--- /dev/null
+// (Orthodox) Chess rules are defined in ChessRules class.
+// Variants generally inherit from it, and modify some parts.
+
+class PiPo //Piece+Position
+{
+ // o: {piece[p], color[c], posX[x], posY[y]}
+ constructor(o)
+ {
+ this.p = o.p;
+ this.c = o.c;
+ this.x = o.x;
+ this.y = o.y;
+ }
+}
+
+// TODO: for animation, moves should contains "moving" and "fading" maybe...
+class Move
+{
+ // o: {appear, vanish, [start,] [end,]}
+ // appear,vanish = arrays of PiPo
+ // start,end = coordinates to apply to trigger move visually (think castle)
+ constructor(o)
+ {
+ this.appear = o.appear;
+ this.vanish = o.vanish;
+ this.start = !!o.start ? o.start : {x:o.vanish[0].x, y:o.vanish[0].y};
+ this.end = !!o.end ? o.end : {x:o.appear[0].x, y:o.appear[0].y};
+ }
+}
+
+// NOTE: x coords = top to bottom; y = left to right (from white player perspective)
+class ChessRules
+{
+ //////////////
+ // MISC UTILS
+
+ static get HasFlags() { return true; } //some variants don't have flags
+
+ static get HasEnpassant() { return true; } //some variants don't have ep.
+
+ // Path to pieces
+ static getPpath(b)
+ {
+ return b; //usual pieces in pieces/ folder
+ }
+
+ // Turn "wb" into "B" (for FEN)
+ static board2fen(b)
+ {
+ return b[0]=='w' ? b[1].toUpperCase() : b[1];
+ }
+
+ // Turn "p" into "bp" (for board)
+ static fen2board(f)
+ {
+ return f.charCodeAt()<=90 ? "w"+f.toLowerCase() : "b"+f;
+ }
+
+ // Check if FEN describe a position
+ static IsGoodFen(fen)
+ {
+ const fenParsed = V.ParseFen(fen);
+ // 1) Check position
+ if (!V.IsGoodPosition(fenParsed.position))
+ return false;
+ // 2) Check turn
+ if (!fenParsed.turn || !V.IsGoodTurn(fenParsed.turn))
+ return false;
+ // 3) Check moves count
+ if (!fenParsed.movesCount || !(parseInt(fenParsed.movesCount) >= 0))
+ return false;
+ // 4) Check flags
+ if (V.HasFlags && (!fenParsed.flags || !V.IsGoodFlags(fenParsed.flags)))
+ return false;
+ // 5) Check enpassant
+ if (V.HasEnpassant &&
+ (!fenParsed.enpassant || !V.IsGoodEnpassant(fenParsed.enpassant)))
+ {
+ return false;
+ }
+ return true;
+ }
+
+ // Is position part of the FEN a priori correct?
+ static IsGoodPosition(position)
+ {
+ if (position.length == 0)
+ return false;
+ const rows = position.split("/");
+ if (rows.length != V.size.x)
+ return false;
+ for (let row of rows)
+ {
+ let sumElts = 0;
+ for (let i=0; i<row.length; i++)
+ {
+ if (V.PIECES.includes(row[i].toLowerCase()))
+ sumElts++;
+ else
+ {
+ const num = parseInt(row[i]);
+ if (isNaN(num))
+ return false;
+ sumElts += num;
+ }
+ }
+ if (sumElts != V.size.y)
+ return false;
+ }
+ return true;
+ }
+
+ // For FEN checking
+ static IsGoodTurn(turn)
+ {
+ return ["w","b"].includes(turn);
+ }
+
+ // For FEN checking
+ static IsGoodFlags(flags)
+ {
+ return !!flags.match(/^[01]{4,4}$/);
+ }
+
+ static IsGoodEnpassant(enpassant)
+ {
+ if (enpassant != "-")
+ {
+ const ep = V.SquareToCoords(fenParsed.enpassant);
+ if (isNaN(ep.x) || !V.OnBoard(ep))
+ return false;
+ }
+ return true;
+ }
+
+ // 3 --> d (column number to letter)
+ static CoordToColumn(colnum)
+ {
+ return String.fromCharCode(97 + colnum);
+ }
+
+ // d --> 3 (column letter to number)
+ static ColumnToCoord(column)
+ {
+ return column.charCodeAt(0) - 97;
+ }
+
+ // a4 --> {x:3,y:0}
+ static SquareToCoords(sq)
+ {
+ return {
+ // NOTE: column is always one char => max 26 columns
+ // row is counted from black side => subtraction
+ x: V.size.x - parseInt(sq.substr(1)),
+ y: sq[0].charCodeAt() - 97
+ };
+ }
+
+ // {x:0,y:4} --> e8
+ static CoordsToSquare(coords)
+ {
+ return V.CoordToColumn(coords.y) + (V.size.x - coords.x);
+ }
+
+ // Aggregates flags into one object
+ aggregateFlags()
+ {
+ return this.castleFlags;
+ }
+
+ // Reverse operation
+ disaggregateFlags(flags)
+ {
+ this.castleFlags = flags;
+ }
+
+ // En-passant square, if any
+ getEpSquare(moveOrSquare)
+ {
+ if (!moveOrSquare)
+ return undefined;
+ if (typeof moveOrSquare === "string")
+ {
+ const square = moveOrSquare;
+ if (square == "-")
+ return undefined;
+ return V.SquareToCoords(square);
+ }
+ // Argument is a move:
+ const move = moveOrSquare;
+ const [sx,sy,ex] = [move.start.x,move.start.y,move.end.x];
+ // TODO: next conditions are first for Atomic, and third for Checkered
+ if (move.appear.length > 0 && move.appear[0].p == V.PAWN && ["w","b"].includes(move.appear[0].c) && Math.abs(sx - ex) == 2)
+ {
+ return {
+ x: (sx + ex)/2,
+ y: sy
+ };
+ }
+ return undefined; //default
+ }
+
+ // Can thing on square1 take thing on square2
+ canTake([x1,y1], [x2,y2])
+ {
+ return this.getColor(x1,y1) !== this.getColor(x2,y2);
+ }
+
+ // Is (x,y) on the chessboard?
+ static OnBoard(x,y)
+ {
+ return (x>=0 && x<V.size.x && y>=0 && y<V.size.y);
+ }
+
+ // Used in interface: 'side' arg == player color
+ canIplay(side, [x,y])
+ {
+ return (this.turn == side && this.getColor(x,y) == side);
+ }
+
+ // On which squares is color under check ? (for interface)
+ getCheckSquares(color)
+ {
+ return this.isAttacked(this.kingPos[color], [V.GetOppCol(color)])
+ ? [JSON.parse(JSON.stringify(this.kingPos[color]))] //need to duplicate!
+ : [];
+ }
+
+ /////////////
+ // FEN UTILS
+
+ // Setup the initial random (assymetric) position
+ static GenRandInitFen()
+ {
+ let pieces = { "w": new Array(8), "b": new Array(8) };
+ // Shuffle pieces on first and last rank
+ for (let c of ["w","b"])
+ {
+ let positions = _.range(8);
+
+ // Get random squares for bishops
+ let randIndex = 2 * _.random(3);
+ const bishop1Pos = positions[randIndex];
+ // The second bishop must be on a square of different color
+ let randIndex_tmp = 2 * _.random(3) + 1;
+ const bishop2Pos = positions[randIndex_tmp];
+ // Remove chosen squares
+ positions.splice(Math.max(randIndex,randIndex_tmp), 1);
+ positions.splice(Math.min(randIndex,randIndex_tmp), 1);
+
+ // Get random squares for knights
+ randIndex = _.random(5);
+ const knight1Pos = positions[randIndex];
+ positions.splice(randIndex, 1);
+ randIndex = _.random(4);
+ const knight2Pos = positions[randIndex];
+ positions.splice(randIndex, 1);
+
+ // Get random square for queen
+ randIndex = _.random(3);
+ const queenPos = positions[randIndex];
+ positions.splice(randIndex, 1);
+
+ // Rooks and king positions are now fixed,
+ // because of the ordering rook-king-rook
+ const rook1Pos = positions[0];
+ const kingPos = positions[1];
+ const rook2Pos = positions[2];
+
+ // Finally put the shuffled pieces in the board array
+ pieces[c][rook1Pos] = 'r';
+ pieces[c][knight1Pos] = 'n';
+ pieces[c][bishop1Pos] = 'b';
+ pieces[c][queenPos] = 'q';
+ pieces[c][kingPos] = 'k';
+ pieces[c][bishop2Pos] = 'b';
+ pieces[c][knight2Pos] = 'n';
+ pieces[c][rook2Pos] = 'r';
+ }
+ return pieces["b"].join("") +
+ "/pppppppp/8/8/8/8/PPPPPPPP/" +
+ pieces["w"].join("").toUpperCase() +
+ " w 0 1111 -"; //add turn + flags + enpassant
+ }
+
+ // "Parse" FEN: just return untransformed string data
+ static ParseFen(fen)
+ {
+ const fenParts = fen.split(" ");
+ let res =
+ {
+ position: fenParts[0],
+ turn: fenParts[1],
+ movesCount: fenParts[2],
+ };
+ let nextIdx = 3;
+ if (V.HasFlags)
+ Object.assign(res, {flags: fenParts[nextIdx++]});
+ if (V.HasEnpassant)
+ Object.assign(res, {enpassant: fenParts[nextIdx]});
+ return res;
+ }
+
+ // Return current fen (game state)
+ getFen()
+ {
+ return this.getBaseFen() + " " +
+ this.getTurnFen() + " " + this.movesCount +
+ (V.HasFlags ? (" " + this.getFlagsFen()) : "") +
+ (V.HasEnpassant ? (" " + this.getEnpassantFen()) : "");
+ }
+
+ // Position part of the FEN string
+ getBaseFen()
+ {
+ let position = "";
+ for (let i=0; i<V.size.x; i++)
+ {
+ let emptyCount = 0;
+ for (let j=0; j<V.size.y; j++)
+ {
+ if (this.board[i][j] == V.EMPTY)
+ emptyCount++;
+ else
+ {
+ if (emptyCount > 0)
+ {
+ // Add empty squares in-between
+ position += emptyCount;
+ emptyCount = 0;
+ }
+ position += V.board2fen(this.board[i][j]);
+ }
+ }
+ if (emptyCount > 0)
+ {
+ // "Flush remainder"
+ position += emptyCount;
+ }
+ if (i < V.size.x - 1)
+ position += "/"; //separate rows
+ }
+ return position;
+ }
+
+ getTurnFen()
+ {
+ return this.turn;
+ }
+
+ // Flags part of the FEN string
+ getFlagsFen()
+ {
+ let flags = "";
+ // Add castling flags
+ for (let i of ['w','b'])
+ {
+ for (let j=0; j<2; j++)
+ flags += (this.castleFlags[i][j] ? '1' : '0');
+ }
+ return flags;
+ }
+
+ // Enpassant part of the FEN string
+ getEnpassantFen()
+ {
+ const L = this.epSquares.length;
+ if (!this.epSquares[L-1])
+ return "-"; //no en-passant
+ return V.CoordsToSquare(this.epSquares[L-1]);
+ }
+
+ // Turn position fen into double array ["wb","wp","bk",...]
+ static GetBoard(position)
+ {
+ const rows = position.split("/");
+ let board = doubleArray(V.size.x, V.size.y, "");
+ for (let i=0; i<rows.length; i++)
+ {
+ let j = 0;
+ for (let indexInRow = 0; indexInRow < rows[i].length; indexInRow++)
+ {
+ const character = rows[i][indexInRow];
+ const num = parseInt(character);
+ if (!isNaN(num))
+ j += num; //just shift j
+ else //something at position i,j
+ board[i][j++] = V.fen2board(character);
+ }
+ }
+ return board;
+ }
+
+ // Extract (relevant) flags from fen
+ setFlags(fenflags)
+ {
+ // white a-castle, h-castle, black a-castle, h-castle
+ this.castleFlags = {'w': [true,true], 'b': [true,true]};
+ if (!fenflags)
+ return;
+ for (let i=0; i<4; i++)
+ this.castleFlags[i < 2 ? 'w' : 'b'][i%2] = (fenflags.charAt(i) == '1');
+ }
+
+ //////////////////
+ // INITIALIZATION
+
+ // Fen string fully describes the game state
+ constructor(fen)
+ {
+ const fenParsed = V.ParseFen(fen);
+ this.board = V.GetBoard(fenParsed.position);
+ this.turn = fenParsed.turn[0]; //[0] to work with MarseilleRules
+ this.movesCount = parseInt(fenParsed.movesCount);
+ this.setOtherVariables(fen);
+ }
+
+ // Scan board for kings and rooks positions
+ scanKingsRooks(fen)
+ {
+ this.INIT_COL_KING = {'w':-1, 'b':-1};
+ this.INIT_COL_ROOK = {'w':[-1,-1], 'b':[-1,-1]};
+ this.kingPos = {'w':[-1,-1], 'b':[-1,-1]}; //squares of white and black king
+ const fenRows = V.ParseFen(fen).position.split("/");
+ for (let i=0; i<fenRows.length; i++)
+ {
+ let k = 0; //column index on board
+ for (let j=0; j<fenRows[i].length; j++)
+ {
+ switch (fenRows[i].charAt(j))
+ {
+ case 'k':
+ this.kingPos['b'] = [i,k];
+ this.INIT_COL_KING['b'] = k;
+ break;
+ case 'K':
+ this.kingPos['w'] = [i,k];
+ this.INIT_COL_KING['w'] = k;
+ break;
+ case 'r':
+ if (this.INIT_COL_ROOK['b'][0] < 0)
+ this.INIT_COL_ROOK['b'][0] = k;
+ else
+ this.INIT_COL_ROOK['b'][1] = k;
+ break;
+ case 'R':
+ if (this.INIT_COL_ROOK['w'][0] < 0)
+ this.INIT_COL_ROOK['w'][0] = k;
+ else
+ this.INIT_COL_ROOK['w'][1] = k;
+ break;
+ default:
+ const num = parseInt(fenRows[i].charAt(j));
+ if (!isNaN(num))
+ k += (num-1);
+ }
+ k++;
+ }
+ }
+ }
+
+ // Some additional variables from FEN (variant dependant)
+ setOtherVariables(fen)
+ {
+ // Set flags and enpassant:
+ const parsedFen = V.ParseFen(fen);
+ if (V.HasFlags)
+ this.setFlags(parsedFen.flags);
+ if (V.HasEnpassant)
+ {
+ const epSq = parsedFen.enpassant != "-"
+ ? V.SquareToCoords(parsedFen.enpassant)
+ : undefined;
+ this.epSquares = [ epSq ];
+ }
+ // Search for king and rooks positions:
+ this.scanKingsRooks(fen);
+ }
+
+ /////////////////////
+ // GETTERS & SETTERS
+
+ static get size()
+ {
+ return {x:8, y:8};
+ }
+
+ // Color of thing on suqare (i,j). 'undefined' if square is empty
+ getColor(i,j)
+ {
+ return this.board[i][j].charAt(0);
+ }
+
+ // Piece type on square (i,j). 'undefined' if square is empty
+ getPiece(i,j)
+ {
+ return this.board[i][j].charAt(1);
+ }
+
+ // Get opponent color
+ static GetOppCol(color)
+ {
+ return (color=="w" ? "b" : "w");
+ }
+
+ // Get next color (for compatibility with 3 and 4 players games)
+ static GetNextCol(color)
+ {
+ return V.GetOppCol(color);
+ }
+
+ // Pieces codes (for a clearer code)
+ static get PAWN() { return 'p'; }
+ static get ROOK() { return 'r'; }
+ static get KNIGHT() { return 'n'; }
+ static get BISHOP() { return 'b'; }
+ static get QUEEN() { return 'q'; }
+ static get KING() { return 'k'; }
+
+ // For FEN checking:
+ static get PIECES()
+ {
+ return [V.PAWN,V.ROOK,V.KNIGHT,V.BISHOP,V.QUEEN,V.KING];
+ }
+
+ // Empty square
+ static get EMPTY() { return ""; }
+
+ // Some pieces movements
+ static get steps()
+ {
+ return {
+ 'r': [ [-1,0],[1,0],[0,-1],[0,1] ],
+ 'n': [ [-1,-2],[-1,2],[1,-2],[1,2],[-2,-1],[-2,1],[2,-1],[2,1] ],
+ 'b': [ [-1,-1],[-1,1],[1,-1],[1,1] ],
+ };
+ }
+
+ ////////////////////
+ // MOVES GENERATION
+
+ // All possible moves from selected square (assumption: color is OK)
+ getPotentialMovesFrom([x,y])
+ {
+ switch (this.getPiece(x,y))
+ {
+ case V.PAWN:
+ return this.getPotentialPawnMoves([x,y]);
+ case V.ROOK:
+ return this.getPotentialRookMoves([x,y]);
+ case V.KNIGHT:
+ return this.getPotentialKnightMoves([x,y]);
+ case V.BISHOP:
+ return this.getPotentialBishopMoves([x,y]);
+ case V.QUEEN:
+ return this.getPotentialQueenMoves([x,y]);
+ case V.KING:
+ return this.getPotentialKingMoves([x,y]);
+ }
+ }
+
+ // Build a regular move from its initial and destination squares.
+ // tr: transformation
+ getBasicMove([sx,sy], [ex,ey], tr)
+ {
+ let mv = new Move({
+ appear: [
+ new PiPo({
+ x: ex,
+ y: ey,
+ c: !!tr ? tr.c : this.getColor(sx,sy),
+ p: !!tr ? tr.p : this.getPiece(sx,sy)
+ })
+ ],
+ vanish: [
+ new PiPo({
+ x: sx,
+ y: sy,
+ c: this.getColor(sx,sy),
+ p: this.getPiece(sx,sy)
+ })
+ ]
+ });
+
+ // The opponent piece disappears if we take it
+ if (this.board[ex][ey] != V.EMPTY)
+ {
+ mv.vanish.push(
+ new PiPo({
+ x: ex,
+ y: ey,
+ c: this.getColor(ex,ey),
+ p: this.getPiece(ex,ey)
+ })
+ );
+ }
+ return mv;
+ }
+
+ // Generic method to find possible moves of non-pawn pieces:
+ // "sliding or jumping"
+ getSlideNJumpMoves([x,y], steps, oneStep)
+ {
+ const color = this.getColor(x,y);
+ let moves = [];
+ outerLoop:
+ for (let step of steps)
+ {
+ let i = x + step[0];
+ let j = y + step[1];
+ while (V.OnBoard(i,j) && this.board[i][j] == V.EMPTY)
+ {
+ moves.push(this.getBasicMove([x,y], [i,j]));
+ if (oneStep !== undefined)
+ continue outerLoop;
+ i += step[0];
+ j += step[1];
+ }
+ if (V.OnBoard(i,j) && this.canTake([x,y], [i,j]))
+ moves.push(this.getBasicMove([x,y], [i,j]));
+ }
+ return moves;
+ }
+
+ // What are the pawn moves from square x,y ?
+ getPotentialPawnMoves([x,y])
+ {
+ const color = this.turn;
+ let moves = [];
+ const [sizeX,sizeY] = [V.size.x,V.size.y];
+ const shiftX = (color == "w" ? -1 : 1);
+ const firstRank = (color == 'w' ? sizeX-1 : 0);
+ const startRank = (color == "w" ? sizeX-2 : 1);
+ const lastRank = (color == "w" ? 0 : sizeX-1);
+ const pawnColor = this.getColor(x,y); //can be different for checkered
+
+ // NOTE: next condition is generally true (no pawn on last rank)
+ if (x+shiftX >= 0 && x+shiftX < sizeX)
+ {
+ const finalPieces = x + shiftX == lastRank
+ ? [V.ROOK,V.KNIGHT,V.BISHOP,V.QUEEN]
+ : [V.PAWN]
+ // One square forward
+ if (this.board[x+shiftX][y] == V.EMPTY)
+ {
+ for (let piece of finalPieces)
+ {
+ moves.push(this.getBasicMove([x,y], [x+shiftX,y],
+ {c:pawnColor,p:piece}));
+ }
+ // Next condition because pawns on 1st rank can generally jump
+ if ([startRank,firstRank].includes(x)
+ && this.board[x+2*shiftX][y] == V.EMPTY)
+ {
+ // Two squares jump
+ moves.push(this.getBasicMove([x,y], [x+2*shiftX,y]));
+ }
+ }
+ // Captures
+ for (let shiftY of [-1,1])
+ {
+ if (y + shiftY >= 0 && y + shiftY < sizeY
+ && this.board[x+shiftX][y+shiftY] != V.EMPTY
+ && this.canTake([x,y], [x+shiftX,y+shiftY]))
+ {
+ for (let piece of finalPieces)
+ {
+ moves.push(this.getBasicMove([x,y], [x+shiftX,y+shiftY],
+ {c:pawnColor,p:piece}));
+ }
+ }
+ }
+ }
+
+ if (V.HasEnpassant)
+ {
+ // En passant
+ const Lep = this.epSquares.length;
+ const epSquare = this.epSquares[Lep-1]; //always at least one element
+ if (!!epSquare && epSquare.x == x+shiftX && Math.abs(epSquare.y - y) == 1)
+ {
+ let enpassantMove = this.getBasicMove([x,y], [epSquare.x,epSquare.y]);
+ enpassantMove.vanish.push({
+ x: x,
+ y: epSquare.y,
+ p: 'p',
+ c: this.getColor(x,epSquare.y)
+ });
+ moves.push(enpassantMove);
+ }
+ }
+
+ return moves;
+ }
+
+ // What are the rook moves from square x,y ?
+ getPotentialRookMoves(sq)
+ {
+ return this.getSlideNJumpMoves(sq, V.steps[V.ROOK]);
+ }
+
+ // What are the knight moves from square x,y ?
+ getPotentialKnightMoves(sq)
+ {
+ return this.getSlideNJumpMoves(sq, V.steps[V.KNIGHT], "oneStep");
+ }
+
+ // What are the bishop moves from square x,y ?
+ getPotentialBishopMoves(sq)
+ {
+ return this.getSlideNJumpMoves(sq, V.steps[V.BISHOP]);
+ }
+
+ // What are the queen moves from square x,y ?
+ getPotentialQueenMoves(sq)
+ {
+ return this.getSlideNJumpMoves(sq,
+ V.steps[V.ROOK].concat(V.steps[V.BISHOP]));
+ }
+
+ // What are the king moves from square x,y ?
+ getPotentialKingMoves(sq)
+ {
+ // Initialize with normal moves
+ let moves = this.getSlideNJumpMoves(sq,
+ V.steps[V.ROOK].concat(V.steps[V.BISHOP]), "oneStep");
+ return moves.concat(this.getCastleMoves(sq));
+ }
+
+ getCastleMoves([x,y])
+ {
+ const c = this.getColor(x,y);
+ if (x != (c=="w" ? V.size.x-1 : 0) || y != this.INIT_COL_KING[c])
+ return []; //x isn't first rank, or king has moved (shortcut)
+
+ // Castling ?
+ const oppCol = V.GetOppCol(c);
+ let moves = [];
+ let i = 0;
+ const finalSquares = [ [2,3], [V.size.y-2,V.size.y-3] ]; //king, then rook
+ castlingCheck:
+ for (let castleSide=0; castleSide < 2; castleSide++) //large, then small
+ {
+ if (!this.castleFlags[c][castleSide])
+ continue;
+ // If this code is reached, rooks and king are on initial position
+
+ // Nothing on the path of the king ?
+ // (And no checks; OK also if y==finalSquare)
+ let step = finalSquares[castleSide][0] < y ? -1 : 1;
+ for (i=y; i!=finalSquares[castleSide][0]; i+=step)
+ {
+ if (this.isAttacked([x,i], [oppCol]) || (this.board[x][i] != V.EMPTY &&
+ // NOTE: next check is enough, because of chessboard constraints
+ (this.getColor(x,i) != c
+ || ![V.KING,V.ROOK].includes(this.getPiece(x,i)))))
+ {
+ continue castlingCheck;
+ }
+ }
+
+ // Nothing on the path to the rook?
+ step = castleSide == 0 ? -1 : 1;
+ for (i = y + step; i != this.INIT_COL_ROOK[c][castleSide]; i += step)
+ {
+ if (this.board[x][i] != V.EMPTY)
+ continue castlingCheck;
+ }
+ const rookPos = this.INIT_COL_ROOK[c][castleSide];
+
+ // Nothing on final squares, except maybe king and castling rook?
+ for (i=0; i<2; i++)
+ {
+ if (this.board[x][finalSquares[castleSide][i]] != V.EMPTY &&
+ this.getPiece(x,finalSquares[castleSide][i]) != V.KING &&
+ finalSquares[castleSide][i] != rookPos)
+ {
+ continue castlingCheck;
+ }
+ }
+
+ // If this code is reached, castle is valid
+ moves.push( new Move({
+ appear: [
+ new PiPo({x:x,y:finalSquares[castleSide][0],p:V.KING,c:c}),
+ new PiPo({x:x,y:finalSquares[castleSide][1],p:V.ROOK,c:c})],
+ vanish: [
+ new PiPo({x:x,y:y,p:V.KING,c:c}),
+ new PiPo({x:x,y:rookPos,p:V.ROOK,c:c})],
+ end: Math.abs(y - rookPos) <= 2
+ ? {x:x, y:rookPos}
+ : {x:x, y:y + 2 * (castleSide==0 ? -1 : 1)}
+ }) );
+ }
+
+ return moves;
+ }
+
+ ////////////////////
+ // MOVES VALIDATION
+
+ // For the interface: possible moves for the current turn from square sq
+ getPossibleMovesFrom(sq)
+ {
+ return this.filterValid( this.getPotentialMovesFrom(sq) );
+ }
+
+ // TODO: promotions (into R,B,N,Q) should be filtered only once
+ filterValid(moves)
+ {
+ if (moves.length == 0)
+ return [];
+ const color = this.turn;
+ return moves.filter(m => {
+ this.play(m);
+ const res = !this.underCheck(color);
+ this.undo(m);
+ return res;
+ });
+ }
+
+ // Search for all valid moves considering current turn
+ // (for engine and game end)
+ getAllValidMoves()
+ {
+ const color = this.turn;
+ const oppCol = V.GetOppCol(color);
+ let potentialMoves = [];
+ for (let i=0; i<V.size.x; i++)
+ {
+ for (let j=0; j<V.size.y; j++)
+ {
+ // Next condition "!= oppCol" to work with checkered variant
+ if (this.board[i][j] != V.EMPTY && this.getColor(i,j) != oppCol)
+ {
+ Array.prototype.push.apply(potentialMoves,
+ this.getPotentialMovesFrom([i,j]));
+ }
+ }
+ }
+ return this.filterValid(potentialMoves);
+ }
+
+ // Stop at the first move found
+ atLeastOneMove()
+ {
+ const color = this.turn;
+ const oppCol = V.GetOppCol(color);
+ for (let i=0; i<V.size.x; i++)
+ {
+ for (let j=0; j<V.size.y; j++)
+ {
+ if (this.board[i][j] != V.EMPTY && this.getColor(i,j) != oppCol)
+ {
+ const moves = this.getPotentialMovesFrom([i,j]);
+ if (moves.length > 0)
+ {
+ for (let k=0; k<moves.length; k++)
+ {
+ if (this.filterValid([moves[k]]).length > 0)
+ return true;
+ }
+ }
+ }
+ }
+ }
+ return false;
+ }
+
+ // Check if pieces of color in 'colors' are attacking (king) on square x,y
+ isAttacked(sq, colors)
+ {
+ return (this.isAttackedByPawn(sq, colors)
+ || this.isAttackedByRook(sq, colors)
+ || this.isAttackedByKnight(sq, colors)
+ || this.isAttackedByBishop(sq, colors)
+ || this.isAttackedByQueen(sq, colors)
+ || this.isAttackedByKing(sq, colors));
+ }
+
+ // Is square x,y attacked by 'colors' pawns ?
+ isAttackedByPawn([x,y], colors)
+ {
+ for (let c of colors)
+ {
+ let pawnShift = (c=="w" ? 1 : -1);
+ if (x+pawnShift>=0 && x+pawnShift<V.size.x)
+ {
+ for (let i of [-1,1])
+ {
+ if (y+i>=0 && y+i<V.size.y && this.getPiece(x+pawnShift,y+i)==V.PAWN
+ && this.getColor(x+pawnShift,y+i)==c)
+ {
+ return true;
+ }
+ }
+ }
+ }
+ return false;
+ }
+
+ // Is square x,y attacked by 'colors' rooks ?
+ isAttackedByRook(sq, colors)
+ {
+ return this.isAttackedBySlideNJump(sq, colors, V.ROOK, V.steps[V.ROOK]);
+ }
+
+ // Is square x,y attacked by 'colors' knights ?
+ isAttackedByKnight(sq, colors)
+ {
+ return this.isAttackedBySlideNJump(sq, colors,
+ V.KNIGHT, V.steps[V.KNIGHT], "oneStep");
+ }
+
+ // Is square x,y attacked by 'colors' bishops ?
+ isAttackedByBishop(sq, colors)
+ {
+ return this.isAttackedBySlideNJump(sq, colors, V.BISHOP, V.steps[V.BISHOP]);
+ }
+
+ // Is square x,y attacked by 'colors' queens ?
+ isAttackedByQueen(sq, colors)
+ {
+ return this.isAttackedBySlideNJump(sq, colors, V.QUEEN,
+ V.steps[V.ROOK].concat(V.steps[V.BISHOP]));
+ }
+
+ // Is square x,y attacked by 'colors' king(s) ?
+ isAttackedByKing(sq, colors)
+ {
+ return this.isAttackedBySlideNJump(sq, colors, V.KING,
+ V.steps[V.ROOK].concat(V.steps[V.BISHOP]), "oneStep");
+ }
+
+ // Generic method for non-pawn pieces ("sliding or jumping"):
+ // is x,y attacked by a piece of color in array 'colors' ?
+ isAttackedBySlideNJump([x,y], colors, piece, steps, oneStep)
+ {
+ for (let step of steps)
+ {
+ let rx = x+step[0], ry = y+step[1];
+ while (V.OnBoard(rx,ry) && this.board[rx][ry] == V.EMPTY && !oneStep)
+ {
+ rx += step[0];
+ ry += step[1];
+ }
+ if (V.OnBoard(rx,ry) && this.getPiece(rx,ry) === piece
+ && colors.includes(this.getColor(rx,ry)))
+ {
+ return true;
+ }
+ }
+ return false;
+ }
+
+ // Is color under check after his move ?
+ underCheck(color)
+ {
+ return this.isAttacked(this.kingPos[color], [V.GetOppCol(color)]);
+ }
+
+ /////////////////
+ // MOVES PLAYING
+
+ // Apply a move on board
+ static PlayOnBoard(board, move)
+ {
+ for (let psq of move.vanish)
+ board[psq.x][psq.y] = V.EMPTY;
+ for (let psq of move.appear)
+ board[psq.x][psq.y] = psq.c + psq.p;
+ }
+ // Un-apply the played move
+ static UndoOnBoard(board, move)
+ {
+ for (let psq of move.appear)
+ board[psq.x][psq.y] = V.EMPTY;
+ for (let psq of move.vanish)
+ board[psq.x][psq.y] = psq.c + psq.p;
+ }
+
+ // After move is played, update variables + flags
+ updateVariables(move)
+ {
+ let piece = undefined;
+ let c = undefined;
+ if (move.vanish.length >= 1)
+ {
+ // Usual case, something is moved
+ piece = move.vanish[0].p;
+ c = move.vanish[0].c;
+ }
+ else
+ {
+ // Crazyhouse-like variants
+ piece = move.appear[0].p;
+ c = move.appear[0].c;
+ }
+ if (c == "c") //if (!["w","b"].includes(c))
+ {
+ // 'c = move.vanish[0].c' doesn't work for Checkered
+ c = V.GetOppCol(this.turn);
+ }
+ const firstRank = (c == "w" ? V.size.x-1 : 0);
+
+ // Update king position + flags
+ if (piece == V.KING && move.appear.length > 0)
+ {
+ this.kingPos[c][0] = move.appear[0].x;
+ this.kingPos[c][1] = move.appear[0].y;
+ if (V.HasFlags)
+ this.castleFlags[c] = [false,false];
+ return;
+ }
+ if (V.HasFlags)
+ {
+ // Update castling flags if rooks are moved
+ const oppCol = V.GetOppCol(c);
+ const oppFirstRank = (V.size.x-1) - firstRank;
+ if (move.start.x == firstRank //our rook moves?
+ && this.INIT_COL_ROOK[c].includes(move.start.y))
+ {
+ const flagIdx = (move.start.y == this.INIT_COL_ROOK[c][0] ? 0 : 1);
+ this.castleFlags[c][flagIdx] = false;
+ }
+ else if (move.end.x == oppFirstRank //we took opponent rook?
+ && this.INIT_COL_ROOK[oppCol].includes(move.end.y))
+ {
+ const flagIdx = (move.end.y == this.INIT_COL_ROOK[oppCol][0] ? 0 : 1);
+ this.castleFlags[oppCol][flagIdx] = false;
+ }
+ }
+ }
+
+ // After move is undo-ed *and flags resetted*, un-update other variables
+ // TODO: more symmetry, by storing flags increment in move (?!)
+ unupdateVariables(move)
+ {
+ // (Potentially) Reset king position
+ const c = this.getColor(move.start.x,move.start.y);
+ if (this.getPiece(move.start.x,move.start.y) == V.KING)
+ this.kingPos[c] = [move.start.x, move.start.y];
+ }
+
+ play(move)
+ {
+ // DEBUG:
+// if (!this.states) this.states = [];
+// const stateFen = this.getBaseFen() + this.getTurnFen() + this.getFlagsFen();
+// this.states.push(stateFen);
+
+ if (V.HasFlags)
+ move.flags = JSON.stringify(this.aggregateFlags()); //save flags (for undo)
+ if (V.HasEnpassant)
+ this.epSquares.push( this.getEpSquare(move) );
+ if (!move.color)
+ move.color = this.turn; //for interface
+ V.PlayOnBoard(this.board, move);
+ this.turn = V.GetOppCol(this.turn);
+ this.movesCount++;
+ this.updateVariables(move);
+ }
+
+ undo(move)
+ {
+ if (V.HasEnpassant)
+ this.epSquares.pop();
+ if (V.HasFlags)
+ this.disaggregateFlags(JSON.parse(move.flags));
+ V.UndoOnBoard(this.board, move);
+ this.turn = V.GetOppCol(this.turn);
+ this.movesCount--;
+ this.unupdateVariables(move);
+
+ // DEBUG:
+// const stateFen = this.getBaseFen() + this.getTurnFen() + this.getFlagsFen();
+// if (stateFen != this.states[this.states.length-1]) debugger;
+// this.states.pop();
+ }
+
+ ///////////////
+ // END OF GAME
+
+ // What is the score ? (Interesting if game is over)
+ getCurrentScore()
+ {
+ if (this.atLeastOneMove()) // game not over
+ return "*";
+
+ // Game over
+ const color = this.turn;
+ // No valid move: stalemate or checkmate?
+ if (!this.isAttacked(this.kingPos[color], [V.GetOppCol(color)]))
+ return "1/2";
+ // OK, checkmate
+ return (color == "w" ? "0-1" : "1-0");
+ }
+
+ ///////////////
+ // ENGINE PLAY
+
+ // Pieces values
+ static get VALUES()
+ {
+ return {
+ 'p': 1,
+ 'r': 5,
+ 'n': 3,
+ 'b': 3,
+ 'q': 9,
+ 'k': 1000
+ };
+ }
+
+ // "Checkmate" (unreachable eval)
+ static get INFINITY() { return 9999; }
+
+ // At this value or above, the game is over
+ static get THRESHOLD_MATE() { return V.INFINITY; }
+
+ // Search depth: 2 for high branching factor, 4 for small (Loser chess, eg.)
+ static get SEARCH_DEPTH() { return 3; }
+
+ // Assumption: at least one legal move
+ // NOTE: works also for extinction chess because depth is 3...
+ getComputerMove()
+ {
+ const maxeval = V.INFINITY;
+ const color = this.turn;
+ // Some variants may show a bigger moves list to the human (Switching),
+ // thus the argument "computer" below (which is generally ignored)
+ let moves1 = this.getAllValidMoves("computer");
+
+ // Can I mate in 1 ? (for Magnetic & Extinction)
+ for (let i of _.shuffle(_.range(moves1.length)))
+ {
+ this.play(moves1[i]);
+ let finish = (Math.abs(this.evalPosition()) >= V.THRESHOLD_MATE);
+ if (!finish)
+ {
+ const score = this.getCurrentScore();
+ if (["1-0","0-1"].includes(score))
+ finish = true;
+ }
+ this.undo(moves1[i]);
+ if (finish)
+ return moves1[i];
+ }
+
+ // Rank moves using a min-max at depth 2
+ for (let i=0; i<moves1.length; i++)
+ {
+ // Initial self evaluation is very low: "I'm checkmated"
+ moves1[i].eval = (color=="w" ? -1 : 1) * maxeval;
+ this.play(moves1[i]);
+ const score1 = this.getCurrentScore();
+ let eval2 = undefined;
+ if (score1 == "*")
+ {
+ // Initial enemy evaluation is very low too, for him
+ eval2 = (color=="w" ? 1 : -1) * maxeval;
+ // Second half-move:
+ let moves2 = this.getAllValidMoves("computer");
+ for (let j=0; j<moves2.length; j++)
+ {
+ this.play(moves2[j]);
+ const score2 = this.getCurrentScore();
+ const evalPos = score2 == "*"
+ ? this.evalPosition()
+ : (score2=="1/2" ? 0 : (score2=="1-0" ? 1 : -1) * maxeval);
+ if ((color == "w" && evalPos < eval2)
+ || (color=="b" && evalPos > eval2))
+ {
+ eval2 = evalPos;
+ }
+ this.undo(moves2[j]);
+ }
+ }
+ else
+ eval2 = (score1=="1/2" ? 0 : (score1=="1-0" ? 1 : -1) * maxeval);
+ if ((color=="w" && eval2 > moves1[i].eval)
+ || (color=="b" && eval2 < moves1[i].eval))
+ {
+ moves1[i].eval = eval2;
+ }
+ this.undo(moves1[i]);
+ }
+ moves1.sort( (a,b) => { return (color=="w" ? 1 : -1) * (b.eval - a.eval); });
+
+ let candidates = [0]; //indices of candidates moves
+ for (let j=1; j<moves1.length && moves1[j].eval == moves1[0].eval; j++)
+ candidates.push(j);
+ let currentBest = moves1[_.sample(candidates, 1)];
+
+ // From here, depth >= 3: may take a while, so we control time
+ const timeStart = Date.now();
+
+ // Skip depth 3+ if we found a checkmate (or if we are checkmated in 1...)
+ if (V.SEARCH_DEPTH >= 3 && Math.abs(moves1[0].eval) < V.THRESHOLD_MATE)
+ {
+ for (let i=0; i<moves1.length; i++)
+ {
+ if (Date.now()-timeStart >= 5000) //more than 5 seconds
+ return currentBest; //depth 2 at least
+ this.play(moves1[i]);
+ // 0.1 * oldEval : heuristic to avoid some bad moves (not all...)
+ moves1[i].eval = 0.1*moves1[i].eval +
+ this.alphabeta(V.SEARCH_DEPTH-1, -maxeval, maxeval);
+ this.undo(moves1[i]);
+ }
+ moves1.sort( (a,b) => {
+ return (color=="w" ? 1 : -1) * (b.eval - a.eval); });
+ }
+ else
+ return currentBest;
+// console.log(moves1.map(m => { return [this.getNotation(m), m.eval]; }));
+
+ candidates = [0];
+ for (let j=1; j<moves1.length && moves1[j].eval == moves1[0].eval; j++)
+ candidates.push(j);
+ return moves1[_.sample(candidates, 1)];
+ }
+
+ alphabeta(depth, alpha, beta)
+ {
+ const maxeval = V.INFINITY;
+ const color = this.turn;
+ const score = this.getCurrentScore();
+ if (score != "*")
+ return (score=="1/2" ? 0 : (score=="1-0" ? 1 : -1) * maxeval);
+ if (depth == 0)
+ return this.evalPosition();
+ const moves = this.getAllValidMoves("computer");
+ let v = color=="w" ? -maxeval : maxeval;
+ if (color == "w")
+ {
+ for (let i=0; i<moves.length; i++)
+ {
+ this.play(moves[i]);
+ v = Math.max(v, this.alphabeta(depth-1, alpha, beta));
+ this.undo(moves[i]);
+ alpha = Math.max(alpha, v);
+ if (alpha >= beta)
+ break; //beta cutoff
+ }
+ }
+ else //color=="b"
+ {
+ for (let i=0; i<moves.length; i++)
+ {
+ this.play(moves[i]);
+ v = Math.min(v, this.alphabeta(depth-1, alpha, beta));
+ this.undo(moves[i]);
+ beta = Math.min(beta, v);
+ if (alpha >= beta)
+ break; //alpha cutoff
+ }
+ }
+ return v;
+ }
+
+ evalPosition()
+ {
+ let evaluation = 0;
+ // Just count material for now
+ for (let i=0; i<V.size.x; i++)
+ {
+ for (let j=0; j<V.size.y; j++)
+ {
+ if (this.board[i][j] != V.EMPTY)
+ {
+ const sign = this.getColor(i,j) == "w" ? 1 : -1;
+ evaluation += sign * V.VALUES[this.getPiece(i,j)];
+ }
+ }
+ }
+ return evaluation;
+ }
+
+ /////////////////////////
+ // MOVES + GAME NOTATION
+ /////////////////////////
+
+ // Context: just before move is played, turn hasn't changed
+ // TODO: un-ambiguous notation (switch on piece type, check directions...)
+ getNotation(move)
+ {
+ if (move.appear.length == 2 && move.appear[0].p == V.KING) //castle
+ return (move.end.y < move.start.y ? "0-0-0" : "0-0");
+
+ // Translate final square
+ const finalSquare = V.CoordsToSquare(move.end);
+
+ const piece = this.getPiece(move.start.x, move.start.y);
+ if (piece == V.PAWN)
+ {
+ // Pawn move
+ let notation = "";
+ if (move.vanish.length > move.appear.length)
+ {
+ // Capture
+ const startColumn = V.CoordToColumn(move.start.y);
+ notation = startColumn + "x" + finalSquare;
+ }
+ else //no capture
+ notation = finalSquare;
+ if (move.appear.length > 0 && move.appear[0].p != V.PAWN) //promotion
+ notation += "=" + move.appear[0].p.toUpperCase();
+ return notation;
+ }
+
+ else
+ {
+ // Piece movement
+ return piece.toUpperCase() +
+ (move.vanish.length > move.appear.length ? "x" : "") + finalSquare;
+ }
+ }
+}
projects / vchess.git / blobdiff