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   underCheck() {
 140     return false; //there is no check
 141   }
 142
 143   getCheckSquares() {
 144     return [];
 145   }
 146
 147   updateVariables(move) {
 148     super.updateVariables(move);
 149     const c = move.vanish[0].c;
 150     if (move.vanish.length >= 2 && move.vanish[1].p == V.KING) {
 151       // We took opponent king !
 152       const oppCol = V.GetOppCol(c);
 153       this.kingPos[oppCol] = [-1, -1];
 154       this.castleFlags[oppCol] = [false, false];
 155     }
 156     // Did we magnetically move our (init) rooks or opponents' ones ?
 157     const firstRank = c == "w" ? 7 : 0;
 158     const oppFirstRank = 7 - firstRank;
 159     const oppCol = V.GetOppCol(c);
 160     move.vanish.forEach(psq => {
 161       if (psq.x == firstRank && this.INIT_COL_ROOK[c].includes(psq.y))
 162         this.castleFlags[c][psq.y == this.INIT_COL_ROOK[c][0] ? 0 : 1] = false;
 163       else if (
 164         psq.x == oppFirstRank &&
 165         this.INIT_COL_ROOK[oppCol].includes(psq.y)
 166       )
 167         this.castleFlags[oppCol][
 168           psq.y == this.INIT_COL_ROOK[oppCol][0] ? 0 : 1
 169         ] = false;
 170     });
 171   }
 172
 173   unupdateVariables(move) {
 174     super.unupdateVariables(move);
 175     const c = move.vanish[0].c;
 176     const oppCol = V.GetOppCol(c);
 177     if (this.kingPos[oppCol][0] < 0) {
 178       // Last move took opponent's king
 179       for (let psq of move.vanish) {
 180         if (psq.p == "k") {
 181           this.kingPos[oppCol] = [psq.x, psq.y];
 182           break;
 183         }
 184       }
 185     }
 186   }
 187
 188   getCurrentScore() {
 189     const color = this.turn;
 190     const kp = this.kingPos[color];
 191     if (kp[0] < 0)
 192       //king disappeared
 193       return color == "w" ? "0-1" : "1-0";
 194     if (this.atLeastOneMove())
 195       // game not over
 196       return "*";
 197     return "1/2"; //no moves but kings still there
 198   }
 199
 200   static get THRESHOLD_MATE() {
 201     return 500; //checkmates evals may be slightly below 1000
 202   }
 203 };