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]){2,2}$/)
 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     const spL = this.sentryPush[L-1].length;
 131     // Condensate path: just need initial and final squares:
 132     return [0, spL - 1]
 133       .map(i => V.CoordsToSquare(this.sentryPush[L-1][i]))
 134       .join("");
 135   }
 136
 137   setOtherVariables(fen) {
 138     super.setOtherVariables(fen);
 139     // subTurn == 2 only when a sentry moved, and is about to push something
 140     this.subTurn = 1;
 141     // Sentry position just after a "capture" (subTurn from 1 to 2)
 142     this.sentryPos = null;
 143     // Stack pieces' forbidden squares after a sentry move at each turn
 144     const parsedFen = V.ParseFen(fen);
 145     if (parsedFen.sentrypush == "-") this.sentryPush = [null];
 146     else {
 147       // Expand init + dest squares into a full path:
 148       const init = V.SquareToCoords(parsedFen.sentrypush.substr(0, 2)),
 149             dest = V.SquareToCoords(parsedFen.sentrypush.substr(2));
 150       let newPath = [init];
 151       const delta = ['x', 'y'].map(i => Math.abs(dest[i] - init[i]));
 152       // Check that it's not a knight movement:
 153       if (delta[0] == 0 || delta[1] == 0 || delta[0] == delta[1]) {
 154         const step = ['x', 'y'].map((i, idx) => {
 155           return (dest[i] - init[i]) / delta[idx] || 0
 156         });
 157         let x = init.x + step[0],
 158             y = init.y + step[1];
 159         while (x != dest.x || y != dest.y) {
 160           newPath.push({ x: x, y: y });
 161           x += step[0];
 162           y += step[1];
 163         }
 164       }
 165       newPath.push(dest);
 166       this.sentryPush = [newPath];
 167     }
 168   }
 169
 170   static GenRandInitFen(randomness) {
 171     if (randomness == 0)
 172       // Deterministic:
 173       return "jfsqkbnr/pppppppp/8/8/8/8/PPPPPPPP/JDSQKBNR w 0 ahah - -";
 174
 175     let pieces = { w: new Array(8), b: new Array(8) };
 176     let flags = "";
 177     // Shuffle pieces on first (and last rank if randomness == 2)
 178     for (let c of ["w", "b"]) {
 179       if (c == 'b' && randomness == 1) {
 180         const lancerIdx = pieces['w'].findIndex(p => {
 181           return Object.keys(V.LANCER_DIRS).includes(p);
 182         });
 183         pieces['b'] =
 184           pieces['w'].slice(0, lancerIdx)
 185           .concat(['g'])
 186           .concat(pieces['w'].slice(lancerIdx + 1));
 187         flags += flags;
 188         break;
 189       }
 190
 191       let positions = ArrayFun.range(8);
 192
 193       // Get random squares for bishop and sentry
 194       let randIndex = 2 * randInt(4);
 195       let bishopPos = positions[randIndex];
 196       // The sentry must be on a square of different color
 197       let randIndex_tmp = 2 * randInt(4) + 1;
 198       let sentryPos = positions[randIndex_tmp];
 199       if (c == 'b') {
 200         // Check if white sentry is on the same color as ours.
 201         // If yes: swap bishop and sentry positions.
 202         // NOTE: test % 2 == 1 because there are 7 slashes.
 203         if ((pieces['w'].indexOf('s') - sentryPos) % 2 == 1)
 204           [bishopPos, sentryPos] = [sentryPos, bishopPos];
 205       }
 206       positions.splice(Math.max(randIndex, randIndex_tmp), 1);
 207       positions.splice(Math.min(randIndex, randIndex_tmp), 1);
 208
 209       // Get random squares for knight and lancer
 210       randIndex = randInt(6);
 211       const knightPos = positions[randIndex];
 212       positions.splice(randIndex, 1);
 213       randIndex = randInt(5);
 214       const lancerPos = positions[randIndex];
 215       positions.splice(randIndex, 1);
 216
 217       // Get random square for queen
 218       randIndex = randInt(4);
 219       const queenPos = positions[randIndex];
 220       positions.splice(randIndex, 1);
 221
 222       // Rook, jailer and king positions are now almost fixed,
 223       // only the ordering rook->jailer or jailer->rook must be decided.
 224       let rookPos = positions[0];
 225       let jailerPos = positions[2];
 226       const kingPos = positions[1];
 227       flags += V.CoordToColumn(rookPos) + V.CoordToColumn(jailerPos);
 228       if (Math.random() < 0.5) [rookPos, jailerPos] = [jailerPos, rookPos];
 229
 230       pieces[c][rookPos] = "r";
 231       pieces[c][knightPos] = "n";
 232       pieces[c][bishopPos] = "b";
 233       pieces[c][queenPos] = "q";
 234       pieces[c][kingPos] = "k";
 235       pieces[c][sentryPos] = "s";
 236       // Lancer faces north for white, and south for black:
 237       pieces[c][lancerPos] = c == 'w' ? 'c' : 'g';
 238       pieces[c][jailerPos] = "j";
 239     }
 240     return (
 241       pieces["b"].join("") +
 242       "/pppppppp/8/8/8/8/PPPPPPPP/" +
 243       pieces["w"].join("").toUpperCase() +
 244       " w 0 " + flags + " - -"
 245     );
 246   }
 247
 248   canTake([x1, y1], [x2, y2]) {
 249     if (this.subTurn == 2)
 250       // Only self captures on this subturn:
 251       return this.getColor(x1, y1) == this.getColor(x2, y2);
 252     return super.canTake([x1, y1], [x2, y2]);
 253   }
 254
 255   // Is piece on square (x,y) immobilized?
 256   isImmobilized([x, y]) {
 257     const color = this.getColor(x, y);
 258     const oppCol = V.GetOppCol(color);
 259     for (let step of V.steps[V.ROOK]) {
 260       const [i, j] = [x + step[0], y + step[1]];
 261       if (
 262         V.OnBoard(i, j) &&
 263         this.board[i][j] != V.EMPTY &&
 264         this.getColor(i, j) == oppCol
 265       ) {
 266         if (this.getPiece(i, j) == V.JAILER) return [i, j];
 267       }
 268     }
 269     return null;
 270   }
 271
 272   // Because of the lancers, getPiece() could be wrong:
 273   // use board[x][y][1] instead (always valid).
 274   getBasicMove([sx, sy], [ex, ey], tr) {
 275     const initColor = this.getColor(sx, sy);
 276     const initPiece = this.board[sx][sy].charAt(1);
 277     let mv = new Move({
 278       appear: [
 279         new PiPo({
 280           x: ex,
 281           y: ey,
 282           c: tr ? tr.c : initColor,
 283           p: tr ? tr.p : initPiece
 284         })
 285       ],
 286       vanish: [
 287         new PiPo({
 288           x: sx,
 289           y: sy,
 290           c: initColor,
 291           p: initPiece
 292         })
 293       ]
 294     });
 295
 296     // The opponent piece disappears if we take it
 297     if (this.board[ex][ey] != V.EMPTY) {
 298       mv.vanish.push(
 299         new PiPo({
 300           x: ex,
 301           y: ey,
 302           c: this.getColor(ex, ey),
 303           p: this.board[ex][ey].charAt(1)
 304         })
 305       );
 306     }
 307
 308     return mv;
 309   }
 310
 311   canIplay(side, [x, y]) {
 312     return (
 313       (this.subTurn == 1 && this.turn == side && this.getColor(x, y) == side)
 314       ||
 315       (this.subTurn == 2 && x == this.sentryPos.x && y == this.sentryPos.y)
 316     );
 317   }
 318
 319   getPotentialMovesFrom([x, y]) {
 320     const piece = this.getPiece(x, y);
 321     const L = this.sentryPush.length;
 322     // At subTurn == 2, jailers aren't effective (Jeff K)
 323     if (this.subTurn == 1) {
 324       const jsq = this.isImmobilized([x, y]);
 325       if (!!jsq) {
 326         let moves = [];
 327         // Special pass move if king:
 328         if (piece == V.KING) {
 329           moves.push(
 330             new Move({
 331               appear: [],
 332               vanish: [],
 333               start: { x: x, y: y },
 334               end: { x: jsq[0], y: jsq[1] }
 335             })
 336           );
 337         }
 338         else if (piece == V.LANCER && !!this.sentryPush[L-1]) {
 339           // A pushed lancer next to the jailer: reorient
 340           const color = this.getColor(x, y);
 341           const curDir = this.board[x][y].charAt(1);
 342           Object.keys(V.LANCER_DIRS).forEach(k => {
 343             moves.push(
 344               new Move({
 345                 appear: [{ x: x, y: y, c: color, p: k }],
 346                 vanish: [{ x: x, y: y, c: color, p: curDir }],
 347                 start: { x: x, y: y },
 348                 end: { x: jsq[0], y: jsq[1] }
 349               })
 350             );
 351           });
 352         }
 353         return moves;
 354       }
 355     }
 356     let moves = [];
 357     switch (piece) {
 358       case V.JAILER:
 359         moves = this.getPotentialJailerMoves([x, y]);
 360         break;
 361       case V.SENTRY:
 362         moves = this.getPotentialSentryMoves([x, y]);
 363         break;
 364       case V.LANCER:
 365         moves = this.getPotentialLancerMoves([x, y]);
 366         break;
 367       default:
 368         moves = super.getPotentialMovesFrom([x, y]);
 369         break;
 370     }
 371     if (!!this.sentryPush[L-1]) {
 372       // Delete moves walking back on sentry push path,
 373       // only if not a pawn, and the piece is the pushed one.
 374       const pl = this.sentryPush[L-1].length;
 375       const finalPushedSq = this.sentryPush[L-1][pl-1];
 376       moves = moves.filter(m => {
 377         if (
 378           m.vanish[0].p != V.PAWN &&
 379           m.start.x == finalPushedSq.x && m.start.y == finalPushedSq.y &&
 380           this.sentryPush[L-1].some(sq => sq.x == m.end.x && sq.y == m.end.y)
 381         ) {
 382           return false;
 383         }
 384         return true;
 385       });
 386     } else if (this.subTurn == 2) {
 387       // Put back the sentinel on board:
 388       const color = this.turn;
 389       moves.forEach(m => {
 390         m.appear.push({x: x, y: y, p: V.SENTRY, c: color});
 391       });
 392     }
 393     return moves;
 394   }
 395
 396   getPotentialPawnMoves([x, y]) {
 397     const color = this.getColor(x, y);
 398     let moves = [];
 399     const [sizeX, sizeY] = [V.size.x, V.size.y];
 400     let shiftX = (color == "w" ? -1 : 1);
 401     if (this.subTurn == 2) shiftX *= -1;
 402     const firstRank = color == "w" ? sizeX - 1 : 0;
 403     const startRank = color == "w" ? sizeX - 2 : 1;
 404     const lastRank = color == "w" ? 0 : sizeX - 1;
 405
 406     // Pawns might be pushed on 1st rank and attempt to move again:
 407     if (!V.OnBoard(x + shiftX, y)) return [];
 408
 409     const finalPieces =
 410       // A push cannot put a pawn on last rank (it goes backward)
 411       x + shiftX == lastRank
 412         ? Object.keys(V.LANCER_DIRS).concat(
 413           [V.ROOK, V.KNIGHT, V.BISHOP, V.QUEEN, V.SENTRY, V.JAILER])
 414         : [V.PAWN];
 415     if (this.board[x + shiftX][y] == V.EMPTY) {
 416       // One square forward
 417       for (let piece of finalPieces) {
 418         moves.push(
 419           this.getBasicMove([x, y], [x + shiftX, y], {
 420             c: color,
 421             p: piece
 422           })
 423         );
 424       }
 425       if (
 426         // 2-squares jumps forbidden if pawn push
 427         this.subTurn == 1 &&
 428         [startRank, firstRank].includes(x) &&
 429         this.board[x + 2 * shiftX][y] == V.EMPTY
 430       ) {
 431         // Two squares jump
 432         moves.push(this.getBasicMove([x, y], [x + 2 * shiftX, y]));
 433       }
 434     }
 435     // Captures
 436     for (let shiftY of [-1, 1]) {
 437       if (
 438         y + shiftY >= 0 &&
 439         y + shiftY < sizeY &&
 440         this.board[x + shiftX][y + shiftY] != V.EMPTY &&
 441         this.canTake([x, y], [x + shiftX, y + shiftY])
 442       ) {
 443         for (let piece of finalPieces) {
 444           moves.push(
 445             this.getBasicMove([x, y], [x + shiftX, y + shiftY], {
 446               c: color,
 447               p: piece
 448             })
 449           );
 450         }
 451       }
 452     }
 453
 454     // En passant: only on subTurn == 1
 455     const Lep = this.epSquares.length;
 456     const epSquare = this.epSquares[Lep - 1];
 457     if (
 458       this.subTurn == 1 &&
 459       !!epSquare &&
 460       epSquare.x == x + shiftX &&
 461       Math.abs(epSquare.y - y) == 1
 462     ) {
 463       let enpassantMove = this.getBasicMove([x, y], [epSquare.x, epSquare.y]);
 464       enpassantMove.vanish.push({
 465         x: x,
 466         y: epSquare.y,
 467         p: "p",
 468         c: this.getColor(x, epSquare.y)
 469       });
 470       moves.push(enpassantMove);
 471     }
 472
 473     return moves;
 474   }
 475
 476   doClick(square) {
 477     if (isNaN(square[0])) return null;
 478     const L = this.sentryPush.length;
 479     const [x, y] = [square[0], square[1]];
 480     const color = this.turn;
 481     if (
 482       this.subTurn == 2 ||
 483       this.board[x][y] == V.EMPTY ||
 484       this.getPiece(x, y) != V.LANCER ||
 485       this.getColor(x, y) != color ||
 486       !!this.sentryPush[L-1]
 487     ) {
 488       return null;
 489     }
 490     // Stuck lancer?
 491     const orientation = this.board[x][y][1];
 492     const step = V.LANCER_DIRS[orientation];
 493     if (!V.OnBoard(x + step[0], y + step[1])) {
 494       let choices = [];
 495       Object.keys(V.LANCER_DIRS).forEach(k => {
 496         const dir = V.LANCER_DIRS[k];
 497         if (
 498           (dir[0] != step[0] || dir[1] != step[1]) &&
 499           V.OnBoard(x + dir[0], y + dir[1])
 500         ) {
 501           choices.push(
 502             new Move({
 503               vanish: [
 504                 new PiPo({
 505                   x: x,
 506                   y: y,
 507                   c: color,
 508                   p: orientation
 509                 })
 510               ],
 511               appear: [
 512                 new PiPo({
 513                   x: x,
 514                   y: y,
 515                   c: color,
 516                   p: k
 517                 })
 518               ],
 519               start: { x: x, y : y },
 520               end: { x: -1, y: -1 }
 521             })
 522           );
 523         }
 524       });
 525       return choices;
 526     }
 527     return null;
 528   }
 529
 530   // Obtain all lancer moves in "step" direction
 531   getPotentialLancerMoves_aux([x, y], step, tr) {
 532     let moves = [];
 533     // Add all moves to vacant squares until opponent is met:
 534     const color = this.getColor(x, y);
 535     const oppCol =
 536       this.subTurn == 1
 537         ? V.GetOppCol(color)
 538         // at subTurn == 2, consider own pieces as opponent
 539         : color;
 540     let sq = [x + step[0], y + step[1]];
 541     while (V.OnBoard(sq[0], sq[1]) && this.getColor(sq[0], sq[1]) != oppCol) {
 542       if (this.board[sq[0]][sq[1]] == V.EMPTY)
 543         moves.push(this.getBasicMove([x, y], sq, tr));
 544       sq[0] += step[0];
 545       sq[1] += step[1];
 546     }
 547     if (V.OnBoard(sq[0], sq[1]))
 548       // Add capturing move
 549       moves.push(this.getBasicMove([x, y], sq, tr));
 550     return moves;
 551   }
 552
 553   getPotentialLancerMoves([x, y]) {
 554     let moves = [];
 555     // Add all lancer possible orientations, similar to pawn promotions.
 556     // Except if just after a push: allow all movements from init square then
 557     const L = this.sentryPush.length;
 558     const color = this.getColor(x, y);
 559     const dirCode = this.board[x][y][1];
 560     const curDir = V.LANCER_DIRS[dirCode];
 561     if (!!this.sentryPush[L-1]) {
 562       // Maybe I was pushed
 563       const pl = this.sentryPush[L-1].length;
 564       if (
 565         this.sentryPush[L-1][pl-1].x == x &&
 566         this.sentryPush[L-1][pl-1].y == y
 567       ) {
 568         // I was pushed: allow all directions (for this move only), but
 569         // do not change direction after moving, *except* if I keep the
 570         // same orientation in which I was pushed.
 571         // Also allow simple reorientation ("capturing king"):
 572         if (!V.OnBoard(x + curDir[0], y + curDir[1])) {
 573           const kp = this.kingPos[color];
 574           let reorientMoves = [];
 575           Object.keys(V.LANCER_DIRS).forEach(k => {
 576             const dir = V.LANCER_DIRS[k];
 577             if (
 578               (dir[0] != curDir[0] || dir[1] != curDir[1]) &&
 579               V.OnBoard(x + dir[0], y + dir[1])
 580             ) {
 581               reorientMoves.push(
 582                 new Move({
 583                   vanish: [
 584                     new PiPo({
 585                       x: x,
 586                       y: y,
 587                       c: color,
 588                       p: dirCode
 589                     })
 590                   ],
 591                   appear: [
 592                     new PiPo({
 593                       x: x,
 594                       y: y,
 595                       c: color,
 596                       p: k
 597                     })
 598                   ],
 599                   start: { x: x, y : y },
 600                   end: { x: kp[0], y: kp[1] }
 601                 })
 602               );
 603             }
 604           });
 605           Array.prototype.push.apply(moves, reorientMoves);
 606         }
 607         Object.values(V.LANCER_DIRS).forEach(step => {
 608           const dirCode = Object.keys(V.LANCER_DIRS).find(k => {
 609             return (
 610               V.LANCER_DIRS[k][0] == step[0] &&
 611               V.LANCER_DIRS[k][1] == step[1]
 612             );
 613           });
 614           const dirMoves =
 615             this.getPotentialLancerMoves_aux(
 616               [x, y],
 617               step,
 618               { p: dirCode, c: color }
 619             );
 620           if (curDir[0] == step[0] && curDir[1] == step[1]) {
 621             // Keeping same orientation: can choose after
 622             let chooseMoves = [];
 623             dirMoves.forEach(m => {
 624               Object.keys(V.LANCER_DIRS).forEach(k => {
 625                 let mk = JSON.parse(JSON.stringify(m));
 626                 mk.appear[0].p = k;
 627                 moves.push(mk);
 628               });
 629             });
 630             Array.prototype.push.apply(moves, chooseMoves);
 631           } else Array.prototype.push.apply(moves, dirMoves);
 632         });
 633         return moves;
 634       }
 635     }
 636     // I wasn't pushed: standard lancer move
 637     const monodirMoves =
 638       this.getPotentialLancerMoves_aux([x, y], V.LANCER_DIRS[dirCode]);
 639     // Add all possible orientations aftermove except if I'm being pushed
 640     if (this.subTurn == 1) {
 641       monodirMoves.forEach(m => {
 642         Object.keys(V.LANCER_DIRS).forEach(k => {
 643           let mk = JSON.parse(JSON.stringify(m));
 644           mk.appear[0].p = k;
 645           moves.push(mk);
 646         });
 647       });
 648       return moves;
 649     } else {
 650       // I'm pushed: add potential nudges, except for current orientation
 651       let potentialNudges = [];
 652       for (let step of V.steps[V.ROOK].concat(V.steps[V.BISHOP])) {
 653         if (
 654           (step[0] != curDir[0] || step[1] != curDir[1]) &&
 655           V.OnBoard(x + step[0], y + step[1]) &&
 656           this.board[x + step[0]][y + step[1]] == V.EMPTY
 657         ) {
 658           const newDirCode = Object.keys(V.LANCER_DIRS).find(k => {
 659             const codeStep = V.LANCER_DIRS[k];
 660             return (codeStep[0] == step[0] && codeStep[1] == step[1]);
 661           });
 662           potentialNudges.push(
 663             this.getBasicMove(
 664               [x, y],
 665               [x + step[0], y + step[1]],
 666               { c: color, p: newDirCode }
 667             )
 668           );
 669         }
 670       }
 671       return monodirMoves.concat(potentialNudges);
 672     }
 673   }
 674
 675   getPotentialSentryMoves([x, y]) {
 676     // The sentry moves a priori like a bishop:
 677     let moves = super.getPotentialBishopMoves([x, y]);
 678     // ...but captures are replaced by special move, if and only if
 679     // "captured" piece can move now, considered as the capturer unit.
 680     // --> except is subTurn == 2, in this case I don't push anything.
 681     if (this.subTurn == 2) return moves.filter(m => m.vanish.length == 1);
 682     moves.forEach(m => {
 683       if (m.vanish.length == 2) {
 684         // Temporarily cancel the sentry capture:
 685         m.appear.pop();
 686         m.vanish.pop();
 687       }
 688     });
 689     const color = this.getColor(x, y);
 690     const fMoves = moves.filter(m => {
 691       // Can the pushed unit make any move? ...resulting in a non-self-check?
 692       if (m.appear.length == 0) {
 693         let res = false;
 694         this.play(m);
 695         let moves2 = this.getPotentialMovesFrom([m.end.x, m.end.y]);
 696         for (let m2 of moves2) {
 697           this.play(m2);
 698           res = !this.underCheck(color);
 699           this.undo(m2);
 700           if (res) break;
 701         }
 702         this.undo(m);
 703         return res;
 704       }
 705       return true;
 706     });
 707     return fMoves;
 708   }
 709
 710   getPotentialJailerMoves([x, y]) {
 711     return super.getPotentialRookMoves([x, y]).filter(m => {
 712       // Remove jailer captures
 713       return m.vanish[0].p != V.JAILER || m.vanish.length == 1;
 714     });
 715   }
 716
 717   getPotentialKingMoves(sq) {
 718     const moves = this.getSlideNJumpMoves(
 719       sq,
 720       V.steps[V.ROOK].concat(V.steps[V.BISHOP]),
 721       "oneStep"
 722     );
 723     return (
 724       this.subTurn == 1
 725         ? moves.concat(this.getCastleMoves(sq))
 726         : moves
 727     );
 728   }
 729
 730   atLeastOneMove() {
 731     // If in second-half of a move, we already know that a move is possible
 732     if (this.subTurn == 2) return true;
 733     return super.atLeastOneMove();
 734   }
 735
 736   filterValid(moves) {
 737     if (moves.length == 0) return [];
 738     const basicFilter = (m, c) => {
 739       this.play(m);
 740       const res = !this.underCheck(c);
 741       this.undo(m);
 742       return res;
 743     };
 744     // Disable check tests for sentry pushes,
 745     // because in this case the move isn't finished
 746     let movesWithoutSentryPushes = [];
 747     let movesWithSentryPushes = [];
 748     moves.forEach(m => {
 749       // Second condition below for special king "pass" moves
 750       if (m.appear.length > 0 || m.vanish.length == 0)
 751         movesWithoutSentryPushes.push(m);
 752       else movesWithSentryPushes.push(m);
 753     });
 754     const color = this.turn;
 755     const oppCol = V.GetOppCol(color);
 756     const filteredMoves =
 757       movesWithoutSentryPushes.filter(m => basicFilter(m, color));
 758     // If at least one full move made, everything is allowed.
 759     // Else: forbid checks and captures.
 760     return (
 761       this.movesCount >= 2
 762         ? filteredMoves
 763         : filteredMoves.filter(m => {
 764           return (m.vanish.length <= 1 && basicFilter(m, oppCol));
 765         })
 766     ).concat(movesWithSentryPushes);
 767   }
 768
 769   getAllValidMoves() {
 770     if (this.subTurn == 1) return super.getAllValidMoves();
 771     // Sentry push:
 772     const sentrySq = [this.sentryPos.x, this.sentryPos.y];
 773     return this.filterValid(this.getPotentialMovesFrom(sentrySq));
 774   }
 775
 776   isAttacked(sq, color) {
 777     return (
 778       super.isAttacked(sq, color) ||
 779       this.isAttackedByLancer(sq, color) ||
 780       this.isAttackedBySentry(sq, color)
 781       // The jailer doesn't capture.
 782     );
 783   }
 784
 785   isAttackedBySlideNJump([x, y], color, piece, steps, oneStep) {
 786     for (let step of steps) {
 787       let rx = x + step[0],
 788           ry = y + step[1];
 789       while (V.OnBoard(rx, ry) && this.board[rx][ry] == V.EMPTY && !oneStep) {
 790         rx += step[0];
 791         ry += step[1];
 792       }
 793       if (
 794         V.OnBoard(rx, ry) &&
 795         this.getPiece(rx, ry) == piece &&
 796         this.getColor(rx, ry) == color &&
 797         !this.isImmobilized([rx, ry])
 798       ) {
 799         return true;
 800       }
 801     }
 802     return false;
 803   }
 804
 805   isAttackedByPawn([x, y], color) {
 806     const pawnShift = (color == "w" ? 1 : -1);
 807     if (x + pawnShift >= 0 && x + pawnShift < V.size.x) {
 808       for (let i of [-1, 1]) {
 809         if (
 810           y + i >= 0 &&
 811           y + i < V.size.y &&
 812           this.getPiece(x + pawnShift, y + i) == V.PAWN &&
 813           this.getColor(x + pawnShift, y + i) == color &&
 814           !this.isImmobilized([x + pawnShift, y + i])
 815         ) {
 816           return true;
 817         }
 818       }
 819     }
 820     return false;
 821   }
 822
 823   isAttackedByLancer([x, y], color) {
 824     for (let step of V.steps[V.ROOK].concat(V.steps[V.BISHOP])) {
 825       // If in this direction there are only enemy pieces and empty squares,
 826       // and we meet a lancer: can he reach us?
 827       // NOTE: do not stop at first lancer, there might be several!
 828       let coord = { x: x + step[0], y: y + step[1] };
 829       let lancerPos = [];
 830       while (
 831         V.OnBoard(coord.x, coord.y) &&
 832         (
 833           this.board[coord.x][coord.y] == V.EMPTY ||
 834           this.getColor(coord.x, coord.y) == color
 835         )
 836       ) {
 837         if (
 838           this.getPiece(coord.x, coord.y) == V.LANCER &&
 839           !this.isImmobilized([coord.x, coord.y])
 840         ) {
 841           lancerPos.push({x: coord.x, y: coord.y});
 842         }
 843         coord.x += step[0];
 844         coord.y += step[1];
 845       }
 846       const L = this.sentryPush.length;
 847       const pl = (!!this.sentryPush[L-1] ? this.sentryPush[L-1].length : 0);
 848       for (let xy of lancerPos) {
 849         const dir = V.LANCER_DIRS[this.board[xy.x][xy.y].charAt(1)];
 850         if (
 851           (dir[0] == -step[0] && dir[1] == -step[1]) ||
 852           // If the lancer was just pushed, this is an attack too:
 853           (
 854             !!this.sentryPush[L-1] &&
 855             this.sentryPush[L-1][pl-1].x == xy.x &&
 856             this.sentryPush[L-1][pl-1].y == xy.y
 857           )
 858         ) {
 859           return true;
 860         }
 861       }
 862     }
 863     return false;
 864   }
 865
 866   // Helper to check sentries attacks:
 867   selfAttack([x1, y1], [x2, y2]) {
 868     const color = this.getColor(x1, y1);
 869     const oppCol = V.GetOppCol(color);
 870     const sliderAttack = (allowedSteps, lancer) => {
 871       const deltaX = x2 - x1,
 872             absDeltaX = Math.abs(deltaX);
 873       const deltaY = y2 - y1,
 874             absDeltaY = Math.abs(deltaY);
 875       const step = [ deltaX / absDeltaX || 0, deltaY / absDeltaY || 0 ];
 876       if (
 877         // Check that the step is a priori valid:
 878         (absDeltaX != absDeltaY && deltaX != 0 && deltaY != 0) ||
 879         allowedSteps.every(st => st[0] != step[0] || st[1] != step[1])
 880       ) {
 881         return false;
 882       }
 883       let sq = [ x1 + step[0], y1 + step[1] ];
 884       while (sq[0] != x2 || sq[1] != y2) {
 885         if (
 886           // NOTE: no need to check OnBoard in this special case
 887           (!lancer && this.board[sq[0]][sq[1]] != V.EMPTY) ||
 888           (!!lancer && this.getColor(sq[0], sq[1]) == oppCol)
 889         ) {
 890           return false;
 891         }
 892         sq[0] += step[0];
 893         sq[1] += step[1];
 894       }
 895       return true;
 896     };
 897     switch (this.getPiece(x1, y1)) {
 898       case V.PAWN: {
 899         // Pushed pawns move as enemy pawns
 900         const shift = (color == 'w' ? 1 : -1);
 901         return (x1 + shift == x2 && Math.abs(y1 - y2) == 1);
 902       }
 903       case V.KNIGHT: {
 904         const deltaX = Math.abs(x1 - x2);
 905         const deltaY = Math.abs(y1 - y2);
 906         return (
 907           deltaX + deltaY == 3 &&
 908           [1, 2].includes(deltaX) &&
 909           [1, 2].includes(deltaY)
 910         );
 911       }
 912       case V.ROOK:
 913         return sliderAttack(V.steps[V.ROOK]);
 914       case V.BISHOP:
 915         return sliderAttack(V.steps[V.BISHOP]);
 916       case V.QUEEN:
 917         return sliderAttack(V.steps[V.ROOK].concat(V.steps[V.BISHOP]));
 918       case V.LANCER: {
 919         // Special case: as long as no enemy units stands in-between,
 920         // it attacks (if it points toward the king).
 921         const allowedStep = V.LANCER_DIRS[this.board[x1][y1].charAt(1)];
 922         return sliderAttack([allowedStep], "lancer");
 923       }
 924       // No sentries or jailer tests: they cannot self-capture
 925     }
 926     return false;
 927   }
 928
 929   isAttackedBySentry([x, y], color) {
 930     // Attacked by sentry means it can self-take our king.
 931     // Just check diagonals of enemy sentry(ies), and if it reaches
 932     // one of our pieces: can I self-take?
 933     const myColor = V.GetOppCol(color);
 934     let candidates = [];
 935     for (let i=0; i<V.size.x; i++) {
 936       for (let j=0; j<V.size.y; j++) {
 937         if (
 938           this.getPiece(i,j) == V.SENTRY &&
 939           this.getColor(i,j) == color &&
 940           !this.isImmobilized([i, j])
 941         ) {
 942           for (let step of V.steps[V.BISHOP]) {
 943             let sq = [ i + step[0], j + step[1] ];
 944             while (
 945               V.OnBoard(sq[0], sq[1]) &&
 946               this.board[sq[0]][sq[1]] == V.EMPTY
 947             ) {
 948               sq[0] += step[0];
 949               sq[1] += step[1];
 950             }
 951             if (
 952               V.OnBoard(sq[0], sq[1]) &&
 953               this.getColor(sq[0], sq[1]) == myColor
 954             ) {
 955               candidates.push([ sq[0], sq[1] ]);
 956             }
 957           }
 958         }
 959       }
 960     }
 961     for (let c of candidates)
 962       if (this.selfAttack(c, [x, y])) return true;
 963     return false;
 964   }
 965
 966   // Jailer doesn't capture or give check
 967
 968   prePlay(move) {
 969     if (move.appear.length == 0 && move.vanish.length == 1)
 970       // The sentry is about to push a piece: subTurn goes from 1 to 2
 971       this.sentryPos = { x: move.end.x, y: move.end.y };
 972     if (this.subTurn == 2 && move.vanish[0].p != V.PAWN) {
 973       // A piece is pushed: forbid array of squares between start and end
 974       // of move, included (except if it's a pawn)
 975       let squares = [];
 976       if ([V.KNIGHT,V.KING].includes(move.vanish[0].p))
 977         // short-range pieces: just forbid initial square
 978         squares.push({ x: move.start.x, y: move.start.y });
 979       else {
 980         const deltaX = move.end.x - move.start.x;
 981         const deltaY = move.end.y - move.start.y;
 982         const step = [
 983           deltaX / Math.abs(deltaX) || 0,
 984           deltaY / Math.abs(deltaY) || 0
 985         ];
 986         for (
 987           let sq = {x: move.start.x, y: move.start.y};
 988           sq.x != move.end.x || sq.y != move.end.y;
 989           sq.x += step[0], sq.y += step[1]
 990         ) {
 991           squares.push({ x: sq.x, y: sq.y });
 992         }
 993       }
 994       // Add end square as well, to know if I was pushed (useful for lancers)
 995       squares.push({ x: move.end.x, y: move.end.y });
 996       this.sentryPush.push(squares);
 997     } else this.sentryPush.push(null);
 998   }
 999
1000   play(move) {
1001     this.prePlay(move);
1002     move.flags = JSON.stringify(this.aggregateFlags());
1003     this.epSquares.push(this.getEpSquare(move));
1004     V.PlayOnBoard(this.board, move);
1005     // Is it a sentry push? (useful for undo)
1006     move.sentryPush = (this.subTurn == 2);
1007     if (this.subTurn == 1) this.movesCount++;
1008     if (move.appear.length == 0 && move.vanish.length == 1) this.subTurn = 2;
1009     else {
1010       // Turn changes only if not a sentry "pre-push"
1011       this.turn = V.GetOppCol(this.turn);
1012       this.subTurn = 1;
1013     }
1014     this.postPlay(move);
1015   }
1016
1017   postPlay(move) {
1018     if (move.vanish.length == 0 || this.subTurn == 2)
1019       // Special pass move of the king, or sentry pre-push: nothing to update
1020       return;
1021     const c = move.vanish[0].c;
1022     const piece = move.vanish[0].p;
1023     const firstRank = c == "w" ? V.size.x - 1 : 0;
1024
1025     if (piece == V.KING) {
1026       this.kingPos[c][0] = move.appear[0].x;
1027       this.kingPos[c][1] = move.appear[0].y;
1028       this.castleFlags[c] = [V.size.y, V.size.y];
1029       return;
1030     }
1031     // Update castling flags if rooks are moved
1032     const oppCol = V.GetOppCol(c);
1033     const oppFirstRank = V.size.x - 1 - firstRank;
1034     if (
1035       move.start.x == firstRank && //our rook moves?
1036       this.castleFlags[c].includes(move.start.y)
1037     ) {
1038       const flagIdx = (move.start.y == this.castleFlags[c][0] ? 0 : 1);
1039       this.castleFlags[c][flagIdx] = V.size.y;
1040     } else if (
1041       move.end.x == oppFirstRank && //we took opponent rook?
1042       this.castleFlags[oppCol].includes(move.end.y)
1043     ) {
1044       const flagIdx = (move.end.y == this.castleFlags[oppCol][0] ? 0 : 1);
1045       this.castleFlags[oppCol][flagIdx] = V.size.y;
1046     }
1047   }
1048
1049   undo(move) {
1050     this.epSquares.pop();
1051     this.disaggregateFlags(JSON.parse(move.flags));
1052     V.UndoOnBoard(this.board, move);
1053     // Decrement movesCount except if the move is a sentry push
1054     if (!move.sentryPush) this.movesCount--;
1055     if (this.subTurn == 2) this.subTurn = 1;
1056     else {
1057       this.turn = V.GetOppCol(this.turn);
1058       if (move.sentryPush) this.subTurn = 2;
1059     }
1060     this.postUndo(move);
1061   }
1062
1063   postUndo(move) {
1064     super.postUndo(move);
1065     this.sentryPush.pop();
1066   }
1067
1068   static get VALUES() {
1069     return Object.assign(
1070       { l: 4.8, s: 2.8, j: 3.8 }, //Jeff K. estimations
1071       ChessRules.VALUES
1072     );
1073   }
1074
1075   getComputerMove() {
1076     const maxeval = V.INFINITY;
1077     const color = this.turn;
1078     let moves1 = this.getAllValidMoves();
1079
1080     if (moves1.length == 0)
1081       // TODO: this situation should not happen
1082       return null;
1083
1084     const setEval = (move, next) => {
1085       const score = this.getCurrentScore();
1086       const curEval = move.eval;
1087       if (score != "*") {
1088         move.eval =
1089           score == "1/2"
1090             ? 0
1091             : (score == "1-0" ? 1 : -1) * maxeval;
1092       } else move.eval = this.evalPosition();
1093       if (
1094         // "next" is defined after sentry pushes
1095         !!next && (
1096           !curEval ||
1097           color == 'w' && move.eval > curEval ||
1098           color == 'b' && move.eval < curEval
1099         )
1100       ) {
1101         move.second = next;
1102       }
1103     };
1104
1105     // Just search_depth == 1 (because of sentries. TODO: can do better...)
1106     moves1.forEach(m1 => {
1107       this.play(m1);
1108       if (this.subTurn == 1) setEval(m1);
1109       else {
1110         // Need to play every pushes and count:
1111         const moves2 = this.getAllValidMoves();
1112         moves2.forEach(m2 => {
1113           this.play(m2);
1114           setEval(m1, m2);
1115           this.undo(m2);
1116         });
1117       }
1118       this.undo(m1);
1119     });
1120
1121     moves1.sort((a, b) => {
1122       return (color == "w" ? 1 : -1) * (b.eval - a.eval);
1123     });
1124     let candidates = [0];
1125     for (let j = 1; j < moves1.length && moves1[j].eval == moves1[0].eval; j++)
1126       candidates.push(j);
1127     const choice = moves1[candidates[randInt(candidates.length)]];
1128     return (!choice.second ? choice : [choice, choice.second]);
1129   }
1130
1131   // For moves notation:
1132   static get LANCER_DIRNAMES() {
1133     return {
1134       'c': "N",
1135       'd': "NE",
1136       'e': "E",
1137       'f': "SE",
1138       'g': "S",
1139       'h': "SW",
1140       'm': "W",
1141       'o': "NW"
1142     };
1143   }
1144
1145   getNotation(move) {
1146     // Special case "king takes jailer" is a pass move
1147     if (move.appear.length == 0 && move.vanish.length == 0) return "pass";
1148     let notation = undefined;
1149     if (this.subTurn == 2) {
1150       // Do not consider appear[1] (sentry) for sentry pushes
1151       const simpleMove = {
1152         appear: [move.appear[0]],
1153         vanish: move.vanish,
1154         start: move.start,
1155         end: move.end
1156       };
1157       notation = super.getNotation(simpleMove);
1158     }
1159     else if (
1160       move.appear.length > 0 &&
1161       move.vanish[0].x == move.appear[0].x &&
1162       move.vanish[0].y == move.appear[0].y
1163     ) {
1164       // Lancer in-place reorientation:
1165       notation = "L" + V.CoordsToSquare(move.start) + ":R";
1166     }
1167     else notation = super.getNotation(move);
1168     if (Object.keys(V.LANCER_DIRNAMES).includes(move.vanish[0].p))
1169       // Lancer: add direction info
1170       notation += "=" + V.LANCER_DIRNAMES[move.appear[0].p];
1171     else if (
1172       move.vanish[0].p == V.PAWN &&
1173       Object.keys(V.LANCER_DIRNAMES).includes(move.appear[0].p)
1174     ) {
1175       // Fix promotions in lancer:
1176       notation = notation.slice(0, -1) +
1177         "L:" + V.LANCER_DIRNAMES[move.appear[0].p];
1178     }
1179     return notation;
1180   }
1181 };