private void AddDirectionalThreats(
Board board,
Player player,
BoardLocation playerKingLocation,
BoardLocation opposingPieceBoardLocation,
Direction direction,
ThreatMatrix threatMatrix)
{
//get the next square in the given direction
BoardLocation?currentLocation = opposingPieceBoardLocation.Neighbor(direction);
//for directional threats the king might be pinned...
var kingCouldBePinned = playerKingLocation.IsInGivenDirectionFrom(opposingPieceBoardLocation, direction);
var threatDirection = direction.ToThreatDirection();
while (currentLocation != null)
{
//get the piece
var piece = board[currentLocation.Value];
//as long as we are empty we can keep moving!
if (piece == ChessPiece.None)
{
//empty square, no pin possible
AddThreat(threatMatrix, playerKingLocation, opposingPieceBoardLocation, currentLocation.Value, threatDirection);
}
else
{
ThreatDirection?pinDirection = null;
//our piece which MIGHT have a pin if our king is on the same directional vector..check for it
if ((piece.BelongsTo(player)) &&
(kingCouldBePinned) &&
PieceIsPinned(board, currentLocation.Value, playerKingLocation, direction))
{
pinDirection = direction.ToThreatDirection();
}
AddThreat(
threatMatrix,
playerKingLocation,
opposingPieceBoardLocation,
currentLocation.Value,
threatDirection,
pinDirection);
//NOTE: This is a hack, but its a domain hack. From a threat perspective, we can pretend
//that the enemy king is 'invisible'. This will allow long range threats to penetrate the king
//and proceed to any columns, rows, or diagonals he is on. This in turn will help us
//when determining the kings moves by making 'backing up' an invalid strategy for him.
//without this check, a king himself would demarcate the end of a long range threat (since a piece is like a stop)
//but THAT would create the problem of making it seem like the square behind him was 'safe'. For Example:
// | | | | | | | | | |
// | |WR|BK| | To=> | |WR| |BK| would be allowed
// | | | | | | | | | |
//Where it is kind of a hack is by treating the king as invisible it means the white rook is threatening
//'beyond' a piece. Theoretically, this would then also allow it to move into those spaces, in essence just
//'hoping over' the king. This would be a HUGE problem if not for the golden rule of chess that it is impossible
//to make a move that actually captures a king. The game literally ends as soon as a board state emerges where
//a king is able to captured on the next turn. Not sure why this is, I am sure it harkens back to some
//haughty rule about how 'ignoble' it would be to ever allow the capture of a royal.
if (piece.IsKing(player) == false)
{
//short circuit search since we are done
break;
}
}
currentLocation = currentLocation.Neighbor(direction);
}
}