client/src/variants/Knightrelay.js

   1 import { ChessRules } from "@/base_rules";
   2
   3 export const VariantRules = class KnightrelayRules extends ChessRules {
   4   getPotentialMovesFrom([x, y]) {
   5     let moves = super.getPotentialMovesFrom([x, y]);
   6
   7     // Expand possible moves if guarded by a knight:
   8     const piece = this.getPiece(x,y);
   9     if (piece != V.KNIGHT) {
  10       const color = this.turn;
  11       let guardedByKnight = false;
  12       for (const step of V.steps[V.KNIGHT]) {
  13         if (
  14           V.OnBoard(x+step[0],y+step[1]) &&
  15           this.getPiece(x+step[0],y+step[1]) == V.KNIGHT &&
  16           this.getColor(x+step[0],y+step[1]) == color
  17         ) {
  18           guardedByKnight = true;
  19           break;
  20         }
  21       }
  22       if (guardedByKnight) {
  23         const lastRank = color == "w" ? 0 : V.size.x - 1;
  24         for (const step of V.steps[V.KNIGHT]) {
  25           if (
  26             V.OnBoard(x+step[0],y+step[1]) &&
  27             this.getColor(x+step[0],y+step[1]) != color
  28           ) {
  29             // Potential promotions:
  30             const finalPieces = piece == V.PAWN && x + step[0] == lastRank
  31               ? [V.ROOK, V.KNIGHT, V.BISHOP, V.QUEEN]
  32               : [piece];
  33             for (let p of finalPieces) {
  34               moves.push(
  35                 this.getBasicMove([x,y], [x+step[0],y+step[1]], {
  36                   c: color,
  37                   p: p
  38                 })
  39               );
  40             }
  41           }
  42         }
  43       }
  44     }
  45
  46     return moves;
  47   }
  48
  49   isAttacked(sq, colors) {
  50     if (super.isAttacked(sq, colors))
  51       return true;
  52
  53     // Check if a (non-knight) piece at knight distance
  54     // is guarded by a knight (and thus attacking)
  55     const x = sq[0],
  56           y = sq[1];
  57     for (const step of V.steps[V.KNIGHT]) {
  58       if (
  59         V.OnBoard(x+step[0],y+step[1]) &&
  60         colors.includes(this.getColor(x+step[0],y+step[1])) &&
  61         this.getPiece(x+step[0],y+step[1]) != V.KNIGHT
  62       ) {
  63         for (const step2 of V.steps[V.KNIGHT]) {
  64           const xx = x+step[0]+step2[0],
  65                 yy = y+step[1]+step2[1];
  66           if (
  67             V.OnBoard(xx,yy) &&
  68             colors.includes(this.getColor(xx,yy)) &&
  69             this.getPiece(xx,yy) == V.KNIGHT
  70           ) {
  71             return true;
  72           }
  73         }
  74       }
  75     }
  76
  77     return false;
  78   }
  79
  80   static get VALUES() {
  81     return {
  82       p: 1,
  83       r: 5,
  84       n: 7, //the knight is valuable
  85       b: 3,
  86       q: 9,
  87       k: 1000
  88     };
  89   }
  90
  91   static get SEARCH_DEPTH() {
  92     return 2;
  93   }
  94
  95   getNotation(move) {
  96     if (move.appear.length == 2 && move.appear[0].p == V.KING)
  97       // Castle
  98       return move.end.y < move.start.y ? "0-0-0" : "0-0";
  99
 100     // Translate final and initial square
 101     const initSquare = V.CoordsToSquare(move.start);
 102     const finalSquare = V.CoordsToSquare(move.end);
 103     const piece = this.getPiece(move.start.x, move.start.y);
 104
 105     // Since pieces and pawns could move like knight, indicate start and end squares
 106     let notation =
 107       piece.toUpperCase() +
 108       initSquare +
 109       (move.vanish.length > move.appear.length ? "x" : "") +
 110       finalSquare
 111
 112     if (
 113       piece == V.PAWN &&
 114       move.appear.length > 0 &&
 115       move.appear[0].p != V.PAWN
 116     ) {
 117       // Promotion
 118       notation += "=" + move.appear[0].p.toUpperCase();
 119     }
 120
 121     return notation;
 122   }
 123 };