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     let moves = this.filterValid(super.getPotentialMovesFrom([x, y]));
 111     if (!this.underCheck(this.getColor(x, y)))
 112       // Augment with potential recaptures, except if we are under check
 113       Array.prototype.push.apply(moves, this.getRecaptures([x, y]));
 114     return moves;
 115   }
 116
 117   // Aux function used to find opponent and self captures
 118   getCaptures(from, to, color) {
 119     const sliderAttack = (xx, yy, allowedSteps) => {
 120       const deltaX = xx - to[0],
 121             absDeltaX = Math.abs(deltaX);
 122       const deltaY = yy - to[1],
 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 = [ to[0] + step[0], to[1] + 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], [to[0], to[1]]);
 140     };
 141     // Can I take on the square 'to' ?
 142     // If yes, return the (list of) capturing move(s)
 143     const getTargetedCaptures = ([i, j]) => {
 144       let move = null;
 145       // From [i, j]:
 146       switch (this.getPiece(i, j)) {
 147         case V.PAWN: {
 148           // Pushed pawns move as enemy pawns
 149           const shift = (color == 'w' ? 1 : -1);
 150           if (to[0] + shift == i && Math.abs(to[1] - j) == 1)
 151             move = this.getBasicMove([i, j], to);
 152           break;
 153         }
 154         case V.KNIGHT: {
 155           const deltaX = Math.abs(i - to[0]);
 156           const deltaY = Math.abs(j - to[1]);
 157           if (
 158             deltaX + deltaY == 3 &&
 159             [1, 2].includes(deltaX) &&
 160             [1, 2].includes(deltaY)
 161           ) {
 162             move = this.getBasicMove([i, j], to);
 163           }
 164           break;
 165         }
 166         case V.KING:
 167           if (Math.abs(i - to[0]) <= 1 && Math.abs(j - to[1]) <= 1)
 168             move = this.getBasicMove([i, j], to);
 169           break;
 170         case V.ROOK: {
 171           move = sliderAttack(i, j, V.steps[V.ROOK]);
 172           break;
 173         }
 174         case V.BISHOP: {
 175           move = sliderAttack(i, j, V.steps[V.BISHOP]);
 176           break;
 177         }
 178         case V.QUEEN: {
 179           move = sliderAttack(i, j, V.steps[V.ROOK].concat(V.steps[V.BISHOP]));
 180           break;
 181         }
 182       }
 183       return move;
 184     };
 185     let moves = [];
 186     if (!!from) {
 187       const theMove = getTargetedCaptures(from);
 188       if (!!theMove) moves.push(theMove);
 189     }
 190     else {
 191       for (let i=0; i<8; i++) {
 192         for (let j=0; j<8; j++) {
 193           if (this.getColor(i, j) == color) {
 194             const newMove = getTargetedCaptures([i, j]);
 195             if (!!newMove) moves.push(newMove);
 196           }
 197         }
 198       }
 199     }
 200     return this.filterValid(moves);
 201   }
 202
 203   getRecaptures(from) {
 204     // 1) Generate all opponent's capturing moves
 205     let oppCaptureMoves = [];
 206     const color = this.turn;
 207     const oppCol = V.GetOppCol(color);
 208     for (let i=0; i<8; i++) {
 209       for (let j=0; j<8; j++) {
 210         if (
 211           this.getColor(i, j) == color &&
 212           // Do not consider king captures: self-captures of king are forbidden
 213           this.getPiece(i, j) != V.KING
 214         ) {
 215           Array.prototype.push.apply(
 216             oppCaptureMoves,
 217             this.getCaptures(null, [i, j], oppCol)
 218           );
 219         }
 220       }
 221     }
 222     // 2) Play each opponent's capture, and see if back-captures are possible:
 223     // Lookup table to quickly decide if a move is already in list:
 224     let moveSet = {};
 225     let moves = [];
 226     oppCaptureMoves.forEach(m => {
 227       // If another opponent capture with same endpoint already processed, skip
 228       const mHash = "m" + m.end.x + m.end.y;
 229       if (!moveSet[mHash]) {
 230         moveSet[mHash] = true;
 231         // Just make enemy piece disappear, to clear potential path:
 232         const justDisappear = {
 233           appear: [],
 234           vanish: [m.vanish[0]]
 235         };
 236         V.PlayOnBoard(this.board, justDisappear);
 237         // Can I take on [m.end.x, m.end.y] ? If yes, add to list:
 238         this.getCaptures(from, [m.end.x, m.end.y], color)
 239           .forEach(cm => moves.push(cm));
 240         V.UndoOnBoard(this.board, justDisappear);
 241       }
 242     });
 243     return moves;
 244   }
 245
 246   getAllValidMoves() {
 247     // Return possible moves + potential recaptures
 248     return super.getAllValidMoves().concat(this.getRecaptures());
 249   }
 250
 251   filterValid(moves) {
 252     if (moves.length == 0) return [];
 253     // filterValid can be called when it's "not our turn":
 254     const color = moves[0].vanish[0].c;
 255     return moves.filter(m => {
 256       const piece = m.vanish[0].p;
 257       if (piece == V.KING) {
 258         this.kingPos[color][0] = m.appear[0].x;
 259         this.kingPos[color][1] = m.appear[0].y;
 260       }
 261       V.PlayOnBoard(this.board, m);
 262       let res = !this.underCheck(color);
 263       V.UndoOnBoard(this.board, m);
 264       if (piece == V.KING) this.kingPos[color] = [m.start.x, m.start.y];
 265       return res;
 266     });
 267   }
 268
 269   atLeastOneMove(color) {
 270     const curTurn = this.turn;
 271     this.turn = color;
 272     const res = super.atLeastOneMove();
 273     this.turn = curTurn;
 274     return res;
 275   }
 276
 277   // White and black (partial) moves were played: merge
 278   resolveSynchroneMove(move) {
 279     const m1 = this.whiteMove;
 280     const m2 = move;
 281     // For PlayOnBoard (no need for start / end, irrelevant)
 282     let smove = {
 283       appear: [],
 284       vanish: [
 285         m1.vanish[0],
 286         m2.vanish[0]
 287       ]
 288     };
 289     if ((m1.end.x != m2.end.x) || (m1.end.y != m2.end.y)) {
 290       // Easy case: two independant moves (which may (self-)capture)
 291       smove.appear.push(m1.appear[0]);
 292       smove.appear.push(m2.appear[0]);
 293       // "Captured" pieces may have moved:
 294       if (m1.appear.length == 2) {
 295         // Castle
 296         smove.appear.push(m1.appear[1]);
 297         smove.vanish.push(m1.vanish[1]);
 298       } else if (
 299         m1.vanish.length == 2 &&
 300         (
 301           m1.vanish[1].x != m2.start.x ||
 302           m1.vanish[1].y != m2.start.y
 303         )
 304       ) {
 305         smove.vanish.push(m1.vanish[1]);
 306       }
 307       if (m2.appear.length == 2) {
 308         // Castle
 309         smove.appear.push(m2.appear[1]);
 310         smove.vanish.push(m2.vanish[1]);
 311       } else if (
 312         m2.vanish.length == 2 &&
 313         (
 314           m2.vanish[1].x != m1.start.x ||
 315           m2.vanish[1].y != m1.start.y
 316         )
 317       ) {
 318         smove.vanish.push(m2.vanish[1]);
 319       }
 320     } else {
 321       // Collision:
 322       if (m1.vanish.length == 1 && m2.vanish.length == 1) {
 323         // Easy case: both disappear except if one is a king
 324         const p1 = m1.vanish[0].p;
 325         const p2 = m2.vanish[0].p;
 326         if ([p1, p2].includes(V.KING)) {
 327           smove.appear.push({
 328             x: m1.end.x,
 329             y: m1.end.y,
 330             p: V.KING,
 331             c: (p1 == V.KING ? 'w' : 'b')
 332           });
 333         }
 334       } else {
 335         // One move is a self-capture and the other a normal capture:
 336         // only the self-capture appears
 337         const selfCaptureMove =
 338           m1.vanish[1].c == m1.vanish[0].c
 339             ? m1
 340             : m2;
 341         smove.appear.push({
 342           x: m1.end.x,
 343           y: m1.end.y,
 344           p: selfCaptureMove.appear[0].p,
 345           c: selfCaptureMove.vanish[0].c
 346         });
 347         smove.vanish.push({
 348           x: m1.end.x,
 349           y: m1.end.y,
 350           p: selfCaptureMove.vanish[1].p,
 351           c: selfCaptureMove.vanish[0].c
 352         });
 353       }
 354     }
 355     return smove;
 356   }
 357
 358   play(move) {
 359     move.flags = JSON.stringify(this.aggregateFlags()); //save flags (for undo)
 360     this.epSquares.push(this.getEpSquare(move));
 361     // Do not play on board (would reveal the move...)
 362     this.turn = V.GetOppCol(this.turn);
 363     this.movesCount++;
 364     this.postPlay(move);
 365   }
 366
 367   updateCastleFlags(move) {
 368     const firstRank = { 'w': V.size.x - 1, 'b': 0 };
 369     move.appear.concat(move.vanish).forEach(av => {
 370       for (let c of ['w', 'b']) {
 371         if (av.x == firstRank[c] && this.castleFlags[c].includes(av.y)) {
 372           const flagIdx = (av.y == this.castleFlags[c][0] ? 0 : 1);
 373           this.castleFlags[c][flagIdx] = 8;
 374         }
 375       }
 376     });
 377   }
 378
 379   postPlay(move) {
 380     if (this.turn == 'b') {
 381       // NOTE: whiteMove is used read-only, so no need to copy
 382       this.whiteMove = move;
 383       return;
 384     }
 385
 386     // A full turn just ended:
 387     const smove = this.resolveSynchroneMove(move);
 388     V.PlayOnBoard(this.board, smove);
 389     move.whiteMove = this.whiteMove; //for undo
 390     this.whiteMove = null;
 391
 392     // Update king position + flags
 393     let kingAppear = { 'w': false, 'b': false };
 394     for (let i=0; i<smove.appear.length; i++) {
 395       if (smove.appear[i].p == V.KING) {
 396         const c = smove.appear[i].c;
 397         kingAppear[c] = true;
 398         this.kingPos[c][0] = smove.appear[i].x;
 399         this.kingPos[c][1] = smove.appear[i].y;
 400       }
 401     }
 402     for (let i=0; i<smove.vanish.length; i++) {
 403       if (smove.vanish[i].p == V.KING) {
 404         const c = smove.vanish[i].c;
 405         if (!kingAppear[c]) {
 406           this.kingPos[c][0] = -1;
 407           this.kingPos[c][1] = -1;
 408         }
 409         break;
 410       }
 411     }
 412     this.updateCastleFlags(smove);
 413     move.smove = smove;
 414   }
 415
 416   undo(move) {
 417     this.epSquares.pop();
 418     this.disaggregateFlags(JSON.parse(move.flags));
 419     if (this.turn == 'w')
 420       // Back to the middle of the move
 421       V.UndoOnBoard(this.board, move.smove);
 422     this.turn = V.GetOppCol(this.turn);
 423     this.movesCount--;
 424     this.postUndo(move);
 425   }
 426
 427   postUndo(move) {
 428     if (this.turn == 'w') {
 429       // Reset king positions: scan board
 430       this.scanKings();
 431       // Also reset whiteMove
 432       this.whiteMove = null;
 433     } else this.whiteMove = move.whiteMove;
 434   }
 435
 436   getCheckSquares(color) {
 437     if (color == 'b') {
 438       // kingPos must be reset for appropriate highlighting:
 439       var lastMove = JSON.parse(JSON.stringify(this.whiteMove));
 440       this.undo(lastMove); //will erase whiteMove, thus saved above
 441     }
 442     let res = [];
 443     if (this.kingPos['w'][0] >= 0 && this.underCheck('w'))
 444       res.push(JSON.parse(JSON.stringify(this.kingPos['w'])));
 445     if (this.kingPos['b'][0] >= 0 && this.underCheck('b'))
 446       res.push(JSON.parse(JSON.stringify(this.kingPos['b'])));
 447     if (color == 'b') this.play(lastMove);
 448     return res;
 449   }
 450
 451   getCurrentScore() {
 452     if (this.turn == 'b')
 453       // Turn (white + black) not over yet
 454       return "*";
 455     // Was a king captured?
 456     if (this.kingPos['w'][0] < 0) return "0-1";
 457     if (this.kingPos['b'][0] < 0) return "1-0";
 458     const whiteCanMove = this.atLeastOneMove('w');
 459     const blackCanMove = this.atLeastOneMove('b');
 460     if (whiteCanMove && blackCanMove) return "*";
 461     // Game over
 462     const whiteInCheck = this.underCheck('w');
 463     const blackInCheck = this.underCheck('b');
 464     if (
 465       (whiteCanMove && !this.underCheck('b')) ||
 466       (blackCanMove && !this.underCheck('w'))
 467     ) {
 468       return "1/2";
 469     }
 470     // Checkmate: could be mutual
 471     if (!whiteCanMove && !blackCanMove) return "1/2";
 472     return (whiteCanMove ? "1-0" : "0-1");
 473   }
 474
 475   getComputerMove() {
 476     const maxeval = V.INFINITY;
 477     const color = this.turn;
 478     let moves = this.getAllValidMoves();
 479     if (moves.length == 0)
 480       // TODO: this situation should not happen
 481       return null;
 482
 483     if (Math.random() < 0.5)
 484       // Return a random move
 485       return moves[randInt(moves.length)];
 486
 487     // Rank moves at depth 1:
 488     // try to capture something (not re-capturing)
 489     moves.forEach(m => {
 490       V.PlayOnBoard(this.board, m);
 491       m.eval = this.evalPosition();
 492       V.UndoOnBoard(this.board, m);
 493     });
 494     moves.sort((a, b) => {
 495       return (color == "w" ? 1 : -1) * (b.eval - a.eval);
 496     });
 497     let candidates = [0];
 498     for (let i = 1; i < moves.length && moves[i].eval == moves[0].eval; i++)
 499       candidates.push(i);
 500     return moves[candidates[randInt(candidates.length)]];
 501   }
 502
 503   getNotation(move) {
 504     if (move.appear.length == 2 && move.appear[0].p == V.KING)
 505       // Castle
 506       return move.end.y < move.start.y ? "0-0-0" : "0-0";
 507     // Basic system: piece + init + dest square
 508     return (
 509       move.vanish[0].p.toUpperCase() +
 510       V.CoordsToSquare(move.start) +
 511       V.CoordsToSquare(move.end)
 512     );
 513   }
 514 };