Non-royal castling pieces (#82)

lib/src/actions/actions/checks.dart

@@ -104,7 +104,10 @@ class ActionCheckPieceCount extends Action {
             }
             return [
               EffectSetGameResult(
-                WonGameElimination(winner: white ? Bishop.white : Bishop.black),
+                WonGameElimination(
+                  winner: white ? Bishop.white : Bishop.black,
+                  pieceType: pieceType,
+                ),
               ),
             ];
           },

lib/src/constants.dart

@@ -208,6 +208,7 @@ enum Variants {
   dobutsu(Dobutsu.dobutsu, alt: 'Dobutsu Shogi'),
   spawn(MiscVariants.spawn, alt: 'Spawn Chess'),
   kinglet(MiscVariants.kinglet, alt: 'Kinglet Chess'),
+  extinction(MiscVariants.extinction),
   threeKings(MiscVariants.threeKings, alt: 'Three Kings Chess'),
   domination(MiscVariants.domination),
   dart(MiscVariants.dart),

lib/src/fen.dart

@@ -120,6 +120,7 @@ ParseFenResult parseFen({
   int sq = 0;
   int emptySquares = 0;
   List<int> royalSquares = List.filled(Bishop.numPlayers, Bishop.invalid);
+  List<int> castlingSquares = List.filled(Bishop.numPlayers, Bishop.invalid);
 
   for (String c in boardSymbols) {
     if (c == '~') {
@@ -154,6 +155,9 @@ ParseFenResult parseFen({
       if (variant.pieces[pieceIndex].type.royal) {
         royalSquares[colour] = sq;
       }
+      if (variant.pieces[pieceIndex].type.castling) {
+        castlingSquares[colour] = sq;
+      }
       sq++;
     }
   }
@@ -191,7 +195,7 @@ ParseFenResult parseFen({
   final castling = variant.castling
       ? setupCastling(
           castlingString: castlingStr,
-          royalSquares: royalSquares,
+          castlingSquares: castlingSquares,
           board: board,
           variant: variant,
         )
@@ -204,6 +208,7 @@ ParseFenResult parseFen({
     epSquare: ep,
     castlingRights: castling.castlingRights,
     royalSquares: royalSquares,
+    castlingSquares: castlingSquares,
     virginFiles: virginFiles,
     hands: hands,
     gates: gates,
@@ -222,14 +227,14 @@ class ParseFenResult {
 
 class CastlingSetup {
   final int castlingRights;
-  final int? royalFile;
+  final int? castlingFile;
   final int? castlingTargetK;
   final int? castlingTargetQ;
   final List<String>? castlingFileSymbols;
 
   const CastlingSetup({
     required this.castlingRights,
-    this.royalFile,
+    this.castlingFile,
     this.castlingTargetK,
     this.castlingTargetQ,
     this.castlingFileSymbols,
@@ -240,7 +245,7 @@ class CastlingSetup {
 
 CastlingSetup setupCastling({
   required String castlingString,
-  required List<int> royalSquares,
+  required List<int> castlingSquares,
   required List<int> board,
   required BuiltVariant variant,
 }) {
@@ -252,20 +257,20 @@ CastlingSetup setupCastling({
     throw ('Invalid castling string');
   }
   List<String>? castlingFileSymbols;
-  int? royalFile;
+  int? castlingFile;
   int? castlingTargetK;
   int? castlingTargetQ;
   final size = variant.boardSize;
   CastlingRights cr = 0;
   for (String c in castlingString.split('')) {
     // there is probably a better way to do all of this
     bool white = c == c.toUpperCase();
-    royalFile = size.file(royalSquares[white ? 0 : 1]);
+    castlingFile = size.file(castlingSquares[white ? 0 : 1]);
     if (Castling.symbols.containsKey(c)) {
       cr += Castling.symbols[c]!;
     } else {
       int cFile = fileFromSymbol(c);
-      bool kingside = cFile > size.file(royalSquares[white ? 0 : 1]);
+      bool kingside = cFile > size.file(castlingSquares[white ? 0 : 1]);
       if (kingside) {
         castlingTargetK = cFile;
         cr += white ? Castling.k : Castling.bk;
@@ -285,9 +290,9 @@ CastlingSetup setupCastling({
       bool kingside = false;
       for (int j = 0; j < size.h; j++) {
         int piece = board[r + j].type;
-        if (piece == variant.royalPiece) {
+        if (piece == variant.castlingPiece) {
           kingside = true;
-        } else if (piece == variant.castlingPiece) {
+        } else if (piece == variant.rookPiece) {
           if (kingside) {
             castlingTargetK = j;
           } else {
@@ -306,7 +311,7 @@ CastlingSetup setupCastling({
   }
   return CastlingSetup(
     castlingRights: cr,
-    royalFile: royalFile,
+    castlingFile: castlingFile,
     castlingTargetK: castlingTargetK,
     castlingTargetQ: castlingTargetQ,
     castlingFileSymbols: castlingFileSymbols,

lib/src/game/game.dart

@@ -32,7 +32,7 @@ class Game {
 
   int? castlingTargetK;
   int? castlingTargetQ;
-  int? royalFile;
+  int? castlingFile;
   List<String> castlingFileSymbols = ['K', 'Q', 'k', 'q'];
   late MoveGenParams royalCaptureOptions;
 
@@ -81,7 +81,7 @@ class Game {
     final newState = result.state.copyWith(hash: zobrist.compute(result.state));
     zobrist.incrementHash(newState.hash);
     history.add(newState);
-    royalFile = result.castling.royalFile;
+    castlingFile = result.castling.castlingFile;
     castlingTargetK = result.castling.castlingTargetK;
     castlingTargetQ = result.castling.castlingTargetQ;
     castlingFileSymbols =
@@ -384,7 +384,10 @@ class Game {
     }
 
     // Generate castling
-    if (variant.castling && options.castling && pieceType.royal && !inCheck) {
+    if (variant.castling &&
+        options.castling &&
+        pieceType.castling &&
+        !inCheck) {
       bool kingside = colour == Bishop.white
           ? state.castlingRights.wk
           : state.castlingRights.bk;
@@ -425,22 +428,22 @@ class Game {
         if (board[targetSq].isNotEmpty &&
             targetSq != rookSq &&
             targetSq != square) continue;
-        int numMidSqs = (targetFile - royalFile!).abs();
+        int numMidSqs = (targetFile - castlingFile!).abs();
         bool valid = true;
         if (!options.ignorePieces) {
           int numRookMidSquares = (targetFile - rookFile).abs();
           if (numRookMidSquares > 1) {
             for (int j = 1; j <= numRookMidSquares; j++) {
               int midFile = rookFile + (i == 0 ? -j : j);
               int midSq = size.square(midFile, royalRank);
-              if (board[midSq].isNotEmpty && midFile != royalFile) {
+              if (board[midSq].isNotEmpty && midFile != castlingFile) {
                 valid = false;
                 break;
               }
             }
           }
           for (int j = 1; j <= numMidSqs; j++) {
-            int midFile = royalFile! + (i == 0 ? j : -j);
+            int midFile = castlingFile! + (i == 0 ? j : -j);
 
             // For some Chess960 positions.
             // See also https://github.com/alexobviously/bishop/issues/11
@@ -456,7 +459,7 @@ class Game {
               break;
             }
 
-            if (midFile == targetFile && targetFile == royalFile) {
+            if (midFile == targetFile && targetFile == castlingFile) {
               continue;
             } // king starting on target
 

lib/src/game/game_movement.dart

@@ -233,6 +233,7 @@ extension GameMovement on Game {
 
     int castlingRights = state.castlingRights;
     List<int> royalSquares = List.from(state.royalSquares);
+    List<int> castlingSquares = List.from(state.castlingSquares);
 
     if (move.enPassant) {
       // Remove the captured ep piece
@@ -265,29 +266,37 @@ extension GameMovement on Game {
           : variant.castlingOptions.qTarget!;
       int rookFile = kingside ? castlingFile - 1 : castlingFile + 1;
       int rookSq = size.square(rookFile, fromRank);
-      int kingSq = size.square(castlingFile, fromRank);
+      int castlingSq = size.square(castlingFile, fromRank);
       int rook = board[move.castlingPieceSquare!];
       hash ^= zobrist.table[move.castlingPieceSquare!][rook.piece];
-      if (board[kingSq].isNotEmpty) {
-        hash ^= zobrist.table[kingSq][board[kingSq].piece];
+      if (board[castlingSq].isNotEmpty) {
+        hash ^= zobrist.table[castlingSq][board[castlingSq].piece];
       }
-      hash ^= zobrist.table[kingSq][fromSq.piece];
+      hash ^= zobrist.table[castlingSq][fromSq.piece];
       if (board[rookSq].isNotEmpty) {
         hash ^= zobrist.table[rookSq][board[rookSq].piece];
       }
       hash ^= zobrist.table[rookSq][rook.piece];
       board[move.castlingPieceSquare!] = Bishop.empty;
-      board[kingSq] = fromSq.setInitialState(false);
+      board[castlingSq] = fromSq.setInitialState(false);
       board[rookSq] = rook;
       castlingRights = castlingRights.remove(colour);
-      royalSquares[colour] = kingSq;
-    } else if (fromPiece.royal) {
-      // king moved
-      castlingRights = castlingRights.remove(colour);
-      royalSquares[colour] = move.to;
+      castlingSquares[colour] = castlingSq;
+      if (fromPiece.royal) {
+        royalSquares[colour] = castlingSq;
+      }
+    } else if (fromPiece.royal || fromPiece.castling) {
+      // Royal or castling piece moved, but it wasn't castling.
+      if (fromPiece.castling) {
+        castlingRights = castlingRights.remove(colour);
+        castlingSquares[colour] = move.to;
+      }
+      if (fromPiece.royal) {
+        royalSquares[colour] = move.to;
+      }
     } else {
       // If the player's rook moved, remove relevant castling rights
-      if (fromSq.type == variant.castlingPiece) {
+      if (fromSq.type == variant.rookPiece) {
         int fromFile = size.file(move.from);
         bool onFirstRank = size.rank(move.from) == size.firstRank(colour);
         int ks = colour == Bishop.white ? Castling.k : Castling.bk;
@@ -302,8 +311,8 @@ extension GameMovement on Game {
           castlingRights = castlingRights.flip(qs);
         }
       }
-      // If the opponent's rook was captured, remove relevant castling rights
-      if (move.capture && move.capturedPiece!.type == variant.castlingPiece) {
+      // If the opponent's rook was captured, remove relevant castling rights.
+      if (move.capture && move.capturedPiece!.type == variant.rookPiece) {
         // rook captured
         int toFile = size.file(move.to);
         int opponent = colour.opponent;
@@ -321,6 +330,10 @@ extension GameMovement on Game {
         }
       }
     }
+    // If the opponent's castling piece was captured.
+    if (move.capture && move.capturedPiece!.type == variant.castlingPiece) {
+      castlingRights = castlingRights.remove(colour.opponent);
+    }
     if (castlingRights != state.castlingRights) {
       hash ^= zobrist.table[zobrist.castling][state.castlingRights];
       hash ^= zobrist.table[zobrist.castling][castlingRights];
@@ -341,6 +354,7 @@ extension GameMovement on Game {
           state.turn == Bishop.black ? state.fullMoves + 1 : state.fullMoves,
       castlingRights: castlingRights,
       royalSquares: royalSquares,
+      castlingSquares: castlingSquares,
       virginFiles: virginFiles,
       epSquare: epSquare,
       hash: hash,

lib/src/game/game_outputs.dart

@@ -218,10 +218,11 @@ extension GameOutputs on Game {
     int firstTurn = history.first.turn;
     int turn = firstTurn;
     String pgn = '';
-     for (int i = 0; i < moves.length; i++) {
-      if (i == 0 || turn == Bishop.white)
+    for (int i = 0; i < moves.length; i++) {
+      if (i == 0 || turn == Bishop.white) {
         pgn =
             '$pgn${firstMove + i ~/ 2}${(i == 0 && turn == Bishop.black) ? "" : ". "}';
+      }
       if (i == 0 && turn == Bishop.black) {
         pgn = '$pgn... ';
         firstMove++;

lib/src/game/game_result.dart

@@ -107,13 +107,18 @@ class WonGameRoyalDead extends WonGame {
 }
 
 class WonGameElimination extends WonGame {
-  const WonGameElimination({required super.winner});
+  final String? pieceType;
+  const WonGameElimination({required super.winner, this.pieceType});
 
   @override
   String toString() => 'WonGameElimination($winner)';
 
   @override
-  String get readable => '${super.readable} by elimination';
+  String get readable => [
+        super.readable,
+        'by elimination',
+        if (pieceType != null) '($pieceType)',
+      ].join(' ');
 }
 
 class WonGameStalemate extends WonGame {

lib/src/piece_type.dart

@@ -9,9 +9,14 @@ class PieceType {
   /// All of the different move groups this piece can make.
   final List<MoveDefinition> moves;
 
-  /// Royal pieces can be checkmated, and can castle.
+  /// Royal pieces can be checkmated, and can castle,
+  /// unless [castling] is false.
   final bool royal;
 
+  /// Whether this is a castling piece.
+  /// If not specified, it will be the same as [royal].
+  final bool castling;
+
   /// Defines the promotion behaviour of this piece type.
   final PiecePromoOptions promoOptions;
 
@@ -51,14 +56,15 @@ class PieceType {
     this.betza,
     required this.moves,
     this.royal = false,
+    bool? castling,
     this.promoOptions = PiecePromoOptions.promoPiece,
     this.enPassantable = false,
     this.noSanSymbol = false,
     this.value = Bishop.defaultPieceValue,
     this.regionEffects = const [],
     this.actions = const [],
     this.optimisationData,
-  });
+  }) : castling = castling ?? royal;
 
   factory PieceType.fromJson(
     Map<String, dynamic> json, {
@@ -68,6 +74,7 @@ class PieceType {
       return PieceType.fromBetza(
         json['betza'],
         royal: json['royal'] ?? false,
+        castling: json['castling'],
         promoOptions: json.containsKey('promoOptions')
             ? PiecePromoOptions.fromJson(json['promoOptions'])
             : PiecePromoOptions.promoPiece,
@@ -97,6 +104,7 @@ class PieceType {
     return {
       'betza': betza,
       if (verbose || royal) 'royal': royal,
+      if (verbose || castling != royal) 'castling': castling,
       if (verbose || promoOptions != PiecePromoOptions.promoPiece)
         'promoOptions': promoOptions.toJson(),
       if (verbose || enPassantable) 'enPassantable': enPassantable,
@@ -119,6 +127,7 @@ class PieceType {
     String? betza,
     List<MoveDefinition>? moves,
     bool? royal,
+    bool? castling,
     PiecePromoOptions? promoOptions,
     bool? enPassantable,
     bool? noSanSymbol,
@@ -131,6 +140,7 @@ class PieceType {
         betza: betza ?? this.betza,
         moves: moves ?? this.moves,
         royal: royal ?? this.royal,
+        castling: castling ?? this.castling,
         promoOptions: promoOptions ?? this.promoOptions,
         enPassantable: enPassantable ?? this.enPassantable,
         noSanSymbol: noSanSymbol ?? this.noSanSymbol,
@@ -194,6 +204,7 @@ class PieceType {
   factory PieceType.fromBetza(
     String betza, {
     bool royal = false,
+    bool? castling,
     PiecePromoOptions promoOptions = PiecePromoOptions.promoPiece,
     bool enPassantable = false,
     bool noSanSymbol = false,
@@ -209,6 +220,7 @@ class PieceType {
       betza: betza,
       moves: moves,
       royal: royal,
+      castling: castling,
       promoOptions: promoOptions,
       enPassantable: enPassantable,
       noSanSymbol: noSanSymbol,