client/src/variants/Eightpieces.js

   1 import { ArrayFun } from "@/utils/array";
   2 import { randInt } from "@/utils/alea";
   3 import { ChessRules, PiPo, Move } from "@/base_rules";
   4
   5 export class EightpiecesRules extends ChessRules {
   6   static get JAILER() {
   7     return "j";
   8   }
   9   static get SENTRY() {
  10     return "s";
  11   }
  12   static get LANCER() {
  13     return "l";
  14   }
  15
  16   static get IMAGE_EXTENSION() {
  17     // Temporarily, for the time SVG pieces are being designed:
  18     return ".png";
  19   }
  20
  21   // Lancer directions *from white perspective*
  22   static get LANCER_DIRS() {
  23     return {
  24       'c': [-1, 0], //north
  25       'd': [-1, 1], //N-E
  26       'e': [0, 1], //east
  27       'f': [1, 1], //S-E
  28       'g': [1, 0], //south
  29       'h': [1, -1], //S-W
  30       'm': [0, -1], //west
  31       'o': [-1, -1] //N-W
  32     };
  33   }
  34
  35   static get PIECES() {
  36     return ChessRules.PIECES
  37       .concat([V.JAILER, V.SENTRY])
  38       .concat(Object.keys(V.LANCER_DIRS));
  39   }
  40
  41   getPiece(i, j) {
  42     const piece = this.board[i][j].charAt(1);
  43     // Special lancer case: 8 possible orientations
  44     if (Object.keys(V.LANCER_DIRS).includes(piece)) return V.LANCER;
  45     return piece;
  46   }
  47
  48   getPpath(b, color, score, orientation) {
  49     if ([V.JAILER, V.SENTRY].includes(b[1])) return "Eightpieces/tmp_png/" + b;
  50     if (Object.keys(V.LANCER_DIRS).includes(b[1])) {
  51       if (orientation == 'w') return "Eightpieces/tmp_png/" + b;
  52       // Find opposite direction for adequate display:
  53       let oppDir = '';
  54       switch (b[1]) {
  55         case 'c':
  56           oppDir = 'g';
  57           break;
  58         case 'g':
  59           oppDir = 'c';
  60           break;
  61         case 'd':
  62           oppDir = 'h';
  63           break;
  64         case 'h':
  65           oppDir = 'd';
  66           break;
  67         case 'e':
  68           oppDir = 'm';
  69           break;
  70         case 'm':
  71           oppDir = 'e';
  72           break;
  73         case 'f':
  74           oppDir = 'o';
  75           break;
  76         case 'o':
  77           oppDir = 'f';
  78           break;
  79       }
  80       return "Eightpieces/tmp_png/" + b[0] + oppDir;
  81     }
  82     // TODO: after we have SVG pieces, remove the folder and next prefix:
  83     return "Eightpieces/tmp_png/" + b;
  84   }
  85
  86   getPPpath(b, orientation) {
  87     return this.getPpath(b, null, null, orientation);
  88   }
  89
  90   static ParseFen(fen) {
  91     const fenParts = fen.split(" ");
  92     return Object.assign(
  93       ChessRules.ParseFen(fen),
  94       { sentrypush: fenParts[5] }
  95     );
  96   }
  97
  98   static IsGoodFen(fen) {
  99     if (!ChessRules.IsGoodFen(fen)) return false;
 100     const fenParsed = V.ParseFen(fen);
 101     // 5) Check sentry push (if any)
 102     if (
 103       fenParsed.sentrypush != "-" &&
 104       !fenParsed.sentrypush.match(/^([a-h][1-8],?)+$/)
 105     ) {
 106       return false;
 107     }
 108     return true;
 109   }
 110
 111   getFen() {
 112     return super.getFen() + " " + this.getSentrypushFen();
 113   }
 114
 115   getFenForRepeat() {
 116     return super.getFenForRepeat() + "_" + this.getSentrypushFen();
 117   }
 118
 119   getSentrypushFen() {
 120     const L = this.sentryPush.length;
 121     if (!this.sentryPush[L-1]) return "-";
 122     let res = "";
 123     this.sentryPush[L-1].forEach(coords =>
 124       res += V.CoordsToSquare(coords) + ",");
 125     return res.slice(0, -1);
 126   }
 127
 128   setOtherVariables(fen) {
 129     super.setOtherVariables(fen);
 130     // subTurn == 2 only when a sentry moved, and is about to push something
 131     this.subTurn = 1;
 132     // Sentry position just after a "capture" (subTurn from 1 to 2)
 133     this.sentryPos = null;
 134     // Stack pieces' forbidden squares after a sentry move at each turn
 135     const parsedFen = V.ParseFen(fen);
 136     if (parsedFen.sentrypush == "-") this.sentryPush = [null];
 137     else {
 138       this.sentryPush = [
 139         parsedFen.sentrypush.split(",").map(sq => {
 140           return V.SquareToCoords(sq);
 141         })
 142       ];
 143     }
 144   }
 145
 146   static GenRandInitFen(randomness) {
 147     if (randomness == 0)
 148       // Deterministic:
 149       return "jsfqkbnr/pppppppp/8/8/8/8/PPPPPPPP/JSDQKBNR w 0 ahah - -";
 150
 151     let pieces = { w: new Array(8), b: new Array(8) };
 152     let flags = "";
 153     // Shuffle pieces on first (and last rank if randomness == 2)
 154     for (let c of ["w", "b"]) {
 155       if (c == 'b' && randomness == 1) {
 156         const lancerIdx = pieces['w'].findIndex(p => {
 157           return Object.keys(V.LANCER_DIRS).includes(p);
 158         });
 159         pieces['b'] =
 160           pieces['w'].slice(0, lancerIdx)
 161           .concat(['g'])
 162           .concat(pieces['w'].slice(lancerIdx + 1));
 163         flags += flags;
 164         break;
 165       }
 166
 167       let positions = ArrayFun.range(8);
 168
 169       // Get random squares for bishop and sentry
 170       let randIndex = 2 * randInt(4);
 171       let bishopPos = positions[randIndex];
 172       // The sentry must be on a square of different color
 173       let randIndex_tmp = 2 * randInt(4) + 1;
 174       let sentryPos = positions[randIndex_tmp];
 175       if (c == 'b') {
 176         // Check if white sentry is on the same color as ours.
 177         // If yes: swap bishop and sentry positions.
 178         if ((pieces['w'].indexOf('s') - sentryPos) % 2 == 0)
 179           [bishopPos, sentryPos] = [sentryPos, bishopPos];
 180       }
 181       positions.splice(Math.max(randIndex, randIndex_tmp), 1);
 182       positions.splice(Math.min(randIndex, randIndex_tmp), 1);
 183
 184       // Get random squares for knight and lancer
 185       randIndex = randInt(6);
 186       const knightPos = positions[randIndex];
 187       positions.splice(randIndex, 1);
 188       randIndex = randInt(5);
 189       const lancerPos = positions[randIndex];
 190       positions.splice(randIndex, 1);
 191
 192       // Get random square for queen
 193       randIndex = randInt(4);
 194       const queenPos = positions[randIndex];
 195       positions.splice(randIndex, 1);
 196
 197       // Rook, jailer and king positions are now almost fixed,
 198       // only the ordering rook->jailer or jailer->rook must be decided.
 199       let rookPos = positions[0];
 200       let jailerPos = positions[2];
 201       const kingPos = positions[1];
 202       flags += V.CoordToColumn(rookPos) + V.CoordToColumn(jailerPos);
 203       if (Math.random() < 0.5) [rookPos, jailerPos] = [jailerPos, rookPos];
 204
 205       pieces[c][rookPos] = "r";
 206       pieces[c][knightPos] = "n";
 207       pieces[c][bishopPos] = "b";
 208       pieces[c][queenPos] = "q";
 209       pieces[c][kingPos] = "k";
 210       pieces[c][sentryPos] = "s";
 211       // Lancer faces north for white, and south for black:
 212       pieces[c][lancerPos] = c == 'w' ? 'c' : 'g';
 213       pieces[c][jailerPos] = "j";
 214     }
 215     return (
 216       pieces["b"].join("") +
 217       "/pppppppp/8/8/8/8/PPPPPPPP/" +
 218       pieces["w"].join("").toUpperCase() +
 219       " w 0 " + flags + " - -"
 220     );
 221   }
 222
 223   canTake([x1, y1], [x2, y2]) {
 224     if (this.subTurn == 2)
 225       // Only self captures on this subturn:
 226       return this.getColor(x1, y1) == this.getColor(x2, y2);
 227     return super.canTake([x1, y1], [x2, y2]);
 228   }
 229
 230   // Is piece on square (x,y) immobilized?
 231   isImmobilized([x, y]) {
 232     const color = this.getColor(x, y);
 233     const oppCol = V.GetOppCol(color);
 234     for (let step of V.steps[V.ROOK]) {
 235       const [i, j] = [x + step[0], y + step[1]];
 236       if (
 237         V.OnBoard(i, j) &&
 238         this.board[i][j] != V.EMPTY &&
 239         this.getColor(i, j) == oppCol
 240       ) {
 241         if (this.getPiece(i, j) == V.JAILER) return [i, j];
 242       }
 243     }
 244     return null;
 245   }
 246
 247   // Because of the lancers, getPiece() could be wrong:
 248   // use board[x][y][1] instead (always valid).
 249   getBasicMove([sx, sy], [ex, ey], tr) {
 250     const initColor = this.getColor(sx, sy);
 251     const initPiece = this.board[sx][sy].charAt(1);
 252     let mv = new Move({
 253       appear: [
 254         new PiPo({
 255           x: ex,
 256           y: ey,
 257           c: tr ? tr.c : initColor,
 258           p: tr ? tr.p : initPiece
 259         })
 260       ],
 261       vanish: [
 262         new PiPo({
 263           x: sx,
 264           y: sy,
 265           c: initColor,
 266           p: initPiece
 267         })
 268       ]
 269     });
 270
 271     // The opponent piece disappears if we take it
 272     if (this.board[ex][ey] != V.EMPTY) {
 273       mv.vanish.push(
 274         new PiPo({
 275           x: ex,
 276           y: ey,
 277           c: this.getColor(ex, ey),
 278           p: this.board[ex][ey].charAt(1)
 279         })
 280       );
 281     }
 282
 283     return mv;
 284   }
 285
 286   canIplay(side, [x, y]) {
 287     return (
 288       (this.subTurn == 1 && this.turn == side && this.getColor(x, y) == side) ||
 289       (this.subTurn == 2 && x == this.sentryPos.x && y == this.sentryPos.y)
 290     );
 291   }
 292
 293   getPotentialMovesFrom([x, y]) {
 294     // At subTurn == 2, jailers aren't effective (Jeff K)
 295     const piece = this.getPiece(x, y);
 296     const L = this.sentryPush.length;
 297     if (this.subTurn == 1) {
 298       const jsq = this.isImmobilized([x, y]);
 299       if (!!jsq) {
 300         let moves = [];
 301         // Special pass move if king:
 302         if (piece == V.KING) {
 303           moves.push(
 304             new Move({
 305               appear: [],
 306               vanish: [],
 307               start: { x: x, y: y },
 308               end: { x: jsq[0], y: jsq[1] }
 309             })
 310           );
 311         }
 312         else if (piece == V.LANCER && !!this.sentryPush[L-1]) {
 313           // A pushed lancer next to the jailer: reorient
 314           const color = this.getColor(x, y);
 315           const curDir = this.board[x][y].charAt(1);
 316           Object.keys(V.LANCER_DIRS).forEach(k => {
 317             moves.push(
 318               new Move({
 319                 appear: [{ x: x, y: y, c: color, p: k }],
 320                 vanish: [{ x: x, y: y, c: color, p: curDir }],
 321                 start: { x: x, y: y },
 322                 end: { x: jsq[0], y: jsq[1] }
 323               })
 324             );
 325           });
 326         }
 327         return moves;
 328       }
 329     }
 330     let moves = [];
 331     switch (piece) {
 332       case V.JAILER:
 333         moves = this.getPotentialJailerMoves([x, y]);
 334         break;
 335       case V.SENTRY:
 336         moves = this.getPotentialSentryMoves([x, y]);
 337         break;
 338       case V.LANCER:
 339         moves = this.getPotentialLancerMoves([x, y]);
 340         break;
 341       default:
 342         moves = super.getPotentialMovesFrom([x, y]);
 343         break;
 344     }
 345     if (!!this.sentryPush[L-1]) {
 346       // Delete moves walking back on sentry push path,
 347       // only if not a pawn, and the piece is the pushed one.
 348       const pl = this.sentryPush[L-1].length;
 349       const finalPushedSq = this.sentryPush[L-1][pl-1];
 350       moves = moves.filter(m => {
 351         if (
 352           m.vanish[0].p != V.PAWN &&
 353           m.start.x == finalPushedSq.x && m.start.y == finalPushedSq.y &&
 354           this.sentryPush[L-1].some(sq => sq.x == m.end.x && sq.y == m.end.y)
 355         ) {
 356           return false;
 357         }
 358         return true;
 359       });
 360     } else if (this.subTurn == 2) {
 361       // Put back the sentinel on board:
 362       const color = this.turn;
 363       moves.forEach(m => {
 364         m.appear.push({x: x, y: y, p: V.SENTRY, c: color});
 365       });
 366     }
 367     return moves;
 368   }
 369
 370   getPotentialPawnMoves([x, y]) {
 371     const color = this.getColor(x, y);
 372     let moves = [];
 373     const [sizeX, sizeY] = [V.size.x, V.size.y];
 374     let shiftX = (color == "w" ? -1 : 1);
 375     if (this.subTurn == 2) shiftX *= -1;
 376     const firstRank = color == "w" ? sizeX - 1 : 0;
 377     const startRank = color == "w" ? sizeX - 2 : 1;
 378     const lastRank = color == "w" ? 0 : sizeX - 1;
 379
 380     // Pawns might be pushed on 1st rank and attempt to move again:
 381     if (!V.OnBoard(x + shiftX, y)) return [];
 382
 383     const finalPieces =
 384       // A push cannot put a pawn on last rank (it goes backward)
 385       x + shiftX == lastRank
 386         ? Object.keys(V.LANCER_DIRS).concat(
 387           [V.ROOK, V.KNIGHT, V.BISHOP, V.QUEEN, V.SENTRY, V.JAILER])
 388         : [V.PAWN];
 389     if (this.board[x + shiftX][y] == V.EMPTY) {
 390       // One square forward
 391       for (let piece of finalPieces) {
 392         moves.push(
 393           this.getBasicMove([x, y], [x + shiftX, y], {
 394             c: color,
 395             p: piece
 396           })
 397         );
 398       }
 399       if (
 400         // 2-squares jumps forbidden if pawn push
 401         this.subTurn == 1 &&
 402         [startRank, firstRank].includes(x) &&
 403         this.board[x + 2 * shiftX][y] == V.EMPTY
 404       ) {
 405         // Two squares jump
 406         moves.push(this.getBasicMove([x, y], [x + 2 * shiftX, y]));
 407       }
 408     }
 409     // Captures
 410     for (let shiftY of [-1, 1]) {
 411       if (
 412         y + shiftY >= 0 &&
 413         y + shiftY < sizeY &&
 414         this.board[x + shiftX][y + shiftY] != V.EMPTY &&
 415         this.canTake([x, y], [x + shiftX, y + shiftY])
 416       ) {
 417         for (let piece of finalPieces) {
 418           moves.push(
 419             this.getBasicMove([x, y], [x + shiftX, y + shiftY], {
 420               c: color,
 421               p: piece
 422             })
 423           );
 424         }
 425       }
 426     }
 427
 428     // En passant: only on subTurn == 1
 429     const Lep = this.epSquares.length;
 430     const epSquare = this.epSquares[Lep - 1];
 431     if (
 432       this.subTurn == 1 &&
 433       !!epSquare &&
 434       epSquare.x == x + shiftX &&
 435       Math.abs(epSquare.y - y) == 1
 436     ) {
 437       let enpassantMove = this.getBasicMove([x, y], [epSquare.x, epSquare.y]);
 438       enpassantMove.vanish.push({
 439         x: x,
 440         y: epSquare.y,
 441         p: "p",
 442         c: this.getColor(x, epSquare.y)
 443       });
 444       moves.push(enpassantMove);
 445     }
 446
 447     return moves;
 448   }
 449
 450   // Obtain all lancer moves in "step" direction
 451   getPotentialLancerMoves_aux([x, y], step, tr) {
 452     let moves = [];
 453     // Add all moves to vacant squares until opponent is met:
 454     const color = this.getColor(x, y);
 455     const oppCol =
 456       this.subTurn == 1
 457         ? V.GetOppCol(color)
 458         // at subTurn == 2, consider own pieces as opponent
 459         : color;
 460     let sq = [x + step[0], y + step[1]];
 461     while (V.OnBoard(sq[0], sq[1]) && this.getColor(sq[0], sq[1]) != oppCol) {
 462       if (this.board[sq[0]][sq[1]] == V.EMPTY)
 463         moves.push(this.getBasicMove([x, y], sq, tr));
 464       sq[0] += step[0];
 465       sq[1] += step[1];
 466     }
 467     if (V.OnBoard(sq[0], sq[1]))
 468       // Add capturing move
 469       moves.push(this.getBasicMove([x, y], sq, tr));
 470     return moves;
 471   }
 472
 473   getPotentialLancerMoves([x, y]) {
 474     let moves = [];
 475     // Add all lancer possible orientations, similar to pawn promotions.
 476     // Except if just after a push: allow all movements from init square then
 477     const L = this.sentryPush.length;
 478     const color = this.getColor(x, y);
 479     if (!!this.sentryPush[L-1]) {
 480       // Maybe I was pushed
 481       const pl = this.sentryPush[L-1].length;
 482       if (
 483         this.sentryPush[L-1][pl-1].x == x &&
 484         this.sentryPush[L-1][pl-1].y == y
 485       ) {
 486         // I was pushed: allow all directions (for this move only), but
 487         // do not change direction after moving, *except* if I keep the
 488         // same orientation in which I was pushed.
 489         const curDir = V.LANCER_DIRS[this.board[x][y].charAt(1)];
 490         Object.values(V.LANCER_DIRS).forEach(step => {
 491           const dirCode = Object.keys(V.LANCER_DIRS).find(k => {
 492             return (
 493               V.LANCER_DIRS[k][0] == step[0] &&
 494               V.LANCER_DIRS[k][1] == step[1]
 495             );
 496           });
 497           const dirMoves =
 498             this.getPotentialLancerMoves_aux(
 499               [x, y],
 500               step,
 501               { p: dirCode, c: color }
 502             );
 503           if (curDir[0] == step[0] && curDir[1] == step[1]) {
 504             // Keeping same orientation: can choose after
 505             let chooseMoves = [];
 506             dirMoves.forEach(m => {
 507               Object.keys(V.LANCER_DIRS).forEach(k => {
 508                 let mk = JSON.parse(JSON.stringify(m));
 509                 mk.appear[0].p = k;
 510                 moves.push(mk);
 511               });
 512             });
 513             Array.prototype.push.apply(moves, chooseMoves);
 514           } else Array.prototype.push.apply(moves, dirMoves);
 515         });
 516         return moves;
 517       }
 518     }
 519     // I wasn't pushed: standard lancer move
 520     const dirCode = this.board[x][y][1];
 521     const monodirMoves =
 522       this.getPotentialLancerMoves_aux([x, y], V.LANCER_DIRS[dirCode]);
 523     // Add all possible orientations aftermove except if I'm being pushed
 524     if (this.subTurn == 1) {
 525       monodirMoves.forEach(m => {
 526         Object.keys(V.LANCER_DIRS).forEach(k => {
 527           let mk = JSON.parse(JSON.stringify(m));
 528           mk.appear[0].p = k;
 529           moves.push(mk);
 530         });
 531       });
 532       return moves;
 533     } else {
 534       // I'm pushed: add potential nudges
 535       let potentialNudges = [];
 536       for (let step of V.steps[V.ROOK].concat(V.steps[V.BISHOP])) {
 537         if (
 538           V.OnBoard(x + step[0], y + step[1]) &&
 539           this.board[x + step[0]][y + step[1]] == V.EMPTY
 540         ) {
 541           const newDirCode = Object.keys(V.LANCER_DIRS).find(k => {
 542             const codeStep = V.LANCER_DIRS[k];
 543             return (codeStep[0] == step[0] && codeStep[1] == step[1]);
 544           });
 545           potentialNudges.push(
 546             this.getBasicMove(
 547               [x, y],
 548               [x + step[0], y + step[1]],
 549               { c: color, p: newDirCode }
 550             )
 551           );
 552         }
 553       }
 554       return monodirMoves.concat(potentialNudges);
 555     }
 556   }
 557
 558   getPotentialSentryMoves([x, y]) {
 559     // The sentry moves a priori like a bishop:
 560     let moves = super.getPotentialBishopMoves([x, y]);
 561     // ...but captures are replaced by special move, if and only if
 562     // "captured" piece can move now, considered as the capturer unit.
 563     // --> except is subTurn == 2, in this case I don't push anything.
 564     if (this.subTurn == 2) return moves.filter(m => m.vanish.length == 1);
 565     moves.forEach(m => {
 566       if (m.vanish.length == 2) {
 567         // Temporarily cancel the sentry capture:
 568         m.appear.pop();
 569         m.vanish.pop();
 570       }
 571     });
 572     const color = this.getColor(x, y);
 573     const fMoves = moves.filter(m => {
 574       // Can the pushed unit make any move? ...resulting in a non-self-check?
 575       if (m.appear.length == 0) {
 576         let res = false;
 577         this.play(m);
 578         let moves2 = this.getPotentialMovesFrom([m.end.x, m.end.y]);
 579         for (let m2 of moves2) {
 580           this.play(m2);
 581           res = !this.underCheck(color);
 582           this.undo(m2);
 583           if (res) break;
 584         }
 585         this.undo(m);
 586         return res;
 587       }
 588       return true;
 589     });
 590     return fMoves;
 591   }
 592
 593   getPotentialJailerMoves([x, y]) {
 594     return super.getPotentialRookMoves([x, y]).filter(m => {
 595       // Remove jailer captures
 596       return m.vanish[0].p != V.JAILER || m.vanish.length == 1;
 597     });
 598   }
 599
 600   getPotentialKingMoves(sq) {
 601     const moves = this.getSlideNJumpMoves(
 602       sq,
 603       V.steps[V.ROOK].concat(V.steps[V.BISHOP]),
 604       "oneStep"
 605     );
 606     return (
 607       this.subTurn == 1
 608         ? moves.concat(this.getCastleMoves(sq))
 609         : moves
 610     );
 611   }
 612
 613   atLeastOneMove() {
 614     // If in second-half of a move, we already know that a move is possible
 615     if (this.subTurn == 2) return true;
 616     return super.atLeastOneMove();
 617   }
 618
 619   filterValid(moves) {
 620     if (moves.length == 0) return [];
 621     const basicFilter = (m, c) => {
 622       this.play(m);
 623       const res = !this.underCheck(c);
 624       this.undo(m);
 625       return res;
 626     };
 627     // Disable check tests for sentry pushes,
 628     // because in this case the move isn't finished
 629     let movesWithoutSentryPushes = [];
 630     let movesWithSentryPushes = [];
 631     moves.forEach(m => {
 632       // Second condition below for special king "pass" moves
 633       if (m.appear.length > 0 || m.vanish.length == 0)
 634         movesWithoutSentryPushes.push(m);
 635       else movesWithSentryPushes.push(m);
 636     });
 637     const color = this.turn;
 638     const oppCol = V.GetOppCol(color);
 639     const filteredMoves =
 640       movesWithoutSentryPushes.filter(m => basicFilter(m, color));
 641     // If at least one full move made, everything is allowed.
 642     // Else: forbid checks and captures.
 643     return (
 644       this.movesCount >= 2
 645         ? filteredMoves
 646         : filteredMoves.filter(m => {
 647           return (m.vanish.length <= 1 && basicFilter(m, oppCol));
 648         })
 649     ).concat(movesWithSentryPushes);
 650   }
 651
 652   getAllValidMoves() {
 653     if (this.subTurn == 1) return super.getAllValidMoves();
 654     // Sentry push:
 655     const sentrySq = [this.sentryPos.x, this.sentryPos.y];
 656     return this.filterValid(this.getPotentialMovesFrom(sentrySq));
 657   }
 658
 659   prePlay(move) {
 660     if (move.appear.length == 0 && move.vanish.length == 1)
 661       // The sentry is about to push a piece: subTurn goes from 1 to 2
 662       this.sentryPos = { x: move.end.x, y: move.end.y };
 663     if (this.subTurn == 2 && move.vanish[0].p != V.PAWN) {
 664       // A piece is pushed: forbid array of squares between start and end
 665       // of move, included (except if it's a pawn)
 666       let squares = [];
 667       if ([V.KNIGHT,V.KING].includes(move.vanish[0].p))
 668         // short-range pieces: just forbid initial square
 669         squares.push({ x: move.start.x, y: move.start.y });
 670       else {
 671         const deltaX = move.end.x - move.start.x;
 672         const deltaY = move.end.y - move.start.y;
 673         const step = [
 674           deltaX / Math.abs(deltaX) || 0,
 675           deltaY / Math.abs(deltaY) || 0
 676         ];
 677         for (
 678           let sq = {x: move.start.x, y: move.start.y};
 679           sq.x != move.end.x || sq.y != move.end.y;
 680           sq.x += step[0], sq.y += step[1]
 681         ) {
 682           squares.push({ x: sq.x, y: sq.y });
 683         }
 684       }
 685       // Add end square as well, to know if I was pushed (useful for lancers)
 686       squares.push({ x: move.end.x, y: move.end.y });
 687       this.sentryPush.push(squares);
 688     } else this.sentryPush.push(null);
 689   }
 690
 691   play(move) {
 692     this.prePlay(move);
 693     move.flags = JSON.stringify(this.aggregateFlags());
 694     this.epSquares.push(this.getEpSquare(move));
 695     V.PlayOnBoard(this.board, move);
 696     // Is it a sentry push? (useful for undo)
 697     move.sentryPush = (this.subTurn == 2);
 698     if (this.subTurn == 1) this.movesCount++;
 699     if (move.appear.length == 0 && move.vanish.length == 1) this.subTurn = 2;
 700     else {
 701       // Turn changes only if not a sentry "pre-push"
 702       this.turn = V.GetOppCol(this.turn);
 703       this.subTurn = 1;
 704     }
 705     this.postPlay(move);
 706   }
 707
 708   postPlay(move) {
 709     if (move.vanish.length == 0 || this.subTurn == 2)
 710       // Special pass move of the king, or sentry pre-push: nothing to update
 711       return;
 712     const c = move.vanish[0].c;
 713     const piece = move.vanish[0].p;
 714     const firstRank = c == "w" ? V.size.x - 1 : 0;
 715
 716     if (piece == V.KING) {
 717       this.kingPos[c][0] = move.appear[0].x;
 718       this.kingPos[c][1] = move.appear[0].y;
 719       this.castleFlags[c] = [V.size.y, V.size.y];
 720       return;
 721     }
 722     // Update castling flags if rooks are moved
 723     const oppCol = V.GetOppCol(c);
 724     const oppFirstRank = V.size.x - 1 - firstRank;
 725     if (
 726       move.start.x == firstRank && //our rook moves?
 727       this.castleFlags[c].includes(move.start.y)
 728     ) {
 729       const flagIdx = (move.start.y == this.castleFlags[c][0] ? 0 : 1);
 730       this.castleFlags[c][flagIdx] = V.size.y;
 731     } else if (
 732       move.end.x == oppFirstRank && //we took opponent rook?
 733       this.castleFlags[oppCol].includes(move.end.y)
 734     ) {
 735       const flagIdx = (move.end.y == this.castleFlags[oppCol][0] ? 0 : 1);
 736       this.castleFlags[oppCol][flagIdx] = V.size.y;
 737     }
 738   }
 739
 740   undo(move) {
 741     this.epSquares.pop();
 742     this.disaggregateFlags(JSON.parse(move.flags));
 743     V.UndoOnBoard(this.board, move);
 744     // Decrement movesCount except if the move is a sentry push
 745     if (!move.sentryPush) this.movesCount--;
 746     if (this.subTurn == 2) this.subTurn = 1;
 747     else {
 748       this.turn = V.GetOppCol(this.turn);
 749       if (move.sentryPush) this.subTurn = 2;
 750     }
 751     this.postUndo(move);
 752   }
 753
 754   postUndo(move) {
 755     super.postUndo(move);
 756     this.sentryPush.pop();
 757   }
 758
 759   isAttacked(sq, color) {
 760     return (
 761       super.isAttacked(sq, color) ||
 762       this.isAttackedByLancer(sq, color) ||
 763       this.isAttackedBySentry(sq, color)
 764     );
 765   }
 766
 767   isAttackedBySlideNJump([x, y], color, piece, steps, oneStep) {
 768     for (let step of steps) {
 769       let rx = x + step[0],
 770           ry = y + step[1];
 771       while (V.OnBoard(rx, ry) && this.board[rx][ry] == V.EMPTY && !oneStep) {
 772         rx += step[0];
 773         ry += step[1];
 774       }
 775       if (
 776         V.OnBoard(rx, ry) &&
 777         this.getPiece(rx, ry) == piece &&
 778         this.getColor(rx, ry) == color &&
 779         !this.isImmobilized([rx, ry])
 780       ) {
 781         return true;
 782       }
 783     }
 784     return false;
 785   }
 786
 787   isAttackedByPawn([x, y], color) {
 788     const pawnShift = (color == "w" ? 1 : -1);
 789     if (x + pawnShift >= 0 && x + pawnShift < V.size.x) {
 790       for (let i of [-1, 1]) {
 791         if (
 792           y + i >= 0 &&
 793           y + i < V.size.y &&
 794           this.getPiece(x + pawnShift, y + i) == V.PAWN &&
 795           this.getColor(x + pawnShift, y + i) == color &&
 796           !this.isImmobilized([x + pawnShift, y + i])
 797         ) {
 798           return true;
 799         }
 800       }
 801     }
 802     return false;
 803   }
 804
 805   isAttackedByLancer([x, y], color) {
 806     for (let step of V.steps[V.ROOK].concat(V.steps[V.BISHOP])) {
 807       // If in this direction there are only enemy pieces and empty squares,
 808       // and we meet a lancer: can he reach us?
 809       // NOTE: do not stop at first lancer, there might be several!
 810       let coord = { x: x + step[0], y: y + step[1] };
 811       let lancerPos = [];
 812       while (
 813         V.OnBoard(coord.x, coord.y) &&
 814         (
 815           this.board[coord.x][coord.y] == V.EMPTY ||
 816           this.getColor(coord.x, coord.y) == color
 817         )
 818       ) {
 819         if (
 820           this.getPiece(coord.x, coord.y) == V.LANCER &&
 821           !this.isImmobilized([coord.x, coord.y])
 822         ) {
 823           lancerPos.push({x: coord.x, y: coord.y});
 824         }
 825         coord.x += step[0];
 826         coord.y += step[1];
 827       }
 828       for (let xy of lancerPos) {
 829         const dir = V.LANCER_DIRS[this.board[xy.x][xy.y].charAt(1)];
 830         if (dir[0] == -step[0] && dir[1] == -step[1]) return true;
 831       }
 832     }
 833     return false;
 834   }
 835
 836   // Helper to check sentries attacks:
 837   selfAttack([x1, y1], [x2, y2]) {
 838     const color = this.getColor(x1, y1);
 839     const sliderAttack = (allowedSteps, lancer) => {
 840       const deltaX = x2 - x1,
 841             absDeltaX = Math.abs(deltaX);
 842       const deltaY = y2 - y1,
 843             absDeltaY = Math.abs(deltaY);
 844       const step = [ deltaX / absDeltaX || 0, deltaY / absDeltaY || 0 ];
 845       if (
 846         // Check that the step is a priori valid:
 847         (absDeltaX != absDeltaY && deltaX != 0 && deltaY != 0) ||
 848         allowedSteps.every(st => st[0] != step[0] || st[1] != step[1])
 849       ) {
 850         return false;
 851       }
 852       let sq = [ x1 + step[0], y1 + step[1] ];
 853       while (sq[0] != x2 || sq[1] != y2) {
 854         if (
 855           // NOTE: no need to check OnBoard in this special case
 856           (!lancer && this.board[sq[0]][sq[1]] != V.EMPTY) ||
 857           (!!lancer && this.getColor(sq[0], sq[1]) != color)
 858         ) {
 859           return false;
 860         }
 861         sq[0] += step[0];
 862         sq[1] += step[1];
 863       }
 864       return true;
 865     };
 866     switch (this.getPiece(x1, y1)) {
 867       case V.PAWN: {
 868         // Pushed pawns move as enemy pawns
 869         const shift = (color == 'w' ? 1 : -1);
 870         return (x1 + shift == x2 && Math.abs(y1 - y2) == 1);
 871       }
 872       case V.KNIGHT: {
 873         const deltaX = Math.abs(x1 - x2);
 874         const deltaY = Math.abs(y1 - y2);
 875         return (
 876           deltaX + deltaY == 3 &&
 877           [1, 2].includes(deltaX) &&
 878           [1, 2].includes(deltaY)
 879         );
 880       }
 881       case V.ROOK:
 882         return sliderAttack(V.steps[V.ROOK]);
 883       case V.BISHOP:
 884         return sliderAttack(V.steps[V.BISHOP]);
 885       case V.QUEEN:
 886         return sliderAttack(V.steps[V.ROOK].concat(V.steps[V.BISHOP]));
 887       case V.LANCER: {
 888         // Special case: as long as no enemy units stands in-between, it attacks
 889         // (if it points toward the king).
 890         const allowedStep = V.LANCER_DIRS[this.board[x1][y1].charAt(1)];
 891         return sliderAttack([allowedStep], "lancer");
 892       }
 893       // No sentries or jailer tests: they cannot self-capture
 894     }
 895     return false;
 896   }
 897
 898   isAttackedBySentry([x, y], color) {
 899     // Attacked by sentry means it can self-take our king.
 900     // Just check diagonals of enemy sentry(ies), and if it reaches
 901     // one of our pieces: can I self-take?
 902     const myColor = V.GetOppCol(color);
 903     let candidates = [];
 904     for (let i=0; i<V.size.x; i++) {
 905       for (let j=0; j<V.size.y; j++) {
 906         if (
 907           this.getPiece(i,j) == V.SENTRY &&
 908           this.getColor(i,j) == color &&
 909           !this.isImmobilized([i, j])
 910         ) {
 911           for (let step of V.steps[V.BISHOP]) {
 912             let sq = [ i + step[0], j + step[1] ];
 913             while (
 914               V.OnBoard(sq[0], sq[1]) &&
 915               this.board[sq[0]][sq[1]] == V.EMPTY
 916             ) {
 917               sq[0] += step[0];
 918               sq[1] += step[1];
 919             }
 920             if (
 921               V.OnBoard(sq[0], sq[1]) &&
 922               this.getColor(sq[0], sq[1]) == myColor
 923             ) {
 924               candidates.push([ sq[0], sq[1] ]);
 925             }
 926           }
 927         }
 928       }
 929     }
 930     for (let c of candidates)
 931       if (this.selfAttack(c, [x, y])) return true;
 932     return false;
 933   }
 934
 935   // Jailer doesn't capture or give check
 936
 937   static get VALUES() {
 938     return Object.assign(
 939       { l: 4.8, s: 2.8, j: 3.8 }, //Jeff K. estimations
 940       ChessRules.VALUES
 941     );
 942   }
 943
 944   getComputerMove() {
 945     const maxeval = V.INFINITY;
 946     const color = this.turn;
 947     let moves1 = this.getAllValidMoves();
 948
 949     if (moves1.length == 0)
 950       // TODO: this situation should not happen
 951       return null;
 952
 953     const setEval = (move, next) => {
 954       const score = this.getCurrentScore();
 955       const curEval = move.eval;
 956       if (score != "*") {
 957         move.eval =
 958           score == "1/2"
 959             ? 0
 960             : (score == "1-0" ? 1 : -1) * maxeval;
 961       } else move.eval = this.evalPosition();
 962       if (
 963         // "next" is defined after sentry pushes
 964         !!next && (
 965           !curEval ||
 966           color == 'w' && move.eval > curEval ||
 967           color == 'b' && move.eval < curEval
 968         )
 969       ) {
 970         move.second = next;
 971       }
 972     };
 973
 974     // Just search_depth == 1 (because of sentries. TODO: can do better...)
 975     moves1.forEach(m1 => {
 976       this.play(m1);
 977       if (this.subTurn == 1) setEval(m1);
 978       else {
 979         // Need to play every pushes and count:
 980         const moves2 = this.getAllValidMoves();
 981         moves2.forEach(m2 => {
 982           this.play(m2);
 983           setEval(m1, m2);
 984           this.undo(m2);
 985         });
 986       }
 987       this.undo(m1);
 988     });
 989
 990     moves1.sort((a, b) => {
 991       return (color == "w" ? 1 : -1) * (b.eval - a.eval);
 992     });
 993     let candidates = [0];
 994     for (let j = 1; j < moves1.length && moves1[j].eval == moves1[0].eval; j++)
 995       candidates.push(j);
 996     const choice = moves1[candidates[randInt(candidates.length)]];
 997     return (!choice.second ? choice : [choice, choice.second]);
 998   }
 999
1000   // For moves notation:
1001   static get LANCER_DIRNAMES() {
1002     return {
1003       'c': "N",
1004       'd': "NE",
1005       'e': "E",
1006       'f': "SE",
1007       'g': "S",
1008       'h': "SW",
1009       'm': "W",
1010       'o': "NW"
1011     };
1012   }
1013
1014   getNotation(move) {
1015     // Special case "king takes jailer" is a pass move
1016     if (move.appear.length == 0 && move.vanish.length == 0) return "pass";
1017     let notation = undefined;
1018     if (this.subTurn == 2) {
1019       // Do not consider appear[1] (sentry) for sentry pushes
1020       const simpleMove = {
1021         appear: [move.appear[0]],
1022         vanish: move.vanish,
1023         start: move.start,
1024         end: move.end
1025       };
1026       notation = super.getNotation(simpleMove);
1027     } else notation = super.getNotation(move);
1028     if (Object.keys(V.LANCER_DIRNAMES).includes(move.vanish[0].p))
1029       // Lancer: add direction info
1030       notation += "=" + V.LANCER_DIRNAMES[move.appear[0].p];
1031     return notation;
1032   }
1033 };