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     // At subTurn == 2, jailers aren't effective (Jeff K)
 321     const piece = this.getPiece(x, y);
 322     const L = this.sentryPush.length;
 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   // Obtain all lancer moves in "step" direction
 477   getPotentialLancerMoves_aux([x, y], step, tr) {
 478     let moves = [];
 479     // Add all moves to vacant squares until opponent is met:
 480     const color = this.getColor(x, y);
 481     const oppCol =
 482       this.subTurn == 1
 483         ? V.GetOppCol(color)
 484         // at subTurn == 2, consider own pieces as opponent
 485         : color;
 486     let sq = [x + step[0], y + step[1]];
 487     while (V.OnBoard(sq[0], sq[1]) && this.getColor(sq[0], sq[1]) != oppCol) {
 488       if (this.board[sq[0]][sq[1]] == V.EMPTY)
 489         moves.push(this.getBasicMove([x, y], sq, tr));
 490       sq[0] += step[0];
 491       sq[1] += step[1];
 492     }
 493     if (V.OnBoard(sq[0], sq[1]))
 494       // Add capturing move
 495       moves.push(this.getBasicMove([x, y], sq, tr));
 496     return moves;
 497   }
 498
 499   getPotentialLancerMoves([x, y]) {
 500     let moves = [];
 501     // Add all lancer possible orientations, similar to pawn promotions.
 502     // Except if just after a push: allow all movements from init square then
 503     const L = this.sentryPush.length;
 504     const color = this.getColor(x, y);
 505     if (!!this.sentryPush[L-1]) {
 506       // Maybe I was pushed
 507       const pl = this.sentryPush[L-1].length;
 508       if (
 509         this.sentryPush[L-1][pl-1].x == x &&
 510         this.sentryPush[L-1][pl-1].y == y
 511       ) {
 512         // I was pushed: allow all directions (for this move only), but
 513         // do not change direction after moving, *except* if I keep the
 514         // same orientation in which I was pushed.
 515         const curDir = V.LANCER_DIRS[this.board[x][y].charAt(1)];
 516         Object.values(V.LANCER_DIRS).forEach(step => {
 517           const dirCode = Object.keys(V.LANCER_DIRS).find(k => {
 518             return (
 519               V.LANCER_DIRS[k][0] == step[0] &&
 520               V.LANCER_DIRS[k][1] == step[1]
 521             );
 522           });
 523           const dirMoves =
 524             this.getPotentialLancerMoves_aux(
 525               [x, y],
 526               step,
 527               { p: dirCode, c: color }
 528             );
 529           if (curDir[0] == step[0] && curDir[1] == step[1]) {
 530             // Keeping same orientation: can choose after
 531             let chooseMoves = [];
 532             dirMoves.forEach(m => {
 533               Object.keys(V.LANCER_DIRS).forEach(k => {
 534                 let mk = JSON.parse(JSON.stringify(m));
 535                 mk.appear[0].p = k;
 536                 moves.push(mk);
 537               });
 538             });
 539             Array.prototype.push.apply(moves, chooseMoves);
 540           } else Array.prototype.push.apply(moves, dirMoves);
 541         });
 542         return moves;
 543       }
 544     }
 545     // I wasn't pushed: standard lancer move
 546     const dirCode = this.board[x][y][1];
 547     const monodirMoves =
 548       this.getPotentialLancerMoves_aux([x, y], V.LANCER_DIRS[dirCode]);
 549     // Add all possible orientations aftermove except if I'm being pushed
 550     if (this.subTurn == 1) {
 551       monodirMoves.forEach(m => {
 552         Object.keys(V.LANCER_DIRS).forEach(k => {
 553           let mk = JSON.parse(JSON.stringify(m));
 554           mk.appear[0].p = k;
 555           moves.push(mk);
 556         });
 557       });
 558       return moves;
 559     } else {
 560       // I'm pushed: add potential nudges
 561       let potentialNudges = [];
 562       for (let step of V.steps[V.ROOK].concat(V.steps[V.BISHOP])) {
 563         if (
 564           V.OnBoard(x + step[0], y + step[1]) &&
 565           this.board[x + step[0]][y + step[1]] == V.EMPTY
 566         ) {
 567           const newDirCode = Object.keys(V.LANCER_DIRS).find(k => {
 568             const codeStep = V.LANCER_DIRS[k];
 569             return (codeStep[0] == step[0] && codeStep[1] == step[1]);
 570           });
 571           potentialNudges.push(
 572             this.getBasicMove(
 573               [x, y],
 574               [x + step[0], y + step[1]],
 575               { c: color, p: newDirCode }
 576             )
 577           );
 578         }
 579       }
 580       return monodirMoves.concat(potentialNudges);
 581     }
 582   }
 583
 584   getPotentialSentryMoves([x, y]) {
 585     // The sentry moves a priori like a bishop:
 586     let moves = super.getPotentialBishopMoves([x, y]);
 587     // ...but captures are replaced by special move, if and only if
 588     // "captured" piece can move now, considered as the capturer unit.
 589     // --> except is subTurn == 2, in this case I don't push anything.
 590     if (this.subTurn == 2) return moves.filter(m => m.vanish.length == 1);
 591     moves.forEach(m => {
 592       if (m.vanish.length == 2) {
 593         // Temporarily cancel the sentry capture:
 594         m.appear.pop();
 595         m.vanish.pop();
 596       }
 597     });
 598     const color = this.getColor(x, y);
 599     const fMoves = moves.filter(m => {
 600       // Can the pushed unit make any move? ...resulting in a non-self-check?
 601       if (m.appear.length == 0) {
 602         let res = false;
 603         this.play(m);
 604         let moves2 = this.getPotentialMovesFrom([m.end.x, m.end.y]);
 605         for (let m2 of moves2) {
 606           this.play(m2);
 607           res = !this.underCheck(color);
 608           this.undo(m2);
 609           if (res) break;
 610         }
 611         this.undo(m);
 612         return res;
 613       }
 614       return true;
 615     });
 616     return fMoves;
 617   }
 618
 619   getPotentialJailerMoves([x, y]) {
 620     return super.getPotentialRookMoves([x, y]).filter(m => {
 621       // Remove jailer captures
 622       return m.vanish[0].p != V.JAILER || m.vanish.length == 1;
 623     });
 624   }
 625
 626   getPotentialKingMoves(sq) {
 627     const moves = this.getSlideNJumpMoves(
 628       sq,
 629       V.steps[V.ROOK].concat(V.steps[V.BISHOP]),
 630       "oneStep"
 631     );
 632     return (
 633       this.subTurn == 1
 634         ? moves.concat(this.getCastleMoves(sq))
 635         : moves
 636     );
 637   }
 638
 639   atLeastOneMove() {
 640     // If in second-half of a move, we already know that a move is possible
 641     if (this.subTurn == 2) return true;
 642     return super.atLeastOneMove();
 643   }
 644
 645   filterValid(moves) {
 646     if (moves.length == 0) return [];
 647     const basicFilter = (m, c) => {
 648       this.play(m);
 649       const res = !this.underCheck(c);
 650       this.undo(m);
 651       return res;
 652     };
 653     // Disable check tests for sentry pushes,
 654     // because in this case the move isn't finished
 655     let movesWithoutSentryPushes = [];
 656     let movesWithSentryPushes = [];
 657     moves.forEach(m => {
 658       // Second condition below for special king "pass" moves
 659       if (m.appear.length > 0 || m.vanish.length == 0)
 660         movesWithoutSentryPushes.push(m);
 661       else movesWithSentryPushes.push(m);
 662     });
 663     const color = this.turn;
 664     const oppCol = V.GetOppCol(color);
 665     const filteredMoves =
 666       movesWithoutSentryPushes.filter(m => basicFilter(m, color));
 667     // If at least one full move made, everything is allowed.
 668     // Else: forbid checks and captures.
 669     return (
 670       this.movesCount >= 2
 671         ? filteredMoves
 672         : filteredMoves.filter(m => {
 673           return (m.vanish.length <= 1 && basicFilter(m, oppCol));
 674         })
 675     ).concat(movesWithSentryPushes);
 676   }
 677
 678   getAllValidMoves() {
 679     if (this.subTurn == 1) return super.getAllValidMoves();
 680     // Sentry push:
 681     const sentrySq = [this.sentryPos.x, this.sentryPos.y];
 682     return this.filterValid(this.getPotentialMovesFrom(sentrySq));
 683   }
 684
 685   isAttacked(sq, color) {
 686     return (
 687       super.isAttacked(sq, color) ||
 688       this.isAttackedByLancer(sq, color) ||
 689       this.isAttackedBySentry(sq, color)
 690       // The jailer doesn't capture.
 691     );
 692   }
 693
 694   isAttackedBySlideNJump([x, y], color, piece, steps, oneStep) {
 695     for (let step of steps) {
 696       let rx = x + step[0],
 697           ry = y + step[1];
 698       while (V.OnBoard(rx, ry) && this.board[rx][ry] == V.EMPTY && !oneStep) {
 699         rx += step[0];
 700         ry += step[1];
 701       }
 702       if (
 703         V.OnBoard(rx, ry) &&
 704         this.getPiece(rx, ry) == piece &&
 705         this.getColor(rx, ry) == color &&
 706         !this.isImmobilized([rx, ry])
 707       ) {
 708         return true;
 709       }
 710     }
 711     return false;
 712   }
 713
 714   isAttackedByPawn([x, y], color) {
 715     const pawnShift = (color == "w" ? 1 : -1);
 716     if (x + pawnShift >= 0 && x + pawnShift < V.size.x) {
 717       for (let i of [-1, 1]) {
 718         if (
 719           y + i >= 0 &&
 720           y + i < V.size.y &&
 721           this.getPiece(x + pawnShift, y + i) == V.PAWN &&
 722           this.getColor(x + pawnShift, y + i) == color &&
 723           !this.isImmobilized([x + pawnShift, y + i])
 724         ) {
 725           return true;
 726         }
 727       }
 728     }
 729     return false;
 730   }
 731
 732   isAttackedByLancer([x, y], color) {
 733     for (let step of V.steps[V.ROOK].concat(V.steps[V.BISHOP])) {
 734       // If in this direction there are only enemy pieces and empty squares,
 735       // and we meet a lancer: can he reach us?
 736       // NOTE: do not stop at first lancer, there might be several!
 737       let coord = { x: x + step[0], y: y + step[1] };
 738       let lancerPos = [];
 739       while (
 740         V.OnBoard(coord.x, coord.y) &&
 741         (
 742           this.board[coord.x][coord.y] == V.EMPTY ||
 743           this.getColor(coord.x, coord.y) == color
 744         )
 745       ) {
 746         if (
 747           this.getPiece(coord.x, coord.y) == V.LANCER &&
 748           !this.isImmobilized([coord.x, coord.y])
 749         ) {
 750           lancerPos.push({x: coord.x, y: coord.y});
 751         }
 752         coord.x += step[0];
 753         coord.y += step[1];
 754       }
 755       for (let xy of lancerPos) {
 756         const dir = V.LANCER_DIRS[this.board[xy.x][xy.y].charAt(1)];
 757         if (dir[0] == -step[0] && dir[1] == -step[1]) return true;
 758       }
 759     }
 760     return false;
 761   }
 762
 763   // Helper to check sentries attacks:
 764   selfAttack([x1, y1], [x2, y2]) {
 765     const color = this.getColor(x1, y1);
 766     const oppCol = V.GetOppCol(color);
 767     const sliderAttack = (allowedSteps, lancer) => {
 768       const deltaX = x2 - x1,
 769             absDeltaX = Math.abs(deltaX);
 770       const deltaY = y2 - y1,
 771             absDeltaY = Math.abs(deltaY);
 772       const step = [ deltaX / absDeltaX || 0, deltaY / absDeltaY || 0 ];
 773       if (
 774         // Check that the step is a priori valid:
 775         (absDeltaX != absDeltaY && deltaX != 0 && deltaY != 0) ||
 776         allowedSteps.every(st => st[0] != step[0] || st[1] != step[1])
 777       ) {
 778         return false;
 779       }
 780       let sq = [ x1 + step[0], y1 + step[1] ];
 781       while (sq[0] != x2 || sq[1] != y2) {
 782         if (
 783           // NOTE: no need to check OnBoard in this special case
 784           (!lancer && this.board[sq[0]][sq[1]] != V.EMPTY) ||
 785           (!!lancer && this.getColor(sq[0], sq[1]) == oppCol)
 786         ) {
 787           return false;
 788         }
 789         sq[0] += step[0];
 790         sq[1] += step[1];
 791       }
 792       return true;
 793     };
 794     switch (this.getPiece(x1, y1)) {
 795       case V.PAWN: {
 796         // Pushed pawns move as enemy pawns
 797         const shift = (color == 'w' ? 1 : -1);
 798         return (x1 + shift == x2 && Math.abs(y1 - y2) == 1);
 799       }
 800       case V.KNIGHT: {
 801         const deltaX = Math.abs(x1 - x2);
 802         const deltaY = Math.abs(y1 - y2);
 803         return (
 804           deltaX + deltaY == 3 &&
 805           [1, 2].includes(deltaX) &&
 806           [1, 2].includes(deltaY)
 807         );
 808       }
 809       case V.ROOK:
 810         return sliderAttack(V.steps[V.ROOK]);
 811       case V.BISHOP:
 812         return sliderAttack(V.steps[V.BISHOP]);
 813       case V.QUEEN:
 814         return sliderAttack(V.steps[V.ROOK].concat(V.steps[V.BISHOP]));
 815       case V.LANCER: {
 816         // Special case: as long as no enemy units stands in-between,
 817         // it attacks (if it points toward the king).
 818         const allowedStep = V.LANCER_DIRS[this.board[x1][y1].charAt(1)];
 819         return sliderAttack([allowedStep], "lancer");
 820       }
 821       // No sentries or jailer tests: they cannot self-capture
 822     }
 823     return false;
 824   }
 825
 826   isAttackedBySentry([x, y], color) {
 827     // Attacked by sentry means it can self-take our king.
 828     // Just check diagonals of enemy sentry(ies), and if it reaches
 829     // one of our pieces: can I self-take?
 830     const myColor = V.GetOppCol(color);
 831     let candidates = [];
 832     for (let i=0; i<V.size.x; i++) {
 833       for (let j=0; j<V.size.y; j++) {
 834         if (
 835           this.getPiece(i,j) == V.SENTRY &&
 836           this.getColor(i,j) == color &&
 837           !this.isImmobilized([i, j])
 838         ) {
 839           for (let step of V.steps[V.BISHOP]) {
 840             let sq = [ i + step[0], j + step[1] ];
 841             while (
 842               V.OnBoard(sq[0], sq[1]) &&
 843               this.board[sq[0]][sq[1]] == V.EMPTY
 844             ) {
 845               sq[0] += step[0];
 846               sq[1] += step[1];
 847             }
 848             if (
 849               V.OnBoard(sq[0], sq[1]) &&
 850               this.getColor(sq[0], sq[1]) == myColor
 851             ) {
 852               candidates.push([ sq[0], sq[1] ]);
 853             }
 854           }
 855         }
 856       }
 857     }
 858     for (let c of candidates)
 859       if (this.selfAttack(c, [x, y])) return true;
 860     return false;
 861   }
 862
 863   // Jailer doesn't capture or give check
 864
 865   prePlay(move) {
 866     if (move.appear.length == 0 && move.vanish.length == 1)
 867       // The sentry is about to push a piece: subTurn goes from 1 to 2
 868       this.sentryPos = { x: move.end.x, y: move.end.y };
 869     if (this.subTurn == 2 && move.vanish[0].p != V.PAWN) {
 870       // A piece is pushed: forbid array of squares between start and end
 871       // of move, included (except if it's a pawn)
 872       let squares = [];
 873       if ([V.KNIGHT,V.KING].includes(move.vanish[0].p))
 874         // short-range pieces: just forbid initial square
 875         squares.push({ x: move.start.x, y: move.start.y });
 876       else {
 877         const deltaX = move.end.x - move.start.x;
 878         const deltaY = move.end.y - move.start.y;
 879         const step = [
 880           deltaX / Math.abs(deltaX) || 0,
 881           deltaY / Math.abs(deltaY) || 0
 882         ];
 883         for (
 884           let sq = {x: move.start.x, y: move.start.y};
 885           sq.x != move.end.x || sq.y != move.end.y;
 886           sq.x += step[0], sq.y += step[1]
 887         ) {
 888           squares.push({ x: sq.x, y: sq.y });
 889         }
 890       }
 891       // Add end square as well, to know if I was pushed (useful for lancers)
 892       squares.push({ x: move.end.x, y: move.end.y });
 893       this.sentryPush.push(squares);
 894     } else this.sentryPush.push(null);
 895   }
 896
 897   play(move) {
 898     this.prePlay(move);
 899     move.flags = JSON.stringify(this.aggregateFlags());
 900     this.epSquares.push(this.getEpSquare(move));
 901     V.PlayOnBoard(this.board, move);
 902     // Is it a sentry push? (useful for undo)
 903     move.sentryPush = (this.subTurn == 2);
 904     if (this.subTurn == 1) this.movesCount++;
 905     if (move.appear.length == 0 && move.vanish.length == 1) this.subTurn = 2;
 906     else {
 907       // Turn changes only if not a sentry "pre-push"
 908       this.turn = V.GetOppCol(this.turn);
 909       this.subTurn = 1;
 910     }
 911     this.postPlay(move);
 912   }
 913
 914   postPlay(move) {
 915     if (move.vanish.length == 0 || this.subTurn == 2)
 916       // Special pass move of the king, or sentry pre-push: nothing to update
 917       return;
 918     const c = move.vanish[0].c;
 919     const piece = move.vanish[0].p;
 920     const firstRank = c == "w" ? V.size.x - 1 : 0;
 921
 922     if (piece == V.KING) {
 923       this.kingPos[c][0] = move.appear[0].x;
 924       this.kingPos[c][1] = move.appear[0].y;
 925       this.castleFlags[c] = [V.size.y, V.size.y];
 926       return;
 927     }
 928     // Update castling flags if rooks are moved
 929     const oppCol = V.GetOppCol(c);
 930     const oppFirstRank = V.size.x - 1 - firstRank;
 931     if (
 932       move.start.x == firstRank && //our rook moves?
 933       this.castleFlags[c].includes(move.start.y)
 934     ) {
 935       const flagIdx = (move.start.y == this.castleFlags[c][0] ? 0 : 1);
 936       this.castleFlags[c][flagIdx] = V.size.y;
 937     } else if (
 938       move.end.x == oppFirstRank && //we took opponent rook?
 939       this.castleFlags[oppCol].includes(move.end.y)
 940     ) {
 941       const flagIdx = (move.end.y == this.castleFlags[oppCol][0] ? 0 : 1);
 942       this.castleFlags[oppCol][flagIdx] = V.size.y;
 943     }
 944   }
 945
 946   undo(move) {
 947     this.epSquares.pop();
 948     this.disaggregateFlags(JSON.parse(move.flags));
 949     V.UndoOnBoard(this.board, move);
 950     // Decrement movesCount except if the move is a sentry push
 951     if (!move.sentryPush) this.movesCount--;
 952     if (this.subTurn == 2) this.subTurn = 1;
 953     else {
 954       this.turn = V.GetOppCol(this.turn);
 955       if (move.sentryPush) this.subTurn = 2;
 956     }
 957     this.postUndo(move);
 958   }
 959
 960   postUndo(move) {
 961     super.postUndo(move);
 962     this.sentryPush.pop();
 963   }
 964
 965   static get VALUES() {
 966     return Object.assign(
 967       { l: 4.8, s: 2.8, j: 3.8 }, //Jeff K. estimations
 968       ChessRules.VALUES
 969     );
 970   }
 971
 972   getComputerMove() {
 973     const maxeval = V.INFINITY;
 974     const color = this.turn;
 975     let moves1 = this.getAllValidMoves();
 976
 977     if (moves1.length == 0)
 978       // TODO: this situation should not happen
 979       return null;
 980
 981     const setEval = (move, next) => {
 982       const score = this.getCurrentScore();
 983       const curEval = move.eval;
 984       if (score != "*") {
 985         move.eval =
 986           score == "1/2"
 987             ? 0
 988             : (score == "1-0" ? 1 : -1) * maxeval;
 989       } else move.eval = this.evalPosition();
 990       if (
 991         // "next" is defined after sentry pushes
 992         !!next && (
 993           !curEval ||
 994           color == 'w' && move.eval > curEval ||
 995           color == 'b' && move.eval < curEval
 996         )
 997       ) {
 998         move.second = next;
 999       }
1000     };
1001
1002     // Just search_depth == 1 (because of sentries. TODO: can do better...)
1003     moves1.forEach(m1 => {
1004       this.play(m1);
1005       if (this.subTurn == 1) setEval(m1);
1006       else {
1007         // Need to play every pushes and count:
1008         const moves2 = this.getAllValidMoves();
1009         moves2.forEach(m2 => {
1010           this.play(m2);
1011           setEval(m1, m2);
1012           this.undo(m2);
1013         });
1014       }
1015       this.undo(m1);
1016     });
1017
1018     moves1.sort((a, b) => {
1019       return (color == "w" ? 1 : -1) * (b.eval - a.eval);
1020     });
1021     let candidates = [0];
1022     for (let j = 1; j < moves1.length && moves1[j].eval == moves1[0].eval; j++)
1023       candidates.push(j);
1024     const choice = moves1[candidates[randInt(candidates.length)]];
1025     return (!choice.second ? choice : [choice, choice.second]);
1026   }
1027
1028   // For moves notation:
1029   static get LANCER_DIRNAMES() {
1030     return {
1031       'c': "N",
1032       'd': "NE",
1033       'e': "E",
1034       'f': "SE",
1035       'g': "S",
1036       'h': "SW",
1037       'm': "W",
1038       'o': "NW"
1039     };
1040   }
1041
1042   getNotation(move) {
1043     // Special case "king takes jailer" is a pass move
1044     if (move.appear.length == 0 && move.vanish.length == 0) return "pass";
1045     let notation = undefined;
1046     if (this.subTurn == 2) {
1047       // Do not consider appear[1] (sentry) for sentry pushes
1048       const simpleMove = {
1049         appear: [move.appear[0]],
1050         vanish: move.vanish,
1051         start: move.start,
1052         end: move.end
1053       };
1054       notation = super.getNotation(simpleMove);
1055     } else notation = super.getNotation(move);
1056     if (Object.keys(V.LANCER_DIRNAMES).includes(move.vanish[0].p))
1057       // Lancer: add direction info
1058       notation += "=" + V.LANCER_DIRNAMES[move.appear[0].p];
1059     else if (
1060       move.vanish[0].p == V.PAWN &&
1061       Object.keys(V.LANCER_DIRNAMES).includes(move.appear[0].p)
1062     ) {
1063       // Fix promotions in lancer:
1064       notation = notation.slice(0, -1) +
1065         "L:" + V.LANCER_DIRNAMES[move.appear[0].p];
1066     }
1067     return notation;
1068   }
1069 };