feat: NCS-30 FEN Parser using ParserCombinators (#21 )

Summary - Added scala-parser-combinators_3:2.4.0 dependency to modules/io - Implemented FenParserCombinators as an alternative FEN parser using RegexParsers, with the same public API as the existing FenParser - Parsers are built bottom-up: piece characters → rank tokens → rank → board, composed with explicit field separators into a full FEN parser - Added FenParserCombinatorsTest mirroring the existing FenParserTest to prove behavioural equivalence Test plan - All existing tests pass — FenParser and all other modules untouched - FenParserCombinatorsTest covers all cases: valid FEN, invalid color, invalid castling, invalid board shapes, en passant, round-trip via FenExporter - 100% line/branch/method coverage on FenParserCombinators Co-authored-by: LQ63 <lkhermann@web.de> Reviewed-on: #21 Reviewed-by: Janis <janis-e@gmx.de> Co-authored-by: Leon Hermann <lq@blackhole.local> Co-committed-by: Leon Hermann <lq@blackhole.local>
refactor: NCS-24 update CLAUDE.md for improved structure and clarity (#20 )
2026-04-07 12:28:43 +02:00 · 2026-04-07 12:25:33 +02:00 · 2026-04-07 06:25:56 +00:00 · 2026-04-06 21:03:17 +02:00 · 2026-04-06 07:21:42 +00:00 · 2026-04-06 09:07:39 +02:00
175 changed files with 6109 additions and 2942 deletions
@@ -2,9 +2,10 @@
 name: scala-implementer
 description: "Implements Scala 3 + Quarkus REST services, domain logic, and persistence"
 tools: Read, Write, Edit, Bash, Glob
-model: sonnet
+model: inherit
 color: pink
 ---
+
 You do not have permissions to write tests, just source code.
 You are a Scala 3 expert specialising in Quarkus microservices.
 Always read the relevant /docs/api/ file before implementing.
@@ -2,9 +2,10 @@
 name: test-writer
 description: "Writes QuarkusTest unit and integration tests for a service. Invoke after scala-implementer has finished."
 tools: Read, Write, Edit, Bash, Glob, Grep, WebFetch, WebSearch, NotebookEdit
-model: sonnet
+model: haiku
 color: purple
 ---
+
 You do not have permissions to modify the source code, just write tests.
 You write tests for Scala 3 + Quarkus services.

@@ -19,5 +20,4 @@ When invoked BEFORE scala-implementer (no implementation exists yet):

 When invoked AFTER scala-implementer (implementation exists):
  Run python3 jacoco-reporter/jacoco_coverage_gaps.py modules/{service-name}/build/reports/jacoco/test/jacocoTestReport.xml --output agent
-  Use the jacoco-coverage-gaps skill — close coverage gaps revealed by the report.
  To regenerate the report run the tests first.
@@ -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)
@@ -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.
@@ -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`
@@ -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
@@ -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
@@ -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
  }
 }
@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="AndroidProjectSystem">
+    <option name="providerId" value="com.android.tools.idea.GradleProjectSystem" />
+  </component>
+</project>
@@ -12,6 +12,9 @@
            <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>
      </GradleProjectSettings>
@@ -1,4 +1,3 @@
-<?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
  <component name="ExternalStorageConfigurationManager" enabled="true" />
  <component name="FrameworkDetectionExcludesConfiguration">
@@ -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">
+    <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>
@@ -6,6 +6,16 @@
      <inspection_tool class="CommitNamingConvention" enabled="true" level="WARNING" enabled_by_default="true" />
    </profile>
  </component>
+  <component name="IssueNavigationConfiguration">
+    <option name="links">
+      <list>
+        <IssueNavigationLink>
+          <option name="issueRegexp" value="(?x)\b(CORE|NCWF|BAC|FRO|K8S|ORG|NCI|NCS)-\d+\b#YouTrack" />
+          <option name="linkRegexp" value="https://knockoutwhist.youtrack.cloud/issue/$0" />
+        </IssueNavigationLink>
+      </list>
+    </option>
+  </component>
  <component name="VcsDirectoryMappings">
    <mapping directory="" vcs="Git" />
  </component>
@@ -0,0 +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
+- Edit and resell the asset to others - - Credits required using This link: https://fatman200.itch.io/
@@ -1,58 +1,50 @@
-# 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.
+
+## 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.
@@ -1,5 +1,6 @@
 plugins {
    id("org.sonarqube") version "7.2.3.7755"
+    id("org.scoverage") version "8.1" apply false
 }

 group = "de.nowchess"
@@ -28,7 +29,11 @@ val versions = mapOf(
    "SCALA_LIBRARY"         to "2.13.18",
    "SCALATEST"             to "3.2.19",
    "SCALATEST_JUNIT"       to "0.1.11",
-    "SCOVERAGE"             to "2.1.1"
+    "SCOVERAGE"             to "2.1.1",
+    "SCALAFX"               to "21.0.0-R32",
+    "JAVAFX"                to "21.0.1",
+    "JUNIT_BOM"             to "5.13.4",
+    "SCALA_PARSER_COMBINATORS" to "2.4.0"
 )
 extra["VERSIONS"] = versions

@@ -0,0 +1,4 @@
+#! /usr/bin/env bash
+set -euo pipefail
+
+./gradlew clean
@@ -0,0 +1,4 @@
+#! /usr/bin/env bash
+set -euo pipefail
+
+./gradlew classes
@@ -0,0 +1,10 @@
+#! /usr/bin/env bash
+set -euo pipefail
+
+./gradlew test
+
+if [ "$#" -eq 0 ]; then
+  PYTHONUTF8=1 python3 jacoco-reporter/scoverage_coverage_gaps.py
+else
+  PYTHONUTF8=1 python3 jacoco-reporter/scoverage_coverage_gaps.py "modules/$1/build/reports/scoverageTest/scoverage.xml"
+fi
@@ -19,6 +19,9 @@ Usage:
    python scoverage_coverage_gaps.py <scoverage.xml> --output agent   (default)
    python scoverage_coverage_gaps.py <scoverage.xml> --package-filter de.nowchess.chess.controller
    python scoverage_coverage_gaps.py <scoverage.xml> --min-coverage 80
+    python scoverage_coverage_gaps.py                                 (default: scans ./modules)
+    python scoverage_coverage_gaps.py --modules-dir ./services
+    python scoverage_coverage_gaps.py <scoverage.xml>
 """

 import xml.etree.ElementTree as ET
@@ -26,7 +29,8 @@ import sys
 import argparse
 import json
 import re
-from pathlib import Path, PureWindowsPath
+import glob
+from pathlib import Path
 from dataclasses import dataclass, field
 from typing import Optional

@@ -112,7 +116,6 @@ class ClassGap:
    @property
    def uncovered_branch_lines(self) -> list[int]:
        """Lines that are branch points and have at least one uncovered branch statement."""
-        # Group branch statements by line; a line is "partial" if some covered, some not
        from collections import defaultdict
        by_line: dict[int, list[Statement]] = defaultdict(list)
        for s in self.statements:
@@ -120,10 +123,7 @@ class ClassGap:
                by_line[s.line].append(s)
        partial = []
        for line, stmts in by_line.items():
-            has_covered = any(s.is_covered for s in stmts)
-            has_uncovered = any(s.is_uncovered for s in stmts)
-            # Report line if any branch arm is uncovered
-            if has_uncovered:
+            if any(s.is_uncovered for s in stmts):
                partial.append(line)
        return sorted(partial)

@@ -169,20 +169,10 @@ class ClassGap:
 # ---------------------------------------------------------------------------

 def _normalise_source(raw: str) -> str:
-    """
-    Convert an absolute Windows or Unix source path from the XML into a
-    relative src/main/scala/… path for agent consumption.
-
-    Strategy:
-      1. Replace Windows backslashes.
-      2. Find the 'src/' anchor and take everything from there.
-      3. Fall back to the package-derived path if no anchor found.
-    """
    normalised = raw.replace("\\", "/")
    match = re.search(r"(src/(?:main|test)/scala/.+)", normalised)
    if match:
        return match.group(1)
-    # Fallback: just the filename portion
    return normalised.split("/")[-1]


@@ -190,11 +180,10 @@ def _normalise_source(raw: str) -> str:
 # Parser
 # ---------------------------------------------------------------------------

-def parse_scoverage_xml(xml_path: str) -> list[ClassGap]:
+def parse_scoverage_xml(xml_path: str) -> tuple[dict, list[ClassGap]]:
    tree = ET.parse(xml_path)
    root = tree.getroot()

-    # ── Authoritative project-level totals from <scoverage> root element ──────
    project_stats = {
        "total_statements":    int(root.get("statement-count", 0)),
        "covered_statements":  int(root.get("statements-invoked", 0)),
@@ -202,17 +191,16 @@ def parse_scoverage_xml(xml_path: str) -> list[ClassGap]:
        "branch_coverage_pct": float(root.get("branch-rate", 0.0)),
    }
    project_stats["missed_statements"] = (
-        project_stats["total_statements"] - project_stats["covered_statements"]
+            project_stats["total_statements"] - project_stats["covered_statements"]
    )

-    class_map: dict[str, ClassGap] = {}   # full-class-name → ClassGap
+    class_map: dict[str, ClassGap] = {}

    for package in root.findall("packages/package"):
        for cls_elem in package.findall("classes/class"):
            class_name = cls_elem.get("name", "")
            filename   = cls_elem.get("filename", "")

-            # Authoritative per-class totals from <class> attributes
            cls_total     = int(cls_elem.get("statement-count", 0))
            cls_invoked   = int(cls_elem.get("statements-invoked", 0))
            cls_stmt_rate = float(cls_elem.get("statement-rate", 0.0))
@@ -221,11 +209,8 @@ def parse_scoverage_xml(xml_path: str) -> list[ClassGap]:
            for method_elem in cls_elem.findall("methods/method"):
                method_name = method_elem.get("name", "")

-                # Authoritative per-method totals from <method> attributes
-                m_total     = int(method_elem.get("statement-count", 0))
-                m_invoked   = int(method_elem.get("statements-invoked", 0))
-                m_stmt_rate = float(method_elem.get("statement-rate", 0.0))
-                m_br_rate   = float(method_elem.get("branch-rate", 0.0))
+                m_total   = int(method_elem.get("statement-count", 0))
+                m_invoked = int(method_elem.get("statements-invoked", 0))

                for stmt_elem in method_elem.findall("statements/statement"):
                    raw_source = stmt_elem.get("source", filename)
@@ -257,7 +242,6 @@ def parse_scoverage_xml(xml_path: str) -> list[ClassGap]:
                        method=method_name,
                    ))

-                # Register method-level gap using authoritative XML stats
                cg = next(
                    (v for v in class_map.values() if v.class_name == class_name),
                    None,
@@ -268,7 +252,6 @@ def parse_scoverage_xml(xml_path: str) -> list[ClassGap]:
                uncov_lines        = sorted({s.line for s in active if s.is_uncovered})
                uncov_branch_lines = sorted({s.line for s in active if s.is_branch and s.is_uncovered})
                if uncov_lines or uncov_branch_lines:
-                    # Count branches from statement-level data (not in method XML attrs)
                    total_b = sum(1 for s in active if s.is_branch)
                    cov_b   = sum(1 for s in active if s.is_branch and s.is_covered)
                    mg = MethodGap(
@@ -282,7 +265,6 @@ def parse_scoverage_xml(xml_path: str) -> list[ClassGap]:
                    )
                    cg.method_gaps.append(mg)

-    # ── Project stats injected so formatters never recount from statements ────
    return project_stats, [cg for cg in class_map.values() if cg.has_gaps]


@@ -310,103 +292,60 @@ def _compact_ranges(numbers: list[int]) -> str:
 # Formatters
 # ---------------------------------------------------------------------------

-def _pct_bar(pct: float, width: int = 20) -> str:
-    """Render a compact ASCII progress bar, e.g. [████░░░░░░░░░░░░░░░░] 23.5%"""
-    filled = round(pct / 100 * width)
-    bar = "█" * filled + "░" * (width - filled)
-    return f"[{bar}] {pct:.1f}%"
-
-
 def format_agent(project_stats: dict, classes: list[ClassGap]) -> str:
+    """
+    Compact agent format — optimised for low token count.
+    Emits only actionable gaps: file path, uncovered lines, branch-gap lines,
+    and a per-method breakdown. No ASCII bars, no redundant tables.
+    """
    lines: list[str] = []
-    lines.append("# scoverage Coverage Gaps — Agent Action Report")
-    lines.append("")

-    # ---- Project-level totals (authoritative from <scoverage> root element) ----
-    total_stmts      = project_stats["total_statements"]
-    covered_stmts    = project_stats["covered_statements"]
-    missed_stmts     = project_stats["missed_statements"]
+    total_stmts        = project_stats["total_statements"]
+    covered_stmts      = project_stats["covered_statements"]
+    missed_stmts       = project_stats["missed_statements"]
    overall_stmt_pct   = project_stats["stmt_coverage_pct"]
    overall_branch_pct = project_stats["branch_coverage_pct"]
-    total_branch_lines = sum(len(c.uncovered_branch_lines) for c in classes)
-    # Branch totals: count from statement data (scoverage root has no branch count attr)
-    total_branches   = sum(c.total_branches for c in classes)
-    covered_branches = sum(c.covered_branches for c in classes)
-    missed_branches  = sum(c.missed_branches for c in classes)
+    total_branches     = sum(c.total_branches for c in classes)
+    covered_branches   = sum(c.covered_branches for c in classes)
+    missed_branches    = total_branches - covered_branches

-    lines.append("## Project Coverage Summary")
-    lines.append("")
-    lines.append(f"| Metric            | Covered | Total | Missed | Coverage |")
-    lines.append(f"|-------------------|---------|-------|--------|----------|")
-    lines.append(f"| Statements        | {covered_stmts:>7} | {total_stmts:>5} | {missed_stmts:>6} | {_pct_bar(overall_stmt_pct)} |")
-    lines.append(f"| Branch paths      | {covered_branches:>7} | {total_branches:>5} | {missed_branches:>6} | {_pct_bar(overall_branch_pct)} |")
-    lines.append(f"| Files with gaps   | {'—':>7} | {len(classes):>5} | {'—':>6} | {'—'} |")
-    lines.append(f"| Lines w/ br. gaps | {'—':>7} | {total_branch_lines:>5} | {'—':>6} | {'—'} |")
-    lines.append("")
-    lines.append("---")
-    lines.append("")
-    lines.append("## Files Requiring Tests")
-    lines.append("")
-    lines.append("> Each entry lists the SOURCE FILE PATH, uncovered LINE NUMBERS,")
-    lines.append("> and the METHODS that contain those gaps.")
-    lines.append("> Write or extend unit/integration tests to exercise these paths.")
+    lines.append("# scoverage Coverage Gaps")
+    lines.append(
+        f"stmt: {overall_stmt_pct:.1f}% ({missed_stmts}/{total_stmts} missed) | "
+        f"branches: {overall_branch_pct:.1f}% ({missed_branches}/{total_branches} missed) | "
+        f"files with gaps: {len(classes)}"
+    )
    lines.append("")

    sorted_classes = sorted(classes, key=lambda c: -(c.missed_statements + c.missed_branches))

    for cls in sorted_classes:
-        lines.append(f"### `{cls.source_path}`")
-        lines.append(f"**Class**: `{cls.class_name}`")
-        lines.append("")
-        lines.append(f"| Metric       | Covered | Total | Missed | Coverage |")
-        lines.append(f"|--------------|---------|-------|--------|----------|")
-        lines.append(f"| Statements   | {cls.covered_statements:>7} | {cls.total_statements:>5} | {cls.missed_statements:>6} | {_pct_bar(cls.stmt_coverage_pct)} |")
-        if cls.total_branches:
-            lines.append(f"| Branch paths | {cls.covered_branches:>7} | {cls.total_branches:>5} | {cls.missed_branches:>6} | {_pct_bar(cls.branch_coverage_pct)} |")
-        lines.append("")
-
-        uncov = cls.all_uncovered_lines
-        if uncov:
-            lines.append("#### ❌ Uncovered Statements")
-            lines.append(f"Lines never executed: `{_compact_ranges(uncov)}`")
-            lines.append("")
-
+        uncov        = cls.all_uncovered_lines
        branch_lines = cls.uncovered_branch_lines
-        if branch_lines:
-            lines.append("#### ⚠️  Missing Branch Coverage (Conditional Paths)")
-            lines.append(f"Lines where not all conditional paths are taken: `{_compact_ranges(branch_lines)}`")
-            lines.append("")
+
+        lines.append(f"## {cls.source_path}")
+        lines.append(
+            f"stmt: {cls.stmt_coverage_pct:.1f}% ({cls.missed_statements} missed)"
+            + (f" | branches: {cls.branch_coverage_pct:.1f}% ({cls.missed_branches} missed)"
+               if cls.total_branches else "")
+        )
+        if uncov:
+            lines.append(f"uncovered lines: {_compact_ranges(uncov)}")
+        only_branch = [l for l in branch_lines if l not in cls.all_uncovered_lines]
+        if only_branch:
+            lines.append(f"partial branches: {_compact_ranges(only_branch)}")

        if cls.method_gaps:
-            lines.append("#### Methods with Gaps")
-            lines.append("")
-            lines.append("| Method | Stmt Coverage | Branch Coverage | Uncovered Lines | Branch Gap Lines |")
-            lines.append("|--------|--------------|-----------------|-----------------|------------------|")
+            lines.append("methods:")
            for mg in cls.method_gaps:
-                stmt_cell   = f"{_pct_bar(mg.stmt_coverage_pct, 10)} ({mg.total_statements - mg.covered_statements}/{mg.total_statements} missed)"
-                branch_cell = f"{_pct_bar(mg.branch_coverage_pct, 10)} ({mg.missed_branches}/{mg.total_branches} missed)" if mg.total_branches else "n/a"
-                uncov_cell  = f"`{_compact_ranges(mg.uncovered_lines)}`"        if mg.uncovered_lines        else "—"
-                br_cell     = f"`{_compact_ranges(mg.uncovered_branch_lines)}`" if mg.uncovered_branch_lines else "—"
-                lines.append(f"| `{mg.short_name}` | {stmt_cell} | {branch_cell} | {uncov_cell} | {br_cell} |")
-            lines.append("")
+                parts = [f"  {mg.short_name}"]
+                if mg.uncovered_lines:
+                    parts.append(f"lines={_compact_ranges(mg.uncovered_lines)}")
+                if mg.uncovered_branch_lines:
+                    parts.append(f"branches={_compact_ranges(mg.uncovered_branch_lines)}")
+                lines.append(" ".join(parts))

-        lines.append("**Action**: Add tests that exercise the lines/branches listed above.")
        lines.append("")
-        lines.append("---")
-        lines.append("")
-
-    lines.append("## Quick Reference: All Uncovered Locations")
-    lines.append("")
-    lines.append("Copy-paste friendly list for IDE navigation or grep:")
-    lines.append("")
-    lines.append("```")
-    for cls in sorted_classes:
-        for ln in cls.all_uncovered_lines:
-            lines.append(f"{cls.source_path}:{ln}  # uncovered statement")
-        for ln in cls.uncovered_branch_lines:
-            if ln not in cls.all_uncovered_lines:
-                lines.append(f"{cls.source_path}:{ln}  # partial branch")
-    lines.append("```")

    return "\n".join(lines)

@@ -511,6 +450,87 @@ def format_markdown(project_stats: dict, classes: list[ClassGap]) -> str:
    return "\n".join(lines)


+# ---------------------------------------------------------------------------
+# Scan-modules mode
+# ---------------------------------------------------------------------------
+
+# Candidate sub-paths within a module directory where scoverage.xml may live.
+_SCOVERAGE_SUBPATHS = [
+    # Gradle / default layout
+    "build/reports/scoverageTest/scoverage.xml",
+    # sbt default (scala version wildcard resolved via glob)
+    "target/scala-*/scoverage-report/scoverage.xml",
+    # Maven / flat layout
+    "target/scoverage-report/scoverage.xml",
+    # Already at root of module
+    "scoverage.xml",
+]
+
+
+def _find_scoverage_xml(module_dir: Path) -> Optional[Path]:
+    """Return the first scoverage.xml found inside *module_dir*, or None."""
+    for pattern in _SCOVERAGE_SUBPATHS:
+        hits = sorted(module_dir.glob(pattern))
+        if hits:
+            return hits[0]
+    return None
+
+
+def format_module_gaps(module_name: str, classes: list[ClassGap], stmt_pct: float) -> str:
+    """
+    One summary line per module. If coverage is not 100%, append an agent hint.
+    """
+    if not classes:
+        return f"[{module_name}] stmt: {stmt_pct:.1f}% ✅"
+
+    line = f"[{module_name}] stmt: {stmt_pct:.1f}%  files_with_gaps: {len(classes)}"
+    if stmt_pct < 100.0:
+        line += f"  # hint: run ./coverage {module_name} for details"
+    return line
+
+
+def run_scan_modules(modules_dir: str, package_filter: Optional[str], min_coverage: float) -> None:
+    base = Path(modules_dir)
+    if not base.is_dir():
+        print(f"ERROR: modules directory not found: {base}", file=sys.stderr)
+        sys.exit(1)
+
+    module_dirs = sorted(p for p in base.iterdir() if p.is_dir())
+    if not module_dirs:
+        print(f"No sub-directories found in {base}", file=sys.stderr)
+        sys.exit(1)
+
+    results: list[str] = []
+    missing: list[str] = []
+
+    for mod_dir in module_dirs:
+        if mod_dir.name.startswith("build"):
+            continue
+        xml_path = _find_scoverage_xml(mod_dir)
+        if xml_path is None:
+            missing.append(mod_dir.name)
+            continue
+
+        project_stats, classes = parse_scoverage_xml(str(xml_path))
+
+        if package_filter:
+            classes = [c for c in classes if c.class_name.startswith(package_filter)]
+        if min_coverage > 0:
+            classes = [c for c in classes if c.stmt_coverage_pct < min_coverage]
+
+        results.append(
+            format_module_gaps(mod_dir.name, classes, project_stats["stmt_coverage_pct"])
+        )
+
+    print("\n".join(results))
+
+    if missing:
+        print(
+            f"\n# Modules without scoverage.xml: {', '.join(missing)}",
+            file=sys.stderr,
+        )
+
+
 # ---------------------------------------------------------------------------
 # Entry point
 # ---------------------------------------------------------------------------
@@ -519,7 +539,13 @@ def main() -> None:
    parser = argparse.ArgumentParser(
        description="Report missing statement & branch coverage from a scoverage XML report."
    )
-    parser.add_argument("xml_file", help="Path to scoverage.xml report file")
+
+    # Positional xml_file is optional when --scan-modules is used
+    parser.add_argument(
+        "xml_file",
+        nargs="?",
+        help="Path to scoverage.xml report file (not required with --scan-modules)",
+    )
    parser.add_argument(
        "--output", "-o",
        choices=["agent", "json", "markdown"],
@@ -537,8 +563,30 @@ def main() -> None:
        default=None,
        help="Only report classes in this package prefix (e.g. de.nowchess.chess.controller)",
    )
+    # ── Scan-modules mode ──────────────────────────────────────────────────
+    parser.add_argument(
+        "--scan-modules",
+        action="store_true",
+        help=(
+            "Scan every sub-directory of --modules-dir for a scoverage.xml "
+            "and print a compact coverage-gaps summary per module."
+        ),
+    )
+    parser.add_argument(
+        "--modules-dir",
+        default="./modules",
+        help="Root directory that contains one sub-directory per module (default: ./modules)",
+    )
+
    args = parser.parse_args()

+    # ── Scan-modules path (explicit flag, or default when no xml_file given) ──
+    if args.scan_modules or not args.xml_file:
+        run_scan_modules(args.modules_dir, args.package_filter, args.min_coverage)
+        return
+
+    # ── Single-file path ──────────────────────────────────────────────────
+
    xml_path = Path(args.xml_file)
    if not xml_path.exists():
        print(f"ERROR: File not found: {xml_path}", file=sys.stderr)
@@ -565,4 +613,4 @@ def main() -> None:


 if __name__ == "__main__":
-    main()
+    main()
@@ -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)
@@ -0,0 +1,288 @@
+#!/usr/bin/env python3
+"""
+Test Gap Reporter
+Scans JUnit XML test results under modules/*/build/test-results/*.xml and
+outputs a minimal summary optimised for agent consumption.
+
+Usage:
+    python test_gaps.py                        # scan all modules (default)
+    python test_gaps.py --module chess         # single module
+    python test_gaps.py --module all           # explicit all
+    python test_gaps.py --modules-dir ./modules
+    python test_gaps.py --results-subdir build/test-results
+"""
+
+import xml.etree.ElementTree as ET
+import sys
+import argparse
+from pathlib import Path
+from dataclasses import dataclass, field
+from typing import Optional
+
+
+# ---------------------------------------------------------------------------
+# Data classes
+# ---------------------------------------------------------------------------
+
+@dataclass
+class TestCase:
+    classname: str
+    name: str
+    time: float
+    failure: Optional[str] = None   # message if failed
+    error: Optional[str]   = None   # message if errored
+    skipped: bool          = False
+
+    @property
+    def short_class(self) -> str:
+        return self.classname.split(".")[-1]
+
+    @property
+    def status(self) -> str:
+        if self.failure is not None:
+            return "FAIL"
+        if self.error is not None:
+            return "ERROR"
+        if self.skipped:
+            return "SKIP"
+        return "OK"
+
+
+@dataclass
+class SuiteResult:
+    name: str
+    total: int
+    failures: int
+    errors: int
+    skipped: int
+    time: float
+    cases: list[TestCase] = field(default_factory=list)
+
+    @property
+    def passed(self) -> int:
+        return self.total - self.failures - self.errors - self.skipped
+
+    @property
+    def is_clean(self) -> bool:
+        return self.failures == 0 and self.errors == 0
+
+    @property
+    def bad_cases(self) -> list[TestCase]:
+        return [c for c in self.cases if c.status in ("FAIL", "ERROR")]
+
+    @property
+    def skipped_cases(self) -> list[TestCase]:
+        return [c for c in self.cases if c.skipped]
+
+
+@dataclass
+class ModuleResult:
+    name: str
+    suites: list[SuiteResult] = field(default_factory=list)
+
+    @property
+    def total(self)    -> int: return sum(s.total    for s in self.suites)
+    @property
+    def failures(self) -> int: return sum(s.failures for s in self.suites)
+    @property
+    def errors(self)   -> int: return sum(s.errors   for s in self.suites)
+    @property
+    def skipped(self)  -> int: return sum(s.skipped  for s in self.suites)
+    @property
+    def passed(self)   -> int: return sum(s.passed   for s in self.suites)
+    @property
+    def is_clean(self) -> bool: return self.failures == 0 and self.errors == 0
+
+    @property
+    def bad_cases(self) -> list[TestCase]:
+        return [c for s in self.suites for c in s.bad_cases]
+
+    @property
+    def skipped_cases(self) -> list[TestCase]:
+        return [c for s in self.suites for c in s.skipped_cases]
+
+
+# ---------------------------------------------------------------------------
+# Parser
+# ---------------------------------------------------------------------------
+
+def parse_suite_xml(xml_path: Path) -> SuiteResult:
+    tree = ET.parse(xml_path)
+    root = tree.getroot()
+
+    # Handle both <testsuite> root and <testsuites> wrapper
+    suites = [root] if root.tag == "testsuite" else root.findall("testsuite")
+
+    # Merge multiple suites from one file into a single SuiteResult
+    total = failures = errors = skipped = 0
+    elapsed = 0.0
+    name = xml_path.stem
+    cases: list[TestCase] = []
+
+    for suite in suites:
+        total    += int(suite.get("tests",    0))
+        failures += int(suite.get("failures", 0))
+        errors   += int(suite.get("errors",   0))
+        skipped  += int(suite.get("skipped",  0))
+        elapsed  += float(suite.get("time",   0.0))
+        if suite.get("name"):
+            name = suite.get("name")
+
+        for tc in suite.findall("testcase"):
+            fail_el = tc.find("failure")
+            err_el  = tc.find("error")
+            skip_el = tc.find("skipped")
+            cases.append(TestCase(
+                classname=tc.get("classname", ""),
+                name=tc.get("name", ""),
+                time=float(tc.get("time", 0.0)),
+                failure=fail_el.get("message", fail_el.text or "") if fail_el is not None else None,
+                error=err_el.get("message",  err_el.text  or "") if err_el  is not None else None,
+                skipped=skip_el is not None,
+            ))
+
+    return SuiteResult(
+        name=name, total=total, failures=failures,
+        errors=errors, skipped=skipped, time=elapsed, cases=cases,
+    )
+
+
+def load_module(module_dir: Path, results_subdir: str) -> Optional[ModuleResult]:
+    results_dir = module_dir / results_subdir
+    if not results_dir.is_dir():
+        return None
+
+    xml_files = sorted(results_dir.glob("*.xml"))
+    if not xml_files:
+        return None
+
+    mod = ModuleResult(name=module_dir.name)
+    for xml_path in xml_files:
+        try:
+            mod.suites.append(parse_suite_xml(xml_path))
+        except ET.ParseError:
+            pass  # skip malformed files silently
+    return mod if mod.suites else None
+
+
+# ---------------------------------------------------------------------------
+# Formatter
+# ---------------------------------------------------------------------------
+
+def _truncate(text: str, max_len: int = 120) -> str:
+    text = " ".join(text.split())        # collapse whitespace
+    return text[:max_len] + "…" if len(text) > max_len else text
+
+
+def format_module(mod: ModuleResult) -> str:
+    parts = [f"[{mod.name}]"]
+
+    if mod.is_clean and mod.skipped == 0:
+        parts.append(f"tests: {mod.total} ✅")
+        return " ".join(parts)
+
+    parts.append(f"tests: {mod.total}")
+    if mod.failures:  parts.append(f"failed: {mod.failures}")
+    if mod.errors:    parts.append(f"errors: {mod.errors}")
+    if mod.skipped:   parts.append(f"skipped: {mod.skipped}")
+
+    # Agent hint only when there are actual failures/errors
+    if not mod.is_clean:
+        parts.append(f" # hint: run ./test {mod.name} for details")
+
+    lines = [" ".join(parts)]
+
+    # List each failed/errored test — this IS the actionable info
+    for tc in mod.bad_cases:
+        msg = tc.failure if tc.failure is not None else tc.error
+        label = f"  {tc.status}: {tc.short_class} > {tc.name}"
+        if msg:
+            label += f"  [{_truncate(msg, 80)}]"
+        lines.append(label)
+
+    # Skipped: compact, one line total
+    if mod.skipped_cases:
+        skipped_names = ", ".join(
+            f"{c.short_class}.{c.name}" for c in mod.skipped_cases[:5]
+        )
+        if len(mod.skipped_cases) > 5:
+            skipped_names += f" (+{len(mod.skipped_cases) - 5} more)"
+        lines.append(f"  SKIP: {skipped_names}")
+
+    return "\n".join(lines)
+
+
+# ---------------------------------------------------------------------------
+# Runner
+# ---------------------------------------------------------------------------
+
+def run(modules_dir: str, results_subdir: str, module_filter: Optional[str]) -> None:
+    base = Path(modules_dir)
+    if not base.is_dir():
+        print(f"ERROR: modules directory not found: {base}", file=sys.stderr)
+        sys.exit(1)
+
+    # Resolve which module dirs to scan
+    if module_filter and module_filter != "all":
+        mod_dir = base / module_filter
+        if not mod_dir.is_dir():
+            print(f"ERROR: module not found: {mod_dir}", file=sys.stderr)
+            sys.exit(1)
+        candidates = [mod_dir]
+    else:
+        candidates = sorted(p for p in base.iterdir() if p.is_dir())
+
+    results: list[str] = []
+    missing: list[str] = []
+
+    for mod_dir in candidates:
+        if mod_dir.name.startswith("build"):
+            continue
+        mod = load_module(mod_dir, results_subdir)
+        if mod is None:
+            missing.append(mod_dir.name)
+            continue
+        results.append(format_module(mod))
+
+    print("\n".join(results))
+
+    if missing:
+        print(
+            f"\n# Modules without test results: {', '.join(missing)}",
+            file=sys.stderr,
+        )
+
+
+# ---------------------------------------------------------------------------
+# Entry point
+# ---------------------------------------------------------------------------
+
+def main() -> None:
+    parser = argparse.ArgumentParser(
+        description="Minimal test-gap reporter for JUnit XML results across modules."
+    )
+    parser.add_argument(
+        "--module", "-m",
+        nargs="?",
+        const="all",
+        default="all",
+        help="Module name to scan, or 'all' (default: all)",
+    )
+    parser.add_argument(
+        "--modules-dir",
+        default="./modules",
+        help="Root directory containing one sub-directory per module (default: ./modules)",
+    )
+    parser.add_argument(
+        "--results-subdir",
+        default="build/test-results/test",
+        help="Sub-path inside each module dir where *.xml files live (default: build/test-results/test)",
+    )
+    args = parser.parse_args()
+
+    filter_ = None if args.module == "all" else args.module
+    run(args.modules_dir, args.results_subdir, filter_)
+
+
+if __name__ == "__main__":
+    main()
@@ -1,3 +1,23 @@
 ##  (2026-03-27)
 ##  (2026-03-28)
 ##  (2026-03-28)
+##  (2026-03-29)
+##  (2026-03-31)
+##  (2026-04-01)
+##  (2026-04-01)
+##  (2026-04-01)
+##  (2026-04-02)
+
+### 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))
@@ -59,7 +59,7 @@ tasks.test {
    useJUnitPlatform {
        includeEngines("scalatest")
        testLogging {
-            events("passed", "skipped", "failed")
+            events("skipped", "failed")
        }
    }
    finalizedBy(tasks.reportScoverage)
@@ -14,6 +14,9 @@ object Board:
      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 =
@@ -0,0 +1,70 @@
+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
@@ -39,3 +39,19 @@ object Square:
          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
@@ -0,0 +1,44 @@
+package de.nowchess.api.game
+
+import de.nowchess.api.board.{Board, Color, Square, CastlingRights}
+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]
+):
+  /** 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)
+
+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
+  )
@@ -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
-  )
@@ -9,7 +9,7 @@ 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). */
@@ -29,5 +29,5 @@ enum MoveType:
 final case class Move(
  from: Square,
  to: Square,
-  moveType: MoveType = MoveType.Normal
+  moveType: MoveType = MoveType.Normal()
 )
@@ -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
  }

@@ -34,38 +31,20 @@ class BoardTest extends AnyFunSuite with Matchers:
    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)
    }
  }
@@ -101,17 +80,14 @@ class BoardTest extends AnyFunSuite with Matchers:
      Board.initial.pieceAt(Square(file, rank)) shouldBe None
  }

-  test("updated adds or replaces piece at square") {
+  test("updated adds and replaces piece at squares") {
    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)
-  }
+    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") {
@@ -120,3 +96,13 @@ class BoardTest extends AnyFunSuite with Matchers:
    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
+  }
+
@@ -0,0 +1,57 @@
+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
+
@@ -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
+    }
@@ -11,50 +11,23 @@ class PieceTest extends AnyFunSuite with Matchers:
    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
+    }
  }
@@ -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
+    }
@@ -5,58 +5,33 @@ 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("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
  }

-  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
-  }
@@ -0,0 +1,60 @@
+package de.nowchess.api.game
+
+import de.nowchess.api.board.{Board, CastlingRights, Color, File, Rank, Square}
+import de.nowchess.api.move.Move
+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
+
+  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)
+
@@ -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
-  }
@@ -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
+    }
  }
@@ -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")
+    val playerId = PlayerId("p1")
+    val info = PlayerInfo(playerId, "Magnus")
    info.id.value      shouldBe "p1"
    info.displayName   shouldBe "Magnus"
  }
@@ -5,52 +5,26 @@ 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.message shouldBe "message"
    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
  }

@@ -1,3 +1,3 @@
 MAJOR=0
-MINOR=0
-PATCH=3
+MINOR=3
+PATCH=0
@@ -28,3 +28,186 @@
 * 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))
+##  (2026-03-29)
+
+### 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-6 Implementing FEN & PGN ([#7](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/7)) ([f28e69d](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/f28e69dc181416aa2f221fdc4b45c2cda5efbf07))
+* 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))
+##  (2026-03-29)
+
+### 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-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))
+##  (2026-03-31)
+
+### 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-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-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))
+##  (2026-04-01)
+
+### 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-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-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))
+##  (2026-04-01)
+
+### 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-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))
+##  (2026-04-01)
+
+### 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-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))
+##  (2026-04-02)
+
+### 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))
+##  (2026-04-03)
+
+### 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))
@@ -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")
@@ -62,7 +54,7 @@ tasks.test {
    useJUnitPlatform {
        includeEngines("scalatest")
        testLogging {
-            events("passed", "skipped", "failed")
+            events("skipped", "failed")
        }
    }
    finalizedBy(tasks.reportScoverage)
@@ -1,12 +0,0 @@
-package de.nowchess.chess
-
-import de.nowchess.api.board.Board
-import de.nowchess.api.board.Color
-import de.nowchess.chess.controller.GameController
-import de.nowchess.chess.logic.GameHistory
-
-object Main {
-  def main(args: Array[String]): Unit =
-    println("NowChess TUI — type moves in coordinate notation (e.g. e2e4). Type 'quit' to exit.")
-    GameController.gameLoop(Board.initial, GameHistory.empty, Color.White)
-}
@@ -0,0 +1,61 @@
+package de.nowchess.chess.command
+
+import de.nowchess.api.board.{Square, Piece}
+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.
+ */
+trait Command:
+  /** Execute the command and return true if successful, false otherwise. */
+  def execute(): Boolean
+
+  /** Undo the command and return true if successful, false otherwise. */
+  def undo(): Boolean
+
+  /** 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.
+ */
+case class MoveCommand(
+  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 =
+    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(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 description: String = "Quit game"
+
+/** Command to reset the board to initial position. */
+case class ResetCommand(
+  previousContext: Option[GameContext] = None
+) extends Command:
+
+  override def execute(): Boolean = true
+
+  override def undo(): Boolean =
+    previousContext.isDefined
+
+  override def description: String = "Reset board"
@@ -0,0 +1,73 @@
+package de.nowchess.chess.command
+
+/** Manages command execution and history for undo/redo support. */
+class CommandInvoker:
+  private val executedCommands = scala.collection.mutable.ListBuffer[Command]()
+  private var currentIndex = -1
+
+  /** 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)
+      executedCommands += command
+      currentIndex += 1
+      true
+    else
+      false
+  }
+
+  /** Undo the last executed command if possible. */
+  def undo(): Boolean = synchronized {
+    if currentIndex >= 0 && currentIndex < executedCommands.size then
+      val command = executedCommands(currentIndex)
+      if command.undo() then
+        currentIndex -= 1
+        true
+      else
+        false
+    else
+      false
+  }
+
+  /** Redo the next command in history if available. */
+  def redo(): Boolean = synchronized {
+    if currentIndex + 1 < executedCommands.size then
+      val command = executedCommands(currentIndex + 1)
+      if command.execute() then
+        currentIndex += 1
+        true
+      else
+        false
+    else
+      false
+  }
+
+  /** Get the history of all executed commands. */
+  def history: List[Command] = synchronized {
+    executedCommands.toList
+  }
+
+  /** Get the current position in command history. */
+  def getCurrentIndex: Int = synchronized {
+    currentIndex
+  }
+
+  /** Clear all command history. */
+  def clear(): Unit = synchronized {
+    executedCommands.clear()
+    currentIndex = -1
+  }
+
+  /** Check if undo is available. */
+  def canUndo: Boolean = synchronized {
+    currentIndex >= 0
+  }
+
+  /** Check if redo is available. */
+  def canRedo: Boolean = synchronized {
+    currentIndex + 1 < executedCommands.size
+  }
@@ -1,105 +0,0 @@
-package de.nowchess.chess.controller
-
-import scala.io.StdIn
-import de.nowchess.api.board.{Board, Color, File, Piece, Rank, Square}
-import de.nowchess.chess.logic.*
-import de.nowchess.chess.view.Renderer
-
-// ---------------------------------------------------------------------------
-// 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  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)) =>
-            board.pieceAt(from) match
-              case None =>
-                MoveResult.NoPiece
-              case Some(piece) if piece.color != turn =>
-                MoveResult.WrongColor
-              case Some(_) =>
-                if !MoveValidator.isLegal(board, history, from, to) then
-                  MoveResult.IllegalMove
-                else
-                  val castleOpt = if MoveValidator.isCastle(board, from, to)
-                                  then Some(MoveValidator.castleSide(from, to))
-                                  else None
-                  val (newBoard, captured) = castleOpt match
-                    case Some(side) => (board.withCastle(turn, side), None)
-                    case None       => board.withMove(from, to)
-                  val newHistory = history.addMove(from, to, castleOpt)
-                  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
-
-  /** Thin I/O shell: renders the board, reads a line, delegates to processMove,
-   *  prints the outcome, and recurses until the game ends.
-   */
-  def gameLoop(board: Board, history: GameHistory, turn: Color): Unit =
-    println()
-    print(Renderer.render(board))
-    println(s"${turn.label}'s turn. Enter move: ")
-    val input = Option(StdIn.readLine()).getOrElse("quit").trim
-    processMove(board, history, turn, input) match
-      case MoveResult.Quit =>
-        println("Game over. Goodbye!")
-      case MoveResult.InvalidFormat(raw) =>
-        println(s"Invalid move format '$raw'. Use coordinate notation, e.g. e2e4.")
-        gameLoop(board, history, turn)
-      case MoveResult.NoPiece =>
-        println(s"No piece on ${Parser.parseMove(input).map(_._1).fold("?")(_.toString)}.")
-        gameLoop(board, history, turn)
-      case MoveResult.WrongColor =>
-        println(s"That is not your piece.")
-        gameLoop(board, history, turn)
-      case MoveResult.IllegalMove =>
-        println(s"Illegal move.")
-        gameLoop(board, history, turn)
-      case MoveResult.Moved(newBoard, newHistory, captured, newTurn) =>
-        val prevTurn = newTurn.opposite
-        captured.foreach: cap =>
-          val toSq = Parser.parseMove(input).map(_._2).fold("?")(_.toString)
-          println(s"${prevTurn.label} captures ${cap.color.label} ${cap.pieceType.label} on $toSq")
-        gameLoop(newBoard, newHistory, newTurn)
-      case MoveResult.MovedInCheck(newBoard, newHistory, captured, newTurn) =>
-        val prevTurn = newTurn.opposite
-        captured.foreach: cap =>
-          val toSq = Parser.parseMove(input).map(_._2).fold("?")(_.toString)
-          println(s"${prevTurn.label} captures ${cap.color.label} ${cap.pieceType.label} on $toSq")
-        println(s"${newTurn.label} is in check!")
-        gameLoop(newBoard, newHistory, newTurn)
-      case MoveResult.Checkmate(winner) =>
-        println(s"Checkmate! ${winner.label} wins.")
-        gameLoop(Board.initial, GameHistory.empty, Color.White)
-      case MoveResult.Stalemate =>
-        println("Stalemate! The game is a draw.")
-        gameLoop(Board.initial, GameHistory.empty, Color.White)
@@ -0,0 +1,318 @@
+package de.nowchess.chess.engine
+
+import de.nowchess.api.board.{Board, Color, Piece, PieceType, Square}
+import de.nowchess.api.move.{Move, MoveType, PromotionPiece}
+import de.nowchess.api.game.GameContext
+import de.nowchess.chess.controller.Parser
+import de.nowchess.chess.observer.*
+import de.nowchess.chess.command.{CommandInvoker, MoveCommand, MoveResult}
+import de.nowchess.io.{GameContextImport, GameContextExport}
+import de.nowchess.rules.RuleSet
+import de.nowchess.rules.sets.DefaultRules
+
+/** 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(
+  val initialContext: GameContext = GameContext.initial,
+  val ruleSet: RuleSet = DefaultRules
+) extends Observable:
+  private var currentContext: GameContext = initialContext
+  private val invoker = new CommandInvoker()
+
+  /** Pending promotion: the Move that triggered it (from/to only, moveType filled in later). */
+  private case class PendingPromotion(from: Square, to: Square, contextBefore: GameContext)
+  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 }
+
+  // Synchronized accessors for current state
+  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 }
+
+  /** Check if redo is available. */
+  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 }
+
+  /** 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" =>
+        ()
+
+      case "undo" =>
+        performUndo()
+
+      case "redo" =>
+        performRedo()
+
+      case "draw" =>
+        if currentContext.halfMoveClock >= 100 then
+          invoker.clear()
+          notifyObservers(DrawClaimedEvent(currentContext))
+        else
+          notifyObservers(InvalidMoveEvent(
+            currentContext,
+            "Draw cannot be claimed: the 50-move rule has not been triggered."
+          ))
+
+      case "" =>
+        notifyObservers(InvalidMoveEvent(currentContext, "Please enter a valid move or command."))
+
+      case moveInput =>
+        Parser.parseMove(moveInput) match
+          case None =>
+            notifyObservers(InvalidMoveEvent(
+              currentContext,
+              s"Invalid move format '$moveInput'. Use coordinate notation, e.g. e2e4."
+            ))
+          case Some((from, to)) =>
+            handleParsedMove(from, to)
+  }
+
+  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)
+
+  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
+    }
+
+  /** 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(currentContext, "No promotion pending."))
+      case Some(pending) =>
+        pendingPromotion = None
+        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."))
+  }
+
+  /** Undo the last move. */
+  def undo(): Unit = synchronized { performUndo() }
+
+  /** 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))
+        }
+  }
+
+  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
+      Right(())
+    else
+      replayMoves(ctx.moves, savedContext)
+
+  private[engine] def replayMoves(moves: List[Move], savedContext: GameContext): Either[String, Unit] =
+    var error: Option[String] = None
+    moves.foreach: move =>
+      if error.isEmpty then
+        handleParsedMove(move.from, move.to)
+
+        move.moveType match {
+          case MoveType.Promotion(pp) =>
+            if pendingPromotion.isDefined then
+              completePromotion(pp)
+            else
+              error = Some(s"Promotion required for move ${move.from}${move.to}")
+          case _ => ()
+        }
+    error match
+      case Some(err) =>
+        currentContext = savedContext
+        Left(err)
+      case None =>
+        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(newContext: GameContext): Unit = synchronized {
+    currentContext = newContext
+    pendingPromotion = None
+    invoker.clear()
+    notifyObservers(BoardResetEvent(currentContext))
+  }
+
+  /** Reset the board to initial position. */
+  def reset(): Unit = synchronized {
+    currentContext = GameContext.initial
+    invoker.clear()
+    notifyObservers(BoardResetEvent(currentContext))
+  }
+
+  // ──── 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} ${c.pieceType.label}")
+    ))
+
+    if ruleSet.isCheckmate(currentContext) then
+      val winner = currentContext.turn.opposite
+      notifyObservers(CheckmateEvent(currentContext, winner))
+      invoker.clear()
+      currentContext = GameContext.initial
+    else if ruleSet.isStalemate(currentContext) then
+      notifyObservers(StalemateEvent(currentContext))
+      invoker.clear()
+      currentContext = GameContext.initial
+    else if ruleSet.isCheck(currentContext) then
+      notifyObservers(CheckDetectedEvent(currentContext))
+
+    if currentContext.halfMoveClock >= 100 then
+      notifyObservers(FiftyMoveRuleAvailableEvent(currentContext))
+
+  private def translateMoveToNotation(move: Move, boardBefore: Board): String =
+    move.moveType match
+      case MoveType.CastleKingside  => "O-O"
+      case MoveType.CastleQueenside => "O-O-O"
+      case MoveType.EnPassant   => enPassantNotation(move)
+      case MoveType.Promotion(pp) => promotionNotation(move, pp)
+      case MoveType.Normal(isCapture) => normalMoveNotation(move, boardBefore, isCapture)
+
+  private def enPassantNotation(move: Move): String =
+    s"${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${move.to}"
+      case None => move.to.toString
+
+  private[engine] def pieceNotation(pieceType: PieceType): String =
+    pieceType match
+      case PieceType.Knight => "N"
+      case PieceType.Bishop => "B"
+      case PieceType.Rook   => "R"
+      case PieceType.Queen  => "Q"
+      case PieceType.King   => "K"
+      case _                => ""
+
+  private def computeCaptured(context: GameContext, move: Move): Option[Piece] =
+    move.moveType match
+      case MoveType.EnPassant =>
+        // Captured pawn is on the same rank as the moving pawn, same file as destination
+        val capturedSquare = Square(move.to.file, move.from.rank)
+        context.board.pieceAt(capturedSquare)
+      case MoveType.CastleKingside | MoveType.CastleQueenside =>
+        None
+      case _ =>
+        context.board.pieceAt(move.to)
+
+  private def performUndo(): Unit =
+    if invoker.canUndo then
+      val cmd = invoker.history(invoker.getCurrentIndex)
+      (cmd: @unchecked) match
+        case moveCmd: MoveCommand =>
+          moveCmd.previousContext.foreach(currentContext = _)
+          invoker.undo()
+          notifyObservers(MoveUndoneEvent(currentContext, moveCmd.notation))
+    else
+      notifyObservers(InvalidMoveEvent(currentContext, "Nothing to undo."))
+
+  private def performRedo(): Unit =
+    if invoker.canRedo then
+      val cmd = invoker.history(invoker.getCurrentIndex + 1)
+      (cmd: @unchecked) match
+        case moveCmd: MoveCommand =>
+          for case MoveResult.Successful(nextCtx, cap) <- moveCmd.moveResult do
+            currentContext = nextCtx
+            invoker.redo()
+            val capturedDesc = cap.map(c => s"${c.color.label} ${c.pieceType.label}")
+            notifyObservers(MoveRedoneEvent(
+              currentContext,
+              moveCmd.notation,
+              moveCmd.from.toString,
+              moveCmd.to.toString,
+              capturedDesc
+            ))
+    else
+      notifyObservers(InvalidMoveEvent(currentContext, "Nothing to redo."))
@@ -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)
@@ -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)
@@ -1,24 +0,0 @@
-package de.nowchess.chess.logic
-
-import de.nowchess.api.board.Square
-
-/** 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]
-)
-
-/** Complete game history: ordered list of moves. */
-case class GameHistory(moves: List[HistoryMove] = List.empty):
-  def addMove(move: HistoryMove): GameHistory =
-    GameHistory(moves :+ move)
-
-  def addMove(from: Square, to: Square): GameHistory =
-    addMove(HistoryMove(from, to, None))
-
-  def addMove(from: Square, to: Square, castleSide: Option[CastleSide]): GameHistory =
-    addMove(HistoryMove(from, to, castleSide))
-
-object GameHistory:
-  val empty: GameHistory = GameHistory()
@@ -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
@@ -1,162 +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 1 else 6  // R2 = ordinal 1, R7 = ordinal 6
-
-    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 _ =>
-        legalTargets(board, from)
-
-  def isLegal(board: Board, history: GameHistory, from: Square, to: Square): Boolean =
-    legalTargets(board, history, from).contains(to)
@@ -1,35 +0,0 @@
-package de.nowchess.chess.notation
-
-import de.nowchess.api.board.*
-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 $blackMoveStr"
-
-      moveLines.mkString(" ") + " *"
-
-    if headerLines.isEmpty then moveText
-    else if moveText.isEmpty then headerLines
-    else s"$headerLines\n\n$moveText"
-
-  /** Convert a HistoryMove to algebraic notation. */
-  private def moveToAlgebraic(move: HistoryMove): String =
-    move.castleSide match
-      case Some(CastleSide.Kingside)  => "O-O"
-      case Some(CastleSide.Queenside) => "O-O-O"
-      case None => s"${move.from}${move.to}"
@@ -1,150 +0,0 @@
-package de.nowchess.chess.notation
-
-import de.nowchess.api.board.*
-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:
-
-  /** 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 = move.castleSide match
-                case Some(side) => board.withCastle(color, side)
-                case None       => board.withMove(move.from, move.to)._1
-              val newHistory = history.addMove(move)
-              (newBoard, newHistory, color.opposite, acc :+ move)
-
-    moves
-
-  /** 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)))
-
-      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)))
-
-      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))
-
-        disambiguated.headOption.map(from => HistoryMove(from, toSquare, None))
-
-  /** True if `sq` matches a disambiguation hint (file letter, rank digit, or both). */
-  private def matchesHint(sq: Square, hint: String): Boolean =
-    hint.foldLeft(true): (ok, c) =>
-      ok && (
-        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
-      )
-
-  /** 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
@@ -0,0 +1,110 @@
+package de.nowchess.chess.observer
+
+import de.nowchess.api.board.{Color, Square}
+import de.nowchess.api.game.GameContext
+
+/** Base trait for all game state events.
+ *  Events are immutable snapshots of game state changes.
+ */
+sealed trait GameEvent:
+  def context: GameContext
+
+/** Fired when a move is successfully executed. */
+case class MoveExecutedEvent(
+  context: GameContext,
+  fromSquare: String,
+  toSquare: String,
+  capturedPiece: Option[String]
+) extends GameEvent
+
+/** Fired when the current player is in check. */
+case class CheckDetectedEvent(
+  context: GameContext
+) extends GameEvent
+
+/** Fired when the game reaches checkmate. */
+case class CheckmateEvent(
+  context: GameContext,
+  winner: Color
+) extends GameEvent
+
+/** Fired when the game reaches stalemate. */
+case class StalemateEvent(
+  context: GameContext
+) extends GameEvent
+
+/** Fired when a move is invalid. */
+case class InvalidMoveEvent(
+  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(
+  context: GameContext,
+  from: Square,
+  to: Square
+) extends GameEvent
+
+/** Fired when the board is reset. */
+case class BoardResetEvent(
+  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(
+  context: GameContext
+) extends GameEvent
+
+/** Fired when a player successfully claims a draw under the 50-move rule. */
+case class DrawClaimedEvent(
+  context: GameContext
+) extends GameEvent
+
+/** Fired when a move is undone, carrying PGN notation of the reversed move. */
+case class MoveUndoneEvent(
+  context: GameContext,
+  pgnNotation: String
+) extends GameEvent
+
+/** Fired when a previously undone move is redone, carrying PGN notation of the replayed move. */
+case class MoveRedoneEvent(
+  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(
+  context: GameContext
+) extends GameEvent
+
+/** Observer trait: implement to receive game state updates. */
+trait Observer:
+  def onGameEvent(event: GameEvent): Unit
+
+/** Observable trait: manages observers and notifies them of events. */
+trait Observable:
+  private val observers = scala.collection.mutable.Set[Observer]()
+
+  /** Register an observer to receive game events. */
+  def subscribe(observer: Observer): Unit = synchronized {
+    observers += observer
+  }
+
+  /** Unregister an observer. */
+  def unsubscribe(observer: Observer): Unit = synchronized {
+    observers -= observer
+  }
+
+  /** Notify all observers of a game event. */
+  protected def notifyObservers(event: GameEvent): Unit = synchronized {
+    observers.foreach(_.onGameEvent(event))
+  }
+
+  /** Return current list of observers (for testing). */
+  def observerCount: Int = synchronized {
+    observers.size
+  }
@@ -0,0 +1,148 @@
+package de.nowchess.chess.command
+
+import de.nowchess.api.board.{Square, File, Rank}
+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)
+
+  private case class FailingCommand() extends Command:
+    override def execute(): Boolean = false
+    override def undo(): Boolean = false
+    override def description: String = "Failing command"
+
+  private case class ConditionalFailCommand(var shouldFailOnUndo: Boolean = false, var shouldFailOnExecute: Boolean = false) extends Command:
+    override def execute(): Boolean = !shouldFailOnExecute
+    override def undo(): Boolean = !shouldFailOnUndo
+    override def description: String = "Conditional fail"
+
+  private def createMoveCommand(from: Square, to: Square, executeSucceeds: Boolean = true): MoveCommand =
+    MoveCommand(
+      from = from,
+      to = to,
+      moveResult = if executeSucceeds then Some(MoveResult.Successful(GameContext.initial, None)) else None,
+      previousContext = Some(GameContext.initial)
+    )
+
+  test("execute rejects failing commands and keeps history unchanged"):
+    val invoker = new CommandInvoker()
+    val cmd = FailingCommand()
+    invoker.execute(cmd) shouldBe false
+    invoker.history.size shouldBe 0
+    invoker.getCurrentIndex shouldBe -1
+
+    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.head shouldBe successCmd
+
+  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
+    }
+
+    {
+      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
+    }
+
+    {
+      val invoker = new CommandInvoker()
+      val failingUndoCmd = ConditionalFailCommand(shouldFailOnUndo = true)
+      invoker.execute(failingUndoCmd) shouldBe true
+      invoker.canUndo shouldBe true
+      invoker.undo() shouldBe false
+      invoker.getCurrentIndex shouldBe 0
+    }
+
+    {
+      val invoker = new CommandInvoker()
+      val successUndoCmd = ConditionalFailCommand()
+      invoker.execute(successUndoCmd) shouldBe true
+      invoker.undo() shouldBe true
+      invoker.getCurrentIndex shouldBe -1
+    }
+
+    {
+      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
+    }
+
+    {
+      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 = true
+      invoker.redo() shouldBe false
+      invoker.getCurrentIndex shouldBe 0
+    }
+
+    {
+      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
+    }
+
+    {
+      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
+    }
@@ -0,0 +1,67 @@
+package de.nowchess.chess.command
+
+import de.nowchess.api.board.{Square, File, Rank}
+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(GameContext.initial, None)),
+      previousContext = Some(GameContext.initial)
+    )
+
+  test("execute appends commands and updates index"):
+    val invoker = new CommandInvoker()
+    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
+
+    val cmd2 = createMoveCommand(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
+    invoker.execute(cmd2) shouldBe true
+    invoker.history.size shouldBe 2
+    invoker.getCurrentIndex shouldBe 1
+
+  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
+    invoker.execute(cmd)
+    invoker.canUndo shouldBe true
+    invoker.undo() shouldBe true
+    invoker.getCurrentIndex shouldBe -1
+    invoker.canRedo shouldBe true
+    invoker.redo() shouldBe true
+    invoker.getCurrentIndex shouldBe 0
+
+  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.clear()
+    invoker.history.size shouldBe 0
+    invoker.getCurrentIndex shouldBe -1
+
+  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))
+    invoker.execute(cmd1)
+    invoker.execute(cmd2)
+    invoker.undo()
+    invoker.getCurrentIndex shouldBe 0
+    invoker.canRedo shouldBe true
+    invoker.execute(cmd3)
+    invoker.canRedo shouldBe false
+    invoker.history.size shouldBe 2
+    invoker.history.head shouldBe cmd1
+    invoker.history(1) shouldBe cmd3
+    invoker.getCurrentIndex shouldBe 1
@@ -0,0 +1,24 @@
+package de.nowchess.chess.command
+
+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 properties and behavior"):
+    val cmd = QuitCommand()
+    cmd shouldNot be(null)
+    cmd.execute() shouldBe true
+    cmd.undo() shouldBe false
+    cmd.description shouldBe "Quit game"
+
+  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
@@ -0,0 +1,70 @@
+package de.nowchess.chess.command
+
+import de.nowchess.api.board.{Square, File, Rank}
+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
--- a/Show More
+++ b/Show More
Author	SHA1	Message	Date
lq64	b4bc72f7e4	feat: NCS-30 FEN Parser using ParserCombinators (#21 ) Build & Test (NowChessSystems) TeamCity build finished Details Summary - Added scala-parser-combinators_3:2.4.0 dependency to modules/io - Implemented FenParserCombinators as an alternative FEN parser using RegexParsers, with the same public API as the existing FenParser - Parsers are built bottom-up: piece characters → rank tokens → rank → board, composed with explicit field separators into a full FEN parser - Added FenParserCombinatorsTest mirroring the existing FenParserTest to prove behavioural equivalence Test plan - All existing tests pass — FenParser and all other modules untouched - FenParserCombinatorsTest covers all cases: valid FEN, invalid color, invalid castling, invalid board shapes, en passant, round-trip via FenExporter - 100% line/branch/method coverage on FenParserCombinators Co-authored-by: LQ63 <lkhermann@web.de> Reviewed-on: #21 Reviewed-by: Janis <janis-e@gmx.de> Co-authored-by: Leon Hermann <lq@blackhole.local> Co-committed-by: Leon Hermann <lq@blackhole.local>	2026-04-07 12:28:43 +02:00
Janis	8959c3a849	refactor: NCS-24 update CLAUDE.md for improved structure and clarity (#20 ) Build & Test (NowChessSystems) TeamCity build finished Details Reviewed-on: #20 Reviewed-by: Leon Hermann <lq@blackhole.local> Co-authored-by: Janis <janis-e@gmx.de> Co-committed-by: Janis <janis-e@gmx.de>	2026-04-07 12:25:33 +02:00
TeamCity	47032378e2	ci: bump version with Build-31	2026-04-07 06:25:56 +00:00
lq64	217f14f899	refactor: NCS-19 Currying (#18 ) Build & Test (NowChessSystems) TeamCity build finished Details Summary - Curried candidateMoves, legalMoves, and applyMove in the RuleSet trait to separate (context) as the world being operated on from the computation parameter - Updated DefaultRules overrides and all internal call sites - Updated all external call sites: GameEngine, PgnParser, PgnExporter, ChessBoardView, and all affected tests Test plan - All existing tests pass (./gradlew build) - No behaviour changes — pure style refactoring, existing test suite is the regression guard Co-authored-by: LQ63 <lkhermann@web.de> Reviewed-on: #18 Reviewed-by: Janis <janis-e@gmx.de> Co-authored-by: Leon Hermann <lq@blackhole.local> Co-committed-by: Leon Hermann <lq@blackhole.local>	2026-04-06 21:03:17 +02:00
TeamCity	638139602c	ci: bump version with Build-30	2026-04-06 07:21:42 +00:00
Janis	8f56a82104	refactor: NCS-22 NCS-23 reworked modules and tests (#17 ) Build & Test (NowChessSystems) TeamCity build finished Details Reviewed-on: #17	2026-04-06 09:07:39 +02:00
TeamCity	51ffd7aac9	ci: bump version with Build-28	2026-04-03 09:09:16 +00:00
Janis	1b9eb471de	fix: set PYTHONUTF8 environment variable for coverage scripts (#16 ) Build & Test (NowChessSystems) TeamCity build finished Details Reviewed-on: #16 Co-authored-by: Janis <janis.e.20@gmx.de> Co-committed-by: Janis <janis.e.20@gmx.de>	2026-04-03 11:03:02 +02:00
TeamCity	45013c87a9	ci: bump version with Build-27	2026-04-02 19:15:54 +00:00
Janis	80518719d5	feat: NCS-21 Write Scripts to automate certain tasks (#15 ) Build & Test (NowChessSystems) TeamCity build finished Details Co-authored-by: shahdlala66 <shahd.lala66@gmail.com> Reviewed-on: #15 Co-authored-by: Janis <janis.e.20@gmx.de> Co-committed-by: Janis <janis.e.20@gmx.de>	2026-04-02 21:11:21 +02:00
TeamCity	2d6ead7e47	ci: bump version with Build-26	2026-04-01 20:53:08 +00:00
Janis	3ff80318b4	feat: NCS-17 Implement basic ScalaFX UI (#14 ) Build & Test (NowChessSystems) TeamCity build finished Details Co-authored-by: shahdlala66 <shahd.lala66@gmail.com> Reviewed-on: #14 Co-authored-by: Janis <janis.e.20@gmx.de> Co-committed-by: Janis <janis.e.20@gmx.de>	2026-04-01 22:48:30 +02:00
TeamCity	9fb743d135	ci: bump version with Build-25	2026-04-01 08:40:41 +00:00
lq64	412ed986a9	feat: NCS-11 50-move rule (#9 ) Build & Test (NowChessSystems) TeamCity build finished Details Summary - Implements the FIDE 50-move draw rule: a player may claim a draw if no pawn move or capture has occurred in the last 50 full moves (100 half-moves) - Draw is not automatic — the eligible player must claim it via a TUI menu shown at the start of their turn - halfMoveClock: Int is threaded through processMove and gameLoop; resets on pawn move, capture, or en passant; increments on all other moves Changes - GameController.scala: extended MoveResult.Moved and MoveResult.MovedInCheck with newHalfMoveClock: Int; added MoveResult.DrawClaimed; added halfMoveClock parameter to processMove and gameLoop; TUI menu shown when clock ≥ 100 - Main.scala: initial gameLoop call passes halfMoveClock = 0 - GameControllerTest.scala: updated all existing pattern matches; added 10 new tests covering clock reset, clock increment, draw claim, and TUI menu behaviour Test plan - processMove: 'draw' with halfMoveClock = 100 → DrawClaimed - processMove: 'draw' with halfMoveClock = 99 → InvalidFormat - Pawn move / capture / en passant → clock resets to 0 - Quiet piece move → clock increments by 1 - MovedInCheck carries updated clock - TUI menu appears when clock ≥ 100; option 1 claims draw, option 2 continues - No TUI menu when clock < 100 - All 197 tests passing Co-authored-by: LQ63 <lkhermann@web.de> Reviewed-on: #9 Co-authored-by: Leon Hermann <lq@blackhole.local> Co-committed-by: Leon Hermann <lq@blackhole.local>	2026-04-01 10:36:24 +02:00
TeamCity	8bbeead702	ci: bump version with Build-24	2026-04-01 07:17:44 +00:00
Janis	e5e20c566e	fix: update move validation to check for king safety (#13 ) Build & Test (NowChessSystems) TeamCity build finished Details Reviewed-on: #13	2026-04-01 09:07:06 +02:00
Janis	13bfc16cfe	feat: NCS-10 Implement Pawn Promotion (#12 ) Build & Test (NowChessSystems) TeamCity build finished Details Reviewed-on: #12 Reviewed-by: Leon Hermann <lq@blackhole.local> Co-authored-by: Janis <janis-e@gmx.de> Co-committed-by: Janis <janis-e@gmx.de>	2026-03-31 22:18:14 +02:00
TeamCity	85cbf95c18	ci: bump version with Build-22	2026-03-31 08:35:28 +00:00
shosho996	1361dfc895	feat: NCS-16 Core Separation via Patterns (#10 ) Build & Test (NowChessSystems) TeamCity build finished Details Co-authored-by: Janis <janis-e@gmx.de> Co-authored-by: shahdlala66 <shahd.lala66@gmail.com> Co-authored-by: Janis <janis.e.20@gmx.de> Reviewed-on: #10 Reviewed-by: Janis <janis-e@gmx.de> Co-authored-by: Shahd Lala <shosho996@blackhole.local> Co-committed-by: Shahd Lala <shosho996@blackhole.local>	2026-03-31 10:31:02 +02:00
TeamCity	707c4826a4	ci: bump version with Build-21	2026-03-29 15:10:35 +00:00
lq64	919beb3b4b	feat: NCS-9 En passant implementation (#8 ) Build & Test (NowChessSystems) TeamCity build finished Details - Add EnPassantCalculator to derive the en passant target square from GameHistory, detect en passant captures, and compute the captured pawn's square - Extend MoveValidator.legalTargets to include the en passant diagonal square in pawn legal targets - Extend GameController.processMove to remove the captured pawn from the board when an en passant capture is played Details En passant is derived purely from the last HistoryMove — no new state is introduced. If the last move was a double pawn push, the target square is the square the pawn passed through. The board mutation follows the same pattern as castling: board.withMove moves the capturing pawn, then board.removed removes the captured pawn from its actual square (which differs from the destination square). Test Plan - EnPassantCalculatorTest — 14 unit tests covering target derivation, captured square calculation, and capture detection for both colors - MoveValidatorTest — 5 new tests: ep target included/excluded based on history, adjacency filter, both colors, case _ branch coverage - GameControllerTest — 2 integration tests: white and black en passant capture removes pawn from board and returns correct captured piece - 100% scoverage (line/branch/method) confirmed Co-authored-by: LQ63 <lkhermann@web.de> Reviewed-on: #8 Reviewed-by: Janis <janis-e@gmx.de> Co-authored-by: Leon Hermann <lq@blackhole.local> Co-committed-by: Leon Hermann <lq@blackhole.local>	2026-03-29 17:06:50 +02:00
TeamCity	ee79dc5b98	ci: bump version with Build-20	2026-03-29 12:06:38 +00:00