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

class UltimaRules extends ChessRules
{
    static getPpath(b)
    {
        if (b[1] == "m") //'m' for Immobilizer (I is too similar to 1)
            return "Ultima/" + b;
        return b; //usual piece
    }

    initVariables(fen)
    {
        this.kingPos = {'w':[-1,-1], 'b':[-1,-1]};
        const fenParts = fen.split(" ");
        const position = fenParts[0].split("/");
        for (let i=0; i<position.length; i++)
        {
            let k = 0;
            for (let j=0; j<position[i].length; j++)
            {
                switch (position[i].charAt(j))
                {
                    case 'k':
                        this.kingPos['b'] = [i,k];
                        break;
                    case 'K':
                        this.kingPos['w'] = [i,k];
                        break;
                    default:
                        let num = parseInt(position[i].charAt(j));
                        if (!isNaN(num))
                            k += (num-1);
                }
                k++;
            }
        }
        this.epSquares = []; //no en-passant here
    }

    setFlags(fen)
    {
        // TODO: for compatibility?
        this.castleFlags = {"w":[false,false], "b":[false,false]};
    }

    static get IMMOBILIZER() { return 'm'; }
    // Although other pieces keep their names here for coding simplicity,
    // keep in mind that:
    //  - a "rook" is a coordinator, capturing by coordinating with the king
    //  - a "knight" is a long-leaper, capturing as in draughts
    //  - a "bishop" is a chameleon, capturing as its prey
    //  - a "queen" is a withdrawer, capturing by moving away from pieces

    // Is piece on square (x,y) immobilized?
    isImmobilized([x,y])
    {
        const piece = this.getPiece(x,y);
        const color = this.getColor(x,y);
        const oppCol = this.getOppCol(color);
        const adjacentSteps = V.steps[V.ROOK].concat(V.steps[V.BISHOP]);
        outerLoop:
        for (let step of adjacentSteps)
        {
            const [i,j] = [x+step[0],y+step[1]];
            if (V.OnBoard(i,j) && this.board[i][j] != V.EMPTY
                && this.getColor(i,j) == oppCol)
            {
                const oppPiece = this.getPiece(i,j);
                if (oppPiece == V.IMMOBILIZER)
                {
                    // Moving is impossible only if this immobilizer is not neutralized
                    for (let step2 of adjacentSteps)
                    {
                        const [i2,j2] = [i+step2[0],j+step2[1]];
                        if (i2 == x && j2 == y)
                            continue; //skip initial piece!
                        if (V.OnBoard(i2,j2) && this.board[i2][j2] != V.EMPTY
                            && this.getColor(i2,j2) == color)
                        {
                            if ([V.BISHOP,V.IMMOBILIZER].includes(this.getPiece(i2,j2)))
                                return false;
                        }
                    }
                    return true; //immobilizer isn't neutralized
                }
                // Chameleons can't be immobilized twice, because there is only one immobilizer
                if (oppPiece == V.BISHOP && piece == V.IMMOBILIZER)
                    return true;
            }
        }
        return false;
    }

    getPotentialMovesFrom([x,y])
    {
        // Pre-check: is thing on this square immobilized?
        if (this.isImmobilized([x,y]))
            return [];
        switch (this.getPiece(x,y))
        {
            case V.IMMOBILIZER:
                return this.getPotentialImmobilizerMoves([x,y]);
            default:
                return super.getPotentialMovesFrom([x,y]);
        }
    }

    getSlideNJumpMoves([x,y], steps, oneStep)
    {
        const color = this.getColor(x,y);
        const piece = this.getPiece(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];
            }
            // Only king can take on occupied square:
            if (piece==V.KING && V.OnBoard(i,j) && this.canTake([x,y], [i,j]))
                moves.push(this.getBasicMove([x,y], [i,j]));
        }
        return moves;
    }

    // Modify capturing moves among listed pawn moves
    addPawnCaptures(moves, byChameleon)
    {
        const steps = V.steps[V.ROOK];
        const color = this.turn;
        const oppCol = this.getOppCol(color);
        moves.forEach(m => {
            if (!!byChameleon && m.start.x!=m.end.x && m.start.y!=m.end.y)
                return; //chameleon not moving as pawn
            // Try capturing in every direction
            for (let step of steps)
            {
                const sq2 = [m.end.x+2*step[0],m.end.y+2*step[1]];
                if (V.OnBoard(sq2[0],sq2[1]) && this.board[sq2[0]][sq2[1]] != V.EMPTY
                    && this.getColor(sq2[0],sq2[1]) == color)
                {
                    // Potential capture
                    const sq1 = [m.end.x+step[0],m.end.y+step[1]];
                    if (this.board[sq1[0]][sq1[1]] != V.EMPTY
                        && this.getColor(sq1[0],sq1[1]) == oppCol)
                    {
                        const piece1 = this.getPiece(sq1[0],sq1[1]);
                        if (!byChameleon || piece1 == V.PAWN)
                        {
                            m.vanish.push(new PiPo({
                                x:sq1[0],
                                y:sq1[1],
                                c:oppCol,
                                p:piece1
                            }));
                        }
                    }
                }
            }
        });
    }

    // "Pincher"
    getPotentialPawnMoves([x,y])
    {
        let moves = super.getPotentialRookMoves([x,y]);
        this.addPawnCaptures(moves);
        return moves;
    }

    addRookCaptures(moves, byChameleon)
    {
        const color = this.turn;
        const oppCol = this.getOppCol(color);
        const kp = this.kingPos[color];
        moves.forEach(m => {
            // Check piece-king rectangle (if any) corners for enemy pieces
            if (m.end.x == kp[0] || m.end.y == kp[1])
                return; //"flat rectangle"
            const corner1 = [m.end.x, kp[1]];
            const corner2 = [kp[0], m.end.y];
            for (let [i,j] of [corner1,corner2])
            {
                if (this.board[i][j] != V.EMPTY && this.getColor(i,j) == oppCol)
                {
                    const piece = this.getPiece(i,j);
                    if (!byChameleon || piece == V.ROOK)
                    {
                        m.vanish.push( new PiPo({
                            x:i,
                            y:j,
                            p:piece,
                            c:oppCol
                        }) );
                    }
                }
            }
        });
    }

    // Coordinator
    getPotentialRookMoves(sq)
    {
        let moves = super.getPotentialQueenMoves(sq);
        this.addRookCaptures(moves);
        return moves;
    }

    // Long-leaper
    getKnightCaptures(startSquare, byChameleon)
    {
        // Look in every direction for captures
        const steps = V.steps[V.ROOK].concat(V.steps[V.BISHOP]);
        const color = this.turn;
        const oppCol = this.getOppCol(color);
        let moves = [];
        const [x,y] = [startSquare[0],startSquare[1]];
        const piece = this.getPiece(x,y); //might be a chameleon!
        outerLoop:
        for (let step of steps)
        {
            let [i,j] = [x+step[0], y+step[1]];
            while (V.OnBoard(i,j) && this.board[i][j]==V.EMPTY)
            {
                i += step[0];
                j += step[1];
            }
            if (!V.OnBoard(i,j) || this.getColor(i,j)==color
                || (!!byChameleon && this.getPiece(i,j)!=V.KNIGHT))
            {
                continue;
            }
            // last(thing), cur(thing) : stop if "cur" is our color, or beyond board limits,
            // or if "last" isn't empty and cur neither. Otherwise, if cur is empty then
            // add move until cur square; if cur is occupied then stop if !!byChameleon and
            // the square not occupied by a leaper.
            let last = [i,j];
            let cur = [i+step[0],j+step[1]];
            let vanished = [ new PiPo({x:x,y:y,c:color,p:piece}) ];
            while (V.OnBoard(cur[0],cur[1]))
            {
                if (this.board[last[0]][last[1]] != V.EMPTY)
                {
                    const oppPiece = this.getPiece(last[0],last[1]);
                    if (!!byChameleon && oppPiece != V.KNIGHT)
                        continue outerLoop;
                    // Something to eat:
                    vanished.push( new PiPo({x:last[0],y:last[1],c:oppCol,p:oppPiece}) );
                }
                if (this.board[cur[0]][cur[1]] != V.EMPTY)
                {
                    if (this.getColor(cur[0],cur[1]) == color
                        || this.board[last[0]][last[1]] != V.EMPTY) //TODO: redundant test
                    {
                        continue outerLoop;
                    }
                }
                else
                {
                    moves.push(new Move({
                        appear: [ new PiPo({x:cur[0],y:cur[1],c:color,p:piece}) ],
                        vanish: JSON.parse(JSON.stringify(vanished)), //TODO: required?
                        start: {x:x,y:y},
                        end: {x:cur[0],y:cur[1]}
                    }));
                }
                last = [last[0]+step[0],last[1]+step[1]];
                cur = [cur[0]+step[0],cur[1]+step[1]];
            }
        }
        return moves;
    }

    // Long-leaper
    getPotentialKnightMoves(sq)
    {
        return super.getPotentialQueenMoves(sq).concat(this.getKnightCaptures(sq));
    }

    getPotentialBishopMoves([x,y])
    {
        let moves = super.getPotentialQueenMoves([x,y])
            .concat(this.getKnightCaptures([x,y],"asChameleon"));
        // No "king capture" because king cannot remain under check
        this.addPawnCaptures(moves, "asChameleon");
        this.addRookCaptures(moves, "asChameleon");
        this.addQueenCaptures(moves, "asChameleon");
        // Post-processing: merge similar moves, concatenating vanish arrays
        let mergedMoves = {};
        moves.forEach(m => {
            const key = m.end.x + V.size.x * m.end.y;
            if (!mergedMoves[key])
                mergedMoves[key] = m;
            else
            {
                for (let i=1; i<m.vanish.length; i++)
                    mergedMoves[key].vanish.push(m.vanish[i]);
            }
        });
        // Finally return an array
        moves = [];
        Object.keys(mergedMoves).forEach(k => { moves.push(mergedMoves[k]); });
        return moves;
    }

    // Withdrawer
    addQueenCaptures(moves, byChameleon)
    {
        if (moves.length == 0)
            return;
        const [x,y] = [moves[0].start.x,moves[0].start.y];
        const adjacentSteps = V.steps[V.ROOK].concat(V.steps[V.BISHOP]);
        let capturingDirections = [];
        const color = this.turn;
        const oppCol = this.getOppCol(color);
        adjacentSteps.forEach(step => {
            const [i,j] = [x+step[0],y+step[1]];
            if (V.OnBoard(i,j) && this.board[i][j] != V.EMPTY && this.getColor(i,j) == oppCol
                && (!byChameleon || this.getPiece(i,j) == V.QUEEN))
            {
                capturingDirections.push(step);
            }
        });
        moves.forEach(m => {
            const step = [
                m.end.x!=x ? (m.end.x-x)/Math.abs(m.end.x-x) : 0,
                m.end.y!=y ? (m.end.y-y)/Math.abs(m.end.y-y) : 0
            ];
            // NOTE: includes() and even _.isEqual() functions fail...
            // TODO: this test should be done only once per direction
            if (capturingDirections.some(dir =>
                { return (dir[0]==-step[0] && dir[1]==-step[1]); }))
            {
                const [i,j] = [x-step[0],y-step[1]];
                m.vanish.push(new PiPo({
                    x:i,
                    y:j,
                    p:this.getPiece(i,j),
                    c:oppCol
                }));
            }
        });
    }

    getPotentialQueenMoves(sq)
    {
        let moves = super.getPotentialQueenMoves(sq);
        this.addQueenCaptures(moves);
        return moves;
    }

    getPotentialImmobilizerMoves(sq)
    {
        // Immobilizer doesn't capture
        return super.getPotentialQueenMoves(sq);
    }

    getPotentialKingMoves(sq)
    {
        return this.getSlideNJumpMoves(sq,
            V.steps[V.ROOK].concat(V.steps[V.BISHOP]), "oneStep");
    }

    // isAttacked() is OK because the immobilizer doesn't take

    isAttackedByPawn([x,y], colors)
    {
        // Square (x,y) must be surroundable by two enemy pieces,
        // and one of them at least should be a pawn (moving).
        const dirs = [ [1,0],[0,1] ];
        const steps = V.steps[V.ROOK];
        for (let dir of dirs)
        {
            const [i1,j1] = [x-dir[0],y-dir[1]]; //"before"
            const [i2,j2] = [x+dir[0],y+dir[1]]; //"after"
            if (V.OnBoard(i1,j1) && V.OnBoard(i2,j2))
            {
                if ((this.board[i1][j1]!=V.EMPTY && colors.includes(this.getColor(i1,j1))
                    && this.board[i2][j2]==V.EMPTY)
                        ||
                    (this.board[i2][j2]!=V.EMPTY && colors.includes(this.getColor(i2,j2))
                    && this.board[i1][j1]==V.EMPTY))
                {
                    // Search a movable enemy pawn landing on the empty square
                    for (let step of steps)
                    {
                        let [ii,jj] = (this.board[i1][j1]==V.EMPTY ? [i1,j1] : [i2,j2]);
                        let [i3,j3] = [ii+step[0],jj+step[1]];
                        while (V.OnBoard(i3,j3) && this.board[i3][j3]==V.EMPTY)
                        {
                            i3 += step[0];
                            j3 += step[1];
                        }
                        if (V.OnBoard(i3,j3) && colors.includes(this.getColor(i3,j3))
                            && this.getPiece(i3,j3) == V.PAWN && !this.isImmobilized([i3,j3]))
                        {
                            return true;
                        }
                    }
                }
            }
        }
        return false;
    }

    isAttackedByRook([x,y], colors)
    {
        // King must be on same column or row,
        // and a rook should be able to reach a capturing square
        // colors contains only one element, giving the oppCol and thus king position
        const sameRow = (x == this.kingPos[colors[0]][0]);
        const sameColumn = (y == this.kingPos[colors[0]][1]);
        if (sameRow || sameColumn)
        {
            // Look for the enemy rook (maximum 1)
            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 && colors.includes(this.getColor(i,j))
                        && this.getPiece(i,j) == V.ROOK)
                    {
                        if (this.isImmobilized([i,j]))
                            return false; //because only one rook
                        // Can it reach a capturing square?
                        // Easy but quite suboptimal way (TODO): generate all moves (turn is OK)
                        const moves = this.getPotentialMovesFrom([i,j]);
                        for (let move of moves)
                        {
                            if (sameRow && move.end.y == y || sameColumn && move.end.x == x)
                                return true;
                        }
                    }
                }
            }
        }
        return false;
    }

    isAttackedByKnight([x,y], colors)
    {
        // Square (x,y) must be on same line as a knight,
        // and there must be empty square(s) behind.
        const steps = V.steps[V.ROOK].concat(V.steps[V.BISHOP]);
        outerLoop:
        for (let step of steps)
        {
            const [i0,j0] = [x+step[0],y+step[1]];
            if (V.OnBoard(i0,j0) && this.board[i0][j0] == V.EMPTY)
            {
                // Try in opposite direction:
                let [i,j] = [x-step[0],y-step[1]];
                while (V.OnBoard(i,j))
                {
                    while (V.OnBoard(i,j) && this.board[i][j] == V.EMPTY)
                    {
                        i -= step[0];
                        j -= step[1];
                    }
                    if (V.OnBoard(i,j))
                    {
                        if (colors.includes(this.getColor(i,j)))
                        {
                            if (this.getPiece(i,j) == V.KNIGHT && !this.isImmobilized([i,j]))
                                return true;
                            continue outerLoop;
                        }
                        // [else] Our color, could be captured *if there was an empty space*
                        if (this.board[i+step[0]][j+step[1]] != V.EMPTY)
                            continue outerLoop;
                        i -= step[0];
                        j -= step[1];
                    }
                }
            }
        }
        return false;
    }

    isAttackedByBishop([x,y], colors)
    {
        // We cheat a little here: since this function is used exclusively for king,
        // it's enough to check the immediate surrounding of the square.
        const adjacentSteps = V.steps[V.ROOK].concat(V.steps[V.BISHOP]);
        for (let step of adjacentSteps)
        {
            const [i,j] = [x+step[0],y+step[1]];
            if (V.OnBoard(i,j) && this.board[i][j]!=V.EMPTY
                && colors.includes(this.getColor(i,j)) && this.getPiece(i,j) == V.BISHOP)
            {
                return true; //bishops are never immobilized
            }
        }
        return false;
    }

    isAttackedByQueen([x,y], colors)
    {
        // Square (x,y) must be adjacent to a queen, and the queen must have
        // some free space in the opposite direction from (x,y)
        const adjacentSteps = V.steps[V.ROOK].concat(V.steps[V.BISHOP]);
        for (let step of adjacentSteps)
        {
            const sq2 = [x+2*step[0],y+2*step[1]];
            if (V.OnBoard(sq2[0],sq2[1]) && this.board[sq2[0]][sq2[1]] == V.EMPTY)
            {
                const sq1 = [x+step[0],y+step[1]];
                if (this.board[sq1[0]][sq1[1]] != V.EMPTY
                    && colors.includes(this.getColor(sq1[0],sq1[1]))
                    && this.getPiece(sq1[0],sq1[1]) == V.QUEEN
                    && !this.isImmobilized(sq1))
                {
                    return true;
                }
            }
        }
        return false;
    }

    updateVariables(move)
    {
        // Just update king(s) position(s)
        const piece = this.getPiece(move.start.x,move.start.y);
        const c = this.getColor(move.start.x,move.start.y);
        if (piece == V.KING && move.appear.length > 0)
        {
            this.kingPos[c][0] = move.appear[0].x;
            this.kingPos[c][1] = move.appear[0].y;
        }
    }

    static get VALUES() { //TODO: totally experimental!
        return {
            'p': 1,
            'r': 2,
            'n': 5,
            'b': 3,
            'q': 3,
            'm': 5,
            'k': 1000
        };
    }

    static get SEARCH_DEPTH() { return 2; } //TODO?

    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 every piece, totally freely

            let randIndex = _.random(7);
            const bishop1Pos = positions[randIndex];
            positions.splice(randIndex, 1);

            randIndex = _.random(6);
            const bishop2Pos = positions[randIndex];
            positions.splice(randIndex, 1);

            randIndex = _.random(5);
            const knight1Pos = positions[randIndex];
            positions.splice(randIndex, 1);

            randIndex = _.random(4);
            const knight2Pos = positions[randIndex];
            positions.splice(randIndex, 1);

            randIndex = _.random(3);
            const queenPos = positions[randIndex];
            positions.splice(randIndex, 1);

            randIndex = _.random(2);
            const kingPos = positions[randIndex];
            positions.splice(randIndex, 1);

            randIndex = _.random(1);
            const rookPos = positions[randIndex];
            positions.splice(randIndex, 1);
            const immobilizerPos = positions[0];

            pieces[c][bishop1Pos] = 'b';
            pieces[c][bishop2Pos] = 'b';
            pieces[c][knight1Pos] = 'n';
            pieces[c][knight2Pos] = 'n';
            pieces[c][queenPos] = 'q';
            pieces[c][kingPos] = 'k';
            pieces[c][rookPos] = 'r';
            pieces[c][immobilizerPos] = 'm';
        }
        return pieces["b"].join("") +
            "/pppppppp/8/8/8/8/PPPPPPPP/" +
            pieces["w"].join("").toUpperCase() +
            " 0000"; //TODO: flags?!
    }

    getFlagsFen()
    {
        return "0000"; //TODO: or "-" ?
    }

    getNotation(move)
    {
        const initialSquare =
            String.fromCharCode(97 + move.start.y) + (V.size.x-move.start.x);
        const finalSquare = String.fromCharCode(97 + move.end.y) + (V.size.x-move.end.x);
        let notation = undefined;
        if (move.appear[0].p == V.PAWN)
        {
            // Pawn: generally ambiguous short notation, so we use full description
            notation = "P" + initialSquare + finalSquare;
        }
        else if (move.appear[0].p == V.KING)
            notation = "K" + (move.vanish.length>1 ? "x" : "") + finalSquare;
        else
            notation = move.appear[0].p.toUpperCase() + finalSquare;
        if (move.vanish.length > 1 && move.appear[0].p != V.KING)
            notation += "X"; //capture mark (not describing what is captured...)
        return notation;
    }
}