client/src/variants/Eightpieces.js

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