using Chess;
using Chess.Utilities;
using Chess.MoveGen;
using Chess.Bitmasks;
using Types.Nibble;
using Types.Bitboards;
using Chess960.Castling;
namespace Chess960
{
public class Board960
{
public Piece[] BoardArray;
public PieceSet White;
public PieceSet Black;
public int moveCounter;
public uint halfMoveClock;
public Nibble castlingRights; // 0b1111 => KQkq
public Stack<Move> moveHistory = new();
public Stack<BoardInfo> boardHistory = new();
public Bitboard pinHV;
public Bitboard pinD;
public Bitboard checkmask;
public Bitboard checkers;
public Bitboard boardMask { get { return White.Mask | Black.Mask; } }
public string FEN { get { return GetFEN(); } }
public int SideToMove { get { return moveCounter & 1; } }
public Colour ColourToMove { get { return (Colour)SideToMove; } }
public PieceSet PlayerToMove { get { return SideToMove == 0 ? White : Black; } }
public PieceSet OpponentToMove { get { return SideToMove == 0 ? Black : White; }}
public Bitboard epSquare;
public int[] rookStarts = [-1, -1, -1, -1];
public Board960(string? FEN = null)
{
// If a FEN wasn't presented, read the list of all FENs and pick a random one
FEN ??= File.ReadAllText("fen960.txt").Split('\n')[new Random().Next() % 960];
// Create piece sets for each side
White = new(Colour.White);
Black = new(Colour.Black);
// Split the FEN string into sections
string[] FENstringSections = FEN.Split(' ');
// Assign variables to each of the sections
string boardFEN = FENstringSections[0];
string sideToMoveString = FENstringSections[1];
string FENcastlingRights = FENstringSections[2];
string epSquareString = FENstringSections[3];
string halftimeCounter = FENstringSections[4];
string currentDoubleMove = FENstringSections[5];
// Reverse FEN string to have a reversed board format
boardFEN = string.Join("/", boardFEN.Split('/').Reverse());
// Fill the board with pieces based on the FEN string
BoardArray = new Piece[64];
Array.Fill(BoardArray, Piece.Empty);
int cursor = 0;
// Fill the board with ecah character
foreach (char c in boardFEN)
{
// Skip these because we don't use a 2D array
if (c == '/') continue;
// If the current character is a number (eg. N)
if (int.TryParse(c.ToString(), out int emptySpaces))
{
// Add N empty spaces to the
for (int i = 0; i < emptySpaces; i++)
{
BoardArray[cursor++] = Piece.Empty;
}
// cursor += emptySpaces; // Keep cursor updated
continue;
}
// Pattern match each character in the FEN string to its
// relative Piece enum to be inserted into the board.
BoardArray[cursor] = c switch
{
'b' => Piece.BlackBishop,
'n' => Piece.BlackKnight,
'r' => Piece.BlackRook,
'q' => Piece.BlackQueen,
'p' => Piece.BlackPawn,
'k' => Piece.BlackKing,
'B' => Piece.WhiteBishop,
'N' => Piece.WhiteKnight,
'R' => Piece.WhiteRook,
'Q' => Piece.WhiteQueen,
'K' => Piece.WhiteKing,
'P' => Piece.WhitePawn,
_ => throw new Exception($"invalid character '{c}' found in FEN string.")
};
// Pattern match each character in the FEN string to the bitboard
// to insert a bit into, using the cursor argument.
var _ = c switch
{
'b' => Black.Bishops |= 1UL << cursor,
'n' => Black.Knights |= 1UL << cursor,
'r' => Black.Rooks |= 1UL << cursor,
'q' => Black.Queens |= 1UL << cursor,
'k' => Black.King |= 1UL << cursor,
'p' => Black.Pawns |= 1UL << cursor,
'B' => White.Bishops |= 1UL << cursor,
'N' => White.Knights |= 1UL << cursor,
'R' => White.Rooks |= 1UL << cursor,
'Q' => White.Queens |= 1UL << cursor,
'K' => White.King |= 1UL << cursor,
'P' => White.Pawns |= 1UL << cursor,
_ => throw new Exception($"invalid character '{c}' found in FEN string.")
};
// Increase the cursor to the new position
cursor++;
}
// Set move counter based on side to move and current double move
int sideToMoveIncrease = sideToMoveString switch
{
"w" => 0, "b" => 1,
_ => throw new Exception($"invalid side to move character.")
};
if (!int.TryParse(currentDoubleMove, out int currentDoubleMoveNumber))
{
throw new Exception($"invalid current move character.");
}
moveCounter = currentDoubleMoveNumber * 2 + sideToMoveIncrease;
// Set castling rights
castlingRights = 0;
static int convBool(bool x) => x ? 1 : 0;
if (FENcastlingRights != "-")
{
foreach (char right in FENcastlingRights)
{
bool isWhite = char.IsUpper(right);
int kingPos = isWhite ? White.KingSquare : Black.KingSquare;
int rookPos = isWhite ? right - 'A' : 56 + right - 'a';
int index = convBool(rookPos < kingPos) + 2 * convBool(!isWhite);
rookStarts[index] = rookPos;
castlingRights |= 1 << 3 - index;
}
}
// Set the halftime counter
if (!uint.TryParse(halftimeCounter, out uint HTC))
{
throw new Exception("half time counter was not a positive integer.");
}
halfMoveClock = HTC;
// Set an en-passant square
if (epSquareString != "-")
{
int rank = "12345678".IndexOf(epSquareString[1]);
int file = "abcdefgh".IndexOf(epSquareString[0]);
int epSquareIndex = rank * 8 + file;
epSquare = 1UL << epSquareIndex;
}
UpdatePinsAndCheckers();
}
public Bitboard GetBitboardFromEnum(Piece pieceEnum)
{
Move getLastMovePlayed()
{
var T = moveHistory.Pop();
moveHistory.Push(T);
return T;
}
return pieceEnum switch
{
Piece.BlackBishop => Black.Bishops,
Piece.BlackKnight => Black.Knights,
Piece.BlackKing => Black.King,
Piece.BlackQueen => Black.Queens,
Piece.BlackRook => Black.Rooks,
Piece.BlackPawn => Black.Pawns,
Piece.WhiteBishop => White.Bishops,
Piece.WhiteKnight => White.Knights,
Piece.WhitePawn => White.Pawns,
Piece.WhiteQueen => White.Queens,
Piece.WhiteRook => White.Rooks,
Piece.WhiteKing => White.King,
Piece.Empty => throw new Exception($"cannot obtain bitboard for an empty piece on move {getLastMovePlayed()}.\nBoard:\n{this}\n\nBitboards:\n{Display.StringifyMultipleBitboards([White.King, White.Rooks])}\n\nMove history: [{string.Join(", ", moveHistory.Reverse())}]\n\nPerhaps your start square is wrong?\n"),
_ => throw new Exception($"cannot set bitboard for unaccounted enum \"{pieceEnum}\".") // raised errors if not in place
};
}
public void SetBitboardFromEnum(Piece pieceEnum, Bitboard bitboard)
{
var _ = pieceEnum switch
{
Piece.BlackBishop => Black.Bishops = bitboard,
Piece.BlackKnight => Black.Knights = bitboard,
Piece.BlackKing => Black.King = bitboard,
Piece.BlackQueen => Black.Queens = bitboard,
Piece.BlackRook => Black.Rooks = bitboard,
Piece.BlackPawn => Black.Pawns = bitboard,
Piece.WhiteBishop => White.Bishops = bitboard,
Piece.WhiteKnight => White.Knights = bitboard,
Piece.WhitePawn => White.Pawns = bitboard,
Piece.WhiteQueen => White.Queens = bitboard,
Piece.WhiteRook => White.Rooks = bitboard,
Piece.WhiteKing => White.King = bitboard,
Piece.Empty => throw new Exception($"cannot set bitboard for an empty piece enum."),
_ => throw new Exception($"cannot set bitboard for unaccounted enum \"{pieceEnum}\".") // raised errors if not in place
};
}
public void MakeMove(Move move)
{
// Archive move
moveHistory.Push(move);
moveCounter++;
Piece pieceCaptured;
// Board info for archiving
BoardInfo boardInfo = new()
{
EPsquare = epSquare,
castlingRights = castlingRights,
checkmask = checkmask,
pinHV = pinHV,
pinD = pinD
};
// Modify the board based on the type of move played
switch (move.type)
{
case MoveType.Normal:
Piece pieceToMove = BoardArray[move.src];
// Handle disabling castling rights when moving kings or rooks
switch (pieceToMove)
{
case Piece.WhiteKing: // Remove white castling rights
castlingRights &= ~0b1100;
break;
case Piece.BlackKing:
castlingRights &= ~0b0011;
break;
case Piece.WhiteRook:
if (move.src == rookStarts[1]) castlingRights &= ~0b0100; // starting leftside rook position
if (move.src == rookStarts[0]) castlingRights &= ~0b1000; // starting rightside rook position
break;
case Piece.BlackRook:
if (move.src == rookStarts[3]) castlingRights &= ~0b0001; // starting leftside rook position
if (move.src == rookStarts[2]) castlingRights &= ~0b0010; // starting rightside rook position
break;
default:
break;
}
// Update piece bitboard
Bitboard bb = GetBitboardFromEnum(pieceToMove);
bb ^= 1UL << move.src | 1UL << move.dst;
SetBitboardFromEnum(pieceToMove, bb);
// Check if piece was a capture
if (BoardArray[move.dst] != Piece.Empty)
{
// Get the piece that was captured
pieceCaptured = BoardArray[move.dst];
// If the piece captured was a rook, remove castling rights
// for whatever side it was taken from
if (pieceCaptured == Piece.WhiteRook)
{
if (move.dst == 0) castlingRights &= ~0b0100;
if (move.dst == 7) castlingRights &= ~0b1000;
}
if (pieceCaptured == Piece.BlackRook)
{
if (move.dst == 56) castlingRights &= ~0b0001;
if (move.dst == 63) castlingRights &= ~0b0010;
}
// Update the captured piece's bitboard
bb = GetBitboardFromEnum(pieceCaptured);
bb ^= 1UL << move.dst;
SetBitboardFromEnum(pieceCaptured, bb);
boardInfo.capturedPiece = pieceCaptured;
}
// Update board array
BoardArray[move.src] = Piece.Empty;
BoardArray[move.dst] = pieceToMove;
// Clear en-passant square
epSquare = 0;
break;
case MoveType.EnPassant:
pieceToMove = BoardArray[move.src];
// Update bitboard of piece
bb = GetBitboardFromEnum(pieceToMove);
bb ^= 1UL << move.src | 1UL << move.dst;
SetBitboardFromEnum(pieceToMove, bb);
// Get square of pawn to capture
int inFrontOfEPsquare = move.dst - 8 * (move.src > move.dst ? 1 : -1);
Piece opponentPawnType = BoardArray[inFrontOfEPsquare];
// Remove pawn from bitboard and update it
Bitboard opponentPawnBB = GetBitboardFromEnum(opponentPawnType);
opponentPawnBB ^= 1UL << inFrontOfEPsquare;
SetBitboardFromEnum(opponentPawnType, opponentPawnBB);
// Remove pawn from board array
BoardArray[move.src] = Piece.Empty;
BoardArray[move.dst] = pieceToMove;
BoardArray[inFrontOfEPsquare] = Piece.Empty;
// Clear EP square (already been used)
epSquare = 0;
break;
case MoveType.PawnDoublePush:
pieceToMove = BoardArray[move.src];
// Get the square behind the pawn by getting the
// middle square between the start and end of the
// double pawn push.
int newEPsquare = (move.src + move.dst) / 2;
epSquare = 1UL << newEPsquare;
// Update piece bitboard
bb = GetBitboardFromEnum(pieceToMove);
bb ^= 1UL << move.src | 1UL << move.dst;
SetBitboardFromEnum(pieceToMove, bb);
// Update board array
BoardArray[move.src] = Piece.Empty;
BoardArray[move.dst] = pieceToMove;
break;
case MoveType.Castling960:
// Clear en-passant square
epSquare = 0;
// Get the king moving
Piece kingToMove = Piece.BlackKing - SideToMove;
// Reset castling rights depending on side
castlingRights &= ~(0b0011 << 2 * SideToMove);
// Get where the king will end up
int endKingPosition = move.src < move.dst ? 6 : 2;
if (kingToMove == Piece.BlackKing) endKingPosition += 56;
// Update bitboard of king
bb = GetBitboardFromEnum(kingToMove);
bb ^= 1UL << move.src | 1UL << endKingPosition;
SetBitboardFromEnum(kingToMove, bb);
// Get where the rook will end up
int endRookPosition = move.src < move.dst ? 5 : 3;
if (kingToMove == Piece.BlackKing) endRookPosition += 56;
// Get rook enum (used for obtaining bitboard)
Piece rookEnum = Piece.BlackRook - SideToMove;
// Update bitboard of rook
Bitboard rookBB = GetBitboardFromEnum(rookEnum);
rookBB ^= 1UL << move.dst | 1UL << endRookPosition;
SetBitboardFromEnum(rookEnum, rookBB);
// Update array
BoardArray[move.src] = Piece.Empty;
BoardArray[move.dst] = Piece.Empty;
BoardArray[endKingPosition] = kingToMove;
BoardArray[endRookPosition] = rookEnum;
break;
case MoveType.Promotion:
// Clear EP square
epSquare = 0;
pieceToMove = BoardArray[move.src];
// Move piece on array
BoardArray[move.src] = Piece.Empty;
Piece promotedPiece = move.promoPiece switch
{
PromoPiece.Bishop => Piece.BlackBishop - SideToMove,
PromoPiece.Knight => Piece.BlackKnight - SideToMove,
PromoPiece.Rook => Piece.BlackRook - SideToMove,
PromoPiece.Queen => Piece.BlackQueen - SideToMove,
_ => throw new Exception($"promotion piece \"{move.promoPiece}\" unaccounted for.")
};
Piece pieceLandedOn = BoardArray[move.dst];
if (pieceLandedOn != Piece.Empty)
{
boardInfo.capturedPiece = pieceLandedOn;
bb = GetBitboardFromEnum(pieceLandedOn);
bb ^= 1UL << move.dst;
SetBitboardFromEnum(pieceLandedOn, bb);
}
pieceCaptured = BoardArray[move.dst];
BoardArray[move.dst] = promotedPiece;
if (pieceCaptured == Piece.WhiteRook)
{
if (move.dst == 0) castlingRights &= ~0b0100;
if (move.dst == 7) castlingRights &= ~0b1000;
}
if (pieceCaptured == Piece.BlackRook)
{
if (move.dst == 56) castlingRights &= ~0b0001;
if (move.dst == 63) castlingRights &= ~0b0010; // issue somewhere here with castling and shit
}
// Update both sets of bitboards
bb = GetBitboardFromEnum(pieceToMove);
bb ^= 1UL << move.src;
SetBitboardFromEnum(pieceToMove, bb);
bb = GetBitboardFromEnum(promotedPiece);
bb ^= 1UL << move.dst;
SetBitboardFromEnum(promotedPiece, bb);
break;
default: // move flag was unaccounted for
throw new Exception($"move flag \"{move.type}\" on move {move} unaccounted for.");
}
// If the move played was a promotion move (pawn was promoted) or a piece
// on the board was captured, reset the halfmove clock
if (move.type == MoveType.Promotion || boardInfo.capturedPiece != Piece.Empty) halfMoveClock = 0;
// Otherwise, increase the halfmove clock
else halfMoveClock++;
boardHistory.Push(boardInfo);
UpdatePinsAndCheckers();
CheckForRepetitions();
}
public void UndoMove()
{
if (moveHistory.Count == 0) throw new Exception("cannot undo when no moves on the board have been played.");
// Get last move and last board info
Move previousMove = moveHistory.Pop();
BoardInfo previousBoardInfo = boardHistory.Pop();
checkmask = previousBoardInfo.checkmask;
pinD = previousBoardInfo.pinD;
pinHV = previousBoardInfo.pinHV;
castlingRights = previousBoardInfo.castlingRights;
epSquare = previousBoardInfo.EPsquare;
halfMoveClock = previousBoardInfo.halfMoveClock;
moveCounter--; // Decrease move counter
Piece pieceThatMoved = BoardArray[previousMove.dst];
// Edit board based on type of previous move
switch (previousMove.type)
{
case MoveType.Normal:
// Update bitboard of piece
Bitboard bb = GetBitboardFromEnum(pieceThatMoved);
bb ^= 1UL << previousMove.dst | 1UL << previousMove.src;
SetBitboardFromEnum(pieceThatMoved, bb);
// Check if a piece was captured
// If so, update their bitboard as well
if (previousBoardInfo.capturedPiece != Piece.Empty)
{
bb = GetBitboardFromEnum(previousBoardInfo.capturedPiece);
bb ^= 1UL << previousMove.dst;
SetBitboardFromEnum(previousBoardInfo.capturedPiece, bb);
}
BoardArray[previousMove.dst] = previousBoardInfo.capturedPiece;
BoardArray[previousMove.src] = pieceThatMoved;
break;
case MoveType.EnPassant:
// Get whichever pawn type did the en-passant
Piece pawnType = Piece.WhitePawn + SideToMove;
// Update bitboard of that piece
bb = GetBitboardFromEnum(pawnType);
bb ^= 1UL << previousMove.dst | 1UL << previousMove.src;
SetBitboardFromEnum(pawnType, bb);
Piece opponentPawnType = Piece.BlackPawn - SideToMove;
// Get the square in front of the EP square (relative to the side moving)
int squarePawnWasTakenFrom = previousMove.dst + (SideToMove == 0 ? -8 : 8);
// Update bitboard of opponent pawn type
// (replace the pawn that was captured)
bb = GetBitboardFromEnum(opponentPawnType);
bb ^= 1UL << squarePawnWasTakenFrom;
SetBitboardFromEnum(opponentPawnType, bb);
// Update board array
BoardArray[previousMove.src] = pawnType;
BoardArray[previousMove.dst] = Piece.Empty;
BoardArray[squarePawnWasTakenFrom] = opponentPawnType;
// En-passant square is previous move destination
epSquare = previousBoardInfo.EPsquare;
break;
case MoveType.PawnDoublePush:
pawnType = BoardArray[previousMove.dst];
bb = GetBitboardFromEnum(pawnType);
bb ^= 1UL << previousMove.dst | 1UL << previousMove.src;
SetBitboardFromEnum(pawnType, bb);
// Reset en-passant square
epSquare = previousBoardInfo.EPsquare;
// Update board array
BoardArray[previousMove.src] = pawnType;
BoardArray[previousMove.dst] = Piece.Empty;
break;
case MoveType.Castling960:
Piece kingEnum = Piece.WhiteKing + SideToMove;
bool isKingside = previousMove.src < previousMove.dst;
// Is kingside? Go to square 6 (G1). If not, go to square 2 (C1)
int endKingPosition = isKingside ? 6 : 2;
if (ColourToMove == Colour.Black) endKingPosition += 56;
// Update king bitboard
bb = GetBitboardFromEnum(kingEnum);
bb ^= 1UL << endKingPosition | 1UL << previousMove.src;
SetBitboardFromEnum(kingEnum, bb);
// Get rook position
int rookPosition = previousMove.src < previousMove.dst ? 5 : 3;
if (kingEnum == Piece.BlackKing) rookPosition += 56;
Piece rookEnum = Piece.WhiteRook + SideToMove;
// Update rook bitboard
bb = GetBitboardFromEnum(rookEnum);
bb ^= 1UL << rookPosition | 1UL << previousMove.dst;
SetBitboardFromEnum(rookEnum, bb);
// Reset castling rights
castlingRights = previousBoardInfo.castlingRights;
// Console.WriteLine($"[undo move {previousMove}] src: {previousMove.src}, dst: {previousMove.dst}, rookPos: {rookPosition}, endKingPos: {endKingPosition}");
// Update board array
BoardArray[endKingPosition] = Piece.Empty;
BoardArray[rookPosition] = Piece.Empty;
BoardArray[previousMove.dst] = rookEnum;
BoardArray[previousMove.src] = kingEnum;
// Reset en-passant square
epSquare = previousBoardInfo.EPsquare;
break;
case MoveType.Promotion:
// Reset en-passant square
epSquare = previousBoardInfo.EPsquare;
Piece promotedPiece = previousMove.promoPiece switch
{
PromoPiece.Bishop => Piece.WhiteBishop + SideToMove,
PromoPiece.Knight => Piece.WhiteKnight + SideToMove,
PromoPiece.Rook => Piece.WhiteRook + SideToMove,
PromoPiece.Queen => Piece.WhiteQueen + SideToMove,
_ => throw new Exception($"promotion piece \"{previousMove.promoPiece}\" unaccounted for.")
};
pawnType = Piece.WhitePawn + SideToMove;
if (previousBoardInfo.capturedPiece != Piece.Empty)
{
bb = GetBitboardFromEnum(previousBoardInfo.capturedPiece);
bb ^= 1UL << previousMove.dst;
SetBitboardFromEnum(previousBoardInfo.capturedPiece, bb);
}
// Update board array
BoardArray[previousMove.src] = pawnType;
BoardArray[previousMove.dst] = previousBoardInfo.capturedPiece;
// Update bitboards
bb = GetBitboardFromEnum(pawnType);
bb ^= 1UL << previousMove.src;
SetBitboardFromEnum(pawnType, bb);
bb = GetBitboardFromEnum(promotedPiece);
bb ^= 1UL << previousMove.dst;
SetBitboardFromEnum(promotedPiece, bb);
break;
default:
throw new Exception($"move flag \"{previousMove.type}\" on move {previousMove} unaccounted for.");
}
UpdatePinsAndCheckers();
}
public List<Move> GenerateLegalMoves()
{
List<Move> moves = [];
// If there are two checkers, only generate king moves
if (checkers.BitCount() == 2)
{
Moves.GenerateKingMoves(
friendlyPieces: PlayerToMove,
opponentPieces: OpponentToMove,
square: PlayerToMove.KingSquare,
moveListToAddTo: moves
);
return moves;
}
Bitboard rooksQueens = PlayerToMove.Queens | PlayerToMove.Rooks;
while (rooksQueens)
{
Moves.GenerateRookMoves(
friendlyOccupancy: PlayerToMove.Mask,
opponentOccupancy: OpponentToMove.Mask,
square: rooksQueens.PopLSB(),
pinHV: pinHV,
pinD: pinD,
checkmask: checkmask,
moveListToAddTo: moves
);
}
Bitboard bishopsQueens = PlayerToMove.Bishops | PlayerToMove.Queens;
while (bishopsQueens)
{
Moves.GenerateBishopMoves(
friendlyOccupancy: PlayerToMove.Mask,
opponentOccupancy: OpponentToMove.Mask,
square: bishopsQueens.PopLSB(),
pinHV: pinHV,
pinD: pinD,
checkmask: checkmask,
moveListToAddTo: moves
);
}
Bitboard knights = PlayerToMove.Knights;
while (knights)
{
Moves.GenerateKnightMoves(
friendlyOccupancy: PlayerToMove.Mask,
square: knights.PopLSB(),
moveListToAddTo: moves,
pinmask: pinD | pinHV,
checkmask: checkmask
);
}
Moves.GeneratePawnMoves(
whitePieces: White,
blackPieces: Black,
epBitboard: epSquare,
moveList: moves,
pinHV: pinHV,
pinD: pinD,
checkmask: checkmask,
side: ColourToMove
);
Moves.GenerateKingMoves(
friendlyPieces: PlayerToMove,
opponentPieces: OpponentToMove,
square: PlayerToMove.KingSquare,
moveListToAddTo: moves
);
if (checkers.BitCount() == 0) // not in check
{
Moves.GenerateCastling960Moves(
board: this,
moveList: moves
);
}
return moves;
}
public void UpdatePinsAndCheckers()
{
PieceSet us = PlayerToMove;
PieceSet them = OpponentToMove;
Bitboard knightCheckers = Bitmask.ForKnight(0, us.KingSquare) & them.Knights;
// Set directions for generating pawn checkers
Direction upLeft, upRight;
if (us.colour == Colour.White)
{
upLeft = Direction.Northwest;
upRight = Direction.Northeast;
}
else
{
upLeft = Direction.Southeast;
upRight = Direction.Southwest;
}
// Manually generate pawn checkers instead of using a function because the function
// accounts for taking pieces instead of simply attacking squares, meaning we can't
// use it for this purpose.
Bitboard pawnCheckers = them.Pawns & (us.King.Shift(upLeft) | us.King.Shift(upRight));
// For rooks, queens and bishops
Bitboard queens = GetBitboardFromEnum(Piece.BlackQueen - SideToMove);
Bitboard bishopsQueens = GetBitboardFromEnum(Piece.BlackBishop - SideToMove) ^ queens;
Bitboard rooksQueens = GetBitboardFromEnum(Piece.BlackRook - SideToMove) ^ queens;
Bitboard bishopAttacks = bishopsQueens & Bitmask.ForBishop(them.Mask, us.KingSquare);
Bitboard rookAttacks = rooksQueens & Bitmask.ForRook(them.Mask, us.KingSquare);
checkers = pawnCheckers | knightCheckers;
checkmask = pawnCheckers | knightCheckers;
pinD = 0;
pinHV = 0;
while (bishopAttacks)
{
int sq = bishopAttacks.PopLSB();
Bitboard checkray = Bitmask.RayBetween(us.KingSquare, sq);
Bitboard blockers = checkray & us.Mask;
int numBlockers = blockers.BitCount();
if (numBlockers == 0)
{
checkmask |= checkray | 1UL << sq;
checkers |= 1UL << sq;
}
else if (numBlockers == 1)
{
pinD |= checkray | 1UL << sq | blockers;
}
}
while (rookAttacks)
{
int sq = rookAttacks.PopLSB();
Bitboard checkray = Bitmask.RayBetween(us.KingSquare, sq);
Bitboard blockers = checkray & us.Mask;
int numBlockers = blockers.BitCount();
if (numBlockers == 0)
{
checkmask |= checkray | 1UL << sq;
checkers |= 1UL << sq;
}
else if (numBlockers == 1)
{
pinHV |= checkray | 1UL << sq | blockers;
}
}
if (!checkmask) checkmask = Bitboard.Filled;
}
public override string ToString()
{
string[] board = new string[8];
for (int rank = 0; rank < 8; rank++)
{
string line = "";
for (int file = 0; file < 8; file++)
{
int index = rank * 8 + file;
char stringPiece = BoardArray[index] switch
{
Piece.WhitePawn => 'P',
Piece.WhiteBishop => 'B',
Piece.WhiteKnight => 'N',
Piece.WhiteQueen => 'Q',
Piece.WhiteRook => 'R',
Piece.WhiteKing => 'K',
Piece.BlackPawn => 'p',
Piece.BlackBishop => 'b',
Piece.BlackKnight => 'n',
Piece.BlackRook => 'r',
Piece.BlackQueen => 'q',
Piece.BlackKing => 'k',
_ => '.'
};
line += stringPiece + " ";
}
board[7 - rank] = line;
}
return string.Join("\n", board);
}
public void CheckForRepetitions()
{
Dictionary<Move, int> pastMoves = new();
foreach (Move pastMove in moveHistory)
{
pastMoves[pastMove] = pastMoves.ContainsKey(pastMove) ? pastMoves[pastMove] + 1 : 1;
if (pastMoves.ContainsValue(3))
{
throw new Exception($"repeated position 3 times. Move that triggered this: {pastMove}");
}
}
}
private string GetFEN()
{
string[] linesOfFEN = new string[8];
int emptySpaces = 0;
// Encode the board into a FEN string
for (int rank = 7; rank != -1; rank--)
{
string line = "";
for (int file = 0; file < 8; file++)
{
int index = rank * 8 + file;
if (BoardArray[index] == Piece.Empty)
{
emptySpaces++;
}
else
{
if (emptySpaces > 0)
{
line += $"{emptySpaces}";
emptySpaces = 0;
}
line += BoardArray[index] switch
{
Piece.WhiteBishop => 'B',
Piece.BlackBishop => 'b',
Piece.WhiteKnight => 'N',
Piece.BlackKnight => 'n',
Piece.WhiteRook => 'R',
Piece.BlackRook => 'r',
Piece.WhitePawn => 'P',
Piece.BlackPawn => 'p',
Piece.WhiteQueen => 'Q',
Piece.BlackQueen => 'q',
Piece.WhiteKing => 'K',
Piece.BlackKing => 'k',
_ => throw new Exception($"piece enum {BoardArray[index]} unaccounted for while constructing FEN string.")
};
}
}
if (emptySpaces > 0)
{
line += $"{emptySpaces}";
emptySpaces = 0;
}
linesOfFEN[rank] = line;
}
string FEN = string.Join("/", linesOfFEN.Reverse());
// Add the side to move
string[] sidesToMove = ["w", "b"];
FEN += " " + sidesToMove[SideToMove];
string castlingRightsToAdd;
// Translate the castling rights from a int to a string
if (castlingRights == 0)
{
castlingRightsToAdd = "-";
}
else
{
castlingRightsToAdd = "";
string[] castlingRightsValues = ["q", "k", "Q", "K"];
// Go back to front (start at MSB instead of LSB)
for (int x = 3; x > -1; x--)
{
if ((castlingRights & (1 << x)) != 0)
{
castlingRightsToAdd += castlingRightsValues[x];
}
}
}
// Add the castling rights
FEN += " " + castlingRightsToAdd;
// Add the en-passant square
if (epSquare == 0)
{
FEN += " -";
}
else
{
int sq = epSquare.PopLSB();
string sqName = $"{"abcedfgh"[sq % 8]}{"12345678"[sq / 8]}";
FEN += " " + sqName;
}
// Add halftime move counter
FEN += $" {halfMoveClock}";
// Add fulltime move counter
FEN += " " + Convert.ToString((moveCounter - SideToMove) / 2);
return FEN;
}
}
}