client/src/variants/Wormhole.js

   1 import { ChessRules } from "@/base_rules";
   2
   3 export const VariantRules = class WormholeRules extends ChessRules {
   4   static get HasFlags() {
   5     return false;
   6   }
   7
   8   static get HasEnpassant() {
   9     return false;
  10   }
  11
  12   static get HOLE() {
  13     return "xx";
  14   }
  15
  16   static board2fen(b) {
  17     if (b[0] == 'x') return 'x';
  18     return ChessRules.board2fen(b);
  19   }
  20
  21   static fen2board(f) {
  22     if (f == 'x') return V.HOLE;
  23     return ChessRules.fen2board(f);
  24   }
  25
  26   getPpath(b) {
  27     if (b[0] == 'x') return "Wormhole/hole";
  28     return b;
  29   }
  30
  31   getSquareAfter(square, movement) {
  32     let shift1, shift2;
  33     if (Array.isArray(movement[0])) {
  34       // A knight
  35       shift1 = movement[0];
  36       shift2 = movement[1];
  37     } else {
  38       shift1 = movement;
  39       shift2 = null;
  40     }
  41     const tryMove = (init, shift) => {
  42       let step = [
  43         shift[0] / Math.abs(shift[0]) || 0,
  44         shift[1] / Math.abs(shift[1]) || 0,
  45       ];
  46       const nbSteps = Math.max(Math.abs(shift[0]), Math.abs(shift[1]));
  47       let stepsAchieved = 0;
  48       let sq = [init[0] + step[0], init[1] + step[1]];
  49       while (V.OnBoard(sq[0],sq[1])) {
  50         if (this.board[sq[0]][sq[1]] != V.HOLE)
  51           stepsAchieved++;
  52         if (stepsAchieved < nbSteps) {
  53           sq[0] += step[0];
  54           sq[1] += step[1];
  55         }
  56         else break;
  57       }
  58       if (stepsAchieved < nbSteps)
  59         // The move is impossible
  60         return null;
  61       return sq;
  62     };
  63     // First, apply shift1
  64     let dest = tryMove(square, shift1);
  65     if (dest && shift2)
  66       // A knight: apply second shift
  67       dest = tryMove(dest, shift2);
  68     return dest;
  69   }
  70
  71   // NOTE (TODO?): some extra work done in some function because informations
  72   // on one step should ease the computation for a step in the same direction.
  73   static get steps() {
  74     return {
  75       r: [
  76         [-1, 0],
  77         [1, 0],
  78         [0, -1],
  79         [0, 1],
  80         [-2, 0],
  81         [2, 0],
  82         [0, -2],
  83         [0, 2]
  84       ],
  85       // Decompose knight movements into one step orthogonal + one diagonal
  86       n: [
  87         [[0, -1], [-1, -1]],
  88         [[0, -1], [1, -1]],
  89         [[-1, 0], [-1,-1]],
  90         [[-1, 0], [-1, 1]],
  91         [[0, 1], [-1, 1]],
  92         [[0, 1], [1, 1]],
  93         [[1, 0], [1, -1]],
  94         [[1, 0], [1, 1]]
  95       ],
  96       b: [
  97         [-1, -1],
  98         [-1, 1],
  99         [1, -1],
 100         [1, 1],
 101         [-2, -2],
 102         [-2, 2],
 103         [2, -2],
 104         [2, 2]
 105       ],
 106       k: [
 107         [-1, 0],
 108         [1, 0],
 109         [0, -1],
 110         [0, 1],
 111         [-1, -1],
 112         [-1, 1],
 113         [1, -1],
 114         [1, 1]
 115       ]
 116     };
 117   }
 118
 119   getJumpMoves([x, y], steps) {
 120     let moves = [];
 121     for (let step of steps) {
 122       const sq = this.getSquareAfter([x,y], step);
 123       if (sq &&
 124         (
 125           this.board[sq[0]][sq[1]] == V.EMPTY ||
 126           this.canTake([x, y], sq)
 127         )
 128       ) {
 129           moves.push(this.getBasicMove([x, y], sq));
 130       }
 131     }
 132     return moves;
 133   }
 134
 135   // What are the pawn moves from square x,y ?
 136   getPotentialPawnMoves([x, y]) {
 137     const color = this.turn;
 138     let moves = [];
 139     const [sizeX, sizeY] = [V.size.x, V.size.y];
 140     const shiftX = color == "w" ? -1 : 1;
 141     const startRank = color == "w" ? sizeX - 2 : 1;
 142     const lastRank = color == "w" ? 0 : sizeX - 1;
 143
 144     const sq1 = this.getSquareAfter([x,y], [shiftX,0]);
 145     if (sq1 && this.board[sq1[0]][y] == V.EMPTY) {
 146       // One square forward (cannot be a promotion)
 147       moves.push(this.getBasicMove([x, y], [sq1[0], y]));
 148       if (x == startRank) {
 149         // If two squares after is available, then move is possible
 150         const sq2 = this.getSquareAfter([x,y], [2*shiftX,0]);
 151         if (sq2 && this.board[sq2[0]][y] == V.EMPTY)
 152           // Two squares jump
 153           moves.push(this.getBasicMove([x, y], [sq2[0], y]));
 154       }
 155     }
 156     // Captures
 157     for (let shiftY of [-1, 1]) {
 158       const sq = this.getSquareAfter([x,y], [shiftX,shiftY]);
 159       if (
 160         !!sq &&
 161         this.board[sq[0]][sq[1]] != V.EMPTY &&
 162         this.canTake([x, y], [sq[0], sq[1]])
 163       ) {
 164         const finalPieces = sq[0] == lastRank
 165           ? [V.ROOK, V.KNIGHT, V.BISHOP, V.QUEEN]
 166           : [V.PAWN];
 167         for (let piece of finalPieces) {
 168           moves.push(
 169             this.getBasicMove([x, y], [sq[0], sq[1]], {
 170               c: color,
 171               p: piece
 172             })
 173           );
 174         }
 175       }
 176     }
 177
 178     return moves;
 179   }
 180
 181   getPotentialRookMoves(sq) {
 182     return this.getJumpMoves(sq, V.steps[V.ROOK]);
 183   }
 184
 185   getPotentialKnightMoves(sq) {
 186     return this.getJumpMoves(sq, V.steps[V.KNIGHT]);
 187   }
 188
 189   getPotentialBishopMoves(sq) {
 190     return this.getJumpMoves(sq, V.steps[V.BISHOP]);
 191   }
 192
 193   getPotentialQueenMoves(sq) {
 194     return this.getJumpMoves(
 195       sq,
 196       V.steps[V.ROOK].concat(V.steps[V.BISHOP])
 197     );
 198   }
 199
 200   getPotentialKingMoves(sq) {
 201     return this.getJumpMoves(sq, V.steps[V.KING]);
 202   }
 203
 204   isAttackedByJump([x, y], colors, piece, steps) {
 205     for (let step of steps) {
 206       const sq = this.getSquareAfter([x,y], step);
 207       if (
 208         sq &&
 209         this.getPiece(sq[0], sq[1]) === piece &&
 210         colors.includes(this.getColor(sq[0], sq[1]))
 211       ) {
 212         return true;
 213       }
 214     }
 215     return false;
 216   }
 217
 218   isAttackedByPawn([x, y], colors) {
 219     for (let c of colors) {
 220       const pawnShift = c == "w" ? 1 : -1;
 221       for (let i of [-1, 1]) {
 222         const sq = this.getSquareAfter([x,y], [pawnShift,i]);
 223         if (
 224           sq &&
 225           this.getPiece(sq[0], sq[1]) == V.PAWN &&
 226           this.getColor(sq[0], sq[1]) == c
 227         ) {
 228           return true;
 229         }
 230       }
 231     }
 232     return false;
 233   }
 234
 235   isAttackedByRook(sq, colors) {
 236     return this.isAttackedByJump(sq, colors, V.ROOK, V.steps[V.ROOK]);
 237   }
 238
 239   isAttackedByKnight(sq, colors) {
 240     // NOTE: knight attack is not symmetric in this variant:
 241     // steps order need to be reversed.
 242     return this.isAttackedByJump(
 243       sq,
 244       colors,
 245       V.KNIGHT,
 246       V.steps[V.KNIGHT].map(s => s.reverse())
 247     );
 248   }
 249
 250   isAttackedByBishop(sq, colors) {
 251     return this.isAttackedByJump(sq, colors, V.BISHOP, V.steps[V.BISHOP]);
 252   }
 253
 254   isAttackedByQueen(sq, colors) {
 255     return this.isAttackedByJump(
 256       sq,
 257       colors,
 258       V.QUEEN,
 259       V.steps[V.ROOK].concat(V.steps[V.BISHOP])
 260     );
 261   }
 262
 263   isAttackedByKing(sq, colors) {
 264     return this.isAttackedByJump(sq, colors, V.KING, V.steps[V.KING]);
 265   }
 266
 267   // NOTE: altering move in getBasicMove doesn't work and wouldn't be logical.
 268   // This is a side-effect on board generated by the move.
 269   static PlayOnBoard(board, move) {
 270     board[move.vanish[0].x][move.vanish[0].y] = V.HOLE;
 271     for (let psq of move.appear) board[psq.x][psq.y] = psq.c + psq.p;
 272   }
 273
 274   getCurrentScore() {
 275     if (this.atLeastOneMove())
 276       return "*";
 277     // No valid move: I lose
 278     return this.turn == "w" ? "0-1" : "1-0";
 279   }
 280
 281   static get SEARCH_DEPTH() {
 282     return 2;
 283   }
 284
 285   evalPosition() {
 286     let evaluation = 0;
 287     for (let i = 0; i < V.size.x; i++) {
 288       for (let j = 0; j < V.size.y; j++) {
 289         if (![V.EMPTY,V.HOLE].includes(this.board[i][j])) {
 290           const sign = this.getColor(i, j) == "w" ? 1 : -1;
 291           evaluation += sign * V.VALUES[this.getPiece(i, j)];
 292         }
 293       }
 294     }
 295     return evaluation;
 296   }
 297
 298   getNotation(move) {
 299     const piece = this.getPiece(move.start.x, move.start.y);
 300     // Indicate start square + dest square, because holes distort the board
 301     let notation =
 302       (piece != V.PAWN ? piece.toUpperCase() : "") +
 303       V.CoordsToSquare(move.start) +
 304       (move.vanish.length > move.appear.length ? "x" : "") +
 305       V.CoordsToSquare(move.end);
 306     if (piece == V.PAWN && move.appear[0].p != V.PAWN)
 307       // Promotion
 308       notation += "=" + move.appear[0].p.toUpperCase();
 309     return notation;
 310   }
 311 };