private void AddPawnMoves(IList <Move> moves, bool onlyCaptures)
{
var pawnDirection = board.Us == Piece.WHITE ? Directions[N] : Directions[S];
var promotionRank = board.Us == Piece.WHITE ? 7 : 0;
//one square moves
var ourPawnsBitboard = board.Us == Piece.WHITE ? board.WhitePawnBitboard : board.BlackPawnBitboard;
var pinnedPawns = pinBitmask & ourPawnsBitboard;
if (!onlyCaptures)
{
var pseudoLegalSinglePawnMoveTargets = board.Us == Piece.WHITE ? BitboardUtilities.ShiftUp(ourPawnsBitboard) : BitboardUtilities.ShiftDown(ourPawnsBitboard);
pseudoLegalSinglePawnMoveTargets &= freeSquares;
var legalSinglePawnMoveTarget = pseudoLegalSinglePawnMoveTargets & rayCheckBitmask;
while (legalSinglePawnMoveTarget != 0)
{
var targetSquare = BitOperations.TrailingZeroCount(legalSinglePawnMoveTarget);
var startSquare = targetSquare - pawnDirection;
legalSinglePawnMoveTarget ^= 1ul << targetSquare;
if ((pinnedPawns & (1ul << startSquare)) != 0 && !IsMovingAlongRay(pawnDirection, startSquare, ourKingSquare))
{
continue;
}
if (targetSquare / 8 == promotionRank)
{
moves.Add(new Move(startSquare, targetSquare, board).PromoteTo(Piece.QUEEN));
moves.Add(new Move(startSquare, targetSquare, board).PromoteTo(Piece.ROOK));
moves.Add(new Move(startSquare, targetSquare, board).PromoteTo(Piece.BISHOP));
moves.Add(new Move(startSquare, targetSquare, board).PromoteTo(Piece.KNIGHT));
}
else
{
moves.Add(new Move(startSquare, targetSquare, board));
}
}
var doublePawnMoveTarget = board.Us == Piece.WHITE ? BitboardUtilities.ShiftUp(pseudoLegalSinglePawnMoveTargets) : BitboardUtilities.ShiftDown(pseudoLegalSinglePawnMoveTargets);
doublePawnMoveTarget &= RankBitboards[board.Us == Piece.WHITE ? 3 : 4] & freeSquares & rayCheckBitmask;
while (doublePawnMoveTarget != 0)
{
var targetSquare = BitOperations.TrailingZeroCount(doublePawnMoveTarget);
var startSquare = targetSquare - 2 * pawnDirection;
doublePawnMoveTarget ^= 1ul << targetSquare;
if ((pinnedPawns & (1ul << startSquare)) != 0)
{
if (!IsMovingAlongRay(pawnDirection, startSquare, ourKingSquare))
{
continue;
}
}
moves.Add(new Move(startSquare, targetSquare, board).DoublePawnMove());
}
}
//Captures
var upWest = Directions[board.Us == Piece.WHITE ? NW : SW];
var upEast = Directions[board.Us == Piece.WHITE ? NE : SE];
var enemyPiecesAndEnPassent = board.EnPassentSquare >= 0 ? enemyPieces | (1ul << board.EnPassentSquare) : enemyPieces;
var captureUpWestTargets = board.Us == Piece.WHITE ? BitboardUtilities.ShiftUpLeft(ourPawnsBitboard) : BitboardUtilities.ShiftDownLeft(ourPawnsBitboard);
captureUpWestTargets &= enemyPiecesAndEnPassent & rayCheckBitmask;
var captureUpEastTargets = board.Us == Piece.WHITE ? BitboardUtilities.ShiftUpRight(ourPawnsBitboard) : BitboardUtilities.ShiftDownRight(ourPawnsBitboard);
captureUpEastTargets &= enemyPiecesAndEnPassent & rayCheckBitmask;
while (captureUpWestTargets != 0)
{
var targetSquare = BitOperations.TrailingZeroCount(captureUpWestTargets);
var startSquare = targetSquare - upWest;
captureUpWestTargets ^= 1ul << targetSquare;
if ((pinnedPawns & (1ul << startSquare)) != 0 && !IsMovingAlongRay(upWest, startSquare, ourKingSquare))
{
continue;
}
if (targetSquare / 8 == promotionRank)
{
moves.Add(new Move(startSquare, targetSquare, board).PromoteTo(Piece.QUEEN));
moves.Add(new Move(startSquare, targetSquare, board).PromoteTo(Piece.ROOK));
moves.Add(new Move(startSquare, targetSquare, board).PromoteTo(Piece.BISHOP));
moves.Add(new Move(startSquare, targetSquare, board).PromoteTo(Piece.KNIGHT));
}
else
{
var move = new Move(startSquare, targetSquare, board);
if (targetSquare == board.EnPassentSquare)
{
move.EnPassent();
}
moves.Add(move);
}
}
while (captureUpEastTargets != 0)
{
var targetSquare = BitOperations.TrailingZeroCount(captureUpEastTargets);
var startSquare = targetSquare - upEast;
captureUpEastTargets ^= 1ul << targetSquare;
if ((pinnedPawns & (1ul << startSquare)) != 0 && !IsMovingAlongRay(upEast, startSquare, ourKingSquare))
{
continue;
}
if (targetSquare / 8 == promotionRank)
{
moves.Add(new Move(startSquare, targetSquare, board).PromoteTo(Piece.QUEEN));
moves.Add(new Move(startSquare, targetSquare, board).PromoteTo(Piece.ROOK));
moves.Add(new Move(startSquare, targetSquare, board).PromoteTo(Piece.BISHOP));
moves.Add(new Move(startSquare, targetSquare, board).PromoteTo(Piece.KNIGHT));
}
else
{
var move = new Move(startSquare, targetSquare, board);
if (targetSquare == board.EnPassentSquare)
{
move.EnPassent();
}
moves.Add(move);
}
}
}
