refactor: NCS-22 NCS-23 reworked modules and tests (#17)
Build & Test (NowChessSystems) TeamCity build finished

Reviewed-on: #17
This commit was merged in pull request #17.
This commit is contained in:
2026-04-06 09:07:39 +02:00
parent 51ffd7aac9
commit 8f56a82104
98 changed files with 3752 additions and 5940 deletions
@@ -1,7 +1,7 @@
package de.nowchess.chess.command
import de.nowchess.api.board.{Square, Board, Color, Piece}
import de.nowchess.chess.logic.GameHistory
import de.nowchess.api.board.{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.
@@ -23,23 +23,22 @@ case class MoveCommand(
from: Square,
to: Square,
moveResult: Option[MoveResult] = None,
previousBoard: Option[Board] = None,
previousHistory: Option[GameHistory] = None,
previousTurn: Option[Color] = None
previousContext: Option[GameContext] = None,
notation: String = ""
) extends Command:
override def execute(): Boolean =
moveResult.isDefined
override def undo(): Boolean =
previousBoard.isDefined && previousHistory.isDefined && previousTurn.isDefined
previousContext.isDefined
override def description: String = s"Move from $from to $to"
// Sealed hierarchy of move outcomes (for tracking state changes)
sealed trait MoveResult
object MoveResult:
case class Successful(newBoard: Board, newHistory: GameHistory, newTurn: Color, captured: Option[Piece]) extends MoveResult
case class Successful(newContext: GameContext, captured: Option[Piece]) extends MoveResult
case object InvalidFormat extends MoveResult
case object InvalidMove extends MoveResult
@@ -51,14 +50,12 @@ case class QuitCommand() extends Command:
/** Command to reset the board to initial position. */
case class ResetCommand(
previousBoard: Option[Board] = None,
previousHistory: Option[GameHistory] = None,
previousTurn: Option[Color] = None
previousContext: Option[GameContext] = None
) extends Command:
override def execute(): Boolean = true
override def undo(): Boolean =
previousBoard.isDefined && previousHistory.isDefined && previousTurn.isDefined
previousContext.isDefined
override def description: String = "Reset board"
@@ -1,106 +0,0 @@
package de.nowchess.chess.controller
import de.nowchess.api.board.{Board, Color, File, Piece, PieceType, Rank, Square}
import de.nowchess.api.move.PromotionPiece
import de.nowchess.chess.logic.*
// ---------------------------------------------------------------------------
// Result ADT returned by the pure processMove function
// ---------------------------------------------------------------------------
sealed trait MoveResult
object MoveResult:
case object Quit extends MoveResult
case class InvalidFormat(raw: String) extends MoveResult
case object NoPiece extends MoveResult
case object WrongColor extends MoveResult
case object IllegalMove extends MoveResult
case class PromotionRequired(
from: Square,
to: Square,
boardBefore: Board,
historyBefore: GameHistory,
captured: Option[Piece],
turn: Color
) extends MoveResult
case class Moved(newBoard: Board, newHistory: GameHistory, captured: Option[Piece], newTurn: Color) extends MoveResult
case class MovedInCheck(newBoard: Board, newHistory: GameHistory, captured: Option[Piece], newTurn: Color) extends MoveResult
case class Checkmate(winner: Color) extends MoveResult
case object Stalemate extends MoveResult
// ---------------------------------------------------------------------------
// Controller
// ---------------------------------------------------------------------------
object GameController:
/** Pure function: interprets one raw input line against the current game context.
* Has no I/O side effects all output must be handled by the caller.
*/
def processMove(board: Board, history: GameHistory, turn: Color, raw: String): MoveResult =
raw.trim match
case "quit" | "q" => MoveResult.Quit
case trimmed =>
Parser.parseMove(trimmed) match
case None => MoveResult.InvalidFormat(trimmed)
case Some((from, to)) => validateAndApply(board, history, turn, from, to)
/** Apply a previously detected promotion move with the chosen piece.
* Called after processMove returned PromotionRequired.
*/
def completePromotion(
board: Board,
history: GameHistory,
from: Square,
to: Square,
piece: PromotionPiece,
turn: Color
): MoveResult =
val (boardAfterMove, captured) = board.withMove(from, to)
val promotedPieceType = piece match
case PromotionPiece.Queen => PieceType.Queen
case PromotionPiece.Rook => PieceType.Rook
case PromotionPiece.Bishop => PieceType.Bishop
case PromotionPiece.Knight => PieceType.Knight
val newBoard = boardAfterMove.updated(to, Piece(turn, promotedPieceType))
// Promotion is always a pawn move → clock resets
val newHistory = history.addMove(from, to, None, Some(piece), wasPawnMove = true)
toMoveResult(newBoard, newHistory, captured, turn)
// ---------------------------------------------------------------------------
// Private helpers
// ---------------------------------------------------------------------------
private def validateAndApply(board: Board, history: GameHistory, turn: Color, from: Square, to: Square): MoveResult =
board.pieceAt(from) match
case None => MoveResult.NoPiece
case Some(piece) if piece.color != turn => MoveResult.WrongColor
case Some(_) =>
if !GameRules.legalMoves(board, history, turn).contains(from -> to) then MoveResult.IllegalMove
else if MoveValidator.isPromotionMove(board, from, to) then
MoveResult.PromotionRequired(from, to, board, history, board.pieceAt(to), turn)
else applyNormalMove(board, history, turn, from, to)
private def applyNormalMove(board: Board, history: GameHistory, turn: Color, from: Square, to: Square): MoveResult =
val castleOpt = Option.when(MoveValidator.isCastle(board, from, to))(MoveValidator.castleSide(from, to))
val isEP = EnPassantCalculator.isEnPassant(board, history, from, to)
val (newBoard, captured) = castleOpt match
case Some(side) => (board.withCastle(turn, side), None)
case None =>
val (b, cap) = board.withMove(from, to)
if isEP then
val capturedSq = EnPassantCalculator.capturedPawnSquare(to, turn)
(b.removed(capturedSq), board.pieceAt(capturedSq))
else (b, cap)
val pieceType = board.pieceAt(from).map(_.pieceType).getOrElse(PieceType.Pawn)
val wasPawnMove = pieceType == PieceType.Pawn
val wasCapture = captured.isDefined
val newHistory = history.addMove(from, to, castleOpt, wasPawnMove = wasPawnMove, wasCapture = wasCapture, pieceType = pieceType)
toMoveResult(newBoard, newHistory, captured, turn)
private def toMoveResult(newBoard: Board, newHistory: GameHistory, captured: Option[Piece], turn: Color): MoveResult =
GameRules.gameStatus(newBoard, newHistory, turn.opposite) match
case PositionStatus.Normal => MoveResult.Moved(newBoard, newHistory, captured, turn.opposite)
case PositionStatus.InCheck => MoveResult.MovedInCheck(newBoard, newHistory, captured, turn.opposite)
case PositionStatus.Mated => MoveResult.Checkmate(turn)
case PositionStatus.Drawn => MoveResult.Stalemate
@@ -1,47 +1,37 @@
package de.nowchess.chess.engine
import de.nowchess.api.board.{Board, Color, Piece, Square}
import de.nowchess.api.move.PromotionPiece
import de.nowchess.chess.logic.{GameHistory, GameRules, PositionStatus}
import de.nowchess.chess.controller.{GameController, Parser, MoveResult}
import de.nowchess.api.board.{Board, Color, Piece, PieceType, Square}
import de.nowchess.api.move.{Move, MoveType, PromotionPiece}
import de.nowchess.api.game.GameContext
import de.nowchess.chess.controller.Parser
import de.nowchess.chess.observer.*
import de.nowchess.chess.command.{CommandInvoker, MoveCommand}
import de.nowchess.chess.notation.{PgnExporter, PgnParser}
import de.nowchess.chess.command.{CommandInvoker, MoveCommand, MoveResult}
import de.nowchess.io.{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.
* This class is the single source of truth for the game state.
* All user interactions must go through this engine via Commands, and all state changes
* are communicated to observers via GameEvent notifications.
* All rule queries delegate to the injected RuleSet.
* All user interactions go through Commands; state changes are broadcast via GameEvents.
*/
class GameEngine(
initialBoard: Board = Board.initial,
initialHistory: GameHistory = GameHistory.empty,
initialTurn: Color = Color.White,
completePromotionFn: (Board, GameHistory, Square, Square, PromotionPiece, Color) => MoveResult =
GameController.completePromotion
val initialContext: GameContext = GameContext.initial,
val ruleSet: RuleSet = DefaultRules
) extends Observable:
private var currentBoard: Board = initialBoard
private var currentHistory: GameHistory = initialHistory
private var currentTurn: Color = initialTurn
private var currentContext: GameContext = initialContext
private val invoker = new CommandInvoker()
/** Inner class for tracking pending promotion state */
private case class PendingPromotion(
from: Square, to: Square,
boardBefore: Board, historyBefore: GameHistory,
turn: Color
)
/** Current pending promotion, if any */
/** Pending promotion: the Move that triggered it (from/to only, moveType filled in later). */
private case class PendingPromotion(from: Square, to: Square, contextBefore: GameContext)
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 { currentBoard }
def history: GameHistory = synchronized { currentHistory }
def turn: Color = synchronized { currentTurn }
def board: Board = synchronized { currentContext.board }
def turn: Color = synchronized { currentContext.turn }
def context: GameContext = synchronized { currentContext }
/** Check if undo is available. */
def canUndo: Boolean = synchronized { invoker.canUndo }
@@ -59,7 +49,6 @@ class GameEngine(
val trimmed = rawInput.trim.toLowerCase
trimmed match
case "quit" | "q" =>
// Client should handle quit logic; we just return
()
case "undo" =>
@@ -69,96 +58,55 @@ class GameEngine(
performRedo()
case "draw" =>
if currentHistory.halfMoveClock >= 100 then
currentBoard = Board.initial
currentHistory = GameHistory.empty
currentTurn = Color.White
if currentContext.halfMoveClock >= 100 then
invoker.clear()
notifyObservers(DrawClaimedEvent(currentBoard, currentHistory, currentTurn))
notifyObservers(DrawClaimedEvent(currentContext))
else
notifyObservers(InvalidMoveEvent(
currentBoard, currentHistory, currentTurn,
currentContext,
"Draw cannot be claimed: the 50-move rule has not been triggered."
))
case "" =>
val event = InvalidMoveEvent(
currentBoard,
currentHistory,
currentTurn,
"Please enter a valid move or command."
)
notifyObservers(event)
notifyObservers(InvalidMoveEvent(currentContext, "Please enter a valid move or command."))
case moveInput =>
Parser.parseMove(moveInput) match
case None =>
notifyObservers(InvalidMoveEvent(
currentBoard, currentHistory, currentTurn,
currentContext,
s"Invalid move format '$moveInput'. Use coordinate notation, e.g. e2e4."
))
case Some((from, to)) =>
handleParsedMove(from, to, moveInput)
handleParsedMove(from, to)
}
private def handleParsedMove(from: Square, to: Square, moveInput: String): Unit =
val cmd = MoveCommand(
from = from,
to = to,
previousBoard = Some(currentBoard),
previousHistory = Some(currentHistory),
previousTurn = Some(currentTurn)
)
GameController.processMove(currentBoard, currentHistory, currentTurn, moveInput) match
case MoveResult.InvalidFormat(_) | MoveResult.NoPiece | MoveResult.WrongColor | MoveResult.IllegalMove | MoveResult.Quit =>
handleFailedMove(moveInput)
private def handleParsedMove(from: Square, to: Square): Unit =
currentContext.board.pieceAt(from) match
case None =>
notifyObservers(InvalidMoveEvent(currentContext, "No piece on that square."))
case Some(piece) if piece.color != currentContext.turn =>
notifyObservers(InvalidMoveEvent(currentContext, "That is not your piece."))
case Some(piece) =>
val legal = ruleSet.legalMoves(currentContext, from)
// Find all legal moves going to `to`
val candidates = legal.filter(_.to == to)
candidates match
case Nil =>
notifyObservers(InvalidMoveEvent(currentContext, "Illegal move."))
case moves if isPromotionMove(piece, to) =>
// Multiple moves (one per promotion piece) — ask user to choose
val contextBefore = currentContext
pendingPromotion = Some(PendingPromotion(from, to, contextBefore))
notifyObservers(PromotionRequiredEvent(currentContext, from, to))
case move :: _ =>
executeMove(move)
case MoveResult.Moved(newBoard, newHistory, captured, newTurn) =>
val updatedCmd = cmd.copy(moveResult = Some(de.nowchess.chess.command.MoveResult.Successful(newBoard, newHistory, newTurn, captured)))
invoker.execute(updatedCmd)
updateGameState(newBoard, newHistory, newTurn)
emitMoveEvent(from.toString, to.toString, captured, newTurn)
if currentHistory.halfMoveClock >= 100 then
notifyObservers(FiftyMoveRuleAvailableEvent(currentBoard, currentHistory, currentTurn))
case MoveResult.MovedInCheck(newBoard, newHistory, captured, newTurn) =>
val updatedCmd = cmd.copy(moveResult = Some(de.nowchess.chess.command.MoveResult.Successful(newBoard, newHistory, newTurn, captured)))
invoker.execute(updatedCmd)
updateGameState(newBoard, newHistory, newTurn)
emitMoveEvent(from.toString, to.toString, captured, newTurn)
notifyObservers(CheckDetectedEvent(currentBoard, currentHistory, currentTurn))
if currentHistory.halfMoveClock >= 100 then
notifyObservers(FiftyMoveRuleAvailableEvent(currentBoard, currentHistory, currentTurn))
case MoveResult.Checkmate(winner) =>
val updatedCmd = cmd.copy(moveResult = Some(de.nowchess.chess.command.MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)))
invoker.execute(updatedCmd)
currentBoard = Board.initial
currentHistory = GameHistory.empty
currentTurn = Color.White
notifyObservers(CheckmateEvent(currentBoard, currentHistory, currentTurn, winner))
case MoveResult.Stalemate =>
val updatedCmd = cmd.copy(moveResult = Some(de.nowchess.chess.command.MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)))
invoker.execute(updatedCmd)
currentBoard = Board.initial
currentHistory = GameHistory.empty
currentTurn = Color.White
notifyObservers(StalemateEvent(currentBoard, currentHistory, currentTurn))
case MoveResult.PromotionRequired(promFrom, promTo, boardBefore, histBefore, _, promotingTurn) =>
pendingPromotion = Some(PendingPromotion(promFrom, promTo, boardBefore, histBefore, promotingTurn))
notifyObservers(PromotionRequiredEvent(currentBoard, currentHistory, currentTurn, promFrom, promTo))
/** Undo the last move. */
def undo(): Unit = synchronized {
performUndo()
}
/** Redo the last undone move. */
def redo(): Unit = synchronized {
performRedo()
}
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.
@@ -166,187 +114,205 @@ class GameEngine(
def completePromotion(piece: PromotionPiece): Unit = synchronized {
pendingPromotion match
case None =>
notifyObservers(InvalidMoveEvent(currentBoard, currentHistory, currentTurn, "No promotion pending."))
notifyObservers(InvalidMoveEvent(currentContext, "No promotion pending."))
case Some(pending) =>
pendingPromotion = None
val cmd = MoveCommand(
from = pending.from,
to = pending.to,
previousBoard = Some(pending.boardBefore),
previousHistory = Some(pending.historyBefore),
previousTurn = Some(pending.turn)
)
completePromotionFn(
pending.boardBefore, pending.historyBefore,
pending.from, pending.to, piece, pending.turn
) match
case MoveResult.Moved(newBoard, newHistory, captured, newTurn) =>
val updatedCmd = cmd.copy(moveResult = Some(de.nowchess.chess.command.MoveResult.Successful(newBoard, newHistory, newTurn, captured)))
invoker.execute(updatedCmd)
updateGameState(newBoard, newHistory, newTurn)
emitMoveEvent(pending.from.toString, pending.to.toString, captured, newTurn)
case MoveResult.MovedInCheck(newBoard, newHistory, captured, newTurn) =>
val updatedCmd = cmd.copy(moveResult = Some(de.nowchess.chess.command.MoveResult.Successful(newBoard, newHistory, newTurn, captured)))
invoker.execute(updatedCmd)
updateGameState(newBoard, newHistory, newTurn)
emitMoveEvent(pending.from.toString, pending.to.toString, captured, newTurn)
notifyObservers(CheckDetectedEvent(currentBoard, currentHistory, currentTurn))
case MoveResult.Checkmate(winner) =>
val updatedCmd = cmd.copy(moveResult = Some(de.nowchess.chess.command.MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)))
invoker.execute(updatedCmd)
currentBoard = Board.initial
currentHistory = GameHistory.empty
currentTurn = Color.White
notifyObservers(CheckmateEvent(currentBoard, currentHistory, currentTurn, winner))
case MoveResult.Stalemate =>
val updatedCmd = cmd.copy(moveResult = Some(de.nowchess.chess.command.MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)))
invoker.execute(updatedCmd)
currentBoard = Board.initial
currentHistory = GameHistory.empty
currentTurn = Color.White
notifyObservers(StalemateEvent(currentBoard, currentHistory, currentTurn))
case _ =>
notifyObservers(InvalidMoveEvent(currentBoard, currentHistory, currentTurn, "Error completing promotion."))
val move = Move(pending.from, pending.to, MoveType.Promotion(piece))
// Verify it's actually legal
val legal = ruleSet.legalMoves(currentContext, pending.from)
if legal.contains(move) then
executeMove(move)
else
notifyObservers(InvalidMoveEvent(currentContext, "Error completing promotion."))
}
/** Validate and load a PGN string.
* Each move is replayed through the command system so undo/redo is available after loading.
* Returns Right(()) on success; Left(error) if any move is illegal or the position impossible. */
def loadPgn(pgn: String): Either[String, Unit] = synchronized {
PgnParser.validatePgn(pgn) match
case Left(err) =>
Left(err)
case Right(game) =>
val initialBoardBeforeLoad = currentBoard
val initialHistoryBeforeLoad = currentHistory
val initialTurnBeforeLoad = currentTurn
currentBoard = Board.initial
currentHistory = GameHistory.empty
currentTurn = Color.White
pendingPromotion = None
invoker.clear()
/** Undo the last move. */
def undo(): Unit = synchronized { performUndo() }
var error: Option[String] = None
import scala.util.control.Breaks._
breakable {
game.moves.foreach { move =>
handleParsedMove(move.from, move.to, s"${move.from}${move.to}")
move.promotionPiece.foreach(completePromotion)
// If the move failed to execute properly, stop and report
// (validatePgn should have caught this, but we're being safe)
if pendingPromotion.isDefined && move.promotionPiece.isEmpty then
error = Some(s"Promotion required for move ${move.from}${move.to}")
break()
}
/** Redo the last undone move. */
def redo(): Unit = synchronized { performRedo() }
/** Load a game using the provided importer.
* If the imported context has moves, they are replayed through the command system.
* Otherwise, the position is set directly.
* Notifies observers with PgnLoadedEvent on success.
*/
def loadGame(importer: GameContextImport, input: String): Either[String, Unit] = synchronized {
importer.importGameContext(input) match
case Left(err) => Left(err)
case Right(ctx) =>
replayGame(ctx).map { _ =>
notifyObservers(PgnLoadedEvent(currentContext))
}
error match
case Some(err) =>
currentBoard = initialBoardBeforeLoad
currentHistory = initialHistoryBeforeLoad
currentTurn = initialTurnBeforeLoad
Left(err)
case None =>
notifyObservers(PgnLoadedEvent(currentBoard, currentHistory, currentTurn))
Right(())
}
private def replayGame(ctx: GameContext): Either[String, Unit] =
val savedContext = currentContext
currentContext = GameContext.initial
pendingPromotion = None
invoker.clear()
if ctx.moves.isEmpty then
currentContext = ctx
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(board: Board, history: GameHistory, turn: Color): Unit = synchronized {
currentBoard = board
currentHistory = history
currentTurn = turn
def loadPosition(newContext: GameContext): Unit = synchronized {
currentContext = newContext
pendingPromotion = None
invoker.clear()
notifyObservers(BoardResetEvent(currentBoard, currentHistory, currentTurn))
notifyObservers(BoardResetEvent(currentContext))
}
/** Reset the board to initial position. */
def reset(): Unit = synchronized {
currentBoard = Board.initial
currentHistory = GameHistory.empty
currentTurn = Color.White
currentContext = GameContext.initial
invoker.clear()
notifyObservers(BoardResetEvent(
currentBoard,
currentHistory,
currentTurn
))
notifyObservers(BoardResetEvent(currentContext))
}
// ──── Private Helpers ────
// ──── Private helpers ────
private def executeMove(move: Move): Unit =
val contextBefore = currentContext
val nextContext = ruleSet.applyMove(currentContext, move)
val captured = computeCaptured(currentContext, move)
val cmd = MoveCommand(
from = move.from,
to = move.to,
moveResult = Some(MoveResult.Successful(nextContext, captured)),
previousContext = Some(contextBefore),
notation = translateMoveToNotation(move, contextBefore.board)
)
invoker.execute(cmd)
currentContext = nextContext
notifyObservers(MoveExecutedEvent(
currentContext,
move.from.toString,
move.to.toString,
captured.map(c => s"${c.color.label} ${c.pieceType.label}")
))
if ruleSet.isCheckmate(currentContext) then
val winner = currentContext.turn.opposite
notifyObservers(CheckmateEvent(currentContext, winner))
invoker.clear()
currentContext = GameContext.initial
else if ruleSet.isStalemate(currentContext) then
notifyObservers(StalemateEvent(currentContext))
invoker.clear()
currentContext = GameContext.initial
else if ruleSet.isCheck(currentContext) then
notifyObservers(CheckDetectedEvent(currentContext))
if currentContext.halfMoveClock >= 100 then
notifyObservers(FiftyMoveRuleAvailableEvent(currentContext))
private def translateMoveToNotation(move: Move, boardBefore: Board): String =
move.moveType match
case MoveType.CastleKingside => "O-O"
case MoveType.CastleQueenside => "O-O-O"
case MoveType.EnPassant => enPassantNotation(move)
case MoveType.Promotion(pp) => promotionNotation(move, pp)
case MoveType.Normal(isCapture) => normalMoveNotation(move, boardBefore, isCapture)
private def enPassantNotation(move: Move): String =
s"${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${move.to}"
case None => move.to.toString
private[engine] def pieceNotation(pieceType: PieceType): String =
pieceType match
case PieceType.Knight => "N"
case PieceType.Bishop => "B"
case PieceType.Rook => "R"
case PieceType.Queen => "Q"
case PieceType.King => "K"
case _ => ""
private def computeCaptured(context: GameContext, move: Move): Option[Piece] =
move.moveType match
case MoveType.EnPassant =>
// Captured pawn is on the same rank as the moving pawn, same file as destination
val capturedSquare = Square(move.to.file, move.from.rank)
context.board.pieceAt(capturedSquare)
case MoveType.CastleKingside | MoveType.CastleQueenside =>
None
case _ =>
context.board.pieceAt(move.to)
private def performUndo(): Unit =
if invoker.canUndo then
val cmd = invoker.history(invoker.getCurrentIndex)
(cmd: @unchecked) match
case moveCmd: MoveCommand =>
val notation = currentHistory.moves.lastOption.map(PgnExporter.moveToAlgebraic).getOrElse("")
moveCmd.previousBoard.foreach(currentBoard = _)
moveCmd.previousHistory.foreach(currentHistory = _)
moveCmd.previousTurn.foreach(currentTurn = _)
moveCmd.previousContext.foreach(currentContext = _)
invoker.undo()
notifyObservers(MoveUndoneEvent(currentBoard, currentHistory, currentTurn, notation))
notifyObservers(MoveUndoneEvent(currentContext, moveCmd.notation))
else
notifyObservers(InvalidMoveEvent(currentBoard, currentHistory, currentTurn, "Nothing to undo."))
notifyObservers(InvalidMoveEvent(currentContext, "Nothing to undo."))
private def performRedo(): Unit =
if invoker.canRedo then
val cmd = invoker.history(invoker.getCurrentIndex + 1)
(cmd: @unchecked) match
case moveCmd: MoveCommand =>
for case de.nowchess.chess.command.MoveResult.Successful(nb, nh, nt, cap) <- moveCmd.moveResult do
updateGameState(nb, nh, nt)
for case MoveResult.Successful(nextCtx, cap) <- moveCmd.moveResult do
currentContext = nextCtx
invoker.redo()
val notation = nh.moves.lastOption.map(PgnExporter.moveToAlgebraic).getOrElse("")
val capturedDesc = cap.map(c => s"${c.color.label} ${c.pieceType.label}")
notifyObservers(MoveRedoneEvent(currentBoard, currentHistory, currentTurn, notation, moveCmd.from.toString, moveCmd.to.toString, capturedDesc))
notifyObservers(MoveRedoneEvent(
currentContext,
moveCmd.notation,
moveCmd.from.toString,
moveCmd.to.toString,
capturedDesc
))
else
notifyObservers(InvalidMoveEvent(currentBoard, currentHistory, currentTurn, "Nothing to redo."))
private def updateGameState(newBoard: Board, newHistory: GameHistory, newTurn: Color): Unit =
currentBoard = newBoard
currentHistory = newHistory
currentTurn = newTurn
private def emitMoveEvent(fromSq: String, toSq: String, captured: Option[Piece], newTurn: Color): Unit =
val capturedDesc = captured.map(c => s"${c.color.label} ${c.pieceType.label}")
notifyObservers(MoveExecutedEvent(
currentBoard,
currentHistory,
newTurn,
fromSq,
toSq,
capturedDesc
))
private def handleFailedMove(moveInput: String): Unit =
(GameController.processMove(currentBoard, currentHistory, currentTurn, moveInput): @unchecked) match
case MoveResult.NoPiece =>
notifyObservers(InvalidMoveEvent(
currentBoard,
currentHistory,
currentTurn,
"No piece on that square."
))
case MoveResult.WrongColor =>
notifyObservers(InvalidMoveEvent(
currentBoard,
currentHistory,
currentTurn,
"That is not your piece."
))
case MoveResult.IllegalMove =>
notifyObservers(InvalidMoveEvent(
currentBoard,
currentHistory,
currentTurn,
"Illegal move."
))
notifyObservers(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)
@@ -1,32 +0,0 @@
package de.nowchess.chess.logic
import de.nowchess.api.board.*
object EnPassantCalculator:
/** Returns the en passant target square if the last move was a double pawn push.
* The target is the square the pawn passed through (e.g. e2e4 yields e3).
*/
def enPassantTarget(board: Board, history: GameHistory): Option[Square] =
history.moves.lastOption.flatMap: move =>
val rankDiff = move.to.rank.ordinal - move.from.rank.ordinal
val isDoublePush = math.abs(rankDiff) == 2
val isPawn = board.pieceAt(move.to).exists(_.pieceType == PieceType.Pawn)
if isDoublePush && isPawn then
val midRankIdx = move.from.rank.ordinal + rankDiff / 2
Some(Square(move.to.file, Rank.values(midRankIdx)))
else None
/** True if moving from→to is an en passant capture. */
def isEnPassant(board: Board, history: GameHistory, from: Square, to: Square): Boolean =
board.pieceAt(from).exists(_.pieceType == PieceType.Pawn) &&
enPassantTarget(board, history).contains(to) &&
math.abs(to.file.ordinal - from.file.ordinal) == 1
/** Returns the square of the pawn to remove when an en passant capture lands on `to`.
* White captures upward → captured pawn is one rank below `to`.
* Black captures downward → captured pawn is one rank above `to`.
*/
def capturedPawnSquare(to: Square, color: Color): Square =
val capturedRankIdx = to.rank.ordinal + (if color == Color.White then -1 else 1)
Square(to.file, Rank.values(capturedRankIdx))
@@ -1,49 +0,0 @@
package de.nowchess.chess.logic
import de.nowchess.api.board.{PieceType, Square}
import de.nowchess.api.move.PromotionPiece
/** A single move recorded in the game history. Distinct from api.move.Move which represents user intent. */
case class HistoryMove(
from: Square,
to: Square,
castleSide: Option[CastleSide],
promotionPiece: Option[PromotionPiece] = None,
pieceType: PieceType = PieceType.Pawn,
isCapture: Boolean = false
)
/** Complete game history: ordered list of moves plus the half-move clock for the 50-move rule.
*
* @param moves moves played so far, oldest first
* @param halfMoveClock plies since the last pawn move or capture (FIDE 50-move rule counter)
*/
case class GameHistory(moves: List[HistoryMove] = List.empty, halfMoveClock: Int = 0):
/** Add a raw HistoryMove record. Clock increments by 1.
* Use the coordinate overload when you know whether the move is a pawn move or capture.
*/
def addMove(move: HistoryMove): GameHistory =
GameHistory(moves :+ move, halfMoveClock + 1)
/** Add a move by coordinates.
*
* @param wasPawnMove true when the moving piece is a pawn — resets the clock to 0
* @param wasCapture true when a piece was captured (including en passant) — resets the clock to 0
*
* If neither flag is set the clock increments by 1.
*/
def addMove(
from: Square,
to: Square,
castleSide: Option[CastleSide] = None,
promotionPiece: Option[PromotionPiece] = None,
wasPawnMove: Boolean = false,
wasCapture: Boolean = false,
pieceType: PieceType = PieceType.Pawn
): GameHistory =
val newClock = if wasPawnMove || wasCapture then 0 else halfMoveClock + 1
GameHistory(moves :+ HistoryMove(from, to, castleSide, promotionPiece, pieceType, wasCapture), newClock)
object GameHistory:
val empty: GameHistory = GameHistory()
@@ -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
@@ -1,183 +0,0 @@
package de.nowchess.chess.logic
import de.nowchess.api.board.*
import de.nowchess.chess.logic.{CastleSide, GameHistory}
object MoveValidator:
/** Returns true if the move is geometrically legal for the piece on `from`,
* ignoring check/pin but respecting:
* - correct movement pattern for the piece type
* - cannot capture own pieces
* - sliding pieces (bishop, rook, queen) are blocked by intervening pieces
*/
def isLegal(board: Board, from: Square, to: Square): Boolean =
legalTargets(board, from).contains(to)
/** All squares a piece on `from` can legally move to (same rules as isLegal). */
def legalTargets(board: Board, from: Square): Set[Square] =
board.pieceAt(from) match
case None => Set.empty
case Some(piece) =>
piece.pieceType match
case PieceType.Pawn => pawnTargets(board, from, piece.color)
case PieceType.Knight => knightTargets(board, from, piece.color)
case PieceType.Bishop => slide(board, from, piece.color, diagonalDeltas)
case PieceType.Rook => slide(board, from, piece.color, orthogonalDeltas)
case PieceType.Queen => slide(board, from, piece.color, diagonalDeltas ++ orthogonalDeltas)
case PieceType.King => kingTargets(board, from, piece.color)
// ── helpers ────────────────────────────────────────────────────────────────
private val diagonalDeltas: List[(Int, Int)] = List((1, 1), (1, -1), (-1, 1), (-1, -1))
private val orthogonalDeltas: List[(Int, Int)] = List((1, 0), (-1, 0), (0, 1), (0, -1))
private val knightDeltas: List[(Int, Int)] =
List((1, 2), (1, -2), (-1, 2), (-1, -2), (2, 1), (2, -1), (-2, 1), (-2, -1))
/** Try to construct a Square from integer file/rank indices (0-based). */
private def squareAt(fileIdx: Int, rankIdx: Int): Option[Square] =
Option.when(fileIdx >= 0 && fileIdx <= 7 && rankIdx >= 0 && rankIdx <= 7)(
Square(File.values(fileIdx), Rank.values(rankIdx))
)
/** True when `sq` is occupied by a piece of `color`. */
private def isOwnPiece(board: Board, sq: Square, color: Color): Boolean =
board.pieceAt(sq).exists(_.color == color)
/** True when `sq` is occupied by a piece of the opposite color. */
private def isEnemyPiece(board: Board, sq: Square, color: Color): Boolean =
board.pieceAt(sq).exists(_.color != color)
/** Sliding move generation along a list of direction deltas.
* Each direction continues until the board edge, an own piece, or the first
* enemy piece (which is included as a capture target).
*/
private def slide(board: Board, from: Square, color: Color, deltas: List[(Int, Int)]): Set[Square] =
val fi = from.file.ordinal
val ri = from.rank.ordinal
deltas.flatMap: (df, dr) =>
Iterator
.iterate((fi + df, ri + dr)) { case (f, r) => (f + df, r + dr) }
.takeWhile { case (f, r) => f >= 0 && f <= 7 && r >= 0 && r <= 7 }
.map { case (f, r) => Square(File.values(f), Rank.values(r)) }
.foldLeft((List.empty[Square], false)):
case ((acc, stopped), sq) =>
if stopped then (acc, true)
else if isOwnPiece(board, sq, color) then (acc, true) // blocked — stop, no capture
else if isEnemyPiece(board, sq, color) then (acc :+ sq, true) // capture — stop after
else (acc :+ sq, false) // empty — continue
._1
.toSet
private def pawnTargets(board: Board, from: Square, color: Color): Set[Square] =
val fi = from.file.ordinal
val ri = from.rank.ordinal
val dir = if color == Color.White then 1 else -1
val startRank = if color == Color.White then Rank.R2.ordinal else Rank.R7.ordinal
val oneStep = squareAt(fi, ri + dir)
// Forward one square (only if empty)
val forward1: Set[Square] = oneStep match
case Some(sq) if board.pieceAt(sq).isEmpty => Set(sq)
case _ => Set.empty
// Forward two squares from starting rank (only if both intermediate squares are empty)
val forward2: Set[Square] =
if ri == startRank && forward1.nonEmpty then
squareAt(fi, ri + 2 * dir) match
case Some(sq) if board.pieceAt(sq).isEmpty => Set(sq)
case _ => Set.empty
else Set.empty
// Diagonal captures (only if enemy piece present)
val captures: Set[Square] =
List(-1, 1).flatMap: df =>
squareAt(fi + df, ri + dir).filter(sq => isEnemyPiece(board, sq, color))
.toSet
forward1 ++ forward2 ++ captures
private def knightTargets(board: Board, from: Square, color: Color): Set[Square] =
val fi = from.file.ordinal
val ri = from.rank.ordinal
knightDeltas.flatMap: (df, dr) =>
squareAt(fi + df, ri + dr).filterNot(sq => isOwnPiece(board, sq, color))
.toSet
private def kingTargets(board: Board, from: Square, color: Color): Set[Square] =
val fi = from.file.ordinal
val ri = from.rank.ordinal
(diagonalDeltas ++ orthogonalDeltas).flatMap: (df, dr) =>
squareAt(fi + df, ri + dr).filterNot(sq => isOwnPiece(board, sq, color))
.toSet
// ── Castling helpers ────────────────────────────────────────────────────────
private def isAttackedBy(board: Board, sq: Square, attackerColor: Color): Boolean =
board.pieces.exists { case (from, piece) =>
piece.color == attackerColor && legalTargets(board, from).contains(sq)
}
def isCastle(board: Board, from: Square, to: Square): Boolean =
board.pieceAt(from).exists(_.pieceType == PieceType.King) &&
math.abs(to.file.ordinal - from.file.ordinal) == 2
def castleSide(from: Square, to: Square): CastleSide =
if to.file.ordinal > from.file.ordinal then CastleSide.Kingside else CastleSide.Queenside
def castlingTargets(board: Board, history: GameHistory, color: Color): Set[Square] =
val rights = CastlingRightsCalculator.deriveCastlingRights(history, color)
val rank = if color == Color.White then Rank.R1 else Rank.R8
val kingSq = Square(File.E, rank)
val enemy = color.opposite
if !board.pieceAt(kingSq).contains(Piece(color, PieceType.King)) ||
GameRules.isInCheck(board, color) then Set.empty
else
val kingsideSq = Option.when(
rights.kingSide &&
board.pieceAt(Square(File.H, rank)).contains(Piece(color, PieceType.Rook)) &&
List(Square(File.F, rank), Square(File.G, rank)).forall(s => board.pieceAt(s).isEmpty) &&
!List(Square(File.F, rank), Square(File.G, rank)).exists(s => isAttackedBy(board, s, enemy))
)(Square(File.G, rank))
val queensideSq = Option.when(
rights.queenSide &&
board.pieceAt(Square(File.A, rank)).contains(Piece(color, PieceType.Rook)) &&
List(Square(File.B, rank), Square(File.C, rank), Square(File.D, rank)).forall(s => board.pieceAt(s).isEmpty) &&
!List(Square(File.D, rank), Square(File.C, rank)).exists(s => isAttackedBy(board, s, enemy))
)(Square(File.C, rank))
kingsideSq.toSet ++ queensideSq.toSet
def legalTargets(board: Board, history: GameHistory, from: Square): Set[Square] =
board.pieceAt(from) match
case Some(piece) if piece.pieceType == PieceType.King =>
legalTargets(board, from) ++ castlingTargets(board, history, piece.color)
case Some(piece) if piece.pieceType == PieceType.Pawn =>
pawnTargets(board, history, from, piece.color)
case _ =>
legalTargets(board, from)
private def pawnTargets(board: Board, history: GameHistory, from: Square, color: Color): Set[Square] =
val existing = pawnTargets(board, from, color)
val fi = from.file.ordinal
val ri = from.rank.ordinal
val dir = if color == Color.White then 1 else -1
val epCapture: Set[Square] =
EnPassantCalculator.enPassantTarget(board, history).filter: target =>
squareAt(fi - 1, ri + dir).contains(target) || squareAt(fi + 1, ri + dir).contains(target)
.toSet
existing ++ epCapture
def isLegal(board: Board, history: GameHistory, from: Square, to: Square): Boolean =
legalTargets(board, history, from).contains(to)
/** Returns true if the piece on `from` is a pawn moving to its back rank (promotion). */
def isPromotionMove(board: Board, from: Square, to: Square): Boolean =
board.pieceAt(from) match
case Some(Piece(_, PieceType.Pawn)) =>
(from.rank == Rank.R7 && to.rank == Rank.R8) ||
(from.rank == Rank.R2 && to.rank == Rank.R1)
case _ => false
@@ -1,60 +0,0 @@
package de.nowchess.chess.notation
import de.nowchess.api.board.*
import de.nowchess.api.game.{CastlingRights, GameState}
import de.nowchess.api.board.Color
object FenExporter:
/** Convert a Board to FEN piece-placement string (rank 8 to rank 1, separated by '/'). */
def boardToFen(board: Board): String =
Rank.values.reverse
.map(rank => buildRankString(board, rank))
.mkString("/")
/** Build the FEN representation for a single rank. */
private def buildRankString(board: Board, rank: Rank): String =
val rankSquares = File.values.map(file => Square(file, rank))
val rankChars = scala.collection.mutable.ListBuffer[Char]()
var emptyCount = 0
for square <- rankSquares do
board.pieceAt(square) match
case Some(piece) =>
if emptyCount > 0 then
rankChars += emptyCount.toString.charAt(0)
emptyCount = 0
rankChars += pieceToPgnChar(piece)
case None =>
emptyCount += 1
if emptyCount > 0 then rankChars += emptyCount.toString.charAt(0)
rankChars.mkString
/** Convert a GameState to a complete FEN string. */
def gameStateToFen(state: GameState): String =
val piecePlacement = state.piecePlacement
val activeColor = if state.activeColor == Color.White then "w" else "b"
val castling = castlingString(state.castlingWhite, state.castlingBlack)
val enPassant = state.enPassantTarget.map(_.toString).getOrElse("-")
s"$piecePlacement $activeColor $castling $enPassant ${state.halfMoveClock} ${state.fullMoveNumber}"
/** Convert castling rights to FEN notation. */
private def castlingString(white: CastlingRights, black: CastlingRights): String =
val wk = if white.kingSide then "K" else ""
val wq = if white.queenSide then "Q" else ""
val bk = if black.kingSide then "k" else ""
val bq = if black.queenSide then "q" else ""
val result = s"$wk$wq$bk$bq"
if result.isEmpty then "-" else result
/** Convert a Piece to its FEN character (uppercase = White, lowercase = Black). */
private def pieceToPgnChar(piece: Piece): Char =
val base = piece.pieceType match
case PieceType.Pawn => 'p'
case PieceType.Knight => 'n'
case PieceType.Bishop => 'b'
case PieceType.Rook => 'r'
case PieceType.Queen => 'q'
case PieceType.King => 'k'
if piece.color == Color.White then base.toUpper else base
@@ -1,103 +0,0 @@
package de.nowchess.chess.notation
import de.nowchess.api.board.*
import de.nowchess.api.game.{CastlingRights, GameState, GameStatus}
object FenParser:
/** Parse a complete FEN string into a GameState.
* Returns None if the format is invalid. */
def parseFen(fen: String): Option[GameState] =
val parts = fen.trim.split("\\s+")
Option.when(parts.length == 6)(parts).flatMap: parts =>
for
_ <- parseBoard(parts(0))
activeColor <- parseColor(parts(1))
castlingRights <- parseCastling(parts(2))
enPassant <- parseEnPassant(parts(3))
halfMoveClock <- parts(4).toIntOption
fullMoveNumber <- parts(5).toIntOption
if halfMoveClock >= 0 && fullMoveNumber >= 1
yield GameState(
piecePlacement = parts(0),
activeColor = activeColor,
castlingWhite = castlingRights._1,
castlingBlack = castlingRights._2,
enPassantTarget = enPassant,
halfMoveClock = halfMoveClock,
fullMoveNumber = fullMoveNumber,
status = GameStatus.InProgress
)
/** Parse active color ("w" or "b"). */
private def parseColor(s: String): Option[Color] =
if s == "w" then Some(Color.White)
else if s == "b" then Some(Color.Black)
else None
/** Parse castling rights string (e.g. "KQkq", "K", "-") into rights for White and Black. */
private def parseCastling(s: String): Option[(CastlingRights, CastlingRights)] =
if s == "-" then
Some((CastlingRights.None, CastlingRights.None))
else if s.length <= 4 && s.forall(c => "KQkq".contains(c)) then
val white = CastlingRights(kingSide = s.contains('K'), queenSide = s.contains('Q'))
val black = CastlingRights(kingSide = s.contains('k'), queenSide = s.contains('q'))
Some((white, black))
else
None
/** Parse en passant target square ("-" for none, or algebraic like "e3"). */
private def parseEnPassant(s: String): Option[Option[Square]] =
if s == "-" then Some(None)
else Square.fromAlgebraic(s).map(Some(_))
/** Parses a FEN piece-placement string (rank 8 to rank 1, separated by '/') into a Board.
* Returns None if the format is invalid. */
def parseBoard(fen: String): Option[Board] =
val rankStrings = fen.split("/", -1)
if rankStrings.length != 8 then None
else
// Parse each rank, collecting all (Square, Piece) pairs or failing on the first error
val parsedRanks: Option[List[List[(Square, Piece)]]] =
rankStrings.zipWithIndex.foldLeft(Option(List.empty[List[(Square, Piece)]])):
case (None, _) => None
case (Some(acc), (rankStr, rankIdx)) =>
val rank = Rank.values(7 - rankIdx) // ranks go 8→1, so reverse
parsePieceRank(rankStr, rank).map(squares => acc :+ squares)
parsedRanks.map(ranks => Board(ranks.flatten.toMap))
/** Parse a single rank string (e.g. "rnbqkbnr" or "p3p3") into a list of (Square, Piece) pairs.
* Returns None if the rank string contains invalid characters or the wrong number of files. */
private def parsePieceRank(rankStr: String, rank: Rank): Option[List[(Square, Piece)]] =
var fileIdx = 0
val squares = scala.collection.mutable.ListBuffer[(Square, Piece)]()
var failed = false
for c <- rankStr if !failed do
if fileIdx > 7 then
failed = true
else if c.isDigit then
fileIdx += c.asDigit
else
charToPiece(c) match
case None => failed = true
case Some(piece) =>
val file = File.values(fileIdx)
squares += (Square(file, rank) -> piece)
fileIdx += 1
if failed || fileIdx != 8 then None
else Some(squares.toList)
/** Convert a FEN piece character to a Piece. Uppercase = White, lowercase = Black. */
private def charToPiece(c: Char): Option[Piece] =
val color = if Character.isUpperCase(c) then Color.White else Color.Black
val pieceTypeOpt = c.toLower match
case 'p' => Some(PieceType.Pawn)
case 'n' => Some(PieceType.Knight)
case 'b' => Some(PieceType.Bishop)
case 'r' => Some(PieceType.Rook)
case 'q' => Some(PieceType.Queen)
case 'k' => Some(PieceType.King)
case _ => None
pieceTypeOpt.map(pt => Piece(color, pt))
@@ -1,54 +0,0 @@
package de.nowchess.chess.notation
import de.nowchess.api.board.{PieceType, *}
import de.nowchess.api.move.PromotionPiece
import de.nowchess.chess.logic.{CastleSide, GameHistory, HistoryMove}
object PgnExporter:
/** Export a game with headers and history to PGN format. */
def exportGame(headers: Map[String, String], history: GameHistory): String =
val headerLines = headers.map { case (key, value) =>
s"""[$key "$value"]"""
}.mkString("\n")
val moveText = if history.moves.isEmpty then ""
else
val groupedMoves = history.moves.zipWithIndex.groupBy(_._2 / 2)
val moveLines = for (moveNumber, movePairs) <- groupedMoves.toList.sortBy(_._1) yield
val moveNum = moveNumber + 1
val whiteMoveStr = movePairs.find(_._2 % 2 == 0).map(p => moveToAlgebraic(p._1)).getOrElse("")
val blackMoveStr = movePairs.find(_._2 % 2 == 1).map(p => moveToAlgebraic(p._1)).getOrElse("")
if blackMoveStr.isEmpty then s"$moveNum. $whiteMoveStr"
else s"$moveNum. $whiteMoveStr $blackMoveStr"
val termination = headers.getOrElse("Result", "*")
moveLines.mkString(" ") + s" $termination"
if headerLines.isEmpty then moveText
else if moveText.isEmpty then headerLines
else s"$headerLines\n\n$moveText"
/** Convert a HistoryMove to Standard Algebraic Notation. */
def moveToAlgebraic(move: HistoryMove): String =
move.castleSide match
case Some(CastleSide.Kingside) => "O-O"
case Some(CastleSide.Queenside) => "O-O-O"
case None =>
val dest = move.to.toString
val capStr = if move.isCapture then "x" else ""
val promSuffix = move.promotionPiece match
case Some(PromotionPiece.Queen) => "=Q"
case Some(PromotionPiece.Rook) => "=R"
case Some(PromotionPiece.Bishop) => "=B"
case Some(PromotionPiece.Knight) => "=N"
case None => ""
move.pieceType match
case PieceType.Pawn =>
if move.isCapture then s"${move.from.file.toString.toLowerCase}x$dest$promSuffix"
else s"$dest$promSuffix"
case PieceType.Knight => s"N$capStr$dest$promSuffix"
case PieceType.Bishop => s"B$capStr$dest$promSuffix"
case PieceType.Rook => s"R$capStr$dest$promSuffix"
case PieceType.Queen => s"Q$capStr$dest$promSuffix"
case PieceType.King => s"K$capStr$dest$promSuffix"
@@ -1,267 +0,0 @@
package de.nowchess.chess.notation
import de.nowchess.api.board.*
import de.nowchess.api.move.PromotionPiece
import de.nowchess.chess.logic.{CastleSide, GameHistory, HistoryMove, GameRules, MoveValidator, withCastle}
/** A parsed PGN game containing headers and the resolved move list. */
case class PgnGame(
headers: Map[String, String],
moves: List[HistoryMove]
)
object PgnParser:
/** Strictly validate a PGN text.
* Returns Right(PgnGame) if every move token is a legal move in the evolving position.
* Returns Left(error message) on the first illegal or impossible move, or any unrecognised token. */
def validatePgn(pgn: String): Either[String, PgnGame] =
val lines = pgn.split("\n").map(_.trim)
val (headerLines, rest) = lines.span(_.startsWith("["))
val headers = parseHeaders(headerLines)
val moveText = rest.mkString(" ")
validateMovesText(moveText).map(moves => PgnGame(headers, moves))
/** Parse a complete PGN text into a PgnGame with headers and moves.
* Always succeeds (returns Some); malformed tokens are silently skipped. */
def parsePgn(pgn: String): Option[PgnGame] =
val lines = pgn.split("\n").map(_.trim)
val (headerLines, rest) = lines.span(_.startsWith("["))
val headers = parseHeaders(headerLines)
val moveText = rest.mkString(" ")
val moves = parseMovesText(moveText)
Some(PgnGame(headers, moves))
/** Parse PGN header lines of the form [Key "Value"]. */
private def parseHeaders(lines: Array[String]): Map[String, String] =
val pattern = """^\[(\w+)\s+"([^"]*)"\s*\]$""".r
lines.flatMap(line => pattern.findFirstMatchIn(line).map(m => m.group(1) -> m.group(2))).toMap
/** Parse the move-text section (e.g. "1. e4 e5 2. Nf3") into resolved HistoryMoves. */
private def parseMovesText(moveText: String): List[HistoryMove] =
val tokens = moveText.split("\\s+").filter(_.nonEmpty)
// Fold over tokens, threading (board, history, currentColor, accumulator)
val (_, _, _, moves) = tokens.foldLeft(
(Board.initial, GameHistory.empty, Color.White, List.empty[HistoryMove])
):
case (state @ (board, history, color, acc), token) =>
// Skip move-number markers (e.g. "1.", "2.") and result tokens
if isMoveNumberOrResult(token) then state
else
parseAlgebraicMove(token, board, history, color) match
case None => state // unrecognised token — skip silently
case Some(move) =>
val newBoard = applyMoveToBoard(board, move, color)
val newHistory = history.addMove(move)
(newBoard, newHistory, color.opposite, acc :+ move)
moves
/** Apply a single HistoryMove to a Board, handling castling and promotion. */
private def applyMoveToBoard(board: Board, move: HistoryMove, color: Color): Board =
move.castleSide match
case Some(side) => board.withCastle(color, side)
case None =>
val (boardAfterMove, _) = board.withMove(move.from, move.to)
move.promotionPiece match
case Some(pp) =>
val pieceType = pp match
case PromotionPiece.Queen => PieceType.Queen
case PromotionPiece.Rook => PieceType.Rook
case PromotionPiece.Bishop => PieceType.Bishop
case PromotionPiece.Knight => PieceType.Knight
boardAfterMove.updated(move.to, Piece(color, pieceType))
case None => boardAfterMove
/** True for move-number tokens ("1.", "12.") and PGN result tokens. */
private def isMoveNumberOrResult(token: String): Boolean =
token.matches("""\d+\.""") ||
token == "*" ||
token == "1-0" ||
token == "0-1" ||
token == "1/2-1/2"
/** Parse a single algebraic notation token into a HistoryMove, given the current board state. */
def parseAlgebraicMove(notation: String, board: Board, history: GameHistory, color: Color): Option[HistoryMove] =
notation match
case "O-O" | "O-O+" | "O-O#" =>
val rank = if color == Color.White then Rank.R1 else Rank.R8
Some(HistoryMove(Square(File.E, rank), Square(File.G, rank), Some(CastleSide.Kingside), pieceType = PieceType.King))
case "O-O-O" | "O-O-O+" | "O-O-O#" =>
val rank = if color == Color.White then Rank.R1 else Rank.R8
Some(HistoryMove(Square(File.E, rank), Square(File.C, rank), Some(CastleSide.Queenside), pieceType = PieceType.King))
case _ =>
parseRegularMove(notation, board, history, color)
/** Parse regular algebraic notation (pawn moves, piece moves, captures, disambiguation). */
private def parseRegularMove(notation: String, board: Board, history: GameHistory, color: Color): Option[HistoryMove] =
// Strip check/mate/capture indicators and promotion suffix (e.g. =Q)
val clean = notation
.replace("+", "")
.replace("#", "")
.replace("x", "")
.replaceAll("=[NBRQ]$", "")
// The destination square is always the last two characters
if clean.length < 2 then None
else
val destStr = clean.takeRight(2)
Square.fromAlgebraic(destStr).flatMap: toSquare =>
val disambig = clean.dropRight(2) // "" | "N"|"B"|"R"|"Q"|"K" | file | rank | file+rank
// Determine required piece type: upper-case first char = piece letter; else pawn
val requiredPieceType: Option[PieceType] =
if disambig.nonEmpty && disambig.head.isUpper then charToPieceType(disambig.head)
else if clean.head.isUpper then charToPieceType(clean.head)
else Some(PieceType.Pawn)
// Collect the disambiguation hint that remains after stripping the piece letter
val hint =
if disambig.nonEmpty && disambig.head.isUpper then disambig.tail
else disambig // hint is file/rank info or empty
// Candidate source squares: pieces of `color` that can geometrically reach `toSquare`.
// We prefer pieces that can actually reach the target; if none can (positionally illegal
// PGN input), fall back to any piece of the matching type belonging to `color`.
val reachable: Set[Square] =
board.pieces.collect {
case (from, piece) if piece.color == color &&
MoveValidator.legalTargets(board, from).contains(toSquare) => from
}.toSet
val candidates: Set[Square] =
if reachable.nonEmpty then reachable
else
// Fallback for positionally-illegal but syntactically valid PGN notation:
// find any piece of `color` with the correct piece type on the board.
board.pieces.collect {
case (from, piece) if piece.color == color => from
}.toSet
// Filter by required piece type
val byPiece = candidates.filter(from =>
requiredPieceType.forall(pt => board.pieceAt(from).exists(_.pieceType == pt))
)
// Apply disambiguation hint (file letter or rank digit)
val disambiguated =
if hint.isEmpty then byPiece
else byPiece.filter(from => matchesHint(from, hint))
val promotion = extractPromotion(notation)
val movePieceType = requiredPieceType.getOrElse(PieceType.Pawn)
val moveIsCapture = notation.contains('x')
disambiguated.headOption.map(from => HistoryMove(from, toSquare, None, promotion, movePieceType, moveIsCapture))
/** True if `sq` matches a disambiguation hint (file letter, rank digit, or both). */
private def matchesHint(sq: Square, hint: String): Boolean =
hint.forall(c => if c >= 'a' && c <= 'h' then sq.file.toString.equalsIgnoreCase(c.toString)
else if c >= '1' && c <= '8' then sq.rank.ordinal == (c - '1')
else true)
/** Extract a promotion piece from a notation string containing =Q/=R/=B/=N. */
private[notation] def extractPromotion(notation: String): Option[PromotionPiece] =
val promotionPattern = """=([A-Z])""".r
promotionPattern.findFirstMatchIn(notation).flatMap { m =>
m.group(1) match
case "Q" => Some(PromotionPiece.Queen)
case "R" => Some(PromotionPiece.Rook)
case "B" => Some(PromotionPiece.Bishop)
case "N" => Some(PromotionPiece.Knight)
case _ => None
}
/** Convert a piece-letter character to a PieceType. */
private def charToPieceType(c: Char): Option[PieceType] =
c match
case 'N' => Some(PieceType.Knight)
case 'B' => Some(PieceType.Bishop)
case 'R' => Some(PieceType.Rook)
case 'Q' => Some(PieceType.Queen)
case 'K' => Some(PieceType.King)
case _ => None
// ── Strict validation helpers ─────────────────────────────────────────────
/** Walk all move tokens, failing immediately on any unresolvable or illegal move. */
private def validateMovesText(moveText: String): Either[String, List[HistoryMove]] =
val tokens = moveText.split("\\s+").filter(_.nonEmpty)
tokens.foldLeft(Right((Board.initial, GameHistory.empty, Color.White, List.empty[HistoryMove])): Either[String, (Board, GameHistory, Color, List[HistoryMove])]) {
case (acc, token) =>
acc.flatMap { case (board, history, color, moves) =>
if isMoveNumberOrResult(token) then Right((board, history, color, moves))
else
strictParseAlgebraicMove(token, board, history, color) match
case None => Left(s"Illegal or impossible move: '$token'")
case Some(move) =>
val newBoard = applyMoveToBoard(board, move, color)
val newHistory = history.addMove(move)
Right((newBoard, newHistory, color.opposite, moves :+ move))
}
}.map(_._4)
/** Strict algebraic move parse — no fallback to positionally-illegal moves. */
private def strictParseAlgebraicMove(notation: String, board: Board, history: GameHistory, color: Color): Option[HistoryMove] =
val rank = if color == Color.White then Rank.R1 else Rank.R8
notation match
case "O-O" | "O-O+" | "O-O#" =>
val dest = Square(File.G, rank)
Option.when(MoveValidator.castlingTargets(board, history, color).contains(dest))(
HistoryMove(Square(File.E, rank), dest, Some(CastleSide.Kingside), pieceType = PieceType.King)
)
case "O-O-O" | "O-O-O+" | "O-O-O#" =>
val dest = Square(File.C, rank)
Option.when(MoveValidator.castlingTargets(board, history, color).contains(dest))(
HistoryMove(Square(File.E, rank), dest, Some(CastleSide.Queenside), pieceType = PieceType.King)
)
case _ =>
strictParseRegularMove(notation, board, history, color)
/** Strict regular move parse — uses only legally reachable squares, no fallback. */
private def strictParseRegularMove(notation: String, board: Board, history: GameHistory, color: Color): Option[HistoryMove] =
val clean = notation
.replace("+", "")
.replace("#", "")
.replace("x", "")
.replaceAll("=[NBRQ]$", "")
if clean.length < 2 then None
else
val destStr = clean.takeRight(2)
Square.fromAlgebraic(destStr).flatMap { toSquare =>
val disambig = clean.dropRight(2)
val requiredPieceType: Option[PieceType] =
if disambig.nonEmpty && disambig.head.isUpper then charToPieceType(disambig.head)
else if clean.head.isUpper then charToPieceType(clean.head)
else Some(PieceType.Pawn)
val hint =
if disambig.nonEmpty && disambig.head.isUpper then disambig.tail
else disambig
// Strict: only squares from which a legal move (including en passant/castling awareness) exists.
val reachable: Set[Square] =
board.pieces.collect {
case (from, piece) if piece.color == color &&
MoveValidator.legalTargets(board, history, from).contains(toSquare) => from
}.toSet
val byPiece = reachable.filter(from =>
requiredPieceType.forall(pt => board.pieceAt(from).exists(_.pieceType == pt))
)
val disambiguated =
if hint.isEmpty then byPiece
else byPiece.filter(from => matchesHint(from, hint))
val promotion = extractPromotion(notation)
val movePieceType = requiredPieceType.getOrElse(PieceType.Pawn)
val moveIsCapture = notation.contains('x')
disambiguated.headOption.map(from => HistoryMove(from, toSquare, None, promotion, movePieceType, moveIsCapture))
}
@@ -1,21 +1,17 @@
package de.nowchess.chess.observer
import de.nowchess.api.board.{Board, Color, Square}
import de.nowchess.chess.logic.GameHistory
import de.nowchess.api.board.{Color, Square}
import de.nowchess.api.game.GameContext
/** Base trait for all game state events.
* Events are immutable snapshots of game state changes.
*/
sealed trait GameEvent:
def board: Board
def history: GameHistory
def turn: Color
def context: GameContext
/** Fired when a move is successfully executed. */
case class MoveExecutedEvent(
board: Board,
history: GameHistory,
turn: Color,
context: GameContext,
fromSquare: String,
toSquare: String,
capturedPiece: Option[String]
@@ -23,77 +19,57 @@ case class MoveExecutedEvent(
/** Fired when the current player is in check. */
case class CheckDetectedEvent(
board: Board,
history: GameHistory,
turn: Color
context: GameContext
) extends GameEvent
/** Fired when the game reaches checkmate. */
case class CheckmateEvent(
board: Board,
history: GameHistory,
turn: Color,
context: GameContext,
winner: Color
) extends GameEvent
/** Fired when the game reaches stalemate. */
case class StalemateEvent(
board: Board,
history: GameHistory,
turn: Color
context: GameContext
) extends GameEvent
/** Fired when a move is invalid. */
case class InvalidMoveEvent(
board: Board,
history: GameHistory,
turn: Color,
context: GameContext,
reason: String
) extends GameEvent
/** Fired when a pawn reaches the back rank and the player must choose a promotion piece. */
case class PromotionRequiredEvent(
board: Board,
history: GameHistory,
turn: Color,
context: GameContext,
from: Square,
to: Square
) extends GameEvent
/** Fired when the board is reset. */
case class BoardResetEvent(
board: Board,
history: GameHistory,
turn: Color
context: GameContext
) extends GameEvent
/** Fired after any move where the half-move clock reaches 100 — the 50-move rule is now claimable. */
case class FiftyMoveRuleAvailableEvent(
board: Board,
history: GameHistory,
turn: Color
context: GameContext
) extends GameEvent
/** Fired when a player successfully claims a draw under the 50-move rule. */
case class DrawClaimedEvent(
board: Board,
history: GameHistory,
turn: Color
context: GameContext
) extends GameEvent
/** Fired when a move is undone, carrying PGN notation of the reversed move. */
case class MoveUndoneEvent(
board: Board,
history: GameHistory,
turn: Color,
context: GameContext,
pgnNotation: String
) extends GameEvent
/** Fired when a previously undone move is redone, carrying PGN notation of the replayed move. */
case class MoveRedoneEvent(
board: Board,
history: GameHistory,
turn: Color,
context: GameContext,
pgnNotation: String,
fromSquare: String,
toSquare: String,
@@ -102,9 +78,7 @@ case class MoveRedoneEvent(
/** Fired after a PGN string is successfully loaded and all moves are replayed into history. */
case class PgnLoadedEvent(
board: Board,
history: GameHistory,
turn: Color
context: GameContext
) extends GameEvent
/** Observer trait: implement to receive game state updates. */
@@ -1,18 +0,0 @@
package de.nowchess.chess.view
import de.nowchess.api.board.{Color, Piece, PieceType}
extension (p: Piece)
def unicode: String = (p.color, p.pieceType) match
case (Color.White, PieceType.King) => "\u2654"
case (Color.White, PieceType.Queen) => "\u2655"
case (Color.White, PieceType.Rook) => "\u2656"
case (Color.White, PieceType.Bishop) => "\u2657"
case (Color.White, PieceType.Knight) => "\u2658"
case (Color.White, PieceType.Pawn) => "\u2659"
case (Color.Black, PieceType.King) => "\u265A"
case (Color.Black, PieceType.Queen) => "\u265B"
case (Color.Black, PieceType.Rook) => "\u265C"
case (Color.Black, PieceType.Bishop) => "\u265D"
case (Color.Black, PieceType.Knight) => "\u265E"
case (Color.Black, PieceType.Pawn) => "\u265F"
@@ -1,28 +0,0 @@
package de.nowchess.chess.view
import de.nowchess.api.board.{Board, Color, File, Rank, Square}
object Renderer:
private val AnsiReset = "\u001b[0m"
private val AnsiLightSquare = "\u001b[48;5;223m" // warm beige
private val AnsiDarkSquare = "\u001b[48;5;130m" // brown
private val AnsiWhitePiece = "\u001b[97m" // bright white text
private val AnsiBlackPiece = "\u001b[30m" // black text
def render(board: Board): String =
val rows = (0 until 8).reverse.map { rank =>
val cells = (0 until 8).map { file =>
val sq = Square(File.values(file), Rank.values(rank))
val isLightSq = (file + rank) % 2 != 0
val bgColor = if isLightSq then AnsiLightSquare else AnsiDarkSquare
board.pieceAt(sq) match
case Some(piece) =>
val fgColor = if piece.color == Color.White then AnsiWhitePiece else AnsiBlackPiece
s"$bgColor$fgColor ${piece.unicode} $AnsiReset"
case None =>
s"$bgColor $AnsiReset"
}.mkString
s"${rank + 1} $cells ${rank + 1}"
}.mkString("\n")
s" a b c d e f g h\n$rows\n a b c d e f g h\n"