private ErrorCondition Move(Move move)
{
if (!BitTranslator.IsValidSquare(move.StartFile, move.StartRank))
{
return(ErrorCondition.InvalidSquare);
}
if (!BitTranslator.IsValidSquare(move.EndFile, move.EndRank))
{
return(ErrorCondition.InvalidSquare);
}
ulong startSquare = BitTranslator.TranslateToBit(move.StartFile, move.StartRank);
if ((CurrentTurn & startSquare) == 0)
{
return(ErrorCondition.MustMoveOwnPiece); // Can't move if not your turn
}
ulong endSquare = BitTranslator.TranslateToBit(move.EndFile, move.EndRank);
if ((CurrentTurn & endSquare) != 0)
{
return(ErrorCondition.CantTakeOwnPiece); // Can't end move on own piece
}
ulong allMoves = MoveGenerator.GenerateValidMovesForPiece(CurrentState, startSquare);
if ((endSquare & allMoves) == 0)
{
return(ErrorCondition.InvalidMovement); // End square is not a valid move
}
// The move is good, so update state
// Update current state
UpdateState(move, startSquare, endSquare);
return(ErrorCondition.None);
}
public static GameState ApplyMove(GameState state, ulong startSq, ulong endSq)
{
var start = BitTranslator.TranslateToSquare(startSq);
var end = BitTranslator.TranslateToSquare(endSq);
var move = new Move(start.File, start.Rank, end.File, end.Rank);
return(ApplyMove(state, move, startSq, endSq));
}
public SquareContents GetSquareContents(char file, int rank)
{
var result = (SquareContents)0;
if (BitTranslator.IsValidSquare(file, rank))
{
ulong bit = BitTranslator.TranslateToBit(file, rank);
result = CurrentState.Board.GetSquareContents(bit);
}
return(result);
}
public List <Square> GetValidMoves(char file, int rank)
{
if (!BitTranslator.IsValidSquare(file, rank))
{
throw new InvalidOperationException();
}
var square = BitTranslator.TranslateToBit(file, rank);
ulong allMoves = MoveGenerator.GenerateValidMovesForPiece(CurrentState, square);
return(BitTranslator.TranslateToSquares(allMoves));
}
private static bool TryInferStartSquare(BoardState state, ulong piecesOnCurrentSide, bool isWhiteMove, bool isCapture, char pieceDesignation, ref ParsedMoveState result)
{
var endBit = BitTranslator.TranslateToBit(result.EndFile, result.EndRank);
var disambiguityMask = BuildDisambiguityMask(result);
switch (pieceDesignation)
{
case Constants.PieceNotation.King:
{
var possibleStartBits = MoveGenerator.GetKingMovements(endBit);
var existingOfPiece = state.Kings & piecesOnCurrentSide;
var actualStartPiece = possibleStartBits & existingOfPiece;
if (disambiguityMask != 0)
{
actualStartPiece &= disambiguityMask;
}
if (actualStartPiece == 0)
{
return(false);
}
var startSquare = BitTranslator.TranslateToSquare(actualStartPiece);
result.StartFile = startSquare.File;
result.StartRank = startSquare.Rank;
return(true);
}
case Constants.PieceNotation.Knight:
{
var possibleStartBits = MoveGenerator.GetKnightMovements(endBit);
var existingOfPiece = state.Knights & piecesOnCurrentSide;
var actualStartPiece = possibleStartBits & existingOfPiece;
if (disambiguityMask != 0)
{
actualStartPiece &= disambiguityMask;
}
if (actualStartPiece == 0)
{
return(false);
}
var startSquare = BitTranslator.TranslateToSquare(actualStartPiece);
result.StartFile = startSquare.File;
result.StartRank = startSquare.Rank;
return(true);
}
case Constants.PieceNotation.Queen:
{
var possibleStartBits = MoveGenerator.GetQueenMovements(endBit, state);
var existingOfPiece = state.Queens & piecesOnCurrentSide;
var actualStartPiece = possibleStartBits & existingOfPiece;
if (disambiguityMask != 0)
{
actualStartPiece &= disambiguityMask;
}
if (actualStartPiece == 0)
{
return(false);
}
var startSquare = BitTranslator.TranslateToSquare(actualStartPiece);
result.StartFile = startSquare.File;
result.StartRank = startSquare.Rank;
return(true);
}
case Constants.PieceNotation.Rook:
{
var possibleStartBits = MoveGenerator.GetRookMovements(endBit, state);
var existingOfPiece = state.Rooks & piecesOnCurrentSide;
var actualStartPiece = possibleStartBits & existingOfPiece;
if (disambiguityMask != 0)
{
actualStartPiece &= disambiguityMask;
}
if (actualStartPiece == 0)
{
return(false);
}
var startSquare = BitTranslator.TranslateToSquare(actualStartPiece);
result.StartFile = startSquare.File;
result.StartRank = startSquare.Rank;
return(true);
}
case Constants.PieceNotation.Bishop:
{
var possibleStartBits = MoveGenerator.GetBishopMovements(endBit, state);
var existingOfPiece = state.Bishops & piecesOnCurrentSide;
var actualStartPiece = possibleStartBits & existingOfPiece;
if (disambiguityMask != 0)
{
actualStartPiece &= disambiguityMask;
}
if (actualStartPiece == 0)
{
return(false);
}
var startSquare = BitTranslator.TranslateToSquare(actualStartPiece);
result.StartFile = startSquare.File;
result.StartRank = startSquare.Rank;
return(true);
}
case Constants.PieceNotation.Pawn:
{
ulong actualStartPiece;
if (isWhiteMove)
{
var possibleMoves = endBit >> 8 | endBit >> 16;
var possibleAttacks = (endBit >> 7 & (~MoveGenerator.Rank8)) | (endBit >> 9 & (~MoveGenerator.Rank1));
var possibleStart = isCapture ? possibleAttacks : possibleMoves;
var pawns = state.Pawns & state.WhitePieces;
actualStartPiece = pawns & possibleStart;
}
else
{
var possibleMoves = endBit << 8 | endBit << 16;
var possibleAttacks = (endBit << 7 & (~MoveGenerator.Rank1)) | (endBit << 9 & (~MoveGenerator.Rank8));
var possibleStart = isCapture ? possibleAttacks : possibleMoves;
var pawns = state.Pawns & state.BlackPieces;
actualStartPiece = pawns & possibleStart;
}
if (disambiguityMask != 0)
{
actualStartPiece &= disambiguityMask;
}
if (actualStartPiece == 0)
{
return(false);
}
var startSquare = BitTranslator.TranslateToSquare(actualStartPiece);
result.StartFile = startSquare.File;
result.StartRank = startSquare.Rank;
return(true);
}
default:
return(false);
}
}
public static string ToMoveString(Move move, BoardState board, AttackState attackState)
{
// Algo: Move from end, adding tokens in order
// - Check if move is promotion, add tokens if so
// - Add end square
// - Check if move is capture, output 'x' if so
// - Then check if multiple pieces of same type can move to end square, then output first rank or file of moved piece
// - Then output piece notation if piece is not a pawn
//
// - Now that the move string is built, splice to only used tokens
var startSquareBit = BitTranslator.TranslateToBit(move.StartFile, move.StartRank);
var endSquareBit = BitTranslator.TranslateToBit(move.EndFile, move.EndRank);
var movedPiece = board.GetSquareContents(startSquareBit) & ~SquareContents.Colours;
Span <char> buffer = stackalloc char[8];
var lastIdx = buffer.Length - 1;
if (attackState != AttackState.None)
{
// Check if move ended in attack
var notation = GetAttackStateMoveNotation(attackState);
if (notation != 0)
{
buffer[lastIdx--] = notation;
}
}
if (movedPiece == SquareContents.King)
{
// Check for castling
var squareDiff = (decimal)startSquareBit / endSquareBit;
var castleNotation = "";
if (squareDiff == 4) // King has moved 2 squares horizontally towards queenside
{
castleNotation = "0-0-0";
}
else if (squareDiff == 0.25M) // King has moved 2 squares horizontally towards kingside
{
castleNotation = "0-0";
}
if (!string.IsNullOrEmpty(castleNotation))
{
var copyIdx = lastIdx - castleNotation.Length + 1;
var notationBuffer = buffer.Slice(copyIdx, castleNotation.Length);
castleNotation.AsSpan().CopyTo(notationBuffer);
lastIdx -= castleNotation.Length;
var copyLocation = buffer.Slice(lastIdx + 1);
return(copyLocation.ToString());
}
}
if (move.PromotedPiece != SquareContents.Empty)
{
var pieceType = move.PromotedPiece & ~SquareContents.Colours;
buffer[lastIdx--] = PiecesAsLetters[pieceType];
buffer[lastIdx--] = '=';
}
buffer[lastIdx--] = (char)(move.EndRank + '0');
buffer[lastIdx--] = move.EndFile;
var isCapture = (endSquareBit & board.AllPieces) != 0;
if (!isCapture && movedPiece == SquareContents.Pawn)
{
// Capture pattern for pawn is diagonal movement
// Explicitly checking will account for capture by en passant where end square is empty
var diff = Math.Max(startSquareBit, endSquareBit) / Math.Min(startSquareBit, endSquareBit);
isCapture = diff == 1 << 7 || diff == 1 << 9;
}
if (isCapture)
{
buffer[lastIdx--] = 'x';
}
if (movedPiece == SquareContents.Pawn)
{
if (isCapture)
{
buffer[lastIdx--] = move.StartFile;
}
}
else
{
if (movedPiece != SquareContents.King)
{
// Check for disambiguation
var colorMask = (startSquareBit & board.WhitePieces) != 0 ? board.WhitePieces : board.BlackPieces;
var pieceMask = 0UL;
if (movedPiece == SquareContents.Knight)
{
pieceMask = board.Knights;
}
else if (movedPiece == SquareContents.Bishop)
{
pieceMask = board.Bishops;
}
else if (movedPiece == SquareContents.Rook)
{
pieceMask = board.Rooks;
}
else if (movedPiece == SquareContents.Queen)
{
pieceMask = board.Queens;
}
pieceMask = pieceMask & colorMask & ~startSquareBit;
var otherPossibleStartSquares = new List <Square>();
for (var i = 0; i < 64; i++)
{
var mask = pieceMask & (1UL << i);
if (mask != 0)
{
var moves = MoveGenerator.GenerateStatelessMovesForPiece(board, mask);
if ((moves & endSquareBit) != 0)
{
otherPossibleStartSquares.Add(BitTranslator.TranslateToSquare(mask));
}
}
}
// There may be multiple possible start squares to disambiguate from
var disambiguateByRank = false;
var disambiguateByFile = false;
foreach (var otherSquare in otherPossibleStartSquares)
{
disambiguateByRank = disambiguateByRank || (otherSquare.File == move.StartFile);
disambiguateByFile = disambiguateByFile || (otherSquare.Rank == move.StartRank);
}
// Need to disambiguate, but both rank + file are different. Default to by file.
if (!disambiguateByFile && !disambiguateByRank && otherPossibleStartSquares.Count > 0)
{
disambiguateByFile = true;
}
if (disambiguateByRank)
{
buffer[lastIdx--] = (char)(move.StartRank + '0');
}
if (disambiguateByFile)
{
buffer[lastIdx--] = move.StartFile;
}
}
buffer[lastIdx--] = PiecesAsLetters[movedPiece];
}
var segment = buffer.Slice(lastIdx + 1);
return(segment.ToString());
}
public static GameState ApplyMove(GameState state, Move move, ulong startSquare, ulong endSquare)
{
var history = state.PossibleRepeatedHistory;
var resetHistory = (
((state.Board.AllPieces & endSquare) != 0) || // regular capture
((state.Board.Pawns & startSquare) != 0) // pawn movement
);
if (resetHistory)
{
history = history.Clear();
}
var newBoard = state.Board.MovePiece(startSquare, endSquare);
if ((startSquare & state.Board.Pawns) != 0)
{
if (endSquare == state.EnPassantSquare)
{
var opponentPawn = BitTranslator.TranslateToBit(move.EndFile, move.StartRank);
newBoard = BoardStateMutator.ClearPiece(newBoard, opponentPawn);
}
else if (move.PromotedPiece != SquareContents.Empty)
{
newBoard = newBoard.ClearPiece(endSquare).SetPiece(endSquare, move.PromotedPiece);
}
}
else if ((startSquare & state.Board.Kings) != 0)
{
// Castling
if (Math.Abs(move.EndFile - move.StartFile) == 2)
{
var rookDestinationRelativeKing = Math.Sign(move.StartFile - move.EndFile);
var rookDestinationFile = (char)(move.EndFile + rookDestinationRelativeKing);
var rookDestinationBit = BitTranslator.TranslateToBit(rookDestinationFile, move.EndRank);
var rookOriginFile = rookDestinationRelativeKing > 0 ? 'a' : 'h';
var rookOriginBit = BitTranslator.TranslateToBit(rookOriginFile, move.EndRank);
newBoard = BoardStateMutator.MovePiece(newBoard, rookOriginBit, rookDestinationBit);
}
}
var newPiecesStillOnStartSquare = state.PiecesOnStartSquares & ~(startSquare | endSquare);
var castlingPiecesUnmoved = newPiecesStillOnStartSquare & MoveGenerator.StartingKingsAndRooks;
var enPassantSquare = 0UL;
if ((startSquare & state.Board.Pawns) != 0)
{
if (startSquare >> 16 == endSquare)
{
enPassantSquare = startSquare >> 8;
}
else if (startSquare << 16 == endSquare)
{
enPassantSquare = startSquare << 8;
}
}
history = history.Push((newBoard, castlingPiecesUnmoved));
return(new GameState(newBoard, move, history, state.AttackState, newPiecesStillOnStartSquare, enPassantSquare, state.SquaresAttackedBy));
}