bool CanTakeEnPassant(Checkerboard checkerboard, Pawn pawn, Pawn sidePawn, Position finalPawnPos, out Pawn sidePosPawn)
{
sidePosPawn = null;
return(pawn.Position.Digit == (pawn.PawnColor == PawnColor.White ? 4 : 3) &&
pawn.AreOppositeColor(sidePawn) &&
checkerboard.AllMoves.Last().Pawn.PawnType == PawnType.Pawn &&
checkerboard.AllMoves.Last().NewPawnPos == sidePawn.Position &&
checkerboard.IsOccupied(sidePawn.Position, out sidePosPawn) &&
!checkerboard.IsOccupied(finalPawnPos, out _));
}
public IEnumerable <Move> GetTakes(Checkerboard checkerboard, Pawn pawn)
{
Position leftPos;
Position rightPos;
Position frontLeftPos;
Position frontRightPos;
int curPawnLetter = pawn.Position.Letter;
int curPawnDigit = pawn.Position.Digit;
if (pawn.PawnColor == PawnColor.White)
{
frontLeftPos = new Position((curPawnLetter - 1), curPawnDigit + 1);
frontRightPos = new Position((curPawnLetter + 1), curPawnDigit + 1);
leftPos = new Position((curPawnLetter - 1), curPawnDigit);
rightPos = new Position((curPawnLetter + 1), curPawnDigit);
}
else
{
frontLeftPos = new Position((curPawnLetter + 1), curPawnDigit - 1);
frontRightPos = new Position((curPawnLetter - 1), curPawnDigit - 1);
leftPos = new Position((curPawnLetter - 1), curPawnDigit);
rightPos = new Position((curPawnLetter + 1), curPawnDigit);
}
if (checkerboard.IsOccupied(leftPos, out Pawn oppositeLeftPawn) && CanTakeEnPassant(checkerboard, pawn, oppositeLeftPawn, frontLeftPos, out Pawn frontLeftPawn))
{
yield return(checkerboard.GetMove(pawn, frontLeftPos, frontLeftPawn));
}
if (checkerboard.IsOccupied(rightPos, out Pawn oppositeRightPawn) && CanTakeEnPassant(checkerboard, pawn, oppositeRightPawn, frontRightPos, out Pawn frontRightPawn))
{
yield return(checkerboard.GetMove(pawn, frontRightPos, frontRightPawn));
}
if (checkerboard.IsOccupied(frontLeftPos, out Pawn frontLeftPawn1) && pawn.AreOppositeColor(frontLeftPawn1))
{
yield return(checkerboard.GetMove(pawn, frontLeftPos, frontLeftPawn1));
}
if (checkerboard.IsOccupied(frontRightPos, out Pawn frontRightPawn1) && pawn.AreOppositeColor(frontRightPawn1))
{
yield return(checkerboard.GetMove(pawn, frontRightPos, frontRightPawn1));
}
}
public static IEnumerable <Move> FindMovesAlongDirection(this Checkerboard checkerboard, Pawn pawn, Position delta)
{
var currPosition = pawn.Position + delta;
while (Checkerboard.Exists(currPosition))
{
if (checkerboard.IsOccupied(currPosition, out Pawn currPosPawn))
{
if (currPosPawn.AreOppositeColor(pawn))
{
yield return(checkerboard.GetMove(pawn, currPosition, currPosPawn));
}
break;
}
else if (checkerboard.IsEmptyButExists(currPosition))
{
yield return(checkerboard.GetMove(pawn, currPosition));
}
currPosition += delta;
}
}