public static Position makeMove(Position position, Move move) {
if (isPseudoLegalCastleMove(position, move)) {
// castle move
Position.Builder builder = new Position.Builder(position);
builder.clearEnPassantPawn().clearPhantomKings().switchPlayerToMove();
if (builder.isWhiteToMove()) {
builder.fullmoveNumber(builder.getFullmoveNumber() + 1);
}
makeCastleMove(builder, move);
return builder.build();
} else {
// normal move
Position.Builder builder = new Position.Builder(position);
builder.clearEnPassantPawn().clearPhantomKings();
Piece fromPiece = position.getPiece(move.getFrom());
Piece toPiece = position.getPiece(move.getTo());
builder.clearPhantomKings();
// adjust castling availability
if (fromPiece == Piece.WHITE_KING) {
builder.canWhiteCastleKingside(false).canWhiteCastleQueenside(false);
} else if (fromPiece == Piece.BLACK_KING) {
builder.canBlackCastleKingside(false).canBlackCastleQueenside(false);
}
if (move.getFrom() == 0) {
builder.canWhiteCastleQueenside(false);
} else if (move.getFrom() == 7) {
builder.canWhiteCastleKingside(false);
} else if (move.getFrom() == 56) {
builder.canBlackCastleQueenside(false);
} else if (move.getFrom() == 63) {
builder.canBlackCastleKingside(false);
}
// if we're capturing an en passant pawn, remove the real pawn, too
if (toPiece == Piece.WHITE_EN_PASSANT_PAWN) {
builder.piece(move.getTo() + 8, Piece.EMPTY);
} else if (toPiece == Piece.BLACK_EN_PASSANT_PAWN) {
builder.piece(move.getTo() - 8, Piece.EMPTY);
}
builder.clearEnPassantPawn();
// create en passant pawns if necessary
if (fromPiece == Piece.WHITE_PAWN && move.getFrom() / 8 == 1 && move.getTo() / 8 == 3) {
int enPassantPawnIndex = move.getFrom() + 8;
builder.enPassantPawnIndex(enPassantPawnIndex, true);
} else if (fromPiece == Piece.BLACK_PAWN
&& move.getFrom() / 8 == 6
&& move.getTo() / 8 == 4) {
int enPassantPawnIndex = move.getFrom() - 8;
builder.enPassantPawnIndex(enPassantPawnIndex, false);
}
boolean isPromotionMove = isPseudoPromotionMove(position, move);
// actually move the selected piece
builder.piece(move.getTo(), fromPiece);
builder.piece(move.getFrom(), Piece.EMPTY);
// if necessary, perform a promotion
if (isPromotionMove) {
if (move.getPromotionPiece() == null) {
throw new RuntimeException("Made a promotion move, but no promotion piece selected");
}
Piece promoPiece =
Piece.getFromColorAndPieceType(builder.isWhiteToMove(), move.getPromotionPiece());
builder.piece(move.getTo(), promoPiece);
}
builder.switchPlayerToMove();
if (builder.isWhiteToMove()) {
builder.fullmoveNumber(builder.getFullmoveNumber() + 1);
}
return builder.build();
}
}
/**
* The specified move must already be checked for pseudo legality, this function does not check.
*/
private static Position.Builder makeCastleMove(Position.Builder builder, Move move) {
assert (builder.getPiece(move.getFrom()) == Piece.WHITE_KING)
|| (builder.getPiece(move.getFrom()) == Piece.BLACK_KING);
if (move.getFrom() == 4 && move.getTo() == 6) {
// white O-O
builder.piece(4, Piece.EMPTY);
builder.piece(5, Piece.WHITE_ROOK);
builder.piece(6, Piece.WHITE_KING);
builder.piece(7, Piece.EMPTY);
builder.setPhantomKings(4, 5);
} else if (move.getFrom() == 4 && move.getTo() == 2) {
// white O-O-O
builder.piece(0, Piece.EMPTY);
builder.piece(1, Piece.EMPTY);
builder.piece(2, Piece.WHITE_KING);
builder.piece(3, Piece.WHITE_ROOK);
builder.piece(4, Piece.EMPTY);
builder.setPhantomKings(3, 4);
} else if (move.getFrom() == 60 && move.getTo() == 62) {
// black O-O
builder.piece(60, Piece.EMPTY);
builder.piece(61, Piece.BLACK_ROOK);
builder.piece(62, Piece.BLACK_KING);
builder.piece(63, Piece.EMPTY);
builder.setPhantomKings(60, 61);
} else if (move.getFrom() == 60 && move.getTo() == 58) {
// black O-O-O
builder.piece(56, Piece.EMPTY);
builder.piece(57, Piece.EMPTY);
builder.piece(58, Piece.BLACK_KING);
builder.piece(59, Piece.BLACK_ROOK);
builder.piece(60, Piece.EMPTY);
builder.setPhantomKings(59, 60);
} else {
throw new AssertionError();
}
return builder;
}
