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