public Position PlayMove(Move move)
{
// 'My' refers to player to move, 'other' refers to other player
var my_player = PlayerToMove;
var other_player = Helper.GetOtherPlayer(my_player);
var my_pieces = GetPieces(my_player);
var other_pieces = GetPieces(other_player);
PlayerPieceSet new_my_pieces = null;
if (move.IsPromotion)
{
Debug.Assert(move.Piece == Exports.Pieces.Pawn);
var tmp_pieces = PlayerPieceSet.RemovePiece(my_pieces,
Exports.Pieces.Pawn, move.FromCell);
new_my_pieces = PlayerPieceSet.InsertPiece(tmp_pieces,
move.PromoteToPiece, move.ToCell);
}
else if (move.IsShortCastle || move.IsLongCastle)
{
int base_row = my_player == Players.White ?
Chessboard.ROW_MIN : Chessboard.ROW_MAX;
Debug.Assert(move.Piece == Exports.Pieces.King);
var tmp_pieces = PlayerPieceSet.MovePiece(my_pieces,
Exports.Pieces.King, move.FromCell, move.ToCell);
if (move.IsShortCastle)
{
new_my_pieces = PlayerPieceSet.MovePiece(tmp_pieces,
Exports.Pieces.Rook,
ChessboardCell.CalculateValue(base_row, Chessboard.COLUMN_H),
ChessboardCell.CalculateValue(base_row, Chessboard.COLUMN_F));
}
else
{
new_my_pieces = PlayerPieceSet.MovePiece(tmp_pieces,
Exports.Pieces.Rook,
ChessboardCell.CalculateValue(base_row, Chessboard.COLUMN_A),
ChessboardCell.CalculateValue(base_row, Chessboard.COLUMN_D));
}
}
else
{
new_my_pieces = PlayerPieceSet.MovePiece(my_pieces,
move.Piece, move.FromCell, move.ToCell);
}
PlayerPieceSet new_other_pieces = null;
if (move.IsCapture)
{
Exports.Pieces piece_to_remove = Exports.Pieces.NoPiece;
int remove_piece_at = 0;
if (move.IsEnPassantCapture)
{
var move_to_cell = new ChessboardCell(move.ToCell);
remove_piece_at = ChessboardCell.CalculateValue(
move_to_cell.Row + (IsWhiteToMove ? -1 : 1),
move_to_cell.Column);
// Only pawns can capture en passant
piece_to_remove = Exports.Pieces.Pawn;
}
else
{
remove_piece_at = move.ToCell;
piece_to_remove = other_pieces.GetPieceAtCell(remove_piece_at);
}
new_other_pieces = PlayerPieceSet.RemovePiece(other_pieces,
piece_to_remove, remove_piece_at);
}
else
{
// No change to other player's pieces, re-use the object
new_other_pieces = other_pieces;
}
// TODO - consider memory pooling here
var result = new Position();
var new_white_pieces =
IsWhiteToMove ? new_my_pieces : new_other_pieces;
var new_black_pieces =
IsWhiteToMove ? new_other_pieces : new_my_pieces;
int? new_en_passant_capture_column = null;
if (move.Piece == Exports.Pieces.Pawn)
{
var from = new ChessboardCell(move.FromCell);
var to_row = new ChessboardCell(move.ToCell).Row;
if (Math.Abs(from.Row - to_row) == 2)
{
new_en_passant_capture_column = from.Column;
}
}
var new_fullmove_number = FullmoveNumber;
if (other_player == Players.White)
{
++new_fullmove_number;
}
var new_halfmove_clock = HalfmoveClock + 1;
if (move.Piece == Exports.Pieces.Pawn || move.IsCapture)
{
new_halfmove_clock = 0;
}
var new_white_castling_options = CalcNewCastlingOptions(Players.White,
new_white_pieces, Chessboard.ROW_MIN);
var new_black_castling_options = CalcNewCastlingOptions(Players.Black,
new_black_pieces, Chessboard.ROW_MAX);
result.Reset(new_white_pieces,
new_black_pieces,
other_player,
new_white_castling_options,
new_black_castling_options,
new_en_passant_capture_column,
new_fullmove_number,
(ushort)new_halfmove_clock);
return result;
}
