feat: NCS-25 Add linters to keep quality up (#27)

Reviewed-on: #27
Reviewed-by: Leon Hermann <lq@blackhole.local>
Co-authored-by: Janis <janis.e.20@gmx.de>
Co-committed-by: Janis <janis.e.20@gmx.de>

modules/rule/src/main/scala/de/nowchess/rules/RuleSet.scala

@@ -4,9 +4,9 @@ import de.nowchess.api.game.GameContext
 import de.nowchess.api.board.Square
 import de.nowchess.api.move.Move
 
-/** Extension point for chess rule variants (standard, Chess960, etc.).
- *  All rule queries are stateless: given a GameContext, return the answer.
- */
+/** Extension point for chess rule variants (standard, Chess960, etc.). All rule queries are stateless: given a
+  * GameContext, return the answer.
+  */
 trait RuleSet:
   /** All pseudo-legal moves for the piece on `square` (ignores check). */
   def candidateMoves(context: GameContext)(square: Square): List[Move]
@@ -32,8 +32,7 @@ trait RuleSet:
   /** True if halfMoveClock >= 100 (50-move rule). */
   def isFiftyMoveRule(context: GameContext): Boolean
 
-  /** Apply a legal move to produce the next game context.
-   *  Handles all special move types: castling, en passant, promotion.
-   *  Updates castling rights, en passant square, half-move clock, turn, and move history.
-   */
+  /** Apply a legal move to produce the next game context. Handles all special move types: castling, en passant,
+    * promotion. Updates castling rights, en passant square, half-move clock, turn, and move history.
+    */
   def applyMove(context: GameContext)(move: Move): GameContext

modules/rule/src/main/scala/de/nowchess/rules/sets/DefaultRules.scala

@@ -7,20 +7,19 @@ import de.nowchess.rules.RuleSet
 
 import scala.annotation.tailrec
 
-/** Standard chess rules implementation.
- *  Handles move generation, validation, check/checkmate/stalemate detection.
- */
+/** Standard chess rules implementation. Handles move generation, validation, check/checkmate/stalemate detection.
+  */
 object DefaultRules extends RuleSet:
 
   // ── Direction vectors ──────────────────────────────────────────────
-  private val RookDirs: List[(Int, Int)] = List((1, 0), (-1, 0), (0, 1), (0, -1))
+  private val RookDirs: List[(Int, Int)]   = List((1, 0), (-1, 0), (0, 1), (0, -1))
   private val BishopDirs: List[(Int, Int)] = List((1, 1), (1, -1), (-1, 1), (-1, -1))
-  private val QueenDirs: List[(Int, Int)] = RookDirs ++ BishopDirs
+  private val QueenDirs: List[(Int, Int)]  = RookDirs ++ BishopDirs
   private val KnightJumps: List[(Int, Int)] =
     List((2, 1), (2, -1), (-2, 1), (-2, -1), (1, 2), (1, -2), (-1, 2), (-1, -2))
 
   // ── Pawn configuration helpers ─────────────────────────────────────
-  private def pawnForward(color: Color): Int = if color == Color.White then 1 else -1
+  private def pawnForward(color: Color): Int   = if color == Color.White then 1 else -1
   private def pawnStartRank(color: Color): Int = if color == Color.White then 1 else 6
   private def pawnPromoRank(color: Color): Int = if color == Color.White then 7 else 0
 
@@ -29,13 +28,14 @@ object DefaultRules extends RuleSet:
   override def candidateMoves(context: GameContext)(square: Square): List[Move] =
     context.board.pieceAt(square).fold(List.empty[Move]) { piece =>
       if piece.color != context.turn then List.empty[Move]
-      else piece.pieceType match
-        case PieceType.Pawn => pawnCandidates(context, square, piece.color)
-        case PieceType.Knight => knightCandidates(context, square, piece.color)
-        case PieceType.Bishop => slidingMoves(context, square, piece.color, BishopDirs)
-        case PieceType.Rook => slidingMoves(context, square, piece.color, RookDirs)
-        case PieceType.Queen => slidingMoves(context, square, piece.color, QueenDirs)
-        case PieceType.King => kingCandidates(context, square, piece.color)
+      else
+        piece.pieceType match
+          case PieceType.Pawn   => pawnCandidates(context, square, piece.color)
+          case PieceType.Knight => knightCandidates(context, square, piece.color)
+          case PieceType.Bishop => slidingMoves(context, square, piece.color, BishopDirs)
+          case PieceType.Rook   => slidingMoves(context, square, piece.color, RookDirs)
+          case PieceType.Queen  => slidingMoves(context, square, piece.color, QueenDirs)
+          case PieceType.King   => kingCandidates(context, square, piece.color)
     }
 
   override def legalMoves(context: GameContext)(square: Square): List[Move] =
@@ -65,18 +65,18 @@ object DefaultRules extends RuleSet:
   // ── Sliding pieces (Bishop, Rook, Queen) ───────────────────────────
 
   private def slidingMoves(
-    context: GameContext,
-    from: Square,
-    color: Color,
-    dirs: List[(Int, Int)]
+      context: GameContext,
+      from: Square,
+      color: Color,
+      dirs: List[(Int, Int)],
   ): List[Move] =
     dirs.flatMap(dir => castRay(context.board, from, color, dir))
 
   private def castRay(
-    board: Board,
-    from: Square,
-    color: Color,
-    dir: (Int, Int)
+      board: Board,
+      from: Square,
+      color: Color,
+      dir: (Int, Int),
   ): List[Move] =
     @tailrec
     def loop(sq: Square, acc: List[Move]): List[Move] =
@@ -84,40 +84,40 @@ object DefaultRules extends RuleSet:
         case None => acc
         case Some(next) =>
           board.pieceAt(next) match
-            case None => loop(next, Move(from, next) :: acc)
+            case None                        => loop(next, Move(from, next) :: acc)
             case Some(p) if p.color != color => Move(from, next, MoveType.Normal(isCapture = true)) :: acc
-            case Some(_) => acc
+            case Some(_)                     => acc
     loop(from, Nil).reverse
 
   // ── Knight ─────────────────────────────────────────────────────────
 
   private def knightCandidates(
-    context: GameContext,
-    from: Square,
-    color: Color
+      context: GameContext,
+      from: Square,
+      color: Color,
   ): List[Move] =
     KnightJumps.flatMap { (df, dr) =>
       from.offset(df, dr).flatMap { to =>
         context.board.pieceAt(to) match
           case Some(p) if p.color == color => None
-          case Some(_) => Some(Move(from, to, MoveType.Normal(isCapture = true)))
-          case None    => Some(Move(from, to))
+          case Some(_)                     => Some(Move(from, to, MoveType.Normal(isCapture = true)))
+          case None                        => Some(Move(from, to))
       }
     }
 
   // ── King ───────────────────────────────────────────────────────────
 
   private def kingCandidates(
-    context: GameContext,
-    from: Square,
-    color: Color
+      context: GameContext,
+      from: Square,
+      color: Color,
   ): List[Move] =
     val steps = QueenDirs.flatMap { (df, dr) =>
       from.offset(df, dr).flatMap { to =>
         context.board.pieceAt(to) match
           case Some(p) if p.color == color => None
-          case Some(_) => Some(Move(from, to, MoveType.Normal(isCapture = true)))
-          case None    => Some(Move(from, to))
+          case Some(_)                     => Some(Move(from, to, MoveType.Normal(isCapture = true)))
+          case None                        => Some(Move(from, to))
       }
     }
     steps ++ castlingCandidates(context, from, color)
@@ -125,17 +125,17 @@ object DefaultRules extends RuleSet:
   // ── Castling ───────────────────────────────────────────────────────
 
   private case class CastlingMove(
-    kingFromAlg: String,
-    kingToAlg: String,
-    middleAlg: String,
-    rookFromAlg: String,
-    moveType: MoveType
+      kingFromAlg: String,
+      kingToAlg: String,
+      middleAlg: String,
+      rookFromAlg: String,
+      moveType: MoveType,
   )
 
   private def castlingCandidates(
-    context: GameContext,
-    from: Square,
-    color: Color
+      context: GameContext,
+      from: Square,
+      color: Color,
   ): List[Move] =
     color match
       case Color.White => whiteCastles(context, from)
@@ -146,10 +146,18 @@ object DefaultRules extends RuleSet:
     if from != expected then List.empty
     else
       val moves = scala.collection.mutable.ListBuffer[Move]()
-      addCastleMove(context, moves, context.castlingRights.whiteKingSide,
-        CastlingMove("e1", "g1", "f1", "h1", MoveType.CastleKingside))
-      addCastleMove(context, moves, context.castlingRights.whiteQueenSide,
-        CastlingMove("e1", "c1", "d1", "a1", MoveType.CastleQueenside))
+      addCastleMove(
+        context,
+        moves,
+        context.castlingRights.whiteKingSide,
+        CastlingMove("e1", "g1", "f1", "h1", MoveType.CastleKingside),
+      )
+      addCastleMove(
+        context,
+        moves,
+        context.castlingRights.whiteQueenSide,
+        CastlingMove("e1", "c1", "d1", "a1", MoveType.CastleQueenside),
+      )
       moves.toList
 
   private def blackCastles(context: GameContext, from: Square): List[Move] =
@@ -157,10 +165,18 @@ object DefaultRules extends RuleSet:
     if from != expected then List.empty
     else
       val moves = scala.collection.mutable.ListBuffer[Move]()
-      addCastleMove(context, moves, context.castlingRights.blackKingSide,
-        CastlingMove("e8", "g8", "f8", "h8", MoveType.CastleKingside))
-      addCastleMove(context, moves, context.castlingRights.blackQueenSide,
-        CastlingMove("e8", "c8", "d8", "a8", MoveType.CastleQueenside))
+      addCastleMove(
+        context,
+        moves,
+        context.castlingRights.blackKingSide,
+        CastlingMove("e8", "g8", "f8", "h8", MoveType.CastleKingside),
+      )
+      addCastleMove(
+        context,
+        moves,
+        context.castlingRights.blackQueenSide,
+        CastlingMove("e8", "c8", "d8", "a8", MoveType.CastleQueenside),
+      )
       moves.toList
 
   private def queensideBSquare(kingToAlg: String): List[String] =
@@ -170,10 +186,10 @@ object DefaultRules extends RuleSet:
       case _    => List.empty
 
   private def addCastleMove(
-    context: GameContext,
-    moves: scala.collection.mutable.ListBuffer[Move],
-    castlingRight: Boolean,
-    castlingMove: CastlingMove
+      context: GameContext,
+      moves: scala.collection.mutable.ListBuffer[Move],
+      castlingRight: Boolean,
+      castlingMove: CastlingMove,
   ): Unit =
     if castlingRight then
       val clearSqs = (List(castlingMove.middleAlg, castlingMove.kingToAlg) ++ queensideBSquare(castlingMove.kingToAlg))
@@ -185,16 +201,15 @@ object DefaultRules extends RuleSet:
           kt <- Square.fromAlgebraic(castlingMove.kingToAlg)
           rf <- Square.fromAlgebraic(castlingMove.rookFromAlg)
         do
-          val color = context.turn
+          val color       = context.turn
           val kingPresent = context.board.pieceAt(kf).exists(p => p.color == color && p.pieceType == PieceType.King)
           val rookPresent = context.board.pieceAt(rf).exists(p => p.color == color && p.pieceType == PieceType.Rook)
           val squaresSafe =
             !isAttackedBy(context.board, kf, color.opposite) &&
-            !isAttackedBy(context.board, km, color.opposite) &&
-            !isAttackedBy(context.board, kt, color.opposite)
+              !isAttackedBy(context.board, km, color.opposite) &&
+              !isAttackedBy(context.board, kt, color.opposite)
 
-          if kingPresent && rookPresent && squaresSafe then
-            moves += Move(kf, kt, castlingMove.moveType)
+          if kingPresent && rookPresent && squaresSafe then moves += Move(kf, kt, castlingMove.moveType)
 
   private def squaresEmpty(board: Board, squares: List[Square]): Boolean =
     squares.forall(sq => board.pieceAt(sq).isEmpty)
@@ -202,22 +217,26 @@ object DefaultRules extends RuleSet:
   // ── Pawn ───────────────────────────────────────────────────────────
 
   private def pawnCandidates(
-    context: GameContext,
-    from: Square,
-    color: Color
+      context: GameContext,
+      from: Square,
+      color: Color,
   ): List[Move] =
-    val fwd = pawnForward(color)
+    val fwd       = pawnForward(color)
     val startRank = pawnStartRank(color)
     val promoRank = pawnPromoRank(color)
 
     val single = from.offset(0, fwd).filter(to => context.board.pieceAt(to).isEmpty)
-    val double = Option.when(from.rank.ordinal == startRank) {
-      from.offset(0, fwd).flatMap { mid =>
-        Option.when(context.board.pieceAt(mid).isEmpty) {
-          from.offset(0, fwd * 2).filter(to => context.board.pieceAt(to).isEmpty)
-        }.flatten
+    val double = Option
+      .when(from.rank.ordinal == startRank) {
+        from.offset(0, fwd).flatMap { mid =>
+          Option
+            .when(context.board.pieceAt(mid).isEmpty) {
+              from.offset(0, fwd * 2).filter(to => context.board.pieceAt(to).isEmpty)
+            }
+            .flatten
+        }
       }
-    }.flatten
+      .flatten
 
     val diagonalCaptures = List(-1, 1).flatMap { df =>
       from.offset(df, fwd).flatMap { to =>
@@ -236,22 +255,22 @@ object DefaultRules extends RuleSet:
     def toMoves(dest: Square, isCapture: Boolean): List[Move] =
       if dest.rank.ordinal == promoRank then
         List(
-          PromotionPiece.Queen, PromotionPiece.Rook,
-          PromotionPiece.Bishop, PromotionPiece.Knight
+          PromotionPiece.Queen,
+          PromotionPiece.Rook,
+          PromotionPiece.Bishop,
+          PromotionPiece.Knight,
         ).map(pt => Move(from, dest, MoveType.Promotion(pt)))
       else List(Move(from, dest, MoveType.Normal(isCapture = isCapture)))
 
-    val stepSquares = single.toList ++ double.toList
-    val stepMoves = stepSquares.flatMap(dest => toMoves(dest, isCapture = false))
+    val stepSquares  = single.toList ++ double.toList
+    val stepMoves    = stepSquares.flatMap(dest => toMoves(dest, isCapture = false))
     val captureMoves = diagonalCaptures.flatMap(dest => toMoves(dest, isCapture = true))
     stepMoves ++ captureMoves ++ epCaptures
 
   // ── Check detection ────────────────────────────────────────────────
 
   private def kingSquare(board: Board, color: Color): Option[Square] =
-    Square.all.find(sq =>
-      board.pieceAt(sq).exists(p => p.color == color && p.pieceType == PieceType.King)
-    )
+    Square.all.find(sq => board.pieceAt(sq).exists(p => p.color == color && p.pieceType == PieceType.King))
 
   private def isAttackedBy(board: Board, target: Square, attacker: Color): Boolean =
     Square.all.exists { sq =>
@@ -266,26 +285,26 @@ object DefaultRules extends RuleSet:
       case PieceType.Pawn =>
         from.offset(-1, fwd).contains(target) || from.offset(1, fwd).contains(target)
       case PieceType.Knight =>
-        KnightJumps.exists { (df, dr) => from.offset(df, dr).contains(target) }
+        KnightJumps.exists((df, dr) => from.offset(df, dr).contains(target))
       case PieceType.Bishop => rayReaches(board, from, BishopDirs, target)
-      case PieceType.Rook => rayReaches(board, from, RookDirs, target)
-      case PieceType.Queen => rayReaches(board, from, QueenDirs, target)
+      case PieceType.Rook   => rayReaches(board, from, RookDirs, target)
+      case PieceType.Queen  => rayReaches(board, from, QueenDirs, target)
       case PieceType.King =>
-        QueenDirs.exists { (df, dr) => from.offset(df, dr).contains(target) }
+        QueenDirs.exists((df, dr) => from.offset(df, dr).contains(target))
 
   private def rayReaches(board: Board, from: Square, dirs: List[(Int, Int)], target: Square): Boolean =
     dirs.exists { dir =>
       @tailrec
       def loop(sq: Square): Boolean = sq.offset(dir._1, dir._2) match
-        case None => false
-        case Some(next) if next == target => true
+        case None                                      => false
+        case Some(next) if next == target              => true
         case Some(next) if board.pieceAt(next).isEmpty => loop(next)
-        case Some(_) => false
+        case Some(_)                                   => false
       loop(from)
     }
 
   private def leavesKingInCheck(context: GameContext, move: Move): Boolean =
-    val nextBoard = context.board.applyMove(move)
+    val nextBoard   = context.board.applyMove(move)
     val nextContext = context.withBoard(nextBoard)
     isCheck(nextContext)
 
@@ -293,7 +312,7 @@ object DefaultRules extends RuleSet:
 
   override def applyMove(context: GameContext)(move: Move): GameContext =
     val color = context.turn
-    val board  = context.board
+    val board = context.board
 
     val newBoard = move.moveType match
       case MoveType.CastleKingside  => applyCastle(board, color, kingside = true)
@@ -302,14 +321,14 @@ object DefaultRules extends RuleSet:
       case MoveType.Promotion(pp)   => applyPromotion(board, move, color, pp)
       case MoveType.Normal(_)       => board.applyMove(move)
 
-    val newCastlingRights = updateCastlingRights(context.castlingRights, board, move, color)
+    val newCastlingRights  = updateCastlingRights(context.castlingRights, board, move, color)
     val newEnPassantSquare = computeEnPassantSquare(board, move)
     val isCapture = move.moveType match
       case MoveType.Normal(capture) => capture
       case MoveType.EnPassant       => true
       case _                        => board.pieceAt(move.to).isDefined
     val isPawnMove = board.pieceAt(move.from).exists(_.pieceType == PieceType.Pawn)
-    val newClock = if isPawnMove || isCapture then 0 else context.halfMoveClock + 1
+    val newClock   = if isPawnMove || isCapture then 0 else context.halfMoveClock + 1
 
     context
       .withBoard(newBoard)
@@ -322,19 +341,18 @@ object DefaultRules extends RuleSet:
   private def applyCastle(board: Board, color: Color, kingside: Boolean): Board =
     val rank = if color == Color.White then Rank.R1 else Rank.R8
     val (kingFrom, kingTo, rookFrom, rookTo) =
-      if kingside then
-        (Square(File.E, rank), Square(File.G, rank), Square(File.H, rank), Square(File.F, rank))
-      else
-        (Square(File.E, rank), Square(File.C, rank), Square(File.A, rank), Square(File.D, rank))
+      if kingside then (Square(File.E, rank), Square(File.G, rank), Square(File.H, rank), Square(File.F, rank))
+      else (Square(File.E, rank), Square(File.C, rank), Square(File.A, rank), Square(File.D, rank))
     val king = board.pieceAt(kingFrom).getOrElse(Piece(color, PieceType.King))
     val rook = board.pieceAt(rookFrom).getOrElse(Piece(color, PieceType.Rook))
     board
-      .removed(kingFrom).removed(rookFrom)
+      .removed(kingFrom)
+      .removed(rookFrom)
       .updated(kingTo, king)
       .updated(rookTo, rook)
 
   private def applyEnPassant(board: Board, move: Move): Board =
-    val capturedRank = move.from.rank  // the captured pawn is on the same rank as the moving pawn
+    val capturedRank   = move.from.rank // the captured pawn is on the same rank as the moving pawn
     val capturedSquare = Square(move.to.file, capturedRank)
     board.applyMove(move).removed(capturedSquare)
 
@@ -347,7 +365,7 @@ object DefaultRules extends RuleSet:
     board.removed(move.from).updated(move.to, Piece(color, promotedType))
 
   private def updateCastlingRights(rights: CastlingRights, board: Board, move: Move, color: Color): CastlingRights =
-    val piece = board.pieceAt(move.from)
+    val piece      = board.pieceAt(move.from)
     val isKingMove = piece.exists(_.pieceType == PieceType.King)
     val isRookMove = piece.exists(_.pieceType == PieceType.Rook)
 
@@ -360,14 +378,14 @@ object DefaultRules extends RuleSet:
     var r = rights
     if isKingMove then r = r.revokeColor(color)
     else if isRookMove then
-      if move.from == whiteKingsideRook  then r = r.revokeKingSide(Color.White)
+      if move.from == whiteKingsideRook then r = r.revokeKingSide(Color.White)
       if move.from == whiteQueensideRook then r = r.revokeQueenSide(Color.White)
-      if move.from == blackKingsideRook  then r = r.revokeKingSide(Color.Black)
+      if move.from == blackKingsideRook then r = r.revokeKingSide(Color.Black)
       if move.from == blackQueensideRook then r = r.revokeQueenSide(Color.Black)
     // Also revoke if a rook is captured
-    if move.to == whiteKingsideRook  then r = r.revokeKingSide(Color.White)
+    if move.to == whiteKingsideRook then r = r.revokeKingSide(Color.White)
     if move.to == whiteQueensideRook then r = r.revokeQueenSide(Color.White)
-    if move.to == blackKingsideRook  then r = r.revokeKingSide(Color.Black)
+    if move.to == blackKingsideRook then r = r.revokeKingSide(Color.Black)
     if move.to == blackQueensideRook then r = r.revokeQueenSide(Color.Black)
     r
 
@@ -386,9 +404,10 @@ object DefaultRules extends RuleSet:
   private def insufficientMaterial(board: Board): Boolean =
     val pieces = board.pieces.values.toList.filter(_.pieceType != PieceType.King)
     pieces match
-      case Nil => true
+      case Nil                                                                           => true
       case List(p) if p.pieceType == PieceType.Bishop || p.pieceType == PieceType.Knight => true
       case List(p1, p2)
-        if p1.pieceType == PieceType.Bishop && p2.pieceType == PieceType.Bishop
-           && p1.color != p2.color => true
+          if p1.pieceType == PieceType.Bishop && p2.pieceType == PieceType.Bishop
+            && p1.color != p2.color =>
+        true
       case _ => false

modules/rule/src/test/scala/de/nowchess/rule/DefaultRulesStateTransitionsTest.scala

@@ -65,7 +65,7 @@ class DefaultRulesStateTransitionsTest extends AnyFunSuite with Matchers:
 
   test("applyMove clears en passant square for non double pawn push"):
     val context = contextFromFen("4k3/8/8/8/8/8/4P3/4K3 w - d6 3 1")
-    val move = Move(sq("e2"), sq("e3"))
+    val move    = Move(sq("e2"), sq("e3"))
 
     val next = DefaultRules.applyMove(context)(move)
 
@@ -73,7 +73,7 @@ class DefaultRulesStateTransitionsTest extends AnyFunSuite with Matchers:
 
   test("applyMove resets halfMoveClock on pawn move"):
     val context = contextFromFen("4k3/8/8/8/8/8/4P3/4K3 w - - 12 1")
-    val move = Move(sq("e2"), sq("e4"))
+    val move    = Move(sq("e2"), sq("e4"))
 
     val next = DefaultRules.applyMove(context)(move)
 
@@ -81,7 +81,7 @@ class DefaultRulesStateTransitionsTest extends AnyFunSuite with Matchers:
 
   test("applyMove increments halfMoveClock on quiet non pawn move"):
     val context = contextFromFen("4k3/8/8/8/8/8/8/4K1N1 w - - 7 1")
-    val move = Move(sq("g1"), sq("f3"))
+    val move    = Move(sq("g1"), sq("f3"))
 
     val next = DefaultRules.applyMove(context)(move)
 
@@ -89,7 +89,7 @@ class DefaultRulesStateTransitionsTest extends AnyFunSuite with Matchers:
 
   test("applyMove resets halfMoveClock on capture"):
     val context = contextFromFen("r3k3/8/8/8/8/8/8/R3K3 w Qq - 9 1")
-    val move = Move(sq("a1"), sq("a8"), MoveType.Normal(isCapture = true))
+    val move    = Move(sq("a1"), sq("a8"), MoveType.Normal(isCapture = true))
 
     val next = DefaultRules.applyMove(context)(move)
 
@@ -98,7 +98,7 @@ class DefaultRulesStateTransitionsTest extends AnyFunSuite with Matchers:
 
   test("applyMove updates castling rights after king move"):
     val context = contextFromFen("r3k2r/8/8/8/8/8/8/R3K2R w KQkq - 0 1")
-    val move = Move(sq("e1"), sq("e2"))
+    val move    = Move(sq("e1"), sq("e2"))
 
     val next = DefaultRules.applyMove(context)(move)
 
@@ -109,7 +109,7 @@ class DefaultRulesStateTransitionsTest extends AnyFunSuite with Matchers:
 
   test("applyMove updates castling rights after rook move from h1"):
     val context = contextFromFen("r3k2r/8/8/8/8/8/8/4K2R w KQkq - 0 1")
-    val move = Move(sq("h1"), sq("h2"))
+    val move    = Move(sq("h1"), sq("h2"))
 
     val next = DefaultRules.applyMove(context)(move)
 
@@ -118,7 +118,7 @@ class DefaultRulesStateTransitionsTest extends AnyFunSuite with Matchers:
 
   test("applyMove revokes opponent castling right when rook on starting square is captured"):
     val context = contextFromFen("r3k3/8/8/8/8/8/8/R3K3 w Qq - 2 1")
-    val move = Move(sq("a1"), sq("a8"), MoveType.Normal(isCapture = true))
+    val move    = Move(sq("a1"), sq("a8"), MoveType.Normal(isCapture = true))
 
     val next = DefaultRules.applyMove(context)(move)
 
@@ -126,7 +126,7 @@ class DefaultRulesStateTransitionsTest extends AnyFunSuite with Matchers:
 
   test("applyMove executes kingside castling and repositions king and rook"):
     val context = contextFromFen("4k2r/8/8/8/8/8/8/R3K2R w KQk - 0 1")
-    val move = Move(sq("e1"), sq("g1"), MoveType.CastleKingside)
+    val move    = Move(sq("e1"), sq("g1"), MoveType.CastleKingside)
 
     val next = DefaultRules.applyMove(context)(move)
 
@@ -137,7 +137,7 @@ class DefaultRulesStateTransitionsTest extends AnyFunSuite with Matchers:
 
   test("applyMove executes queenside castling and repositions king and rook"):
     val context = contextFromFen("r3k3/8/8/8/8/8/8/R3K2R w KQq - 0 1")
-    val move = Move(sq("e1"), sq("c1"), MoveType.CastleQueenside)
+    val move    = Move(sq("e1"), sq("c1"), MoveType.CastleQueenside)
 
     val next = DefaultRules.applyMove(context)(move)
 
@@ -148,7 +148,7 @@ class DefaultRulesStateTransitionsTest extends AnyFunSuite with Matchers:
 
   test("applyMove executes en passant and removes captured pawn"):
     val context = contextFromFen("k7/8/8/3pP3/8/8/8/7K w - d6 0 1")
-    val move = Move(sq("e5"), sq("d6"), MoveType.EnPassant)
+    val move    = Move(sq("e5"), sq("d6"), MoveType.EnPassant)
 
     val next = DefaultRules.applyMove(context)(move)
 
@@ -158,7 +158,7 @@ class DefaultRulesStateTransitionsTest extends AnyFunSuite with Matchers:
 
   test("applyMove executes promotion with selected piece type"):
     val context = contextFromFen("4k3/P7/8/8/8/8/8/4K3 w - - 0 1")
-    val move = Move(sq("a7"), sq("a8"), MoveType.Promotion(PromotionPiece.Knight))
+    val move    = Move(sq("a7"), sq("a8"), MoveType.Promotion(PromotionPiece.Knight))
 
     val next = DefaultRules.applyMove(context)(move)
 
@@ -179,7 +179,7 @@ class DefaultRulesStateTransitionsTest extends AnyFunSuite with Matchers:
 
   test("applyMove preserves black castling rights after white kingside castling"):
     val context = contextFromFen("r3k2r/8/8/8/8/8/8/R3K2R w KQkq - 0 1")
-    val move = Move(sq("e1"), sq("g1"), MoveType.CastleKingside)
+    val move    = Move(sq("e1"), sq("g1"), MoveType.CastleKingside)
 
     val next = DefaultRules.applyMove(context)(move)
 
@@ -190,16 +190,18 @@ class DefaultRulesStateTransitionsTest extends AnyFunSuite with Matchers:
 
   test("applyMove can revoke both white castling rights when both rooks are captured"):
     val context = GameContext(
-      board = contextFromFen("4k3/8/8/8/8/8/8/R3K2R w KQ - 0 1").board.updated(sq("a8"), Piece(Color.Black, PieceType.Queen)),
+      board =
+        contextFromFen("4k3/8/8/8/8/8/8/R3K2R w KQ - 0 1").board.updated(sq("a8"), Piece(Color.Black, PieceType.Queen)),
       turn = Color.Black,
       castlingRights = CastlingRights(true, true, false, false),
       enPassantSquare = None,
       halfMoveClock = 0,
-      moves = List.empty
+      moves = List.empty,
     )
 
     val afterA1Capture = DefaultRules.applyMove(context)(Move(sq("a8"), sq("a1"), MoveType.Normal(isCapture = true)))
-    val afterH1Capture = DefaultRules.applyMove(afterA1Capture)(Move(sq("a1"), sq("h1"), MoveType.Normal(isCapture = true)))
+    val afterH1Capture =
+      DefaultRules.applyMove(afterA1Capture)(Move(sq("a1"), sq("h1"), MoveType.Normal(isCapture = true)))
 
     afterH1Capture.castlingRights.whiteKingSide shouldBe false
     afterH1Capture.castlingRights.whiteQueenSide shouldBe false
@@ -233,7 +235,7 @@ class DefaultRulesStateTransitionsTest extends AnyFunSuite with Matchers:
 
   test("applyMove executes black kingside castling and repositions pieces on rank 8"):
     val context = contextFromFen("r3k2r/8/8/8/8/8/8/4K3 b kq - 0 1")
-    val move = Move(sq("e8"), sq("g8"), MoveType.CastleKingside)
+    val move    = Move(sq("e8"), sq("g8"), MoveType.CastleKingside)
 
     val next = DefaultRules.applyMove(context)(move)
 
@@ -244,7 +246,7 @@ class DefaultRulesStateTransitionsTest extends AnyFunSuite with Matchers:
 
   test("applyMove revokes black castling rights when black rook moves from h8"):
     val context = contextFromFen("r3k2r/8/8/8/8/8/8/4K3 b kq - 0 1")
-    val move = Move(sq("h8"), sq("h7"))
+    val move    = Move(sq("h8"), sq("h7"))
 
     val next = DefaultRules.applyMove(context)(move)
 
@@ -253,7 +255,7 @@ class DefaultRulesStateTransitionsTest extends AnyFunSuite with Matchers:
 
   test("applyMove revokes black queenside castling right when black rook moves from a8"):
     val context = contextFromFen("r3k2r/8/8/8/8/8/8/4K3 b kq - 0 1")
-    val move = Move(sq("a8"), sq("a7"))
+    val move    = Move(sq("a8"), sq("a7"))
 
     val next = DefaultRules.applyMove(context)(move)
 
@@ -262,7 +264,7 @@ class DefaultRulesStateTransitionsTest extends AnyFunSuite with Matchers:
 
   test("applyMove revokes black kingside castling right when rook on h8 is captured"):
     val context = contextFromFen("4k2r/8/8/8/8/8/8/4K2R w Kk - 0 1")
-    val move = Move(sq("h1"), sq("h8"), MoveType.Normal(isCapture = true))
+    val move    = Move(sq("h1"), sq("h8"), MoveType.Normal(isCapture = true))
 
     val next = DefaultRules.applyMove(context)(move)
 
@@ -270,31 +272,25 @@ class DefaultRulesStateTransitionsTest extends AnyFunSuite with Matchers:
 
   test("candidateMoves creates all promotion move variants for black pawn"):
     val context = contextFromFen("4k3/8/8/8/8/8/p7/4K3 b - - 0 1")
-    val to = sq("a1")
+    val to      = sq("a1")
 
-    val pawnMoves = DefaultRules.candidateMoves(context)(sq("a2"))
+    val pawnMoves  = DefaultRules.candidateMoves(context)(sq("a2"))
     val promotions = pawnMoves.collect { case Move(_, `to`, MoveType.Promotion(piece)) => piece }
 
     promotions.toSet shouldBe Set(
       PromotionPiece.Queen,
       PromotionPiece.Rook,
       PromotionPiece.Bishop,
-      PromotionPiece.Knight
+      PromotionPiece.Knight,
     )
 
   test("applyMove promotion supports queen rook and bishop targets"):
     val base = contextFromFen("4k3/P7/8/8/8/8/8/4K3 w - - 0 1")
 
-    val queen = DefaultRules.applyMove(base)(Move(sq("a7"), sq("a8"), MoveType.Promotion(PromotionPiece.Queen)))
-    val rook = DefaultRules.applyMove(base)(Move(sq("a7"), sq("a8"), MoveType.Promotion(PromotionPiece.Rook)))
+    val queen  = DefaultRules.applyMove(base)(Move(sq("a7"), sq("a8"), MoveType.Promotion(PromotionPiece.Queen)))
+    val rook   = DefaultRules.applyMove(base)(Move(sq("a7"), sq("a8"), MoveType.Promotion(PromotionPiece.Rook)))
     val bishop = DefaultRules.applyMove(base)(Move(sq("a7"), sq("a8"), MoveType.Promotion(PromotionPiece.Bishop)))
 
     queen.board.pieceAt(sq("a8")) shouldBe Some(Piece(Color.White, PieceType.Queen))
     rook.board.pieceAt(sq("a8")) shouldBe Some(Piece(Color.White, PieceType.Rook))
     bishop.board.pieceAt(sq("a8")) shouldBe Some(Piece(Color.White, PieceType.Bishop))
-
-
-
-
-
-

modules/rule/src/test/scala/de/nowchess/rule/DefaultRulesTest.scala

@@ -1,6 +1,6 @@
 package de.nowchess.rule
 
-import de.nowchess.api.board.{Board, Color, File, Rank, Square, Piece, PieceType, CastlingRights}
+import de.nowchess.api.board.{Board, CastlingRights, Color, File, Piece, PieceType, Rank, Square}
 import de.nowchess.api.game.GameContext
 import de.nowchess.api.move.{Move, MoveType}
 import de.nowchess.io.fen.FenParser
@@ -15,31 +15,31 @@ class DefaultRulesTest extends AnyFunSuite with Matchers:
   // ── Pawn moves ──────────────────────────────────────────────────
 
   test("pawn can move forward one square"):
-    val fen = "8/8/8/8/8/8/4P3/8 w - - 0 1"
-    val context = FenParser.parseFen(fen).fold(_ => fail(), identity)
-    val moves = rules.allLegalMoves(context)
+    val fen       = "8/8/8/8/8/8/4P3/8 w - - 0 1"
+    val context   = FenParser.parseFen(fen).fold(_ => fail(), identity)
+    val moves     = rules.allLegalMoves(context)
     val pawnMoves = moves.filter(m => m.from == Square(File.E, Rank.R2))
     pawnMoves.exists(m => m.to == Square(File.E, Rank.R3)) shouldBe true
 
   test("pawn can move forward two squares from starting position"):
     val context = GameContext.initial
-    val moves = rules.allLegalMoves(context)
+    val moves   = rules.allLegalMoves(context)
     val e2Moves = moves.filter(m => m.from == Square(File.E, Rank.R2))
     e2Moves.exists(m => m.to == Square(File.E, Rank.R4)) shouldBe true
 
   test("pawn can capture diagonally"):
     // FEN: white pawn e4, black pawn d5
-    val fen = "8/8/8/3p4/4P3/8/8/8 w - - 0 1"
-    val context = FenParser.parseFen(fen).fold(_ => fail(), identity)
-    val moves = rules.allLegalMoves(context)
+    val fen      = "8/8/8/3p4/4P3/8/8/8 w - - 0 1"
+    val context  = FenParser.parseFen(fen).fold(_ => fail(), identity)
+    val moves    = rules.allLegalMoves(context)
     val captures = moves.filter(m => m.from == Square(File.E, Rank.R4) && m.moveType.isInstanceOf[MoveType.Normal])
     captures.exists(m => m.to == Square(File.D, Rank.R5)) shouldBe true
 
   test("pawn cannot move backward"):
     // FEN: white pawn on e4
-    val fen = "8/8/8/8/4P3/8/8/8 w - - 0 1"
-    val context = FenParser.parseFen(fen).fold(_ => fail(), identity)
-    val moves = rules.allLegalMoves(context)
+    val fen       = "8/8/8/8/4P3/8/8/8 w - - 0 1"
+    val context   = FenParser.parseFen(fen).fold(_ => fail(), identity)
+    val moves     = rules.allLegalMoves(context)
     val pawnMoves = moves.filter(m => m.from == Square(File.E, Rank.R4))
     pawnMoves.exists(m => m.to == Square(File.E, Rank.R3)) shouldBe false
 
@@ -47,18 +47,18 @@ class DefaultRulesTest extends AnyFunSuite with Matchers:
 
   test("moving king out of check removes it from legal moves if king stays in check"):
     // FEN: white king e1, black rook e8, white tries to move away
-    val fen = "4r3/8/8/8/8/8/8/4K3 w - - 0 1"
+    val fen     = "4r3/8/8/8/8/8/8/4K3 w - - 0 1"
     val context = FenParser.parseFen(fen).fold(_ => fail(), identity)
-    val moves = rules.allLegalMoves(context)
+    val moves   = rules.allLegalMoves(context)
 
     // King must move; e2 should be valid but d1 might be blocked by rook if still on same file
     moves.exists(m => m.from == Square(File.E, Rank.R1)) shouldBe true
 
   test("king cannot move to square attacked by opponent"):
     // FEN: white king e1, black rook e2 defended by black king e3
-    val fen = "8/8/8/8/8/4k3/4r3/4K3 w - - 0 1"
+    val fen     = "8/8/8/8/8/4k3/4r3/4K3 w - - 0 1"
     val context = FenParser.parseFen(fen).fold(_ => fail(), identity)
-    val moves = rules.allLegalMoves(context)
+    val moves   = rules.allLegalMoves(context)
 
     // King cannot move to e2 (occupied and attacked)
     val kingMovesToE2 = moves.filter(m => m.from == Square(File.E, Rank.R1) && m.to == Square(File.E, Rank.R2))
@@ -67,64 +67,67 @@ class DefaultRulesTest extends AnyFunSuite with Matchers:
   // ── Castling legality ────────────────────────────────────────────
 
   test("castling kingside is legal when king and rook unmoved and path clear"):
-    val fen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQK2R w KQkq - 0 1"
+    val fen     = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQK2R w KQkq - 0 1"
     val context = FenParser.parseFen(fen).fold(_ => fail(), identity)
-    val moves = rules.allLegalMoves(context)
+    val moves   = rules.allLegalMoves(context)
 
     val castles = moves.filter(m => m.moveType == MoveType.CastleKingside)
     castles.nonEmpty shouldBe true
 
   test("castling queenside is legal when king and rook unmoved and path clear"):
-    val fen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/R3K2R w KQkq - 0 1"
+    val fen     = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/R3K2R w KQkq - 0 1"
     val context = FenParser.parseFen(fen).fold(_ => fail(), identity)
-    val moves = rules.allLegalMoves(context)
+    val moves   = rules.allLegalMoves(context)
 
     val castles = moves.filter(m => m.moveType == MoveType.CastleQueenside)
     castles.nonEmpty shouldBe true
 
   test("castling is illegal when castling rights are false"):
     // FEN: king and rook in position, but castling rights disabled
-    val fen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQK2R w - - 0 1"
+    val fen     = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQK2R w - - 0 1"
     val context = FenParser.parseFen(fen).fold(_ => fail(), identity)
-    val moves = rules.allLegalMoves(context)
+    val moves   = rules.allLegalMoves(context)
 
     val castles = moves.filter(m => m.moveType == MoveType.CastleKingside)
     castles.isEmpty shouldBe true
 
   test("castling is illegal when king is in check"):
     // FEN: white king e1 in check from black rook e8
-    val fen = "4r3/8/8/8/8/8/8/R3K2R w KQ - 0 1"
+    val fen     = "4r3/8/8/8/8/8/8/R3K2R w KQ - 0 1"
     val context = FenParser.parseFen(fen).fold(_ => fail(), identity)
-    val moves = rules.allLegalMoves(context)
+    val moves   = rules.allLegalMoves(context)
 
     val castles = moves.filter(m => m.moveType == MoveType.CastleKingside || m.moveType == MoveType.CastleQueenside)
     castles.isEmpty shouldBe true
 
   test("castling is illegal when path has piece in the way"):
     // FEN: white king e1, white rook h1, white bishop f1 (blocks f-file)
-    val fen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBR1 w KQkq - 0 1"
+    val fen     = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBR1 w KQkq - 0 1"
     val context = FenParser.parseFen(fen).fold(_ => fail(), identity)
-    val moves = rules.allLegalMoves(context)
+    val moves   = rules.allLegalMoves(context)
 
     val castles = moves.filter(m => m.moveType == MoveType.CastleKingside)
     castles.isEmpty shouldBe true
 
   test("castling queenside is illegal when knight blocks on b8"):
     // Black king e8, black rook a8, black knight b8 (blocks queenside path)
-    val board = Board(Map(
-      Square(File.A, Rank.R8) -> Piece(Color.Black, PieceType.Rook),
-      Square(File.B, Rank.R8) -> Piece(Color.Black, PieceType.Knight),
-      Square(File.E, Rank.R8) -> Piece(Color.Black, PieceType.King),
-      Square(File.A, Rank.R1) -> Piece(Color.White, PieceType.Rook),
-      Square(File.E, Rank.R1) -> Piece(Color.White, PieceType.King)
-    ))
+    val board = Board(
+      Map(
+        Square(File.A, Rank.R8) -> Piece(Color.Black, PieceType.Rook),
+        Square(File.B, Rank.R8) -> Piece(Color.Black, PieceType.Knight),
+        Square(File.E, Rank.R8) -> Piece(Color.Black, PieceType.King),
+        Square(File.A, Rank.R1) -> Piece(Color.White, PieceType.Rook),
+        Square(File.E, Rank.R1) -> Piece(Color.White, PieceType.King),
+      ),
+    )
     val context = GameContext(
       board = board,
       turn = Color.Black,
-      castlingRights = CastlingRights(whiteKingSide = true, whiteQueenSide = true, blackKingSide = true, blackQueenSide = true),
+      castlingRights =
+        CastlingRights(whiteKingSide = true, whiteQueenSide = true, blackKingSide = true, blackQueenSide = true),
       enPassantSquare = None,
       halfMoveClock = 0,
-      moves = List.empty
+      moves = List.empty,
     )
     val moves = rules.allLegalMoves(context)
 
@@ -135,18 +138,18 @@ class DefaultRulesTest extends AnyFunSuite with Matchers:
 
   test("en passant is legal when en passant square is set"):
     // FEN: white pawn e5, black pawn d5 (just double-pushed), en passant square d6
-    val fen = "k7/8/8/3pP3/8/8/8/7K w - d6 0 1"
+    val fen     = "k7/8/8/3pP3/8/8/8/7K w - d6 0 1"
     val context = FenParser.parseFen(fen).fold(_ => fail(), identity)
-    val moves = rules.allLegalMoves(context)
+    val moves   = rules.allLegalMoves(context)
 
     val epMoves = moves.filter(m => m.moveType == MoveType.EnPassant)
     epMoves.exists(m => m.to == Square(File.D, Rank.R6)) shouldBe true
 
   test("en passant is illegal when en passant square is none"):
     // FEN: white pawn e5, black pawn d5, but no en passant square
-    val fen = "k7/8/8/3pP3/8/8/8/7K w - - 0 1"
+    val fen     = "k7/8/8/3pP3/8/8/8/7K w - - 0 1"
     val context = FenParser.parseFen(fen).fold(_ => fail(), identity)
-    val moves = rules.allLegalMoves(context)
+    val moves   = rules.allLegalMoves(context)
 
     val epMoves = moves.filter(m => m.moveType == MoveType.EnPassant)
     epMoves.isEmpty shouldBe true
@@ -155,9 +158,9 @@ class DefaultRulesTest extends AnyFunSuite with Matchers:
 
   test("pinned piece cannot move and expose king to check"):
     // FEN: white king e1, white bishop d2 (pinned), black rook a2
-    val fen = "8/8/8/8/8/8/r1B1K3/8 w - - 0 1"
+    val fen     = "8/8/8/8/8/8/r1B1K3/8 w - - 0 1"
     val context = FenParser.parseFen(fen).fold(_ => fail(), identity)
-    val moves = rules.allLegalMoves(context)
+    val moves   = rules.allLegalMoves(context)
 
     // Bishop on d2 is pinned by rook on a2; it cannot move
     val bishopMoves = moves.filter(m => m.from == Square(File.C, Rank.R2))
@@ -166,9 +169,9 @@ class DefaultRulesTest extends AnyFunSuite with Matchers:
   test("piece blocking a check is legal"):
     // FEN: white king e1, white rook d1, black bishop a4 attacking e1 via d2
     // Actually, this is complex. Let's use: white king e1, black rook e8, white pawn blocks on e2
-    val fen = "4r3/8/8/8/8/8/4P3/4K3 w - - 0 1"
+    val fen     = "4r3/8/8/8/8/8/4P3/4K3 w - - 0 1"
     val context = FenParser.parseFen(fen).fold(_ => fail(), identity)
-    val moves = rules.allLegalMoves(context)
+    val moves   = rules.allLegalMoves(context)
 
     // White is in check; only moves that block or move the king are legal
     moves.nonEmpty shouldBe true