client/src/variants/Synchrone.js

   1 import { ChessRules } from "@/base_rules";
   2 import { randInt } from "@/utils/alea";
   3
   4 export class SynchroneRules extends ChessRules {
   5   static get CanAnalyze() {
   6     return false;
   7   }
   8
   9   static get ShowMoves() {
  10     return "byrow";
  11   }
  12
  13   static IsGoodFen(fen) {
  14     if (!ChessRules.IsGoodFen(fen)) return false;
  15     const fenParsed = V.ParseFen(fen);
  16     // 5) Check whiteMove
  17     if (
  18       (
  19         fenParsed.turn == "b" &&
  20         // NOTE: do not check really JSON stringified move...
  21         (!fenParsed.whiteMove || fenParsed.whiteMove == "-")
  22       )
  23       ||
  24       (fenParsed.turn == "w" && fenParsed.whiteMove != "-")
  25     ) {
  26       return false;
  27     }
  28     return true;
  29   }
  30
  31   static IsGoodEnpassant(enpassant) {
  32     const epArray = enpassant.split(",");
  33     if (![2, 3].includes(epArray.length)) return false;
  34     epArray.forEach(epsq => {
  35       if (epsq != "-") {
  36         const ep = V.SquareToCoords(epsq);
  37         if (isNaN(ep.x) || !V.OnBoard(ep)) return false;
  38       }
  39     });
  40     return true;
  41   }
  42
  43   static ParseFen(fen) {
  44     const fenParts = fen.split(" ");
  45     return Object.assign(
  46       ChessRules.ParseFen(fen),
  47       { whiteMove: fenParts[5] }
  48     );
  49   }
  50
  51   static GenRandInitFen(randomness) {
  52     return ChessRules.GenRandInitFen(randomness).slice(0, -1) + "-,- -";
  53   }
  54
  55   getFen() {
  56     return super.getFen() + " " + this.getWhitemoveFen();
  57   }
  58
  59   getFenForRepeat() {
  60     return super.getFenForRepeat() + "_" + this.getWhitemoveFen();
  61   }
  62
  63   setOtherVariables(fen) {
  64     const parsedFen = V.ParseFen(fen);
  65     this.setFlags(parsedFen.flags);
  66     const epArray = parsedFen.enpassant.split(",");
  67     this.epSquares = [];
  68     epArray.forEach(epsq => this.epSquares.push(this.getEpSquare(epsq)));
  69     super.scanKings(fen);
  70     // Also init whiteMove
  71     this.whiteMove =
  72       parsedFen.whiteMove != "-"
  73         ? JSON.parse(parsedFen.whiteMove)
  74         : null;
  75   }
  76
  77   // After undo(): no need to re-set INIT_COL_KING
  78   scanKings() {
  79     this.kingPos = { w: [-1, -1], b: [-1, -1] };
  80     for (let i = 0; i < V.size.x; i++) {
  81       for (let j = 0; j < V.size.y; j++) {
  82         if (this.getPiece(i, j) == V.KING)
  83           this.kingPos[this.getColor(i, j)] = [i, j];
  84       }
  85     }
  86   }
  87
  88   getEnpassantFen() {
  89     const L = this.epSquares.length;
  90     let res = "";
  91     const start = L - 2 - (this.turn == 'b' ? 1 : 0);
  92     for (let i=start; i < L; i++) {
  93       if (!this.epSquares[i]) res += "-,";
  94       else res += V.CoordsToSquare(this.epSquares[i]) + ",";
  95     }
  96     return res.slice(0, -1);
  97   }
  98
  99   getWhitemoveFen() {
 100     if (!this.whiteMove) return "-";
 101     return JSON.stringify({
 102       start: this.whiteMove.start,
 103       end: this.whiteMove.end,
 104       appear: this.whiteMove.appear,
 105       vanish: this.whiteMove.vanish
 106     });
 107   }
 108
 109   getPossibleMovesFrom([x, y]) {
 110     return (
 111       this.filterValid(super.getPotentialMovesFrom([x, y]))
 112       // Augment with potential recaptures:
 113       .concat(this.getRecaptures())
 114     );
 115   }
 116
 117   // Aux function used to find opponent and self captures
 118   getCaptures(x, y, color) {
 119     const sliderAttack = (xx, yy, allowedSteps) => {
 120       const deltaX = xx - x,
 121             absDeltaX = Math.abs(deltaX);
 122       const deltaY = yy - y,
 123             absDeltaY = Math.abs(deltaY);
 124       const step = [ deltaX / absDeltaX || 0, deltaY / absDeltaY || 0 ];
 125       if (
 126         // Check that the step is a priori valid:
 127         (absDeltaX != absDeltaY && deltaX != 0 && deltaY != 0) ||
 128         allowedSteps.every(st => st[0] != step[0] || st[1] != step[1])
 129       ) {
 130         return null;
 131       }
 132       let sq = [ x + step[0], y + step[1] ];
 133       while (sq[0] != xx || sq[1] != yy) {
 134         // NOTE: no need to check OnBoard in this special case
 135         if (this.board[sq[0]][sq[1]] != V.EMPTY) return null;
 136         sq[0] += step[0];
 137         sq[1] += step[1];
 138       }
 139       return this.getBasicMove([xx, yy], [x, y]);
 140     };
 141     // Can I take on the square [x, y] ?
 142     // If yes, return the (list of) capturing move(s)
 143     let moves = [];
 144     for (let i=0; i<8; i++) {
 145       for (let j=0; j<8; j++) {
 146         if (this.getColor(i, j) == color) {
 147           switch (this.getPiece(i, j)) {
 148             case V.PAWN: {
 149               // Pushed pawns move as enemy pawns
 150               const shift = (color == 'w' ? 1 : -1);
 151               if (x + shift == i && Math.abs(y - j) == 1)
 152                 moves.push(this.getBasicMove([i, j], [x, y]));
 153               break;
 154             }
 155             case V.KNIGHT: {
 156               const deltaX = Math.abs(i - x);
 157               const deltaY = Math.abs(j - y);
 158               if (
 159                 deltaX + deltaY == 3 &&
 160                 [1, 2].includes(deltaX) &&
 161                 [1, 2].includes(deltaY)
 162               ) {
 163                 moves.push(this.getBasicMove([i, j], [x, y]));
 164               }
 165               break;
 166             }
 167             case V.KING:
 168               if (Math.abs(i - x) <= 1 && Math.abs(j - y) <= 1)
 169                 moves.push(this.getBasicMove([i, j], [x, y]));
 170               break;
 171             case V.ROOK: {
 172               const mv = sliderAttack(i, j, V.steps[V.ROOK]);
 173               if (!!mv) moves.push(mv);
 174               break;
 175             }
 176             case V.BISHOP: {
 177               const mv = sliderAttack(i, j, V.steps[V.BISHOP]);
 178               if (!!mv) moves.push(mv);
 179               break;
 180             }
 181             case V.QUEEN: {
 182               const mv = sliderAttack(
 183                 i, j, V.steps[V.ROOK].concat(V.steps[V.BISHOP]));
 184               if (!!mv) moves.push(mv);
 185               break;
 186             }
 187           }
 188         }
 189       }
 190     }
 191     return this.filterValid(moves);
 192   }
 193
 194   getRecaptures() {
 195     // 1) Generate all opponent's capturing moves
 196     let oppCaptureMoves = [];
 197     const color = this.turn;
 198     const oppCol = V.GetOppCol(color);
 199     for (let i=0; i<8; i++) {
 200       for (let j=0; j<8; j++) {
 201         if (
 202           this.getColor(i, j) == color &&
 203           // Do not consider king captures: self-captures of king are forbidden
 204           this.getPiece(i, j) != V.KING
 205         ) {
 206           Array.prototype.push.apply(
 207             oppCaptureMoves,
 208             this.getCaptures(i, j, oppCol)
 209           );
 210         }
 211       }
 212     }
 213     // 2) Play each opponent's capture, and see if back-captures are possible:
 214     // Lookup table to quickly decide if a move is already in list:
 215     let moveSet = {};
 216     let moves = [];
 217     oppCaptureMoves.forEach(m => {
 218       // If another opponent capture with same endpoint already processed, skip:
 219       const mHash = "m" + m.end.x + m.end.y;
 220       if (!moveSet[mHash]) {
 221         moveSet[mHash] = true;
 222         // Just make enemy piece disappear, to clear potential path:
 223         const justDisappear = {
 224           appear: [],
 225           vanish: [m.vanish[0]]
 226         };
 227         V.PlayOnBoard(this.board, justDisappear);
 228         // Can I take on [m.end.x, m.end.y] ? If yes, add to list:
 229         this.getCaptures(m.end.x, m.end.y, color).forEach(cm => moves.push(cm));
 230         V.UndoOnBoard(this.board, justDisappear);
 231       }
 232     });
 233     return moves;
 234   }
 235
 236   getAllValidMoves() {
 237     // Return possible moves + potential recaptures
 238     return super.getAllValidMoves().concat(this.getRecaptures());
 239   }
 240
 241   filterValid(moves) {
 242     if (moves.length == 0) return [];
 243     // filterValid can be called when it's "not our turn":
 244     const color = moves[0].vanish[0].c;
 245     return moves.filter(m => {
 246       const piece = m.vanish[0].p;
 247       if (piece == V.KING) {
 248         this.kingPos[color][0] = m.appear[0].x;
 249         this.kingPos[color][1] = m.appear[0].y;
 250       }
 251       V.PlayOnBoard(this.board, m);
 252       let res = !this.underCheck(color);
 253       V.UndoOnBoard(this.board, m);
 254       if (piece == V.KING) this.kingPos[color] = [m.start.x, m.start.y];
 255       return res;
 256     });
 257   }
 258
 259   atLeastOneMove(color) {
 260     const curTurn = this.turn;
 261     this.turn = color;
 262     const res = super.atLeastOneMove();
 263     this.turn = curTurn;
 264     return res;
 265   }
 266
 267   // White and black (partial) moves were played: merge
 268   resolveSynchroneMove(move) {
 269     const m1 = this.whiteMove;
 270     const m2 = move;
 271     // For PlayOnBoard (no need for start / end, irrelevant)
 272     let smove = {
 273       appear: [],
 274       vanish: [
 275         m1.vanish[0],
 276         m2.vanish[0]
 277       ]
 278     };
 279     if ((m1.end.x != m2.end.x) || (m1.end.y != m2.end.y)) {
 280       // Easy case: two independant moves (which may (self-)capture)
 281       smove.appear.push(m1.appear[0]);
 282       smove.appear.push(m2.appear[0]);
 283       // "Captured" pieces may have moved:
 284       if (m1.appear.length == 2) {
 285         // Castle
 286         smove.appear.push(m1.appear[1]);
 287         smove.vanish.push(m1.vanish[1]);
 288       } else if (
 289         m1.vanish.length == 2 &&
 290         (
 291           m1.vanish[1].x != m2.start.x ||
 292           m1.vanish[1].y != m2.start.y
 293         )
 294       ) {
 295         smove.vanish.push(m1.vanish[1]);
 296       }
 297       if (m2.appear.length == 2) {
 298         // Castle
 299         smove.appear.push(m2.appear[1]);
 300         smove.vanish.push(m2.vanish[1]);
 301       } else if (
 302         m2.vanish.length == 2 &&
 303         (
 304           m2.vanish[1].x != m1.start.x ||
 305           m2.vanish[1].y != m1.start.y
 306         )
 307       ) {
 308         smove.vanish.push(m2.vanish[1]);
 309       }
 310     } else {
 311       // Collision:
 312       if (m1.vanish.length == 1 && m2.vanish.length == 1) {
 313         // Easy case: both disappear except if one is a king
 314         const p1 = m1.vanish[0].p;
 315         const p2 = m2.vanish[0].p;
 316         if ([p1, p2].includes(V.KING)) {
 317           smove.appear.push({
 318             x: m1.end.x,
 319             y: m1.end.y,
 320             p: V.KING,
 321             c: (p1 == V.KING ? 'w' : 'b')
 322           });
 323         }
 324       } else {
 325         // One move is a self-capture and the other a normal capture:
 326         // only the self-capture appears
 327         const selfCaptureMove =
 328           m1.vanish[1].c == m1.vanish[0].c
 329             ? m1
 330             : m2;
 331         smove.appear.push({
 332           x: m1.end.x,
 333           y: m1.end.y,
 334           p: selfCaptureMove.appear[0].p,
 335           c: selfCaptureMove.vanish[0].c
 336         });
 337         smove.vanish.push({
 338           x: m1.end.x,
 339           y: m1.end.y,
 340           p: selfCaptureMove.vanish[1].p,
 341           c: selfCaptureMove.vanish[0].c
 342         });
 343       }
 344     }
 345     return smove;
 346   }
 347
 348   play(move) {
 349     move.flags = JSON.stringify(this.aggregateFlags()); //save flags (for undo)
 350     this.epSquares.push(this.getEpSquare(move));
 351     // Do not play on board (would reveal the move...)
 352     this.turn = V.GetOppCol(this.turn);
 353     this.movesCount++;
 354     this.postPlay(move);
 355   }
 356
 357   updateCastleFlags(move) {
 358     const firstRank = { 'w': V.size.x - 1, 'b': 0 };
 359     move.appear.concat(move.vanish).forEach(av => {
 360       for (let c of ['w', 'b']) {
 361         if (av.x == firstRank[c] && this.castleFlags[c].includes(av.y)) {
 362           const flagIdx = (av.y == this.castleFlags[c][0] ? 0 : 1);
 363           this.castleFlags[c][flagIdx] = 8;
 364         }
 365       }
 366     });
 367   }
 368
 369   postPlay(move) {
 370     if (this.turn == 'b') {
 371       // NOTE: whiteMove is used read-only, so no need to copy
 372       this.whiteMove = move;
 373       return;
 374     }
 375
 376     // A full turn just ended:
 377     const smove = this.resolveSynchroneMove(move);
 378     V.PlayOnBoard(this.board, smove);
 379     move.whiteMove = this.whiteMove; //for undo
 380     this.whiteMove = null;
 381
 382     // Update king position + flags
 383     let kingAppear = { 'w': false, 'b': false };
 384     for (let i=0; i<smove.appear.length; i++) {
 385       if (smove.appear[i].p == V.KING) {
 386         const c = smove.appear[i].c;
 387         kingAppear[c] = true;
 388         this.kingPos[c][0] = smove.appear[i].x;
 389         this.kingPos[c][1] = smove.appear[i].y;
 390       }
 391     }
 392     for (let i=0; i<smove.vanish.length; i++) {
 393       if (smove.vanish[i].p == V.KING) {
 394         const c = smove.vanish[i].c;
 395         if (!kingAppear[c]) {
 396           this.kingPos[c][0] = -1;
 397           this.kingPos[c][1] = -1;
 398         }
 399         break;
 400       }
 401     }
 402     this.updateCastleFlags(smove);
 403     move.smove = smove;
 404   }
 405
 406   undo(move) {
 407     this.epSquares.pop();
 408     this.disaggregateFlags(JSON.parse(move.flags));
 409     if (this.turn == 'w')
 410       // Back to the middle of the move
 411       V.UndoOnBoard(this.board, move.smove);
 412     this.turn = V.GetOppCol(this.turn);
 413     this.movesCount--;
 414     this.postUndo(move);
 415   }
 416
 417   postUndo(move) {
 418     if (this.turn == 'w') {
 419       // Reset king positions: scan board
 420       this.scanKings();
 421       // Also reset whiteMove
 422       this.whiteMove = null;
 423     } else this.whiteMove = move.whiteMove;
 424   }
 425
 426   getCheckSquares(color) {
 427     if (color == 'b') {
 428       // kingPos must be reset for appropriate highlighting:
 429       var lastMove = JSON.parse(JSON.stringify(this.whiteMove));
 430       this.undo(lastMove); //will erase whiteMove, thus saved above
 431     }
 432     let res = [];
 433     if (this.kingPos['w'][0] >= 0 && this.underCheck('w'))
 434       res.push(JSON.parse(JSON.stringify(this.kingPos['w'])));
 435     if (this.kingPos['b'][0] >= 0 && this.underCheck('b'))
 436       res.push(JSON.parse(JSON.stringify(this.kingPos['b'])));
 437     if (color == 'b') this.play(lastMove);
 438     return res;
 439   }
 440
 441   getCurrentScore() {
 442     if (this.turn == 'b')
 443       // Turn (white + black) not over yet
 444       return "*";
 445     // Was a king captured?
 446     if (this.kingPos['w'][0] < 0) return "0-1";
 447     if (this.kingPos['b'][0] < 0) return "1-0";
 448     const whiteCanMove = this.atLeastOneMove('w');
 449     const blackCanMove = this.atLeastOneMove('b');
 450     if (whiteCanMove && blackCanMove) return "*";
 451     // Game over
 452     const whiteInCheck = this.underCheck('w');
 453     const blackInCheck = this.underCheck('b');
 454     if (
 455       (whiteCanMove && !this.underCheck('b')) ||
 456       (blackCanMove && !this.underCheck('w'))
 457     ) {
 458       return "1/2";
 459     }
 460     // Checkmate: could be mutual
 461     if (!whiteCanMove && !blackCanMove) return "1/2";
 462     return (whiteCanMove ? "1-0" : "0-1");
 463   }
 464
 465   getComputerMove() {
 466     const maxeval = V.INFINITY;
 467     const color = this.turn;
 468     let moves = this.getAllValidMoves();
 469     if (moves.length == 0)
 470       // TODO: this situation should not happen
 471       return null;
 472
 473     if (Math.random() < 0.5)
 474       // Return a random move
 475       return moves[randInt(moves.length)];
 476
 477     // Rank moves at depth 1:
 478     // try to capture something (not re-capturing)
 479     moves.forEach(m => {
 480       V.PlayOnBoard(this.board, m);
 481       m.eval = this.evalPosition();
 482       V.UndoOnBoard(this.board, m);
 483     });
 484     moves.sort((a, b) => {
 485       return (color == "w" ? 1 : -1) * (b.eval - a.eval);
 486     });
 487     let candidates = [0];
 488     for (let i = 1; i < moves.length && moves[i].eval == moves[0].eval; i++)
 489       candidates.push(i);
 490     return moves[candidates[randInt(candidates.length)]];
 491   }
 492
 493   getNotation(move) {
 494     if (move.appear.length == 2 && move.appear[0].p == V.KING)
 495       // Castle
 496       return move.end.y < move.start.y ? "0-0-0" : "0-0";
 497     // Basic system: piece + init + dest square
 498     return (
 499       move.vanish[0].p.toUpperCase() +
 500       V.CoordsToSquare(move.start) +
 501       V.CoordsToSquare(move.end)
 502     );
 503   }
 504 };