/// <summary>
/// Checks if it's the two-squares move.
/// </summary>
/// <param name="board">The board</param>
/// <param name="from">The starting square</param>
/// <param name="to">The ending square</param>
/// <returns></returns>
public bool IsTwoSquaresMove(Board board, int from, int to)
{
return
Board.Rank(from) == 1 && Board.Rank(to) == 3 &&
Board.File(from) == Board.File(to) &&// the same file
board[from + Board.SideSquareNo] == null && board[from + (Board.SideSquareNo << 1)] == null;// the first and second squares are empty
}
/// <summary>
/// Checks if the piece might move on this "board",
/// from the "from" square to the "to" square according to the chess rules.
/// It doesn't verify if its own king is in check after the move.
/// </summary>
/// <param name="board">The board</param>
/// <param name="from">The starting square</param>
/// <param name="to">The ending square</param>
/// <returns></returns>
public override bool MightMove(Board board, int from, int to)
{
return
base.MightMove(board, from, to) &&
Math.Abs(Board.File(from) - Board.File(to)) == Math.Abs(Board.Rank(from) - Board.Rank(to)) &&// it's a diagonal move
board.IsPathClear(from, to);// the path is clear
}
/// <summary>
/// Checks if the piece might move on this "board",
/// from the "from" square to the "to" square according to the chess rules.
/// It doesn't verify if its own king is in check after the move.
/// </summary>
/// <param name="board">The board</param>
/// <param name="from">The starting square</param>
/// <param name="to">The ending square</param>
/// <returns></returns>
public override bool MightMove(Board board, int from, int to)
{
// the first condition for a piece to be able to move
// is that starting square and the ending square be different
// and the ending square be empty or opposite piece
return from != to && !(board[to] is BlackPiece);
}
/// <summary>
/// Checks if it's the en passant move.
/// </summary>
/// <param name="board">The board</param>
/// <param name="from">The starting square</param>
/// <param name="to">The ending square</param>
/// <returns></returns>
public bool IsEnPassantCaptureMove(Board board, int from, int to)
{
return
board.Status.EnPassantTarget != null &&// there is a en passant target
to == board.Status.EnPassantTarget.Value && Board.Rank(from) == 4 && Board.Rank(board.Status.EnPassantTarget.Value) == 5 &&
Math.Abs(Board.File(from) - Board.File(to)) == 1;// it's a diagonal move
}
/// <summary>
/// Takes back the move, it doesn't check if it's a valid move
/// </summary>
/// <param name="board">The board</param>
internal override void TakeBack(Board board)
{
board.Status = before;// set the board status to the before board status
board[from] = board[to];// put the piece on the starting square
board[Target] = capture;// put back the en passant target
board[to] = null;// empty the ending square
}
/// <summary>
/// Makes the move, it doesn't check if it's a valid move
/// </summary>
/// <param name="board">The board</param>
internal override void Make(Board board)
{
capture = board[Target];// set the capture as the en passant target
board[Target] = null;// empty the en passant target square
board[to] = board[from];// put the piece on the ending square
board[from] = null;// empty the starting square
board.Status = after;// set the board status to the after board status
}
/// <summary>
/// Verifies if the piece attacks the "to" square, on this board, from the "from" square.
/// </summary>
/// <param name="board">The board</param>
/// <param name="from">The starting square</param>
/// <param name="to">The ending square</param>
/// <returns></returns>
public override bool Attacks(Board board, int from, int to)
{
// castling is not considered an attack
// so the king attacks the squares around him
return
base.MightMove(board, from, to) &&
Math.Abs(Board.Rank(from) - Board.Rank(to)) <= 1 && Math.Abs(Board.File(from) - Board.File(to)) <= 1;
}
/// <summary>
/// Checks if the piece might move on this "board",
/// from the "from" square to the "to" square according to the chess rules.
/// It doesn't verify if its own king is in check after the move.
/// </summary>
/// <param name="board">The board</param>
/// <param name="from">The starting square</param>
/// <param name="to">The ending square</param>
/// <returns></returns>
public override bool MightMove(Board board, int from, int to)
{
return
base.MightMove(board, from, to) &&
Board.File(from) != Board.File(to) &&// the files are different
Board.Rank(from) != Board.Rank(to) &&// the ranks are different
(Math.Abs(Board.File(from) - Board.File(to)) + Math.Abs(Board.Rank(from) - Board.Rank(to))) == 3;// the rank difference plus file difference must be 3
}
/// <summary>
/// Verifies if the king can castle short.
/// </summary>
/// <param name="board">The board</param>
/// <param name="from">The starting square</param>
/// <param name="to">The ending square</param>
/// <returns></returns>
public bool CanCastleShort(Board board, int from, int to)
{
return (
from == Board.E1 && to == Board.G1 &&
board.Status.WhiteCouldCastleShort &&//check if the king or the rook didn't already move
board.IsPathClear(Board.E1, Board.H1) &&// check if the path is clear
!board.IsAttackedByBlack(Board.E1) && !board.IsAttackedByBlack(Board.F1) && !board.IsAttackedByBlack(Board.G1)// check if the squares traversed by king are not attacked
);
}
/// <summary>
/// Verifies if the king can castle long.
/// </summary>
/// <param name="board">The board</param>
/// <param name="from">The starting square</param>
/// <param name="to">The ending square</param>
/// <returns></returns>
public bool CanCastleLong(Board board, int from, int to)
{
return (
from == Board.E8 && to == Board.C8 &&
board.Status.BlackCouldCastleLong &&//check if the king or the rook didn't already move
board.IsPathClear(Board.A8, Board.E8) &&// check if the path is clear
!board.IsAttackedByWhite(Board.E8) && !board.IsAttackedByWhite(Board.D8) && !board.IsAttackedByWhite(Board.C8)// check if the squares traversed by king are not attacked
);
}
/// <summary>
/// Verifies if the piece attacks the "to" square, on this board, from the "from" square.
/// </summary>
/// <param name="board">The board</param>
/// <param name="from">The starting square</param>
/// <param name="to">The ending square</param>
/// <returns></returns>
public override bool Attacks(Board board, int from, int to)
{
// a pawn attacks one square in front diagonaly
// and only if it's an empty square or an opposite side piece
return
Board.Rank(to) == Board.Rank(from) + 1 &&// it's on the front row
Math.Abs(Board.File(to) - Board.File(from)) == 1 &&// it's a diagonal move
!(board[to] is BlackPiece);// it's not occupied by a same side piece
}
/// <summary>
/// Checks if the piece might move on this "board",
/// from the "from" square to the "to" square according to the chess rules.
/// It doesn't verify if its own king is in check after the move.
/// </summary>
/// <param name="board">The board</param>
/// <param name="from">The starting square</param>
/// <param name="to">The ending square</param>
/// <returns></returns>
public override bool MightMove(Board board, int from, int to)
{
return
base.MightMove(board, from, to) &&
(
Board.File(from) == Board.File(to) ||// the same file
Board.Rank(from) == Board.Rank(to)// the same rank
) &&
board.IsPathClear(from, to);// the path is clear
}
/// <summary>
/// Checks if the piece might move on this "board",
/// from the "from" square to the "to" square according to the chess rules.
/// It doesn't verify if its own king is in check after the move.
/// </summary>
/// <param name="board">The board</param>
/// <param name="from">The starting square</param>
/// <param name="to">The ending square</param>
/// <returns></returns>
public override bool MightMove(Board board, int from, int to)
{
return
base.MightMove(board, from, to) &&
(
(Math.Abs(Board.Rank(from) - Board.Rank(to)) <= 1 && Math.Abs(Board.File(from) - Board.File(to)) <= 1) ||// the king can move one square
CanCastleLong(board, from, to) ||// the king can castle long
CanCastleShort(board, from, to)// the king can castle short
);
}
/// <summary>
/// Checks if the piece might move on this "board",
/// from the "from" square to the "to" square according to the chess rules.
/// It doesn't verify if its own king is in check after the move.
/// </summary>
/// <param name="board">The board</param>
/// <param name="from">The starting square</param>
/// <param name="to">The ending square</param>
/// <returns></returns>
public override bool MightMove(Board board, int from, int to)
{
return
base.MightMove(board, from, to) &&
(
Board.File(from) == Board.File(to) ||// the same file
Board.Rank(from) == Board.Rank(to) ||// the same rank
Math.Abs(Board.File(from) - Board.File(to)) == Math.Abs(Board.Rank(from) - Board.Rank(to))// it's a diagonal move
) &&
board.IsPathClear(from, to);
}
/// <summary>
/// Generates the move.
/// In this class, the move is not verified if it puts its own king in check.
/// This is implemented in the BlackPiece and WhitePiece subclasses.
/// </summary>
/// <param name="board">The board</param>
/// <param name="from">The starting square</param>
/// <param name="to">The ending square</param>
/// <returns></returns>
internal virtual Move GenerateMove(Board board, int from, int to)
{
if (!MightMove(board, from, to)) { return null; }
Move move = new Move(board.Status, from, to);
move.ChangeSideToMove();// change side to move
move.SetEnPassantTarget(null);// reset the en passant target
if (board[to] == null)// if there is no capture
{
move.IncrementPly();// increment the ply
}
else// if there is a capture
{
move.ResetPly();// reset the ply
// if there this moves captures a rook
// and the ending squares is one of the board corners
// reset castling availability
if (board[to] is WhiteRook)
{
if (to == Board.A1)
{
move.MakeWhiteLongCastlingUnavail();
}
else if (to == Board.H1)
{
move.MakeWhiteShortCastlingUnavail();
}
}
else if (board[to] is BlackRook)
{
if (to == Board.A8)
{
move.MakeBlackLongCastlingUnavail();
}
else if (to == Board.H8)
{
move.MakeBlackShortCastlingUnavail();
}
}
}
return move;
}
/// <summary>
/// Makes the move, it doesn't check if it's a valid move.
/// The capture must be set before making the move, othewise it throws InvalidOperationException.
/// </summary>
/// <param name="board">The board</param>
internal override void Make(Board board)
{
if (promotionPiece != null)
{
// set the ending square
board[to] = promotionPiece;
}
else
{
// if the promotion was not set throw an exception
throw new InvalidOperationException(Resources.NoPromotionMsg);
}
promotedPiece = board[from];// set the promoted piece
board[from] = null;// empty the starting square
board.Status = after;// set the board status to the after board status
}
/// <summary>
/// Checks if the piece might move on this "board",
/// from the "from" square to the "to" square according to the chess rules.
/// It doesn't verify if its own king is in check after the move.
/// </summary>
/// <param name="board">The board</param>
/// <param name="from">The starting square</param>
/// <param name="to">The ending square</param>
/// <returns></returns>
public override bool MightMove(Board board, int from, int to)
{
return
// a pawn can move one square in front to an empty square
(
to == from + Board.SideSquareNo &&// it's the front square
board[to] == null// it's an empty square
) ||
// a pawn can move one square in front diagonally if there is an opposite side piece
(
Board.Rank(to) == Board.Rank(from) + 1 &&// it's on the front row
Math.Abs(Board.File(to) - Board.File(from)) == 1 &&// it's a diagonal move
board[to] is WhitePiece// it's an opposite side piece
) ||
IsTwoSquaresMove(board, from, to) ||// it's the two-squares move
IsEnPassantCaptureMove(board, from, to);// it's the en passant move
}
/// <summary>
/// Generates the move.
/// Adds check verification to move generation,
/// returns null if its own king will be in check.
/// </summary>
/// <param name="board">The board</param>
/// <param name="from">The starting square</param>
/// <param name="to">The ending square</param>
/// <returns></returns>
internal override Move GenerateMove(Board board, int from, int to)
{
Move move = base.GenerateMove(board, from, to);
if (move != null)
{
// verify for king in check
move.Make(board);
bool result = !board.WhiteKingInCheck();
move.TakeBack(board);
return result ? move : null;
}
else
{
return null;
}
}
/// <summary>
/// Generates the move.
/// Adds check verification to move generation,
/// returns null if its own king will be in check.
/// </summary>
/// <param name="board">The board</param>
/// <param name="from">The starting square</param>
/// <param name="to">The ending square</param>
/// <returns></returns>
internal override Move GenerateMove(Board board, int from, int to)
{
Move move = base.GenerateMove(board, from, to);
if (move != null)
{
move.IncrementMoves();// the number of moves is incremented after Black moves
// verify for king in check
move.Make(board);
bool result = !board.BlackKingInCheck();
move.TakeBack(board);
return result ? move : null;
}
else
{
return null;
}
}
/// <summary>
/// Generates the move.
/// </summary>
/// <param name="board">The board</param>
/// <param name="from">The starting square</param>
/// <param name="to">The ending square</param>
/// <returns></returns>
internal override Move GenerateMove(Board board, int from, int to)
{
Move move = base.GenerateMove(board, from, to);
// just reset castling availability
if (move != null)
{
if (from == Board.A1)
{
move.MakeWhiteLongCastlingUnavail();
}
else if (from == Board.H1)
{
move.MakeWhiteShortCastlingUnavail();
}
return move;
}
else
{
return null;
}
}
/// <summary>
/// Generates the move.
/// </summary>
/// <param name="board">The board</param>
/// <param name="from">The starting square</param>
/// <param name="to">The ending square</param>
/// <returns></returns>
internal override Move GenerateMove(Board board, int from, int to)
{
Move move;
// if it's a castling move
// CanCastleLong already verifies if the king will
// end in check so we don't have to verify it again
if (CanCastleLong(board, from, to))
{
move = new CastlingMove(board.Status, Board.E1, Board.C1, new Move(board.Status, Board.A1, Board.D1));
move.ChangeSideToMove();// change side to move
move.MakeWhiteLongCastlingUnavail();// reset castling availability
move.MakeWhiteShortCastlingUnavail();// reset castling availability
move.SetEnPassantTarget(null);// reset en passant target
move.IncrementPly();// increment the ply
return move;
}
// if it's a castling move
// CanCastleShort already verifies if the king will
// end in check so we don't have to verify it again
if (CanCastleShort(board, from, to))
{
move = new CastlingMove(board.Status, Board.E1, Board.G1, new Move(board.Status, Board.H1, Board.F1));
move.ChangeSideToMove();// change side to move
move.MakeWhiteLongCastlingUnavail();// reset castling availability
move.MakeWhiteShortCastlingUnavail();// reset castling availability
move.SetEnPassantTarget(null);// reset en passant target
move.IncrementPly();// increment the ply
return move;
}
// if it's a regular move
// just reset castling availability
move = base.GenerateMove(board, from, to);
if (move != null)
{
move.MakeWhiteLongCastlingUnavail();
move.MakeWhiteShortCastlingUnavail();
return move;
}
else
{
return null;
}
}
/// <summary>
/// Gets the board FEN (Forsyth-Edwards notation).
/// </summary>
/// <param name="board">The board</param>
/// <returns></returns>
public static string GetFEN(Board board)
{
// the board must not be null
if (board == null) { throw new ArgumentNullException("board", "Resources.NullBoardMsg"); }
StringBuilder sb = new StringBuilder(80);
int emptySqNo = 0;
for (int sqIndex = 0; sqIndex < Board.SquareNo; sqIndex++)
{
// if the end of row is reached
if (sqIndex % Board.SideSquareNo == 0 && sqIndex > 0)
{
// write the number of empty squares (if any) and reset it
if (emptySqNo != 0)
{
sb.Append(emptySqNo.ToString(CultureInfo.InvariantCulture));
emptySqNo = 0;
}
sb.Append('/');// write '/'
}
//if there is a piece on this square
if (board[sqIndex] != null)
{
// write the number of empty squares (if any) and reset it
if (emptySqNo != 0)
{
sb.Append(emptySqNo.ToString(CultureInfo.InvariantCulture));
emptySqNo = 0;
}
sb.Append(pieceTypeToCharConversion[board[sqIndex].GetType()]);// write piece char representation
}
// if the square is empty
else
{
emptySqNo++;// increment the number of empty squares
}
}
// write the number of empty squares (if any)
if (emptySqNo != 0)
{
sb.Append(emptySqNo.ToString(CultureInfo.InvariantCulture));
}
sb.Append(' ').Append(board.Status.WhiteTurn ? 'w' : 'b');// write the side to move char
// write castling availability chars
if (board.Status.WhiteCouldCastleLong || board.Status.WhiteCouldCastleShort || board.Status.BlackCouldCastleLong || board.Status.BlackCouldCastleShort)
{
sb.Append(' ');
if (board.Status.WhiteCouldCastleShort) { sb.Append('K'); }
if (board.Status.WhiteCouldCastleLong) { sb.Append('Q'); }
if (board.Status.BlackCouldCastleShort) { sb.Append('k'); }
if (board.Status.BlackCouldCastleLong) { sb.Append('q'); }
}
else
{
sb.Append(' ').Append('-');
}
// write en passant target notation
sb.Append(' ').Append((board.Status.EnPassantTarget != null ? GetNotation(board.Status.EnPassantTarget.Value) : "-"));
// write ply
sb.Append(' ').Append(board.Status.Ply.ToString(CultureInfo.InvariantCulture));
// write move number
sb.Append(' ').Append(board.Status.Moves.ToString(CultureInfo.InvariantCulture));
return sb.ToString();
}
/// <summary>
/// Takes back the move, it doesn't check if it's a valid move.
/// </summary>
/// <param name="board">The board</param>
internal virtual void TakeBack(Board board)
{
board.Status = before;// set the board status to the before board status
board[from] = board[to];// put the piece on starting square
board[to] = capture;// put back the capture
}
/// <summary>
/// Computes the board hash using Zobrist method.
/// </summary>
/// <param name="board">The board</param>
/// <returns></returns>
public static int GetHash(Board board)
{
// the board must not be null
if (board == null) { throw new ArgumentNullException("board", "Resources.NullBoardMsg"); }
long hash = 0;
// loop through the squares
for (int sqIndex = 0; sqIndex < Board.SquareNo; sqIndex++)
{
// if the square is not empty
if (board[sqIndex] != null)
{
// XOR the Zobrist key which coresponds to type of piece and for this square
// to find the key index, offset the key index of the type by the square number
hash ^= zobristKeys[pieceZobristIndexTable[board[sqIndex].GetType()] + sqIndex];
}
}
// if White is to move, XOR the corresponding Zobrist key
if (board.Status.WhiteTurn)
{
hash ^= zobristKeys[Piece.TypesNo * Board.SquareNo];
}
// if the Kings could castle, the corresponding Zobrist keys
if (board.Status.WhiteCouldCastleLong)
{
hash ^= zobristKeys[Piece.TypesNo * Board.SquareNo + 1];
}
if (board.Status.WhiteCouldCastleShort)
{
hash ^= zobristKeys[Piece.TypesNo * Board.SquareNo + 2];
}
if (board.Status.BlackCouldCastleLong)
{
hash ^= zobristKeys[Piece.TypesNo * Board.SquareNo + 3];
}
if (board.Status.BlackCouldCastleShort)
{
hash ^= zobristKeys[Piece.TypesNo * Board.SquareNo + 4];
}
// if there is an en passant target, XOR the corresponding Zobrist key
if (board.Status.EnPassantTarget != null)
{
// the en passant targets have rank 2 or 5
if (Board.Rank(board.Status.EnPassantTarget.Value) == 2)
{
hash ^= zobristKeys[Piece.TypesNo * Board.SquareNo + 5 + Board.File(board.Status.EnPassantTarget.Value)];
}
else if (Board.Rank(board.Status.EnPassantTarget.Value) == 5)
{
hash ^= zobristKeys[Piece.TypesNo * Board.SquareNo + 13 + Board.File(board.Status.EnPassantTarget.Value)];
}
}
// XOR the first 4 bytes with the last 4 bytes to return an 32-bit integer
return (int)((hash & 0xFFFFFFFF) ^ (hash >> 32));
}
/// <summary>
/// Gets a board from its FEN (Forsyth-Edwards notation).
/// Throws ArgumentException if it's not a valid position.
/// </summary>
/// <param name="fen">The FEN string</param>
/// <returns></returns>
public static Board GetFENBoard(string fen)
{
try
{
// the FEN string must not be null
if (fen == null) { throw new ArgumentNullException("fen", "Resources.NullFENMsg"); }
Piece[] squares = new Piece[Board.SquareNo];
BoardStatus status = new BoardStatus();
Piece piece;
int index = 0, pos = 0;
while (fen[index] != ' ')
{
// get the piece from its char representation
piece = GetPieceFromChar(fen[index]);
// if there is a piece
if (piece != null)
{
squares[pos++] = piece;// put the piece on board
}
// if there is a number
else if (fen[index] >= '1' && fen[index] <= '8')
{
pos += fen[index] - '0';// skip empty squares
}
// if there another char than '/' throw exception
else if (fen[index] != '/')
{
throw new ArgumentException("Resources.IllegalFENFormatMsg", "fen");
}
index++;
}
index++;
// set side to move
if (fen[index] == 'w')
{
status.WhiteTurn = true;
}
else if (fen[index] == 'b')
{
status.BlackTurn = true;
}
else
{
throw new ArgumentException("Resources.IllegalFENFormatMsg", "fen");
}
index += 2;
// set castling availability
if (fen[index] == '-')
{
index++;
}
else
{
do
{
switch (fen[index])
{
case 'K':
status.WhiteCouldCastleShort = true;
break;
case 'Q':
status.WhiteCouldCastleLong = true;
break;
case 'k':
status.BlackCouldCastleShort = true;
break;
case 'q':
status.BlackCouldCastleLong = true;
break;
default:
throw new ArgumentException("Resources.IllegalFENFormatMsg", "fen");
}
}
while (fen[++index] != ' ');
}
index++;
// set en passant target
if (fen[index] == '-')
{
status.EnPassantTarget = null;
index++;
}
else
{
// checks if the square notation is correct
if (fen[index] < 'a' || fen[index] > 'h' || fen[index + 1] < '1' || fen[index + 1] > '8')
{
throw new ArgumentException("Resources.IllegalFENFormatMsg", "fen");
}
status.EnPassantTarget = GetPosition(fen[index], fen[index + 1]);
index += 2;
}
index++;
// set ply
try
{
status.Ply = Int32.Parse(fen.Substring(index, fen.IndexOf(' ', index) - index), CultureInfo.InvariantCulture);
}
catch
{
throw new ArgumentException("Resources.IllegalFENFormatMsg", "fen");
}
index = fen.IndexOf(' ', index) + 1;
// set move number
try
{
status.Moves = Int32.Parse(fen.Substring(index), CultureInfo.InvariantCulture);
}
catch
{
throw new ArgumentException("Resources.IllegalFENFormatMsg", "fen");
}
Board board = new Board(squares, status);
// verfies if the board is in valid state, throws ArgumentException if it's not
VerifyState(board);
return board;
}
// if the FEN string was too short
catch (IndexOutOfRangeException)
{
throw new ArgumentException("Resources.IllegalFENFormatMsg", "fen");
}
}
/// <summary>
/// Verifies if the piece attacks the "to" square, on this board, from the "from" square.
/// </summary>
/// <param name="board">The board</param>
/// <param name="from">The starting square</param>
/// <param name="to">The ending square</param>
/// <returns></returns>
public virtual bool Attacks(Board board, int from, int to)
{
return MightMove(board, from, to);// usually a piece attacks a square if it can move there
}
/// <summary> /// Checks if the piece might move on this "board", /// from the "from" square to the "to" square according to the chess rules. /// It doesn't verify if its own king is in check after the move. /// </summary> /// <param name="board">The board</param> /// <param name="from">The starting square</param> /// <param name="to">The ending square</param> /// <returns></returns> public abstract bool MightMove(Board board, int from, int to);
/// <summary>
/// Verifies if the board is in a valid state, throws ArgumentException if it's not.
/// </summary>
/// <param name="board">The board</param>
public static void VerifyState(Board board)
{
// the board must not be null
if (board == null) { throw new ArgumentNullException("board", "Resources.NullBoardMsg"); }
// hastable to remember the number of each piece type
// a pair consists in a piece type and the number of pieces on this board
Dictionary<Type, int> pieceNo = new Dictionary<Type, int>(Piece.TypesNo);
// initialize the values with 0
foreach (Type type in pieceZobristIndexTable.Keys) { pieceNo[type] = 0; }
// loop through the squares
for (int sqIndex = 0; sqIndex < Board.SquareNo; sqIndex++)
{
if (board[sqIndex] != null)
{
// increment the number of this piece type
Type type = board[sqIndex].GetType();
pieceNo[type] = pieceNo[type] + 1;
// check if the White Pawn has rank 1
if (type == typeof(WhitePawn) && Utils.GetRankNotation(sqIndex) == '1')
{
throw new ArgumentException("Resources.WhitePawnRank1Msg", "board");
}
// check if the Black Pawn has rank 8
if (type == typeof(BlackPawn) && Utils.GetRankNotation(sqIndex) == '8')
{
throw new ArgumentException("Resources.BlackPawnRank8Msg", "board");
}
}
}
// if there are too many White pieces
// check if the number of Pawns
// plus the number of extra Queens, Rooks, Bishops, Knights
// (which can result only by promotion) exceeds 8
if ((pieceNo[typeof(WhitePawn)] + Math.Max(pieceNo[typeof(WhiteQueen)] - 1, 0) + Math.Max(pieceNo[typeof(WhiteRook)] - 2, 0) + Math.Max(pieceNo[typeof(WhiteBishop)] - 2, 0) + Math.Max(pieceNo[typeof(WhiteKnight)] - 2, 0)) > 8)
{
throw new ArgumentException("Resources.TooManyWhitePiecesMsg", "board");
}
// if there are too many Black pieces
// check if the number of Pawns
// plus the number of extra Queens, Rooks, Bishops, Knights
// (which can result only by promotion) exceeds 8
if ((pieceNo[typeof(BlackPawn)] + Math.Max(pieceNo[typeof(BlackQueen)] - 1, 0) + Math.Max(pieceNo[typeof(BlackRook)] - 2, 0) + Math.Max(pieceNo[typeof(BlackBishop)] - 2, 0) + Math.Max(pieceNo[typeof(BlackKnight)] - 2, 0)) > 8)
{
throw new ArgumentException("Resources.TooManyBlackPiecesMsg", "board");
}
// check for White King
if (pieceNo[typeof(WhiteKing)] > 1)
{
throw new ArgumentException("Resources.MoreThanOneWhiteKingMsg", "board");
}
if (pieceNo[typeof(WhiteKing)] < 1)
{
throw new ArgumentException("Resources.NoWhiteKingMsg", "board");
}
// check for Black King
if (pieceNo[typeof(BlackKing)] > 1)
{
throw new ArgumentException("Resources.MoreThanOneBlackKingMsg", "board");
}
if (pieceNo[typeof(BlackKing)] < 1)
{
throw new ArgumentException("Resources.NoBlackKingMsg", "board");
}
// check if the King and the Rook are in place for castling availability
if (board.Status.WhiteCouldCastleShort && !(board[Board.E1] is WhiteKing && board[Board.H1] is WhiteRook))
{
throw new ArgumentException("Resources.IllegalWhiteKingShortCastlingMsg", "board");
}
// check if the King and the Rook are in place for castling availability
if (board.Status.WhiteCouldCastleLong && !(board[Board.E1] is WhiteKing && board[Board.A1] is WhiteRook))
{
throw new ArgumentException("Resources.IllegalWhiteKingLongCastlingMsg", "board");
}
// check if the King and the Rook are in place for castling availability
if (board.Status.BlackCouldCastleShort && !(board[Board.E8] is BlackKing && board[Board.H8] is BlackRook))
{
throw new ArgumentException("Resources.IllegalBlackKingShortCastlingMsg", "board");
}
// check if the King and the Rook are in place for castling availability
if (board.Status.BlackCouldCastleLong && !(board[Board.E8] is BlackKing && board[Board.A8] is BlackRook))
{
throw new ArgumentException("Resources.IllegalBlackKingLongCastlingMsg", "board");
}
// check the en passant target
if (
board.Status.EnPassantTarget != null &&
!(
(
Board.Rank(board.Status.EnPassantTarget.Value) == 5 && board.Status.BlackTurn &&// the rank of en passant target is correct
board[board.Status.EnPassantTarget.Value - Board.SideSquareNo] is WhitePawn &&// there is a pawn in front of the target
board[board.Status.EnPassantTarget.Value] == null && board[board.Status.EnPassantTarget.Value + Board.SideSquareNo] == null// the en passant target square and the one behind are empty
) ||
(
Board.Rank(board.Status.EnPassantTarget.Value) == 2 && board.Status.WhiteTurn &&// the rank of en passant target is correct
board[board.Status.EnPassantTarget.Value + Board.SideSquareNo] is BlackPawn &&// there is a pawn in front of the target
board[board.Status.EnPassantTarget.Value] == null && board[board.Status.EnPassantTarget.Value - Board.SideSquareNo] == null// the en passant target square and the one behind are empty
)
)
)
{
throw new ArgumentException("Resources.IllegalEPTargetMsg", "board");
}
// check if ply >= 0
if (board.Status.Ply < 0)
{
throw new ArgumentException("Resources.NonNegativePlyMsg", "board");
}
// check if move number >= 1
if (board.Status.Moves < 1)
{
throw new ArgumentException("Resources.PositiveMoveNoMsg", "board");
}
// check if the side which is not to move is in check
if ((board.Status.WhiteTurn && board.BlackKingInCheck()) || (board.Status.BlackTurn && board.WhiteKingInCheck()))
{
throw new ArgumentException("Resources.NoSideNotToMoveCheckMsg", "board");
}
}
/// <summary>
/// Generates the move.
/// </summary>
/// <param name="board">The board</param>
/// <param name="from">The starting square</param>
/// <param name="to">The ending square</param>
/// <returns></returns>
internal override Move GenerateMove(Board board, int from, int to)
{
Move move;
// if it's an en passant capture
if (IsEnPassantCaptureMove(board, from, to))
{
move = new EnPassantCaptureMove(board.Status, from, to);
move.ChangeSideToMove();// change the side to move
move.SetEnPassantTarget(null);// reset the en passant target
move.ResetPly();// reset the ply
move.IncrementMoves();// increment the number of moves
// we need to verify for check
move.Make(board);
bool result = !board.BlackKingInCheck();
move.TakeBack(board);
return result ? move : null;
}
move = base.GenerateMove(board, from, to);
if (move != null)
{
move.ResetPly();// reset the ply
// if it's the two-squares move
if (IsTwoSquaresMove(board, from, to))
{
// set the en passant target
move.SetEnPassantTarget(to - Board.SideSquareNo);
}
// if it's a promotion
if (Board.Rank(to) == Board.SideSquareNo - 1)
{
// we don't need to verify for check again
// so the promotion delegate will not be triggered
// later we will change the promotion type as needed
move = new PromotionMove(board.Status, from, to);
move.ChangeSideToMove();// change the side to move
move.SetEnPassantTarget(null);// reset the en passant target
move.ResetPly();// reset the ply
move.IncrementMoves();// increment the number of moves
(move as PromotionMove).SetCapture(board[to]);// the capture information is set
}
return move;
}
else
{
return null;
}
}
/// <summary>
/// Takes back the move, it doesn't check if it's a valid move.
/// </summary>
/// <param name="board">The board</param>
internal override void TakeBack(Board board)
{
board.Status = before;// set the board status to the before board status
board[from] = promotedPiece;// put the promoted piece on starting square
board[to] = capture;// put back the capture
}