client/src/variants/Cannibal.js

   1 import { ChessRules, Move, PiPo } from "@/base_rules";
   2
   3 export class CannibalRules extends ChessRules {
   4   static get KING_CODE() {
   5     return {
   6       'p': 's',
   7       'r': 'u',
   8       'n': 'o',
   9       'b': 'c',
  10       'q': 't'
  11     };
  12   }
  13
  14   static get KING_DECODE() {
  15     return {
  16       's': 'p',
  17       'u': 'r',
  18       'o': 'n',
  19       'c': 'b',
  20       't': 'q'
  21     };
  22   }
  23
  24   // Kings may be disguised:
  25   getPiece(x, y) {
  26     const piece = this.board[x][y].charAt(1);
  27     if (Object.keys(V.KING_DECODE).includes(piece))
  28       return V.KING_DECODE[piece];
  29     return piece;
  30   }
  31
  32   getPpath(b) {
  33     return (Object.keys(V.KING_DECODE).includes(b[1]) ? "Cannibal/" : "") + b;
  34   }
  35
  36   // Kings may be disguised:
  37   setOtherVariables(fen) {
  38     super.setOtherVariables(fen);
  39     const rows = V.ParseFen(fen).position.split("/");
  40     if (this.kingPos["w"][0] < 0 || this.kingPos["b"][0] < 0) {
  41       for (let i = 0; i < rows.length; i++) {
  42         let k = 0; //column index on board
  43         for (let j = 0; j < rows[i].length; j++) {
  44           const piece = rows[i].charAt(j);
  45           if (Object.keys(V.KING_DECODE).includes(piece.toLowerCase())) {
  46             const color = (piece.charCodeAt(0) <= 90 ? 'w' : 'b');
  47             this.kingPos[color] = [i, k];
  48           } else {
  49             const num = parseInt(rows[i].charAt(j));
  50             if (!isNaN(num)) k += num - 1;
  51           }
  52           k++;
  53         }
  54       }
  55     }
  56   }
  57
  58   // Trim all non-capturing moves
  59   static KeepCaptures(moves) {
  60     return moves.filter(m => m.vanish.length == 2 && m.appear.length == 1);
  61   }
  62
  63     // Stop at the first capture found (if any)
  64   atLeastOneCapture() {
  65     const color = this.turn;
  66     const oppCol = V.GetOppCol(color);
  67     for (let i = 0; i < V.size.x; i++) {
  68       for (let j = 0; j < V.size.y; j++) {
  69         if (
  70           this.board[i][j] != V.EMPTY &&
  71           this.getColor(i, j) != oppCol &&
  72           this.filterValid(this.getPotentialMovesFrom([i, j])).some(m =>
  73             // Warning: discard castle moves
  74             m.vanish.length == 2 && m.appear.length == 1)
  75         ) {
  76           return true;
  77         }
  78       }
  79     }
  80     return false;
  81   }
  82
  83   // Because of the disguised kings, getPiece() could be wrong:
  84   // use board[x][y][1] instead (always valid).
  85   getBasicMove([sx, sy], [ex, ey], tr) {
  86     const initColor = this.getColor(sx, sy);
  87     const initPiece = this.board[sx][sy].charAt(1);
  88     let mv = new Move({
  89       appear: [
  90         new PiPo({
  91           x: ex,
  92           y: ey,
  93           c: tr ? tr.c : initColor,
  94           p: tr ? tr.p : initPiece
  95         })
  96       ],
  97       vanish: [
  98         new PiPo({
  99           x: sx,
 100           y: sy,
 101           c: initColor,
 102           p: initPiece
 103         })
 104       ]
 105     });
 106
 107     // The opponent piece disappears if we take it
 108     if (this.board[ex][ey] != V.EMPTY) {
 109       mv.vanish.push(
 110         new PiPo({
 111           x: ex,
 112           y: ey,
 113           c: this.getColor(ex, ey),
 114           p: this.board[ex][ey].charAt(1)
 115         })
 116       );
 117
 118       // If the captured piece has a different nature: take it as well
 119       if (mv.vanish[0].p != mv.vanish[1].p) {
 120         if (
 121           mv.vanish[0].p == V.KING ||
 122           Object.keys(V.KING_DECODE).includes(mv.vanish[0].p)
 123         ) {
 124           mv.appear[0].p = V.KING_CODE[mv.vanish[1].p];
 125         } else mv.appear[0].p = mv.vanish[1].p;
 126       }
 127     }
 128     else if (!!tr && mv.vanish[0].p != V.PAWN)
 129       // Special case of a non-capturing king-as-pawn promotion
 130       mv.appear[0].p = V.KING_CODE[tr.p];
 131
 132     return mv;
 133   }
 134
 135   getPotentialMovesFrom([x, y]) {
 136     const piece = this.board[x][y].charAt(1);
 137     if (Object.keys(V.KING_DECODE).includes(piece))
 138       return super.getPotentialMovesFrom([x, y], V.KING_DECODE[piece]);
 139     return super.getPotentialMovesFrom([x, y], piece);
 140   }
 141
 142   addPawnMoves([x1, y1], [x2, y2], moves) {
 143     let finalPieces = [V.PAWN];
 144     const color = this.turn;
 145     const lastRank = (color == "w" ? 0 : V.size.x - 1);
 146     if (x2 == lastRank) {
 147       if (this.board[x2][y2] != V.EMPTY)
 148         // Cannibal rules: no choice if capture
 149         finalPieces = [this.getPiece(x2, y2)];
 150       else finalPieces = V.PawnSpecs.promotions;
 151     }
 152     let tr = null;
 153     for (let piece of finalPieces) {
 154       tr = (piece != V.PAWN ? { c: color, p: piece } : null);
 155       moves.push(this.getBasicMove([x1, y1], [x2, y2], tr));
 156     }
 157   }
 158
 159   getPossibleMovesFrom(sq) {
 160     let moves = this.filterValid(this.getPotentialMovesFrom(sq));
 161     const captureMoves = V.KeepCaptures(moves);
 162     if (captureMoves.length > 0) return captureMoves;
 163     if (this.atLeastOneCapture()) return [];
 164     return moves;
 165   }
 166
 167   getAllValidMoves() {
 168     const moves = super.getAllValidMoves();
 169     if (moves.some(m => m.vanish.length == 2)) return V.KeepCaptures(moves);
 170     return moves;
 171   }
 172
 173   postPlay(move) {
 174     const c = V.GetOppCol(this.turn);
 175     const piece = move.appear[0].p;
 176     // Update king position + flags
 177     if (piece == V.KING || Object.keys(V.KING_DECODE).includes(piece)) {
 178       this.kingPos[c][0] = move.appear[0].x;
 179       this.kingPos[c][1] = move.appear[0].y;
 180       this.castleFlags[c] = [V.size.y, V.size.y];
 181       return;
 182     }
 183     super.updateCastleFlags(move);
 184   }
 185
 186   postUndo(move) {
 187     // (Potentially) Reset king position
 188     const c = this.getColor(move.start.x, move.start.y);
 189     const piece = move.appear[0].p;
 190     if (piece == V.KING || Object.keys(V.KING_DECODE).includes(piece))
 191       this.kingPos[c] = [move.start.x, move.start.y];
 192   }
 193
 194   static get VALUES() {
 195     return {
 196       p: 1,
 197       r: 5,
 198       n: 3,
 199       b: 3,
 200       q: 9,
 201       k: 5
 202     };
 203   }
 204
 205   static get SEARCH_DEPTH() {
 206     return 4;
 207   }
 208 };