public/javascripts/variants/Magnetic.js

   1 class MagneticRules extends ChessRules
   2 {
   3     static get HasEnpassant() { return false; }
   4
   5     getPotentialMovesFrom([x,y])
   6     {
   7         let standardMoves = super.getPotentialMovesFrom([x,y]);
   8         let moves = [];
   9         standardMoves.forEach(m => {
  10             let newMove_s = this.applyMagneticLaws(m);
  11             if (newMove_s.length == 1)
  12                 moves.push(newMove_s[0]);
  13             else //promotion
  14                 moves = moves.concat(newMove_s);
  15         });
  16         return moves;
  17     }
  18
  19     // Complete a move with magnetic actions
  20     // TODO: job is done multiple times for (normal) promotions.
  21     applyMagneticLaws(move)
  22     {
  23         if (move.appear[0].p == V.KING && move.appear.length==1)
  24             return [move]; //kings are not charged
  25         const aIdx = (move.appear[0].p != V.KING ? 0 : 1); //if castling, rook is charged
  26         const [x,y] = [move.appear[aIdx].x, move.appear[aIdx].y];
  27         const color = this.turn;
  28         const lastRank = (color=="w" ? 0 : 7);
  29         const standardMove = JSON.parse(JSON.stringify(move));
  30         this.play(standardMove);
  31         for (let step of [[-1,0],[1,0],[0,-1],[0,1]])
  32         {
  33             let [i,j] = [x+step[0],y+step[1]];
  34             while (V.OnBoard(i,j))
  35             {
  36                 if (this.board[i][j] != V.EMPTY)
  37                 {
  38                     // Found something. Same color or not?
  39                     if (this.getColor(i,j) != color)
  40                     {
  41                         // Attraction
  42                         if ((Math.abs(i-x)>=2 || Math.abs(j-y)>=2) && this.getPiece(i,j) != V.KING)
  43                         {
  44                             move.vanish.push(
  45                                 new PiPo({
  46                                     p:this.getPiece(i,j),
  47                                     c:this.getColor(i,j),
  48                                     x:i,
  49                                     y:j
  50                                 })
  51                             );
  52                             move.appear.push(
  53                                 new PiPo({
  54                                     p:this.getPiece(i,j),
  55                                     c:this.getColor(i,j),
  56                                     x:x+step[0],
  57                                     y:y+step[1]
  58                                 })
  59                             );
  60                         }
  61                     }
  62                     else
  63                     {
  64                         // Repulsion
  65                         if (this.getPiece(i,j) != V.KING)
  66                         {
  67                             // Push it until we meet an obstacle or edge of the board
  68                             let [ii,jj] = [i+step[0],j+step[1]];
  69                             while (V.OnBoard(ii,jj))
  70                             {
  71                                 if (this.board[ii][jj] != V.EMPTY)
  72                                     break;
  73                                 ii += step[0];
  74                                 jj += step[1];
  75                             }
  76                             ii -= step[0];
  77                             jj -= step[1];
  78                             if (Math.abs(ii-i)>=1 || Math.abs(jj-j)>=1)
  79                             {
  80                                 move.vanish.push(
  81                                     new PiPo({
  82                                         p:this.getPiece(i,j),
  83                                         c:this.getColor(i,j),
  84                                         x:i,
  85                                         y:j
  86                                     })
  87                                 );
  88                                 move.appear.push(
  89                                     new PiPo({
  90                                         p:this.getPiece(i,j),
  91                                         c:this.getColor(i,j),
  92                                         x:ii,
  93                                         y:jj
  94                                     })
  95                                 );
  96                             }
  97                         }
  98                     }
  99                     break;
 100                 }
 101                 i += step[0];
 102                 j += step[1];
 103             }
 104         }
 105         this.undo(standardMove);
 106         let moves = [];
 107         // Scan move for pawn (max 1) on 8th rank
 108         for (let i=1; i<move.appear.length; i++)
 109         {
 110             if (move.appear[i].p==V.PAWN && move.appear[i].c==color
 111                 && move.appear[i].x==lastRank)
 112             {
 113                 move.appear[i].p = V.ROOK;
 114                 moves.push(move);
 115                 for (let piece of [V.KNIGHT, V.BISHOP, V.QUEEN])
 116                 {
 117                     let cmove = JSON.parse(JSON.stringify(move));
 118                     cmove.appear[i].p = piece;
 119                     moves.push(cmove);
 120                 }
 121                 // Swap appear[i] and appear[0] for moves presentation (TODO: this is awkward)
 122                 moves.forEach(m => {
 123                     let tmp = m.appear[0];
 124                     m.appear[0] = m.appear[i];
 125                     m.appear[i] = tmp;
 126                 });
 127                 break;
 128             }
 129         }
 130         if (moves.length == 0) //no pawn on 8th rank
 131             moves.push(move);
 132         return moves;
 133     }
 134
 135     atLeastOneMove()
 136     {
 137         if (this.kingPos[this.turn][0] < 0)
 138             return false;
 139         return true; //TODO: is it right?
 140     }
 141
 142     underCheck(move)
 143     {
 144         return false; //there is no check
 145     }
 146
 147     getCheckSquares(move)
 148     {
 149         const c = this.getOppCol(this.turn); //opponent
 150         const saveKingPos = this.kingPos[c]; //king might be taken
 151         this.play(move);
 152         // The only way to be "under check" is to have lost the king (thus game over)
 153         let res = this.kingPos[c][0] < 0
 154             ? [JSON.parse(JSON.stringify(saveKingPos))]
 155             : [];
 156         this.undo(move);
 157         return res;
 158     }
 159
 160     updateVariables(move)
 161     {
 162         super.updateVariables(move);
 163         const c = this.getColor(move.start.x,move.start.y);
 164         if (this.board[move.end.x][move.end.y] != V.EMPTY
 165             && c != this.getColor(move.end.x,move.end.y)
 166             && this.getPiece(move.end.x,move.end.y) == V.KING)
 167         {
 168             // We took opponent king !
 169             const oppCol = this.getOppCol(c);
 170             this.kingPos[oppCol] = [-1,-1];
 171             this.castleFlags[oppCol] = [false,false];
 172         }
 173         // Did we magnetically move our (init) rooks or opponents' ones ?
 174         const firstRank = (c == "w" ? 7 : 0);
 175         const oppFirstRank = 7 - firstRank;
 176         const oppCol = this.getOppCol(c);
 177         move.vanish.forEach(psq => {
 178             if (psq.x == firstRank && this.INIT_COL_ROOK[c].includes(psq.y))
 179                 this.castleFlags[c][psq.y==this.INIT_COL_ROOK[c][0] ? 0 : 1] = false;
 180             else if (psq.x == oppFirstRank && this.INIT_COL_ROOK[oppCol].includes(psq.y))
 181                 this.castleFlags[oppCol][psq.y==this.INIT_COL_ROOK[oppCol][0] ? 0 : 1] = false;
 182         });
 183     }
 184
 185     unupdateVariables(move)
 186     {
 187         super.unupdateVariables(move);
 188         const c = this.getColor(move.start.x,move.start.y);
 189         const oppCol = this.getOppCol(c);
 190         if (this.kingPos[oppCol][0] < 0)
 191         {
 192             // Last move took opponent's king
 193             for (let psq of move.vanish)
 194             {
 195                 if (psq.p == 'k')
 196                 {
 197                     this.kingPos[oppCol] = [psq.x, psq.y];
 198                     break;
 199                 }
 200             }
 201         }
 202     }
 203
 204     checkGameEnd()
 205     {
 206         // No valid move: our king disappeared
 207         return this.turn == "w" ? "0-1" : "1-0";
 208     }
 209
 210     static get THRESHOLD_MATE()
 211     {
 212         return 500; //checkmates evals may be slightly below 1000
 213     }
 214 }
 215
 216 const VariantRules = MagneticRules;