public/javascripts/variants/Extinction.js

   1 class ExtinctionRules extends ChessRules
   2 {
   3     initVariables(fen)
   4     {
   5         super.initVariables(fen);
   6         const V = VariantRules;
   7         this.material =
   8         {
   9             "w":
  10             {
  11                 [V.KING]: 1,
  12                 [V.QUEEN]: 1,
  13                 [V.ROOK]: 2,
  14                 [V.KNIGHT]: 2,
  15                 [V.BISHOP]: 2,
  16                 [V.PAWN]: 8
  17             },
  18             "b":
  19             {
  20                 [V.KING]: 1,
  21                 [V.QUEEN]: 1,
  22                 [V.ROOK]: 2,
  23                 [V.KNIGHT]: 2,
  24                 [V.BISHOP]: 2,
  25                 [V.PAWN]: 8
  26             }
  27         };
  28     }
  29
  30     getPotentialPawnMoves([x,y])
  31     {
  32         let moves = super.getPotentialPawnMoves([x,y]);
  33         // Add potential promotions into king
  34         const color = this.turn;
  35         const V = VariantRules;
  36         const [sizeX,sizeY] = V.size;
  37         const shift = (color == "w" ? -1 : 1);
  38         const lastRank = (color == "w" ? 0 : sizeX-1);
  39
  40         if (x+shift == lastRank)
  41         {
  42             // Normal move
  43             if (this.board[x+shift][y] == V.EMPTY)
  44                 moves.push(this.getBasicMove([x,y], [x+shift,y], {c:color,p:V.KING}));
  45             // Captures
  46             if (y>0 && this.canTake([x,y], [x+shift,y-1])
  47                 && this.board[x+shift][y-1] != V.EMPTY)
  48             {
  49                 moves.push(this.getBasicMove([x,y], [x+shift,y-1], {c:color,p:V.KING}));
  50             }
  51             if (y<sizeY-1 && this.canTake([x,y], [x+shift,y+1])
  52                 && this.board[x+shift][y+1] != V.EMPTY)
  53             {
  54                 moves.push(this.getBasicMove([x,y], [x+shift,y+1], {c:color,p:V.KING}));
  55             }
  56         }
  57
  58         return moves;
  59     }
  60
  61     // TODO: verify this assertion
  62     atLeastOneMove()
  63     {
  64         return true; //always at least one possible move
  65     }
  66
  67     underCheck(move)
  68     {
  69         return false; //there is no check
  70     }
  71
  72     getCheckSquares(move)
  73     {
  74         return [];
  75     }
  76
  77     updateVariables(move)
  78     {
  79         super.updateVariables(move);
  80         // Treat the promotion case: (not the capture part)
  81         if (move.appear[0].p != move.vanish[0].p)
  82         {
  83             this.material[move.appear[0].c][move.appear[0].p]++;
  84             this.material[move.appear[0].c][VariantRules.PAWN]--;
  85         }
  86         if (move.vanish.length==2 && move.appear.length==1) //capture
  87             this.material[move.vanish[1].c][move.vanish[1].p]--;
  88     }
  89
  90     unupdateVariables(move)
  91     {
  92         super.unupdateVariables(move);
  93         if (move.appear[0].p != move.vanish[0].p)
  94         {
  95             this.material[move.appear[0].c][move.appear[0].p]--;
  96             this.material[move.appear[0].c][VariantRules.PAWN]++;
  97         }
  98         if (move.vanish.length==2 && move.appear.length==1)
  99             this.material[move.vanish[1].c][move.vanish[1].p]++;
 100     }
 101
 102     checkGameOver()
 103     {
 104         if (this.checkRepetition())
 105             return "1/2";
 106
 107         if (this.atLeastOneMove()) // game not over?
 108         {
 109             const color = this.turn;
 110             if (Object.keys(this.material[color]).some(
 111                 p => { return this.material[color][p] == 0; }))
 112             {
 113                 return this.checkGameEnd();
 114             }
 115             return "*";
 116         }
 117
 118         return this.checkGameEnd(); //NOTE: currently unreachable...
 119     }
 120
 121     checkGameEnd()
 122     {
 123         return this.turn == "w" ? "0-1" : "1-0";
 124     }
 125
 126     evalPosition()
 127     {
 128         const color = this.turn;
 129         if (Object.keys(this.material[color]).some(
 130             p => { return this.material[color][p] == 0; }))
 131         {
 132             // Very negative (resp. positive) if white (reps. black) pieces set is incomplete
 133             return (color=="w"?-1:1) * VariantRules.INFINITY;
 134         }
 135         return super.evalPosition();
 136     }
 137 }