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(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].c==color
 116                 && move.appear[i].x==lastRank)
 117             {
 118                 move.appear[i].p = V.ROOK;
 119                 moves.push(move);
 120                 for (let piece of [V.KNIGHT, V.BISHOP, V.QUEEN])
 121                 {
 122                     let cmove = JSON.parse(JSON.stringify(move));
 123                     cmove.appear[i].p = piece;
 124                     moves.push(cmove);
 125                 }
 126                 // Swap appear[i] and appear[0] for moves presentation (TODO: this is awkward)
 127                 moves.forEach(m => {
 128                     let tmp = m.appear[0];
 129                     m.appear[0] = m.appear[i];
 130                     m.appear[i] = tmp;
 131                 });
 132                 break;
 133             }
 134         }
 135         if (moves.length == 0) //no pawn on 8th rank
 136             moves.push(move);
 137         return moves;
 138     }
 139
 140     // TODO: verify this assertion
 141     atLeastOneMove()
 142     {
 143         return true; //always at least one possible move
 144     }
 145
 146     underCheck(move)
 147     {
 148         return false; //there is no check
 149     }
 150
 151     getCheckSquares(move)
 152     {
 153         const c = this.getOppCol(this.turn); //opponent
 154         const saveKingPos = this.kingPos[c]; //king might be taken
 155         this.play(move);
 156         // The only way to be "under check" is to have lost the king (thus game over)
 157         let res = this.kingPos[c][0] < 0
 158             ? [ JSON.parse(JSON.stringify(saveKingPos)) ]
 159             : [ ];
 160         this.undo(move);
 161         return res;
 162     }
 163
 164     updateVariables(move)
 165     {
 166         super.updateVariables(move);
 167         const c = this.getColor(move.start.x,move.start.y);
 168         if (this.board[move.end.x][move.end.y] != VariantRules.EMPTY
 169             && c != this.getColor(move.end.x,move.end.y)
 170             && this.getPiece(move.end.x,move.end.y) == VariantRules.KING)
 171         {
 172             // We took opponent king !
 173             const oppCol = this.getOppCol(c);
 174             this.kingPos[oppCol] = [-1,-1];
 175             this.castleFlags[oppCol] = [false,false];
 176         }
 177         // Did we magnetically move our (init) rooks or opponents' ones ?
 178         const firstRank = (c == "w" ? 7 : 0);
 179         const oppFirstRank = 7 - firstRank;
 180         const oppCol = this.getOppCol(c);
 181         move.vanish.forEach(psq => {
 182             if (psq.x == firstRank && this.INIT_COL_ROOK[c].includes(psq.y))
 183                 this.castleFlags[c][psq.y==this.INIT_COL_ROOK[c][0] ? 0 : 1] = false;
 184             else if (psq.x == oppFirstRank && this.INIT_COL_ROOK[oppCol].includes(psq.y))
 185                 this.castleFlags[oppCol][psq.y==this.INIT_COL_ROOK[oppCol][0] ? 0 : 1] = false;
 186         });
 187     }
 188
 189     unupdateVariables(move)
 190     {
 191         super.unupdateVariables(move);
 192         const c = this.getColor(move.start.x,move.start.y);
 193         const oppCol = this.getOppCol(c);
 194         if (this.kingPos[oppCol][0] < 0)
 195         {
 196             // Last move took opponent's king
 197             for (let psq of move.vanish)
 198             {
 199                 if (psq.p == 'k')
 200                 {
 201                     this.kingPos[oppCol] = [psq.x, psq.y];
 202                     break;
 203                 }
 204             }
 205         }
 206     }
 207
 208     checkGameOver()
 209     {
 210         if (this.checkRepetition())
 211             return "1/2";
 212
 213         const color = this.turn;
 214         // TODO: do we need "atLeastOneMove()"?
 215         if (this.atLeastOneMove() && this.kingPos[color][0] >= 0)
 216             return "*";
 217
 218         return this.checkGameEnd();
 219     }
 220
 221     checkGameEnd()
 222     {
 223         // No valid move: our king disappeared
 224         return this.turn == "w" ? "0-1" : "1-0";
 225     }
 226
 227     static get THRESHOLD_MATE() {
 228         return 500; //checkmates evals may be slightly below 1000
 229     }
 230 }