private IEnumerable <Move> GetDoubleFrontStepMoves(Piece pawn, Board board)
{
var startPosRow = board.IsWhitesTurn ? whitePawnStartRow : blackPawnStartRow;
var isStartPos = pawn.Position.row == startPosRow;
if (!isStartPos)
{
yield break;
}
var destRow = pawn.Position.row + (board.IsWhitesTurn ? -2 : 2);
var dest = (row : destRow, pawn.Position.col);
var fieldInBetween = Avg(pawn.Position, dest);
if (board.IsEmptyAt(dest) && board.IsEmptyAt(fieldInBetween))
{
yield return(new Move(pawn.Type, MoveType.EnPassantMove, pawn.Position, dest));
}
}
private IEnumerable <Move> GetSingleFrontStepMoves(Piece pawn, Board board)
{
var destRow = pawn.Position.row + (board.IsWhitesTurn ? -1 : 1);
var dest = (row : destRow, pawn.Position.col);
if (!board.IsEmptyAt(dest))
{
yield break;
}
if (!_promotionRows.Contains(dest.row))
{
yield return(new Move(pawn.Type, MoveType.Move, pawn.Position, dest));
yield break;
}
var promotionPieceTypes = board.IsWhitesTurn ? _whitePromotionPieces : _blackPromotionPieces;
foreach (var move in promotionPieceTypes.Select(pt => new Move(pawn.Type, MoveType.Move, pawn.Position, dest, pt)))
{
yield return(move);
}
}