client/src/variants/Arena.js

   1 import { ChessRules } from "@/base_rules";
   2
   3 export const VariantRules = class ArenaRules extends ChessRules {
   4   static get hasFlags() {
   5     return false;
   6   }
   7
   8   static GenRandInitFen(randomness) {
   9     return ChessRules
  10       .GenRandInitFen(randomness)
  11       .replace("w 0 1111 -", "w 0 -");
  12   }
  13
  14   static InArena(x) {
  15     return Math.abs(3.5 - x) <= 1.5;
  16   }
  17
  18   getPotentialMovesFrom([x, y]) {
  19     const moves = super.getPotentialMovesFrom([x, y]);
  20     // Eliminate moves which neither enter the arena or capture something
  21     return moves.filter(m => {
  22       const startInArena = V.InArena(m.start.x);
  23       const endInArena = V.InArena(m.end.x);
  24       return (
  25         (startInArena && endInArena && m.vanish.length == 2) ||
  26         (!startInArena && endInArena)
  27       );
  28     });
  29
  30     return moves;
  31   }
  32
  33   getPotentialPawnMoves([x, y]) {
  34     const color = this.turn;
  35     let moves = [];
  36     const [sizeX, sizeY] = [V.size.x, V.size.y];
  37     const shiftX = color == "w" ? -1 : 1;
  38     const startRank = color == "w" ? sizeX - 2 : 1;
  39
  40     if (this.board[x + shiftX][y] == V.EMPTY) {
  41       // One square forward
  42       moves.push(this.getBasicMove([x, y], [x + shiftX, y]));
  43       // Next condition because pawns on 1st rank can generally jump
  44       if (
  45         x == startRank &&
  46         this.board[x + 2 * shiftX][y] == V.EMPTY
  47       ) {
  48         // Two squares jump
  49         moves.push(this.getBasicMove([x, y], [x + 2 * shiftX, y]));
  50       }
  51     }
  52     // Captures: also possible backward
  53     for (let shiftY of [-1, 1]) {
  54       if (y + shiftY >= 0 && y + shiftY < sizeY) {
  55         for (let direction of [-1,1]) {
  56           if (
  57             this.board[x + direction][y + shiftY] != V.EMPTY &&
  58             this.canTake([x, y], [x + direction, y + shiftY])
  59           ) {
  60             moves.push(this.getBasicMove([x, y], [x + direction, y + shiftY]));
  61           }
  62         }
  63       }
  64     }
  65
  66     // En passant
  67     const Lep = this.epSquares.length;
  68     const epSquare = this.epSquares[Lep - 1]; //always at least one element
  69     if (
  70       !!epSquare &&
  71       epSquare.x == x + shiftX &&
  72       Math.abs(epSquare.y - y) == 1
  73     ) {
  74       let enpassantMove = this.getBasicMove([x, y], [epSquare.x, epSquare.y]);
  75       enpassantMove.vanish.push({
  76         x: x,
  77         y: epSquare.y,
  78         p: "p",
  79         c: this.getColor(x, epSquare.y)
  80       });
  81       moves.push(enpassantMove);
  82     }
  83
  84     return moves;
  85   }
  86
  87   getPotentialQueenMoves(sq) {
  88     return this.getSlideNJumpMoves(
  89       sq,
  90       V.steps[V.ROOK].concat(V.steps[V.BISHOP])
  91     ).filter(m => {
  92       // Filter out moves longer than 3 squares
  93       return Math.max(
  94         Math.abs(m.end.x - m.start.x),
  95         Math.abs(m.end.y - m.start.y)) <= 3;
  96     });
  97   }
  98
  99   getPotentialKingMoves(sq) {
 100     return this.getSlideNJumpMoves(
 101       sq,
 102       V.steps[V.ROOK].concat(V.steps[V.BISHOP])
 103     ).filter(m => {
 104       // Filter out moves longer than 3 squares
 105       return Math.max(
 106         Math.abs(m.end.x - m.start.x),
 107         Math.abs(m.end.y - m.start.y)) <= 3;
 108     });
 109   }
 110
 111   getCheckSquares() {
 112     return [];
 113   }
 114
 115   filterValid(moves) {
 116     // No check conditions
 117     return moves;
 118   }
 119
 120   getCurrentScore() {
 121     const color = this.turn;
 122     if (!this.atLeastOneMove())
 123       // I cannot move anymore
 124       return color == "w" ? "0-1" : "1-0";
 125     // Win if the opponent has no more pieces left (in the Arena),
 126     // (and/)or if he lost both his dukes.
 127     let someUnitRemain = false;
 128     let atLeastOneDuke = false;
 129     let somethingInArena = false;
 130     outerLoop: for (let i=0; i<V.size.x; i++) {
 131       for (let j=0; j<V.size.y; j++) {
 132         if (this.getColor(i,j) == color) {
 133           someUnitRemain = true;
 134           if (this.movesCount >= 2 && V.InArena(i)) {
 135             somethingInArena = true;
 136             if (atLeastOneDuke)
 137               break outerLoop;
 138           }
 139           if ([V.QUEEN,V.KING].includes(this.getPiece(i,j))) {
 140             atLeastOneDuke = true;
 141             if (this.movesCount < 2 || somethingInArena)
 142               break outerLoop;
 143           }
 144         }
 145       }
 146     }
 147     if (
 148       !someUnitRemain ||
 149       !atLeastOneDuke ||
 150       (this.movesCount >= 2 && !somethingInArena)
 151     ) {
 152       return color == "w" ? "0-1" : "1-0";
 153     }
 154     return "*";
 155   }
 156 };