private IEnumerable <ChessDraw> getForewardDraws(IChessBoard board, ChessPosition drawingPiecePosition)
{
var draws = new List <ChessDraw>();
var piece = board.GetPieceAt(drawingPiecePosition);
var coordsPosOneForeward = new Tuple <int, int>(drawingPiecePosition.Row + (piece.Color == ChessColor.White ? 1 : -1), drawingPiecePosition.Column);
var coordsPosTwoForeward = new Tuple <int, int>(drawingPiecePosition.Row + (piece.Color == ChessColor.White ? 2 : -2), drawingPiecePosition.Column);
if (ChessPosition.AreCoordsValid(coordsPosOneForeward))
{
var posOneForeward = new ChessPosition(coordsPosOneForeward);
bool oneForeward = !board.IsCapturedAt(posOneForeward);
if (oneForeward)
{
draws.Add(new ChessDraw(board, drawingPiecePosition, posOneForeward));
if (!piece.WasMoved && ChessPosition.AreCoordsValid(coordsPosTwoForeward))
{
var posTwoForeward = new ChessPosition(coordsPosTwoForeward);
if (!board.IsCapturedAt(posTwoForeward))
{
draws.Add(new ChessDraw(board, drawingPiecePosition, posTwoForeward));
}
}
}
}
return(draws);
}
private IEnumerable <ChessDraw> getRochadeDraws(IChessBoard board, ChessColor drawingSide)
{
// TODO: do optimizations!!!
// get enemy capturable positions
var enemyKing = (drawingSide == ChessColor.White) ? board.BlackKing : board.WhiteKing;
var enemyCapturablePositions =
board.GetPiecesOfColor(drawingSide.Opponent()).Where(x => x.Piece.Type != ChessPieceType.King)
.SelectMany(x => ChessDrawGenerator.Instance.GetDraws(board, x.Position, null, false)).Select(x => x.NewPosition)
.Concat(getStandardDrawPositions(enemyKing.Position));
// get the allied king and towers
int row = (drawingSide == ChessColor.White) ? 0 : 7;
var alliedKing = (drawingSide == ChessColor.White) ? board.WhiteKing : board.BlackKing;
var farAlliedTowerPos = new ChessPosition(row, 0);
var farAlliedTower = board.GetPieceAt(farAlliedTowerPos);
var nearAlliedTowerPos = new ChessPosition(row, 7);
var nearAlliedTower = board.GetPieceAt(nearAlliedTowerPos);
// define the fields that must not be capturable by the opponent
var bigRochadeKingPassagePositions = (drawingSide == ChessColor.White) ? whiteKingBigRochadePassagePositions : blackKingBigRochadePassagePositions;
var smallRochadeKingPassagePositions = (drawingSide == ChessColor.White) ? whiteKingSmallRochadePassagePositions : blackKingSmallRochadePassagePositions;
bool canBigRochade =
// check for preconditions of big rochade
(board.IsCapturedAt(farAlliedTowerPos) && !alliedKing.Piece.WasMoved && !farAlliedTower.WasMoved &&
bigRochadeKingPassagePositions.All(x => !board.IsCapturedAt(x) || (board.GetPieceAt(x).Color == drawingSide && board.GetPieceAt(x).Type == ChessPieceType.King)) &&
!board.IsCapturedAt(new ChessPosition(row, 1)))
// make sure that no rochade field can be captured by the opponent
&& !enemyCapturablePositions.Any(pos => bigRochadeKingPassagePositions.Contains(pos));
bool canSmallRochade =
// check for preconditions of small rochade
(board.IsCapturedAt(nearAlliedTowerPos) && !alliedKing.Piece.WasMoved && !nearAlliedTower.WasMoved &&
smallRochadeKingPassagePositions.All(x => !board.IsCapturedAt(x) || (board.GetPieceAt(x).Color == drawingSide && board.GetPieceAt(x).Type == ChessPieceType.King)))
// make sure that no rochade field can be captured by the opponent and the rochade field on the B-line is not captured
&& !enemyCapturablePositions.Any(pos => smallRochadeKingPassagePositions.Contains(pos));
// write result draws
int index = 0;
int drawsCount = (canSmallRochade ? 1 : 0) + (canBigRochade ? 1 : 0);
ChessDraw[] draws = new ChessDraw[drawsCount];
if (canSmallRochade)
{
draws[index++] = new ChessDraw(board, alliedKing.Position, new ChessPosition(row, 6));
}
if (canBigRochade)
{
draws[index++] = new ChessDraw(board, alliedKing.Position, new ChessPosition(row, 2));
}
return(draws);
}
/// <summary>
/// Compute whether the draw is valid or not. If it is invalid, an exception with an according message is thrown.
/// </summary>
/// <param name="board">the chess board where the draw should be applied to</param>
/// <param name="predecedingEnemyDraw">The last draw that the oponent made</param>
/// <returns>boolean whether the draw is valid</returns>
public bool IsValid(IChessBoard board, ChessDraw?predecedingEnemyDraw = null)
{
// TODO: refactor this function!!!
// get the piece to be drawn
var piece = board.GetPieceAt(OldPosition);
// make sure that there is a chess piece of the correct color that can be drawn
if (!board.IsCapturedAt(OldPosition))
{
throw new ArgumentException($"There is no chess piece on { OldPosition.FieldName }.");
}
if (piece.Color != DrawingSide)
{
throw new ArgumentException($"The chess piece on { OldPosition.FieldName } is owned by the opponent.");
}
// compute the possible chess draws for the given chess piece
var possibleDraws = ChessDrawGenerator.Instance.GetDraws(board, OldPosition, predecedingEnemyDraw, true);
// check if there is a possible draw with the same new position and type (this implies that the given draw is valid)
var type = Type;
var position = NewPosition;
bool ret = (possibleDraws?.Count() > 0) && possibleDraws.Any(x => x.Type == type && x.NewPosition == position);
return(ret);
}
private static ChessDrawType getDrawType(IChessBoard board, ChessPosition oldPos,
ChessPosition newPos, ChessPieceType?peasantPromotionType)
{
var piece = board.GetPieceAt(oldPos);
var type = ChessDrawType.Standard;
// check for a peasant promotion
if (peasantPromotionType != null && piece.Type == ChessPieceType.Peasant &&
((newPos.Row == 7 && piece.Color == ChessColor.White) ||
(newPos.Row == 0 && piece.Color == ChessColor.Black)))
{
type = ChessDrawType.PeasantPromotion;
}
// check for a rochade
else if (piece.Type == ChessPieceType.King && Math.Abs(oldPos.Column - newPos.Column) == 2)
{
type = ChessDrawType.Rochade;
}
// check for an en-passant
else if (piece.Type == ChessPieceType.Peasant && !board.IsCapturedAt(newPos) &&
Math.Abs(oldPos.Column - newPos.Column) == 1)
{
type = ChessDrawType.EnPassant;
}
return(type);
}
public void UpdatePieces(IChessBoard board)
{
for (byte pos = 0; pos < 64; pos++)
{
var field = Fields[pos];
field.UpdatePiece(board.IsCapturedAt(pos) ? (ChessPiece?)board.GetPieceAt(pos) : null);
}
_board = (IChessBoard)((ICloneable)board).Clone();
}
public ChessDraw(IChessBoard board, ChessPosition oldPos, ChessPosition newPos, ChessPieceType?peasantPromotionType = null)
{
// get the drawing piece
var piece = board.GetPieceAt(oldPos);
// determine all property values
var type = getDrawType(board, oldPos, newPos, peasantPromotionType);
var drawingSide = piece.Color;
var drawingPieceType = piece.Type;
var takenPieceType =
(type == ChessDrawType.EnPassant)
? (ChessPieceType?)ChessPieceType.Peasant
: (board.IsCapturedAt(newPos) ? (ChessPieceType?)board.GetPieceAt(newPos).Type : null);
// transform property values to a hash code
_hashCode = toHashCode(type, drawingSide, drawingPieceType, takenPieceType, peasantPromotionType, oldPos, newPos, !piece.WasMoved);
}
/// <summary>
/// Compute the field positions that can be captured by the given chess piece.
/// </summary>
/// <param name="board">The chess board representing the game situation</param>
/// <param name="drawingPiecePosition">The chess position of the chess piece to be drawn</param>
/// <param name="precedingEnemyDraw">The last draw made by the opponent</param>
/// <param name="analyzeDrawIntoCheck">Indicates whether drawing into a check situation should be analyzed</param>
/// <returns>a list of all possible chess draws</returns>
public IEnumerable <ChessDraw> GetDraws(IChessBoard board, ChessPosition drawingPiecePosition, ChessDraw?precedingEnemyDraw = null, bool analyzeDrawIntoCheck = false)
{
var piece = board.GetPieceAt(drawingPiecePosition);
// make sure the chess piece is a knight
if (piece.Type != ChessPieceType.Knight)
{
throw new InvalidOperationException("The chess piece is not a knight.");
}
// get positions next to the current position of the king (all permutations of { -1, 0, +1 }^2 except (0, 0))
var coords = new Tuple <int, int>[]
{
new Tuple <int, int>(drawingPiecePosition.Row - 2, drawingPiecePosition.Column - 1),
new Tuple <int, int>(drawingPiecePosition.Row - 2, drawingPiecePosition.Column + 1),
new Tuple <int, int>(drawingPiecePosition.Row - 1, drawingPiecePosition.Column - 2),
new Tuple <int, int>(drawingPiecePosition.Row - 1, drawingPiecePosition.Column + 2),
new Tuple <int, int>(drawingPiecePosition.Row + 1, drawingPiecePosition.Column - 2),
new Tuple <int, int>(drawingPiecePosition.Row + 1, drawingPiecePosition.Column + 2),
new Tuple <int, int>(drawingPiecePosition.Row + 2, drawingPiecePosition.Column - 1),
new Tuple <int, int>(drawingPiecePosition.Row + 2, drawingPiecePosition.Column + 1),
};
// only retrieve positions that are actually onto the chess board (and not off scale)
var positions = coords.Where(x => ChessPosition.AreCoordsValid(x)).Select(x => new ChessPosition(x));
// do not draw into positions captured by allied chess pieces
positions = positions.Where(x => !board.IsCapturedAt(x) || board.GetPieceAt(x).Color != piece.Color);
// transform positions to chess draws
var draws = positions.Select(newPos => new ChessDraw(board, drawingPiecePosition, newPos));
if (analyzeDrawIntoCheck && draws?.Count() > 0)
{
// remove draws that would draw into a check situation
draws = draws.Where(x => !ChessDrawSimulator.Instance.IsDrawIntoCheck(board, x));
}
return(draws);
}
/// <summary>
/// Make a human user put the next draw via CLI.
/// </summary>
/// <param name="board">The chess board representing the current game situation.</param>
/// <param name="previousDraw">The preceding draw made by the enemy.</param>
/// <returns>the next chess draw</returns>
public ChessDraw GetNextDraw(IChessBoard board, ChessDraw?previousDraw)
{
ChessPosition oldPosition;
ChessPosition newPosition;
ChessPieceType?promotionPieceType = null;
do
{
// get draw from user input
Console.Write("Please make your next draw (e.g. 'e2-e4): ");
string userInput = Console.ReadLine().Trim().ToLower();
// parse user input
if (userInput.Length == 5)
{
// parse coord strings
string oldPosString = userInput.Substring(0, 2);
string newPosString = userInput.Substring(3, 2);
// validate coord strings
if (ChessPosition.AreCoordsValid(oldPosString) && ChessPosition.AreCoordsValid(newPosString))
{
// init chess positions
oldPosition = new ChessPosition(oldPosString);
newPosition = new ChessPosition(newPosString);
// make sure that the player possesses the the chess piece he is moving (simple validation)
if (board.IsCapturedAt(oldPosition) && board.GetPieceAt(oldPosition).Color == Side)
{
break;
}
else
{
Console.Write("There is no chess piece to be moved onto the field you put! ");
}
}
}
else
{
Console.Write("Your input needs to be of the syntax in the example! ");
}
}while (true);
// handle peasant promotion
if (board.IsCapturedAt(oldPosition) && board.GetPieceAt(oldPosition).Type == ChessPieceType.Peasant &&
(Side == ChessColor.White && newPosition.Row == 7) || (Side == ChessColor.Black && newPosition.Row == 0))
{
do
{
// get draw from user input
Console.Write("You have put a promotion draw. Please choose the type you want to promote to (options: Bishop=B, Knight=N, Rook=R, Queen=Q): ");
string userInput = Console.ReadLine().Trim().ToLower().ToLower();
if (userInput.Length == 1)
{
switch (userInput[0])
{
case 'b': promotionPieceType = ChessPieceType.Bishop; break;
case 'n': promotionPieceType = ChessPieceType.Knight; break;
case 'r': promotionPieceType = ChessPieceType.Rook; break;
case 'q': promotionPieceType = ChessPieceType.Queen; break;
}
if (promotionPieceType == null)
{
Console.Write("Your input needs to be a letter like in the example! ");
}
}
}while (promotionPieceType == null);
}
return(new ChessDraw(board, oldPosition, newPosition, promotionPieceType));
}
private IEnumerable <ChessDraw> getCatchDraws(IChessBoard board, ChessPosition drawingPiecePosition, ChessDraw?precedingEnemyDraw = null)
{
var draws = new List <ChessDraw>();
var piece = board.GetPieceAt(drawingPiecePosition);
// get the possible chess field positions (info: right / left from the point of view of the white side player)
var coordsPosCatchLeft = new Tuple <int, int>(drawingPiecePosition.Row + (piece.Color == ChessColor.White ? 1 : -1), drawingPiecePosition.Column + 1);
var coordsPosCatchRight = new Tuple <int, int>(drawingPiecePosition.Row + (piece.Color == ChessColor.White ? 1 : -1), drawingPiecePosition.Column - 1);
// check for en-passant precondition
bool wasLastDrawPeasantDoubleForeward =
precedingEnemyDraw != null && precedingEnemyDraw.Value.DrawingPieceType == ChessPieceType.Peasant &&
Math.Abs(precedingEnemyDraw.Value.OldPosition.Row - precedingEnemyDraw.Value.NewPosition.Row) == 2;
// check if left catch / en-passant is possible
if (ChessPosition.AreCoordsValid(coordsPosCatchLeft))
{
var posCatchLeft = new ChessPosition(coordsPosCatchLeft);
bool catchLeft = board.IsCapturedAt(posCatchLeft) && board.GetPieceAt(posCatchLeft).Color != piece.Color;
if (catchLeft)
{
draws.Add(new ChessDraw(board, drawingPiecePosition, posCatchLeft));
}
if (wasLastDrawPeasantDoubleForeward)
{
// get the positions of an enemy chess piece taken by a possible en-passant
var posEnPassantEnemyLeft = new ChessPosition(drawingPiecePosition.Row, drawingPiecePosition.Column + 1);
bool isLeftFieldCapturedByEnemy =
precedingEnemyDraw.Value.NewPosition == posEnPassantEnemyLeft && board.IsCapturedAt(posEnPassantEnemyLeft) &&
board.GetPieceAt(posEnPassantEnemyLeft).Color != piece.Color;
bool enPassantLeft = isLeftFieldCapturedByEnemy && Math.Abs(posEnPassantEnemyLeft.Column - drawingPiecePosition.Column) == 1;
if (enPassantLeft)
{
draws.Add(new ChessDraw(board, drawingPiecePosition, posCatchLeft));
}
}
}
// check if right catch / en-passant is possible
if (ChessPosition.AreCoordsValid(coordsPosCatchRight))
{
var posCatchRight = new ChessPosition(coordsPosCatchRight);
bool catchRight = board.IsCapturedAt(posCatchRight) && board.GetPieceAt(posCatchRight).Color != piece.Color;
if (catchRight)
{
draws.Add(new ChessDraw(board, drawingPiecePosition, posCatchRight));
}
if (wasLastDrawPeasantDoubleForeward)
{
// get the positions of an enemy chess piece taken by a possible en-passant
var posEnPassantEnemyRight = new ChessPosition(drawingPiecePosition.Row, drawingPiecePosition.Column - 1);
bool isRightFieldCapturedByEnemy =
precedingEnemyDraw.Value.NewPosition == posEnPassantEnemyRight &&
board.IsCapturedAt(posEnPassantEnemyRight) && board.GetPieceAt(posEnPassantEnemyRight).Color != piece.Color;
bool enPassantRight = isRightFieldCapturedByEnemy && Math.Abs(posEnPassantEnemyRight.Column - drawingPiecePosition.Column) == 1;
if (enPassantRight)
{
draws.Add(new ChessDraw(board, drawingPiecePosition, posCatchRight));
}
}
}
return(draws);
}
/// <summary>
/// Compute the field positions that can be captured by the given chess piece.
/// </summary>
/// <param name="board">The chess board representing the game situation</param>
/// <param name="drawingPiecePosition">The chess position of the chess piece to be drawn</param>
/// <param name="precedingEnemyDraw">The last draw made by the opponent</param>
/// <param name="analyzeDrawIntoCheck">Indicates whether drawing into a check situation should be analyzed</param>
/// <returns>a list of all possible chess draws</returns>
public IEnumerable <ChessDraw> GetDraws(IChessBoard board, ChessPosition drawingPiecePosition, ChessDraw?precedingEnemyDraw = null, bool analyzeDrawIntoCheck = false)
{
var piece = board.GetPieceAt(drawingPiecePosition);
// make sure the chess piece is bishop-like
if (piece.Type != ChessPieceType.Bishop && piece.Type != ChessPieceType.Queen)
{
throw new InvalidOperationException("The chess piece is not a bishop.");
}
var draws = new List <ChessDraw>();
// get upper left-side draws
for (int i = 1; i < 8; i++)
{
// get position and make sure it is valid (otherwise exit loop)
var coords = new Tuple <int, int>(drawingPiecePosition.Row + i, drawingPiecePosition.Column - i);
if (!ChessPosition.AreCoordsValid(coords))
{
break;
}
var newPos = new ChessPosition(coords);
if (!board.IsCapturedAt(newPos) || board.GetPieceAt(newPos).Color != piece.Color)
{
draws.Add(new ChessDraw(board, drawingPiecePosition, newPos));
}
if (board.IsCapturedAt(newPos))
{
break;
}
}
// get lower left-side draws
for (int i = 1; i < 8; i++)
{
// get position and make sure it is valid (otherwise exit loop)
var coords = new Tuple <int, int>(drawingPiecePosition.Row - i, drawingPiecePosition.Column - i);
if (!ChessPosition.AreCoordsValid(coords))
{
break;
}
var newPos = new ChessPosition(coords);
if (!board.IsCapturedAt(newPos) || board.GetPieceAt(newPos).Color != piece.Color)
{
draws.Add(new ChessDraw(board, drawingPiecePosition, newPos));
}
if (board.IsCapturedAt(newPos))
{
break;
}
}
// get upper right-side draws
for (int i = 1; i < 8; i++)
{
// get position and make sure it is valid (otherwise exit loop)
var coords = new Tuple <int, int>(drawingPiecePosition.Row + i, drawingPiecePosition.Column + i);
if (!ChessPosition.AreCoordsValid(coords))
{
break;
}
var newPos = new ChessPosition(coords);
if (!board.IsCapturedAt(newPos) || board.GetPieceAt(newPos).Color != piece.Color)
{
draws.Add(new ChessDraw(board, drawingPiecePosition, newPos));
}
if (board.IsCapturedAt(newPos))
{
break;
}
}
// get lower right-side draws
for (int i = 1; i < 8; i++)
{
// get position and make sure it is valid (otherwise exit loop)
var coords = new Tuple <int, int>(drawingPiecePosition.Row - i, drawingPiecePosition.Column + i);
if (!ChessPosition.AreCoordsValid(coords))
{
break;
}
var newPos = new ChessPosition(coords);
if (!board.IsCapturedAt(newPos) || board.GetPieceAt(newPos).Color != piece.Color)
{
draws.Add(new ChessDraw(board, drawingPiecePosition, newPos));
}
if (board.IsCapturedAt(newPos))
{
break;
}
}
// analyze draw into a check situation
if (analyzeDrawIntoCheck && draws?.Count() > 0)
{
draws = draws.Where(draw => !ChessDrawSimulator.Instance.IsDrawIntoCheck(board, draw)).ToList();
}
return(draws);
}