowchess/chess/command/CommandInvokerTest.scala

@@ -1,123 +1,67 @@
 package de.nowchess.chess.command
 
-import de.nowchess.api.board.{Square, File, Rank, Board, Color}
-import de.nowchess.chess.logic.GameHistory
+import de.nowchess.api.board.{File, Rank, Square}
+import de.nowchess.api.game.GameContext
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
 
 class CommandInvokerTest extends AnyFunSuite with Matchers:
 
   private def sq(f: File, r: Rank): Square = Square(f, r)
-  
+
   private def createMoveCommand(from: Square, to: Square): MoveCommand =
     MoveCommand(
       from = from,
       to = to,
-      moveResult = Some(MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)),
-      previousBoard = Some(Board.initial),
-      previousHistory = Some(GameHistory.empty),
-      previousTurn = Some(Color.White)
+      moveResult = Some(MoveResult.Successful(GameContext.initial, None)),
+      previousContext = Some(GameContext.initial),
     )
 
-  test("CommandInvoker executes a command and adds it to history"):
+  test("execute appends commands and updates index"):
     val invoker = new CommandInvoker()
-    val cmd = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
+    val cmd     = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
     invoker.execute(cmd) shouldBe true
     invoker.history.size shouldBe 1
     invoker.getCurrentIndex shouldBe 0
 
-  test("CommandInvoker executes multiple commands in sequence"):
-    val invoker = new CommandInvoker()
-    val cmd1 = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
     val cmd2 = createMoveCommand(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
-    invoker.execute(cmd1) shouldBe true
     invoker.execute(cmd2) shouldBe true
     invoker.history.size shouldBe 2
     invoker.getCurrentIndex shouldBe 1
 
-  test("CommandInvoker.canUndo returns false when empty"):
+  test("undo and redo update index and availability flags"):
     val invoker = new CommandInvoker()
+    val cmd     = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
     invoker.canUndo shouldBe false
-
-  test("CommandInvoker.canUndo returns true after execution"):
-    val invoker = new CommandInvoker()
-    val cmd = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
     invoker.execute(cmd)
     invoker.canUndo shouldBe true
-
-  test("CommandInvoker.undo decrements current index"):
-    val invoker = new CommandInvoker()
-    val cmd = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    invoker.execute(cmd)
-    invoker.getCurrentIndex shouldBe 0
     invoker.undo() shouldBe true
     invoker.getCurrentIndex shouldBe -1
-
-  test("CommandInvoker.canRedo returns true after undo"):
-    val invoker = new CommandInvoker()
-    val cmd = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    invoker.execute(cmd)
-    invoker.undo()
     invoker.canRedo shouldBe true
-
-  test("CommandInvoker.redo re-executes a command"):
-    val invoker = new CommandInvoker()
-    val cmd = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    invoker.execute(cmd)
-    invoker.undo() shouldBe true
     invoker.redo() shouldBe true
     invoker.getCurrentIndex shouldBe 0
 
-  test("CommandInvoker.canUndo returns false when at beginning"):
+  test("clear removes full history and resets index"):
     val invoker = new CommandInvoker()
-    val cmd = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    invoker.execute(cmd)
-    invoker.undo()
-    invoker.canUndo shouldBe false
-
-  test("CommandInvoker clear removes all history"):
-    val invoker = new CommandInvoker()
-    val cmd = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
+    val cmd     = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
     invoker.execute(cmd)
     invoker.clear()
     invoker.history.size shouldBe 0
     invoker.getCurrentIndex shouldBe -1
 
-  test("CommandInvoker discards all history when executing after undoing all"):
+  test("execute after undo discards redo history"):
     val invoker = new CommandInvoker()
-    val cmd1 = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    val cmd2 = createMoveCommand(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
-    val cmd3 = createMoveCommand(sq(File.D, Rank.R2), sq(File.D, Rank.R4))
+    val cmd1    = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
+    val cmd2    = createMoveCommand(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
+    val cmd3    = createMoveCommand(sq(File.D, Rank.R2), sq(File.D, Rank.R4))
     invoker.execute(cmd1)
     invoker.execute(cmd2)
     invoker.undo()
-    invoker.undo()
-    // After undoing twice, we're at the beginning (before any commands)
-    invoker.getCurrentIndex shouldBe -1
-    invoker.canRedo shouldBe true
-    // Executing a new command from the beginning discards all redo history
-    invoker.execute(cmd3)
-    invoker.canRedo shouldBe false
-    invoker.history.size shouldBe 1
-    invoker.history(0) shouldBe cmd3
-    invoker.getCurrentIndex shouldBe 0
-
-  test("CommandInvoker discards redo history when executing mid-history"):
-    val invoker = new CommandInvoker()
-    val cmd1 = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    val cmd2 = createMoveCommand(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
-    val cmd3 = createMoveCommand(sq(File.D, Rank.R2), sq(File.D, Rank.R4))
-    invoker.execute(cmd1)
-    invoker.execute(cmd2)
-    invoker.undo()
-    // After one undo, we're at the end of cmd1
     invoker.getCurrentIndex shouldBe 0
     invoker.canRedo shouldBe true
-    // Executing a new command discards cmd2 (the redo history)
     invoker.execute(cmd3)
     invoker.canRedo shouldBe false
     invoker.history.size shouldBe 2
-    invoker.history(0) shouldBe cmd1
+    invoker.history.head shouldBe cmd1
     invoker.history(1) shouldBe cmd3
     invoker.getCurrentIndex shouldBe 1
-

modules/core/src/test/scala/de/nowchess/chess/command/CommandInvokerThreadSafetyTest.scala

@@ -1,131 +0,0 @@
-package de.nowchess.chess.command
-
-import de.nowchess.api.board.{Square, File, Rank, Board, Color}
-import de.nowchess.chess.logic.GameHistory
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-import scala.collection.mutable
-
-class CommandInvokerThreadSafetyTest extends AnyFunSuite with Matchers:
-
-  private def sq(f: File, r: Rank): Square = Square(f, r)
-
-  private def createMoveCommand(from: Square, to: Square): MoveCommand =
-    MoveCommand(
-      from = from,
-      to = to,
-      moveResult = Some(MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)),
-      previousBoard = Some(Board.initial),
-      previousHistory = Some(GameHistory.empty),
-      previousTurn = Some(Color.White)
-    )
-
-  test("CommandInvoker is thread-safe for concurrent execute and history reads"):
-    val invoker = new CommandInvoker()
-    @volatile var raceDetected = false
-    val exceptions = mutable.ListBuffer[Exception]()
-
-    // Thread 1: executes commands
-    val executorThread = new Thread(new Runnable {
-      def run(): Unit = {
-        try {
-          for i <- 1 to 1000 do
-            val cmd = createMoveCommand(
-              sq(File.E, Rank.R2),
-              sq(File.E, Rank.R4)
-            )
-            invoker.execute(cmd)
-        } catch {
-          case e: Exception =>
-            exceptions += e
-            raceDetected = true
-        }
-      }
-    })
-
-    // Thread 2: reads history during execution
-    val readerThread = new Thread(new Runnable {
-      def run(): Unit = {
-        try {
-          for _ <- 1 to 1000 do
-            val _ = invoker.history
-            val _ = invoker.getCurrentIndex
-            Thread.sleep(0) // Yield to increase contention
-        } catch {
-          case e: Exception =>
-            exceptions += e
-            raceDetected = true
-        }
-      }
-    })
-
-    executorThread.start()
-    readerThread.start()
-    executorThread.join()
-    readerThread.join()
-
-    exceptions.isEmpty shouldBe true
-    raceDetected shouldBe false
-
-  test("CommandInvoker is thread-safe for concurrent execute, undo, and redo"):
-    val invoker = new CommandInvoker()
-    @volatile var raceDetected = false
-    val exceptions = mutable.ListBuffer[Exception]()
-
-    // Pre-populate with some commands
-    for _ <- 1 to 5 do
-      invoker.execute(createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4)))
-
-    // Thread 1: executes new commands
-    val executorThread = new Thread(new Runnable {
-      def run(): Unit = {
-        try {
-          for _ <- 1 to 500 do
-            invoker.execute(createMoveCommand(sq(File.D, Rank.R2), sq(File.D, Rank.R4)))
-        } catch {
-          case e: Exception =>
-            exceptions += e
-            raceDetected = true
-        }
-      }
-    })
-
-    // Thread 2: undoes commands
-    val undoThread = new Thread(new Runnable {
-      def run(): Unit = {
-        try {
-          for _ <- 1 to 500 do
-            if invoker.canUndo then
-              invoker.undo()
-        } catch {
-          case e: Exception =>
-            exceptions += e
-            raceDetected = true
-        }
-      }
-    })
-
-    // Thread 3: redoes commands
-    val redoThread = new Thread(new Runnable {
-      def run(): Unit = {
-        try {
-          for _ <- 1 to 500 do
-            if invoker.canRedo then
-              invoker.redo()
-        } catch {
-          case e: Exception =>
-            exceptions += e
-            raceDetected = true
-        }
-      }
-    })
-
-    executorThread.start()
-    undoThread.start()
-    redoThread.start()
-    executorThread.join()
-    undoThread.join()
-    redoThread.join()
-
-    exceptions.isEmpty shouldBe true
-    raceDetected shouldBe false

modules/core/src/test/scala/de/nowchess/chess/command/CommandTest.scala

@@ -1,52 +1,23 @@
 package de.nowchess.chess.command
 
-import de.nowchess.api.board.{Board, Color}
-import de.nowchess.chess.logic.GameHistory
+import de.nowchess.api.game.GameContext
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
 
 class CommandTest extends AnyFunSuite with Matchers:
 
-  test("QuitCommand can be created"):
-    val cmd = QuitCommand()
-    cmd shouldNot be(null)
-
-  test("QuitCommand execute returns true"):
+  test("QuitCommand properties and behavior"):
     val cmd = QuitCommand()
     cmd.execute() shouldBe true
-
-  test("QuitCommand undo returns false (cannot undo quit)"):
-    val cmd = QuitCommand()
     cmd.undo() shouldBe false
-
-  test("QuitCommand description"):
-    val cmd = QuitCommand()
     cmd.description shouldBe "Quit game"
 
-  test("ResetCommand with no prior state"):
-    val cmd = ResetCommand()
-    cmd.execute() shouldBe true
-    cmd.undo() shouldBe false
-
-  test("ResetCommand with prior state can undo"):
-    val cmd = ResetCommand(
-      previousBoard = Some(Board.initial),
-      previousHistory = Some(GameHistory.empty),
-      previousTurn = Some(Color.White)
-    )
-    cmd.execute() shouldBe true
-    cmd.undo() shouldBe true
-
-  test("ResetCommand with partial state cannot undo"):
-    val cmd = ResetCommand(
-      previousBoard = Some(Board.initial),
-      previousHistory = None,  // missing
-      previousTurn = Some(Color.White)
-    )
-    cmd.execute() shouldBe true
-    cmd.undo() shouldBe false
-
-  test("ResetCommand description"):
-    val cmd = ResetCommand()
-    cmd.description shouldBe "Reset board"
+  test("ResetCommand behavior depends on previousContext"):
+    val noState = ResetCommand()
+    noState.execute() shouldBe true
+    noState.undo() shouldBe false
+    noState.description shouldBe "Reset board"
 
+    val withState = ResetCommand(previousContext = Some(GameContext.initial))
+    withState.execute() shouldBe true
+    withState.undo() shouldBe true

modules/core/src/test/scala/de/nowchess/chess/command/MoveCommandImmutabilityTest.scala

@@ -1,65 +0,0 @@
-package de.nowchess.chess.command
-
-import de.nowchess.api.board.{Square, File, Rank, Board, Color}
-import de.nowchess.chess.logic.GameHistory
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class MoveCommandImmutabilityTest extends AnyFunSuite with Matchers:
-
-  private def sq(f: File, r: Rank): Square = Square(f, r)
-
-  test("MoveCommand should be immutable - fields cannot be mutated after creation"):
-    val cmd1 = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4)
-    )
-
-    // Create second command with filled state
-    val result = MoveResult.Successful(Board.initial, GameHistory.empty, Color.Black, None)
-    val cmd2 = cmd1.copy(
-      moveResult = Some(result),
-      previousBoard = Some(Board.initial),
-      previousHistory = Some(GameHistory.empty),
-      previousTurn = Some(Color.White)
-    )
-
-    // Original should be unchanged
-    cmd1.moveResult shouldBe None
-    cmd1.previousBoard shouldBe None
-    cmd1.previousHistory shouldBe None
-    cmd1.previousTurn shouldBe None
-
-    // New should have values
-    cmd2.moveResult shouldBe Some(result)
-    cmd2.previousBoard shouldBe Some(Board.initial)
-    cmd2.previousHistory shouldBe Some(GameHistory.empty)
-    cmd2.previousTurn shouldBe Some(Color.White)
-
-  test("MoveCommand equals and hashCode respect immutability"):
-    val cmd1 = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4),
-      moveResult = None,
-      previousBoard = None,
-      previousHistory = None,
-      previousTurn = None
-    )
-
-    val cmd2 = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4),
-      moveResult = None,
-      previousBoard = None,
-      previousHistory = None,
-      previousTurn = None
-    )
-
-    // Same values should be equal
-    cmd1 shouldBe cmd2
-    cmd1.hashCode shouldBe cmd2.hashCode
-
-    // Hash should be consistent (required for use as map keys)
-    val hash1 = cmd1.hashCode
-    val hash2 = cmd1.hashCode
-    hash1 shouldBe hash2

modules/core/src/test/scala/de/nowchess/chess/command/MoveCommandTest.scala

@@ -0,0 +1,70 @@
+package de.nowchess.chess.command
+
+import de.nowchess.api.board.{File, Rank, Square}
+import de.nowchess.api.game.GameContext
+import org.scalatest.funsuite.AnyFunSuite
+import org.scalatest.matchers.should.Matchers
+
+class MoveCommandTest extends AnyFunSuite with Matchers:
+
+  private def sq(f: File, r: Rank): Square = Square(f, r)
+
+  test("MoveCommand defaults to empty optional state and false execute/undo"):
+    val cmd = MoveCommand(from = sq(File.E, Rank.R2), to = sq(File.E, Rank.R4))
+    cmd.moveResult shouldBe None
+    cmd.previousContext shouldBe None
+    cmd.execute() shouldBe false
+    cmd.undo() shouldBe false
+    cmd.description shouldBe "Move from e2 to e4"
+
+  test("MoveCommand execute/undo succeed when state is present"):
+    val executable = MoveCommand(
+      from = sq(File.E, Rank.R2),
+      to = sq(File.E, Rank.R4),
+      moveResult = Some(MoveResult.Successful(GameContext.initial, None)),
+    )
+    executable.execute() shouldBe true
+
+    val undoable = MoveCommand(
+      from = sq(File.E, Rank.R2),
+      to = sq(File.E, Rank.R4),
+      moveResult = Some(MoveResult.Successful(GameContext.initial, None)),
+      previousContext = Some(GameContext.initial),
+    )
+    undoable.undo() shouldBe true
+
+  test("MoveCommand is immutable and preserves equality/hash semantics"):
+    val cmd1 = MoveCommand(from = sq(File.E, Rank.R2), to = sq(File.E, Rank.R4))
+
+    val result = MoveResult.Successful(GameContext.initial, None)
+    val cmd2 = cmd1.copy(
+      moveResult = Some(result),
+      previousContext = Some(GameContext.initial),
+    )
+
+    cmd1.moveResult shouldBe None
+    cmd1.previousContext shouldBe None
+
+    cmd2.moveResult shouldBe Some(result)
+    cmd2.previousContext shouldBe Some(GameContext.initial)
+
+    val eq1 = MoveCommand(
+      from = sq(File.E, Rank.R2),
+      to = sq(File.E, Rank.R4),
+      moveResult = None,
+      previousContext = None,
+    )
+
+    val eq2 = MoveCommand(
+      from = sq(File.E, Rank.R2),
+      to = sq(File.E, Rank.R4),
+      moveResult = None,
+      previousContext = None,
+    )
+
+    eq1 shouldBe eq2
+    eq1.hashCode shouldBe eq2.hashCode
+
+    val hash1 = eq1.hashCode
+    val hash2 = eq1.hashCode
+    hash1 shouldBe hash2

modules/core/src/test/scala/de/nowchess/chess/controller/GameControllerTest.scala

@@ -1,526 +0,0 @@
-package de.nowchess.chess.controller
-
-import de.nowchess.api.board.*
-import de.nowchess.api.game.CastlingRights
-import de.nowchess.api.move.PromotionPiece
-import de.nowchess.chess.logic.{CastleSide, GameHistory}
-import de.nowchess.chess.notation.FenParser
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class GameControllerTest extends AnyFunSuite with Matchers:
-
-  private def sq(f: File, r: Rank): Square = Square(f, r)
-  private def processMove(board: Board, history: GameHistory, turn: Color, raw: String): MoveResult =
-    GameController.processMove(board, history, turn, raw)
-
-  private def castlingRights(history: GameHistory, color: Color): CastlingRights =
-    de.nowchess.chess.logic.CastlingRightsCalculator.deriveCastlingRights(history, color)
-
-  // ──── processMove ────────────────────────────────────────────────────
-
-  test("processMove: 'quit' input returns Quit"):
-    processMove(Board.initial, GameHistory.empty, Color.White, "quit") shouldBe MoveResult.Quit
-
-  test("processMove: 'q' input returns Quit"):
-    processMove(Board.initial, GameHistory.empty, Color.White, "q") shouldBe MoveResult.Quit
-
-  test("processMove: quit with surrounding whitespace returns Quit"):
-    processMove(Board.initial, GameHistory.empty, Color.White, "  quit  ") shouldBe MoveResult.Quit
-
-  test("processMove: unparseable input returns InvalidFormat"):
-    processMove(Board.initial, GameHistory.empty, Color.White, "xyz") shouldBe MoveResult.InvalidFormat("xyz")
-
-  test("processMove: valid format but empty square returns NoPiece"):
-    // E3 is empty in the initial position
-    processMove(Board.initial, GameHistory.empty, Color.White, "e3e4") shouldBe MoveResult.NoPiece
-
-  test("processMove: piece of wrong color returns WrongColor"):
-    // E7 has a Black pawn; it is White's turn
-    processMove(Board.initial, GameHistory.empty, Color.White, "e7e6") shouldBe MoveResult.WrongColor
-
-  test("processMove: geometrically illegal move returns IllegalMove"):
-    // White pawn at E2 cannot jump three squares to E5
-    processMove(Board.initial, GameHistory.empty, Color.White, "e2e5") shouldBe MoveResult.IllegalMove
-
-  test("processMove: move that leaves own king in check returns IllegalMove"):
-    // White King E1 is in check from Black Rook E8. Moving the D2 pawn is
-    // geometrically legal but does not resolve the check — must be rejected.
-    val b = Board(Map(
-      sq(File.E, Rank.R1) -> Piece.WhiteKing,
-      sq(File.D, Rank.R2) -> Piece.WhitePawn,
-      sq(File.E, Rank.R8) -> Piece.BlackRook,
-      sq(File.A, Rank.R8) -> Piece.BlackKing
-    ))
-    processMove(b, GameHistory.empty, Color.White, "d2d4") shouldBe MoveResult.IllegalMove
-
-  test("processMove: move that resolves check is allowed"):
-    // White King E1 is in check from Black Rook E8 along the E-file.
-    // White Rook A5 interposes at E5 — resolves the check, no new check on Black King A8.
-    val b = Board(Map(
-      sq(File.E, Rank.R1) -> Piece.WhiteKing,
-      sq(File.A, Rank.R5) -> Piece.WhiteRook,
-      sq(File.E, Rank.R8) -> Piece.BlackRook,
-      sq(File.A, Rank.R8) -> Piece.BlackKing
-    ))
-    processMove(b, GameHistory.empty, Color.White, "a5e5") match
-      case _: MoveResult.Moved => succeed
-      case other => fail(s"Expected Moved, got $other")
-
-  test("processMove: legal pawn move returns Moved with updated board and flipped turn"):
-    processMove(Board.initial, GameHistory.empty, Color.White, "e2e4") match
-      case MoveResult.Moved(newBoard, newHistory, captured, newTurn) =>
-        newBoard.pieceAt(sq(File.E, Rank.R4)) shouldBe Some(Piece.WhitePawn)
-        newBoard.pieceAt(sq(File.E, Rank.R2)) shouldBe None
-        captured shouldBe None
-        newTurn shouldBe Color.Black
-      case other => fail(s"Expected Moved, got $other")
-
-  test("processMove: legal capture returns Moved with the captured piece"):
-    val board = Board(Map(
-      sq(File.E, Rank.R5) -> Piece.WhitePawn,
-      sq(File.D, Rank.R6) -> Piece.BlackPawn,
-      sq(File.H, Rank.R1) -> Piece.BlackKing,
-      sq(File.H, Rank.R8) -> Piece.WhiteKing
-    ))
-    processMove(board, GameHistory.empty, Color.White, "e5d6") match
-      case MoveResult.Moved(newBoard, newHistory, captured, newTurn) =>
-        captured shouldBe Some(Piece.BlackPawn)
-        newBoard.pieceAt(sq(File.D, Rank.R6)) shouldBe Some(Piece.WhitePawn)
-        newTurn shouldBe Color.Black
-      case other => fail(s"Expected Moved, got $other")
-
-  // ──── processMove: check / checkmate / stalemate ─────────────────────
-
-  test("processMove: legal move that delivers check returns MovedInCheck"):
-    // White Ra1, Ka3; Black Kh8 — White plays Ra1-Ra8, Ra8 attacks rank 8 putting Kh8 in check
-    // Kh8 can escape to g7/g8/h7 so this is InCheck, not Mated
-    val b = Board(Map(
-      sq(File.A, Rank.R1) -> Piece.WhiteRook,
-      sq(File.C, Rank.R3) -> Piece.WhiteKing,
-      sq(File.H, Rank.R8) -> Piece.BlackKing
-    ))
-    processMove(b, GameHistory.empty, Color.White, "a1a8") match
-      case MoveResult.MovedInCheck(_, _, _, newTurn) => newTurn shouldBe Color.Black
-      case other => fail(s"Expected MovedInCheck, got $other")
-
-  test("processMove: legal move that results in checkmate returns Checkmate"):
-    // White Qa1, Ka6; Black Ka8 — White plays Qa1-Qh8 (diagonal a1→h8)
-    // After Qh8: White Qh8 + Ka6 vs Black Ka8 = checkmate (spec-verified position)
-    // Qa1 does NOT currently attack Ka8 — path along file A is blocked by Ka6
-    val b = Board(Map(
-      sq(File.A, Rank.R1) -> Piece.WhiteQueen,
-      sq(File.A, Rank.R6) -> Piece.WhiteKing,
-      sq(File.A, Rank.R8) -> Piece.BlackKing
-    ))
-    processMove(b, GameHistory.empty, Color.White, "a1h8") match
-      case MoveResult.Checkmate(winner) => winner shouldBe Color.White
-      case other => fail(s"Expected Checkmate(White), got $other")
-
-  test("processMove: legal move that results in stalemate returns Stalemate"):
-    // White Qb1, Kc6; Black Ka8 — White plays Qb1-Qb6
-    // After Qb6: White Qb6 + Kc6 vs Black Ka8 = stalemate (spec-verified position)
-    val b = Board(Map(
-      sq(File.B, Rank.R1) -> Piece.WhiteQueen,
-      sq(File.C, Rank.R6) -> Piece.WhiteKing,
-      sq(File.A, Rank.R8) -> Piece.BlackKing
-    ))
-    processMove(b, GameHistory.empty, Color.White, "b1b6") match
-      case MoveResult.Stalemate => succeed
-      case other => fail(s"Expected Stalemate, got $other")
-
-  // ──── castling execution ─────────────────────────────────────────────
-
-  test("processMove: e1g1 returns Moved with king on g1 and rook on f1"):
-    val b = Board(Map(
-        sq(File.E, Rank.R1) -> Piece.WhiteKing,
-        sq(File.H, Rank.R1) -> Piece.WhiteRook,
-        sq(File.H, Rank.R8) -> Piece.BlackKing
-      ))
-    processMove(b, GameHistory.empty, Color.White, "e1g1") match
-      case MoveResult.Moved(newBoard, newHistory, captured, newTurn) =>
-        newBoard.pieceAt(sq(File.G, Rank.R1)) shouldBe Some(Piece.WhiteKing)
-        newBoard.pieceAt(sq(File.F, Rank.R1)) shouldBe Some(Piece.WhiteRook)
-        newBoard.pieceAt(sq(File.E, Rank.R1)) shouldBe None
-        newBoard.pieceAt(sq(File.H, Rank.R1)) shouldBe None
-        captured shouldBe None
-        newTurn shouldBe Color.Black
-      case other => fail(s"Expected Moved, got $other")
-
-  test("processMove: e1c1 returns Moved with king on c1 and rook on d1"):
-    val b = Board(Map(
-        sq(File.E, Rank.R1) -> Piece.WhiteKing,
-        sq(File.A, Rank.R1) -> Piece.WhiteRook,
-        sq(File.H, Rank.R8) -> Piece.BlackKing
-      ))
-    processMove(b, GameHistory.empty, Color.White, "e1c1") match
-      case MoveResult.Moved(newBoard, _, _, _) =>
-        newBoard.pieceAt(sq(File.C, Rank.R1)) shouldBe Some(Piece.WhiteKing)
-        newBoard.pieceAt(sq(File.D, Rank.R1)) shouldBe Some(Piece.WhiteRook)
-      case other => fail(s"Expected Moved, got $other")
-
-  // ──── rights revocation ──────────────────────────────────────────────
-
-  test("processMove: e1g1 revokes both white castling rights"):
-    val b = Board(Map(
-        sq(File.E, Rank.R1) -> Piece.WhiteKing,
-        sq(File.H, Rank.R1) -> Piece.WhiteRook,
-        sq(File.H, Rank.R8) -> Piece.BlackKing
-      ))
-    processMove(b, GameHistory.empty, Color.White, "e1g1") match
-      case MoveResult.Moved(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.White) shouldBe CastlingRights.None
-      case other => fail(s"Expected Moved, got $other")
-
-  test("processMove: moving rook from h1 revokes white kingside right"):
-    val b = Board(Map(
-        sq(File.E, Rank.R1) -> Piece.WhiteKing,
-        sq(File.H, Rank.R1) -> Piece.WhiteRook,
-        sq(File.H, Rank.R8) -> Piece.BlackKing
-      ))
-    processMove(b, GameHistory.empty, Color.White, "h1h4") match
-      case MoveResult.Moved(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.White).kingSide  shouldBe false
-        castlingRights(newHistory, Color.White).queenSide shouldBe true
-      case MoveResult.MovedInCheck(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.White).kingSide  shouldBe false
-        castlingRights(newHistory, Color.White).queenSide shouldBe true
-      case other => fail(s"Expected Moved or MovedInCheck, got $other")
-
-  test("processMove: moving king from e1 revokes both white rights"):
-    val b = Board(Map(
-        sq(File.E, Rank.R1) -> Piece.WhiteKing,
-        sq(File.H, Rank.R8) -> Piece.BlackKing
-      ))
-    processMove(b, GameHistory.empty, Color.White, "e1e2") match
-      case MoveResult.Moved(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.White) shouldBe CastlingRights.None
-      case other => fail(s"Expected Moved, got $other")
-
-  test("processMove: enemy capture on h1 revokes white kingside right"):
-    val b = Board(Map(
-        sq(File.E, Rank.R1) -> Piece.WhiteKing,
-        sq(File.H, Rank.R1) -> Piece.WhiteRook,
-        sq(File.H, Rank.R2) -> Piece.BlackRook,
-        sq(File.A, Rank.R8) -> Piece.BlackKing
-      ))
-    processMove(b, GameHistory.empty, Color.Black, "h2h1") match
-      case MoveResult.Moved(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.White).kingSide shouldBe false
-      case MoveResult.MovedInCheck(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.White).kingSide shouldBe false
-      case other => fail(s"Expected Moved or MovedInCheck, got $other")
-
-  test("processMove: castle attempt when rights revoked returns IllegalMove"):
-    val b = Board(Map(
-        sq(File.E, Rank.R1) -> Piece.WhiteKing,
-        sq(File.H, Rank.R1) -> Piece.WhiteRook,
-        sq(File.H, Rank.R8) -> Piece.BlackKing
-      ))
-    val history = GameHistory.empty.addMove(sq(File.E, Rank.R1), sq(File.E, Rank.R2)).addMove(sq(File.E, Rank.R2), sq(File.E, Rank.R1))
-    processMove(b, history, Color.White, "e1g1") shouldBe MoveResult.IllegalMove
-
-  test("processMove: castle attempt when rook not on home square returns IllegalMove"):
-    val b = Board(Map(
-        sq(File.E, Rank.R1) -> Piece.WhiteKing,
-        sq(File.G, Rank.R1) -> Piece.WhiteRook,
-        sq(File.H, Rank.R8) -> Piece.BlackKing
-      ))
-    processMove(b, GameHistory.empty, Color.White, "e1g1") shouldBe MoveResult.IllegalMove
-
-  test("processMove: moving king from e8 revokes both black rights"):
-    val b = Board(Map(
-        sq(File.E, Rank.R8) -> Piece.BlackKing,
-        sq(File.H, Rank.R1) -> Piece.WhiteKing
-      ))
-    processMove(b, GameHistory.empty, Color.Black, "e8e7") match
-      case MoveResult.Moved(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.Black) shouldBe CastlingRights.None
-      case MoveResult.MovedInCheck(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.Black) shouldBe CastlingRights.None
-      case other => fail(s"Expected Moved or MovedInCheck, got $other")
-
-  test("processMove: moving rook from a8 revokes black queenside right"):
-    val b = Board(Map(
-        sq(File.E, Rank.R8) -> Piece.BlackKing,
-        sq(File.A, Rank.R8) -> Piece.BlackRook,
-        sq(File.H, Rank.R1) -> Piece.WhiteKing
-      ))
-    processMove(b, GameHistory.empty, Color.Black, "a8a1") match
-      case MoveResult.Moved(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.Black).queenSide shouldBe false
-        castlingRights(newHistory, Color.Black).kingSide  shouldBe true
-      case MoveResult.MovedInCheck(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.Black).queenSide shouldBe false
-        castlingRights(newHistory, Color.Black).kingSide  shouldBe true
-      case other => fail(s"Expected Moved or MovedInCheck, got $other")
-
-  test("processMove: moving rook from h8 revokes black kingside right"):
-    val b = Board(Map(
-        sq(File.E, Rank.R8) -> Piece.BlackKing,
-        sq(File.H, Rank.R8) -> Piece.BlackRook,
-        sq(File.A, Rank.R1) -> Piece.WhiteKing
-      ))
-    processMove(b, GameHistory.empty, Color.Black, "h8h4") match
-      case MoveResult.Moved(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.Black).kingSide  shouldBe false
-        castlingRights(newHistory, Color.Black).queenSide shouldBe true
-      case MoveResult.MovedInCheck(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.Black).kingSide  shouldBe false
-        castlingRights(newHistory, Color.Black).queenSide shouldBe true
-      case other => fail(s"Expected Moved or MovedInCheck, got $other")
-
-  test("processMove: enemy capture on a1 revokes white queenside right"):
-    val b = Board(Map(
-        sq(File.E, Rank.R1) -> Piece.WhiteKing,
-        sq(File.A, Rank.R1) -> Piece.WhiteRook,
-        sq(File.A, Rank.R2) -> Piece.BlackRook,
-        sq(File.H, Rank.R8) -> Piece.BlackKing
-      ))
-    processMove(b, GameHistory.empty, Color.Black, "a2a1") match
-      case MoveResult.Moved(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.White).queenSide shouldBe false
-      case MoveResult.MovedInCheck(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.White).queenSide shouldBe false
-      case other => fail(s"Expected Moved or MovedInCheck, got $other")
-
-  // ──── en passant ────────────────────────────────────────────────────────
-
-  test("en passant capture removes the captured pawn from the board"):
-    // Setup: white pawn e5, black pawn just double-pushed to d5 (ep target = d6)
-    val b = Board(Map(
-      Square(File.E, Rank.R5) -> Piece.WhitePawn,
-      Square(File.D, Rank.R5) -> Piece.BlackPawn,
-      Square(File.E, Rank.R1) -> Piece.WhiteKing,
-      Square(File.E, Rank.R8) -> Piece.BlackKing
-    ))
-    val h = GameHistory.empty.addMove(Square(File.D, Rank.R7), Square(File.D, Rank.R5))
-    val result = GameController.processMove(b, h, Color.White, "e5d6")
-    result match
-      case MoveResult.Moved(newBoard, _, captured, _) =>
-        newBoard.pieceAt(Square(File.D, Rank.R5)) shouldBe None  // captured pawn removed
-        newBoard.pieceAt(Square(File.D, Rank.R6)) shouldBe Some(Piece.WhitePawn)  // capturing pawn placed
-        captured shouldBe Some(Piece.BlackPawn)
-      case other => fail(s"Expected Moved but got $other")
-
-  test("en passant capture by black removes the captured white pawn"):
-    // Setup: black pawn d4, white pawn just double-pushed to e4 (ep target = e3)
-    val b = Board(Map(
-      Square(File.D, Rank.R4) -> Piece.BlackPawn,
-      Square(File.E, Rank.R4) -> Piece.WhitePawn,
-      Square(File.E, Rank.R8) -> Piece.BlackKing,
-      Square(File.E, Rank.R1) -> Piece.WhiteKing
-    ))
-    val h = GameHistory.empty.addMove(Square(File.E, Rank.R2), Square(File.E, Rank.R4))
-    val result = GameController.processMove(b, h, Color.Black, "d4e3")
-    result match
-      case MoveResult.Moved(newBoard, _, captured, _) =>
-        newBoard.pieceAt(Square(File.E, Rank.R4)) shouldBe None  // captured pawn removed
-        newBoard.pieceAt(Square(File.E, Rank.R3)) shouldBe Some(Piece.BlackPawn)  // capturing pawn placed
-        captured shouldBe Some(Piece.WhitePawn)
-      case other => fail(s"Expected Moved but got $other")
-
-  // ──── pawn promotion detection ───────────────────────────────────────────
-
-  test("processMove detects white pawn reaching R8 and returns PromotionRequired"):
-    val board = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val result = GameController.processMove(board, GameHistory.empty, Color.White, "e7e8")
-    result should matchPattern { case _: MoveResult.PromotionRequired => }
-    result match
-      case MoveResult.PromotionRequired(from, to, _, _, _, turn) =>
-        from should be (sq(File.E, Rank.R7))
-        to   should be (sq(File.E, Rank.R8))
-        turn should be (Color.White)
-      case _ => fail("Expected PromotionRequired")
-
-  test("processMove detects black pawn reaching R1 and returns PromotionRequired"):
-    val board = FenParser.parseBoard("8/8/8/8/4K3/8/4p3/8").get
-    val result = GameController.processMove(board, GameHistory.empty, Color.Black, "e2e1")
-    result should matchPattern { case _: MoveResult.PromotionRequired => }
-    result match
-      case MoveResult.PromotionRequired(from, to, _, _, _, turn) =>
-        from should be (sq(File.E, Rank.R2))
-        to   should be (sq(File.E, Rank.R1))
-        turn should be (Color.Black)
-      case _ => fail("Expected PromotionRequired")
-
-  test("processMove detects pawn capturing to back rank as PromotionRequired with captured piece"):
-    val board = FenParser.parseBoard("3q4/4P3/8/8/8/8/8/8").get
-    val result = GameController.processMove(board, GameHistory.empty, Color.White, "e7d8")
-    result should matchPattern { case _: MoveResult.PromotionRequired => }
-    result match
-      case MoveResult.PromotionRequired(_, _, _, _, captured, _) =>
-        captured should be (Some(Piece(Color.Black, PieceType.Queen)))
-      case _ => fail("Expected PromotionRequired")
-
-  // ──── completePromotion ──────────────────────────────────────────────────
-
-  test("completePromotion applies move and places queen"):
-    // Black king on h1: not attacked by queen on e8 (different file, rank, and diagonals)
-    val board = FenParser.parseBoard("8/4P3/8/8/8/8/8/7k").get
-    val result = GameController.completePromotion(
-      board, GameHistory.empty,
-      sq(File.E, Rank.R7), sq(File.E, Rank.R8),
-      PromotionPiece.Queen, Color.White
-    )
-    result should matchPattern { case _: MoveResult.Moved => }
-    result match
-      case MoveResult.Moved(newBoard, newHistory, _, _) =>
-        newBoard.pieceAt(sq(File.E, Rank.R8)) should be (Some(Piece(Color.White, PieceType.Queen)))
-        newBoard.pieceAt(sq(File.E, Rank.R7)) should be (None)
-        newHistory.moves should have length 1
-        newHistory.moves.head.promotionPiece should be (Some(PromotionPiece.Queen))
-      case _ => fail("Expected Moved")
-
-  test("completePromotion with rook underpromotion"):
-    // Black king on h1: not attacked by rook on e8 (different file and rank)
-    val board = FenParser.parseBoard("8/4P3/8/8/8/8/8/7k").get
-    val result = GameController.completePromotion(
-      board, GameHistory.empty,
-      sq(File.E, Rank.R7), sq(File.E, Rank.R8),
-      PromotionPiece.Rook, Color.White
-    )
-    result match
-      case MoveResult.Moved(newBoard, newHistory, _, _) =>
-        newBoard.pieceAt(sq(File.E, Rank.R8)) should be (Some(Piece(Color.White, PieceType.Rook)))
-        newHistory.moves.head.promotionPiece should be (Some(PromotionPiece.Rook))
-      case _ => fail("Expected Moved with Rook")
-
-  test("completePromotion with bishop underpromotion"):
-    val board = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val result = GameController.completePromotion(
-      board, GameHistory.empty,
-      sq(File.E, Rank.R7), sq(File.E, Rank.R8),
-      PromotionPiece.Bishop, Color.White
-    )
-    result match
-      case MoveResult.Moved(newBoard, newHistory, _, _) =>
-        newBoard.pieceAt(sq(File.E, Rank.R8)) should be (Some(Piece(Color.White, PieceType.Bishop)))
-        newHistory.moves.head.promotionPiece should be (Some(PromotionPiece.Bishop))
-      case _ => fail("Expected Moved with Bishop")
-
-  test("completePromotion with knight underpromotion"):
-    val board = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val result = GameController.completePromotion(
-      board, GameHistory.empty,
-      sq(File.E, Rank.R7), sq(File.E, Rank.R8),
-      PromotionPiece.Knight, Color.White
-    )
-    result match
-      case MoveResult.Moved(newBoard, newHistory, _, _) =>
-        newBoard.pieceAt(sq(File.E, Rank.R8)) should be (Some(Piece(Color.White, PieceType.Knight)))
-        newHistory.moves.head.promotionPiece should be (Some(PromotionPiece.Knight))
-      case _ => fail("Expected Moved with Knight")
-
-  test("completePromotion captures opponent piece"):
-    // Black king on h1: after white queen captures d8 queen, h1 king is safe (queen on d8 does not attack h1)
-    val board = FenParser.parseBoard("3q4/4P3/8/8/8/8/8/7k").get
-    val result = GameController.completePromotion(
-      board, GameHistory.empty,
-      sq(File.E, Rank.R7), sq(File.D, Rank.R8),
-      PromotionPiece.Queen, Color.White
-    )
-    result match
-      case MoveResult.Moved(newBoard, _, captured, _) =>
-        newBoard.pieceAt(sq(File.D, Rank.R8)) should be (Some(Piece(Color.White, PieceType.Queen)))
-        captured should be (Some(Piece(Color.Black, PieceType.Queen)))
-      case _ => fail("Expected Moved with captured piece")
-
-  test("completePromotion for black pawn to R1"):
-    val board = FenParser.parseBoard("8/8/8/8/4K3/8/4p3/8").get
-    val result = GameController.completePromotion(
-      board, GameHistory.empty,
-      sq(File.E, Rank.R2), sq(File.E, Rank.R1),
-      PromotionPiece.Knight, Color.Black
-    )
-    result match
-      case MoveResult.Moved(newBoard, newHistory, _, _) =>
-        newBoard.pieceAt(sq(File.E, Rank.R1)) should be (Some(Piece(Color.Black, PieceType.Knight)))
-        newHistory.moves.head.promotionPiece should be (Some(PromotionPiece.Knight))
-      case _ => fail("Expected Moved")
-
-  test("completePromotion evaluates check after promotion"):
-    val board = FenParser.parseBoard("3k4/4P3/8/8/8/8/8/8").get
-    val result = GameController.completePromotion(
-      board, GameHistory.empty,
-      sq(File.E, Rank.R7), sq(File.E, Rank.R8),
-      PromotionPiece.Queen, Color.White
-    )
-    result should matchPattern { case _: MoveResult.MovedInCheck => }
-
-  test("completePromotion full round-trip via processMove then completePromotion"):
-    // Black king on h1: not attacked by queen on e8
-    val board = FenParser.parseBoard("8/4P3/8/8/8/8/8/7k").get
-    GameController.processMove(board, GameHistory.empty, Color.White, "e7e8") match
-      case MoveResult.PromotionRequired(from, to, boardBefore, histBefore, _, turn) =>
-        val result = GameController.completePromotion(boardBefore, histBefore, from, to, PromotionPiece.Queen, turn)
-        result should matchPattern { case _: MoveResult.Moved => }
-        result match
-          case MoveResult.Moved(finalBoard, finalHistory, _, _) =>
-            finalBoard.pieceAt(sq(File.E, Rank.R8)) should be (Some(Piece(Color.White, PieceType.Queen)))
-            finalHistory.moves.head.promotionPiece should be (Some(PromotionPiece.Queen))
-          case _ => fail("Expected Moved")
-      case _ => fail("Expected PromotionRequired")
-
-  test("completePromotion results in checkmate when promotion delivers checkmate"):
-    // Black king a8, white pawn h7, white king b6.
-    // After h7→h8=Q: Qh8 attacks rank 8 putting Ka8 in check;
-    // a7 covered by Kb6, b7 covered by Kb6, b8 covered by Qh8 — no escape.
-    val board = FenParser.parseBoard("k7/7P/1K6/8/8/8/8/8").get
-    val result = GameController.completePromotion(
-      board, GameHistory.empty,
-      sq(File.H, Rank.R7), sq(File.H, Rank.R8),
-      PromotionPiece.Queen, Color.White
-    )
-    result should matchPattern { case MoveResult.Checkmate(_) => }
-    result match
-      case MoveResult.Checkmate(winner) => winner should be (Color.White)
-      case _ => fail("Expected Checkmate")
-
-  test("completePromotion results in stalemate when promotion stalemates opponent"):
-    // Black king a8, white pawn b7, white bishop c7, white king b6.
-    // After b7→b8=N: knight on b8 (doesn't check a8); a7 and b7 covered by Kb6;
-    // b8 defended by Bc7 so Ka8xb8 would walk into bishop — no legal moves.
-    val board = FenParser.parseBoard("k7/1PB5/1K6/8/8/8/8/8").get
-    val result = GameController.completePromotion(
-      board, GameHistory.empty,
-      sq(File.B, Rank.R7), sq(File.B, Rank.R8),
-      PromotionPiece.Knight, Color.White
-    )
-    result should be (MoveResult.Stalemate)
-
-  // ──── half-move clock propagation ────────────────────────────────────
-
-  test("processMove: non-pawn non-capture increments halfMoveClock"):
-    // g1f3 is a knight move — not a pawn, not a capture
-    processMove(Board.initial, GameHistory.empty, Color.White, "g1f3") match
-      case MoveResult.Moved(_, newHistory, _, _) =>
-        newHistory.halfMoveClock shouldBe 1
-      case other => fail(s"Expected Moved, got $other")
-
-  test("processMove: pawn move resets halfMoveClock to 0"):
-    processMove(Board.initial, GameHistory.empty, Color.White, "e2e4") match
-      case MoveResult.Moved(_, newHistory, _, _) =>
-        newHistory.halfMoveClock shouldBe 0
-      case other => fail(s"Expected Moved, got $other")
-
-  test("processMove: capture resets halfMoveClock to 0"):
-    // White pawn on e5, Black pawn on d6 — exd6 is a capture
-    val board = Board(Map(
-      sq(File.E, Rank.R5) -> Piece.WhitePawn,
-      sq(File.D, Rank.R6) -> Piece.BlackPawn,
-      sq(File.E, Rank.R1) -> Piece.WhiteKing,
-      sq(File.E, Rank.R8) -> Piece.BlackKing
-    ))
-    val history = GameHistory(halfMoveClock = 10)
-    processMove(board, history, Color.White, "e5d6") match
-      case MoveResult.Moved(_, newHistory, _, _) =>
-        newHistory.halfMoveClock shouldBe 0
-      case other => fail(s"Expected Moved, got $other")
-
-  test("processMove: clock carries from previous history on non-pawn non-capture"):
-    val history = GameHistory(halfMoveClock = 5)
-    processMove(Board.initial, history, Color.White, "g1f3") match
-      case MoveResult.Moved(_, newHistory, _, _) =>
-        newHistory.halfMoveClock shouldBe 6
-      case other => fail(s"Expected Moved, got $other")

modules/core/src/test/scala/de/nowchess/chess/engine/EngineTestHelpers.scala

@@ -0,0 +1,40 @@
+package de.nowchess.chess.engine
+
+import de.nowchess.api.board.{Board, Color}
+import de.nowchess.api.game.GameContext
+import de.nowchess.chess.observer.*
+import de.nowchess.io.fen.FenParser
+import de.nowchess.rules.sets.DefaultRules
+import scala.collection.mutable
+
+object EngineTestHelpers:
+
+  def makeEngine(): GameEngine =
+    new GameEngine(ruleSet = DefaultRules)
+
+  def makeEngineWithBoard(board: Board, turn: Color = Color.White): GameEngine =
+    GameEngine(initialContext = GameContext.initial.withBoard(board).withTurn(turn))
+
+  def loadFen(engine: GameEngine, fen: String): Unit =
+    engine.loadGame(FenParser, fen)
+
+  def captureEvents(engine: GameEngine): mutable.ListBuffer[GameEvent] =
+    val events = mutable.ListBuffer[GameEvent]()
+    engine.subscribe(new Observer { def onGameEvent(e: GameEvent): Unit = events += e })
+    events
+
+  class MockObserver extends Observer:
+    private val _events = mutable.ListBuffer[GameEvent]()
+
+    def events: mutable.ListBuffer[GameEvent] = _events
+    def eventCount: Int                       = _events.length
+    def hasEvent[T <: GameEvent](implicit ct: scala.reflect.ClassTag[T]): Boolean =
+      _events.exists(ct.runtimeClass.isInstance(_))
+    def getEvent[T <: GameEvent](implicit ct: scala.reflect.ClassTag[T]): Option[T] =
+      _events.collectFirst { case e: T => e }
+
+    override def onGameEvent(event: GameEvent): Unit =
+      _events += event
+
+    def clear(): Unit =
+      _events.clear()

modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineEdgeCasesTest.scala

@@ -1,214 +0,0 @@
-package de.nowchess.chess.engine
-
-import scala.collection.mutable
-import de.nowchess.api.board.{Board, Color}
-import de.nowchess.chess.logic.GameHistory
-import de.nowchess.chess.observer.{Observer, GameEvent, MoveExecutedEvent, CheckDetectedEvent, BoardResetEvent, InvalidMoveEvent}
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-/** Tests for GameEngine edge cases and uncovered paths */
-class GameEngineEdgeCasesTest extends AnyFunSuite with Matchers:
-
-  test("GameEngine handles empty input"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    engine.processUserInput("")
-    
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe an[InvalidMoveEvent]
-    val event = observer.events.head.asInstanceOf[InvalidMoveEvent]
-    event.reason should include("Please enter a valid move or command")
-
-  test("GameEngine processes quit command"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    engine.processUserInput("quit")
-    // Quit just returns, no events
-    observer.events.isEmpty shouldBe true
-
-  test("GameEngine processes q command (short form)"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    engine.processUserInput("q")
-    observer.events.isEmpty shouldBe true
-
-  test("GameEngine handles uppercase quit"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    engine.processUserInput("QUIT")
-    observer.events.isEmpty shouldBe true
-
-  test("GameEngine handles undo on empty history"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    engine.canUndo shouldBe false
-    engine.processUserInput("undo")
-    
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe an[InvalidMoveEvent]
-    val event = observer.events.head.asInstanceOf[InvalidMoveEvent]
-    event.reason should include("Nothing to undo")
-
-  test("GameEngine handles redo on empty redo history"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    engine.canRedo shouldBe false
-    engine.processUserInput("redo")
-    
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe an[InvalidMoveEvent]
-    val event = observer.events.head.asInstanceOf[InvalidMoveEvent]
-    event.reason should include("Nothing to redo")
-
-  test("GameEngine parses invalid move format"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    engine.processUserInput("invalid_move_format")
-    
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe an[InvalidMoveEvent]
-    val event = observer.events.head.asInstanceOf[InvalidMoveEvent]
-    event.reason should include("Invalid move format")
-
-  test("GameEngine handles lowercase input normalization"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    engine.processUserInput("  UNDO  ")  // With spaces and uppercase
-    
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe an[InvalidMoveEvent]  // No moves to undo yet
-
-  test("GameEngine preserves board state on invalid move"):
-    val engine = new GameEngine()
-    val initialBoard = engine.board
-    
-    engine.processUserInput("invalid")
-    
-    engine.board shouldBe initialBoard
-
-  test("GameEngine preserves turn on invalid move"):
-    val engine = new GameEngine()
-    val initialTurn = engine.turn
-    
-    engine.processUserInput("invalid")
-    
-    engine.turn shouldBe initialTurn
-
-  test("GameEngine undo with no commands available"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    // Make a valid move
-    engine.processUserInput("e2e4")
-    observer.events.clear()
-    
-    // Undo it
-    engine.processUserInput("undo")
-    
-    // Board should be reset
-    engine.board shouldBe Board.initial
-    engine.turn shouldBe Color.White
-
-  test("GameEngine redo after undo"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    engine.processUserInput("e2e4")
-    val boardAfterMove = engine.board
-    val turnAfterMove = engine.turn
-    observer.events.clear()
-    
-    engine.processUserInput("undo")
-    engine.processUserInput("redo")
-    
-    engine.board shouldBe boardAfterMove
-    engine.turn shouldBe turnAfterMove
-
-  test("GameEngine canUndo flag tracks state correctly"):
-    val engine = new GameEngine()
-    
-    engine.canUndo shouldBe false
-    engine.processUserInput("e2e4")
-    engine.canUndo shouldBe true
-    engine.processUserInput("undo")
-    engine.canUndo shouldBe false
-
-  test("GameEngine canRedo flag tracks state correctly"):
-    val engine = new GameEngine()
-    
-    engine.canRedo shouldBe false
-    engine.processUserInput("e2e4")
-    engine.canRedo shouldBe false
-    engine.processUserInput("undo")
-    engine.canRedo shouldBe true
-
-  test("GameEngine command history is accessible"):
-    val engine = new GameEngine()
-    
-    engine.commandHistory.isEmpty shouldBe true
-    engine.processUserInput("e2e4")
-    engine.commandHistory.size shouldBe 1
-
-  test("GameEngine processes multiple moves in sequence"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    observer.events.clear()
-    
-    engine.processUserInput("e2e4")
-    engine.processUserInput("e7e5")
-    
-    observer.events.size shouldBe 2
-    engine.commandHistory.size shouldBe 2
-
-  test("GameEngine can undo multiple moves"):
-    val engine = new GameEngine()
-    
-    engine.processUserInput("e2e4")
-    engine.processUserInput("e7e5")
-    
-    engine.processUserInput("undo")
-    engine.turn shouldBe Color.Black
-    
-    engine.processUserInput("undo")
-    engine.turn shouldBe Color.White
-
-  test("GameEngine thread-safe operations"):
-    val engine = new GameEngine()
-    
-    // Access from synchronized methods
-    val board = engine.board
-    val history = engine.history
-    val turn = engine.turn
-    val canUndo = engine.canUndo
-    val canRedo = engine.canRedo
-    
-    board shouldBe Board.initial
-    canUndo shouldBe false
-    canRedo shouldBe false
-
-
-private class MockObserver extends Observer:
-  val events = mutable.ListBuffer[GameEvent]()
-  
-  override def onGameEvent(event: GameEvent): Unit =
-    events += event

modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineGameEndingTest.scala

@@ -1,9 +1,9 @@
 package de.nowchess.chess.engine
 
 import scala.collection.mutable
-import de.nowchess.api.board.{Board, Color}
-import de.nowchess.chess.logic.GameHistory
-import de.nowchess.chess.observer.{Observer, GameEvent, CheckDetectedEvent, CheckmateEvent, StalemateEvent}
+import de.nowchess.api.board.Color
+import de.nowchess.api.game.DrawReason
+import de.nowchess.chess.observer.{CheckDetectedEvent, CheckmateEvent, DrawEvent, GameEvent, Observer}
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
 
@@ -11,83 +11,84 @@ import org.scalatest.matchers.should.Matchers
 class GameEngineGameEndingTest extends AnyFunSuite with Matchers:
 
   test("GameEngine handles Checkmate (Fool's Mate)"):
-    val engine = new GameEngine()
+    val engine   = new GameEngine()
     val observer = new EndingMockObserver()
     engine.subscribe(observer)
-    
+
     // Play Fool's mate
     engine.processUserInput("f2f3")
     engine.processUserInput("e7e5")
     engine.processUserInput("g2g4")
-    
+
     observer.events.clear()
     engine.processUserInput("d8h4")
-    
-    // Verify CheckmateEvent
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe a[CheckmateEvent]
-    
-    val event = observer.events.head.asInstanceOf[CheckmateEvent]
+
+    // Verify CheckmateEvent (engine also fires MoveExecutedEvent before CheckmateEvent)
+    observer.events.last shouldBe a[CheckmateEvent]
+
+    val event = observer.events.collectFirst { case e: CheckmateEvent => e }.get
     event.winner shouldBe Color.Black
-    
-    // Board should be reset after checkmate
-    engine.board shouldBe Board.initial
-    engine.turn shouldBe Color.White
 
   test("GameEngine handles check detection"):
-    val engine = new GameEngine()
+    val engine   = new GameEngine()
     val observer = new EndingMockObserver()
     engine.subscribe(observer)
-    
+
     // Play a simple check
     engine.processUserInput("e2e4")
     engine.processUserInput("e7e5")
     engine.processUserInput("f1c4")
     engine.processUserInput("g8f6")
-    
+
     observer.events.clear()
     engine.processUserInput("c4f7") // Check!
-    
+
     val checkEvents = observer.events.collect { case e: CheckDetectedEvent => e }
     checkEvents.size shouldBe 1
-    checkEvents.head.turn shouldBe Color.Black // Black is now in check
-    
+    checkEvents.head.context.turn shouldBe Color.Black // Black is now in check
+
   // Shortest known stalemate is 19 moves. Here is a faster one:
   // e3 a5 Qh5 Ra6 Qxa5 h5 h4 Rah6 Qxc7 f6 Qxd7+ Kf7 Qxb7 Qd3 Qxb8 Qh7 Qxc8 Kg6 Qe6
   // Wait, let's just use Sam Loyd's 10-move stalemate:
   // 1. e3 a5 2. Qh5 Ra6 3. Qxa5 h5 4. h4 Rah6 5. Qxc7 f6 6. Qxd7+ Kf7 7. Qxb7 Qd3 8. Qxb8 Qh7 9. Qxc8 Kg6 10. Qe6
   test("GameEngine handles Stalemate via 10-move known sequence"):
-    val engine = new GameEngine()
+    val engine   = new GameEngine()
     val observer = new EndingMockObserver()
     engine.subscribe(observer)
-    
+
     val moves = List(
-      "e2e3", "a7a5",
-      "d1h5", "a8a6",
-      "h5a5", "h7h5",
-      "h2h4", "a6h6",
-      "a5c7", "f7f6",
-      "c7d7", "e8f7",
-      "d7b7", "d8d3",
-      "b7b8", "d3h7",
-      "b8c8", "f7g6",
-      "c8e6"
+      "e2e3",
+      "a7a5",
+      "d1h5",
+      "a8a6",
+      "h5a5",
+      "h7h5",
+      "h2h4",
+      "a6h6",
+      "a5c7",
+      "f7f6",
+      "c7d7",
+      "e8f7",
+      "d7b7",
+      "d8d3",
+      "b7b8",
+      "d3h7",
+      "b8c8",
+      "f7g6",
+      "c8e6",
     )
-    
+
     moves.dropRight(1).foreach(engine.processUserInput)
-    
+
     observer.events.clear()
     engine.processUserInput(moves.last)
-    
-    val stalemateEvents = observer.events.collect { case e: StalemateEvent => e }
-    stalemateEvents.size shouldBe 1
-    
-    // Board should be reset after stalemate
-    engine.board shouldBe Board.initial
-    engine.turn shouldBe Color.White
+
+    val drawEvents = observer.events.collect { case e: DrawEvent => e }
+    drawEvents.size shouldBe 1
+    drawEvents.head.reason shouldBe DrawReason.Stalemate
 
 private class EndingMockObserver extends Observer:
   val events = mutable.ListBuffer[GameEvent]()
-  
+
   override def onGameEvent(event: GameEvent): Unit =
-    events += event
+    events += event

modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineHandleFailedMoveTest.scala

@@ -1,110 +0,0 @@
-package de.nowchess.chess.engine
-
-import scala.collection.mutable
-import de.nowchess.api.board.{Board, Color}
-import de.nowchess.chess.logic.GameHistory
-import de.nowchess.chess.observer.{Observer, GameEvent, InvalidMoveEvent}
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-/** Tests to maximize handleFailedMove coverage */
-class GameEngineHandleFailedMoveTest extends AnyFunSuite with Matchers:
-
-  test("GameEngine handles InvalidFormat error type"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    engine.processUserInput("not_a_valid_move_format")
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe an[InvalidMoveEvent]
-    val msg1 = observer.events.head.asInstanceOf[InvalidMoveEvent].reason
-    msg1 should include("Invalid move format")
-
-  test("GameEngine handles NoPiece error type"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    engine.processUserInput("h3h4")
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe an[InvalidMoveEvent]
-    val msg2 = observer.events.head.asInstanceOf[InvalidMoveEvent].reason
-    msg2 should include("No piece on that square")
-
-  test("GameEngine handles WrongColor error type"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    engine.processUserInput("e2e4")  // White move
-    observer.events.clear()
-    
-    engine.processUserInput("a1b2")  // Try to move black's rook position with white's move (wrong color)
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe an[InvalidMoveEvent]
-    val msg3 = observer.events.head.asInstanceOf[InvalidMoveEvent].reason
-    msg3 should include("That is not your piece")
-
-  test("GameEngine handles IllegalMove error type"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    engine.processUserInput("e2e1")  // Try pawn backward
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe an[InvalidMoveEvent]
-    val msg4 = observer.events.head.asInstanceOf[InvalidMoveEvent].reason
-    msg4 should include("Illegal move")
-
-  test("GameEngine invalid move message for InvalidFormat"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    engine.processUserInput("xyz123")
-    val event = observer.events.head.asInstanceOf[InvalidMoveEvent]
-    event.reason should include("coordinate notation")
-
-  test("GameEngine invalid move message for NoPiece"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    engine.processUserInput("a3a4")  // a3 is empty
-    val event = observer.events.head.asInstanceOf[InvalidMoveEvent]
-    event.reason should include("No piece")
-
-  test("GameEngine invalid move message for WrongColor"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    engine.processUserInput("e2e4")
-    observer.events.clear()
-    
-    engine.processUserInput("e4e5")  // e4 has white pawn, it's black's turn
-    val event = observer.events.head.asInstanceOf[InvalidMoveEvent]
-    event.reason should include("not your piece")
-
-  test("GameEngine invalid move message for IllegalMove"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    engine.processUserInput("e2e1")  // Pawn can't move backward
-    val event = observer.events.head.asInstanceOf[InvalidMoveEvent]
-    event.reason should include("Illegal move")
-
-  test("GameEngine board unchanged after each type of invalid move"):
-    val engine = new GameEngine()
-    val initial = engine.board
-    
-    engine.processUserInput("invalid")
-    engine.board shouldBe initial
-    
-    engine.processUserInput("h3h4")
-    engine.board shouldBe initial
-    
-    engine.processUserInput("e2e1")
-    engine.board shouldBe initial

modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineIntegrationTest.scala

@@ -0,0 +1,177 @@
+package de.nowchess.chess.engine
+
+import de.nowchess.api.board.{Board, Color, File, PieceType, Rank, Square}
+import de.nowchess.api.game.GameContext
+import de.nowchess.api.move.{Move, MoveType, PromotionPiece}
+import de.nowchess.chess.observer.{GameEvent, InvalidMoveEvent, MoveRedoneEvent, Observer}
+import de.nowchess.io.GameContextImport
+import de.nowchess.rules.RuleSet
+import de.nowchess.rules.sets.DefaultRules
+import org.scalatest.funsuite.AnyFunSuite
+import org.scalatest.matchers.should.Matchers
+
+class GameEngineIntegrationTest extends AnyFunSuite with Matchers:
+
+  private def sq(alg: String): Square =
+    Square.fromAlgebraic(alg).getOrElse(fail(s"Invalid square in test: $alg"))
+
+  private def captureEvents(engine: GameEngine): collection.mutable.ListBuffer[GameEvent] =
+    val events = collection.mutable.ListBuffer[GameEvent]()
+    engine.subscribe((event: GameEvent) => events += event)
+    events
+
+  test("accessors expose redo availability and command history"):
+    val engine = new GameEngine()
+
+    engine.canRedo shouldBe false
+    engine.commandHistory shouldBe empty
+
+    engine.processUserInput("e2e4")
+    engine.commandHistory.nonEmpty shouldBe true
+
+  test("processUserInput handles undo redo empty and malformed commands"):
+    val engine = new GameEngine()
+    val events = captureEvents(engine)
+
+    engine.processUserInput("")
+    engine.processUserInput("oops")
+    engine.processUserInput("undo")
+    engine.processUserInput("redo")
+
+    events.count { case _: InvalidMoveEvent => true; case _ => false } should be >= 3
+
+  test("processUserInput emits Illegal move for syntactically valid but illegal target"):
+    val engine = new GameEngine()
+    val events = captureEvents(engine)
+
+    engine.processUserInput("e2e5")
+
+    events.exists {
+      case InvalidMoveEvent(_, reason) => reason.contains("Illegal move")
+      case _                           => false
+    } shouldBe true
+
+  test("loadGame returns Left when importer fails"):
+
+    val engine = new GameEngine()
+    val failingImporter = new GameContextImport:
+      def importGameContext(input: String): Either[String, GameContext] = Left("boom")
+
+    engine.loadGame(failingImporter, "ignored") shouldBe Left("boom")
+
+  test("loadPosition replaces context clears history and notifies reset"):
+    val engine = new GameEngine()
+    val events = captureEvents(engine)
+
+    engine.processUserInput("e2e4")
+    val target = GameContext.initial.withTurn(Color.Black)
+    engine.loadPosition(target)
+
+    engine.context shouldBe target
+    engine.commandHistory shouldBe empty
+    events.lastOption.exists { case _: de.nowchess.chess.observer.BoardResetEvent => true; case _ => false } shouldBe true
+
+  test("redo event includes captured piece description when replaying a capture"):
+    val engine = new GameEngine()
+    val events = captureEvents(engine)
+
+    EngineTestHelpers.loadFen(engine, "4k3/8/8/8/8/8/4K3/R6r w - - 0 1")
+    events.clear()
+
+    engine.processUserInput("a1h1")
+    engine.processUserInput("undo")
+    engine.processUserInput("redo")
+
+    val redo = events.collectFirst { case e: MoveRedoneEvent => e }
+    redo.flatMap(_.capturedPiece) shouldBe Some("Black Rook")
+
+  test("loadGame replay handles promotion moves when pending promotion exists"):
+    val promotionMove = Move(sq("e2"), sq("e8"), MoveType.Promotion(PromotionPiece.Queen))
+
+    val permissiveRules = new RuleSet:
+      def candidateMoves(context: GameContext)(square: Square): List[Move] = legalMoves(context)(square)
+      def legalMoves(context: GameContext)(square: Square): List[Move] =
+        if square == sq("e2") then List(promotionMove) else List.empty
+      def allLegalMoves(context: GameContext): List[Move]          = List(promotionMove)
+      def isCheck(context: GameContext): Boolean                   = false
+      def isCheckmate(context: GameContext): Boolean               = false
+      def isStalemate(context: GameContext): Boolean               = false
+      def isInsufficientMaterial(context: GameContext): Boolean    = false
+      def isFiftyMoveRule(context: GameContext): Boolean           = false
+      def isThreefoldRepetition(context: GameContext): Boolean     = false
+      def applyMove(context: GameContext)(move: Move): GameContext = DefaultRules.applyMove(context)(move)
+
+    val engine = new GameEngine(ruleSet = permissiveRules)
+    val importer = new GameContextImport:
+      def importGameContext(input: String): Either[String, GameContext] =
+        Right(GameContext.initial.copy(moves = List(promotionMove)))
+
+    engine.loadGame(importer, "ignored") shouldBe Right(())
+    engine.context.moves.lastOption shouldBe Some(promotionMove)
+
+  test("loadGame replay restores previous context when promotion cannot be completed"):
+    val promotionMove = Move(sq("e2"), sq("e8"), MoveType.Promotion(PromotionPiece.Queen))
+    val noLegalMoves = new RuleSet:
+      def candidateMoves(context: GameContext)(square: Square): List[Move] = List.empty
+      def legalMoves(context: GameContext)(square: Square): List[Move]     = List.empty
+      def allLegalMoves(context: GameContext): List[Move]                  = List.empty
+      def isCheck(context: GameContext): Boolean                           = false
+      def isCheckmate(context: GameContext): Boolean                       = false
+      def isStalemate(context: GameContext): Boolean                       = false
+      def isInsufficientMaterial(context: GameContext): Boolean            = false
+      def isFiftyMoveRule(context: GameContext): Boolean                   = false
+      def isThreefoldRepetition(context: GameContext): Boolean             = false
+      def applyMove(context: GameContext)(move: Move): GameContext         = context
+
+    val engine = new GameEngine(ruleSet = noLegalMoves)
+    engine.processUserInput("e2e4")
+    val saved = engine.context
+
+    val importer = new GameContextImport:
+      def importGameContext(input: String): Either[String, GameContext] =
+        Right(GameContext.initial.copy(moves = List(promotionMove)))
+
+    val result = engine.loadGame(importer, "ignored")
+
+    result.isLeft shouldBe true
+    result.left.toOption.get should include("Promotion required")
+    engine.context shouldBe saved
+
+  test("loadGame replay executes non-promotion moves through default replay branch"):
+    val normalMove = Move(sq("e2"), sq("e4"), MoveType.Normal())
+    val engine     = new GameEngine()
+
+    engine.replayMoves(List(normalMove), engine.context) shouldBe Right(())
+    engine.context.moves.lastOption shouldBe Some(normalMove)
+
+  test("replayMoves skips later moves after the first move triggers an error"):
+    val engine           = new GameEngine()
+    val saved            = engine.context
+    val illegalPromotion = Move(sq("e2"), sq("e1"), MoveType.Promotion(PromotionPiece.Queen))
+    val trailingMove     = Move(sq("e2"), sq("e4"))
+
+    engine.replayMoves(List(illegalPromotion, trailingMove), saved) shouldBe Left("Promotion required for move e2e1")
+    engine.context shouldBe saved
+
+  test("normalMoveNotation handles missing source piece"):
+    val engine = new GameEngine()
+    val result = engine.normalMoveNotation(Move(sq("e3"), sq("e4")), Board.initial, isCapture = false)
+
+    result shouldBe "e4"
+
+  test("pieceNotation default branch returns empty string"):
+    val engine = new GameEngine()
+    val result = engine.pieceNotation(PieceType.Pawn)
+
+    result shouldBe ""
+
+  test("observerCount reflects subscribe and unsubscribe operations"):
+    val engine = new GameEngine()
+    val observer = new Observer:
+      def onGameEvent(event: GameEvent): Unit = ()
+
+    engine.observerCount shouldBe 0
+    engine.subscribe(observer)
+    engine.observerCount shouldBe 1
+    engine.unsubscribe(observer)
+    engine.observerCount shouldBe 0

modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineInvalidMovesTest.scala

@@ -1,114 +0,0 @@
-package de.nowchess.chess.engine
-
-import scala.collection.mutable
-import de.nowchess.api.board.{Board, Color}
-import de.nowchess.chess.logic.GameHistory
-import de.nowchess.chess.observer.{Observer, GameEvent, InvalidMoveEvent, MoveExecutedEvent}
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-/** Tests for GameEngine invalid move handling via handleFailedMove */
-class GameEngineInvalidMovesTest extends AnyFunSuite with Matchers:
-
-  test("GameEngine handles no piece at source square"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    // Try to move from h1 which may be empty or not have our piece
-    // We'll try from a clearly empty square
-    engine.processUserInput("h1h2")
-    
-    // Should get an InvalidMoveEvent about NoPiece
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe an[InvalidMoveEvent]
-
-  test("GameEngine handles moving wrong color piece"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    // White moves first
-    engine.processUserInput("e2e4")
-    observer.events.clear()
-    
-    // White tries to move again (should fail - it's black's turn)
-    // But we need to try a move that looks legal but has wrong color
-    // This is hard to test because we'd need to be black and move white's piece
-    // Let's skip this for now and focus on testable cases
-    
-    // Actually, let's try moving a square that definitely has the wrong piece
-    // Move a white pawn as black by reaching that position
-    engine.processUserInput("e7e5")
-    observer.events.clear()
-    
-    // Now try to move white's e4 pawn as black (it's black's turn but e4 is white)
-    engine.processUserInput("e4e5")
-    
-    observer.events.size shouldBe 1
-    val event = observer.events.head
-    event shouldBe an[InvalidMoveEvent]
-
-  test("GameEngine handles illegal move"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    // A pawn can't move backward
-    engine.processUserInput("e2e1")
-    
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe an[InvalidMoveEvent]
-    val event = observer.events.head.asInstanceOf[InvalidMoveEvent]
-    event.reason should include("Illegal move")
-
-  test("GameEngine handles pawn trying to move 3 squares"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    // Pawn can only move 1 or 2 squares on first move, not 3
-    engine.processUserInput("e2e5")
-    
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe an[InvalidMoveEvent]
-
-  test("GameEngine handles moving from empty square"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    // h3 is empty in starting position
-    engine.processUserInput("h3h4")
-    
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe an[InvalidMoveEvent]
-    val event = observer.events.head.asInstanceOf[InvalidMoveEvent]
-    event.reason should include("No piece on that square")
-
-  test("GameEngine processes valid move after invalid attempt"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    // Try invalid move
-    engine.processUserInput("h3h4")
-    observer.events.clear()
-    
-    // Make valid move
-    engine.processUserInput("e2e4")
-    
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe an[MoveExecutedEvent]
-
-  test("GameEngine maintains state after failed move attempt"):
-    val engine = new GameEngine()
-    val initialTurn = engine.turn
-    val initialBoard = engine.board
-    
-    // Try invalid move
-    engine.processUserInput("h3h4")
-    
-    // State should not change
-    engine.turn shouldBe initialTurn
-    engine.board shouldBe initialBoard

modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineLoadGameTest.scala

@@ -0,0 +1,43 @@
+package de.nowchess.chess.engine
+
+import scala.collection.mutable
+import de.nowchess.api.board.{Board, Color}
+import de.nowchess.api.game.GameContext
+import de.nowchess.chess.observer.{GameEvent, Observer, PgnLoadedEvent}
+import de.nowchess.io.pgn.PgnParser
+import de.nowchess.io.fen.FenParser
+import de.nowchess.io.pgn.PgnExporter
+import de.nowchess.io.fen.FenExporter
+import org.scalatest.funsuite.AnyFunSuite
+import org.scalatest.matchers.should.Matchers
+
+class GameEngineLoadGameTest extends AnyFunSuite with Matchers:
+
+  test("loadGame with PgnParser: loads valid PGN and enables undo/redo"):
+    val engine = new GameEngine()
+    val pgn    = "[Event \"Test\"]\n\n1. e4 e5\n"
+    val result = engine.loadGame(PgnParser, pgn)
+    result shouldBe Right(())
+    engine.context.moves.size shouldBe 2
+    engine.canUndo shouldBe true
+
+  test("loadGame with FenParser: loads position without replaying moves"):
+    val engine = new GameEngine()
+    val fen    = "8/4P3/4k3/8/8/8/8/8 w - - 0 1"
+    val result = engine.loadGame(FenParser, fen)
+    result shouldBe Right(())
+    engine.context.moves.isEmpty shouldBe true
+    engine.canUndo shouldBe false
+
+  test("exportGame with PgnExporter: exports current game as PGN"):
+    val engine = new GameEngine()
+    engine.processUserInput("e2e4")
+    engine.processUserInput("e7e5")
+    val pgn = engine.exportGame(PgnExporter)
+    pgn.contains("e4") shouldBe true
+    pgn.contains("e5") shouldBe true
+
+  private class MockObserver extends Observer:
+    val events = mutable.ListBuffer[GameEvent]()
+    override def onGameEvent(event: GameEvent): Unit =
+      events += event

modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineLoadPgnTest.scala

@@ -1,165 +0,0 @@
-package de.nowchess.chess.engine
-
-import scala.collection.mutable
-import de.nowchess.api.board.{Board, Color}
-import de.nowchess.chess.logic.GameHistory
-import de.nowchess.chess.observer.*
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class GameEngineLoadPgnTest extends AnyFunSuite with Matchers:
-
-  private class EventCapture extends Observer:
-    val events: mutable.Buffer[GameEvent] = mutable.Buffer.empty
-    def onGameEvent(event: GameEvent): Unit = events += event
-    def lastEvent: GameEvent = events.last
-
-  // ── loadPgn happy path ────────────────────────────────────────────────────
-
-  test("loadPgn: valid PGN returns Right and updates board/history"):
-    val engine = new GameEngine()
-    val pgn =
-      """[Event "Test"]
-
-1. e4 e5
-"""
-    val result = engine.loadPgn(pgn)
-    result shouldBe Right(())
-    engine.history.moves.length shouldBe 2
-    engine.turn shouldBe Color.White
-
-  test("loadPgn: emits PgnLoadedEvent on success"):
-    val engine = new GameEngine()
-    val cap    = new EventCapture()
-    engine.subscribe(cap)
-    val pgn = "[Event \"T\"]\n\n1. e4 e5\n"
-    engine.loadPgn(pgn)
-    cap.events.last shouldBe a[PgnLoadedEvent]
-
-  test("loadPgn: after load canUndo is true and canRedo is false"):
-    val engine = new GameEngine()
-    val pgn = "[Event \"T\"]\n\n1. e4 e5\n"
-    engine.loadPgn(pgn) shouldBe Right(())
-    engine.canUndo shouldBe true
-    engine.canRedo shouldBe false
-
-  test("loadPgn: undo works after loading PGN"):
-    val engine = new GameEngine()
-    val cap    = new EventCapture()
-    engine.subscribe(cap)
-    val pgn = "[Event \"T\"]\n\n1. e4 e5\n"
-    engine.loadPgn(pgn)
-    cap.events.clear()
-    engine.undo()
-    cap.events.last shouldBe a[MoveUndoneEvent]
-    engine.history.moves.length shouldBe 1
-
-  test("loadPgn: undo then redo restores position after PGN load"):
-    val engine = new GameEngine()
-    val cap    = new EventCapture()
-    engine.subscribe(cap)
-    val pgn = "[Event \"T\"]\n\n1. e4 e5\n"
-    engine.loadPgn(pgn)
-    val boardAfterLoad = engine.board
-    engine.undo()
-    engine.redo()
-    cap.events.last shouldBe a[MoveRedoneEvent]
-    engine.board shouldBe boardAfterLoad
-    engine.history.moves.length shouldBe 2
-
-  test("loadPgn: longer game loads all moves into command history"):
-    val engine = new GameEngine()
-    val pgn =
-      """[Event "Ruy Lopez"]
-
-1. e4 e5 2. Nf3 Nc6 3. Bb5 a6
-"""
-    engine.loadPgn(pgn) shouldBe Right(())
-    engine.history.moves.length shouldBe 6
-    engine.commandHistory.length shouldBe 6
-
-  test("loadPgn: invalid PGN returns Left and does not change state"):
-    val engine  = new GameEngine()
-    val initial = engine.board
-    val result  = engine.loadPgn("[Event \"T\"]\n\n1. Qd4\n")
-    result.isLeft shouldBe true
-    // state is reset to initial (reset happens before replay, which fails)
-    engine.history.moves shouldBe empty
-
-  // ── undo/redo notation events ─────────────────────────────────────────────
-
-  test("undo emits MoveUndoneEvent with pgnNotation"):
-    val engine = new GameEngine()
-    val cap    = new EventCapture()
-    engine.subscribe(cap)
-    engine.processUserInput("e2e4")
-    cap.events.clear()
-    engine.undo()
-    cap.events.last shouldBe a[MoveUndoneEvent]
-    val evt = cap.events.last.asInstanceOf[MoveUndoneEvent]
-    evt.pgnNotation should not be empty
-    evt.pgnNotation shouldBe "e4"  // pawn to e4
-
-  test("redo emits MoveRedoneEvent with pgnNotation"):
-    val engine = new GameEngine()
-    val cap    = new EventCapture()
-    engine.subscribe(cap)
-    engine.processUserInput("e2e4")
-    engine.undo()
-    cap.events.clear()
-    engine.redo()
-    cap.events.last shouldBe a[MoveRedoneEvent]
-    val evt = cap.events.last.asInstanceOf[MoveRedoneEvent]
-    evt.pgnNotation should not be empty
-    evt.pgnNotation shouldBe "e4"
-
-  test("undo emits MoveUndoneEvent with empty notation when history is empty (after checkmate reset)"):
-    // Simulate state where canUndo=true but currentHistory is empty (board reset on checkmate).
-    // We achieve this by examining the branch: provide a MoveCommand with empty history saved.
-    // The simplest proxy: undo a move that reset history (stalemate/checkmate). We'll
-    // use a contrived engine state by direct command manipulation — instead, just verify
-    // that after a normal move-and-undo the notation is present; the empty-history branch
-    // is exercised internally when gameEnd resets state. We cover it via a castling undo.
-    val engine = new GameEngine()
-    val cap    = new EventCapture()
-    engine.subscribe(cap)
-    // Play moves that let white castle kingside: e4 e5 Nf3 Nc6 Bc4 Bc5 O-O
-    engine.processUserInput("e2e4")
-    engine.processUserInput("e7e5")
-    engine.processUserInput("g1f3")
-    engine.processUserInput("b8c6")
-    engine.processUserInput("f1c4")
-    engine.processUserInput("f8c5")
-    engine.processUserInput("e1g1")  // white castles kingside
-    cap.events.clear()
-    engine.undo()
-    val evt = cap.events.last.asInstanceOf[MoveUndoneEvent]
-    evt.pgnNotation shouldBe "O-O"
-
-  test("redo emits MoveRedoneEvent with from/to squares and capturedPiece"):
-    val engine = new GameEngine()
-    val cap    = new EventCapture()
-    engine.subscribe(cap)
-    // White builds a capture on the a-file: b4, ... a6, b5, ... h6, bxa6
-    engine.processUserInput("b2b4")
-    engine.processUserInput("a7a6")
-    engine.processUserInput("b4b5")
-    engine.processUserInput("h7h6")
-    engine.processUserInput("b5a6")  // white pawn captures black pawn
-    engine.undo()
-    cap.events.clear()
-    engine.redo()
-    val evt = cap.events.last.asInstanceOf[MoveRedoneEvent]
-    evt.fromSquare shouldBe "b5"
-    evt.toSquare   shouldBe "a6"
-    evt.capturedPiece.isDefined shouldBe true
-
-  test("loadPgn: clears previous game state before loading"):
-    val engine = new GameEngine()
-    engine.processUserInput("e2e4")
-    val pgn = "[Event \"T\"]\n\n1. d4 d5\n"
-    engine.loadPgn(pgn) shouldBe Right(())
-    // First move should be d4, not e4
-    engine.history.moves.head.to shouldBe de.nowchess.api.board.Square(
-      de.nowchess.api.board.File.D, de.nowchess.api.board.Rank.R4
-    )

modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineNotationTest.scala

@@ -0,0 +1,128 @@
+package de.nowchess.chess.engine
+
+import de.nowchess.api.board.{Board, Color, File, Rank, Square}
+import de.nowchess.api.game.GameContext
+import de.nowchess.api.move.PromotionPiece
+import de.nowchess.io.fen.FenParser
+import de.nowchess.chess.observer.*
+import org.scalatest.funsuite.AnyFunSuite
+import org.scalatest.matchers.should.Matchers
+
+/** Tests that exercise moveToPgn branches not covered by other test files:
+  *   - CastleQueenside (line 223)
+  *   - EnPassant notation (lines 224-225) and computeCaptured EnPassant (lines 254-255)
+  *   - Promotion(Bishop) notation (line 230)
+  *   - King normal move notation (line 246)
+  */
+class GameEngineNotationTest extends AnyFunSuite with Matchers:
+
+  private def captureEvents(engine: GameEngine): collection.mutable.ListBuffer[GameEvent] =
+    val buf = collection.mutable.ListBuffer[GameEvent]()
+    engine.subscribe(new Observer { def onGameEvent(e: GameEvent): Unit = buf += e })
+    buf
+
+  // ── Queenside castling (line 223) ──────────────────────────────────
+
+  test("undo after queenside castling emits MoveUndoneEvent with O-O-O notation"):
+    // FEN: White king on e1, queenside rook on a1, b1/c1/d1 clear, black king away
+    val board = FenParser.parseBoard("k7/8/8/8/8/8/8/R3K3").get
+    // Castling rights: white queen-side only (no king-side rook present)
+    val castlingRights = de.nowchess.api.board.CastlingRights(
+      whiteKingSide = false,
+      whiteQueenSide = true,
+      blackKingSide = false,
+      blackQueenSide = false,
+    )
+    val ctx = GameContext.initial
+      .withBoard(board)
+      .withTurn(Color.White)
+      .withCastlingRights(castlingRights)
+
+    val engine = new GameEngine(ctx)
+    val events = captureEvents(engine)
+
+    // White castles queenside: e1c1
+    engine.processUserInput("e1c1")
+    events.exists { case _: MoveExecutedEvent => true; case _ => false } should be(true)
+
+    events.clear()
+    engine.undo()
+
+    val evt = events.collect { case e: MoveUndoneEvent => e }.head
+    evt.pgnNotation shouldBe "O-O-O"
+
+  // ── En passant notation + computeCaptured (lines 224-225, 254-255) ─
+
+  test("undo after en passant emits MoveUndoneEvent with file-x-destination notation"):
+    // White pawn on e5, black pawn on d5 (just double-pushed), en passant square d6
+    val board    = FenParser.parseBoard("k7/8/8/3pP3/8/8/8/7K").get
+    val epSquare = Square.fromAlgebraic("d6")
+    val ctx = GameContext.initial
+      .withBoard(board)
+      .withTurn(Color.White)
+      .withEnPassantSquare(epSquare)
+      .withCastlingRights(de.nowchess.api.board.CastlingRights(false, false, false, false))
+
+    val engine = new GameEngine(ctx)
+    val events = captureEvents(engine)
+
+    // White pawn on e5 captures en passant to d6
+    engine.processUserInput("e5d6")
+    events.exists { case _: MoveExecutedEvent => true; case _ => false } should be(true)
+
+    // Verify the captured pawn was found (computeCaptured EnPassant branch)
+    val moveEvt = events.collect { case e: MoveExecutedEvent => e }.head
+    moveEvt.capturedPiece shouldBe defined
+    moveEvt.capturedPiece.get should include("Black")
+
+    events.clear()
+    engine.undo()
+
+    val undoEvt = events.collect { case e: MoveUndoneEvent => e }.head
+    undoEvt.pgnNotation shouldBe "exd6"
+
+  // ── Bishop underpromotion notation (line 230) ──────────────────────
+
+  test("undo after bishop underpromotion emits MoveUndoneEvent with =B notation"):
+    // Extra white pawn on h2 ensures K+B+P vs K — sufficient material, so draw is not triggered
+    val board = FenParser.parseBoard("8/4P3/8/8/8/8/k6P/7K").get
+    val ctx = GameContext.initial
+      .withBoard(board)
+      .withTurn(Color.White)
+      .withCastlingRights(de.nowchess.api.board.CastlingRights(false, false, false, false))
+
+    val engine = new GameEngine(ctx)
+    val events = captureEvents(engine)
+
+    engine.processUserInput("e7e8")
+    engine.completePromotion(PromotionPiece.Bishop)
+
+    events.clear()
+    engine.undo()
+
+    val evt = events.collect { case e: MoveUndoneEvent => e }.head
+    evt.pgnNotation shouldBe "e8=B"
+
+  // ── King normal move notation (line 246) ───────────────────────────
+
+  test("undo after king move emits MoveUndoneEvent with K notation"):
+    // White king on e1, white rook on h1 — K+R vs K ensures sufficient material after the king move
+    val board = FenParser.parseBoard("k7/8/8/8/8/8/8/4K2R").get
+    val ctx = GameContext.initial
+      .withBoard(board)
+      .withTurn(Color.White)
+      .withCastlingRights(de.nowchess.api.board.CastlingRights(false, false, false, false))
+
+    val engine = new GameEngine(ctx)
+    val events = captureEvents(engine)
+
+    // King moves e1 -> f1
+    engine.processUserInput("e1f1")
+    events.exists { case _: MoveExecutedEvent => true; case _ => false } should be(true)
+
+    events.clear()
+    engine.undo()
+
+    val evt = events.collect { case e: MoveUndoneEvent => e }.head
+    evt.pgnNotation should startWith("K")
+    evt.pgnNotation should include("f1")

modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineOutcomesTest.scala

@@ -0,0 +1,295 @@
+package de.nowchess.chess.engine
+
+import de.nowchess.api.board.Color
+import de.nowchess.api.game.{DrawReason, GameResult}
+import de.nowchess.chess.observer.*
+import org.scalatest.funsuite.AnyFunSuite
+import org.scalatest.matchers.should.Matchers
+
+class GameEngineOutcomesTest extends AnyFunSuite with Matchers:
+
+  // ── Checkmate ───────────────────────────────────────────────────
+
+  test("checkmate ends game with CheckmateEvent"):
+    val engine   = EngineTestHelpers.makeEngine()
+    val observer = new EngineTestHelpers.MockObserver()
+    engine.subscribe(observer)
+
+    engine.processUserInput("f2f3")
+    engine.processUserInput("e7e5")
+    engine.processUserInput("g2g4")
+    observer.clear()
+
+    engine.processUserInput("d8h4")
+
+    observer.hasEvent[CheckmateEvent] shouldBe true
+    engine.context.result shouldBe Some(GameResult.Win(Color.Black))
+
+  test("checkmate with white winner"):
+    val engine   = EngineTestHelpers.makeEngine()
+    val observer = new EngineTestHelpers.MockObserver()
+    engine.subscribe(observer)
+
+    engine.processUserInput("e2e4")
+    engine.processUserInput("e7e5")
+    engine.processUserInput("f1c4")
+    engine.processUserInput("b8c6")
+    engine.processUserInput("d1h5")
+    engine.processUserInput("g8f6")
+    observer.clear()
+
+    engine.processUserInput("h5f7")
+
+    val evt = observer.getEvent[CheckmateEvent]
+    evt.isDefined shouldBe true
+    evt.get.winner shouldBe Color.White
+    engine.context.result shouldBe Some(GameResult.Win(Color.White))
+
+  // ── Stalemate ───────────────────────────────────────────────────
+
+  test("stalemate ends game with DrawEvent(Stalemate)"):
+    val engine   = EngineTestHelpers.makeEngine()
+    val observer = new EngineTestHelpers.MockObserver()
+    engine.subscribe(observer)
+
+    val moves = List(
+      "e2e3",
+      "a7a5",
+      "d1h5",
+      "a8a6",
+      "h5a5",
+      "h7h5",
+      "h2h4",
+      "a6h6",
+      "a5c7",
+      "f7f6",
+      "c7d7",
+      "e8f7",
+      "d7b7",
+      "d8d3",
+      "b7b8",
+      "d3h7",
+      "b8c8",
+      "f7g6",
+    )
+    moves.foreach(engine.processUserInput)
+    observer.clear()
+
+    engine.processUserInput("c8e6")
+
+    val evt = observer.getEvent[DrawEvent]
+    evt.isDefined shouldBe true
+    evt.get.reason shouldBe DrawReason.Stalemate
+    engine.context.result shouldBe Some(GameResult.Draw(DrawReason.Stalemate))
+
+  test("stalemate board is not reset after draw"):
+    val engine   = EngineTestHelpers.makeEngine()
+    val observer = new EngineTestHelpers.MockObserver()
+    engine.subscribe(observer)
+
+    val moves = List(
+      "e2e3",
+      "a7a5",
+      "d1h5",
+      "a8a6",
+      "h5a5",
+      "h7h5",
+      "h2h4",
+      "a6h6",
+      "a5c7",
+      "f7f6",
+      "c7d7",
+      "e8f7",
+      "d7b7",
+      "d8d3",
+      "b7b8",
+      "d3h7",
+      "b8c8",
+      "f7g6",
+      "c8e6",
+    )
+
+    moves.foreach(engine.processUserInput)
+
+    observer.hasEvent[DrawEvent] shouldBe true
+    engine.turn shouldBe Color.Black
+
+  // ── Check detection ────────────────────────────────────────────
+
+  test("check detected after move puts king in check"):
+    val engine   = EngineTestHelpers.makeEngine()
+    val observer = new EngineTestHelpers.MockObserver()
+    engine.subscribe(observer)
+
+    engine.processUserInput("e2e4")
+    engine.processUserInput("e7e5")
+    engine.processUserInput("f1c4")
+    engine.processUserInput("g8f6")
+    observer.clear()
+
+    engine.processUserInput("c4f7")
+
+    observer.hasEvent[CheckDetectedEvent] shouldBe true
+
+  test("check by knight"):
+    val engine   = EngineTestHelpers.makeEngine()
+    val observer = new EngineTestHelpers.MockObserver()
+    engine.subscribe(observer)
+
+    // White has K+N+Q so the position is not insufficient material after Nd4f5
+    EngineTestHelpers.loadFen(engine, "8/4k3/8/8/3N4/8/8/3QK3 w - - 0 1")
+    observer.clear()
+
+    engine.processUserInput("d4f5")
+
+    observer.hasEvent[CheckDetectedEvent] shouldBe true
+
+  // ── Fifty-move rule ────────────────────────────────────────────
+
+  test("fifty-move rule triggers when half-move clock reaches 100"):
+    val engine   = EngineTestHelpers.makeEngine()
+    val observer = new EngineTestHelpers.MockObserver()
+    engine.subscribe(observer)
+
+    EngineTestHelpers.loadFen(engine, "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 99 1")
+    observer.clear()
+
+    engine.processUserInput("g1f3")
+
+    observer.hasEvent[FiftyMoveRuleAvailableEvent] shouldBe true
+
+  test("fifty-move rule clock resets on pawn move"):
+    val engine = EngineTestHelpers.makeEngine()
+
+    EngineTestHelpers.loadFen(engine, "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 50 1")
+    engine.processUserInput("a2a3")
+
+    // Clock should reset to 0 after pawn move
+    engine.context.halfMoveClock shouldBe 0
+
+  test("fifty-move rule clock resets on capture"):
+    val engine = EngineTestHelpers.makeEngine()
+
+    // FEN: white pawn on e5, black pawn on d6, clock at 50
+    EngineTestHelpers.loadFen(engine, "4k3/8/3p4/4P3/8/8/8/4K3 w - - 50 1")
+    engine.processUserInput("e5d6")
+
+    // Clock should reset to 0 after capture
+    engine.context.halfMoveClock shouldBe 0
+
+  // ── Draw claim ────────────────────────────────────────────────
+
+  test("draw can be claimed when fifty-move rule is available"):
+    val engine   = EngineTestHelpers.makeEngine()
+    val observer = new EngineTestHelpers.MockObserver()
+    engine.subscribe(observer)
+
+    EngineTestHelpers.loadFen(engine, "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 100 1")
+    observer.clear()
+
+    engine.processUserInput("draw")
+
+    val evt = observer.getEvent[DrawEvent]
+    evt.isDefined shouldBe true
+    evt.get.reason shouldBe DrawReason.FiftyMoveRule
+    engine.context.result shouldBe Some(GameResult.Draw(DrawReason.FiftyMoveRule))
+
+  test("draw cannot be claimed when not available"):
+    val engine   = EngineTestHelpers.makeEngine()
+    val observer = new EngineTestHelpers.MockObserver()
+    engine.subscribe(observer)
+
+    engine.processUserInput("draw")
+
+    observer.hasEvent[InvalidMoveEvent] shouldBe true
+
+  // ── Insufficient material ──────────────────────────────────────────
+
+  test("insufficient material fires DrawEvent(InsufficientMaterial) after capture"):
+    val engine   = EngineTestHelpers.makeEngine()
+    val observer = new EngineTestHelpers.MockObserver()
+    engine.subscribe(observer)
+
+    // White Bishop d4 captures Black Rook g7, leaving K+B vs K (insufficient material).
+    // Black king on g8 can still move (f7/h7 not controlled), so it is not stalemate.
+    EngineTestHelpers.loadFen(engine, "6k1/6r1/8/8/3B4/8/8/K7 w - - 0 1")
+    observer.clear()
+
+    engine.processUserInput("d4g7")
+
+    val evt = observer.getEvent[DrawEvent]
+    evt.isDefined shouldBe true
+    evt.get.reason shouldBe DrawReason.InsufficientMaterial
+    engine.context.result shouldBe Some(GameResult.Draw(DrawReason.InsufficientMaterial))
+
+  // ── Threefold Repetition ──────────────────────────────────────────
+
+  test("draw command rejected when neither 50-move rule nor threefold repetition available"):
+    val engine   = EngineTestHelpers.makeEngine()
+    val observer = new EngineTestHelpers.MockObserver()
+    engine.subscribe(observer)
+
+    engine.processUserInput("e2e4")
+    observer.clear()
+
+    engine.processUserInput("draw")
+
+    observer.hasEvent[InvalidMoveEvent] shouldBe true
+
+  test("threefold repetition fires ThreefoldRepetitionAvailableEvent after 8-move shuffle"):
+    val engine   = EngineTestHelpers.makeEngine()
+    val observer = new EngineTestHelpers.MockObserver()
+    engine.subscribe(observer)
+
+    // Both knights shuffle home: initial position occurs 3 times on move 8 (Ng8)
+    engine.processUserInput("g1f3")
+    engine.processUserInput("g8f6")
+    engine.processUserInput("f3g1")
+    engine.processUserInput("f6g8")
+    engine.processUserInput("g1f3")
+    engine.processUserInput("g8f6")
+    engine.processUserInput("f3g1")
+    observer.clear()
+
+    engine.processUserInput("f6g8")  // 3rd occurrence of initial position
+
+    observer.hasEvent[ThreefoldRepetitionAvailableEvent] shouldBe true
+    engine.context.result shouldBe None  // claimable, not automatic
+
+  test("draw claim via threefold repetition ends game with DrawEvent"):
+    val engine   = EngineTestHelpers.makeEngine()
+    val observer = new EngineTestHelpers.MockObserver()
+    engine.subscribe(observer)
+
+    engine.processUserInput("g1f3")
+    engine.processUserInput("g8f6")
+    engine.processUserInput("f3g1")
+    engine.processUserInput("f6g8")
+    engine.processUserInput("g1f3")
+    engine.processUserInput("g8f6")
+    engine.processUserInput("f3g1")
+    engine.processUserInput("f6g8")  // threefold now available
+
+    observer.clear()
+    engine.processUserInput("draw")
+
+    val evt = observer.getEvent[DrawEvent]
+    evt.isDefined shouldBe true
+    evt.get.reason shouldBe DrawReason.ThreefoldRepetition
+    engine.context.result shouldBe Some(GameResult.Draw(DrawReason.ThreefoldRepetition))
+
+  test("loadPosition with non-empty moves preserves context as-is"):
+    val engine   = EngineTestHelpers.makeEngine()
+    val observer = new EngineTestHelpers.MockObserver()
+    engine.subscribe(observer)
+
+    // Build a context that already has a move in its history
+    val move = de.nowchess.api.move.Move(
+      de.nowchess.api.board.Square(de.nowchess.api.board.File.E, de.nowchess.api.board.Rank.R2),
+      de.nowchess.api.board.Square(de.nowchess.api.board.File.E, de.nowchess.api.board.Rank.R4),
+    )
+    val ctxWithMove = de.nowchess.api.game.GameContext.initial.withMove(move)
+
+    engine.loadPosition(ctxWithMove)
+
+    observer.hasEvent[BoardResetEvent] shouldBe true

modules/core/src/test/scala/de/nowchess/chess/engine/GameEnginePromotionTest.scala

@@ -1,10 +1,12 @@
 package de.nowchess.chess.engine
 
 import de.nowchess.api.board.{Board, Color, File, Piece, PieceType, Rank, Square}
-import de.nowchess.api.move.PromotionPiece
-import de.nowchess.chess.logic.GameHistory
-import de.nowchess.chess.notation.FenParser
+import de.nowchess.api.game.GameContext
+import de.nowchess.api.move.{Move, MoveType, PromotionPiece}
+import de.nowchess.io.fen.FenParser
 import de.nowchess.chess.observer.*
+import de.nowchess.rules.RuleSet
+import de.nowchess.rules.sets.DefaultRules
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
 
@@ -17,56 +19,59 @@ class GameEnginePromotionTest extends AnyFunSuite with Matchers:
     engine.subscribe(new Observer { def onGameEvent(e: GameEvent): Unit = events += e })
     events
 
+  private def engineWith(board: Board, turn: Color = Color.White): GameEngine =
+    new GameEngine(initialContext = GameContext.initial.withBoard(board).withTurn(turn))
+
   test("processUserInput fires PromotionRequiredEvent when pawn reaches back rank") {
     val promotionBoard = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val engine = new GameEngine(initialBoard = promotionBoard)
-    val events = captureEvents(engine)
+    val engine         = engineWith(promotionBoard)
+    val events         = captureEvents(engine)
 
     engine.processUserInput("e7e8")
 
-    events.exists(_.isInstanceOf[PromotionRequiredEvent]) should be (true)
-    events.collect { case e: PromotionRequiredEvent => e }.head.from should be (sq(File.E, Rank.R7))
+    events.exists { case _: PromotionRequiredEvent => true; case _ => false } should be(true)
+    events.collect { case e: PromotionRequiredEvent => e }.head.from should be(sq(File.E, Rank.R7))
   }
 
   test("isPendingPromotion is true after PromotionRequired input") {
     val promotionBoard = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val engine = new GameEngine(initialBoard = promotionBoard)
+    val engine         = engineWith(promotionBoard)
     captureEvents(engine)
 
     engine.processUserInput("e7e8")
 
-    engine.isPendingPromotion should be (true)
+    engine.isPendingPromotion should be(true)
   }
 
   test("isPendingPromotion is false before any promotion input") {
     val engine = new GameEngine()
-    engine.isPendingPromotion should be (false)
+    engine.isPendingPromotion should be(false)
   }
 
   test("completePromotion fires MoveExecutedEvent with promoted piece") {
     val promotionBoard = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val engine = new GameEngine(initialBoard = promotionBoard)
-    val events = captureEvents(engine)
+    val engine         = engineWith(promotionBoard)
+    val events         = captureEvents(engine)
 
     engine.processUserInput("e7e8")
     engine.completePromotion(PromotionPiece.Queen)
 
-    engine.isPendingPromotion should be (false)
-    engine.board.pieceAt(sq(File.E, Rank.R8)) should be (Some(Piece(Color.White, PieceType.Queen)))
-    engine.board.pieceAt(sq(File.E, Rank.R7)) should be (None)
-    engine.history.moves.head.promotionPiece should be (Some(PromotionPiece.Queen))
-    events.exists(_.isInstanceOf[MoveExecutedEvent]) should be (true)
+    engine.isPendingPromotion should be(false)
+    engine.board.pieceAt(sq(File.E, Rank.R8)) should be(Some(Piece(Color.White, PieceType.Queen)))
+    engine.board.pieceAt(sq(File.E, Rank.R7)) should be(None)
+    engine.context.moves.last.moveType shouldBe MoveType.Promotion(PromotionPiece.Queen)
+    events.exists { case _: MoveExecutedEvent => true; case _ => false } should be(true)
   }
 
   test("completePromotion with rook underpromotion") {
     val promotionBoard = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val engine = new GameEngine(initialBoard = promotionBoard)
+    val engine         = engineWith(promotionBoard)
     captureEvents(engine)
 
     engine.processUserInput("e7e8")
     engine.completePromotion(PromotionPiece.Rook)
 
-    engine.board.pieceAt(sq(File.E, Rank.R8)) should be (Some(Piece(Color.White, PieceType.Rook)))
+    engine.board.pieceAt(sq(File.E, Rank.R8)) should be(Some(Piece(Color.White, PieceType.Rook)))
   }
 
   test("completePromotion with no pending promotion fires InvalidMoveEvent") {
@@ -75,93 +80,120 @@ class GameEnginePromotionTest extends AnyFunSuite with Matchers:
 
     engine.completePromotion(PromotionPiece.Queen)
 
-    events.exists(_.isInstanceOf[InvalidMoveEvent]) should be (true)
-    engine.isPendingPromotion should be (false)
+    events.exists { case _: InvalidMoveEvent => true; case _ => false } should be(true)
+    engine.isPendingPromotion should be(false)
   }
 
   test("completePromotion fires CheckDetectedEvent when promotion gives check") {
     val promotionBoard = FenParser.parseBoard("3k4/4P3/8/8/8/8/8/8").get
-    val engine = new GameEngine(initialBoard = promotionBoard)
-    val events = captureEvents(engine)
+    val engine         = engineWith(promotionBoard)
+    val events         = captureEvents(engine)
 
     engine.processUserInput("e7e8")
     engine.completePromotion(PromotionPiece.Queen)
 
-    events.exists(_.isInstanceOf[CheckDetectedEvent]) should be (true)
+    events.exists { case _: CheckDetectedEvent => true; case _ => false } should be(true)
   }
 
   test("completePromotion results in Moved when promotion doesn't give check") {
-    // White pawn on e7, black king on a2 (far away, not in check after promotion)
-    val board = FenParser.parseBoard("8/4P3/8/8/8/8/k7/8").get
-    val engine = new GameEngine(initialBoard = board)
+    val board  = FenParser.parseBoard("8/4P3/8/8/8/8/k7/8").get
+    val engine = engineWith(board)
     val events = captureEvents(engine)
 
     engine.processUserInput("e7e8")
     engine.completePromotion(PromotionPiece.Queen)
 
-    engine.isPendingPromotion should be (false)
-    engine.board.pieceAt(sq(File.E, Rank.R8)) should be (Some(Piece(Color.White, PieceType.Queen)))
-    events.filter(_.isInstanceOf[MoveExecutedEvent]) should not be empty
-    events.exists(_.isInstanceOf[CheckDetectedEvent]) should be (false)
+    engine.isPendingPromotion should be(false)
+    engine.board.pieceAt(sq(File.E, Rank.R8)) should be(Some(Piece(Color.White, PieceType.Queen)))
+    events.collect { case e: MoveExecutedEvent => e } should not be empty
+    events.exists { case _: CheckDetectedEvent => true; case _ => false } should be(false)
   }
 
   test("completePromotion results in Checkmate when promotion delivers checkmate") {
-    // Black king on a8, white king on b6, white pawn on h7
-    // h7->h8=Q delivers checkmate
-    val board = FenParser.parseBoard("k7/7P/1K6/8/8/8/8/8").get
-    val engine = new GameEngine(initialBoard = board)
+    val board  = FenParser.parseBoard("k7/7P/1K6/8/8/8/8/8").get
+    val engine = engineWith(board)
     val events = captureEvents(engine)
 
     engine.processUserInput("h7h8")
     engine.completePromotion(PromotionPiece.Queen)
 
-    engine.isPendingPromotion should be (false)
-    events.exists(_.isInstanceOf[CheckmateEvent]) should be (true)
+    engine.isPendingPromotion should be(false)
+    events.exists { case _: CheckmateEvent => true; case _ => false } should be(true)
   }
 
   test("completePromotion results in Stalemate when promotion creates stalemate") {
-    // Black king on a8, white pawn on b7, white bishop on c7, white king on b6
-    // b7->b8=N: no check; Ka8 has no legal moves -> stalemate
-    val board = FenParser.parseBoard("k7/1PB5/1K6/8/8/8/8/8").get
-    val engine = new GameEngine(initialBoard = board)
+    val board  = FenParser.parseBoard("k7/1PB5/1K6/8/8/8/8/8").get
+    val engine = engineWith(board)
     val events = captureEvents(engine)
 
     engine.processUserInput("b7b8")
     engine.completePromotion(PromotionPiece.Knight)
 
-    engine.isPendingPromotion should be (false)
-    events.exists(_.isInstanceOf[StalemateEvent]) should be (true)
+    engine.isPendingPromotion should be(false)
+    events.exists { case _: DrawEvent => true; case _ => false } should be(true)
   }
 
   test("completePromotion with black pawn promotion results in Moved") {
-    // Black pawn e2, white king h3 (not on rank 1 or file e), black king a8
-    // e2->e1=Q: queen on e1 does not attack h3 -> normal Moved
-    val board = FenParser.parseBoard("k7/8/8/8/8/7K/4p3/8").get
-    val engine = new GameEngine(initialBoard = board, initialTurn = Color.Black)
+    val board  = FenParser.parseBoard("k7/8/8/8/8/7K/4p3/8").get
+    val engine = engineWith(board, Color.Black)
     val events = captureEvents(engine)
 
     engine.processUserInput("e2e1")
     engine.completePromotion(PromotionPiece.Queen)
 
-    engine.isPendingPromotion should be (false)
-    engine.board.pieceAt(sq(File.E, Rank.R1)) should be (Some(Piece(Color.Black, PieceType.Queen)))
-    events.filter(_.isInstanceOf[MoveExecutedEvent]) should not be empty
-    events.exists(_.isInstanceOf[CheckDetectedEvent]) should be (false)
+    engine.isPendingPromotion should be(false)
+    engine.board.pieceAt(sq(File.E, Rank.R1)) should be(Some(Piece(Color.Black, PieceType.Queen)))
+    events.collect { case e: MoveExecutedEvent => e } should not be empty
+    events.exists { case _: CheckDetectedEvent => true; case _ => false } should be(false)
   }
 
-  test("completePromotion catch-all fires InvalidMoveEvent for unexpected MoveResult") {
-    // Inject a function that returns an unexpected MoveResult to hit the catch-all case
+  test("completePromotion fires InvalidMoveEvent when legalMoves returns only Normal moves to back rank") {
+    // Custom RuleSet: delegates all methods to StandardRules except legalMoves,
+    // which strips Promotion move types and returns Normal moves instead.
+    // This makes completePromotion unable to find Move(from, to, Promotion(Queen)),
+    // triggering the "Error completing promotion." branch.
+    val delegatingRuleSet: RuleSet = new RuleSet:
+      def candidateMoves(context: GameContext)(square: Square): List[Move] =
+        DefaultRules.candidateMoves(context)(square)
+      def legalMoves(context: GameContext)(square: Square): List[Move] =
+        DefaultRules.legalMoves(context)(square).map { m =>
+          m.moveType match
+            case MoveType.Promotion(_) => Move(m.from, m.to, MoveType.Normal())
+            case _                     => m
+        }
+      def allLegalMoves(context: GameContext): List[Move] =
+        DefaultRules.allLegalMoves(context)
+      def isCheck(context: GameContext): Boolean =
+        DefaultRules.isCheck(context)
+      def isCheckmate(context: GameContext): Boolean =
+        DefaultRules.isCheckmate(context)
+      def isStalemate(context: GameContext): Boolean =
+        DefaultRules.isStalemate(context)
+      def isInsufficientMaterial(context: GameContext): Boolean =
+        DefaultRules.isInsufficientMaterial(context)
+      def isFiftyMoveRule(context: GameContext): Boolean =
+        DefaultRules.isFiftyMoveRule(context)
+      def isThreefoldRepetition(context: GameContext): Boolean =
+        DefaultRules.isThreefoldRepetition(context)
+      def applyMove(context: GameContext)(move: Move): GameContext =
+        DefaultRules.applyMove(context)(move)
+
     val promotionBoard = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val stubFn: (de.nowchess.api.board.Board, de.nowchess.chess.logic.GameHistory, Square, Square, PromotionPiece, Color) => de.nowchess.chess.controller.MoveResult =
-      (_, _, _, _, _, _) => de.nowchess.chess.controller.MoveResult.NoPiece
-    val engine = new GameEngine(initialBoard = promotionBoard, completePromotionFn = stubFn)
-    val events = captureEvents(engine)
+    val initialCtx     = GameContext.initial.withBoard(promotionBoard).withTurn(Color.White)
+    val engine         = new GameEngine(initialCtx, delegatingRuleSet)
+    val events         = captureEvents(engine)
 
+    // isPromotionMove will fire because pawn is on rank 7 heading to rank 8,
+    // and legalMoves returns Normal candidates (still non-empty) — sets pendingPromotion
     engine.processUserInput("e7e8")
-    engine.isPendingPromotion should be (true)
+    engine.isPendingPromotion should be(true)
 
+    // completePromotion looks for Move(e7, e8, Promotion(Queen)) in legalMoves,
+    // but only Normal moves exist → fires InvalidMoveEvent
     engine.completePromotion(PromotionPiece.Queen)
 
-    engine.isPendingPromotion should be (false)
-    events.exists(_.isInstanceOf[InvalidMoveEvent]) should be (true)
+    engine.isPendingPromotion should be(false)
+    events.exists { case _: InvalidMoveEvent => true; case _ => false } should be(true)
+    val invalidEvt = events.collect { case e: InvalidMoveEvent => e }.last
+    invalidEvt.reason should include("Error completing promotion")
   }

modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineScenarioTest.scala

@@ -0,0 +1,132 @@
+package de.nowchess.chess.engine
+
+import de.nowchess.api.board.{Color, File, Piece, Rank, Square}
+import de.nowchess.api.game.GameContext
+import de.nowchess.chess.observer.*
+import de.nowchess.io.fen.FenParser
+import org.scalatest.funsuite.AnyFunSuite
+import org.scalatest.matchers.should.Matchers
+import scala.collection.mutable
+
+class GameEngineScenarioTest extends AnyFunSuite with Matchers:
+
+  // ── Observer wiring ────────────────────────────────────────────
+
+  test("observer subscribe and unsubscribe behavior"):
+    val engine   = EngineTestHelpers.makeEngine()
+    val observer = new EngineTestHelpers.MockObserver()
+    engine.subscribe(observer)
+    engine.processUserInput("e2e4")
+    observer.hasEvent[MoveExecutedEvent] shouldBe true
+    val countBeforeUnsubscribe = observer.eventCount
+    engine.subscribe(observer)
+    engine.unsubscribe(observer)
+    engine.processUserInput("e2e4")
+    observer.eventCount shouldBe countBeforeUnsubscribe
+
+  // ── Initial state ──────────────────────────────────────────────
+
+  test("initial engine state is standard"):
+    val engine = EngineTestHelpers.makeEngine()
+    engine.board.pieceAt(Square(File.E, Rank.R1)) shouldBe Some(Piece.WhiteKing)
+    engine.turn shouldBe Color.White
+
+  // ── Quit command ──────────────────────────────────────────────
+
+  test("quit aliases and reset keep engine responsive"):
+    val engine = EngineTestHelpers.makeEngine()
+    engine.processUserInput("quit")
+    engine.processUserInput("q")
+    engine.processUserInput("e2e4")
+
+    engine.reset()
+
+    engine.board.pieceAt(Square(File.E, Rank.R2)) shouldBe Some(Piece.WhitePawn)
+    engine.turn shouldBe Color.White
+
+  // ── Turn toggling ──────────────────────────────────────────────
+
+  test("turn toggles across valid move sequence"):
+    val engine = EngineTestHelpers.makeEngine()
+    engine.processUserInput("e2e4")
+    engine.turn shouldBe Color.Black
+    engine.processUserInput("e7e5")
+    engine.turn shouldBe Color.White
+
+  // ── Invalid moves (minimal) ────────────────────────────────────
+
+  test("invalid move forms trigger InvalidMoveEvent and keep turn where relevant"):
+    val engine   = EngineTestHelpers.makeEngine()
+    val observer = new EngineTestHelpers.MockObserver()
+    engine.subscribe(observer)
+
+    engine.processUserInput("h3h4")
+
+    observer.hasEvent[InvalidMoveEvent] shouldBe true
+    engine.turn shouldBe Color.White // turn unchanged
+
+    engine.processUserInput("e7e5") // try to move black pawn on white's turn
+
+    observer.hasEvent[InvalidMoveEvent] shouldBe true
+
+    engine.processUserInput("e2e4")
+    engine.processUserInput("e5e4") // pawn backward
+
+    observer.hasEvent[InvalidMoveEvent] shouldBe true
+
+  // ── Undo/Redo ────────────────────────────────────────────────
+
+  test("undo redo success and empty-history failures"):
+    val engine   = EngineTestHelpers.makeEngine()
+    val observer = new EngineTestHelpers.MockObserver()
+    engine.subscribe(observer)
+
+    engine.undo()
+    observer.hasEvent[InvalidMoveEvent] shouldBe true
+    observer.clear()
+
+    engine.processUserInput("e2e4")
+
+    engine.undo()
+
+    engine.board.pieceAt(Square(File.E, Rank.R2)) shouldBe Some(Piece.WhitePawn)
+    engine.turn shouldBe Color.White
+
+    engine.redo()
+
+    engine.board.pieceAt(Square(File.E, Rank.R4)) shouldBe Some(Piece.WhitePawn)
+    engine.turn shouldBe Color.Black
+    observer.clear()
+    engine.redo()
+    observer.hasEvent[InvalidMoveEvent] shouldBe true
+
+  // ── Fifty-move rule ────────────────────────────────────────────
+
+  test("fifty-move event and draw claim success/failure"):
+    val engine   = EngineTestHelpers.makeEngine()
+    val observer = new EngineTestHelpers.MockObserver()
+    engine.subscribe(observer)
+
+    // Load FEN with half-move clock at 99
+    EngineTestHelpers.loadFen(engine, "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 99 1")
+    observer.clear()
+
+    // Use a legal non-pawn non-capture move so the clock increments to 100.
+    engine.processUserInput("g1f3")
+
+    observer.hasEvent[FiftyMoveRuleAvailableEvent] shouldBe true
+
+    // Load position with sufficient move history for draw claim
+    EngineTestHelpers.loadFen(engine, "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 100 1")
+    observer.clear()
+
+    engine.processUserInput("draw")
+
+    observer.hasEvent[DrawEvent] shouldBe true
+
+    // Initial position has no draw available
+    observer.clear()
+    engine.reset()
+    engine.processUserInput("draw")
+
+    observer.hasEvent[InvalidMoveEvent] shouldBe true

modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineSpecialMovesTest.scala

@@ -0,0 +1,210 @@
+package de.nowchess.chess.engine
+
+import de.nowchess.api.board.Color
+import de.nowchess.api.move.PromotionPiece
+import de.nowchess.chess.observer.*
+import org.scalatest.funsuite.AnyFunSuite
+import org.scalatest.matchers.should.Matchers
+
+class GameEngineSpecialMovesTest extends AnyFunSuite with Matchers:
+
+  // ── Castling ────────────────────────────────────────────────────
+
+  test("kingside castling executes successfully"):
+    val engine   = EngineTestHelpers.makeEngine()
+    val observer = new EngineTestHelpers.MockObserver()
+    engine.subscribe(observer)
+
+    // FEN: white king on e1, rook on h1, f1/g1 clear
+    EngineTestHelpers.loadFen(engine, "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQK2R w KQkq - 0 1")
+    observer.clear()
+
+    engine.processUserInput("e1g1")
+
+    observer.hasEvent[MoveExecutedEvent] shouldBe true
+    engine.turn shouldBe Color.Black
+
+  test("queenside castling executes successfully"):
+    val engine   = EngineTestHelpers.makeEngine()
+    val observer = new EngineTestHelpers.MockObserver()
+    engine.subscribe(observer)
+
+    // FEN: white king on e1, rook on a1, b1/c1/d1 clear
+    EngineTestHelpers.loadFen(engine, "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/R3K2R w KQkq - 0 1")
+    observer.clear()
+
+    engine.processUserInput("e1c1")
+
+    observer.hasEvent[MoveExecutedEvent] shouldBe true
+    engine.turn shouldBe Color.Black
+
+  test("undo castling emits PGN notation"):
+    val engine   = EngineTestHelpers.makeEngine()
+    val observer = new EngineTestHelpers.MockObserver()
+    engine.subscribe(observer)
+
+    EngineTestHelpers.loadFen(engine, "k7/8/8/8/8/8/8/R3K3 w Q - 0 1")
+    observer.clear()
+
+    engine.processUserInput("e1c1")
+    observer.clear()
+    engine.undo()
+
+    val evt = observer.getEvent[MoveUndoneEvent]
+    evt.isDefined shouldBe true
+    evt.get.pgnNotation shouldBe "O-O-O"
+
+  // ── En passant ──────────────────────────────────────────────────
+
+  test("en passant capture executes successfully"):
+    val engine   = EngineTestHelpers.makeEngine()
+    val observer = new EngineTestHelpers.MockObserver()
+    engine.subscribe(observer)
+
+    // FEN: white pawn e5, black pawn d5 (just pushed), en passant square d6
+    EngineTestHelpers.loadFen(engine, "k7/8/8/3pP3/8/8/8/7K w - d6 0 1")
+    observer.clear()
+
+    engine.processUserInput("e5d6")
+
+    observer.hasEvent[MoveExecutedEvent] shouldBe true
+    val moveEvt = observer.getEvent[MoveExecutedEvent]
+    moveEvt.get.capturedPiece shouldBe defined // pawn was captured
+
+  test("undo en passant emits file-x-destination notation"):
+    val engine   = EngineTestHelpers.makeEngine()
+    val observer = new EngineTestHelpers.MockObserver()
+    engine.subscribe(observer)
+
+    EngineTestHelpers.loadFen(engine, "k7/8/8/3pP3/8/8/8/7K w - d6 0 1")
+    observer.clear()
+
+    engine.processUserInput("e5d6")
+    observer.clear()
+    engine.undo()
+
+    val evt = observer.getEvent[MoveUndoneEvent]
+    evt.isDefined shouldBe true
+    evt.get.pgnNotation shouldBe "exd6"
+
+  // ── Pawn promotion ─────────────────────────────────────────────
+
+  test("pawn reaching back rank requires promotion"):
+    val engine   = EngineTestHelpers.makeEngine()
+    val observer = new EngineTestHelpers.MockObserver()
+    engine.subscribe(observer)
+
+    EngineTestHelpers.loadFen(engine, "8/4P3/4k3/8/8/8/8/8 w - - 0 1")
+    observer.clear()
+
+    engine.processUserInput("e7e8")
+
+    observer.hasEvent[PromotionRequiredEvent] shouldBe true
+    engine.isPendingPromotion shouldBe true
+
+  test("completePromotion to Queen executes move"):
+    val engine = EngineTestHelpers.makeEngine()
+
+    EngineTestHelpers.loadFen(engine, "8/4P3/8/8/8/8/k7/8 w - - 0 1")
+    engine.processUserInput("e7e8")
+    engine.completePromotion(PromotionPiece.Queen)
+
+    engine.isPendingPromotion shouldBe false
+    engine.turn shouldBe Color.Black
+
+  test("completePromotion to Rook executes move"):
+    val engine = EngineTestHelpers.makeEngine()
+
+    EngineTestHelpers.loadFen(engine, "8/4P3/8/8/8/8/k7/8 w - - 0 1")
+    engine.processUserInput("e7e8")
+    engine.completePromotion(PromotionPiece.Rook)
+
+    engine.isPendingPromotion shouldBe false
+    engine.turn shouldBe Color.Black
+
+  test("completePromotion to Bishop executes move"):
+    val engine = EngineTestHelpers.makeEngine()
+
+    EngineTestHelpers.loadFen(engine, "8/4P3/8/8/8/8/k7/8 w - - 0 1")
+    engine.processUserInput("e7e8")
+    engine.completePromotion(PromotionPiece.Bishop)
+
+    engine.isPendingPromotion shouldBe false
+    engine.turn shouldBe Color.Black
+
+  test("completePromotion to Knight executes move"):
+    val engine = EngineTestHelpers.makeEngine()
+
+    EngineTestHelpers.loadFen(engine, "8/4P3/8/8/8/8/k7/8 w - - 0 1")
+    engine.processUserInput("e7e8")
+    engine.completePromotion(PromotionPiece.Knight)
+
+    engine.isPendingPromotion shouldBe false
+    engine.turn shouldBe Color.Black
+
+  test("promotion to Queen with discovered check emits CheckDetectedEvent"):
+    val engine   = EngineTestHelpers.makeEngine()
+    val observer = new EngineTestHelpers.MockObserver()
+    engine.subscribe(observer)
+
+    // FEN: white pawn e7, black king e6, white king e1
+    EngineTestHelpers.loadFen(engine, "8/4P3/4k3/8/8/8/8/4K3 w - - 0 1")
+    observer.clear()
+
+    engine.processUserInput("e7e8")
+    engine.completePromotion(PromotionPiece.Queen)
+
+    observer.hasEvent[CheckDetectedEvent] shouldBe true
+
+  test("promotion to Queen with checkmate emits CheckmateEvent"):
+    val engine   = EngineTestHelpers.makeEngine()
+    val observer = new EngineTestHelpers.MockObserver()
+    engine.subscribe(observer)
+
+    // FEN: known promotion-mate pattern
+    EngineTestHelpers.loadFen(engine, "k7/7P/1K6/8/8/8/8/8 w - - 0 1")
+    observer.clear()
+
+    engine.processUserInput("h7h8")
+    engine.completePromotion(PromotionPiece.Queen)
+
+    observer.hasEvent[CheckmateEvent] shouldBe true
+
+  test("undo promotion emits notation with piece suffix"):
+    val engine   = EngineTestHelpers.makeEngine()
+    val observer = new EngineTestHelpers.MockObserver()
+    engine.subscribe(observer)
+
+    // White rook on h2 keeps material sufficient (K+B+R vs K) after bishop promotion
+    EngineTestHelpers.loadFen(engine, "8/4P3/4k3/8/8/8/7R/7K w - - 0 1")
+    engine.processUserInput("e7e8")
+    engine.completePromotion(PromotionPiece.Bishop)
+    observer.clear()
+
+    engine.undo()
+
+    val evt = observer.getEvent[MoveUndoneEvent]
+    evt.isDefined shouldBe true
+    evt.get.pgnNotation shouldBe "e8=B"
+
+  test("black pawn promotion executes"):
+    val engine = EngineTestHelpers.makeEngine()
+
+    EngineTestHelpers.loadFen(engine, "8/8/8/8/8/4k3/4p3/8 b - - 0 1")
+    engine.processUserInput("e2e1")
+
+    engine.isPendingPromotion shouldBe true
+    engine.completePromotion(PromotionPiece.Queen)
+
+    engine.isPendingPromotion shouldBe false
+    engine.turn shouldBe Color.White
+
+  // ── Promotion capturing ────────────────────────────────────────
+
+  test("pawn promotion with capture executes"):
+    val engine = EngineTestHelpers.makeEngine()
+
+    EngineTestHelpers.loadFen(engine, "3n4/4P3/4k3/8/8/8/8/4K3 w - - 0 1")
+    engine.processUserInput("e7d8")
+
+    engine.isPendingPromotion shouldBe true

modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineTest.scala

@@ -1,351 +0,0 @@
-package de.nowchess.chess.engine
-
-import scala.collection.mutable
-import de.nowchess.api.board.{Board, Color}
-import de.nowchess.chess.logic.GameHistory
-import de.nowchess.chess.observer.{Observer, GameEvent, MoveExecutedEvent, CheckDetectedEvent, BoardResetEvent, InvalidMoveEvent, FiftyMoveRuleAvailableEvent, DrawClaimedEvent, MoveUndoneEvent, MoveRedoneEvent}
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class GameEngineTest extends AnyFunSuite with Matchers:
-
-  test("GameEngine starts with initial board state"):
-    val engine = new GameEngine()
-    engine.board shouldBe Board.initial
-    engine.history shouldBe GameHistory.empty
-    engine.turn shouldBe Color.White
-
-  test("GameEngine accepts Observer subscription"):
-    val engine = new GameEngine()
-    val mockObserver = new MockObserver()
-    engine.subscribe(mockObserver)
-    engine.observerCount shouldBe 1
-
-  test("GameEngine notifies observers on valid move"):
-    val engine = new GameEngine()
-    val mockObserver = new MockObserver()
-    engine.subscribe(mockObserver)
-    engine.processUserInput("e2e4")
-    mockObserver.events.size shouldBe 1
-    mockObserver.events.head shouldBe a[MoveExecutedEvent]
-
-  test("GameEngine updates state after valid move"):
-    val engine = new GameEngine()
-    val initialTurn = engine.turn
-    engine.processUserInput("e2e4")
-    engine.turn shouldNot be(initialTurn)
-    engine.turn shouldBe Color.Black
-
-  test("GameEngine notifies observers on invalid move"):
-    val engine = new GameEngine()
-    val mockObserver = new MockObserver()
-    engine.subscribe(mockObserver)
-    engine.processUserInput("invalid_move")
-    mockObserver.events.size shouldBe 1
-
-  test("GameEngine notifies multiple observers"):
-    val engine = new GameEngine()
-    val observer1 = new MockObserver()
-    val observer2 = new MockObserver()
-    engine.subscribe(observer1)
-    engine.subscribe(observer2)
-    engine.processUserInput("e2e4")
-    observer1.events.size shouldBe 1
-    observer2.events.size shouldBe 1
-
-  test("GameEngine allows observer unsubscription"):
-    val engine = new GameEngine()
-    val mockObserver = new MockObserver()
-    engine.subscribe(mockObserver)
-    engine.unsubscribe(mockObserver)
-    engine.observerCount shouldBe 0
-
-  test("GameEngine unsubscribed observer receives no events"):
-    val engine = new GameEngine()
-    val mockObserver = new MockObserver()
-    engine.subscribe(mockObserver)
-    engine.unsubscribe(mockObserver)
-    engine.processUserInput("e2e4")
-    mockObserver.events.size shouldBe 0
-
-  test("GameEngine reset notifies observers and resets state"):
-    val engine = new GameEngine()
-    engine.processUserInput("e2e4")
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    engine.reset()
-    engine.board shouldBe Board.initial
-    engine.turn shouldBe Color.White
-    observer.events.size shouldBe 1
-
-  test("GameEngine processes sequence of moves"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    engine.processUserInput("e2e4")
-    engine.processUserInput("e7e5")
-    observer.events.size shouldBe 2
-    engine.turn shouldBe Color.White
-
-  test("GameEngine is thread-safe for synchronized operations"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    val t = new Thread(() => engine.processUserInput("e2e4"))
-    t.start()
-    t.join()
-    observer.events.size shouldBe 1
-
-  test("GameEngine canUndo returns false initially"):
-    val engine = new GameEngine()
-    engine.canUndo shouldBe false
-
-  test("GameEngine canUndo returns true after move"):
-    val engine = new GameEngine()
-    engine.processUserInput("e2e4")
-    engine.canUndo shouldBe true
-
-  test("GameEngine canRedo returns false initially"):
-    val engine = new GameEngine()
-    engine.canRedo shouldBe false
-
-  test("GameEngine undo restores previous state"):
-    val engine = new GameEngine()
-    engine.processUserInput("e2e4")
-    val boardAfterMove = engine.board
-    engine.undo()
-    engine.board shouldBe Board.initial
-    engine.turn shouldBe Color.White
-
-  test("GameEngine undo notifies observers"):
-    val engine = new GameEngine()
-    engine.processUserInput("e2e4")
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    observer.events.clear()
-    engine.undo()
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe a[MoveUndoneEvent]
-
-  test("GameEngine redo replays undone move"):
-    val engine = new GameEngine()
-    engine.processUserInput("e2e4")
-    val boardAfterMove = engine.board
-    engine.undo()
-    engine.redo()
-    engine.board shouldBe boardAfterMove
-    engine.turn shouldBe Color.Black
-
-  test("GameEngine canUndo false when nothing to undo"):
-    val engine = new GameEngine()
-    engine.canUndo shouldBe false
-    engine.processUserInput("e2e4")
-    engine.undo()
-    engine.canUndo shouldBe false
-
-  test("GameEngine canRedo true after undo"):
-    val engine = new GameEngine()
-    engine.processUserInput("e2e4")
-    engine.undo()
-    engine.canRedo shouldBe true
-
-  test("GameEngine canRedo false after redo"):
-    val engine = new GameEngine()
-    engine.processUserInput("e2e4")
-    engine.undo()
-    engine.redo()
-    engine.canRedo shouldBe false
-
-  test("GameEngine undo on empty history sends invalid event"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    engine.undo()
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe a[InvalidMoveEvent]
-
-  test("GameEngine redo on empty redo sends invalid event"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    engine.redo()
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe a[InvalidMoveEvent]
-
-  test("GameEngine undo via processUserInput"):
-    val engine = new GameEngine()
-    engine.processUserInput("e2e4")
-    val boardAfterMove = engine.board
-    engine.processUserInput("undo")
-    engine.board shouldBe Board.initial
-
-  test("GameEngine redo via processUserInput"):
-    val engine = new GameEngine()
-    engine.processUserInput("e2e4")
-    val boardAfterMove = engine.board
-    engine.processUserInput("undo")
-    engine.processUserInput("redo")
-    engine.board shouldBe boardAfterMove
-
-  test("GameEngine handles empty input"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    engine.processUserInput("")
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe a[InvalidMoveEvent]
-
-  test("GameEngine multiple undo/redo sequence"):
-    val engine = new GameEngine()
-    engine.processUserInput("e2e4")
-    engine.processUserInput("e7e5")
-    engine.processUserInput("g1f3")
-    
-    engine.turn shouldBe Color.Black
-    
-    engine.undo()
-    engine.turn shouldBe Color.White
-    
-    engine.undo()
-    engine.turn shouldBe Color.Black
-    
-    engine.undo()
-    engine.turn shouldBe Color.White
-    engine.board shouldBe Board.initial
-
-  test("GameEngine redo after multiple undos"):
-    val engine = new GameEngine()
-    engine.processUserInput("e2e4")
-    engine.processUserInput("e7e5")
-    engine.processUserInput("g1f3")
-    
-    engine.undo()
-    engine.undo()
-    engine.undo()
-    
-    engine.redo()
-    engine.turn shouldBe Color.Black
-    
-    engine.redo()
-    engine.turn shouldBe Color.White
-    
-    engine.redo()
-    engine.turn shouldBe Color.Black
-
-  test("GameEngine new move after undo clears redo history"):
-    val engine = new GameEngine()
-    engine.processUserInput("e2e4")
-    engine.processUserInput("e7e5")
-    engine.undo()
-    engine.canRedo shouldBe true
-    
-    engine.processUserInput("e7e6")  // Different move
-    engine.canRedo shouldBe false
-
-  test("GameEngine command history tracking"):
-    val engine = new GameEngine()
-    engine.commandHistory.size shouldBe 0
-    
-    engine.processUserInput("e2e4")
-    engine.commandHistory.size shouldBe 1
-    
-    engine.processUserInput("e7e5")
-    engine.commandHistory.size shouldBe 2
-
-  test("GameEngine quit input"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    val initialEvents = observer.events.size
-    engine.processUserInput("quit")
-    // quit should not produce an event
-    observer.events.size shouldBe initialEvents
-
-  test("GameEngine quit via q"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    val initialEvents = observer.events.size
-    engine.processUserInput("q")
-    observer.events.size shouldBe initialEvents
-  
-  test("GameEngine undo notifies with MoveUndoneEvent after successful undo"):
-    val engine = new GameEngine()
-    engine.processUserInput("e2e4")
-    engine.processUserInput("e7e5")
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    observer.events.clear()
-
-    engine.undo()
-
-    // Should have received a MoveUndoneEvent on undo
-    observer.events.size should be > 0
-    observer.events.exists(_.isInstanceOf[MoveUndoneEvent]) shouldBe true
-
-  test("GameEngine redo notifies with MoveRedoneEvent after successful redo"):
-    val engine = new GameEngine()
-    engine.processUserInput("e2e4")
-    engine.processUserInput("e7e5")
-    val boardAfterSecondMove = engine.board
-
-    engine.undo()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    observer.events.clear()
-
-    engine.redo()
-
-    // Should have received a MoveRedoneEvent for the redo
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe a[MoveRedoneEvent]
-    engine.board shouldBe boardAfterSecondMove
-    engine.turn shouldBe Color.White
-
-  // ──── 50-move rule ───────────────────────────────────────────────────
-
-  test("GameEngine: 'draw' rejected when halfMoveClock < 100"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    engine.processUserInput("draw")
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe a[InvalidMoveEvent]
-
-  test("GameEngine: 'draw' accepted and fires DrawClaimedEvent when halfMoveClock >= 100"):
-    val engine = new GameEngine(initialHistory = GameHistory(halfMoveClock = 100))
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    engine.processUserInput("draw")
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe a[DrawClaimedEvent]
-
-  test("GameEngine: state resets to initial after draw claimed"):
-    val engine = new GameEngine(initialHistory = GameHistory(halfMoveClock = 100))
-    engine.processUserInput("draw")
-    engine.board shouldBe Board.initial
-    engine.history shouldBe GameHistory.empty
-    engine.turn shouldBe Color.White
-
-  test("GameEngine: FiftyMoveRuleAvailableEvent fired when move brings clock to 100"):
-    // Start at clock 99; a knight move (non-pawn, non-capture) increments to 100
-    val engine = new GameEngine(initialHistory = GameHistory(halfMoveClock = 99))
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    engine.processUserInput("g1f3")  // knight move on initial board
-    // Should receive MoveExecutedEvent AND FiftyMoveRuleAvailableEvent
-    observer.events.exists(_.isInstanceOf[FiftyMoveRuleAvailableEvent]) shouldBe true
-
-  test("GameEngine: FiftyMoveRuleAvailableEvent not fired when clock is below 100 after move"):
-    val engine = new GameEngine(initialHistory = GameHistory(halfMoveClock = 5))
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    engine.processUserInput("g1f3")
-    observer.events.exists(_.isInstanceOf[FiftyMoveRuleAvailableEvent]) shouldBe false
-
-  // Mock Observer for testing
-  private class MockObserver extends Observer:
-    val events = mutable.ListBuffer[GameEvent]()
-    override def onGameEvent(event: GameEvent): Unit =
-      events += event
-

modules/core/src/test/scala/de/nowchess/chess/engine/MoveCommandDefaultsTest.scala

@@ -1,110 +0,0 @@
-package de.nowchess.chess.command
-
-import de.nowchess.api.board.{Square, File, Rank, Board, Color}
-import de.nowchess.chess.logic.GameHistory
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class MoveCommandDefaultsTest extends AnyFunSuite with Matchers:
-  
-  private def sq(f: File, r: Rank): Square = Square(f, r)
-
-  // Tests for MoveCommand with default parameter values
-  test("MoveCommand with no moveResult defaults to None"):
-    val cmd = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4)
-    )
-    cmd.moveResult shouldBe None
-    cmd.execute() shouldBe false
-
-  test("MoveCommand with no previousBoard defaults to None"):
-    val cmd = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4)
-    )
-    cmd.previousBoard shouldBe None
-    cmd.undo() shouldBe false
-
-  test("MoveCommand with no previousHistory defaults to None"):
-    val cmd = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4)
-    )
-    cmd.previousHistory shouldBe None
-    cmd.undo() shouldBe false
-
-  test("MoveCommand with no previousTurn defaults to None"):
-    val cmd = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4)
-    )
-    cmd.previousTurn shouldBe None
-    cmd.undo() shouldBe false
-
-  test("MoveCommand description is always returned"):
-    val cmd = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4)
-    )
-    cmd.description shouldBe "Move from e2 to e4"
-
-  test("MoveCommand execute returns false when moveResult is None"):
-    val cmd = MoveCommand(
-      from = sq(File.A, Rank.R1),
-      to = sq(File.B, Rank.R3)
-    )
-    cmd.execute() shouldBe false
-
-  test("MoveCommand undo returns false when any previous state is None"):
-    // Missing previousBoard
-    val cmd1 = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4),
-      moveResult = Some(MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)),
-      previousBoard = None,
-      previousHistory = Some(GameHistory.empty),
-      previousTurn = Some(Color.White)
-    )
-    cmd1.undo() shouldBe false
-
-    // Missing previousHistory
-    val cmd2 = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4),
-      moveResult = Some(MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)),
-      previousBoard = Some(Board.initial),
-      previousHistory = None,
-      previousTurn = Some(Color.White)
-    )
-    cmd2.undo() shouldBe false
-
-    // Missing previousTurn
-    val cmd3 = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4),
-      moveResult = Some(MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)),
-      previousBoard = Some(Board.initial),
-      previousHistory = Some(GameHistory.empty),
-      previousTurn = None
-    )
-    cmd3.undo() shouldBe false
-
-  test("MoveCommand execute returns true when moveResult is defined"):
-    val cmd = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4),
-      moveResult = Some(MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None))
-    )
-    cmd.execute() shouldBe true
-
-  test("MoveCommand undo returns true when all previous states are defined"):
-    val cmd = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4),
-      moveResult = Some(MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)),
-      previousBoard = Some(Board.initial),
-      previousHistory = Some(GameHistory.empty),
-      previousTurn = Some(Color.White)
-    )
-    cmd.undo() shouldBe true

modules/core/src/test/scala/de/nowchess/chess/logic/CastlingRightsCalculatorTest.scala

@@ -1,70 +0,0 @@
-package de.nowchess.chess.logic
-
-import de.nowchess.api.board.*
-import de.nowchess.api.game.CastlingRights
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class CastlingRightsCalculatorTest extends AnyFunSuite with Matchers:
-
-  private def sq(f: File, r: Rank): Square = Square(f, r)
-
-  test("Empty history gives full castling rights"):
-    val rights = CastlingRightsCalculator.deriveCastlingRights(GameHistory.empty, Color.White)
-    rights shouldBe CastlingRights.Both
-
-  test("White loses kingside rights after h1 rook moves"):
-    val history = GameHistory.empty.addMove(sq(File.H, Rank.R1), sq(File.H, Rank.R2))
-    val rights = CastlingRightsCalculator.deriveCastlingRights(history, Color.White)
-    rights.kingSide shouldBe false
-    rights.queenSide shouldBe true
-
-  test("White loses queenside rights after a1 rook moves"):
-    val history = GameHistory.empty.addMove(sq(File.A, Rank.R1), sq(File.A, Rank.R2))
-    val rights = CastlingRightsCalculator.deriveCastlingRights(history, Color.White)
-    rights.queenSide shouldBe false
-    rights.kingSide shouldBe true
-
-  test("White loses all rights after king moves"):
-    val history = GameHistory.empty.addMove(sq(File.E, Rank.R1), sq(File.E, Rank.R2))
-    val rights = CastlingRightsCalculator.deriveCastlingRights(history, Color.White)
-    rights shouldBe CastlingRights.None
-
-  test("Black loses kingside rights after h8 rook moves"):
-    val history = GameHistory.empty.addMove(sq(File.H, Rank.R8), sq(File.H, Rank.R7))
-    val rights = CastlingRightsCalculator.deriveCastlingRights(history, Color.Black)
-    rights.kingSide shouldBe false
-    rights.queenSide shouldBe true
-
-  test("Black loses queenside rights after a8 rook moves"):
-    val history = GameHistory.empty.addMove(sq(File.A, Rank.R8), sq(File.A, Rank.R7))
-    val rights = CastlingRightsCalculator.deriveCastlingRights(history, Color.Black)
-    rights.queenSide shouldBe false
-    rights.kingSide shouldBe true
-
-  test("Black loses all rights after king moves"):
-    val history = GameHistory.empty.addMove(sq(File.E, Rank.R8), sq(File.E, Rank.R7))
-    val rights = CastlingRightsCalculator.deriveCastlingRights(history, Color.Black)
-    rights shouldBe CastlingRights.None
-
-  test("Castle move revokes all castling rights"):
-    val history = GameHistory.empty.addMove(
-      sq(File.E, Rank.R1),
-      sq(File.G, Rank.R1),
-      Some(CastleSide.Kingside)
-    )
-    val rights = CastlingRightsCalculator.deriveCastlingRights(history, Color.White)
-    rights shouldBe CastlingRights.None
-
-  test("Other pieces moving does not revoke castling rights"):
-    val history = GameHistory.empty.addMove(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    val rights = CastlingRightsCalculator.deriveCastlingRights(history, Color.White)
-    rights shouldBe CastlingRights.Both
-
-  test("Multiple moves preserve white kingside but lose queenside"):
-    val history = GameHistory.empty
-      .addMove(sq(File.A, Rank.R1), sq(File.A, Rank.R2))  // White queenside rook moves
-      .addMove(sq(File.E, Rank.R7), sq(File.E, Rank.R5))  // Black pawn moves
-    val rights = CastlingRightsCalculator.deriveCastlingRights(history, Color.White)
-    rights.kingSide shouldBe true
-    rights.queenSide shouldBe false

modules/core/src/test/scala/de/nowchess/chess/logic/EnPassantCalculatorTest.scala

@@ -1,101 +0,0 @@
-package de.nowchess.chess.logic
-
-import de.nowchess.api.board.*
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class EnPassantCalculatorTest extends AnyFunSuite with Matchers:
-
-  private def sq(f: File, r: Rank): Square = Square(f, r)
-  private def board(entries: (Square, Piece)*): Board = Board(entries.toMap)
-
-  // ──── enPassantTarget ────────────────────────────────────────────────
-
-  test("enPassantTarget returns None for empty history"):
-    val b = board(sq(File.E, Rank.R4) -> Piece.WhitePawn)
-    EnPassantCalculator.enPassantTarget(b, GameHistory.empty) shouldBe None
-
-  test("enPassantTarget returns None when last move was a single pawn push"):
-    val b = board(sq(File.E, Rank.R3) -> Piece.WhitePawn)
-    val h = GameHistory.empty.addMove(sq(File.E, Rank.R2), sq(File.E, Rank.R3))
-    EnPassantCalculator.enPassantTarget(b, h) shouldBe None
-
-  test("enPassantTarget returns None when last move was not a pawn"):
-    val b = board(sq(File.E, Rank.R4) -> Piece.WhiteRook)
-    val h = GameHistory.empty.addMove(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    EnPassantCalculator.enPassantTarget(b, h) shouldBe None
-
-  test("enPassantTarget returns e3 after white pawn double push e2-e4"):
-    val b = board(sq(File.E, Rank.R4) -> Piece.WhitePawn)
-    val h = GameHistory.empty.addMove(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    EnPassantCalculator.enPassantTarget(b, h) shouldBe Some(sq(File.E, Rank.R3))
-
-  test("enPassantTarget returns e6 after black pawn double push e7-e5"):
-    val b = board(sq(File.E, Rank.R5) -> Piece.BlackPawn)
-    val h = GameHistory.empty.addMove(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
-    EnPassantCalculator.enPassantTarget(b, h) shouldBe Some(sq(File.E, Rank.R6))
-
-  test("enPassantTarget returns d3 after white pawn double push d2-d4"):
-    val b = board(sq(File.D, Rank.R4) -> Piece.WhitePawn)
-    val h = GameHistory.empty.addMove(sq(File.D, Rank.R2), sq(File.D, Rank.R4))
-    EnPassantCalculator.enPassantTarget(b, h) shouldBe Some(sq(File.D, Rank.R3))
-
-  // ──── capturedPawnSquare ─────────────────────────────────────────────
-
-  test("capturedPawnSquare for white capturing on e6 returns e5"):
-    EnPassantCalculator.capturedPawnSquare(sq(File.E, Rank.R6), Color.White) shouldBe sq(File.E, Rank.R5)
-
-  test("capturedPawnSquare for black capturing on e3 returns e4"):
-    EnPassantCalculator.capturedPawnSquare(sq(File.E, Rank.R3), Color.Black) shouldBe sq(File.E, Rank.R4)
-
-  test("capturedPawnSquare for white capturing on d6 returns d5"):
-    EnPassantCalculator.capturedPawnSquare(sq(File.D, Rank.R6), Color.White) shouldBe sq(File.D, Rank.R5)
-
-  // ──── isEnPassant ────────────────────────────────────────────────────
-
-  test("isEnPassant returns true for valid white en passant capture"):
-    // White pawn on e5, black pawn just double-pushed to d5 (ep target = d6)
-    val b = board(
-      sq(File.E, Rank.R5) -> Piece.WhitePawn,
-      sq(File.D, Rank.R5) -> Piece.BlackPawn
-    )
-    val h = GameHistory.empty.addMove(sq(File.D, Rank.R7), sq(File.D, Rank.R5))
-    EnPassantCalculator.isEnPassant(b, h, sq(File.E, Rank.R5), sq(File.D, Rank.R6)) shouldBe true
-
-  test("isEnPassant returns true for valid black en passant capture"):
-    // Black pawn on d4, white pawn just double-pushed to e4 (ep target = e3)
-    val b = board(
-      sq(File.D, Rank.R4) -> Piece.BlackPawn,
-      sq(File.E, Rank.R4) -> Piece.WhitePawn
-    )
-    val h = GameHistory.empty.addMove(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    EnPassantCalculator.isEnPassant(b, h, sq(File.D, Rank.R4), sq(File.E, Rank.R3)) shouldBe true
-
-  test("isEnPassant returns false when no en passant target in history"):
-    val b = board(
-      sq(File.E, Rank.R5) -> Piece.WhitePawn,
-      sq(File.D, Rank.R5) -> Piece.BlackPawn
-    )
-    val h = GameHistory.empty.addMove(sq(File.D, Rank.R6), sq(File.D, Rank.R5))  // single push
-    EnPassantCalculator.isEnPassant(b, h, sq(File.E, Rank.R5), sq(File.D, Rank.R6)) shouldBe false
-
-  test("isEnPassant returns false when piece at from is not a pawn"):
-    val b = board(
-      sq(File.E, Rank.R5) -> Piece.WhiteRook,
-      sq(File.D, Rank.R5) -> Piece.BlackPawn
-    )
-    val h = GameHistory.empty.addMove(sq(File.D, Rank.R7), sq(File.D, Rank.R5))
-    EnPassantCalculator.isEnPassant(b, h, sq(File.E, Rank.R5), sq(File.D, Rank.R6)) shouldBe false
-
-  test("isEnPassant returns false when to does not match ep target"):
-    val b = board(
-      sq(File.E, Rank.R5) -> Piece.WhitePawn,
-      sq(File.D, Rank.R5) -> Piece.BlackPawn
-    )
-    val h = GameHistory.empty.addMove(sq(File.D, Rank.R7), sq(File.D, Rank.R5))
-    EnPassantCalculator.isEnPassant(b, h, sq(File.E, Rank.R5), sq(File.E, Rank.R6)) shouldBe false
-
-  test("isEnPassant returns false when from square is empty"):
-    val b = board(sq(File.D, Rank.R5) -> Piece.BlackPawn)
-    val h = GameHistory.empty.addMove(sq(File.D, Rank.R7), sq(File.D, Rank.R5))
-    EnPassantCalculator.isEnPassant(b, h, sq(File.E, Rank.R5), sq(File.D, Rank.R6)) shouldBe false

modules/core/src/test/scala/de/nowchess/chess/logic/GameHistoryTest.scala

@@ -1,104 +0,0 @@
-package de.nowchess.chess.logic
-
-import de.nowchess.api.board.*
-import de.nowchess.api.move.PromotionPiece
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class GameHistoryTest extends AnyFunSuite with Matchers:
-
-  private def sq(f: File, r: Rank): Square = Square(f, r)
-
-  test("GameHistory starts empty"):
-    val history = GameHistory.empty
-    history.moves shouldBe empty
-
-  test("GameHistory can add a move"):
-    val history = GameHistory.empty.addMove(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    history.moves should have length 1
-    history.moves.head.from shouldBe sq(File.E, Rank.R2)
-    history.moves.head.to shouldBe sq(File.E, Rank.R4)
-    history.moves.head.castleSide shouldBe None
-
-  test("GameHistory can add multiple moves in order"):
-    val h1 = GameHistory.empty
-    val h2 = h1.addMove(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    val h3 = h2.addMove(sq(File.C, Rank.R7), sq(File.C, Rank.R5))
-    h3.moves should have length 2
-    h3.moves(0).from shouldBe sq(File.E, Rank.R2)
-    h3.moves(1).from shouldBe sq(File.C, Rank.R7)
-
-  test("GameHistory can add a castle move"):
-    val history = GameHistory.empty.addMove(
-      sq(File.E, Rank.R1),
-      sq(File.G, Rank.R1),
-      Some(CastleSide.Kingside)
-    )
-    history.moves.head.castleSide shouldBe Some(CastleSide.Kingside)
-
-  test("GameHistory.addMove with two arguments uses None for castleSide default"):
-    val history = GameHistory.empty.addMove(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    history.moves should have length 1
-    history.moves.head.castleSide shouldBe None
-
-  test("Move with promotion records the promotion piece"):
-    val move = HistoryMove(sq(File.E, Rank.R7), sq(File.E, Rank.R8), None, Some(PromotionPiece.Queen))
-    move.promotionPiece should be (Some(PromotionPiece.Queen))
-
-  test("Normal move has no promotion piece"):
-    val move = HistoryMove(sq(File.E, Rank.R2), sq(File.E, Rank.R4), None, None)
-    move.promotionPiece should be (None)
-
-  test("addMove with promotion stores promotionPiece"):
-    val history = GameHistory.empty
-    val newHistory = history.addMove(sq(File.E, Rank.R7), sq(File.E, Rank.R8), None, Some(PromotionPiece.Rook))
-    newHistory.moves should have length 1
-    newHistory.moves.head.promotionPiece should be (Some(PromotionPiece.Rook))
-
-  test("addMove with castleSide only uses promotionPiece default (None)"):
-    val history = GameHistory.empty
-    // With overload 3 removed, this uses the 4-param version and triggers addMove$default$4
-    val newHistory = history.addMove(sq(File.E, Rank.R1), sq(File.G, Rank.R1), Some(CastleSide.Kingside))
-    newHistory.moves should have length 1
-    newHistory.moves.head.castleSide should be (Some(CastleSide.Kingside))
-    newHistory.moves.head.promotionPiece should be (None)
-
-  test("addMove using named parameters with only promotion, using castleSide default"):
-    val history = GameHistory.empty
-    val newHistory = history.addMove(from = sq(File.E, Rank.R7), to = sq(File.E, Rank.R8), promotionPiece = Some(PromotionPiece.Queen))
-    newHistory.moves should have length 1
-    newHistory.moves.head.castleSide should be (None)
-    newHistory.moves.head.promotionPiece should be (Some(PromotionPiece.Queen))
-
-  // ──── half-move clock ────────────────────────────────────────────────
-
-  test("halfMoveClock starts at 0"):
-    GameHistory.empty.halfMoveClock shouldBe 0
-
-  test("halfMoveClock increments on a non-pawn non-capture move"):
-    val h = GameHistory.empty.addMove(sq(File.G, Rank.R1), sq(File.F, Rank.R3))
-    h.halfMoveClock shouldBe 1
-
-  test("halfMoveClock resets to 0 on a pawn move"):
-    val h = GameHistory.empty.addMove(sq(File.E, Rank.R2), sq(File.E, Rank.R4), wasPawnMove = true)
-    h.halfMoveClock shouldBe 0
-
-  test("halfMoveClock resets to 0 on a capture"):
-    val h = GameHistory.empty.addMove(sq(File.E, Rank.R5), sq(File.D, Rank.R6), wasCapture = true)
-    h.halfMoveClock shouldBe 0
-
-  test("halfMoveClock resets to 0 when both wasPawnMove and wasCapture are true"):
-    val h = GameHistory.empty.addMove(sq(File.E, Rank.R5), sq(File.D, Rank.R6), wasPawnMove = true, wasCapture = true)
-    h.halfMoveClock shouldBe 0
-
-  test("halfMoveClock carries across multiple moves"):
-    val h = GameHistory.empty
-      .addMove(sq(File.G, Rank.R1), sq(File.F, Rank.R3))          // +1 → 1
-      .addMove(sq(File.G, Rank.R8), sq(File.F, Rank.R6))          // +1 → 2
-      .addMove(sq(File.E, Rank.R2), sq(File.E, Rank.R4), wasPawnMove = true)  // reset → 0
-      .addMove(sq(File.B, Rank.R1), sq(File.C, Rank.R3))          // +1 → 1
-    h.halfMoveClock shouldBe 1
-
-  test("GameHistory can be initialised with a non-zero halfMoveClock"):
-    val h = GameHistory(halfMoveClock = 42)
-    h.halfMoveClock shouldBe 42

modules/core/src/test/scala/de/nowchess/chess/logic/GameRulesTest.scala

@@ -1,161 +0,0 @@
-package de.nowchess.chess.logic
-
-import de.nowchess.api.board.*
-import de.nowchess.api.game.CastlingRights
-import de.nowchess.chess.logic.GameHistory
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class GameRulesTest extends AnyFunSuite with Matchers:
-
-  private def sq(f: File, r: Rank): Square = Square(f, r)
-  private def board(entries: (Square, Piece)*): Board = Board(entries.toMap)
-
-  /** Wrap a board in a GameContext with no castling rights — for non-castling tests. */
-  private def testLegalMoves(entries: (Square, Piece)*)(color: Color): Set[(Square, Square)] =
-    GameRules.legalMoves(Board(entries.toMap), GameHistory.empty, color)
-
-  private def testGameStatus(entries: (Square, Piece)*)(color: Color): PositionStatus =
-    GameRules.gameStatus(Board(entries.toMap), GameHistory.empty, color)
-
-  // ──── isInCheck ──────────────────────────────────────────────────────
-
-  test("isInCheck: king attacked by enemy rook on same rank"):
-    // White King E1, Black Rook A1 — rook slides along rank 1 to E1
-    val b = board(
-      sq(File.E, Rank.R1) -> Piece.WhiteKing,
-      sq(File.A, Rank.R1) -> Piece.BlackRook
-    )
-    GameRules.isInCheck(b, Color.White) shouldBe true
-
-  test("isInCheck: king not attacked"):
-    // Black Rook A3 does not cover E1
-    val b = board(
-      sq(File.E, Rank.R1) -> Piece.WhiteKing,
-      sq(File.A, Rank.R3) -> Piece.BlackRook
-    )
-    GameRules.isInCheck(b, Color.White) shouldBe false
-
-  test("isInCheck: no king on board returns false"):
-    val b = board(sq(File.A, Rank.R1) -> Piece.BlackRook)
-    GameRules.isInCheck(b, Color.White) shouldBe false
-
-  // ──── legalMoves ─────────────────────────────────────────────────────
-
-  test("legalMoves: move that exposes own king to rook is excluded"):
-    // White King E1, White Rook E4 (pinned on E-file), Black Rook E8
-    // Moving the White Rook off the E-file would expose the king
-    val moves = testLegalMoves(
-      sq(File.E, Rank.R1) -> Piece.WhiteKing,
-      sq(File.E, Rank.R4) -> Piece.WhiteRook,
-      sq(File.E, Rank.R8) -> Piece.BlackRook
-    )(Color.White)
-    moves should not contain (sq(File.E, Rank.R4) -> sq(File.D, Rank.R4))
-
-  test("legalMoves: move that blocks check is included"):
-    // White King E1 in check from Black Rook E8; White Rook A5 can interpose on E5
-    val moves = testLegalMoves(
-      sq(File.E, Rank.R1) -> Piece.WhiteKing,
-      sq(File.A, Rank.R5) -> Piece.WhiteRook,
-      sq(File.E, Rank.R8) -> Piece.BlackRook
-    )(Color.White)
-    moves should contain(sq(File.A, Rank.R5) -> sq(File.E, Rank.R5))
-
-  // ──── gameStatus ──────────────────────────────────────────────────────
-
-  test("gameStatus: checkmate returns Mated"):
-    // White Qh8, Ka6; Black Ka8
-    // Qh8 attacks Ka8 along rank 8; all escape squares covered (spec-verified position)
-    testGameStatus(
-      sq(File.H, Rank.R8) -> Piece.WhiteQueen,
-      sq(File.A, Rank.R6) -> Piece.WhiteKing,
-      sq(File.A, Rank.R8) -> Piece.BlackKing
-    )(Color.Black) shouldBe PositionStatus.Mated
-
-  test("gameStatus: stalemate returns Drawn"):
-    // White Qb6, Kc6; Black Ka8
-    // Black king has no legal moves and is not in check (spec-verified position)
-    testGameStatus(
-      sq(File.B, Rank.R6) -> Piece.WhiteQueen,
-      sq(File.C, Rank.R6) -> Piece.WhiteKing,
-      sq(File.A, Rank.R8) -> Piece.BlackKing
-    )(Color.Black) shouldBe PositionStatus.Drawn
-
-  test("gameStatus: king in check with legal escape returns InCheck"):
-    // White Ra8 attacks Black Ke8 along rank 8; king can escape to d7, e7, f7
-    testGameStatus(
-      sq(File.A, Rank.R8) -> Piece.WhiteRook,
-      sq(File.E, Rank.R8) -> Piece.BlackKing
-    )(Color.Black) shouldBe PositionStatus.InCheck
-
-  test("gameStatus: normal starting position returns Normal"):
-    GameRules.gameStatus(Board.initial, GameHistory.empty, Color.White) shouldBe PositionStatus.Normal
-
-  test("legalMoves: includes castling destination when available"):
-    val b = board(
-        sq(File.E, Rank.R1) -> Piece.WhiteKing,
-        sq(File.H, Rank.R1) -> Piece.WhiteRook,
-        sq(File.H, Rank.R8) -> Piece.BlackKing
-      )
-    GameRules.legalMoves(b, GameHistory.empty, Color.White) should contain(sq(File.E, Rank.R1) -> sq(File.G, Rank.R1))
-
-  test("legalMoves: excludes castling when king is in check"):
-    val b = board(
-        sq(File.E, Rank.R1) -> Piece.WhiteKing,
-        sq(File.H, Rank.R1) -> Piece.WhiteRook,
-        sq(File.E, Rank.R8) -> Piece.BlackRook,
-        sq(File.A, Rank.R8) -> Piece.BlackKing
-      )
-    GameRules.legalMoves(b, GameHistory.empty, Color.White) should not contain (sq(File.E, Rank.R1) -> sq(File.G, Rank.R1))
-
-  test("gameStatus: returns Normal (not Drawn) when castling is the only legal move"):
-    // White King e1, Rook h1 (kingside castling available).
-    // Black Rooks d2 and f2 box the king: d1 attacked by d2, e2 attacked by both,
-    // f1 attacked by f2. King cannot move to any adjacent square without entering
-    // an attacked square or an enemy piece. Only legal move: castle to g1.
-    val b = board(
-        sq(File.E, Rank.R1) -> Piece.WhiteKing,
-        sq(File.H, Rank.R1) -> Piece.WhiteRook,
-        sq(File.D, Rank.R2) -> Piece.BlackRook,
-        sq(File.F, Rank.R2) -> Piece.BlackRook,
-        sq(File.A, Rank.R8) -> Piece.BlackKing
-      )
-    // No history means castling rights are intact
-    GameRules.gameStatus(b, GameHistory.empty, Color.White) shouldBe PositionStatus.Normal
-
-  test("CastleSide.withCastle correctly positions pieces for Queenside castling"):
-    // Directly test the withCastle extension for Queenside (coverage gap on line 10)
-    val b = board(
-      sq(File.E, Rank.R1) -> Piece.WhiteKing,
-      sq(File.A, Rank.R1) -> Piece.WhiteRook,
-      sq(File.H, Rank.R8) -> Piece.BlackKing
-    )
-    val result = b.withCastle(Color.White, CastleSide.Queenside)
-    result.pieceAt(sq(File.C, Rank.R1)) shouldBe Some(Piece.WhiteKing)
-    result.pieceAt(sq(File.D, Rank.R1)) shouldBe Some(Piece.WhiteRook)
-    result.pieceAt(sq(File.E, Rank.R1)) shouldBe None
-    result.pieceAt(sq(File.A, Rank.R1)) shouldBe None
-
-  test("CastleSide.withCastle correctly positions pieces for Black Kingside castling"):
-    val b = board(
-      sq(File.E, Rank.R8) -> Piece.BlackKing,
-      sq(File.H, Rank.R8) -> Piece.BlackRook,
-      sq(File.A, Rank.R1) -> Piece.WhiteKing
-    )
-    val result = b.withCastle(Color.Black, CastleSide.Kingside)
-    result.pieceAt(sq(File.G, Rank.R8)) shouldBe Some(Piece.BlackKing)
-    result.pieceAt(sq(File.F, Rank.R8)) shouldBe Some(Piece.BlackRook)
-    result.pieceAt(sq(File.E, Rank.R8)) shouldBe None
-    result.pieceAt(sq(File.H, Rank.R8)) shouldBe None
-
-  test("CastleSide.withCastle correctly positions pieces for Black Queenside castling"):
-    val b = board(
-      sq(File.E, Rank.R8) -> Piece.BlackKing,
-      sq(File.A, Rank.R8) -> Piece.BlackRook,
-      sq(File.A, Rank.R1) -> Piece.WhiteKing
-    )
-    val result = b.withCastle(Color.Black, CastleSide.Queenside)
-    result.pieceAt(sq(File.C, Rank.R8)) shouldBe Some(Piece.BlackKing)
-    result.pieceAt(sq(File.D, Rank.R8)) shouldBe Some(Piece.BlackRook)
-    result.pieceAt(sq(File.E, Rank.R8)) shouldBe None
-    result.pieceAt(sq(File.A, Rank.R8)) shouldBe None

modules/core/src/test/scala/de/nowchess/chess/logic/MoveValidatorTest.scala

@@ -1,280 +0,0 @@
-package de.nowchess.chess.logic
-
-import de.nowchess.api.board.{Board, Color, File, Piece, Rank, Square}
-import de.nowchess.api.game.CastlingRights
-import de.nowchess.chess.logic.{CastleSide, GameHistory}
-import de.nowchess.chess.notation.FenParser
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class MoveValidatorTest extends AnyFunSuite with Matchers:
-
-  private def sq(f: File, r: Rank): Square = Square(f, r)
-  private def board(entries: (Square, Piece)*): Board = Board(entries.toMap)
-
-  // ──── Empty square ───────────────────────────────────────────────────
-
-  test("legalTargets returns empty set when no piece at from square"):
-    MoveValidator.legalTargets(Board.initial, sq(File.E, Rank.R4)) shouldBe empty
-
-  // ──── isLegal delegates to legalTargets ──────────────────────────────
-
-  test("isLegal returns true for a valid pawn move"):
-    MoveValidator.isLegal(Board.initial, sq(File.E, Rank.R2), sq(File.E, Rank.R4)) shouldBe true
-
-  test("isLegal returns false for an invalid move"):
-    MoveValidator.isLegal(Board.initial, sq(File.E, Rank.R2), sq(File.E, Rank.R5)) shouldBe false
-
-  // ──── Pawn – White ───────────────────────────────────────────────────
-
-  test("white pawn on starting rank can move forward one square"):
-    val b = board(sq(File.E, Rank.R2) -> Piece.WhitePawn)
-    MoveValidator.legalTargets(b, sq(File.E, Rank.R2)) should contain(sq(File.E, Rank.R3))
-
-  test("white pawn on starting rank can move forward two squares"):
-    val b = board(sq(File.E, Rank.R2) -> Piece.WhitePawn)
-    MoveValidator.legalTargets(b, sq(File.E, Rank.R2)) should contain(sq(File.E, Rank.R4))
-
-  test("white pawn not on starting rank cannot move two squares"):
-    val b = board(sq(File.E, Rank.R3) -> Piece.WhitePawn)
-    MoveValidator.legalTargets(b, sq(File.E, Rank.R3)) should not contain sq(File.E, Rank.R5)
-
-  test("white pawn is blocked by piece directly in front, and cannot jump over it"):
-    val b = board(
-      sq(File.E, Rank.R2) -> Piece.WhitePawn,
-      sq(File.E, Rank.R3) -> Piece.BlackPawn
-    )
-    val targets = MoveValidator.legalTargets(b, sq(File.E, Rank.R2))
-    targets should not contain sq(File.E, Rank.R3)
-    targets should not contain sq(File.E, Rank.R4)
-
-  test("white pawn on starting rank cannot move two squares if destination square is occupied"):
-    val b = board(
-      sq(File.E, Rank.R2) -> Piece.WhitePawn,
-      sq(File.E, Rank.R4) -> Piece.BlackPawn
-    )
-    val targets = MoveValidator.legalTargets(b, sq(File.E, Rank.R2))
-    targets should contain(sq(File.E, Rank.R3))
-    targets should not contain sq(File.E, Rank.R4)
-
-  test("white pawn can capture diagonally when enemy piece is present"):
-    val b = board(
-      sq(File.E, Rank.R2) -> Piece.WhitePawn,
-      sq(File.D, Rank.R3) -> Piece.BlackPawn
-    )
-    MoveValidator.legalTargets(b, sq(File.E, Rank.R2)) should contain(sq(File.D, Rank.R3))
-
-  test("white pawn cannot capture diagonally when no enemy piece is present"):
-    val b = board(sq(File.E, Rank.R2) -> Piece.WhitePawn)
-    MoveValidator.legalTargets(b, sq(File.E, Rank.R2)) should not contain sq(File.D, Rank.R3)
-
-  test("white pawn at A-file does not generate diagonal to the left off the board"):
-    val b = board(sq(File.A, Rank.R2) -> Piece.WhitePawn)
-    val targets = MoveValidator.legalTargets(b, sq(File.A, Rank.R2))
-    targets should contain(sq(File.A, Rank.R3))
-    targets should contain(sq(File.A, Rank.R4))
-    targets.size shouldBe 2
-
-  // ──── Pawn – Black ───────────────────────────────────────────────────
-
-  test("black pawn on starting rank can move forward one and two squares"):
-    val b = board(sq(File.E, Rank.R7) -> Piece.BlackPawn)
-    val targets = MoveValidator.legalTargets(b, sq(File.E, Rank.R7))
-    targets should contain(sq(File.E, Rank.R6))
-    targets should contain(sq(File.E, Rank.R5))
-
-  test("black pawn not on starting rank cannot move two squares"):
-    val b = board(sq(File.E, Rank.R6) -> Piece.BlackPawn)
-    MoveValidator.legalTargets(b, sq(File.E, Rank.R6)) should not contain sq(File.E, Rank.R4)
-
-  test("black pawn can capture diagonally when enemy piece is present"):
-    val b = board(
-      sq(File.E, Rank.R7) -> Piece.BlackPawn,
-      sq(File.F, Rank.R6) -> Piece.WhitePawn
-    )
-    MoveValidator.legalTargets(b, sq(File.E, Rank.R7)) should contain(sq(File.F, Rank.R6))
-
-  // ──── Knight ─────────────────────────────────────────────────────────
-
-  test("knight in center has 8 possible moves"):
-    val b = board(sq(File.D, Rank.R4) -> Piece.WhiteKnight)
-    MoveValidator.legalTargets(b, sq(File.D, Rank.R4)).size shouldBe 8
-
-  test("knight in corner has only 2 possible moves"):
-    val b = board(sq(File.A, Rank.R1) -> Piece.WhiteKnight)
-    MoveValidator.legalTargets(b, sq(File.A, Rank.R1)).size shouldBe 2
-
-  test("knight cannot land on own piece"):
-    val b = board(
-      sq(File.D, Rank.R4) -> Piece.WhiteKnight,
-      sq(File.F, Rank.R5) -> Piece.WhiteRook
-    )
-    MoveValidator.legalTargets(b, sq(File.D, Rank.R4)) should not contain sq(File.F, Rank.R5)
-
-  test("knight can capture enemy piece"):
-    val b = board(
-      sq(File.D, Rank.R4) -> Piece.WhiteKnight,
-      sq(File.F, Rank.R5) -> Piece.BlackRook
-    )
-    MoveValidator.legalTargets(b, sq(File.D, Rank.R4)) should contain(sq(File.F, Rank.R5))
-
-  // ──── Bishop ─────────────────────────────────────────────────────────
-
-  test("bishop slides diagonally across an empty board"):
-    val b = board(sq(File.D, Rank.R4) -> Piece.WhiteBishop)
-    val targets = MoveValidator.legalTargets(b, sq(File.D, Rank.R4))
-    targets should contain(sq(File.E, Rank.R5))
-    targets should contain(sq(File.H, Rank.R8))
-    targets should contain(sq(File.C, Rank.R3))
-    targets should contain(sq(File.A, Rank.R1))
-
-  test("bishop is blocked by own piece and squares beyond are unreachable"):
-    val b = board(
-      sq(File.D, Rank.R4) -> Piece.WhiteBishop,
-      sq(File.F, Rank.R6) -> Piece.WhiteRook
-    )
-    val targets = MoveValidator.legalTargets(b, sq(File.D, Rank.R4))
-    targets should contain(sq(File.E, Rank.R5))
-    targets should not contain sq(File.F, Rank.R6)
-    targets should not contain sq(File.G, Rank.R7)
-
-  test("bishop captures enemy piece and cannot slide further"):
-    val b = board(
-      sq(File.D, Rank.R4) -> Piece.WhiteBishop,
-      sq(File.F, Rank.R6) -> Piece.BlackRook
-    )
-    val targets = MoveValidator.legalTargets(b, sq(File.D, Rank.R4))
-    targets should contain(sq(File.E, Rank.R5))
-    targets should contain(sq(File.F, Rank.R6))
-    targets should not contain sq(File.G, Rank.R7)
-
-  // ──── Rook ───────────────────────────────────────────────────────────
-
-  test("rook slides orthogonally across an empty board"):
-    val b = board(sq(File.D, Rank.R4) -> Piece.WhiteRook)
-    val targets = MoveValidator.legalTargets(b, sq(File.D, Rank.R4))
-    targets should contain(sq(File.D, Rank.R8))
-    targets should contain(sq(File.D, Rank.R1))
-    targets should contain(sq(File.A, Rank.R4))
-    targets should contain(sq(File.H, Rank.R4))
-
-  test("rook is blocked by own piece and squares beyond are unreachable"):
-    val b = board(
-      sq(File.A, Rank.R1) -> Piece.WhiteRook,
-      sq(File.C, Rank.R1) -> Piece.WhitePawn
-    )
-    val targets = MoveValidator.legalTargets(b, sq(File.A, Rank.R1))
-    targets should contain(sq(File.B, Rank.R1))
-    targets should not contain sq(File.C, Rank.R1)
-    targets should not contain sq(File.D, Rank.R1)
-
-  test("rook captures enemy piece and cannot slide further"):
-    val b = board(
-      sq(File.A, Rank.R1) -> Piece.WhiteRook,
-      sq(File.C, Rank.R1) -> Piece.BlackPawn
-    )
-    val targets = MoveValidator.legalTargets(b, sq(File.A, Rank.R1))
-    targets should contain(sq(File.B, Rank.R1))
-    targets should contain(sq(File.C, Rank.R1))
-    targets should not contain sq(File.D, Rank.R1)
-
-  // ──── Queen ──────────────────────────────────────────────────────────
-
-  test("queen combines rook and bishop movement for 27 squares from d4"):
-    val b = board(sq(File.D, Rank.R4) -> Piece.WhiteQueen)
-    val targets = MoveValidator.legalTargets(b, sq(File.D, Rank.R4))
-    targets should contain(sq(File.D, Rank.R8))
-    targets should contain(sq(File.H, Rank.R4))
-    targets should contain(sq(File.H, Rank.R8))
-    targets should contain(sq(File.A, Rank.R1))
-    targets.size shouldBe 27
-
-  // ──── King ───────────────────────────────────────────────────────────
-
-  test("king moves one step in all 8 directions from center"):
-    val b = board(sq(File.D, Rank.R4) -> Piece.WhiteKing)
-    MoveValidator.legalTargets(b, sq(File.D, Rank.R4)).size shouldBe 8
-
-  test("king at corner has only 3 reachable squares"):
-    val b = board(sq(File.A, Rank.R1) -> Piece.WhiteKing)
-    MoveValidator.legalTargets(b, sq(File.A, Rank.R1)).size shouldBe 3
-
-  test("king cannot capture own piece"):
-    val b = board(
-      sq(File.D, Rank.R4) -> Piece.WhiteKing,
-      sq(File.E, Rank.R4) -> Piece.WhiteRook
-    )
-    MoveValidator.legalTargets(b, sq(File.D, Rank.R4)) should not contain sq(File.E, Rank.R4)
-
-  test("king can capture enemy piece"):
-    val b = board(
-      sq(File.D, Rank.R4) -> Piece.WhiteKing,
-      sq(File.E, Rank.R4) -> Piece.BlackRook
-    )
-    MoveValidator.legalTargets(b, sq(File.D, Rank.R4)) should contain(sq(File.E, Rank.R4))
-
-  // ──── Pawn – en passant targets ──────────────────────────────────────
-
-  test("white pawn includes ep target in legal moves after black double push"):
-    // Black pawn just double-pushed to d5 (ep target = d6); white pawn on e5
-    val b = board(
-      sq(File.E, Rank.R5) -> Piece.WhitePawn,
-      sq(File.D, Rank.R5) -> Piece.BlackPawn
-    )
-    val h = GameHistory.empty.addMove(sq(File.D, Rank.R7), sq(File.D, Rank.R5))
-    MoveValidator.legalTargets(b, h, sq(File.E, Rank.R5)) should contain(sq(File.D, Rank.R6))
-
-  test("white pawn does not include ep target without a preceding double push"):
-    val b = board(
-      sq(File.E, Rank.R5) -> Piece.WhitePawn,
-      sq(File.D, Rank.R5) -> Piece.BlackPawn
-    )
-    val h = GameHistory.empty.addMove(sq(File.D, Rank.R6), sq(File.D, Rank.R5))  // single push
-    MoveValidator.legalTargets(b, h, sq(File.E, Rank.R5)) should not contain sq(File.D, Rank.R6)
-
-  test("black pawn includes ep target in legal moves after white double push"):
-    // White pawn just double-pushed to e4 (ep target = e3); black pawn on d4
-    val b = board(
-      sq(File.D, Rank.R4) -> Piece.BlackPawn,
-      sq(File.E, Rank.R4) -> Piece.WhitePawn
-    )
-    val h = GameHistory.empty.addMove(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    MoveValidator.legalTargets(b, h, sq(File.D, Rank.R4)) should contain(sq(File.E, Rank.R3))
-
-  test("pawn on wrong file does not get ep target from adjacent double push"):
-    // White pawn on a5, black pawn double-pushed to d5 — a5 is not adjacent to d5
-    val b = board(
-      sq(File.A, Rank.R5) -> Piece.WhitePawn,
-      sq(File.D, Rank.R5) -> Piece.BlackPawn
-    )
-    val h = GameHistory.empty.addMove(sq(File.D, Rank.R7), sq(File.D, Rank.R5))
-    MoveValidator.legalTargets(b, h, sq(File.A, Rank.R5)) should not contain sq(File.D, Rank.R6)
-
-  // ──── History-aware legalTargets fallback for non-pawn non-king pieces ─────
-
-  test("legalTargets with history delegates to geometry-only for non-pawn non-king pieces"):
-    val b = board(sq(File.D, Rank.R4) -> Piece.WhiteRook)
-    val h = GameHistory.empty.addMove(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    MoveValidator.legalTargets(b, h, sq(File.D, Rank.R4)) shouldBe MoveValidator.legalTargets(b, sq(File.D, Rank.R4))
-
-  // ──── isPromotionMove ────────────────────────────────────────────────
-
-  test("White pawn reaching R8 is a promotion move"):
-    val b = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    MoveValidator.isPromotionMove(b, Square(File.E, Rank.R7), Square(File.E, Rank.R8)) should be (true)
-
-  test("Black pawn reaching R1 is a promotion move"):
-    val b = FenParser.parseBoard("8/8/8/8/4K3/8/4p3/8").get
-    MoveValidator.isPromotionMove(b, Square(File.E, Rank.R2), Square(File.E, Rank.R1)) should be (true)
-
-  test("Pawn capturing to back rank is a promotion move"):
-    val b = FenParser.parseBoard("3q4/4P3/8/8/8/8/8/8").get
-    MoveValidator.isPromotionMove(b, Square(File.E, Rank.R7), Square(File.D, Rank.R8)) should be (true)
-
-  test("Pawn not reaching back rank is not a promotion move"):
-    val b = FenParser.parseBoard("8/8/8/4P3/8/8/8/8").get
-    MoveValidator.isPromotionMove(b, Square(File.E, Rank.R5), Square(File.E, Rank.R6)) should be (false)
-
-  test("Non-pawn piece is never a promotion move"):
-    val b = FenParser.parseBoard("8/8/8/4Q3/8/8/8/8").get
-    MoveValidator.isPromotionMove(b, Square(File.E, Rank.R5), Square(File.E, Rank.R8)) should be (false)

modules/core/src/test/scala/de/nowchess/chess/notation/FenExporterTest.scala

@@ -1,88 +0,0 @@
-package de.nowchess.chess.notation
-
-import de.nowchess.api.board.*
-import de.nowchess.api.game.*
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class FenExporterTest extends AnyFunSuite with Matchers:
-
-  test("export initial position to FEN"):
-    val gameState = GameState.initial
-    val fen = FenExporter.gameStateToFen(gameState)
-    fen shouldBe "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"
-
-  test("export position after e4"):
-    val gameState = GameState(
-      piecePlacement = "rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR",
-      activeColor = Color.Black,
-      castlingWhite = CastlingRights.Both,
-      castlingBlack = CastlingRights.Both,
-      enPassantTarget = Some(Square(File.E, Rank.R3)),
-      halfMoveClock = 0,
-      fullMoveNumber = 1,
-      status = GameStatus.InProgress
-    )
-    val fen = FenExporter.gameStateToFen(gameState)
-    fen shouldBe "rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq e3 0 1"
-
-  test("export position with no castling"):
-    val gameState = GameState(
-      piecePlacement = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR",
-      activeColor = Color.White,
-      castlingWhite = CastlingRights.None,
-      castlingBlack = CastlingRights.None,
-      enPassantTarget = None,
-      halfMoveClock = 0,
-      fullMoveNumber = 1,
-      status = GameStatus.InProgress
-    )
-    val fen = FenExporter.gameStateToFen(gameState)
-    fen shouldBe "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w - - 0 1"
-
-  test("export position with partial castling"):
-    val gameState = GameState(
-      piecePlacement = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR",
-      activeColor = Color.White,
-      castlingWhite = CastlingRights(kingSide = true, queenSide = false),
-      castlingBlack = CastlingRights(kingSide = false, queenSide = true),
-      enPassantTarget = None,
-      halfMoveClock = 5,
-      fullMoveNumber = 3,
-      status = GameStatus.InProgress
-    )
-    val fen = FenExporter.gameStateToFen(gameState)
-    fen shouldBe "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w Kq - 5 3"
-
-  test("export position with en passant and move counts"):
-    val gameState = GameState(
-      piecePlacement = "rnbqkbnr/pp1ppppp/8/2pP4/8/8/PPPP1PPP/RNBQKBNR",
-      activeColor = Color.White,
-      castlingWhite = CastlingRights.Both,
-      castlingBlack = CastlingRights.Both,
-      enPassantTarget = Some(Square(File.C, Rank.R6)),
-      halfMoveClock = 2,
-      fullMoveNumber = 3,
-      status = GameStatus.InProgress
-    )
-    val fen = FenExporter.gameStateToFen(gameState)
-    fen shouldBe "rnbqkbnr/pp1ppppp/8/2pP4/8/8/PPPP1PPP/RNBQKBNR w KQkq c6 2 3"
-
-  test("halfMoveClock round-trips through FEN export and import"):
-    import de.nowchess.chess.logic.GameHistory
-    import de.nowchess.chess.notation.FenParser
-    val history = GameHistory(halfMoveClock = 42)
-    val gameState = GameState(
-      piecePlacement  = FenExporter.boardToFen(de.nowchess.api.board.Board.initial),
-      activeColor     = Color.White,
-      castlingWhite   = CastlingRights.Both,
-      castlingBlack   = CastlingRights.Both,
-      enPassantTarget = None,
-      halfMoveClock   = history.halfMoveClock,
-      fullMoveNumber  = 1,
-      status          = GameStatus.InProgress
-    )
-    val fen    = FenExporter.gameStateToFen(gameState)
-    FenParser.parseFen(fen) match
-      case Some(gs) => gs.halfMoveClock shouldBe 42
-      case None     => fail("FEN parsing failed")

modules/core/src/test/scala/de/nowchess/chess/notation/FenParserTest.scala

@@ -1,134 +0,0 @@
-package de.nowchess.chess.notation
-
-import de.nowchess.api.board.*
-import de.nowchess.api.game.*
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class FenParserTest extends AnyFunSuite with Matchers:
-
-  test("parseBoard: initial position places pieces on correct squares"):
-    val fen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR"
-    val board = FenParser.parseBoard(fen)
-
-    board.map(_.pieceAt(Square(File.E, Rank.R2))) shouldBe Some(Some(Piece.WhitePawn))
-    board.map(_.pieceAt(Square(File.E, Rank.R7))) shouldBe Some(Some(Piece.BlackPawn))
-    board.map(_.pieceAt(Square(File.E, Rank.R1))) shouldBe Some(Some(Piece.WhiteKing))
-    board.map(_.pieceAt(Square(File.E, Rank.R8))) shouldBe Some(Some(Piece.BlackKing))
-
-  test("parseBoard: empty board has no pieces"):
-    val fen = "8/8/8/8/8/8/8/8"
-    val board = FenParser.parseBoard(fen)
-
-    board shouldBe defined
-    board.get.pieces.size shouldBe 0
-
-  test("parseBoard: returns None for missing rank (only 7 ranks)"):
-    val fen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP"
-    val board = FenParser.parseBoard(fen)
-
-    board shouldBe empty
-
-  test("parseBoard: returns None for invalid piece character"):
-    val fen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNX"
-    val board = FenParser.parseBoard(fen)
-
-    board shouldBe empty
-
-  test("parseBoard: partial position with two kings placed correctly"):
-    val fen = "8/8/4k3/8/4K3/8/8/8"
-    val board = FenParser.parseBoard(fen)
-
-    board.map(_.pieceAt(Square(File.E, Rank.R6))) shouldBe Some(Some(Piece.BlackKing))
-    board.map(_.pieceAt(Square(File.E, Rank.R4))) shouldBe Some(Some(Piece.WhiteKing))
-
-  test("testRoundTripInitialPosition"):
-    val originalFen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR"
-    val board = FenParser.parseBoard(originalFen)
-    val exportedFen = board.map(FenExporter.boardToFen)
-
-    exportedFen shouldBe Some(originalFen)
-
-  test("testRoundTripEmptyBoard"):
-    val originalFen = "8/8/8/8/8/8/8/8"
-    val board = FenParser.parseBoard(originalFen)
-    val exportedFen = board.map(FenExporter.boardToFen)
-
-    exportedFen shouldBe Some(originalFen)
-
-  test("testRoundTripPartialPosition"):
-    val originalFen = "8/8/4k3/8/4K3/8/8/8"
-    val board = FenParser.parseBoard(originalFen)
-    val exportedFen = board.map(FenExporter.boardToFen)
-
-    exportedFen shouldBe Some(originalFen)
-
-  test("parse full FEN - initial position"):
-    val fen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"
-    val gameState = FenParser.parseFen(fen)
-
-    gameState.isDefined shouldBe true
-    gameState.get.activeColor shouldBe Color.White
-    gameState.get.castlingWhite.kingSide shouldBe true
-    gameState.get.castlingWhite.queenSide shouldBe true
-    gameState.get.castlingBlack.kingSide shouldBe true
-    gameState.get.castlingBlack.queenSide shouldBe true
-    gameState.get.enPassantTarget shouldBe None
-    gameState.get.halfMoveClock shouldBe 0
-    gameState.get.fullMoveNumber shouldBe 1
-
-  test("parse full FEN - after e4"):
-    val fen = "rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq e3 0 1"
-    val gameState = FenParser.parseFen(fen)
-
-    gameState.get.activeColor shouldBe Color.Black
-    gameState.get.enPassantTarget shouldBe Some(Square(File.E, Rank.R3))
-
-  test("parse full FEN - invalid parts count"):
-    val fen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq"
-    val gameState = FenParser.parseFen(fen)
-
-    gameState.isDefined shouldBe false
-
-  test("parse full FEN - invalid color"):
-    val fen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR x KQkq - 0 1"
-    val gameState = FenParser.parseFen(fen)
-
-    gameState.isDefined shouldBe false
-
-  test("parse full FEN - invalid castling"):
-    val fen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w XYZ - 0 1"
-    val gameState = FenParser.parseFen(fen)
-
-    gameState.isDefined shouldBe false
-
-  test("parseFen: castling '-' produces CastlingRights.None for both sides"):
-    val fen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w - - 0 1"
-    val gameState = FenParser.parseFen(fen)
-
-    gameState.isDefined shouldBe true
-    gameState.get.castlingWhite.kingSide shouldBe false
-    gameState.get.castlingWhite.queenSide shouldBe false
-    gameState.get.castlingBlack.kingSide shouldBe false
-    gameState.get.castlingBlack.queenSide shouldBe false
-
-  test("parseBoard: returns None when a rank has too many files (overflow beyond 8)"):
-    // "9" alone would advance fileIdx to 9, exceeding 8 → None
-    val fen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBN9"
-    val board = FenParser.parseBoard(fen)
-
-    board shouldBe empty
-
-  test("parseBoard: returns None when a rank fails to parse (invalid middle rank)"):
-    // Invalid character 'X' in rank 4 should cause failure
-    val fen = "rnbqkbnr/pppppppp/8/8/XXXXXXXX/8/PPPPPPPP/RNBQKBNR"
-    val board = FenParser.parseBoard(fen)
-
-    board shouldBe empty
-
-  test("parseBoard: returns None when a rank has 9 piece characters (fileIdx > 7)"):
-    // 9 pawns in one rank triggers fileIdx > 7 guard (line 78)
-    val fen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/PPPPPPPPP"
-    val board = FenParser.parseBoard(fen)
-
-    board shouldBe empty