public/javascripts/variants/Magnetic.js

   1 class MagneticRules extends ChessRules
   2 {
   3     getEpSquare(move)
   4     {
   5         return undefined; //no en-passant
   6     }
   7
   8     getPotentialMovesFrom([x,y])
   9     {
  10         const standardMoves = super.getPotentialMovesFrom([x,y]);
  11         let moves = [];
  12         standardMoves.forEach(m => {
  13             let newMove_s = this.applyMagneticLaws(m);
  14             if (newMove_s.length == 1)
  15                 moves.push(newMove_s[0]);
  16             else //promotion
  17                 moves = moves.concat(moves, newMove_s);
  18         });
  19     }
  20
  21     // Complete a move with magnetic actions
  22     applyMagneticLaws(standardMove)
  23     {
  24         const [x,y] = [moves.start.x, move.start.y];
  25         let move = JSON.parse(JSON.stringify(standardMove));
  26         this.play(standardMove);
  27         const color = this.getColor(x,y);
  28         const [sizeX,sizeY] = VariantRules.size;
  29         for (let step of [[-1,0],[1,0],[0,-1],[0,1]])
  30         {
  31             let [i,j] = [x+step[0],y+step[1]];
  32             while (i>=0 && i<sizeX && j>=0 && j<sizeY)
  33             {
  34                 if (this.board[i][j] != VariantRules.EMPTY)
  35                 {
  36                     // Found something. Same color or not?
  37                     if (this.getColor(i,j) != color)
  38                     {
  39                         // Attraction
  40                         if ((Math.abs(i-x)>=2 || Math.abs(j-y)>=2)
  41                             && this.getPiece(i,j) != VariantRules.KING)
  42                         {
  43                             move.vanish.push(
  44                                 new PiPo({
  45                                     p:this.getPiece(i,j),
  46                                     c:this.getColor(i,j),
  47                                     x:i,
  48                                     y:j
  49                                 })
  50                             );
  51                             move.appear.push(
  52                                 new PiPo({
  53                                     p:this.getPiece(i,j),
  54                                     c:this.getColor(i,j),
  55                                     x:x+step[0],
  56                                     y:y+step[1]
  57                                 })
  58                             );
  59                         }
  60                     }
  61                     else
  62                     {
  63                         // Repulsion
  64                         if (this.getPiece(i,j) != VariantRules.KING)
  65                         {
  66                             // Push it until we meet an obstacle or edge of the board
  67                             let [ii,jj] = [i+step[0],j+step[1]];
  68                             while (ii>=0 && ii<sizeX && jj>=0 && jj<sizeY)
  69                             {
  70                                 if (this.board[ii][jj] != VariantRules.EMPTY)
  71                                     break;
  72                                 ii += step[0];
  73                                 jj += step[1];
  74                             }
  75                             ii -= step[0];
  76                             jj -= step[1];
  77                             if (Math.abs(ii-i)>=1 || Math.abs(jj-j)>=1)
  78                             {
  79                                 move.vanish.push(
  80                                     new PiPo({
  81                                         p:this.getPiece(i,j),
  82                                         c:this.getColor(i,j),
  83                                         x:i,
  84                                         y:j
  85                                     })
  86                                 );
  87                                 move.appear.push(
  88                                     new PiPo({
  89                                         p:this.getPiece(i,j),
  90                                         c:this.getColor(i,j),
  91                                         x:ii,
  92                                         y:jj
  93                                     })
  94                                 );
  95                             }
  96                         }
  97                     }
  98                     break;
  99                 }
 100                 i += step[0];
 101                 j += step[1];
 102             }
 103         }
 104         this.undo(standardMove);
 105         let moves = [];
 106         if (..condition pawn promote)
 107         {
 108             move. ... = ... //loop
 109             moves.push(...);
 110         }
 111         else
 112             moves.push(move);
 113         return moves;
 114     }
 115
 116     // TODO: verify this assertion
 117     atLeastOneMove()
 118     {
 119         return true; //always at least one possible move
 120     }
 121
 122     underCheck(move)
 123     {
 124         return false; //there is no check
 125     }
 126
 127     getCheckSquares(move)
 128     {
 129         const c = this.getOppCol(this.turn); //opponent
 130         const saveKingPos = this.kingPos[c]; //king might be taken
 131         this.play(move);
 132         // The only way to be "under check" is to have lost the king (thus game over)
 133         let res = this.kingPos[c][0] < 0
 134             ? [ JSON.parse(JSON.stringify(saveKingPos)) ]
 135             : [ ];
 136         this.undo(move);
 137         return res;
 138     }
 139
 140     updateVariables(move)
 141     {
 142         super.updateVariables(move);
 143         const c = this.getColor(move.start.x,move.start.y);
 144         if (c != this.getColor(move.end.x,move.end.y)
 145             && this.board[move.end.x][move.end.y] != VariantRules.EMPTY
 146             && this.getPiece(move.end.x,move.end.y) == VariantRules.KING)
 147         {
 148             // We took opponent king !
 149             const oppCol = this.getOppCol(c);
 150             this.kingPos[oppCol] = [-1,-1];
 151             this.castleFlags[oppCol] = [false,false];
 152         }
 153     }
 154
 155     unupdateVariables(move)
 156     {
 157         super.unupdateVariables(move);
 158         const c = this.getColor(move.start.x,move.start.y);
 159         const oppCol = this.getOppCol(c);
 160         if (this.kingPos[oppCol][0] < 0)
 161         {
 162             // Last move took opponent's king
 163             for (let psq of move.vanish)
 164             {
 165                 if (psq.p == 'k')
 166                 {
 167                     this.kingPos[oppCol] = [psq.x, psq.y];
 168                     break;
 169                 }
 170             }
 171         }
 172     }
 173
 174     checkGameOver()
 175     {
 176         if (this.checkRepetition())
 177             return "1/2";
 178
 179         const color = this.turn;
 180         // TODO: do we need "atLeastOneMove()"?
 181         if (this.atLeastOneMove() && this.kingPos[color][0] >= 0)
 182             return "*";
 183
 184         return this.checkGameEnd();
 185     }
 186
 187     checkGameEnd()
 188     {
 189         // No valid move: our king disappeared
 190         return this.turn == "w" ? "0-1" : "1-0";
 191     }
 192 }