private static bool CanCapture(
Color pawnColor,
Board board,
Square from, Square to)
{
// white: b2 -> a3 || c3; from.y - to.y == 1; |from.x - to.x| == 1
// black: b7 -> a6 || c6; from.y - to.y == -1; |from.x == to.x| == 1
var step = GetPawnStep(pawnColor);
return
(!board[to].IsNone() &&
MoveProperty.AbsDeltaX(from, to) == 1 &&
MoveProperty.DeltaY(from, to) == step);
}
private static bool CanForward(
Color pawnColor,
Board board,
Square from, Square to)
{
// white: a1 -> a2; from.y - to.y == 1; from.x == to.x
// black: a2 -> a1; from.y - to.y == -1; from.x == to.x
var step = GetPawnStep(pawnColor);
return
(MoveProperty.DeltaX(from, to) == 0 &&
MoveProperty.DeltaY(from, to) == step &&
board[to].IsNone());
}
private static bool CanEnPassantCapture(
ChessGame game,
Color pawnColor,
Square from, Square to)
{
if (game.EnPassantTargetSquare.IsNone())
{
return(false);
}
var step = GetPawnStep(pawnColor);
return
(to == game.EnPassantTargetSquare &&
MoveProperty.AbsDeltaX(from, to) == 1 &&
MoveProperty.DeltaY(from, to) == step);
}
private static bool CanPush(
Color pawnColor,
Board board,
Square from, Square to)
{
// white: a2 -> a4; from.y - to.y == 2; from.x == to.x
// black: a7 -> a5; from.y - to.y == -2; from.x == to.x
var row = GetPawnStartRow(pawnColor);
var step = GetPawnStep(pawnColor);
return
(row == from.Y &&
board[to].IsNone() &&
board[new Square(from.X, from.Y + step)].IsNone() &&
MoveProperty.DeltaX(from, to) == 0 &&
MoveProperty.DeltaY(from, to) == 2 * step);
}