// Filters out moves that would result in a check on the king.
public static void checkFilter(ref List <Tuple <uint, uint> > moves, Board board, Piece piece)
{
string colour = piece.getColour();
// Find king square
Square kingSquare = null;
for (uint j = 0; j < Board.BOARD_SIZE_Y; j++)
{
for (uint i = 0; i < Board.BOARD_SIZE_X; i++)
{
kingSquare = board.getSquareAt(i, j);
if (kingSquare.getPiece() is King &&
kingSquare.getPiece().getColour() == colour)
{
break;
}
}
if (kingSquare.getPiece() is King &&
kingSquare.getPiece().getColour() == colour)
{
break;
}
}
// Get king position
uint xKing = kingSquare.getX();
uint yKing = kingSquare.getY();
// Check if king has more than one threat
if ((colour == "white" && kingSquare.getBlackCover() > 1) ||
(colour == "black" && kingSquare.getWhiteCover() > 1))
{
moves.Clear();
}
else if ((colour == "white" && kingSquare.getBlackCover() == 1) ||
(colour == "black" && kingSquare.getWhiteCover() == 1))
{
Piece threat = null;
// Get all squares with cover of king
Piece possibleThreat;
for (uint j = 0; j < Board.BOARD_SIZE_Y; j++)
{
for (uint i = 0; i < Board.BOARD_SIZE_X; i++)
{
possibleThreat = board.getPieceAt(j, i);
if (possibleThreat != null && possibleThreat.getColour() != colour)
{
// Enemy piece, check if threat
List <Tuple <uint, uint> > cover = Rules.getCover(board, possibleThreat);
foreach (Tuple <uint, uint> t in cover)
{
if (t.Item1 == xKing && t.Item2 == yKing)
{
// Threat
threat = possibleThreat;
break;
}
}
}
if (threat != null)
{
break;
}
}
if (threat != null)
{
break;
}
}
// Remove all moves that do not resolve the check
List <Tuple <uint, uint> > tmpMoves = new List <Tuple <uint, uint> >(moves);
Piece p = threat;
if (p is Knight || p is Pawn)
{
// Must take threat
foreach (Tuple <uint, uint> move in tmpMoves)
{
if (move.Item1 != threat.getX() ||
move.Item2 != threat.getY())
{
// Will not take, remove
moves.Remove(move);
}
}
}
tmpMoves = new List <Tuple <uint, uint> >(moves);
if (p is Rook || p is Queen)
{
// Must take or block threat
foreach (Tuple <uint, uint> move in tmpMoves)
{
if (xKing == p.getX())
{
// Same x
if (!(move.Item1 == xKing && // Move will move to same x
((yKing > move.Item2 && move.Item2 >= p.getY()) || // Move will block or take when King to the right of Rook
(yKing < move.Item2 && move.Item2 <= p.getY())))) // Move will block or take when King to the left of Rook
{
// Will not block or take
moves.Remove(move);
}
}
else if (yKing == p.getY())
{
// Same y
if (!(move.Item2 == yKing && // Move will move to same y
((xKing > move.Item1 && move.Item1 >= p.getX()) || // Move will block or take when King above Rook
(xKing < move.Item1 && move.Item1 <= p.getX())))) // Move will block or take when King below Rook
{
// Will not block or take
moves.Remove(move);
}
}
}
}
tmpMoves = new List <Tuple <uint, uint> >(moves);
if ((p is Bishop || p is Queen) && !(xKing == p.getX() || yKing == p.getY()))
{
// Must take or block threat
int xMod = (xKing > p.getX() ? -1 : 1);
int yMod = (yKing > p.getY() ? -1 : 1);
// Step from King to Threat
int steps = (int)Math.Abs((int)xKing - (uint)p.getX());
foreach (Tuple <uint, uint> move in tmpMoves)
{
// Search for any blocking or taking moves
int x = (int)xKing;
int y = (int)yKing;
bool foundGoodMove = false;
for (int i = 0; i < steps; i++)
{
x += xMod;
y += yMod;
if (move.Item1 == x && move.Item2 == y)
{
foundGoodMove = true;
break;
}
}
// Remove if no good move
if (!foundGoodMove)
{
moves.Remove(move);
}
}
}
}
// ----------------------------------------------------------------------------------------
// Make sure that no new check is created by a move
if (board.getSquareAt(piece.getX(), piece.getY()).getEnemyCover(colour))
{
// Empty list of squares with cover of this square
List <Piece> threats = new List <Piece>();
// Get all squares with cover of self
Piece p;
for (uint j = 0; j < Board.BOARD_SIZE_X; j++)
{
for (uint i = 0; i < Board.BOARD_SIZE_Y; i++)
{
p = board.getPieceAt(j, i);
if (p != null && p.getColour() != colour)
{
// Remove impossible cases
if (p is King || p is Knight || p is Pawn)
{
continue;
}
// Enemy piece, check if threat
List <Tuple <uint, uint> > cover = Rules.getCover(board, p);
foreach (Tuple <uint, uint> t in cover)
{
if (t.Item1 == piece.getX() && t.Item2 == piece.getY())
{
// Threat
threats.Add(p);
}
}
}
}
}
// Check each threat for possible new check
Piece realThreat = null;
int xMod = 0, yMod = 0;
foreach (Piece threat in threats)
{
int threatX = (int)threat.getX();
int threatY = (int)threat.getY();
int x = (int)piece.getX();
int y = (int)piece.getY();
// Find relative position of the threat
if (threatX > x)
{
xMod = -1; // Threat to the right
}
else if (threatX == x)
{
xMod = 0; // Threat at same x
}
else
{
xMod = 1; // Treat to the left
}
if (threatY > y)
{
yMod = -1; // Threat above
}
else if (threatY == y)
{
yMod = 0; // Threat at same y
}
else
{
yMod = 1; // Treat below
}
// Step from self away from threat.
// If king is the first piece found, this is the real threatening piece.
Piece firstPiece;
while (true)
{
x += xMod;
y += yMod;
if (!board.withinBoard(x, y))
{
break;
}
firstPiece = board.getPieceAt((uint)x, (uint)y);
if (firstPiece != null)
{
if (firstPiece is King && firstPiece.getColour() == piece.getColour())
{
// This is the friendly king.
realThreat = threat;
}
break;
}
}
if (realThreat != null)
{
// Real threat found.
break;
}
}
// If a real new threat is found; remove any moves that do not end on the
// line between this and king.
if (realThreat != null)
{
int x = (int)realThreat.getX();
int y = (int)realThreat.getY();
List <Tuple <uint, uint> > possibleMoves = new List <Tuple <uint, uint> >();
// First get all the squares that are on a line between the threat piece and the king,
// including the threat, excluding the king.
while (true)
{
possibleMoves.Add(new Tuple <uint, uint>((uint)x, (uint)y));
x += xMod;
y += yMod;
if (x == xKing && y == yKing)
{
// End of possible moves.
break;
}
}
// Remove any moves not in possible list.
List <Tuple <uint, uint> > tmp = new List <Tuple <uint, uint> >(moves);
foreach (Tuple <uint, uint> move in tmp)
{
if (!possibleMoves.Contains(move))
{
moves.Remove(move);
}
}
}
}
}
private static void checkFilter(ref List <Tuple <uint, uint> > moves, Board board, Piece king)
{
uint kx = king.getX();
uint ky = king.getY();
List <Piece> threats = new List <Piece>();
// Make sure no new checks are created by King moving.
if (board.getSquareAt(kx, ky).getEnemyCover(king.getColour()))
{
// King is in check, get all threats
for (uint y = 0; y < Board.BOARD_SIZE_Y; y++)
{
for (uint x = 0; x < Board.BOARD_SIZE_X; x++)
{
Piece p = board.getPieceAt(x, y);
if (p != null && p.getColour() != king.getColour())
{
List <Tuple <uint, uint> > cover = Rules.getCover(board, p);
if (cover.Contains(new Tuple <uint, uint>(kx, ky)))
{
threats.Add(p);
}
}
}
}
}
foreach (Piece threat in threats)
{
if (threat is Pawn || threat is King || threat is Knight)
{
continue;
}
// Get relative position of threat
uint tx = threat.getX();
uint ty = threat.getY();
int xMod;
int yMod;
if (tx > kx)
{
xMod = -1;
}
else if (tx < kx)
{
xMod = 1;
}
else
{
xMod = 0;
}
if (ty > ky)
{
yMod = -1;
}
else if (ty < ky)
{
yMod = 1;
}
else
{
yMod = 0;
}
// Get square on the other side of king relative to the threat.
int x = (int)kx + xMod;
int y = (int)ky + yMod;
if (board.withinBoard(x, y))
{
List <Tuple <uint, uint> > tmp = new List <Tuple <uint, uint> >(moves);
foreach (Tuple <uint, uint> move in tmp)
{
if (move.Item1 == x && move.Item2 == y)
{
moves.Remove(move);
}
}
}
}
}
