client/src/variants/Knightrelay1.js

   1 import { ChessRules } from "@/base_rules";
   2
   3 export class Knightrelay1Rules extends ChessRules {
   4   static get HasEnpassant() {
   5     return false;
   6   }
   7
   8   // TODO: IsGoodPosition to check that 2 knights are on the board...
   9
  10   getPotentialMovesFrom([x, y]) {
  11     let moves = super.getPotentialMovesFrom([x, y]);
  12
  13     // Expand possible moves if guarded by a knight, and is not a king:
  14     const piece = this.getPiece(x,y);
  15     if (![V.KNIGHT,V.KING].includes(piece)) {
  16       const color = this.turn;
  17       let guardedByKnight = false;
  18       for (const step of V.steps[V.KNIGHT]) {
  19         if (
  20           V.OnBoard(x+step[0],y+step[1]) &&
  21           this.getPiece(x+step[0],y+step[1]) == V.KNIGHT &&
  22           this.getColor(x+step[0],y+step[1]) == color
  23         ) {
  24           guardedByKnight = true;
  25           break;
  26         }
  27       }
  28       if (guardedByKnight) {
  29         const lastRank = (color == "w" ? 0 : V.size.x - 1);
  30         for (const step of V.steps[V.KNIGHT]) {
  31           if (
  32             V.OnBoard(x+step[0],y+step[1]) &&
  33             this.getColor(x+step[0],y+step[1]) != color &&
  34             // Pawns cannot promote by knight-relay
  35             (piece != V.PAWN || x+step[0] != lastRank)
  36           ) {
  37             moves.push(this.getBasicMove([x,y], [x+step[0],y+step[1]]));
  38           }
  39         }
  40       }
  41     }
  42
  43     // Forbid captures of knights (invincible in this variant)
  44     return moves.filter(m => {
  45       return (
  46         m.vanish.length == 1 ||
  47         m.appear.length == 2 ||
  48         m.vanish[1].p != V.KNIGHT
  49       );
  50     });
  51   }
  52
  53   getPotentialKnightMoves(sq) {
  54     // Knights don't capture:
  55     return super.getPotentialKnightMoves(sq).filter(m => m.vanish.length == 1);
  56   }
  57
  58   isAttacked(sq, color) {
  59     if (super.isAttacked(sq, color)) return true;
  60
  61     // Check if a (non-knight) piece at knight distance
  62     // is guarded by a knight (and thus attacking)
  63     // --> Except for pawns targetting last rank.
  64     const x = sq[0],
  65           y = sq[1];
  66     // Last rank for me, that is to say oppCol of color:
  67     const lastRank = (color == 'w' ? V.size.x - 1 : 0);
  68     for (const step of V.steps[V.KNIGHT]) {
  69       if (
  70         V.OnBoard(x+step[0],y+step[1]) &&
  71         this.getColor(x+step[0],y+step[1]) == color
  72       ) {
  73         const piece = this.getPiece(x+step[0],y+step[1]);
  74         if (piece != V.KNIGHT && (piece != V.PAWN || x != lastRank)) {
  75           for (const step2 of V.steps[V.KNIGHT]) {
  76             const xx = x+step[0]+step2[0],
  77                   yy = y+step[1]+step2[1];
  78             if (
  79               V.OnBoard(xx,yy) &&
  80               this.getColor(xx,yy) == color &&
  81               this.getPiece(xx,yy) == V.KNIGHT
  82             ) {
  83               return true;
  84             }
  85           }
  86         }
  87       }
  88     }
  89
  90     return false;
  91   }
  92
  93   isAttackedByKnight(sq, color) {
  94     // Knights don't attack
  95     return false;
  96   }
  97
  98   static get VALUES() {
  99     return {
 100       p: 1,
 101       r: 5,
 102       n: 0, //the knight isn't captured - value doesn't matter
 103       b: 3,
 104       q: 9,
 105       k: 1000
 106     };
 107   }
 108
 109   static get SEARCH_DEPTH() {
 110     return 2;
 111   }
 112
 113   getNotation(move) {
 114     if (move.appear.length == 2 && move.appear[0].p == V.KING)
 115       // Castle
 116       return move.end.y < move.start.y ? "0-0-0" : "0-0";
 117
 118     // Translate final and initial square
 119     const initSquare = V.CoordsToSquare(move.start);
 120     const finalSquare = V.CoordsToSquare(move.end);
 121     const piece = this.getPiece(move.start.x, move.start.y);
 122
 123     // Since pieces and pawns could move like knight, indicate start and end squares
 124     let notation =
 125       piece.toUpperCase() +
 126       initSquare +
 127       (move.vanish.length > move.appear.length ? "x" : "") +
 128       finalSquare
 129
 130     if (
 131       piece == V.PAWN &&
 132       move.appear.length > 0 &&
 133       move.appear[0].p != V.PAWN
 134     ) {
 135       // Promotion
 136       notation += "=" + move.appear[0].p.toUpperCase();
 137     }
 138
 139     return notation;
 140   }
 141 };