client/src/variants/Berolina.js

   1 import { ChessRules } from "@/base_rules";
   2
   3 export class BerolinaRules extends ChessRules {
   4
   5   // En-passant after 2-sq jump
   6   getEpSquare(moveOrSquare) {
   7     if (!moveOrSquare) return undefined;
   8     if (typeof moveOrSquare === "string") {
   9       const square = moveOrSquare;
  10       if (square == "-") return undefined;
  11       // Enemy pawn initial column must be given too:
  12       let res = [];
  13       const epParts = square.split(",");
  14       res.push(V.SquareToCoords(epParts[0]));
  15       res.push(V.ColumnToCoord(epParts[1]));
  16       return res;
  17     }
  18     // Argument is a move:
  19     const move = moveOrSquare;
  20     const [sx, ex, sy] = [move.start.x, move.end.x, move.start.y];
  21     if (this.getPiece(sx, sy) == V.PAWN && Math.abs(sx - ex) == 2) {
  22       return [
  23         {
  24           x: (ex + sx) / 2,
  25           y: (move.end.y + sy) / 2
  26         },
  27         // The arrival column must be remembered, because
  28         // potentially two pawns could be candidates to be captured:
  29         // one on our left, and one on our right.
  30         move.end.y
  31       ];
  32     }
  33     return undefined; //default
  34   }
  35
  36   static IsGoodEnpassant(enpassant) {
  37     if (enpassant != "-") {
  38       const epParts = enpassant.split(",");
  39       const epSq = V.SquareToCoords(epParts[0]);
  40       if (isNaN(epSq.x) || isNaN(epSq.y) || !V.OnBoard(epSq)) return false;
  41       const arrCol = V.ColumnToCoord(epParts[1]);
  42       if (isNaN(arrCol) || arrCol < 0 || arrCol >= V.size.y) return false;
  43     }
  44     return true;
  45   }
  46
  47   getEnpassantFen() {
  48     const L = this.epSquares.length;
  49     if (!this.epSquares[L - 1]) return "-"; //no en-passant
  50     return (
  51       V.CoordsToSquare(this.epSquares[L - 1][0]) +
  52       "," +
  53       V.CoordToColumn(this.epSquares[L - 1][1])
  54     );
  55   }
  56
  57   // Special pawns movements
  58   getPotentialPawnMoves([x, y]) {
  59     const color = this.turn;
  60     let moves = [];
  61     const [sizeX, sizeY] = [V.size.x, V.size.y];
  62     const shiftX = color == "w" ? -1 : 1;
  63     const startRank = color == "w" ? sizeX - 2 : 1;
  64     const lastRank = color == "w" ? 0 : sizeX - 1;
  65     const finalPieces =
  66       x + shiftX == lastRank
  67         ? [V.ROOK, V.KNIGHT, V.BISHOP, V.QUEEN]
  68         : [V.PAWN];
  69
  70     // One square diagonally
  71     for (let shiftY of [-1, 1]) {
  72       if (this.board[x + shiftX][y + shiftY] == V.EMPTY) {
  73         for (let piece of finalPieces) {
  74           moves.push(
  75             this.getBasicMove([x, y], [x + shiftX, y + shiftY], {
  76               c: color,
  77               p: piece
  78             })
  79           );
  80         }
  81         if (
  82           V.PawnSpecs.twoSquares &&
  83           x == startRank &&
  84           y + 2 * shiftY >= 0 &&
  85           y + 2 * shiftY < sizeY &&
  86           this.board[x + 2 * shiftX][y + 2 * shiftY] == V.EMPTY
  87         ) {
  88           // Two squares jump
  89           moves.push(
  90             this.getBasicMove([x, y], [x + 2 * shiftX, y + 2 * shiftY])
  91           );
  92         }
  93       }
  94     }
  95     // Capture
  96     if (
  97       this.board[x + shiftX][y] != V.EMPTY &&
  98       this.canTake([x, y], [x + shiftX, y])
  99     ) {
 100       for (let piece of finalPieces) {
 101         moves.push(
 102           this.getBasicMove([x, y], [x + shiftX, y], { c: color, p: piece })
 103         );
 104       }
 105     }
 106
 107     // Next condition so that other variants could inherit from this class
 108     if (V.PawnSpecs.enPassant) {
 109       // En passant
 110       const Lep = this.epSquares.length;
 111       const epSquare = this.epSquares[Lep - 1]; //always at least one element
 112       if (
 113         !!epSquare &&
 114         epSquare[0].x == x + shiftX &&
 115         epSquare[0].y == y
 116       ) {
 117         let enpassantMove = this.getBasicMove([x, y], [x + shiftX, y]);
 118         enpassantMove.vanish.push({
 119           x: x,
 120           y: epSquare[1],
 121           p: "p",
 122           c: this.getColor(x, epSquare[1])
 123         });
 124         moves.push(enpassantMove);
 125       }
 126     }
 127
 128     return moves;
 129   }
 130
 131   isAttackedByPawn([x, y], color) {
 132     let pawnShift = (color == "w" ? 1 : -1);
 133     return (
 134       x + pawnShift >= 0 && x + pawnShift < V.size.x &&
 135       this.getPiece(x + pawnShift, y) == V.PAWN &&
 136       this.getColor(x + pawnShift, y) == color
 137     );
 138   }
 139
 140   static get SEARCH_DEPTH() {
 141     return 2;
 142   }
 143
 144   getNotation(move) {
 145     const piece = this.getPiece(move.start.x, move.start.y);
 146     if (piece == V.PAWN) {
 147       // Pawn move
 148       const finalSquare = V.CoordsToSquare(move.end);
 149       let notation = "";
 150       if (move.vanish.length == 2)
 151         // Capture
 152         notation = "Px" + finalSquare;
 153       else {
 154         // No capture: indicate the initial square for potential ambiguity
 155         const startSquare = V.CoordsToSquare(move.start);
 156         notation = startSquare + finalSquare;
 157       }
 158       if (move.appear[0].p != V.PAWN)
 159         // Promotion
 160         notation += "=" + move.appear[0].p.toUpperCase();
 161       return notation;
 162     }
 163     return super.getNotation(move); //all other pieces are orthodox
 164   }
 165
 166 };