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