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(m, orientation) {
  87     return (
  88       this.getPpath(
  89         m.appear[0].c + m.appear[0].p,
  90         null,
  91         null,
  92         orientation
  93       )
  94     );
  95   }
  96
  97   static ParseFen(fen) {
  98     const fenParts = fen.split(" ");
  99     return Object.assign(
 100       ChessRules.ParseFen(fen),
 101       { sentrypush: fenParts[5] }
 102     );
 103   }
 104
 105   static IsGoodFen(fen) {
 106     if (!ChessRules.IsGoodFen(fen)) return false;
 107     const fenParsed = V.ParseFen(fen);
 108     // 5) Check sentry push (if any)
 109     if (
 110       fenParsed.sentrypush != "-" &&
 111       !fenParsed.sentrypush.match(/^([a-h][1-8],?)+$/)
 112     ) {
 113       return false;
 114     }
 115     return true;
 116   }
 117
 118   getFen() {
 119     return super.getFen() + " " + this.getSentrypushFen();
 120   }
 121
 122   getFenForRepeat() {
 123     return super.getFenForRepeat() + "_" + this.getSentrypushFen();
 124   }
 125
 126   getSentrypushFen() {
 127     const L = this.sentryPush.length;
 128     if (!this.sentryPush[L-1]) return "-";
 129     let res = "";
 130     this.sentryPush[L-1].forEach(coords =>
 131       res += V.CoordsToSquare(coords) + ",");
 132     return res.slice(0, -1);
 133   }
 134
 135   setOtherVariables(fen) {
 136     super.setOtherVariables(fen);
 137     // subTurn == 2 only when a sentry moved, and is about to push something
 138     this.subTurn = 1;
 139     // Sentry position just after a "capture" (subTurn from 1 to 2)
 140     this.sentryPos = null;
 141     // Stack pieces' forbidden squares after a sentry move at each turn
 142     const parsedFen = V.ParseFen(fen);
 143     if (parsedFen.sentrypush == "-") this.sentryPush = [null];
 144     else {
 145       this.sentryPush = [
 146         parsedFen.sentrypush.split(",").map(sq => {
 147           return V.SquareToCoords(sq);
 148         })
 149       ];
 150     }
 151   }
 152
 153   static GenRandInitFen(randomness) {
 154     if (randomness == 0)
 155       // Deterministic:
 156       return "jfsqkbnr/pppppppp/8/8/8/8/PPPPPPPP/JDSQKBNR w 0 ahah - -";
 157
 158     let pieces = { w: new Array(8), b: new Array(8) };
 159     let flags = "";
 160     // Shuffle pieces on first (and last rank if randomness == 2)
 161     for (let c of ["w", "b"]) {
 162       if (c == 'b' && randomness == 1) {
 163         const lancerIdx = pieces['w'].findIndex(p => {
 164           return Object.keys(V.LANCER_DIRS).includes(p);
 165         });
 166         pieces['b'] =
 167           pieces['w'].slice(0, lancerIdx)
 168           .concat(['g'])
 169           .concat(pieces['w'].slice(lancerIdx + 1));
 170         flags += flags;
 171         break;
 172       }
 173
 174       let positions = ArrayFun.range(8);
 175
 176       // Get random squares for bishop and sentry
 177       let randIndex = 2 * randInt(4);
 178       let bishopPos = positions[randIndex];
 179       // The sentry must be on a square of different color
 180       let randIndex_tmp = 2 * randInt(4) + 1;
 181       let sentryPos = positions[randIndex_tmp];
 182       if (c == 'b') {
 183         // Check if white sentry is on the same color as ours.
 184         // If yes: swap bishop and sentry positions.
 185         // NOTE: test % 2 == 1 because there are 7 slashes.
 186         if ((pieces['w'].indexOf('s') - sentryPos) % 2 == 1)
 187           [bishopPos, sentryPos] = [sentryPos, bishopPos];
 188       }
 189       positions.splice(Math.max(randIndex, randIndex_tmp), 1);
 190       positions.splice(Math.min(randIndex, randIndex_tmp), 1);
 191
 192       // Get random squares for knight and lancer
 193       randIndex = randInt(6);
 194       const knightPos = positions[randIndex];
 195       positions.splice(randIndex, 1);
 196       randIndex = randInt(5);
 197       const lancerPos = positions[randIndex];
 198       positions.splice(randIndex, 1);
 199
 200       // Get random square for queen
 201       randIndex = randInt(4);
 202       const queenPos = positions[randIndex];
 203       positions.splice(randIndex, 1);
 204
 205       // Rook, jailer and king positions are now almost fixed,
 206       // only the ordering rook->jailer or jailer->rook must be decided.
 207       let rookPos = positions[0];
 208       let jailerPos = positions[2];
 209       const kingPos = positions[1];
 210       flags += V.CoordToColumn(rookPos) + V.CoordToColumn(jailerPos);
 211       if (Math.random() < 0.5) [rookPos, jailerPos] = [jailerPos, rookPos];
 212
 213       pieces[c][rookPos] = "r";
 214       pieces[c][knightPos] = "n";
 215       pieces[c][bishopPos] = "b";
 216       pieces[c][queenPos] = "q";
 217       pieces[c][kingPos] = "k";
 218       pieces[c][sentryPos] = "s";
 219       // Lancer faces north for white, and south for black:
 220       pieces[c][lancerPos] = c == 'w' ? 'c' : 'g';
 221       pieces[c][jailerPos] = "j";
 222     }
 223     return (
 224       pieces["b"].join("") +
 225       "/pppppppp/8/8/8/8/PPPPPPPP/" +
 226       pieces["w"].join("").toUpperCase() +
 227       " w 0 " + flags + " - -"
 228     );
 229   }
 230
 231   canTake([x1, y1], [x2, y2]) {
 232     if (this.subTurn == 2)
 233       // Only self captures on this subturn:
 234       return this.getColor(x1, y1) == this.getColor(x2, y2);
 235     return super.canTake([x1, y1], [x2, y2]);
 236   }
 237
 238   // Is piece on square (x,y) immobilized?
 239   isImmobilized([x, y]) {
 240     const color = this.getColor(x, y);
 241     const oppCol = V.GetOppCol(color);
 242     for (let step of V.steps[V.ROOK]) {
 243       const [i, j] = [x + step[0], y + step[1]];
 244       if (
 245         V.OnBoard(i, j) &&
 246         this.board[i][j] != V.EMPTY &&
 247         this.getColor(i, j) == oppCol
 248       ) {
 249         if (this.getPiece(i, j) == V.JAILER) return [i, j];
 250       }
 251     }
 252     return null;
 253   }
 254
 255   // Because of the lancers, getPiece() could be wrong:
 256   // use board[x][y][1] instead (always valid).
 257   getBasicMove([sx, sy], [ex, ey], tr) {
 258     const initColor = this.getColor(sx, sy);
 259     const initPiece = this.board[sx][sy].charAt(1);
 260     let mv = new Move({
 261       appear: [
 262         new PiPo({
 263           x: ex,
 264           y: ey,
 265           c: tr ? tr.c : initColor,
 266           p: tr ? tr.p : initPiece
 267         })
 268       ],
 269       vanish: [
 270         new PiPo({
 271           x: sx,
 272           y: sy,
 273           c: initColor,
 274           p: initPiece
 275         })
 276       ]
 277     });
 278
 279     // The opponent piece disappears if we take it
 280     if (this.board[ex][ey] != V.EMPTY) {
 281       mv.vanish.push(
 282         new PiPo({
 283           x: ex,
 284           y: ey,
 285           c: this.getColor(ex, ey),
 286           p: this.board[ex][ey].charAt(1)
 287         })
 288       );
 289     }
 290
 291     return mv;
 292   }
 293
 294   canIplay(side, [x, y]) {
 295     return (
 296       (this.subTurn == 1 && this.turn == side && this.getColor(x, y) == side) ||
 297       (this.subTurn == 2 && x == this.sentryPos.x && y == this.sentryPos.y)
 298     );
 299   }
 300
 301   getPotentialMovesFrom([x, y]) {
 302     // At subTurn == 2, jailers aren't effective (Jeff K)
 303     const piece = this.getPiece(x, y);
 304     const L = this.sentryPush.length;
 305     if (this.subTurn == 1) {
 306       const jsq = this.isImmobilized([x, y]);
 307       if (!!jsq) {
 308         let moves = [];
 309         // Special pass move if king:
 310         if (piece == V.KING) {
 311           moves.push(
 312             new Move({
 313               appear: [],
 314               vanish: [],
 315               start: { x: x, y: y },
 316               end: { x: jsq[0], y: jsq[1] }
 317             })
 318           );
 319         }
 320         else if (piece == V.LANCER && !!this.sentryPush[L-1]) {
 321           // A pushed lancer next to the jailer: reorient
 322           const color = this.getColor(x, y);
 323           const curDir = this.board[x][y].charAt(1);
 324           Object.keys(V.LANCER_DIRS).forEach(k => {
 325             moves.push(
 326               new Move({
 327                 appear: [{ x: x, y: y, c: color, p: k }],
 328                 vanish: [{ x: x, y: y, c: color, p: curDir }],
 329                 start: { x: x, y: y },
 330                 end: { x: jsq[0], y: jsq[1] }
 331               })
 332             );
 333           });
 334         }
 335         return moves;
 336       }
 337     }
 338     let moves = [];
 339     switch (piece) {
 340       case V.JAILER:
 341         moves = this.getPotentialJailerMoves([x, y]);
 342         break;
 343       case V.SENTRY:
 344         moves = this.getPotentialSentryMoves([x, y]);
 345         break;
 346       case V.LANCER:
 347         moves = this.getPotentialLancerMoves([x, y]);
 348         break;
 349       default:
 350         moves = super.getPotentialMovesFrom([x, y]);
 351         break;
 352     }
 353     if (!!this.sentryPush[L-1]) {
 354       // Delete moves walking back on sentry push path,
 355       // only if not a pawn, and the piece is the pushed one.
 356       const pl = this.sentryPush[L-1].length;
 357       const finalPushedSq = this.sentryPush[L-1][pl-1];
 358       moves = moves.filter(m => {
 359         if (
 360           m.vanish[0].p != V.PAWN &&
 361           m.start.x == finalPushedSq.x && m.start.y == finalPushedSq.y &&
 362           this.sentryPush[L-1].some(sq => sq.x == m.end.x && sq.y == m.end.y)
 363         ) {
 364           return false;
 365         }
 366         return true;
 367       });
 368     } else if (this.subTurn == 2) {
 369       // Put back the sentinel on board:
 370       const color = this.turn;
 371       moves.forEach(m => {
 372         m.appear.push({x: x, y: y, p: V.SENTRY, c: color});
 373       });
 374     }
 375     return moves;
 376   }
 377
 378   getPotentialPawnMoves([x, y]) {
 379     const color = this.getColor(x, y);
 380     let moves = [];
 381     const [sizeX, sizeY] = [V.size.x, V.size.y];
 382     let shiftX = (color == "w" ? -1 : 1);
 383     if (this.subTurn == 2) shiftX *= -1;
 384     const firstRank = color == "w" ? sizeX - 1 : 0;
 385     const startRank = color == "w" ? sizeX - 2 : 1;
 386     const lastRank = color == "w" ? 0 : sizeX - 1;
 387
 388     // Pawns might be pushed on 1st rank and attempt to move again:
 389     if (!V.OnBoard(x + shiftX, y)) return [];
 390
 391     const finalPieces =
 392       // A push cannot put a pawn on last rank (it goes backward)
 393       x + shiftX == lastRank
 394         ? Object.keys(V.LANCER_DIRS).concat(
 395           [V.ROOK, V.KNIGHT, V.BISHOP, V.QUEEN, V.SENTRY, V.JAILER])
 396         : [V.PAWN];
 397     if (this.board[x + shiftX][y] == V.EMPTY) {
 398       // One square forward
 399       for (let piece of finalPieces) {
 400         moves.push(
 401           this.getBasicMove([x, y], [x + shiftX, y], {
 402             c: color,
 403             p: piece
 404           })
 405         );
 406       }
 407       if (
 408         // 2-squares jumps forbidden if pawn push
 409         this.subTurn == 1 &&
 410         [startRank, firstRank].includes(x) &&
 411         this.board[x + 2 * shiftX][y] == V.EMPTY
 412       ) {
 413         // Two squares jump
 414         moves.push(this.getBasicMove([x, y], [x + 2 * shiftX, y]));
 415       }
 416     }
 417     // Captures
 418     for (let shiftY of [-1, 1]) {
 419       if (
 420         y + shiftY >= 0 &&
 421         y + shiftY < sizeY &&
 422         this.board[x + shiftX][y + shiftY] != V.EMPTY &&
 423         this.canTake([x, y], [x + shiftX, y + shiftY])
 424       ) {
 425         for (let piece of finalPieces) {
 426           moves.push(
 427             this.getBasicMove([x, y], [x + shiftX, y + shiftY], {
 428               c: color,
 429               p: piece
 430             })
 431           );
 432         }
 433       }
 434     }
 435
 436     // En passant: only on subTurn == 1
 437     const Lep = this.epSquares.length;
 438     const epSquare = this.epSquares[Lep - 1];
 439     if (
 440       this.subTurn == 1 &&
 441       !!epSquare &&
 442       epSquare.x == x + shiftX &&
 443       Math.abs(epSquare.y - y) == 1
 444     ) {
 445       let enpassantMove = this.getBasicMove([x, y], [epSquare.x, epSquare.y]);
 446       enpassantMove.vanish.push({
 447         x: x,
 448         y: epSquare.y,
 449         p: "p",
 450         c: this.getColor(x, epSquare.y)
 451       });
 452       moves.push(enpassantMove);
 453     }
 454
 455     return moves;
 456   }
 457
 458   // Obtain all lancer moves in "step" direction
 459   getPotentialLancerMoves_aux([x, y], step, tr) {
 460     let moves = [];
 461     // Add all moves to vacant squares until opponent is met:
 462     const color = this.getColor(x, y);
 463     const oppCol =
 464       this.subTurn == 1
 465         ? V.GetOppCol(color)
 466         // at subTurn == 2, consider own pieces as opponent
 467         : color;
 468     let sq = [x + step[0], y + step[1]];
 469     while (V.OnBoard(sq[0], sq[1]) && this.getColor(sq[0], sq[1]) != oppCol) {
 470       if (this.board[sq[0]][sq[1]] == V.EMPTY)
 471         moves.push(this.getBasicMove([x, y], sq, tr));
 472       sq[0] += step[0];
 473       sq[1] += step[1];
 474     }
 475     if (V.OnBoard(sq[0], sq[1]))
 476       // Add capturing move
 477       moves.push(this.getBasicMove([x, y], sq, tr));
 478     return moves;
 479   }
 480
 481   getPotentialLancerMoves([x, y]) {
 482     let moves = [];
 483     // Add all lancer possible orientations, similar to pawn promotions.
 484     // Except if just after a push: allow all movements from init square then
 485     const L = this.sentryPush.length;
 486     const color = this.getColor(x, y);
 487     if (!!this.sentryPush[L-1]) {
 488       // Maybe I was pushed
 489       const pl = this.sentryPush[L-1].length;
 490       if (
 491         this.sentryPush[L-1][pl-1].x == x &&
 492         this.sentryPush[L-1][pl-1].y == y
 493       ) {
 494         // I was pushed: allow all directions (for this move only), but
 495         // do not change direction after moving, *except* if I keep the
 496         // same orientation in which I was pushed.
 497         const curDir = V.LANCER_DIRS[this.board[x][y].charAt(1)];
 498         Object.values(V.LANCER_DIRS).forEach(step => {
 499           const dirCode = Object.keys(V.LANCER_DIRS).find(k => {
 500             return (
 501               V.LANCER_DIRS[k][0] == step[0] &&
 502               V.LANCER_DIRS[k][1] == step[1]
 503             );
 504           });
 505           const dirMoves =
 506             this.getPotentialLancerMoves_aux(
 507               [x, y],
 508               step,
 509               { p: dirCode, c: color }
 510             );
 511           if (curDir[0] == step[0] && curDir[1] == step[1]) {
 512             // Keeping same orientation: can choose after
 513             let chooseMoves = [];
 514             dirMoves.forEach(m => {
 515               Object.keys(V.LANCER_DIRS).forEach(k => {
 516                 let mk = JSON.parse(JSON.stringify(m));
 517                 mk.appear[0].p = k;
 518                 moves.push(mk);
 519               });
 520             });
 521             Array.prototype.push.apply(moves, chooseMoves);
 522           } else Array.prototype.push.apply(moves, dirMoves);
 523         });
 524         return moves;
 525       }
 526     }
 527     // I wasn't pushed: standard lancer move
 528     const dirCode = this.board[x][y][1];
 529     const monodirMoves =
 530       this.getPotentialLancerMoves_aux([x, y], V.LANCER_DIRS[dirCode]);
 531     // Add all possible orientations aftermove except if I'm being pushed
 532     if (this.subTurn == 1) {
 533       monodirMoves.forEach(m => {
 534         Object.keys(V.LANCER_DIRS).forEach(k => {
 535           let mk = JSON.parse(JSON.stringify(m));
 536           mk.appear[0].p = k;
 537           moves.push(mk);
 538         });
 539       });
 540       return moves;
 541     } else {
 542       // I'm pushed: add potential nudges
 543       let potentialNudges = [];
 544       for (let step of V.steps[V.ROOK].concat(V.steps[V.BISHOP])) {
 545         if (
 546           V.OnBoard(x + step[0], y + step[1]) &&
 547           this.board[x + step[0]][y + step[1]] == V.EMPTY
 548         ) {
 549           const newDirCode = Object.keys(V.LANCER_DIRS).find(k => {
 550             const codeStep = V.LANCER_DIRS[k];
 551             return (codeStep[0] == step[0] && codeStep[1] == step[1]);
 552           });
 553           potentialNudges.push(
 554             this.getBasicMove(
 555               [x, y],
 556               [x + step[0], y + step[1]],
 557               { c: color, p: newDirCode }
 558             )
 559           );
 560         }
 561       }
 562       return monodirMoves.concat(potentialNudges);
 563     }
 564   }
 565
 566   getPotentialSentryMoves([x, y]) {
 567     // The sentry moves a priori like a bishop:
 568     let moves = super.getPotentialBishopMoves([x, y]);
 569     // ...but captures are replaced by special move, if and only if
 570     // "captured" piece can move now, considered as the capturer unit.
 571     // --> except is subTurn == 2, in this case I don't push anything.
 572     if (this.subTurn == 2) return moves.filter(m => m.vanish.length == 1);
 573     moves.forEach(m => {
 574       if (m.vanish.length == 2) {
 575         // Temporarily cancel the sentry capture:
 576         m.appear.pop();
 577         m.vanish.pop();
 578       }
 579     });
 580     const color = this.getColor(x, y);
 581     const fMoves = moves.filter(m => {
 582       // Can the pushed unit make any move? ...resulting in a non-self-check?
 583       if (m.appear.length == 0) {
 584         let res = false;
 585         this.play(m);
 586         let moves2 = this.getPotentialMovesFrom([m.end.x, m.end.y]);
 587         for (let m2 of moves2) {
 588           this.play(m2);
 589           res = !this.underCheck(color);
 590           this.undo(m2);
 591           if (res) break;
 592         }
 593         this.undo(m);
 594         return res;
 595       }
 596       return true;
 597     });
 598     return fMoves;
 599   }
 600
 601   getPotentialJailerMoves([x, y]) {
 602     return super.getPotentialRookMoves([x, y]).filter(m => {
 603       // Remove jailer captures
 604       return m.vanish[0].p != V.JAILER || m.vanish.length == 1;
 605     });
 606   }
 607
 608   getPotentialKingMoves(sq) {
 609     const moves = this.getSlideNJumpMoves(
 610       sq,
 611       V.steps[V.ROOK].concat(V.steps[V.BISHOP]),
 612       "oneStep"
 613     );
 614     return (
 615       this.subTurn == 1
 616         ? moves.concat(this.getCastleMoves(sq))
 617         : moves
 618     );
 619   }
 620
 621   atLeastOneMove() {
 622     // If in second-half of a move, we already know that a move is possible
 623     if (this.subTurn == 2) return true;
 624     return super.atLeastOneMove();
 625   }
 626
 627   filterValid(moves) {
 628     if (moves.length == 0) return [];
 629     const basicFilter = (m, c) => {
 630       this.play(m);
 631       const res = !this.underCheck(c);
 632       this.undo(m);
 633       return res;
 634     };
 635     // Disable check tests for sentry pushes,
 636     // because in this case the move isn't finished
 637     let movesWithoutSentryPushes = [];
 638     let movesWithSentryPushes = [];
 639     moves.forEach(m => {
 640       // Second condition below for special king "pass" moves
 641       if (m.appear.length > 0 || m.vanish.length == 0)
 642         movesWithoutSentryPushes.push(m);
 643       else movesWithSentryPushes.push(m);
 644     });
 645     const color = this.turn;
 646     const oppCol = V.GetOppCol(color);
 647     const filteredMoves =
 648       movesWithoutSentryPushes.filter(m => basicFilter(m, color));
 649     // If at least one full move made, everything is allowed.
 650     // Else: forbid checks and captures.
 651     return (
 652       this.movesCount >= 2
 653         ? filteredMoves
 654         : filteredMoves.filter(m => {
 655           return (m.vanish.length <= 1 && basicFilter(m, oppCol));
 656         })
 657     ).concat(movesWithSentryPushes);
 658   }
 659
 660   getAllValidMoves() {
 661     if (this.subTurn == 1) return super.getAllValidMoves();
 662     // Sentry push:
 663     const sentrySq = [this.sentryPos.x, this.sentryPos.y];
 664     return this.filterValid(this.getPotentialMovesFrom(sentrySq));
 665   }
 666
 667   isAttacked(sq, color) {
 668     return (
 669       super.isAttacked(sq, color) ||
 670       this.isAttackedByLancer(sq, color) ||
 671       this.isAttackedBySentry(sq, color)
 672       // The jailer doesn't capture.
 673     );
 674   }
 675
 676   isAttackedBySlideNJump([x, y], color, piece, steps, oneStep) {
 677     for (let step of steps) {
 678       let rx = x + step[0],
 679           ry = y + step[1];
 680       while (V.OnBoard(rx, ry) && this.board[rx][ry] == V.EMPTY && !oneStep) {
 681         rx += step[0];
 682         ry += step[1];
 683       }
 684       if (
 685         V.OnBoard(rx, ry) &&
 686         this.getPiece(rx, ry) == piece &&
 687         this.getColor(rx, ry) == color &&
 688         !this.isImmobilized([rx, ry])
 689       ) {
 690         return true;
 691       }
 692     }
 693     return false;
 694   }
 695
 696   isAttackedByPawn([x, y], color) {
 697     const pawnShift = (color == "w" ? 1 : -1);
 698     if (x + pawnShift >= 0 && x + pawnShift < V.size.x) {
 699       for (let i of [-1, 1]) {
 700         if (
 701           y + i >= 0 &&
 702           y + i < V.size.y &&
 703           this.getPiece(x + pawnShift, y + i) == V.PAWN &&
 704           this.getColor(x + pawnShift, y + i) == color &&
 705           !this.isImmobilized([x + pawnShift, y + i])
 706         ) {
 707           return true;
 708         }
 709       }
 710     }
 711     return false;
 712   }
 713
 714   isAttackedByLancer([x, y], color) {
 715     for (let step of V.steps[V.ROOK].concat(V.steps[V.BISHOP])) {
 716       // If in this direction there are only enemy pieces and empty squares,
 717       // and we meet a lancer: can he reach us?
 718       // NOTE: do not stop at first lancer, there might be several!
 719       let coord = { x: x + step[0], y: y + step[1] };
 720       let lancerPos = [];
 721       while (
 722         V.OnBoard(coord.x, coord.y) &&
 723         (
 724           this.board[coord.x][coord.y] == V.EMPTY ||
 725           this.getColor(coord.x, coord.y) == color
 726         )
 727       ) {
 728         if (
 729           this.getPiece(coord.x, coord.y) == V.LANCER &&
 730           !this.isImmobilized([coord.x, coord.y])
 731         ) {
 732           lancerPos.push({x: coord.x, y: coord.y});
 733         }
 734         coord.x += step[0];
 735         coord.y += step[1];
 736       }
 737       for (let xy of lancerPos) {
 738         const dir = V.LANCER_DIRS[this.board[xy.x][xy.y].charAt(1)];
 739         if (dir[0] == -step[0] && dir[1] == -step[1]) return true;
 740       }
 741     }
 742     return false;
 743   }
 744
 745   // Helper to check sentries attacks:
 746   selfAttack([x1, y1], [x2, y2]) {
 747     const color = this.getColor(x1, y1);
 748     const oppCol = V.GetOppCol(color);
 749     const sliderAttack = (allowedSteps, lancer) => {
 750       const deltaX = x2 - x1,
 751             absDeltaX = Math.abs(deltaX);
 752       const deltaY = y2 - y1,
 753             absDeltaY = Math.abs(deltaY);
 754       const step = [ deltaX / absDeltaX || 0, deltaY / absDeltaY || 0 ];
 755       if (
 756         // Check that the step is a priori valid:
 757         (absDeltaX != absDeltaY && deltaX != 0 && deltaY != 0) ||
 758         allowedSteps.every(st => st[0] != step[0] || st[1] != step[1])
 759       ) {
 760         return false;
 761       }
 762       let sq = [ x1 + step[0], y1 + step[1] ];
 763       while (sq[0] != x2 || sq[1] != y2) {
 764         if (
 765           // NOTE: no need to check OnBoard in this special case
 766           (!lancer && this.board[sq[0]][sq[1]] != V.EMPTY) ||
 767           (!!lancer && this.getColor(sq[0], sq[1]) == oppCol)
 768         ) {
 769           return false;
 770         }
 771         sq[0] += step[0];
 772         sq[1] += step[1];
 773       }
 774       return true;
 775     };
 776     switch (this.getPiece(x1, y1)) {
 777       case V.PAWN: {
 778         // Pushed pawns move as enemy pawns
 779         const shift = (color == 'w' ? 1 : -1);
 780         return (x1 + shift == x2 && Math.abs(y1 - y2) == 1);
 781       }
 782       case V.KNIGHT: {
 783         const deltaX = Math.abs(x1 - x2);
 784         const deltaY = Math.abs(y1 - y2);
 785         return (
 786           deltaX + deltaY == 3 &&
 787           [1, 2].includes(deltaX) &&
 788           [1, 2].includes(deltaY)
 789         );
 790       }
 791       case V.ROOK:
 792         return sliderAttack(V.steps[V.ROOK]);
 793       case V.BISHOP:
 794         return sliderAttack(V.steps[V.BISHOP]);
 795       case V.QUEEN:
 796         return sliderAttack(V.steps[V.ROOK].concat(V.steps[V.BISHOP]));
 797       case V.LANCER: {
 798         // Special case: as long as no enemy units stands in-between, it attacks
 799         // (if it points toward the king).
 800         const allowedStep = V.LANCER_DIRS[this.board[x1][y1].charAt(1)];
 801         return sliderAttack([allowedStep], "lancer");
 802       }
 803       // No sentries or jailer tests: they cannot self-capture
 804     }
 805     return false;
 806   }
 807
 808   isAttackedBySentry([x, y], color) {
 809     // Attacked by sentry means it can self-take our king.
 810     // Just check diagonals of enemy sentry(ies), and if it reaches
 811     // one of our pieces: can I self-take?
 812     const myColor = V.GetOppCol(color);
 813     let candidates = [];
 814     for (let i=0; i<V.size.x; i++) {
 815       for (let j=0; j<V.size.y; j++) {
 816         if (
 817           this.getPiece(i,j) == V.SENTRY &&
 818           this.getColor(i,j) == color &&
 819           !this.isImmobilized([i, j])
 820         ) {
 821           for (let step of V.steps[V.BISHOP]) {
 822             let sq = [ i + step[0], j + step[1] ];
 823             while (
 824               V.OnBoard(sq[0], sq[1]) &&
 825               this.board[sq[0]][sq[1]] == V.EMPTY
 826             ) {
 827               sq[0] += step[0];
 828               sq[1] += step[1];
 829             }
 830             if (
 831               V.OnBoard(sq[0], sq[1]) &&
 832               this.getColor(sq[0], sq[1]) == myColor
 833             ) {
 834               candidates.push([ sq[0], sq[1] ]);
 835             }
 836           }
 837         }
 838       }
 839     }
 840     for (let c of candidates)
 841       if (this.selfAttack(c, [x, y])) return true;
 842     return false;
 843   }
 844
 845   // Jailer doesn't capture or give check
 846
 847   prePlay(move) {
 848     if (move.appear.length == 0 && move.vanish.length == 1)
 849       // The sentry is about to push a piece: subTurn goes from 1 to 2
 850       this.sentryPos = { x: move.end.x, y: move.end.y };
 851     if (this.subTurn == 2 && move.vanish[0].p != V.PAWN) {
 852       // A piece is pushed: forbid array of squares between start and end
 853       // of move, included (except if it's a pawn)
 854       let squares = [];
 855       if ([V.KNIGHT,V.KING].includes(move.vanish[0].p))
 856         // short-range pieces: just forbid initial square
 857         squares.push({ x: move.start.x, y: move.start.y });
 858       else {
 859         const deltaX = move.end.x - move.start.x;
 860         const deltaY = move.end.y - move.start.y;
 861         const step = [
 862           deltaX / Math.abs(deltaX) || 0,
 863           deltaY / Math.abs(deltaY) || 0
 864         ];
 865         for (
 866           let sq = {x: move.start.x, y: move.start.y};
 867           sq.x != move.end.x || sq.y != move.end.y;
 868           sq.x += step[0], sq.y += step[1]
 869         ) {
 870           squares.push({ x: sq.x, y: sq.y });
 871         }
 872       }
 873       // Add end square as well, to know if I was pushed (useful for lancers)
 874       squares.push({ x: move.end.x, y: move.end.y });
 875       this.sentryPush.push(squares);
 876     } else this.sentryPush.push(null);
 877   }
 878
 879   play(move) {
 880     this.prePlay(move);
 881     move.flags = JSON.stringify(this.aggregateFlags());
 882     this.epSquares.push(this.getEpSquare(move));
 883     V.PlayOnBoard(this.board, move);
 884     // Is it a sentry push? (useful for undo)
 885     move.sentryPush = (this.subTurn == 2);
 886     if (this.subTurn == 1) this.movesCount++;
 887     if (move.appear.length == 0 && move.vanish.length == 1) this.subTurn = 2;
 888     else {
 889       // Turn changes only if not a sentry "pre-push"
 890       this.turn = V.GetOppCol(this.turn);
 891       this.subTurn = 1;
 892     }
 893     this.postPlay(move);
 894   }
 895
 896   postPlay(move) {
 897     if (move.vanish.length == 0 || this.subTurn == 2)
 898       // Special pass move of the king, or sentry pre-push: nothing to update
 899       return;
 900     const c = move.vanish[0].c;
 901     const piece = move.vanish[0].p;
 902     const firstRank = c == "w" ? V.size.x - 1 : 0;
 903
 904     if (piece == V.KING) {
 905       this.kingPos[c][0] = move.appear[0].x;
 906       this.kingPos[c][1] = move.appear[0].y;
 907       this.castleFlags[c] = [V.size.y, V.size.y];
 908       return;
 909     }
 910     // Update castling flags if rooks are moved
 911     const oppCol = V.GetOppCol(c);
 912     const oppFirstRank = V.size.x - 1 - firstRank;
 913     if (
 914       move.start.x == firstRank && //our rook moves?
 915       this.castleFlags[c].includes(move.start.y)
 916     ) {
 917       const flagIdx = (move.start.y == this.castleFlags[c][0] ? 0 : 1);
 918       this.castleFlags[c][flagIdx] = V.size.y;
 919     } else if (
 920       move.end.x == oppFirstRank && //we took opponent rook?
 921       this.castleFlags[oppCol].includes(move.end.y)
 922     ) {
 923       const flagIdx = (move.end.y == this.castleFlags[oppCol][0] ? 0 : 1);
 924       this.castleFlags[oppCol][flagIdx] = V.size.y;
 925     }
 926   }
 927
 928   undo(move) {
 929     this.epSquares.pop();
 930     this.disaggregateFlags(JSON.parse(move.flags));
 931     V.UndoOnBoard(this.board, move);
 932     // Decrement movesCount except if the move is a sentry push
 933     if (!move.sentryPush) this.movesCount--;
 934     if (this.subTurn == 2) this.subTurn = 1;
 935     else {
 936       this.turn = V.GetOppCol(this.turn);
 937       if (move.sentryPush) this.subTurn = 2;
 938     }
 939     this.postUndo(move);
 940   }
 941
 942   postUndo(move) {
 943     super.postUndo(move);
 944     this.sentryPush.pop();
 945   }
 946
 947   static get VALUES() {
 948     return Object.assign(
 949       { l: 4.8, s: 2.8, j: 3.8 }, //Jeff K. estimations
 950       ChessRules.VALUES
 951     );
 952   }
 953
 954   getComputerMove() {
 955     const maxeval = V.INFINITY;
 956     const color = this.turn;
 957     let moves1 = this.getAllValidMoves();
 958
 959     if (moves1.length == 0)
 960       // TODO: this situation should not happen
 961       return null;
 962
 963     const setEval = (move, next) => {
 964       const score = this.getCurrentScore();
 965       const curEval = move.eval;
 966       if (score != "*") {
 967         move.eval =
 968           score == "1/2"
 969             ? 0
 970             : (score == "1-0" ? 1 : -1) * maxeval;
 971       } else move.eval = this.evalPosition();
 972       if (
 973         // "next" is defined after sentry pushes
 974         !!next && (
 975           !curEval ||
 976           color == 'w' && move.eval > curEval ||
 977           color == 'b' && move.eval < curEval
 978         )
 979       ) {
 980         move.second = next;
 981       }
 982     };
 983
 984     // Just search_depth == 1 (because of sentries. TODO: can do better...)
 985     moves1.forEach(m1 => {
 986       this.play(m1);
 987       if (this.subTurn == 1) setEval(m1);
 988       else {
 989         // Need to play every pushes and count:
 990         const moves2 = this.getAllValidMoves();
 991         moves2.forEach(m2 => {
 992           this.play(m2);
 993           setEval(m1, m2);
 994           this.undo(m2);
 995         });
 996       }
 997       this.undo(m1);
 998     });
 999
1000     moves1.sort((a, b) => {
1001       return (color == "w" ? 1 : -1) * (b.eval - a.eval);
1002     });
1003     let candidates = [0];
1004     for (let j = 1; j < moves1.length && moves1[j].eval == moves1[0].eval; j++)
1005       candidates.push(j);
1006     const choice = moves1[candidates[randInt(candidates.length)]];
1007     return (!choice.second ? choice : [choice, choice.second]);
1008   }
1009
1010   // For moves notation:
1011   static get LANCER_DIRNAMES() {
1012     return {
1013       'c': "N",
1014       'd': "NE",
1015       'e': "E",
1016       'f': "SE",
1017       'g': "S",
1018       'h': "SW",
1019       'm': "W",
1020       'o': "NW"
1021     };
1022   }
1023
1024   getNotation(move) {
1025     // Special case "king takes jailer" is a pass move
1026     if (move.appear.length == 0 && move.vanish.length == 0) return "pass";
1027     let notation = undefined;
1028     if (this.subTurn == 2) {
1029       // Do not consider appear[1] (sentry) for sentry pushes
1030       const simpleMove = {
1031         appear: [move.appear[0]],
1032         vanish: move.vanish,
1033         start: move.start,
1034         end: move.end
1035       };
1036       notation = super.getNotation(simpleMove);
1037     } else notation = super.getNotation(move);
1038     if (Object.keys(V.LANCER_DIRNAMES).includes(move.vanish[0].p))
1039       // Lancer: add direction info
1040       notation += "=" + V.LANCER_DIRNAMES[move.appear[0].p];
1041     else if (
1042       move.vanish[0].p == V.PAWN &&
1043       Object.keys(V.LANCER_DIRNAMES).includes(move.appear[0].p)
1044     ) {
1045       // Fix promotions in lancer:
1046       notation = notation.slice(0, -1) + "L:" + V.LANCER_DIRNAMES[move.appear[0].p];
1047     }
1048     return notation;
1049   }
1050 };