private bool mayKingMoveOrthogonallyHere(AttackedSquare clearMove, IEnumerable <AttackedSquare> attacksOnKing, List <AttackedSquare> attacks)
{
var kingSquare = (Square)attacksOnKing.First();
//need to detect if we're moving into check
var anybodyAttackingThisSquare = attacks.Any(a => a.Index == clearMove.Index && a.AttackingSquare.Piece.Color != kingSquare.Piece.Color);
if (anybodyAttackingThisSquare)
{
return(false);
}
//now make sure we're not ignoring the issue where an attack isn't displayed because the king was blocking the square
//that he would move into, that is still being attacked by the original attacker.
var isRankMove = GeneralEngine.GivenOrthogonalMove_IsItARankMove(clearMove.AttackingSquare.Index, clearMove.Index);
//find all attackers who attack orthogonally and determine if they are on the same line
var orthogonalAttacksOnKing = attacksOnKing.Where(a => orthogonalAttackers.Contains(a.AttackingSquare.Piece.PieceType));
foreach (var x in orthogonalAttacksOnKing)
{
var oxs = getEntireOrthogonalLine(isRankMove ? false : true, x);
//if oxs contains the clearMove.Index, then the king has not moved out of check
if (oxs.Contains(clearMove.Index))
{
return(false);
}
}
return(true);
}
/// <summary>
/// In the future, I should be passing back all the moves rather than a boolean
/// that way the engine can have metadata about all the possible moves that
/// could be taken and maybe offer a suggestion.
/// </summary>
/// <param name="attacksOnKing"></param>
/// <param name="teamAttacks"></param>
/// <returns></returns>
private bool interpositionsExist(IEnumerable <AttackedSquare> attacksOnKing, IEnumerable <AttackedSquare> teamAttacks)
{
foreach (var attackOnKing in attacksOnKing)
{
var attackIsOrthogonal = GeneralEngine.IsOrthogonal(attackOnKing.AttackingSquare.Index, attackOnKing.Index);
var attackIsDiagonal = DiagonalEngine.IsDiagonal(attackOnKing.AttackingSquare.Index, attackOnKing.Index);
var range = new List <Square>();
if (attackIsOrthogonal)
{
var isRankMove = GeneralEngine.GivenOrthogonalMove_IsItARankMove(attackOnKing.AttackingSquare.Index, attackOnKing.Index);
var oxs = getEntireOrthogonalLine(isRankMove, attackOnKing, true);
var ixs = teamAttacks.Select(a => a.Index).Intersect(oxs);
if (ixs.Any())
{
return(true);
}
}
else if (attackIsDiagonal)
{
var dxs = DiagonalEngine.GetDiagonalLine(attackOnKing.AttackingSquare.Index, attackOnKing.Index);
//if dxs contains the clearMove.Index, then the king has not moved out of check
var ixs = teamAttacks.Select(a => a.Index).Intersect(dxs);
if (ixs.Any())
{
return(true);
}
}
//else it could be a knight attack, but no interpositions would exist
}
return(false);
}
public List <AttackedSquare> GetOrthogonalLine(GameState gameState, Square square, Direction direction)
{
var attacks = new List <AttackedSquare>();
var currentPosition = square.Index;
var lineTerminator = getOrthogonalLineTerminator(direction, currentPosition);
var iterator = getIteratorByDirectionEnum(direction);
var nextPositionInTheLine = currentPosition + iterator;
for (var position = nextPositionInTheLine; position != lineTerminator; position = position + iterator)
{
var isValidCoordinate = GeneralEngine.IsValidCoordinate(position);
if (!isValidCoordinate)
{
break;
}
var moveViability = GeneralEngine.DetermineMoveViability(gameState, square.Piece, position);
//these conditions shouldn't occur
if (!moveViability.IsValidCoordinate || moveViability.SquareToAdd == null)
{
continue;
}
var attack = new AttackedSquare(square, moveViability.SquareToAdd, isProtecting: moveViability.IsTeamPiece);
attacks.Add(attack);
if (moveViability.SquareToAdd.Occupied)
{
break;
}
}
return(attacks);
}
private bool isValidKnightMove(int position, int tempPosition, int file, int rank)
{
var isValidCoordinate = GeneralEngine.IsValidCoordinate(tempPosition);
if (!isValidCoordinate)
{
return(false);
}
var tempCoord = NotationEngine.PositionToCoordinate(tempPosition);
var tempFile = NotationEngine.FileToInt(tempCoord[0]);
var tempRank = (int)tempCoord[1];
var fileDiff = Math.Abs(tempFile - file);
var rankDiff = Math.Abs(tempRank - rank);
if (fileDiff > 2 || fileDiff < 1)
{
return(false);
}
if (rankDiff > 2 || rankDiff < 1)
{
return(false);
}
return(true);
}
public void IsOrthogonal()
{
Assert.IsTrue(GeneralEngine.IsOrthogonal(0, 7));
Assert.IsTrue(GeneralEngine.IsOrthogonal(7, 0));
Assert.IsTrue(GeneralEngine.IsOrthogonal(56, 0));
Assert.IsTrue(GeneralEngine.IsOrthogonal(0, 56));
Assert.IsFalse(GeneralEngine.IsOrthogonal(0, 9));
}
private bool kingMovesExist(GameState gameState, Color kingColor, IEnumerable <AttackedSquare> attacksOnKing)
{
var opponentAttacks = gameState.Attacks.Where(a => a.AttackingSquare.Piece.Color == kingColor.Reverse()).ToList();
var kingMoves = gameState.Attacks
.Where(a =>
a.AttackingSquare.Piece.PieceType == PieceType.King &&
a.AttackingSquare.Piece.Color == kingColor &&
!a.IsProtecting
).ToList();
var clearMoves = kingMoves.Select(a => a.Index).Except(opponentAttacks.Select(b => b.Index));
if (!clearMoves.Any())
{
return(false);
}
//todo: there is a bug here: when the king is checked like so (5rk1/5pbp/5Qp1/8/8/8/5PPP/3q2K1 w - - 0 1)
//he is boxed in, but h1 looks a valid move for him because the Queen doesn't currently have it as an attack square
//because the King is blocking it.
//fix this by examining if the king is moving orthoganally or diagonally and determine if any attackers are on that line as well
var clearMoveCount = clearMoves.Count();
foreach (var clearMoveIndex in clearMoves)
{
//clearMove.AttackerSquare is the king here
//clearMove.Index is where he is going
var clearMove = kingMoves.GetSquare(clearMoveIndex);
var isOrthogonal = GeneralEngine.IsOrthogonal(clearMove.AttackingSquare.Index, clearMove.Index);
var _mayKingMoveHere = false;
if (isOrthogonal)
{
_mayKingMoveHere = this.mayKingMoveOrthogonallyHere(clearMove, attacksOnKing, gameState.Attacks);
if (!_mayKingMoveHere)
{
clearMoveCount--;
}
}
else
{
//has to be diagonal
_mayKingMoveHere = this.mayKingMoveDiagonallyHere(clearMove, attacksOnKing, gameState.Attacks);
if (!_mayKingMoveHere)
{
clearMoveCount--;
}
}
}
return(clearMoveCount > 0);
}
private static (bool IsValid, bool CanAttackOccupyingPiece) basicMoveValidity(Color pieceColor, Square square)
{
if (!square.Occupied)
{
// go for it
return(true, true);
}
// if it is your teammate, you can't do that
if (GeneralEngine.IsTeamPiece(pieceColor, square.Piece))
{
return(true, true);
}
else
{
return(true, false);
}
}
private void getKnightAttacks(GameState gameState, Square square, List <AttackedSquare> accumulator)
{
var squares = gameState.Squares;
var currentPosition = square.Index;
var pieceColor = square.Piece.Color;
var attacks = new List <AttackedSquare>();
var coord = NotationEngine.PositionToCoordinate(currentPosition);
var file = NotationEngine.FileToInt(coord[0]);
var rank = (int)coord[1];
var potentialPositions = new List <int> {
6, 10, 15, 17, -6, -10, -15, -17
};
foreach (var potentialPosition in potentialPositions)
{
var position = currentPosition + potentialPosition;
var _isValidKnightMove = isValidKnightMove(currentPosition, position, file, rank);
var _isValidMove = isValidMove(accumulator, gameState, square, position, pieceColor);
var _isValidCoordinate = GeneralEngine.IsValidCoordinate(position);
if (!_isValidKnightMove || !_isValidMove.IsValid || !_isValidCoordinate)
{
continue;
}
var attackedSquare = squares.GetSquare(position);
if (!attackedSquare.Occupied)
{
attacks.Add(new AttackedSquare(square, attackedSquare));
}
else
{
attacks.Add(new AttackedSquare(square, attackedSquare, isProtecting: attackedSquare.Piece.Color == pieceColor));
}
}
if (attacks.Any())
{
accumulator.AddRange(attacks);
}
}
public List <int> GetEntireRank(int rank)
{
return(GeneralEngine.GetEntireRank(rank));
}
public List <int> GetEntireFile(int file)
{
return(GeneralEngine.GetEntireFile(file));
}
private void getKingAttacks(GameState gameState, Square square, List <AttackedSquare> accumulator)
{
var attacks = new List <AttackedSquare>();
var squares = gameState.Squares;
var offsets = getKingOffsets(square.Index);
var pieceColor = square.Piece.Color;
foreach (var offset in offsets)
{
var destinationPosition = square.Index + offset;
var isValidCoordinate = GeneralEngine.IsValidCoordinate(destinationPosition);
if (!isValidCoordinate)
{
continue;
}
var _isValidMove = isValidMove(accumulator, gameState, square, destinationPosition, pieceColor);
if (!_isValidMove.IsValid)
{
continue;
}
attacks.Add(
new AttackedSquare(square, squares.GetSquare(destinationPosition), isProtecting: !_isValidMove.CanAttackOccupyingPiece)
);
}
//*********************
//castling stuff
//*********************
var castleAvailability = gameState.CastlingAvailability;
if (pieceColor == Color.White)
{
if (castleAvailability.Contains("K"))
{
addCastleAttackIfPossible(
square,
attacks,
squares,
7,
new List <int> {
5, 6
},
6
);
}
if (castleAvailability.Contains("Q"))
{
addCastleAttackIfPossible(
square,
attacks,
squares,
0,
new List <int> {
1, 2, 3
},
2
);
}
}
else if (pieceColor == Color.Black)
{
if (castleAvailability.Contains("k"))
{
addCastleAttackIfPossible(
square,
attacks,
squares,
63,
new List <int> {
61, 62
},
62
);
}
if (castleAvailability.Contains("q"))
{
addCastleAttackIfPossible(
square,
attacks,
squares,
56,
new List <int> {
57, 58, 59
},
58
);
}
}
//*********************
//end castling stuff
//*********************
if (!attacks.Any())
{
return;
}
accumulator.AddRange(attacks);
}
private (bool IsValid, bool CanAttackOccupyingPiece) isValidMove(List <AttackedSquare> attacks, GameState gameState, Square locationSquare, int destination, Color pieceColor)
{
var isValidCoordinate = GeneralEngine.IsValidCoordinate(destination);
if (!isValidCoordinate || !gameState.Squares.Any(a => a.Index == destination))
{
// throw new Exception($"Invalid position passed: { position }");
// probably doing this just as an easy way to not have to trim squares from every algorithm
return(false, false);
}
var destinationSquare = gameState.Squares.GetSquare(destination);
// if you're not a king you've got simpler rules
// but if you're the king, you still have to obey the basics
var basics = basicMoveValidity(pieceColor, destinationSquare);
if (locationSquare.Piece.PieceType != PieceType.King || !basics.CanAttackOccupyingPiece)
{
return(basics);
}
// check to make sure that this move would get us out of check
var newPositionAttacks = attacks.Where(a => a.Index == destination && a.AttackingSquare.Piece.Color != locationSquare.Piece.Color);
if (newPositionAttacks.Any())
{
// king can't move into check
return(true, false);
}
// no-one is attacking the destination that we can tell, let's make sure
// piece currently being attacked?
var attacksOnThisPosition = attacks.Where(a => a.Index == locationSquare.Index && a.AttackingSquare.Piece.Color != locationSquare.Piece.Color);
if (!attacksOnThisPosition.Any())
{
// nobody is attacking this king now, or in the new position
return(true, true);
}
var dangerSquares = attacksOnThisPosition.Where(a => _dangerPieceTypes.Contains(a.AttackingSquare.Piece.PieceType) && a.AttackingSquare.Piece.Color != locationSquare.Piece.Color);
if (!dangerSquares.Any())
{
// nobody dangerous is attacking this king now, or in the new position
return(true, true);
}
// which direction are we moving?
var directionInfo = GeneralEngine.GetDirectionInfo(locationSquare.Index, destination);
var directionalDangerPieceTypes = directionInfo.IsDiagonal ? _diagonalDangerPieceTypes : _orthogonalFangerPieceTypes;
var directionalDangerSquares = attacksOnThisPosition.Where(a => directionalDangerPieceTypes.Contains(a.AttackingSquare.Piece.PieceType) && a.AttackingSquare.Piece.Color != locationSquare.Piece.Color);
foreach (var dangerSquare in directionalDangerSquares)
{
// is that going to get us out of the attack path that this piece would normally have?
var dangerPieceDirectionInfo = GeneralEngine.GetDirectionInfo(dangerSquare.AttackingSquare.Index, locationSquare.Index);
if (dangerPieceDirectionInfo.IsDiagonal && directionInfo.IsOrthogonal)
{
// won't intersect paths
continue;
}
if (dangerPieceDirectionInfo.IsOrthogonal && directionInfo.IsDiagonal)
{
// won't intersect paths
continue;
}
if (dangerPieceDirectionInfo.IsDiagonal && directionInfo.IsDiagonal)
{
// are we moving on the same diagonal plane?
if (dangerPieceDirectionInfo.DiagonalDirection == directionInfo.DiagonalDirection)
{
// not safe
return(false, false);
}
}
if (dangerPieceDirectionInfo.IsOrthogonal && directionInfo.IsOrthogonal)
{
// are we moving on the same orthogonal plane?
if (dangerPieceDirectionInfo.Direction == directionInfo.Direction)
{
// not safe
return(false, false);
}
}
}
// safe
return(true, true);
}
