private static bool IsAttackedByPawn(
BoardSquare targetSquare,
Board board,
Player attacker)
{
var pawnAttackDeltaRow = attacker == Player.Black ? -1 : 1;
var possiblePawnRow = targetSquare.Row - pawnAttackDeltaRow;
if (possiblePawnRow < 0 || possiblePawnRow >= Board.RowCount)
{
return(false);
}
if (targetSquare.Column > 0)
{
var possiblePawnSquare = new BoardSquare(
possiblePawnRow,
targetSquare.Column - 1);
if (IsAttackerPawnAt(possiblePawnSquare, attacker, board))
{
return(true);
}
}
if (targetSquare.Column + 1 < Board.ColumnCount)
{
var possiblePawnSquare = new BoardSquare(
possiblePawnRow,
targetSquare.Column + 1);
if (IsAttackerPawnAt(possiblePawnSquare, attacker, board))
{
return(true);
}
}
return(false);
}
private static bool IsAttackerPawnAt(BoardSquare square, Player player, Board board)
{
if (board.IsEmpty(square))
{
return(false);
}
var pieceAtSquare = board.GetPieceAt(square);
return(pieceAtSquare.player == player && pieceAtSquare.piece == Piece.Pawn);
}
private static bool IsAllSquaresEmptyAlongBishopAttack(
Bitmask64 targetBishopMovesBitmask,
BoardSquare targetSquare,
BoardSquare attackerSquare,
long freeSquares)
{
long rayAttack = targetBishopMovesBitmask.Value &
GetBitmaskInBetweenRows(targetSquare.Row, attackerSquare.Row).Value &
GetBitmaskInBetweenColumns(targetSquare.Column, attackerSquare.Column).Value;
return(rayAttack == (rayAttack & freeSquares));
}
private static bool IsBishopAttack(
Bitmask64 targetBishopMovesBitmask,
BoardSquare targetSquare,
BoardSquare attackerSquare,
long freeSquares)
{
if (!IsBishopDelta(new MoveDelta(targetSquare, attackerSquare)))
{
return(false);
}
return(IsAllSquaresEmptyAlongBishopAttack(
targetBishopMovesBitmask,
targetSquare,
attackerSquare,
freeSquares));
}
private static bool IsRookAttack(
Bitmask64 targetRookMovesBitmask,
BoardSquare targetSquare,
BoardSquare attackerSquare,
long freeSquares)
{
if (targetSquare.Row == attackerSquare.Row)
{
return(IsAllSquaresEmptyAlongHorizontalAttack(
targetRookMovesBitmask,
targetSquare.Column,
attackerSquare.Column,
freeSquares));
}
else if (targetSquare.Column == attackerSquare.Column)
{
return(IsAllSquaresEmptyAlongVerticalAttack(
targetRookMovesBitmask,
targetSquare.Row,
attackerSquare.Row,
freeSquares));
}
return(false);
}
public static bool IsBoardSquareAttacked(
BoardSquare targetSquare,
Board board,
Player attacker)
{
if (IsAttackedByPawn(targetSquare, board, attacker))
{
return(true);
}
var targetBishopMovesBitmask = GetBishopBitmask(targetSquare);
var targetRookMovesBitmask = GetRookBitmask(targetSquare);
long freeSquares = ~board.OccupiedSquares.Value;
foreach (var attackingPiece in board.GetPieces(attacker))
{
switch (attackingPiece.piece)
{
case Piece.Pawn:
// Already checked
break;
case Piece.Knight:
{
if (IsKnightDelta(new MoveDelta(targetSquare, attackingPiece.square)))
{
return(true);
}
}
break;
case Piece.Bishop:
{
if (IsBishopAttack(
targetBishopMovesBitmask,
targetSquare,
attackingPiece.square,
freeSquares))
{
return(true);
}
}
break;
case Piece.Rook:
{
if (IsRookAttack(
targetRookMovesBitmask,
targetSquare,
attackingPiece.square,
freeSquares))
{
return(true);
}
}
break;
case Piece.Queen:
{
if (IsBishopAttack(
targetBishopMovesBitmask,
targetSquare,
attackingPiece.square,
freeSquares))
{
return(true);
}
if (IsRookAttack(
targetRookMovesBitmask,
targetSquare,
attackingPiece.square,
freeSquares))
{
return(true);
}
}
break;
case Piece.King:
{
if (IsKingDelta(new MoveDelta(targetSquare, attackingPiece.square)))
{
return(true);
}
}
break;
}
}
return(false);
}
private void MovePiece(BoardSquare originSquare, BoardSquare destSquare)
{
_pieceTable.MovePiece(originSquare.IntValue, destSquare.IntValue);
_occupiedSquares.UnsetBit(originSquare.IntValue);
_occupiedSquares.SetBit(destSquare.IntValue);
}
public PieceOnBoard GetPieceAt(BoardSquare square)
{
return(_pieceTable.GetPieceAt(square.IntValue));
}
public bool IsEmpty(BoardSquare square)
{
return(!_occupiedSquares.IsBitSet(square.IntValue));
}