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         let 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         return moves;
  20     }
  21
  22     // Complete a move with magnetic actions
  23     // TODO: job is done multiple times for (normal) promotions.
  24     applyMagneticLaws(move)
  25     {
  26         const V = VariantRules;
  27         if (move.appear[0].p == V.KING && move.appear.length==1)
  28             return [move]; //kings are not charged
  29         const aIdx = (move.appear[0].p != V.KING ? 0 : 1); //if castling, rook is charged
  30         const [x,y] = [move.appear[aIdx].x, move.appear[aIdx].y];
  31         const color = this.turn;
  32         const lastRank = (color=="w" ? 0 : 7);
  33         const standardMove = JSON.parse(JSON.stringify(move));
  34         this.play(standardMove);
  35         const [sizeX,sizeY] = V.size;
  36         for (let step of [[-1,0],[1,0],[0,-1],[0,1]])
  37         {
  38             let [i,j] = [x+step[0],y+step[1]];
  39             while (i>=0 && i<sizeX && j>=0 && j<sizeY)
  40             {
  41                 if (this.board[i][j] != V.EMPTY)
  42                 {
  43                     // Found something. Same color or not?
  44                     if (this.getColor(i,j) != color)
  45                     {
  46                         // Attraction
  47                         if ((Math.abs(i-x)>=2 || Math.abs(j-y)>=2) && this.getPiece(i,j) != V.KING)
  48                         {
  49                             move.vanish.push(
  50                                 new PiPo({
  51                                     p:this.getPiece(i,j),
  52                                     c:this.getColor(i,j),
  53                                     x:i,
  54                                     y:j
  55                                 })
  56                             );
  57                             move.appear.push(
  58                                 new PiPo({
  59                                     p:this.getPiece(i,j),
  60                                     c:this.getColor(i,j),
  61                                     x:x+step[0],
  62                                     y:y+step[1]
  63                                 })
  64                             );
  65                         }
  66                     }
  67                     else
  68                     {
  69                         // Repulsion
  70                         if (this.getPiece(i,j) != V.KING)
  71                         {
  72                             // Push it until we meet an obstacle or edge of the board
  73                             let [ii,jj] = [i+step[0],j+step[1]];
  74                             while (ii>=0 && ii<sizeX && jj>=0 && jj<sizeY)
  75                             {
  76                                 if (this.board[ii][jj] != V.EMPTY)
  77                                     break;
  78                                 ii += step[0];
  79                                 jj += step[1];
  80                             }
  81                             ii -= step[0];
  82                             jj -= step[1];
  83                             if (Math.abs(ii-i)>=1 || Math.abs(jj-j)>=1)
  84                             {
  85                                 move.vanish.push(
  86                                     new PiPo({
  87                                         p:this.getPiece(i,j),
  88                                         c:this.getColor(i,j),
  89                                         x:i,
  90                                         y:j
  91                                     })
  92                                 );
  93                                 move.appear.push(
  94                                     new PiPo({
  95                                         p:this.getPiece(i,j),
  96                                         c:this.getColor(i,j),
  97                                         x:ii,
  98                                         y:jj
  99                                     })
 100                                 );
 101                             }
 102                         }
 103                     }
 104                     break;
 105                 }
 106                 i += step[0];
 107                 j += step[1];
 108             }
 109         }
 110         this.undo(standardMove);
 111         let moves = [];
 112         // Scan move for pawn (max 1) on 8th rank
 113         for (let i=1; i<move.appear.length; i++)
 114         {
 115             if (move.appear[i].p==V.PAWN && move.appear[i].x==lastRank)
 116             {
 117                 move.appear[i].p = V.ROOK;
 118                 moves.push(move);
 119                 for (let piece of [V.KNIGHT, V.BISHOP, V.QUEEN])
 120                 {
 121                     let cmove = JSON.parse(JSON.stringify(move));
 122                     cmove.appear[i].p = piece;
 123                     moves.push(cmove);
 124                 }
 125                 // Swap appear[i] and appear[0] for moves presentation (TODO: this is awkward)
 126                 moves.forEach(m => {
 127                     let tmp = m.appear[0];
 128                     m.appear[0] = m.appear[i];
 129                     m.appear[i] = tmp;
 130                 });
 131                 break;
 132             }
 133         }
 134         if (moves.length == 0) //no pawn on 8th rank
 135             moves.push(move);
 136         return moves;
 137     }
 138
 139     // TODO: verify this assertion
 140     atLeastOneMove()
 141     {
 142         return true; //always at least one possible move
 143     }
 144
 145     underCheck(move)
 146     {
 147         return false; //there is no check
 148     }
 149
 150     getCheckSquares(move)
 151     {
 152         const c = this.getOppCol(this.turn); //opponent
 153         const saveKingPos = this.kingPos[c]; //king might be taken
 154         this.play(move);
 155         // The only way to be "under check" is to have lost the king (thus game over)
 156         let res = this.kingPos[c][0] < 0
 157             ? [ JSON.parse(JSON.stringify(saveKingPos)) ]
 158             : [ ];
 159         this.undo(move);
 160         return res;
 161     }
 162
 163     updateVariables(move)
 164     {
 165         super.updateVariables(move);
 166         const c = this.getColor(move.start.x,move.start.y);
 167         if (c != this.getColor(move.end.x,move.end.y)
 168             && this.board[move.end.x][move.end.y] != VariantRules.EMPTY
 169             && this.getPiece(move.end.x,move.end.y) == VariantRules.KING)
 170         {
 171             // We took opponent king !
 172             const oppCol = this.getOppCol(c);
 173             this.kingPos[oppCol] = [-1,-1];
 174             this.castleFlags[oppCol] = [false,false];
 175         }
 176     }
 177
 178     unupdateVariables(move)
 179     {
 180         super.unupdateVariables(move);
 181         const c = this.getColor(move.start.x,move.start.y);
 182         const oppCol = this.getOppCol(c);
 183         if (this.kingPos[oppCol][0] < 0)
 184         {
 185             // Last move took opponent's king
 186             for (let psq of move.vanish)
 187             {
 188                 if (psq.p == 'k')
 189                 {
 190                     this.kingPos[oppCol] = [psq.x, psq.y];
 191                     break;
 192                 }
 193             }
 194         }
 195     }
 196
 197     checkGameOver()
 198     {
 199         if (this.checkRepetition())
 200             return "1/2";
 201
 202         const color = this.turn;
 203         // TODO: do we need "atLeastOneMove()"?
 204         if (this.atLeastOneMove() && this.kingPos[color][0] >= 0)
 205             return "*";
 206
 207         return this.checkGameEnd();
 208     }
 209
 210     checkGameEnd()
 211     {
 212         // No valid move: our king disappeared
 213         return this.turn == "w" ? "0-1" : "1-0";
 214     }
 215 }