client/src/variants/Magnetic.js

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