client/src/variants/Checkered.js

   1 import { ChessRules } from "@/base_rules";
   2
   3 export const VariantRules = class CheckeredRules extends ChessRules {
   4   static board2fen(b) {
   5     const checkered_codes = {
   6       p: "s",
   7       q: "t",
   8       r: "u",
   9       b: "c",
  10       n: "o"
  11     };
  12     if (b[0] == "c") return checkered_codes[b[1]];
  13     return ChessRules.board2fen(b);
  14   }
  15
  16   static fen2board(f) {
  17     // Tolerate upper-case versions of checkered pieces (why not?)
  18     const checkered_pieces = {
  19       s: "p",
  20       S: "p",
  21       t: "q",
  22       T: "q",
  23       u: "r",
  24       U: "r",
  25       c: "b",
  26       C: "b",
  27       o: "n",
  28       O: "n"
  29     };
  30     if (Object.keys(checkered_pieces).includes(f))
  31       return "c" + checkered_pieces[f];
  32     return ChessRules.fen2board(f);
  33   }
  34
  35   static get PIECES() {
  36     return ChessRules.PIECES.concat(["s", "t", "u", "c", "o"]);
  37   }
  38
  39   getPpath(b) {
  40     return (b[0] == "c" ? "Checkered/" : "") + b;
  41   }
  42
  43   setOtherVariables(fen) {
  44     super.setOtherVariables(fen);
  45     // Local stack of non-capturing checkered moves:
  46     this.cmoves = [];
  47     const cmove = fen.split(" ")[5];
  48     if (cmove == "-") this.cmoves.push(null);
  49     else {
  50       this.cmoves.push({
  51         start: ChessRules.SquareToCoords(cmove.substr(0, 2)),
  52         end: ChessRules.SquareToCoords(cmove.substr(2))
  53       });
  54     }
  55   }
  56
  57   static IsGoodFen(fen) {
  58     if (!ChessRules.IsGoodFen(fen)) return false;
  59     const fenParts = fen.split(" ");
  60     if (fenParts.length != 6) return false;
  61     if (fenParts[5] != "-" && !fenParts[5].match(/^([a-h][1-8]){2}$/))
  62       return false;
  63     return true;
  64   }
  65
  66   static IsGoodFlags(flags) {
  67     // 4 for castle + 16 for pawns
  68     return !!flags.match(/^[01]{20,20}$/);
  69   }
  70
  71   setFlags(fenflags) {
  72     super.setFlags(fenflags); //castleFlags
  73     this.pawnFlags = {
  74       w: [...Array(8).fill(true)], //pawns can move 2 squares?
  75       b: [...Array(8).fill(true)]
  76     };
  77     const flags = fenflags.substr(4); //skip first 4 digits, for castle
  78     for (let c of ["w", "b"]) {
  79       for (let i = 0; i < 8; i++)
  80         this.pawnFlags[c][i] = flags.charAt((c == "w" ? 0 : 8) + i) == "1";
  81     }
  82   }
  83
  84   aggregateFlags() {
  85     return [this.castleFlags, this.pawnFlags];
  86   }
  87
  88   disaggregateFlags(flags) {
  89     this.castleFlags = flags[0];
  90     this.pawnFlags = flags[1];
  91   }
  92
  93   getEpSquare(moveOrSquare) {
  94     if (typeof moveOrSquare !== "object" || moveOrSquare.appear[0].c != 'c')
  95       return super.getEpSquare(moveOrSquare);
  96     // Checkered move: no en-passant
  97     return undefined;
  98   }
  99
 100   getCmove(move) {
 101     if (move.appear[0].c == "c" && move.vanish.length == 1)
 102       return { start: move.start, end: move.end };
 103     return null;
 104   }
 105
 106   canTake([x1, y1], [x2, y2]) {
 107     const color1 = this.getColor(x1, y1);
 108     const color2 = this.getColor(x2, y2);
 109     // Checkered aren't captured
 110     return (
 111       color1 != color2 &&
 112       color2 != "c" &&
 113       (color1 != "c" || color2 != this.turn)
 114     );
 115   }
 116
 117   // Post-processing: apply "checkerization" of standard moves
 118   getPotentialMovesFrom([x, y]) {
 119     let standardMoves = super.getPotentialMovesFrom([x, y]);
 120     const lastRank = this.turn == "w" ? 0 : 7;
 121     // King has to be treated differently (for castles)
 122     if (this.getPiece(x, y) == V.KING) return standardMoves;
 123     let moves = [];
 124     standardMoves.forEach(m => {
 125       if (m.vanish[0].p == V.PAWN) {
 126         if (
 127           Math.abs(m.end.x - m.start.x) == 2 &&
 128           !this.pawnFlags[this.turn][m.start.y]
 129         )
 130           return; //skip forbidden 2-squares jumps
 131         if (
 132           this.board[m.end.x][m.end.y] == V.EMPTY &&
 133           m.vanish.length == 2 &&
 134           this.getColor(m.start.x, m.start.y) == "c"
 135         ) {
 136           return; //checkered pawns cannot take en-passant
 137         }
 138       }
 139       if (m.vanish.length == 1) moves.push(m);
 140       // No capture
 141       else {
 142         // A capture occured (m.vanish.length == 2)
 143         m.appear[0].c = "c";
 144         moves.push(m);
 145         if (
 146           m.appear[0].p != m.vanish[1].p && //avoid promotions (already treated):
 147           (m.vanish[0].p != V.PAWN || m.end.x != lastRank)
 148         ) {
 149           // Add transformation into captured piece
 150           let m2 = JSON.parse(JSON.stringify(m));
 151           m2.appear[0].p = m.vanish[1].p;
 152           moves.push(m2);
 153         }
 154       }
 155     });
 156     return moves;
 157   }
 158
 159   getPotentialPawnMoves([x, y]) {
 160     const color = this.turn;
 161     let moves = [];
 162     const [sizeX, sizeY] = [V.size.x, V.size.y];
 163     const shiftX = color == "w" ? -1 : 1;
 164     const startRank = color == "w" ? sizeX - 2 : 1;
 165     const lastRank = color == "w" ? 0 : sizeX - 1;
 166     const pawnColor = this.getColor(x, y); //can be  checkered
 167
 168     const finalPieces =
 169       x + shiftX == lastRank
 170         ? [V.ROOK, V.KNIGHT, V.BISHOP, V.QUEEN]
 171         : [V.PAWN];
 172     if (this.board[x + shiftX][y] == V.EMPTY) {
 173       // One square forward
 174       for (let piece of finalPieces) {
 175         moves.push(
 176           this.getBasicMove([x, y], [x + shiftX, y], {
 177             c: pawnColor,
 178             p: piece
 179           })
 180         );
 181       }
 182       if (
 183         x == startRank &&
 184         this.board[x + 2 * shiftX][y] == V.EMPTY
 185       ) {
 186         // Two squares jump
 187         moves.push(this.getBasicMove([x, y], [x + 2 * shiftX, y]));
 188       }
 189     }
 190     // Captures
 191     for (let shiftY of [-1, 1]) {
 192       if (
 193         y + shiftY >= 0 &&
 194         y + shiftY < sizeY &&
 195         this.board[x + shiftX][y + shiftY] != V.EMPTY &&
 196         this.canTake([x, y], [x + shiftX, y + shiftY])
 197       ) {
 198         for (let piece of finalPieces) {
 199           moves.push(
 200             this.getBasicMove([x, y], [x + shiftX, y + shiftY], {
 201               c: pawnColor,
 202               p: piece
 203             })
 204           );
 205         }
 206       }
 207     }
 208
 209     // En passant
 210     const Lep = this.epSquares.length;
 211     const epSquare = this.epSquares[Lep - 1]; //always at least one element
 212     if (
 213       !!epSquare &&
 214       epSquare.x == x + shiftX &&
 215       Math.abs(epSquare.y - y) == 1
 216     ) {
 217       let enpassantMove = this.getBasicMove([x, y], [epSquare.x, epSquare.y]);
 218       enpassantMove.vanish.push({
 219         x: x,
 220         y: epSquare.y,
 221         p: "p",
 222         c: this.getColor(x, epSquare.y)
 223       });
 224       moves.push(enpassantMove);
 225     }
 226
 227     return moves;
 228   }
 229
 230   canIplay(side, [x, y]) {
 231     return side == this.turn && [side, "c"].includes(this.getColor(x, y));
 232   }
 233
 234   // Does m2 un-do m1 ? (to disallow undoing checkered moves)
 235   oppositeMoves(m1, m2) {
 236     return (
 237       m1 &&
 238       m2.appear[0].c == "c" &&
 239       m2.appear.length == 1 &&
 240       m2.vanish.length == 1 &&
 241       m1.start.x == m2.end.x &&
 242       m1.end.x == m2.start.x &&
 243       m1.start.y == m2.end.y &&
 244       m1.end.y == m2.start.y
 245     );
 246   }
 247
 248   filterValid(moves) {
 249     if (moves.length == 0) return [];
 250     const color = this.turn;
 251     const L = this.cmoves.length; //at least 1: init from FEN
 252     return moves.filter(m => {
 253       if (this.oppositeMoves(this.cmoves[L - 1], m)) return false;
 254       this.play(m);
 255       const res = !this.underCheck(color);
 256       this.undo(m);
 257       return res;
 258     });
 259   }
 260
 261   getAllValidMoves() {
 262     const oppCol = V.GetOppCol(this.turn);
 263     let potentialMoves = [];
 264     for (let i = 0; i < V.size.x; i++) {
 265       for (let j = 0; j < V.size.y; j++) {
 266         // NOTE: just testing == color isn't enough because of checkred pieces
 267         if (this.board[i][j] != V.EMPTY && this.getColor(i, j) != oppCol) {
 268           Array.prototype.push.apply(
 269             potentialMoves,
 270             this.getPotentialMovesFrom([i, j])
 271           );
 272         }
 273       }
 274     }
 275     return this.filterValid(potentialMoves);
 276   }
 277
 278   atLeastOneMove() {
 279     const oppCol = V.GetOppCol(this.turn);
 280     for (let i = 0; i < V.size.x; i++) {
 281       for (let j = 0; j < V.size.y; j++) {
 282         // NOTE: just testing == color isn't enough because of checkred pieces
 283         if (this.board[i][j] != V.EMPTY && this.getColor(i, j) != oppCol) {
 284           const moves = this.getPotentialMovesFrom([i, j]);
 285           if (moves.length > 0) {
 286             for (let k = 0; k < moves.length; k++) {
 287               if (this.filterValid([moves[k]]).length > 0) return true;
 288             }
 289           }
 290         }
 291       }
 292     }
 293     return false;
 294   }
 295
 296   isAttackedByPawn([x, y], colors) {
 297     for (let c of colors) {
 298       const color = c == "c" ? this.turn : c;
 299       let pawnShift = color == "w" ? 1 : -1;
 300       if (x + pawnShift >= 0 && x + pawnShift < 8) {
 301         for (let i of [-1, 1]) {
 302           if (
 303             y + i >= 0 &&
 304             y + i < 8 &&
 305             this.getPiece(x + pawnShift, y + i) == V.PAWN &&
 306             this.getColor(x + pawnShift, y + i) == c
 307           ) {
 308             return true;
 309           }
 310         }
 311       }
 312     }
 313     return false;
 314   }
 315
 316   underCheck(color) {
 317     return this.isAttacked(this.kingPos[color], [V.GetOppCol(color), "c"]);
 318   }
 319
 320   getCheckSquares(color) {
 321     // Artifically change turn, for checkered pawns
 322     this.turn = V.GetOppCol(color);
 323     const kingAttacked = this.isAttacked(this.kingPos[color], [
 324       V.GetOppCol(color),
 325       "c"
 326     ]);
 327     let res = kingAttacked
 328       ? [JSON.parse(JSON.stringify(this.kingPos[color]))] //need to duplicate!
 329       : [];
 330     this.turn = color;
 331     return res;
 332   }
 333
 334   updateVariables(move) {
 335     super.updateVariables(move);
 336     // Does this move turn off a 2-squares pawn flag?
 337     const secondRank = [1, 6];
 338     if (secondRank.includes(move.start.x) && move.vanish[0].p == V.PAWN)
 339       this.pawnFlags[move.start.x == 6 ? "w" : "b"][move.start.y] = false;
 340   }
 341
 342   getCurrentScore() {
 343     if (this.atLeastOneMove())
 344       // game not over
 345       return "*";
 346
 347     const color = this.turn;
 348     // Artifically change turn, for checkered pawns
 349     this.turn = V.GetOppCol(this.turn);
 350     const res = this.isAttacked(this.kingPos[color], [V.GetOppCol(color), "c"])
 351       ? color == "w"
 352         ? "0-1"
 353         : "1-0"
 354       : "1/2";
 355     this.turn = V.GetOppCol(this.turn);
 356     return res;
 357   }
 358
 359   evalPosition() {
 360     let evaluation = 0;
 361     // Just count material for now, considering checkered neutral (...)
 362     for (let i = 0; i < V.size.x; i++) {
 363       for (let j = 0; j < V.size.y; j++) {
 364         if (this.board[i][j] != V.EMPTY) {
 365           const sqColor = this.getColor(i, j);
 366           if (["w","b"].includes(sqColor)) {
 367             const sign = sqColor == "w" ? 1 : -1;
 368             evaluation += sign * V.VALUES[this.getPiece(i, j)];
 369           }
 370         }
 371       }
 372     }
 373     return evaluation;
 374   }
 375
 376   static GenRandInitFen(randomness) {
 377     return ChessRules.GenRandInitFen(randomness)
 378       // Add 16 pawns flags + empty cmove:
 379       .replace(" w 0 1111", " w 0 11111111111111111111 -");
 380   }
 381
 382   static ParseFen(fen) {
 383     return Object.assign({}, ChessRules.ParseFen(fen), {
 384       cmove: fen.split(" ")[5]
 385     });
 386   }
 387
 388   getFen() {
 389     const L = this.cmoves.length;
 390     const cmoveFen = !this.cmoves[L - 1]
 391       ? "-"
 392       : ChessRules.CoordsToSquare(this.cmoves[L - 1].start) +
 393         ChessRules.CoordsToSquare(this.cmoves[L - 1].end);
 394     return super.getFen() + " " + cmoveFen;
 395   }
 396
 397   getFlagsFen() {
 398     let fen = super.getFlagsFen();
 399     // Add pawns flags
 400     for (let c of ["w", "b"]) {
 401       for (let i = 0; i < 8; i++) fen += this.pawnFlags[c][i] ? "1" : "0";
 402     }
 403     return fen;
 404   }
 405
 406   // TODO (design): this cmove update here or in (un)updateVariables ?
 407   play(move) {
 408     this.cmoves.push(this.getCmove(move));
 409     super.play(move);
 410   }
 411
 412   undo(move) {
 413     this.cmoves.pop();
 414     super.undo(move);
 415   }
 416
 417   getNotation(move) {
 418     if (move.appear.length == 2) {
 419       // Castle
 420       if (move.end.y < move.start.y) return "0-0-0";
 421       return "0-0";
 422     }
 423
 424     // Translate final square
 425     const finalSquare = V.CoordsToSquare(move.end);
 426
 427     const piece = this.getPiece(move.start.x, move.start.y);
 428     if (piece == V.PAWN) {
 429       // Pawn move
 430       let notation = "";
 431       if (move.vanish.length > 1) {
 432         // Capture
 433         const startColumn = V.CoordToColumn(move.start.y);
 434         notation =
 435           startColumn +
 436           "x" +
 437           finalSquare +
 438           "=" +
 439           move.appear[0].p.toUpperCase();
 440       } //no capture
 441       else {
 442         notation = finalSquare;
 443         if (move.appear.length > 0 && piece != move.appear[0].p)
 444           //promotion
 445           notation += "=" + move.appear[0].p.toUpperCase();
 446       }
 447       return notation;
 448     }
 449     // Piece movement
 450     return (
 451       piece.toUpperCase() +
 452       (move.vanish.length > 1 ? "x" : "") +
 453       finalSquare +
 454       (move.vanish.length > 1 ? "=" + move.appear[0].p.toUpperCase() : "")
 455     );
 456   }
 457 };