client/src/variants/Shatranj.js

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