client/src/variants/Shatranj.js

   1 // TODO: bishop OK, but queen should move vertical/horizontal and capture diagonally.
   2 // ==> then the pawn promotion is a real promotion (enhancement).
   3
   4 import { ChessRules } from "@/base_rules";
   5
   6 export const VariantRules = class ShatranjRules extends ChessRules {
   7   static get HasFlags() {
   8     return false;
   9   }
  10
  11   static get HasEnpassant() {
  12     return false;
  13   }
  14
  15   static get ElephantSteps() {
  16     return [
  17       [-2, -2],
  18       [-2, 2],
  19       [2, -2],
  20       [2, 2]
  21     ];
  22   }
  23
  24   static GenRandInitFen() {
  25     return ChessRules.GenRandInitFen().replace("w 1111 -", "w");
  26   }
  27
  28   getPotentialPawnMoves([x, y]) {
  29     const color = this.turn;
  30     let moves = [];
  31     const [sizeX, sizeY] = [V.size.x, V.size.y];
  32     const shiftX = color == "w" ? -1 : 1;
  33     const startRank = color == "w" ? sizeX - 2 : 1;
  34     const lastRank = color == "w" ? 0 : sizeX - 1;
  35     // Promotion in minister (queen) only:
  36     const finalPiece = x + shiftX == lastRank ? V.QUEEN : V.PAWN;
  37
  38     if (this.board[x + shiftX][y] == V.EMPTY) {
  39       // One square forward
  40       moves.push(
  41         this.getBasicMove([x, y], [x + shiftX, y], {
  42           c: color,
  43           p: finalPiece
  44         })
  45       );
  46     }
  47     // Captures
  48     for (let shiftY of [-1, 1]) {
  49       if (
  50         y + shiftY >= 0 &&
  51         y + shiftY < sizeY &&
  52         this.board[x + shiftX][y + shiftY] != V.EMPTY &&
  53         this.canTake([x, y], [x + shiftX, y + shiftY])
  54       ) {
  55         moves.push(
  56           this.getBasicMove([x, y], [x + shiftX, y + shiftY], {
  57             c: color,
  58             p: finalPiece
  59           })
  60         );
  61       }
  62     }
  63
  64     return moves;
  65   }
  66
  67   getPotentialBishopMoves(sq) {
  68     let moves = this.getSlideNJumpMoves(sq, V.ElephantSteps, "oneStep");
  69     // Complete with "repositioning moves": like a queen, without capture
  70     let repositioningMoves = this.getSlideNJumpMoves(
  71       sq,
  72       V.steps[V.BISHOP],
  73       "oneStep"
  74     ).filter(m => m.vanish.length == 1);
  75     return moves.concat(repositioningMoves);
  76   }
  77
  78   getPotentialQueenMoves(sq) {
  79     return this.getSlideNJumpMoves(
  80       sq,
  81       V.steps[V.BISHOP],
  82       "oneStep"
  83     );
  84   }
  85
  86   getPotentialKingMoves(sq) {
  87     return this.getSlideNJumpMoves(
  88       sq,
  89       V.steps[V.ROOK].concat(V.steps[V.BISHOP]),
  90       "oneStep"
  91     );
  92   }
  93
  94   isAttackedByBishop(sq, colors) {
  95     return this.isAttackedBySlideNJump(
  96       sq,
  97       colors,
  98       V.BISHOP,
  99       V.ElephantSteps,
 100       "oneStep"
 101     );
 102   }
 103
 104   isAttackedByQueen(sq, colors) {
 105     return this.isAttackedBySlideNJump(
 106       sq,
 107       colors,
 108       V.QUEEN,
 109       V.steps[V.BISHOP],
 110       "oneStep"
 111     );
 112   }
 113
 114   static get VALUES() {
 115     return {
 116       p: 1,
 117       r: 5,
 118       n: 3,
 119       b: 2.5,
 120       q: 2,
 121       k: 1000
 122     };
 123   }
 124 };