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