private static Move DetermineMove(Board board, UCIChessMove uciMove)
{
string from = uciMove.From;
string to = uciMove.To;
var fromPos = Position.Parse(from);
var toPos = Position.Parse(to);
var fromPiece = board[fromPos];
int fileDiff = Math.Abs((int)fromPiece.Position.File - (int)toPos.File);
if (fromPiece.Type == PieceType.King && (fileDiff == 3 || fileDiff == 4))
{
King king = (King)fromPiece;
Rook rook;
if (fileDiff == 4)
{
rook = (Rook)board[File.A, fromPiece.Position.Rank];
}
else
{
rook = (Rook)board[File.H, fromPiece.Position.Rank];
}
return(MoveBuilder.CreateCastleMove(king, rook));
}
if (uciMove.PromotionChar != null)
{
string promotionChar = uciMove.PromotionChar.ToUpper();
var promotionType = (from p in (PieceType[])Enum.GetValues(typeof(PieceType))
where p.ToNotationLetter().ToUpper() == promotionChar.ToUpper()
select p).First();
var promotionMoves = MoveBuilder.CreatePromotionMoves((Pawn)fromPiece, toPos, board[toPos] != null);
return((from m in promotionMoves
where m.Promotion.NewPieceType.Type == promotionType
select m).First());
}
// Check for en passant
var existingPieceRank = fromPiece.Position.Rank;
var isCorrectRank = fromPiece.Color == PieceColor.Black ? existingPieceRank == Rank._4 : existingPieceRank == Rank._5;
try
{
int vertDir = fromPiece.Color == PieceColor.White ? -1 : 1;
var existingPieceTo = board[toPos];
var capturedPiecePos = toPos.MoveVert(vertDir);
var capturedPiece = board[capturedPiecePos];
if (capturedPiece.Color == fromPiece.Color.Opposite() &&
capturedPiece.MoveHistory.Count == 1)
{
// This is an en passant
return(MoveBuilder.CreateEnPassantMove((Pawn)fromPiece, toPos, capturedPiecePos));
}
}
catch { }
// Only other option is that this is a normal move.
return(MoveBuilder.CreateNormalMove(fromPiece, toPos, board[toPos] != null));
}
private List <Move> GetEnPassantMoves(Board board)
{
var enPassantMoves = new List <Move>();
// Is the pawn in the right rank?
if (Color == PieceColor.Black && Position.Rank != Rank._4)
{
return(new List <Move>());
}
if (Color == PieceColor.White && Position.Rank != Rank._5)
{
return(new List <Move>());
}
// Create a few KVP of Key = new position and value = piece to capture position
var positions = new List <KeyValuePair <Position, Position> >();
if ((int)Position.File >= (int)File.B)
{
positions.Add(
new KeyValuePair <Position, Position>(
Position.MoveVert(IncrementDirection).MoveHoriz(-1),
Position.MoveHoriz(-1)));
}
if ((int)Position.File <= (int)File.G)
{
positions.Add(
new KeyValuePair <Position, Position>(
Position.MoveVert(IncrementDirection).MoveHoriz(1),
Position.MoveHoriz(1)));
}
foreach (var kvp in positions)
{
var newPos = kvp.Key;
var capturePos = kvp.Value;
// There has to be an enemy piece there
var pieceToCapture = board[capturePos];
if (pieceToCapture == null ||
pieceToCapture.Color == this.Color)
{
continue;
}
// The piece must have made a pawn advances 2 move.
if (pieceToCapture.MoveHistory == null ||
pieceToCapture.MoveHistory.Count != 1)
{
continue;
}
// The move must be the most recently played move in the game.
var pieceToCaptureLastMove = pieceToCapture.MoveHistory.Last();
if (pieceToCaptureLastMove != board.LastMove)
{
continue;
}
// We have a candidate for en passant!
enPassantMoves.Add(MoveBuilder.CreateEnPassantMove(this, newPos, capturePos));
}
return(enPassantMoves);
}