public ValidateMoveResult CanMove(ChessBoard board, string move, PlayerTypeEnum player,
string lastMoveNotation)
{
Tuple<string, string> breakdown = NotationHelper.Breakdown(move);
string source = breakdown.Item1;
string destination = breakdown.Item2;
bool playerInCheck = IsInCheck(player, board, lastMoveNotation).Item1;
ValidateMoveResult canMoveResult = CanMove(board, source, destination, player, lastMoveNotation, playerInCheck);
if (canMoveResult.Success)
{
// pawn to queen swap
ChessPiece sourceBeforeSimulate = board.Get(source);
bool pawnSwap =
sourceBeforeSimulate != null &&
sourceBeforeSimulate.Type == PieceTypeEnum.Pawn &&
(sourceBeforeSimulate.Direction == -1 ? (int.Parse(destination[1].ToString()) == 8) : (int.Parse(destination[1].ToString()) == 1));
string swap = pawnSwap ? destination : null;
canMoveResult.Swap = swap;
ChessBoard boardAfterMove = board.SimulateMoves(move, canMoveResult.TakenPiece, swap);
// did player move into check?
var movedIntoCheckResult = IsInCheck(player, boardAfterMove, lastMoveNotation);
if (movedIntoCheckResult.Item1)
{
canMoveResult.Success = false;
return canMoveResult.SetMessage("cannot move into check.");
}
// did player put opponent in check?
var isOpponentInCheckResult = IsInCheck(GetOppositePlayer(player), boardAfterMove, lastMoveNotation);
bool isOpponentInCheck = isOpponentInCheckResult.Item1;
canMoveResult.MoveType = isOpponentInCheck ? MoveTypeEnum.Check : MoveTypeEnum.Normal;
// if player checked opponent, can opponent get out of check? if not, check mate
if (isOpponentInCheck)
{
string opponentKingNotation = boardAfterMove.GetKing(GetOppositePlayer(player));
Tuple<int, int> opponentKingTuple = NotationHelper.Translate(opponentKingNotation);
// can checked king move out of check?
bool canMoveOutOfCheck = CanMoveOutOfCheck(player, lastMoveNotation, boardAfterMove, opponentKingNotation, opponentKingTuple);
// can opponent kill piece that put king in check? is still in check afterwards?
bool canTakedownAttacker = false;
if (!canMoveOutOfCheck)
canTakedownAttacker = CanTakedownAttackers(player, lastMoveNotation, boardAfterMove, isOpponentInCheckResult.Item2);
// can block path of piece that put king in check? (brute force method)
bool canBlockPathOfAttackers = false;
if (!canMoveOutOfCheck && !canTakedownAttacker)
canBlockPathOfAttackers = CanMoveIntoAttackersPath(player, lastMoveNotation, boardAfterMove, isOpponentInCheckResult.Item2, opponentKingTuple);
if (!canMoveOutOfCheck && !canTakedownAttacker && !canBlockPathOfAttackers)
canMoveResult.MoveType = MoveTypeEnum.Checkmate;
}
}
return canMoveResult;
}
