Finish Magnetic chess

[vchess.git] / public / javascripts / variants / Magnetic.js

class MagneticRules extends ChessRules
{
    getEpSquare(move)
    {
        return undefined; //no en-passant
    }

    // Complete a move with magnetic actions
    applyMagneticLaws([x,y], move)
    {
        const standardMove = JSON.parse(JSON.stringify(move));
        this.play(standardMove);
        const color = this.getColor(x,y);
        const [sizeX,sizeY] = VariantRules.size;
        for (let step of [[-1,0],[1,0],[0,-1],[0,1]])
        {
            let [i,j] = [x+step[0],y+step[1]];
            while (i>=0 && i<sizeX && j>=0 && j<sizeY)
            {
                if (this.board[i][j] != VariantRules.EMPTY)
                {
                    // Found something. Same color or not?
                    if (this.getColor(i,j) != color)
                    {
                        // Attraction
                        if ((Math.abs(i-x)>=2 || Math.abs(j-y)>=2)
                            && this.getPiece(i,j) != VariantRules.KING)
                        {
                            move.vanish.push(
                                new PiPo({
                                    p:this.getPiece(i,j),
                                    c:this.getColor(i,j),
                                    x:i,
                                    y:j
                                })
                            );
                            move.appear.push(
                                new PiPo({
                                    p:this.getPiece(i,j),
                                    c:this.getColor(i,j),
                                    x:x+step[0],
                                    y:y+step[1]
                                })
                            );
                        }
                    }
                    else
                    {
                        // Repulsion
                        if (this.getPiece(i,j) != VariantRules.KING)
                        {
                            // Push it until we meet an obstacle or edge of the board
                            let [ii,jj] = [i+step[0],j+step[1]];
                            while (ii>=0 && ii<sizeX && jj>=0 && jj<sizeY)
                            {
                                if (this.board[ii][jj] != VariantRules.EMPTY)
                                    break;
                                ii += step[0];
                                jj += step[1];
                            }
                            ii -= step[0];
                            jj -= step[1];
                            if (Math.abs(ii-i)>=1 || Math.abs(jj-j)>=1)
                            {
                                move.vanish.push(
                                    new PiPo({
                                        p:this.getPiece(i,j),
                                        c:this.getColor(i,j),
                                        x:i,
                                        y:j
                                    })
                                );
                                move.appear.push(
                                    new PiPo({
                                        p:this.getPiece(i,j),
                                        c:this.getColor(i,j),
                                        x:ii,
                                        y:jj
                                    })
                                );
                            }
                        }
                    }
                    break;
                }
                i += step[0];
                j += step[1];
            }
        }
        this.undo(standardMove);
    }

    getBasicMove([sx,sy], [ex,ey], tr)
    {
        var 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)
                })
            ]
        });

        if (this.board[ex][ey] != VariantRules.EMPTY)
        {
            mv.vanish.push(
                new PiPo({
                    x: ex,
                    y: ey,
                    c: this.getColor(ex,ey),
                    p: this.getPiece(ex,ey)
                })
            );
        }
        this.applyMagneticLaws([ex,ey], mv);
        return mv;
    }

    getPotentialPawnMoves([x,y])
    {
        const color = this.getColor(x,y);
        var moves = [];
        var V = VariantRules;
        const [sizeX,sizeY] = VariantRules.size;
        let shift = (color == "w" ? -1 : 1);
        let startRank = (color == "w" ? sizeY-2 : 1);
        let firstRank = (color == 'w' ? sizeY-1 : 0);
        let lastRank = (color == "w" ? 0 : sizeY-1);

        if (x+shift >= 0 && x+shift < sizeX && x+shift != lastRank)
        {
            // Normal moves
            if (this.board[x+shift][y] == V.EMPTY)
            {
                moves.push(this.getBasicMove([x,y], [x+shift,y]));
                if ([startRank,firstRank].includes(x) && this.board[x+2*shift][y] == V.EMPTY)
                {
                    // Two squares jump
                    moves.push(this.getBasicMove([x,y], [x+2*shift,y]));
                }
            }
            // Captures
            if (y>0 && this.canTake([x,y], [x+shift,y-1]) && this.board[x+shift][y-1] != V.EMPTY)
                moves.push(this.getBasicMove([x,y], [x+shift,y-1]));
            if (y<sizeY-1 && this.canTake([x,y], [x+shift,y+1]) && this.board[x+shift][y+1] != V.EMPTY)
                moves.push(this.getBasicMove([x,y], [x+shift,y+1]));
        }

        if (x+shift == lastRank)
        {
            // Promotion
            let promotionPieces = [V.ROOK,V.KNIGHT,V.BISHOP,V.QUEEN];
            promotionPieces.forEach(p => {
                // Normal move
                if (this.board[x+shift][y] == V.EMPTY)
                    moves.push(this.getBasicMove([x,y], [x+shift,y], {c:color,p:p}));
                // Captures
                if (y>0 && this.canTake([x,y], [x+shift,y-1]) && this.board[x+shift][y-1] != V.EMPTY)
                    moves.push(this.getBasicMove([x,y], [x+shift,y-1], {c:color,p:p}));
                if (y<sizeY-1 && this.canTake([x,y], [x+shift,y+1]) && this.board[x+shift][y+1] != V.EMPTY)
                    moves.push(this.getBasicMove([x,y], [x+shift,y+1], {c:color,p:p}));
            });
        }

        // No en passant

        return moves;
    }

    getCastleMoves([x,y])
    {
        const c = this.getColor(x,y);
        if (x != (c=="w" ? 7 : 0) || y != this.INIT_COL_KING[c])
            return []; //x isn't first rank, or king has moved (shortcut)

        const V = VariantRules;

        // Castling ?
        const oppCol = this.getOppCol(c);
        let moves = [];
        let i = 0;
        const finalSquares = [ [2,3], [6,5] ]; //king, then rook
        castlingCheck:
        for (let castleSide=0; castleSide < 2; castleSide++) //large, then small
        {
            if (!this.flags[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
            let cmove = 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)}
            });
            this.applyMagneticLaws([x,finalSquares[castleSide][1]], cmove);
            moves.push(cmove);
        }

        return moves;
    }

    // TODO: verify this assertion
//  atLeastOneMove()
//  {
//      return true; //always at least one possible move
//  }

    underCheck(move)
    {
        return false; //there is no check
    }

    getCheckSquares(move)
    {
        const c = this.getOppCol(this.turn); //opponent
        const saveKingPos = this.kingPos[c]; //king might be taken
        this.play(move);
        // The only way to be "under check" is to have lost the king (thus game over)
        let res = this.kingPos[c][0] < 0
            ? [ JSON.parse(JSON.stringify(saveKingPos)) ]
            : [ ];
        this.undo(move);
        return res;
    }

    updateVariables(move)
    {
        super.updateVariables(move);
        const c = this.getColor(move.start.x,move.start.y);
        if (c != this.getColor(move.end.x,move.end.y)
            && this.board[move.end.x][move.end.y] != VariantRules.EMPTY
            && this.getPiece(move.end.x,move.end.y) == VariantRules.KING)
        {
            // We took opponent king !
            const oppCol = this.getOppCol(c);
            this.kingPos[oppCol] = [-1,-1];
            this.flags[oppCol] = [false,false];
        }
    }

    unupdateVariables(move)
    {
        super.unupdateVariables(move);
        const c = this.getColor(move.start.x,move.start.y);
        const oppCol = this.getOppCol(c);
        if (this.kingPos[oppCol][0] < 0)
        {
            // Last move took opponent's king
            for (let psq of move.vanish)
            {
                if (psq.p == 'k')
                {
                    this.kingPos[oppCol] = [psq.x, psq.y];
                    break;
                }
            }
        }
    }

    checkGameOver()
    {
        if (this.checkRepetition())
            return "1/2";

        const color = this.turn;
        // TODO: do we need "atLeastOneMove()"?
        if (this.atLeastOneMove() && this.kingPos[color][0] >= 0)
            return "*";

        return this.checkGameEnd();
    }

    checkGameEnd()
    {
        // No valid move: our king disappeared
        return this.turn == "w" ? "0-1" : "1-0";
    }
}