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 Notoodark() {
  17     return true;
  18   }
  19
  20   static get PawnSpecs() {
  21     return Object.assign(
  22       {},
  23       ChessRules.PawnSpecs,
  24       {
  25         twoSquares: false,
  26         promotions: [V.QUEEN]
  27       }
  28     );
  29   }
  30
  31   getPpath(b) {
  32     if (b[1] == 'b') return "Shatranj/" + b;
  33     return b;
  34   }
  35
  36   static get ElephantSteps() {
  37     return [
  38       [-2, -2],
  39       [-2, 2],
  40       [2, -2],
  41       [2, 2]
  42     ];
  43   }
  44
  45   static GenRandInitFen(randomness) {
  46     // Remove castle flags and en-passant indication
  47     return ChessRules.GenRandInitFen(randomness).slice(0, -7);
  48   }
  49
  50   getPotentialBishopMoves(sq) {
  51     let moves = this.getSlideNJumpMoves(sq, V.ElephantSteps, "oneStep");
  52     // Complete with "repositioning moves": like a queen, without capture
  53     let repositioningMoves = this.getSlideNJumpMoves(
  54       sq,
  55       V.steps[V.BISHOP],
  56       "oneStep"
  57     ).filter(m => m.vanish.length == 1);
  58     return moves.concat(repositioningMoves);
  59   }
  60
  61   getPotentialQueenMoves(sq) {
  62     // Diagonal capturing moves
  63     let captures = this.getSlideNJumpMoves(
  64       sq,
  65       V.steps[V.BISHOP],
  66       "oneStep"
  67     ).filter(m => m.vanish.length == 2);
  68     return captures.concat(
  69       // Orthogonal non-capturing moves
  70       this.getSlideNJumpMoves(
  71         sq,
  72         V.steps[V.ROOK],
  73         "oneStep"
  74       ).filter(m => m.vanish.length == 1)
  75     );
  76   }
  77
  78   isAttackedByBishop(sq, color) {
  79     return this.isAttackedBySlideNJump(
  80       sq,
  81       color,
  82       V.BISHOP,
  83       V.ElephantSteps,
  84       "oneStep"
  85     );
  86   }
  87
  88   isAttackedByQueen(sq, color) {
  89     return this.isAttackedBySlideNJump(
  90       sq,
  91       color,
  92       V.QUEEN,
  93       V.steps[V.BISHOP],
  94       "oneStep"
  95     );
  96   }
  97
  98   getCurrentScore() {
  99     const color = this.turn;
 100     const getScoreLost = () => {
 101       // Result if I lose:
 102       return color == "w" ? "0-1" : "1-0";
 103     };
 104     if (!this.atLeastOneMove())
 105       // No valid move: I lose (this includes checkmate)
 106       return getScoreLost();
 107     // Win if the opponent has no pieces left (except king),
 108     // and cannot bare king on the next move.
 109     let piecesLeft = {
 110       // No need to remember all pieces' squares:
 111       // variable only used if just one remaining piece.
 112       "w": {count: 0, square: null},
 113       "b": {count: 0, square: null}
 114     };
 115     outerLoop: for (let i=0; i<V.size.x; i++) {
 116       for (let j=0; j<V.size.y; j++) {
 117         if (this.board[i][j] != V.EMPTY && this.getPiece(i,j) != V.KING) {
 118           const sqCol = this.getColor(i,j);
 119           piecesLeft[sqCol].count++;
 120           piecesLeft[sqCol].square = [i,j];
 121         }
 122       }
 123     }
 124     if (Object.values(piecesLeft).every(v => v.count > 0))
 125       return "*";
 126     // No pieces left for some side: if both kings are bare, it's a draw
 127     if (Object.values(piecesLeft).every(v => v.count == 0))
 128       return "1/2";
 129     if (piecesLeft[color].count > 0)
 130       // He could have drawn, but didn't take my last piece...
 131       return color == "w" ? "1-0" : "0-1";
 132     const oppCol = V.GetOppCol(color);
 133     if (piecesLeft[oppCol].count >= 2)
 134       // 2 enemy units or more: I lose
 135       return getScoreLost();
 136     // I don't have any piece, my opponent have one: can I take it?
 137     if (this.isAttacked(piecesLeft[oppCol].square, color))
 138       // Yes! But I still need to take it
 139       return "*";
 140     // No :(
 141     return getScoreLost();
 142   }
 143
 144   static get VALUES() {
 145     return {
 146       p: 1,
 147       r: 5,
 148       n: 3,
 149       b: 3,
 150       q: 3,
 151       k: 1000
 152     };
 153   }
 154 };