private void FindPawnMoves(
List <Move> moves,
ThreatMatrix threats,
Player player,
BoardLocation playerPieceLocation,
ThreatDirection?playerPieceThreatDirection)
{
var opposingPlayer = player.OpposingPlayer();
var marchDirection = player == Player.White ? Direction.North : Direction.South;
var gradeAttackDirection = player == Player.White ? Direction.NorthEast : Direction.SouthWest;
var slopeAttackDirection = player == Player.White ? Direction.NorthWest : Direction.SouthEast;
//check to see if we can move up/down
//note that any diagonal or horizontal threats will block these moves
if ((playerPieceThreatDirection.HasThreats(ThreatDirection.Horizontal | ThreatDirection.Diagonal) == false) &&
(_board.NeighboringLocationIsEmpty(playerPieceLocation, marchDirection)))
{
var firstMarchLocation = playerPieceLocation.Neighbor(marchDirection).Value;
var row = firstMarchLocation.Row();
if (row == 0 || row == 7)//we can assume this is a pawn promotion
{
moves.Add(new Move(playerPieceLocation, firstMarchLocation, SpecialMoveType.PawnPromotionKnight));
moves.Add(new Move(playerPieceLocation, firstMarchLocation, SpecialMoveType.PawnPromotionBishop));
moves.Add(new Move(playerPieceLocation, firstMarchLocation, SpecialMoveType.PawnPromotionRook));
moves.Add(new Move(playerPieceLocation, firstMarchLocation, SpecialMoveType.PawnPromotionQueen));
}
else
{
moves.Add(new Move(playerPieceLocation, firstMarchLocation));
}
//we can also move up two spaces if the next northern square is empty
if ((playerPieceLocation.IsPawnStartingLocation(player)) &&
(_board.NeighboringLocationIsEmpty(firstMarchLocation, marchDirection)))
{
moves.Add(new Move(playerPieceLocation, firstMarchLocation.Neighbor(marchDirection).Value));
}
}
//check to see if we can move along the grade
//note that any line or slope threats will block this move
if (playerPieceThreatDirection.HasThreats(ThreatDirection.Line | ThreatDirection.Slope) == false)
{
//if we have an opposing piece in the next square, make hte move
if (_board.NeighboringLocationIsOccupiedBy(playerPieceLocation, gradeAttackDirection, opposingPlayer))
{
var neighbor = playerPieceLocation.Neighbor(gradeAttackDirection).Value;
var row = neighbor.Row();
//capture pawn promotion
if (row == 0 || row == 7)
{
moves.Add(new Move(playerPieceLocation, neighbor, _board[neighbor], SpecialMoveType.PawnPromotionKnight));
moves.Add(new Move(playerPieceLocation, neighbor, _board[neighbor], SpecialMoveType.PawnPromotionBishop));
moves.Add(new Move(playerPieceLocation, neighbor, _board[neighbor], SpecialMoveType.PawnPromotionRook));
moves.Add(new Move(playerPieceLocation, neighbor, _board[neighbor], SpecialMoveType.PawnPromotionQueen));
}
else//normal capture
{
moves.Add(new Move(playerPieceLocation, neighbor, _board[neighbor]));
}
}
else if (LastMoveAllowsEnPassantFor(playerPieceLocation, gradeAttackDirection))
{//we can do an en passant.
var neighbor = playerPieceLocation.Neighbor(gradeAttackDirection).Value;
moves.Add(new Move(playerPieceLocation, neighbor, CurrentPlayer == Player.White ? ChessPiece.BlackPawn : ChessPiece.WhitePawn, SpecialMoveType.AuPassant));
}
}
//check to see if we can move along the slope
//note that any line or grade threats will block this move
if (playerPieceThreatDirection.HasThreats(ThreatDirection.Line | ThreatDirection.Grade) == false)
{
//if we have an opposing piece in the next square, make hte move
if (_board.NeighboringLocationIsOccupiedBy(playerPieceLocation, slopeAttackDirection, opposingPlayer))
{
var neighbor = playerPieceLocation.Neighbor(slopeAttackDirection).Value;
var row = neighbor.Row();
//capture pawn promotion
if (row == 0 || row == 7)
{
moves.Add(new Move(playerPieceLocation, neighbor, _board[neighbor], SpecialMoveType.PawnPromotionKnight));
moves.Add(new Move(playerPieceLocation, neighbor, _board[neighbor], SpecialMoveType.PawnPromotionBishop));
moves.Add(new Move(playerPieceLocation, neighbor, _board[neighbor], SpecialMoveType.PawnPromotionRook));
moves.Add(new Move(playerPieceLocation, neighbor, _board[neighbor], SpecialMoveType.PawnPromotionQueen));
}
else//normal capture
{
moves.Add(new Move(playerPieceLocation, neighbor, _board[neighbor]));
}
}
else if (LastMoveAllowsEnPassantFor(playerPieceLocation, slopeAttackDirection))
{//we can do an en passant.
var neighbor = playerPieceLocation.Neighbor(slopeAttackDirection).Value;
moves.Add(new Move(playerPieceLocation, neighbor, CurrentPlayer == Player.White ? ChessPiece.BlackPawn : ChessPiece.WhitePawn, SpecialMoveType.AuPassant));
}
}
}
