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     getPotentialPawnMoves([x,y])
  20     {
  21         const color = this.turn;
  22         let moves = [];
  23         const [sizeX,sizeY] = [V.size.x,V.size.y];
  24         const shift = (color == "w" ? -1 : 1);
  25         const firstRank = (color == 'w' ? sizeX-1 : 0);
  26         const startRank = (color == "w" ? sizeX-2 : 1);
  27         const lastRank = (color == "w" ? 0 : sizeX-1);
  28
  29         if (x+shift >= 0 && x+shift < sizeX && x+shift != lastRank)
  30         {
  31             // Normal moves
  32             if (this.board[x+shift][y] == V.EMPTY)
  33             {
  34                 moves.push(this.getBasicMove([x,y], [x+shift,y]));
  35                 // Next condition because variants with pawns on 1st rank allow them to jump
  36                 if ([startRank,firstRank].includes(x) && this.board[x+2*shift][y] == V.EMPTY)
  37                 {
  38                     // Two squares jump
  39                     moves.push(this.getBasicMove([x,y], [x+2*shift,y]));
  40                 }
  41             }
  42             // Captures
  43             if (y>0 && this.board[x+shift][y-1] != V.EMPTY
  44                 && this.canTake([x,y], [x+shift,y-1]))
  45             {
  46                 moves.push(this.getBasicMove([x,y], [x+shift,y-1]));
  47             }
  48             if (y<sizeY-1 && this.board[x+shift][y+1] != V.EMPTY
  49                 && this.canTake([x,y], [x+shift,y+1]))
  50             {
  51                 moves.push(this.getBasicMove([x,y], [x+shift,y+1]));
  52             }
  53         }
  54
  55         if (x+shift == lastRank)
  56         {
  57             // Promotion
  58             const pawnColor = this.getColor(x,y); //can be different for checkered
  59             let promotionPieces = [V.ROOK,V.KNIGHT,V.BISHOP,V.QUEEN];
  60             promotionPieces.forEach(p => {
  61                 // Normal move
  62                 if (this.board[x+shift][y] == V.EMPTY)
  63                     moves.push(this.getBasicMove([x,y], [x+shift,y], {c:pawnColor,p:p}));
  64                 // Captures
  65                 if (y>0 && this.board[x+shift][y-1] != V.EMPTY
  66                     && this.canTake([x,y], [x+shift,y-1]))
  67                 {
  68                     moves.push(this.getBasicMove([x,y], [x+shift,y-1], {c:pawnColor,p:p}));
  69                 }
  70                 if (y<sizeY-1 && this.board[x+shift][y+1] != V.EMPTY
  71                     && this.canTake([x,y], [x+shift,y+1]))
  72                 {
  73                     moves.push(this.getBasicMove([x,y], [x+shift,y+1], {c:pawnColor,p:p}));
  74                 }
  75             });
  76         }
  77         return moves; //no en-passant
  78     }
  79
  80     // Complete a move with magnetic actions
  81     // TODO: job is done multiple times for (normal) promotions.
  82     applyMagneticLaws(move)
  83     {
  84         if (move.appear[0].p == V.KING && move.appear.length==1)
  85             return [move]; //kings are not charged
  86         const aIdx = (move.appear[0].p != V.KING ? 0 : 1); //if castling, rook is charged
  87         const [x,y] = [move.appear[aIdx].x, move.appear[aIdx].y];
  88         const color = this.turn;
  89         const lastRank = (color=="w" ? 0 : 7);
  90         const standardMove = JSON.parse(JSON.stringify(move));
  91         this.play(standardMove);
  92         for (let step of [[-1,0],[1,0],[0,-1],[0,1]])
  93         {
  94             let [i,j] = [x+step[0],y+step[1]];
  95             while (V.OnBoard(i,j))
  96             {
  97                 if (this.board[i][j] != V.EMPTY)
  98                 {
  99                     // Found something. Same color or not?
 100                     if (this.getColor(i,j) != color)
 101                     {
 102                         // Attraction
 103                         if ((Math.abs(i-x)>=2 || Math.abs(j-y)>=2) && this.getPiece(i,j) != V.KING)
 104                         {
 105                             move.vanish.push(
 106                                 new PiPo({
 107                                     p:this.getPiece(i,j),
 108                                     c:this.getColor(i,j),
 109                                     x:i,
 110                                     y:j
 111                                 })
 112                             );
 113                             move.appear.push(
 114                                 new PiPo({
 115                                     p:this.getPiece(i,j),
 116                                     c:this.getColor(i,j),
 117                                     x:x+step[0],
 118                                     y:y+step[1]
 119                                 })
 120                             );
 121                         }
 122                     }
 123                     else
 124                     {
 125                         // Repulsion
 126                         if (this.getPiece(i,j) != V.KING)
 127                         {
 128                             // Push it until we meet an obstacle or edge of the board
 129                             let [ii,jj] = [i+step[0],j+step[1]];
 130                             while (V.OnBoard(ii,jj))
 131                             {
 132                                 if (this.board[ii][jj] != V.EMPTY)
 133                                     break;
 134                                 ii += step[0];
 135                                 jj += step[1];
 136                             }
 137                             ii -= step[0];
 138                             jj -= step[1];
 139                             if (Math.abs(ii-i)>=1 || Math.abs(jj-j)>=1)
 140                             {
 141                                 move.vanish.push(
 142                                     new PiPo({
 143                                         p:this.getPiece(i,j),
 144                                         c:this.getColor(i,j),
 145                                         x:i,
 146                                         y:j
 147                                     })
 148                                 );
 149                                 move.appear.push(
 150                                     new PiPo({
 151                                         p:this.getPiece(i,j),
 152                                         c:this.getColor(i,j),
 153                                         x:ii,
 154                                         y:jj
 155                                     })
 156                                 );
 157                             }
 158                         }
 159                     }
 160                     break;
 161                 }
 162                 i += step[0];
 163                 j += step[1];
 164             }
 165         }
 166         this.undo(standardMove);
 167         let moves = [];
 168         // Scan move for pawn (max 1) on 8th rank
 169         for (let i=1; i<move.appear.length; i++)
 170         {
 171             if (move.appear[i].p==V.PAWN && move.appear[i].c==color
 172                 && move.appear[i].x==lastRank)
 173             {
 174                 move.appear[i].p = V.ROOK;
 175                 moves.push(move);
 176                 for (let piece of [V.KNIGHT, V.BISHOP, V.QUEEN])
 177                 {
 178                     let cmove = JSON.parse(JSON.stringify(move));
 179                     cmove.appear[i].p = piece;
 180                     moves.push(cmove);
 181                 }
 182                 // Swap appear[i] and appear[0] for moves presentation (TODO: this is awkward)
 183                 moves.forEach(m => {
 184                     let tmp = m.appear[0];
 185                     m.appear[0] = m.appear[i];
 186                     m.appear[i] = tmp;
 187                 });
 188                 break;
 189             }
 190         }
 191         if (moves.length == 0) //no pawn on 8th rank
 192             moves.push(move);
 193         return moves;
 194     }
 195
 196     atLeastOneMove()
 197     {
 198         if (this.kingPos[this.turn][0] < 0)
 199             return false;
 200         return true; //TODO: is it right?
 201     }
 202
 203     underCheck(move)
 204     {
 205         return false; //there is no check
 206     }
 207
 208     getCheckSquares(move)
 209     {
 210         const c = this.getOppCol(this.turn); //opponent
 211         const saveKingPos = this.kingPos[c]; //king might be taken
 212         this.play(move);
 213         // The only way to be "under check" is to have lost the king (thus game over)
 214         let res = this.kingPos[c][0] < 0
 215             ? [JSON.parse(JSON.stringify(saveKingPos))]
 216             : [];
 217         this.undo(move);
 218         return res;
 219     }
 220
 221     updateVariables(move)
 222     {
 223         super.updateVariables(move);
 224         const c = this.getColor(move.start.x,move.start.y);
 225         if (this.board[move.end.x][move.end.y] != V.EMPTY
 226             && c != this.getColor(move.end.x,move.end.y)
 227             && this.getPiece(move.end.x,move.end.y) == V.KING)
 228         {
 229             // We took opponent king !
 230             const oppCol = this.getOppCol(c);
 231             this.kingPos[oppCol] = [-1,-1];
 232             this.castleFlags[oppCol] = [false,false];
 233         }
 234         // Did we magnetically move our (init) rooks or opponents' ones ?
 235         const firstRank = (c == "w" ? 7 : 0);
 236         const oppFirstRank = 7 - firstRank;
 237         const oppCol = this.getOppCol(c);
 238         move.vanish.forEach(psq => {
 239             if (psq.x == firstRank && this.INIT_COL_ROOK[c].includes(psq.y))
 240                 this.castleFlags[c][psq.y==this.INIT_COL_ROOK[c][0] ? 0 : 1] = false;
 241             else if (psq.x == oppFirstRank && this.INIT_COL_ROOK[oppCol].includes(psq.y))
 242                 this.castleFlags[oppCol][psq.y==this.INIT_COL_ROOK[oppCol][0] ? 0 : 1] = false;
 243         });
 244     }
 245
 246     unupdateVariables(move)
 247     {
 248         super.unupdateVariables(move);
 249         const c = this.getColor(move.start.x,move.start.y);
 250         const oppCol = this.getOppCol(c);
 251         if (this.kingPos[oppCol][0] < 0)
 252         {
 253             // Last move took opponent's king
 254             for (let psq of move.vanish)
 255             {
 256                 if (psq.p == 'k')
 257                 {
 258                     this.kingPos[oppCol] = [psq.x, psq.y];
 259                     break;
 260                 }
 261             }
 262         }
 263     }
 264
 265     checkGameEnd()
 266     {
 267         // No valid move: our king disappeared
 268         return this.turn == "w" ? "0-1" : "1-0";
 269     }
 270
 271     static get THRESHOLD_MATE()
 272     {
 273         return 500; //checkmates evals may be slightly below 1000
 274     }
 275 }
 276
 277 const VariantRules = MagneticRules;