public/javascripts/variants/Switching.js

   1 class SwitchingRules extends ChessRules
   2 {
   3     // Build switch move between squares x1,y1 and x2,y2
   4     getSwitchMove_s([x1,y1],[x2,y2])
   5     {
   6         const c = this.getColor(x1,y1); //same as color at square 2
   7         const p1 = this.getPiece(x1,y1);
   8         const p2 = this.getPiece(x2,y2);
   9         if (p1 == V.KING && p2 == V.ROOK)
  10             return []; //avoid duplicate moves (potential conflict with castle)
  11         let move = new Move({
  12             appear: [
  13                 new PiPo({x:x2,y:y2,c:c,p:p1}),
  14                 new PiPo({x:x1,y:y1,c:c,p:p2})
  15             ],
  16             vanish: [
  17                 new PiPo({x:x1,y:y1,c:c,p:p1}),
  18                 new PiPo({x:x2,y:y2,c:c,p:p2})
  19             ],
  20             start: {x:x1,y:y1},
  21             end: {x:x2,y:y2}
  22         });
  23         // Move completion: promote switched pawns (as in Magnetic)
  24         const lastRank = (c == "w" ? 0 : V.size.x-1);
  25         let moves = [];
  26         if ((p1==V.PAWN && x2==lastRank) || (p2==V.PAWN && x1==lastRank))
  27         {
  28             const idx = (p1==V.PAWN ? 0 : 1);
  29             move.appear[idx].p = V.ROOK;
  30             moves.push(move);
  31             for (let piece of [V.KNIGHT, V.BISHOP, V.QUEEN])
  32             {
  33                 let cmove = JSON.parse(JSON.stringify(move));
  34                 cmove.appear[idx].p = piece;
  35                 moves.push(cmove);
  36             }
  37             if (idx == 1)
  38             {
  39                 // Swap moves[i].appear[0] and [1] for moves presentation [TODO...]
  40                 moves.forEach(m => {
  41                     let tmp = m.appear[0];
  42                     m.appear[0] = m.appear[1];
  43                     m.appear[1] = tmp;
  44                 });
  45             }
  46         }
  47         else //other cases
  48             moves.push(move);
  49         return moves;
  50     }
  51
  52     getPotentialMovesFrom([x,y], computer)
  53     {
  54         let moves = super.getPotentialMovesFrom([x,y]);
  55         // Add switches: respecting chessboard ordering if "computer" is on
  56         const color = this.turn;
  57         const piece = this.getPiece(x,y);
  58         const steps = V.steps[V.ROOK].concat(V.steps[V.BISHOP]);
  59         const kp = this.kingPos[color];
  60         const oppCol = V.GetOppCol(color);
  61         for (let step of steps)
  62         {
  63             let [i,j] = [x+step[0],y+step[1]];
  64             if (!!computer && (i<x || (i==x && j<y)))
  65                 continue; //only switch with superior indices
  66             if (V.OnBoard(i,j) && this.board[i][j]!=V.EMPTY
  67                 && this.getColor(i,j)==color && this.getPiece(i,j)!=piece
  68                 // No switching under check (theoretically non-king pieces could, but not)
  69                 && !this.isAttacked(kp, [oppCol]))
  70             {
  71                 let switchMove_s = this.getSwitchMove_s([x,y],[i,j]);
  72                 if (switchMove_s.length == 1)
  73                     moves.push(switchMove_s[0]);
  74                 else //promotion
  75                     moves = moves.concat(switchMove_s);
  76             }
  77         }
  78         return moves;
  79     }
  80
  81     getAllValidMoves(computer)
  82     {
  83         const color = this.turn;
  84         const oppCol = V.GetOppCol(color);
  85         let potentialMoves = [];
  86         for (let i=0; i<V.size.x; i++)
  87         {
  88             for (let j=0; j<V.size.y; j++)
  89             {
  90                 if (this.board[i][j] != V.EMPTY && this.getColor(i,j) == color)
  91                 {
  92                     Array.prototype.push.apply(potentialMoves,
  93                         this.getPotentialMovesFrom([i,j], computer));
  94                 }
  95             }
  96         }
  97         return this.filterValid(potentialMoves);
  98     }
  99
 100     updateVariables(move)
 101     {
 102         super.updateVariables(move);
 103         if (move.appear.length == 2 && move.vanish.length == 2
 104             && move.appear[1].p == V.KING)
 105         {
 106             // Switch with the king; not castle, and not handled by main class
 107             const color = move.vanish[0].c;
 108             this.kingPos[color] = [move.appear[1].x, move.appear[1].y];
 109         }
 110     }
 111
 112     unupdateVariables(move)
 113     {
 114         super.unupdateVariables(move);
 115         if (move.appear.length == 2 && move.vanish.length == 2
 116             && move.appear[1].p == V.KING)
 117         {
 118             const color = move.vanish[0].c;
 119             this.kingPos[color] = [move.appear[0].x, move.appear[0].y];
 120         }
 121     }
 122
 123     static get SEARCH_DEPTH() { return 2; } //high branching factor
 124
 125     getNotation(move)
 126     {
 127         if (move.appear.length == 1)
 128             return super.getNotation(move); //no switch
 129         // Switch or castle
 130         if (move.appear[0].p == V.KING && move.appear[1].p == V.ROOK)
 131             return (move.end.y < move.start.y ? "0-0-0" : "0-0");
 132         // Switch:
 133         return "S" + V.CoordsToSquare(move.start) + V.CoordsToSquare(move.end);
 134     }
 135 }