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
   7         const c = this.getColor(x1,y1); //same as color at square 2
   8         const p1 = this.getPiece(x1,y1);
   9         const p2 = this.getPiece(x2,y2);
  10         let move = new Move({
  11             appear: [
  12                 new PiPo({x:x2,y:y2,c:c,p:p1}),
  13                 new PiPo({x:x1,y:y1,c:c,p:p2})
  14             ],
  15             vanish: [
  16                 new PiPo({x:x1,y:y1,c:c,p:p1}),
  17                 new PiPo({x:x2,y:y2,c:c,p:p2})
  18             ],
  19             start: {x:x1,y:y1},
  20             end: {x:x2,y:y2}
  21         });
  22         // Move completion: promote switched pawns (as in Magnetic)
  23         const sizeX = VariantRules.size[0];
  24         const lastRank = (c == "w" ? 0 : sizeX-1);
  25         const V = VariantRules;
  26         let moves = [];
  27         if (p1==V.PAWN && x2==lastRank) //TODO: also the case p2==V.PAWN and x1==lastRank! see Magnetic chess
  28         {
  29             move.appear[0].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[0].p = piece;
  35                 moves.push(cmove);
  36             }
  37         }
  38         else //other cases
  39             moves.push(move);
  40         return moves;
  41     }
  42
  43     getPotentialMovesFrom([x,y])
  44     {
  45         let moves = super.getPotentialMovesFrom([x,y]);
  46         // Add switches:
  47         const V = VariantRules;
  48         const color = this.turn;
  49         const piece = this.getPiece(x,y);
  50         const [sizeX,sizeY] = V.size;
  51         const steps = V.steps[V.ROOK].concat(V.steps[V.BISHOP]);
  52         const kp = this.kingPos[color];
  53         const oppCol = this.getOppCol(color);
  54         for (let step of steps)
  55         {
  56             let [i,j] = [x+step[0],y+step[1]];
  57             if (i>=0 && i<sizeX && j>=0 && j<sizeY && this.board[i][j]!=V.EMPTY
  58                 && this.getColor(i,j)==color && this.getPiece(i,j)!=piece
  59                 // No switching under check (theoretically non-king pieces could, but not)
  60                 && !this.isAttacked(kp, [oppCol]))
  61             {
  62                 let switchMove_s = this.getSwitchMove_s([x,y],[i,j]);
  63                 if (switchMove_s.length == 1)
  64                     moves.push(switchMove_s[0]);
  65                 else //promotion
  66                     moves = moves.concat(switchMove_s);
  67             }
  68         }
  69         return moves;
  70     }
  71
  72     static get SEARCH_DEPTH() { return 2; } //branching factor is quite high
  73 }