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 Monochrome() {
  13     return true;
  14   }
  15
  16   static get PawnSpecs() {
  17     return Object.assign(
  18       {},
  19       ChessRules.PawnSpecs,
  20       {
  21         twoSquares: false,
  22         promotions: [V.QUEEN]
  23       }
  24     );
  25   }
  26
  27   getPpath(b) {
  28     if (b[1] == 'b') return "Shatranj/" + b;
  29     return b;
  30   }
  31
  32   static get ElephantSteps() {
  33     return [
  34       [-2, -2],
  35       [-2, 2],
  36       [2, -2],
  37       [2, 2]
  38     ];
  39   }
  40
  41   static GenRandInitFen(randomness) {
  42     // Remove castle flags and en-passant indication
  43     return ChessRules.GenRandInitFen(randomness).slice(0, -7);
  44   }
  45
  46   getPotentialBishopMoves(sq) {
  47     let moves = this.getSlideNJumpMoves(sq, V.ElephantSteps, "oneStep");
  48     // Complete with "repositioning moves": like a queen, without capture
  49     let repositioningMoves = this.getSlideNJumpMoves(
  50       sq,
  51       V.steps[V.BISHOP],
  52       "oneStep"
  53     ).filter(m => m.vanish.length == 1);
  54     return moves.concat(repositioningMoves);
  55   }
  56
  57   getPotentialQueenMoves(sq) {
  58     // Diagonal capturing moves
  59     let captures = this.getSlideNJumpMoves(
  60       sq,
  61       V.steps[V.BISHOP],
  62       "oneStep"
  63     ).filter(m => m.vanish.length == 2);
  64     return captures.concat(
  65       // Orthogonal non-capturing moves
  66       this.getSlideNJumpMoves(
  67         sq,
  68         V.steps[V.ROOK],
  69         "oneStep"
  70       ).filter(m => m.vanish.length == 1)
  71     );
  72   }
  73
  74   isAttackedByBishop(sq, color) {
  75     return this.isAttackedBySlideNJump(
  76       sq,
  77       color,
  78       V.BISHOP,
  79       V.ElephantSteps,
  80       "oneStep"
  81     );
  82   }
  83
  84   isAttackedByQueen(sq, color) {
  85     return this.isAttackedBySlideNJump(
  86       sq,
  87       color,
  88       V.QUEEN,
  89       V.steps[V.BISHOP],
  90       "oneStep"
  91     );
  92   }
  93
  94   getCurrentScore() {
  95     const color = this.turn;
  96     const getScoreLost = () => {
  97       // Result if I lose:
  98       return color == "w" ? "0-1" : "1-0";
  99     };
 100     if (!this.atLeastOneMove())
 101       // No valid move: I lose (this includes checkmate)
 102       return getScoreLost();
 103     // Win if the opponent has no pieces left (except king),
 104     // and cannot bare king on the next move.
 105     let piecesLeft = {
 106       // No need to remember all pieces' squares:
 107       // variable only used if just one remaining piece.
 108       "w": {count: 0, square: null},
 109       "b": {count: 0, square: null}
 110     };
 111     outerLoop: for (let i=0; i<V.size.x; i++) {
 112       for (let j=0; j<V.size.y; j++) {
 113         if (this.board[i][j] != V.EMPTY && this.getPiece(i,j) != V.KING) {
 114           const sqCol = this.getColor(i,j);
 115           piecesLeft[sqCol].count++;
 116           piecesLeft[sqCol].square = [i,j];
 117         }
 118       }
 119     }
 120     if (Object.values(piecesLeft).every(v => v.count > 0))
 121       return "*";
 122     // No pieces left for some side: if both kings are bare, it's a draw
 123     if (Object.values(piecesLeft).every(v => v.count == 0))
 124       return "1/2";
 125     if (piecesLeft[color].count > 0)
 126       // He could have drawn, but didn't take my last piece...
 127       return color == "w" ? "1-0" : "0-1";
 128     const oppCol = V.GetOppCol(color);
 129     if (piecesLeft[oppCol].count >= 2)
 130       // 2 enemy units or more: I lose
 131       return getScoreLost();
 132     // I don't have any piece, my opponent have one: can I take it?
 133     if (this.isAttacked(piecesLeft[oppCol].square, color))
 134       // Yes! But I still need to take it
 135       return "*";
 136     // No :(
 137     return getScoreLost();
 138   }
 139
 140   static get VALUES() {
 141     return {
 142       p: 1,
 143       r: 5,
 144       n: 3,
 145       b: 3,
 146       q: 3,
 147       k: 1000
 148     };
 149   }
 150 };