client/src/variants/Grasshopper.js

   1 import { ChessRules } from "@/base_rules";
   2 import { ArrayFun } from "@/utils/array";
   3 import { randInt } from "@/utils/alea";
   4
   5 export class GrasshopperRules extends ChessRules {
   6   static get HasEnpassant() {
   7     return false;
   8   }
   9
  10   static get PawnSpecs() {
  11     return Object.assign(
  12       {},
  13       ChessRules.PawnSpecs,
  14       { promotions: ChessRules.PawnSpecs.promotions.concat([V.GRASSHOPPER]) }
  15     );
  16   }
  17
  18   static get GRASSHOPPER() {
  19     return "g";
  20   }
  21
  22   static get PIECES() {
  23     return ChessRules.PIECES.concat([V.GRASSHOPPER]);
  24   }
  25
  26   getPpath(b) {
  27     return (b[1] == V.GRASSHOPPER ? "Grasshopper/" : "") + b;
  28   }
  29
  30   getPotentialMovesFrom([x, y]) {
  31     switch (this.getPiece(x, y)) {
  32       case V.GRASSHOPPER:
  33         return this.getPotentialGrasshopperMoves([x, y]);
  34       default:
  35         return super.getPotentialMovesFrom([x, y]);
  36     }
  37   }
  38
  39   getPotentialGrasshopperMoves([x, y]) {
  40     let moves = [];
  41     // Look in every direction until an obstacle (to jump) is met
  42     for (const step of V.steps[V.ROOK].concat(V.steps[V.BISHOP])) {
  43       let i = x + step[0];
  44       let j = y + step[1];
  45       while (V.OnBoard(i, j) && this.board[i][j] == V.EMPTY) {
  46         i += step[0];
  47         j += step[1];
  48       }
  49       // Move is valid if the next square is empty or occupied by enemy
  50       const nextSq = [i+step[0], j+step[1]];
  51       if (V.OnBoard(nextSq[0], nextSq[1]) && this.canTake([x, y], nextSq))
  52         moves.push(this.getBasicMove([x, y], nextSq));
  53     }
  54     return moves;
  55   }
  56
  57   isAttacked(sq, color) {
  58     return (
  59       super.isAttacked(sq, color) ||
  60       this.isAttackedByGrasshopper(sq, color)
  61     );
  62   }
  63
  64   isAttackedByGrasshopper([x, y], color) {
  65     // Reversed process: is there an adjacent obstacle,
  66     // and a grasshopper next in the same line?
  67     for (const step of V.steps[V.ROOK].concat(V.steps[V.BISHOP])) {
  68       const nextSq = [x+step[0], y+step[1]];
  69       if (
  70         V.OnBoard(nextSq[0], nextSq[1]) &&
  71         this.board[nextSq[0]][nextSq[1]] != V.EMPTY
  72       ) {
  73         let i = nextSq[0] + step[0];
  74         let j = nextSq[1] + step[1];
  75         while (V.OnBoard(i, j) && this.board[i][j] == V.EMPTY) {
  76           i += step[0];
  77           j += step[1];
  78         }
  79         if (
  80           V.OnBoard(i, j) &&
  81           this.getPiece(i, j) == V.GRASSHOPPER &&
  82           this.getColor(i, j) == color
  83         ) {
  84           return true;
  85         }
  86       }
  87     }
  88     return false;
  89   }
  90
  91   static get VALUES() {
  92     return Object.assign(
  93       // TODO: grasshoppers power decline with less pieces on board...
  94       { g: 2 },
  95       ChessRules.VALUES
  96     );
  97   }
  98
  99   static get SEARCH_DEPTH() {
 100     return 2;
 101   }
 102
 103   static GenRandInitFen(randomness) {
 104     return ChessRules.GenRandInitFen(randomness)
 105       .slice(0, -2)
 106       .replace(
 107         "/pppppppp/8/8/8/8/PPPPPPPP/",
 108         "/gggggggg/pppppppp/8/8/PPPPPPPP/GGGGGGGG/"
 109       );
 110   }
 111 };