client/src/variants/Shatranj.js

   1 import { ChessRules } from "@/base_rules";
   2
   3 export class ShatranjRules extends ChessRules {
   4   static get HasFlags() {
   5     return false;
   6   }
   7
   8   static get HasEnpassant() {
   9     return false;
  10   }
  11
  12   static get PawnSpecs() {
  13     return Object.assign(
  14       {},
  15       ChessRules.PawnSpecs,
  16       {
  17         twoSquares: false,
  18         promotions: [V.QUEEN]
  19       }
  20     );
  21   }
  22
  23   static get ElephantSteps() {
  24     return [
  25       [-2, -2],
  26       [-2, 2],
  27       [2, -2],
  28       [2, 2]
  29     ];
  30   }
  31
  32   static GenRandInitFen(randomness) {
  33     // Remove castle flags and en-passant indication
  34     return ChessRules.GenRandInitFen(randomness).slice(0, -7);
  35   }
  36
  37   getPotentialBishopMoves(sq) {
  38     let moves = this.getSlideNJumpMoves(sq, V.ElephantSteps, "oneStep");
  39     // Complete with "repositioning moves": like a queen, without capture
  40     let repositioningMoves = this.getSlideNJumpMoves(
  41       sq,
  42       V.steps[V.BISHOP],
  43       "oneStep"
  44     ).filter(m => m.vanish.length == 1);
  45     return moves.concat(repositioningMoves);
  46   }
  47
  48   getPotentialQueenMoves(sq) {
  49     // Diagonal capturing moves
  50     let captures = this.getSlideNJumpMoves(
  51       sq,
  52       V.steps[V.BISHOP],
  53       "oneStep"
  54     ).filter(m => m.vanish.length == 2);
  55     return captures.concat(
  56       // Orthogonal non-capturing moves
  57       this.getSlideNJumpMoves(
  58         sq,
  59         V.steps[V.ROOK],
  60         "oneStep"
  61       ).filter(m => m.vanish.length == 1)
  62     );
  63   }
  64
  65   isAttackedByBishop(sq, color) {
  66     return this.isAttackedBySlideNJump(
  67       sq,
  68       color,
  69       V.BISHOP,
  70       V.ElephantSteps,
  71       "oneStep"
  72     );
  73   }
  74
  75   isAttackedByQueen(sq, color) {
  76     return this.isAttackedBySlideNJump(
  77       sq,
  78       color,
  79       V.QUEEN,
  80       V.steps[V.BISHOP],
  81       "oneStep"
  82     );
  83   }
  84
  85   getCurrentScore() {
  86     const color = this.turn;
  87     const getScoreLost = () => {
  88       // Result if I lose:
  89       return color == "w" ? "0-1" : "1-0";
  90     };
  91     if (!this.atLeastOneMove())
  92       // No valid move: I lose (this includes checkmate)
  93       return getScoreLost();
  94     // Win if the opponent has no pieces left (except king),
  95     // and cannot bare king on the next move.
  96     let piecesLeft = {
  97       // No need to remember all pieces' squares:
  98       // variable only used if just one remaining piece.
  99       "w": {count: 0, square: null},
 100       "b": {count: 0, square: null}
 101     };
 102     outerLoop: for (let i=0; i<V.size.x; i++) {
 103       for (let j=0; j<V.size.y; j++) {
 104         if (this.board[i][j] != V.EMPTY && this.getPiece(i,j) != V.KING) {
 105           const sqCol = this.getColor(i,j);
 106           piecesLeft[sqCol].count++;
 107           piecesLeft[sqCol].square = [i,j];
 108         }
 109       }
 110     }
 111     if (Object.values(piecesLeft).every(v => v.count > 0))
 112       return "*";
 113     // No pieces left for some side: if both kings are bare, it's a draw
 114     if (Object.values(piecesLeft).every(v => v.count == 0))
 115       return "1/2";
 116     if (piecesLeft[color].count > 0)
 117       // He could have drawn, but didn't take my last piece...
 118       return color == "w" ? "1-0" : "0-1";
 119     const oppCol = V.GetOppCol(color);
 120     if (piecesLeft[oppCol].count >= 2)
 121       // 2 enemy units or more: I lose
 122       return getScoreLost();
 123     // I don't have any piece, my opponent have one: can I take it?
 124     if (this.isAttacked(piecesLeft[oppCol].square, color))
 125       // Yes! But I still need to take it
 126       return "*";
 127     // No :(
 128     return getScoreLost();
 129   }
 130
 131   static get VALUES() {
 132     return {
 133       p: 1,
 134       r: 5,
 135       n: 3,
 136       b: 3,
 137       q: 3,
 138       k: 1000
 139     };
 140   }
 141 };