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 const VariantRules = class EightpiecesRules extends ChessRules {
   6   static get JAILER() {
   7     return "j";
   8   }
   9   static get SENTRY() {
  10     return "s";
  11   }
  12   static get LANCER() {
  13     return "l";
  14   }
  15
  16   static get IMAGE_EXTENSION() {
  17     // Temporarily, for the time SVG pieces are being designed:
  18     return ".png";
  19   }
  20
  21   // Lancer directions *from white perspective*
  22   static get LANCER_DIRS() {
  23     return {
  24       'c': [-1, 0], //north
  25       'd': [-1, 1], //N-E
  26       'e': [0, 1], //east
  27       'f': [1, 1], //S-E
  28       'g': [1, 0], //south
  29       'h': [1, -1], //S-W
  30       'm': [0, -1], //west
  31       'o': [-1, -1] //N-W
  32     };
  33   }
  34
  35   static get PIECES() {
  36     return ChessRules.PIECES
  37       .concat([V.JAILER, V.SENTRY])
  38       .concat(Object.keys(V.LANCER_DIRS));
  39   }
  40
  41   getPiece(i, j) {
  42     const piece = this.board[i][j].charAt(1);
  43     // Special lancer case: 8 possible orientations
  44     if (Object.keys(V.LANCER_DIRS).includes(piece)) return V.LANCER;
  45     return piece;
  46   }
  47
  48   getPpath(b, color, score, orientation) {
  49     if ([V.JAILER, V.SENTRY].includes(b[1])) return "Eightpieces/tmp_png/" + b;
  50     if (Object.keys(V.LANCER_DIRS).includes(b[1])) {
  51       if (orientation == 'w') return "Eightpieces/tmp_png/" + b;
  52       // Find opposite direction for adequate display:
  53       let oppDir = '';
  54       switch (b[1]) {
  55         case 'c':
  56           oppDir = 'g';
  57           break;
  58         case 'g':
  59           oppDir = 'c';
  60           break;
  61         case 'd':
  62           oppDir = 'h';
  63           break;
  64         case 'h':
  65           oppDir = 'd';
  66           break;
  67         case 'e':
  68           oppDir = 'm';
  69           break;
  70         case 'm':
  71           oppDir = 'e';
  72           break;
  73         case 'f':
  74           oppDir = 'o';
  75           break;
  76         case 'o':
  77           oppDir = 'f';
  78           break;
  79       }
  80       return "Eightpieces/tmp_png/" + b[0] + oppDir;
  81     }
  82     // TODO: after we have SVG pieces, remove the folder and next prefix:
  83     return "Eightpieces/tmp_png/" + b;
  84   }
  85
  86   getPPpath(b, orientation) {
  87     return this.getPpath(b, null, null, orientation);
  88   }
  89
  90   static ParseFen(fen) {
  91     const fenParts = fen.split(" ");
  92     return Object.assign(
  93       ChessRules.ParseFen(fen),
  94       { sentrypush: fenParts[5] }
  95     );
  96   }
  97
  98   static IsGoodFen(fen) {
  99     if (!ChessRules.IsGoodFen(fen)) return false;
 100     const fenParsed = V.ParseFen(fen);
 101     // 5) Check sentry push (if any)
 102     if (
 103       fenParsed.sentrypush != "-" &&
 104       !fenParsed.sentrypush.match(/^([a-h][1-8],?)+$/)
 105     ) {
 106       return false;
 107     }
 108     return true;
 109   }
 110
 111   getFen() {
 112     return super.getFen() + " " + this.getSentrypushFen();
 113   }
 114
 115   getFenForRepeat() {
 116     return super.getFenForRepeat() + "_" + this.getSentrypushFen();
 117   }
 118
 119   getSentrypushFen() {
 120     const L = this.sentryPush.length;
 121     if (!this.sentryPush[L-1]) return "-";
 122     let res = "";
 123     this.sentryPush[L-1].forEach(coords =>
 124       res += V.CoordsToSquare(coords) + ",");
 125     return res.slice(0, -1);
 126   }
 127
 128   setOtherVariables(fen) {
 129     super.setOtherVariables(fen);
 130     // subTurn == 2 only when a sentry moved, and is about to push something
 131     this.subTurn = 1;
 132     // Sentry position just after a "capture" (subTurn from 1 to 2)
 133     this.sentryPos = null;
 134     // Stack pieces' forbidden squares after a sentry move at each turn
 135     const parsedFen = V.ParseFen(fen);
 136     if (parsedFen.sentrypush == "-") this.sentryPush = [null];
 137     else {
 138       this.sentryPush = [
 139         parsedFen.sentrypush.split(",").map(sq => {
 140           return V.SquareToCoords(sq);
 141         })
 142       ];
 143     }
 144   }
 145
 146   static GenRandInitFen(randomness) {
 147     if (randomness == 0)
 148       // Deterministic:
 149       return "jsfqkbnr/pppppppp/8/8/8/8/PPPPPPPP/JSDQKBNR w 0 ahah - -";
 150
 151     let pieces = { w: new Array(8), b: new Array(8) };
 152     let flags = "";
 153     // Shuffle pieces on first (and last rank if randomness == 2)
 154     for (let c of ["w", "b"]) {
 155       if (c == 'b' && randomness == 1) {
 156         const lancerIdx = pieces['w'].findIndex(p => {
 157           return Object.keys(V.LANCER_DIRS).includes(p);
 158         });
 159         pieces['b'] =
 160           pieces['w'].slice(0, lancerIdx)
 161           .concat(['g'])
 162           .concat(pieces['w'].slice(lancerIdx + 1));
 163         flags += flags;
 164         break;
 165       }
 166
 167       let positions = ArrayFun.range(8);
 168
 169       // Get random squares for bishop and sentry
 170       let randIndex = 2 * randInt(4);
 171       let bishopPos = positions[randIndex];
 172       // The sentry must be on a square of different color
 173       let randIndex_tmp = 2 * randInt(4) + 1;
 174       let sentryPos = positions[randIndex_tmp];
 175       if (c == 'b') {
 176         // Check if white sentry is on the same color as ours.
 177         // If yes: swap bishop and sentry positions.
 178         if ((pieces['w'].indexOf('s') - sentryPos) % 2 == 0)
 179           [bishopPos, sentryPos] = [sentryPos, bishopPos];
 180       }
 181       positions.splice(Math.max(randIndex, randIndex_tmp), 1);
 182       positions.splice(Math.min(randIndex, randIndex_tmp), 1);
 183
 184       // Get random squares for knight and lancer
 185       randIndex = randInt(6);
 186       const knightPos = positions[randIndex];
 187       positions.splice(randIndex, 1);
 188       randIndex = randInt(5);
 189       const lancerPos = positions[randIndex];
 190       positions.splice(randIndex, 1);
 191
 192       // Get random square for queen
 193       randIndex = randInt(4);
 194       const queenPos = positions[randIndex];
 195       positions.splice(randIndex, 1);
 196
 197       // Rook, jailer and king positions are now almost fixed,
 198       // only the ordering rook-> jailer or jailer->rook must be decided.
 199       let rookPos = positions[0];
 200       let jailerPos = positions[2];
 201       const kingPos = positions[1];
 202       flags += V.CoordToColumn(rookPos) + V.CoordToColumn(jailerPos);
 203       if (Math.random() < 0.5) [rookPos, jailerPos] = [jailerPos, rookPos];
 204
 205       pieces[c][rookPos] = "r";
 206       pieces[c][knightPos] = "n";
 207       pieces[c][bishopPos] = "b";
 208       pieces[c][queenPos] = "q";
 209       pieces[c][kingPos] = "k";
 210       pieces[c][sentryPos] = "s";
 211       // Lancer faces north for white, and south for black:
 212       pieces[c][lancerPos] = c == 'w' ? 'c' : 'g';
 213       pieces[c][jailerPos] = "j";
 214     }
 215     return (
 216       pieces["b"].join("") +
 217       "/pppppppp/8/8/8/8/PPPPPPPP/" +
 218       pieces["w"].join("").toUpperCase() +
 219       " w 0 " + flags + " - -"
 220     );
 221   }
 222
 223   canTake([x1, y1], [x2, y2]) {
 224     if (this.subTurn == 2)
 225       // Only self captures on this subturn:
 226       return this.getColor(x1, y1) == this.getColor(x2, y2);
 227     return super.canTake([x1, y1], [x2, y2]);
 228   }
 229
 230   // Is piece on square (x,y) immobilized?
 231   isImmobilized([x, y]) {
 232     const color = this.getColor(x, y);
 233     const oppCol = V.GetOppCol(color);
 234     for (let step of V.steps[V.ROOK]) {
 235       const [i, j] = [x + step[0], y + step[1]];
 236       if (
 237         V.OnBoard(i, j) &&
 238         this.board[i][j] != V.EMPTY &&
 239         this.getColor(i, j) == oppCol
 240       ) {
 241         if (this.getPiece(i, j) == V.JAILER) return [i, j];
 242       }
 243     }
 244     return null;
 245   }
 246
 247   // Because of the lancers, getPiece() could be wrong:
 248   // use board[x][y][1] instead (always valid).
 249   getBasicMove([sx, sy], [ex, ey], tr) {
 250     let mv = new Move({
 251       appear: [
 252         new PiPo({
 253           x: ex,
 254           y: ey,
 255           c: tr ? tr.c : this.getColor(sx, sy),
 256           p: tr ? tr.p : this.board[sx][sy].charAt(1)
 257         })
 258       ],
 259       vanish: [
 260         new PiPo({
 261           x: sx,
 262           y: sy,
 263           c: this.getColor(sx, sy),
 264           p: this.board[sx][sy].charAt(1)
 265         })
 266       ]
 267     });
 268
 269     // The opponent piece disappears if we take it
 270     if (this.board[ex][ey] != V.EMPTY) {
 271       mv.vanish.push(
 272         new PiPo({
 273           x: ex,
 274           y: ey,
 275           c: this.getColor(ex, ey),
 276           p: this.board[ex][ey].charAt(1)
 277         })
 278       );
 279     }
 280
 281     return mv;
 282   }
 283
 284   canIplay(side, [x, y]) {
 285     return (
 286       (this.subTurn == 1 && this.turn == side && this.getColor(x, y) == side) ||
 287       (this.subTurn == 2 && x == this.sentryPos.x && y == this.sentryPos.y)
 288     );
 289   }
 290
 291   getPotentialMovesFrom([x, y]) {
 292     // At subTurn == 2, jailers aren't effective (Jeff K)
 293     const piece = this.getPiece(x, y);
 294     const L = this.sentryPush.length;
 295     if (this.subTurn == 1) {
 296       const jsq = this.isImmobilized([x, y]);
 297       if (!!jsq) {
 298         let moves = [];
 299         // Special pass move if king:
 300         if (piece == V.KING) {
 301           moves.push(
 302             new Move({
 303               appear: [],
 304               vanish: [],
 305               start: { x: x, y: y },
 306               end: { x: jsq[0], y: jsq[1] }
 307             })
 308           );
 309         }
 310         else if (piece == V.LANCER && !!this.sentryPush[L-1]) {
 311           // A pushed lancer next to the jailer: reorient
 312           const color = this.getColor(x, y);
 313           const curDir = this.board[x][y].charAt(1);
 314           Object.keys(V.LANCER_DIRS).forEach(k => {
 315             moves.push(
 316               new Move({
 317                 appear: [{ x: x, y: y, c: color, p: k }],
 318                 vanish: [{ x: x, y: y, c: color, p: curDir }],
 319                 start: { x: x, y: y },
 320                 end: { x: jsq[0], y: jsq[1] }
 321               })
 322             );
 323           });
 324         }
 325         return moves;
 326       }
 327     }
 328     let moves = [];
 329     switch (piece) {
 330       case V.JAILER:
 331         moves = this.getPotentialJailerMoves([x, y]);
 332         break;
 333       case V.SENTRY:
 334         moves = this.getPotentialSentryMoves([x, y]);
 335         break;
 336       case V.LANCER:
 337         moves = this.getPotentialLancerMoves([x, y]);
 338         break;
 339       default:
 340         moves = super.getPotentialMovesFrom([x, y]);
 341         break;
 342     }
 343     if (!!this.sentryPush[L-1]) {
 344       // Delete moves walking back on sentry push path,
 345       // only if not a pawn, and the piece is the pushed one.
 346       const pl = this.sentryPush[L-1].length;
 347       const finalPushedSq = this.sentryPush[L-1][pl-1];
 348       moves = moves.filter(m => {
 349         if (
 350           m.vanish[0].p != V.PAWN &&
 351           m.start.x == finalPushedSq.x && m.start.y == finalPushedSq.y &&
 352           this.sentryPush[L-1].some(sq => sq.x == m.end.x && sq.y == m.end.y)
 353         ) {
 354           return false;
 355         }
 356         return true;
 357       });
 358     } else if (this.subTurn == 2) {
 359       // Put back the sentinel on board:
 360       const color = this.turn;
 361       moves.forEach(m => {
 362         m.appear.push({x: x, y: y, p: V.SENTRY, c: color});
 363       });
 364     }
 365     return moves;
 366   }
 367
 368   getPotentialPawnMoves([x, y]) {
 369     const color = this.getColor(x, y);
 370     let moves = [];
 371     const [sizeX, sizeY] = [V.size.x, V.size.y];
 372     let shiftX = (color == "w" ? -1 : 1);
 373     if (this.subTurn == 2) shiftX *= -1;
 374     const firstRank = color == "w" ? sizeX - 1 : 0;
 375     const startRank = color == "w" ? sizeX - 2 : 1;
 376     const lastRank = color == "w" ? 0 : sizeX - 1;
 377
 378     // Pawns might be pushed on 1st rank and attempt to move again:
 379     if (!V.OnBoard(x + shiftX, y)) return [];
 380
 381     const finalPieces =
 382       // A push cannot put a pawn on last rank (it goes backward)
 383       x + shiftX == lastRank
 384         ? Object.keys(V.LANCER_DIRS).concat(
 385           [V.ROOK, V.KNIGHT, V.BISHOP, V.QUEEN, V.SENTRY, V.JAILER])
 386         : [V.PAWN];
 387     if (this.board[x + shiftX][y] == V.EMPTY) {
 388       // One square forward
 389       for (let piece of finalPieces) {
 390         moves.push(
 391           this.getBasicMove([x, y], [x + shiftX, y], {
 392             c: color,
 393             p: piece
 394           })
 395         );
 396       }
 397       if (
 398         // 2-squares jumps forbidden if pawn push
 399         this.subTurn == 1 &&
 400         [startRank, firstRank].includes(x) &&
 401         this.board[x + 2 * shiftX][y] == V.EMPTY
 402       ) {
 403         // Two squares jump
 404         moves.push(this.getBasicMove([x, y], [x + 2 * shiftX, y]));
 405       }
 406     }
 407     // Captures
 408     for (let shiftY of [-1, 1]) {
 409       if (
 410         y + shiftY >= 0 &&
 411         y + shiftY < sizeY &&
 412         this.board[x + shiftX][y + shiftY] != V.EMPTY &&
 413         this.canTake([x, y], [x + shiftX, y + shiftY])
 414       ) {
 415         for (let piece of finalPieces) {
 416           moves.push(
 417             this.getBasicMove([x, y], [x + shiftX, y + shiftY], {
 418               c: color,
 419               p: piece
 420             })
 421           );
 422         }
 423       }
 424     }
 425
 426     // En passant: only on subTurn == 1
 427     const Lep = this.epSquares.length;
 428     const epSquare = this.epSquares[Lep - 1];
 429     if (
 430       this.subTurn == 1 &&
 431       !!epSquare &&
 432       epSquare.x == x + shiftX &&
 433       Math.abs(epSquare.y - y) == 1
 434     ) {
 435       let enpassantMove = this.getBasicMove([x, y], [epSquare.x, epSquare.y]);
 436       enpassantMove.vanish.push({
 437         x: x,
 438         y: epSquare.y,
 439         p: "p",
 440         c: this.getColor(x, epSquare.y)
 441       });
 442       moves.push(enpassantMove);
 443     }
 444
 445     return moves;
 446   }
 447
 448   // Obtain all lancer moves in "step" direction
 449   getPotentialLancerMoves_aux([x, y], step, tr) {
 450     let moves = [];
 451     // Add all moves to vacant squares until opponent is met:
 452     const color = this.getColor(x, y);
 453     const oppCol =
 454       this.subTurn == 1
 455         ? V.GetOppCol(color)
 456         // at subTurn == 2, consider own pieces as opponent
 457         : color;
 458     let sq = [x + step[0], y + step[1]];
 459     while (V.OnBoard(sq[0], sq[1]) && this.getColor(sq[0], sq[1]) != oppCol) {
 460       if (this.board[sq[0]][sq[1]] == V.EMPTY)
 461         moves.push(this.getBasicMove([x, y], sq, tr));
 462       sq[0] += step[0];
 463       sq[1] += step[1];
 464     }
 465     if (V.OnBoard(sq[0], sq[1]))
 466       // Add capturing move
 467       moves.push(this.getBasicMove([x, y], sq, tr));
 468     return moves;
 469   }
 470
 471   getPotentialLancerMoves([x, y]) {
 472     let moves = [];
 473     // Add all lancer possible orientations, similar to pawn promotions.
 474     // Except if just after a push: allow all movements from init square then
 475     const L = this.sentryPush.length;
 476     const color = this.getColor(x, y);
 477     if (!!this.sentryPush[L-1]) {
 478       // Maybe I was pushed
 479       const pl = this.sentryPush[L-1].length;
 480       if (
 481         this.sentryPush[L-1][pl-1].x == x &&
 482         this.sentryPush[L-1][pl-1].y == y
 483       ) {
 484         // I was pushed: allow all directions (for this move only), but
 485         // do not change direction after moving, *except* if I keep the
 486         // same orientation in which I was pushed.
 487         const curDir = V.LANCER_DIRS[this.board[x][y].charAt(1)];
 488         Object.values(V.LANCER_DIRS).forEach(step => {
 489           const dirCode = Object.keys(V.LANCER_DIRS).find(k => {
 490             return (
 491               V.LANCER_DIRS[k][0] == step[0] &&
 492               V.LANCER_DIRS[k][1] == step[1]
 493             );
 494           });
 495           const dirMoves =
 496             this.getPotentialLancerMoves_aux(
 497               [x, y],
 498               step,
 499               { p: dirCode, c: color }
 500             );
 501           if (curDir[0] == step[0] && curDir[1] == step[1]) {
 502             // Keeping same orientation: can choose after
 503             let chooseMoves = [];
 504             dirMoves.forEach(m => {
 505               Object.keys(V.LANCER_DIRS).forEach(k => {
 506                 let mk = JSON.parse(JSON.stringify(m));
 507                 mk.appear[0].p = k;
 508                 moves.push(mk);
 509               });
 510             });
 511             Array.prototype.push.apply(moves, chooseMoves);
 512           } else Array.prototype.push.apply(moves, dirMoves);
 513         });
 514         return moves;
 515       }
 516     }
 517     // I wasn't pushed: standard lancer move
 518     const dirCode = this.board[x][y][1];
 519     const monodirMoves =
 520       this.getPotentialLancerMoves_aux([x, y], V.LANCER_DIRS[dirCode]);
 521     // Add all possible orientations aftermove except if I'm being pushed
 522     if (this.subTurn == 1) {
 523       monodirMoves.forEach(m => {
 524         Object.keys(V.LANCER_DIRS).forEach(k => {
 525           let mk = JSON.parse(JSON.stringify(m));
 526           mk.appear[0].p = k;
 527           moves.push(mk);
 528         });
 529       });
 530       return moves;
 531     } else {
 532       // I'm pushed: add potential nudges
 533       let potentialNudges = [];
 534       for (let step of V.steps[V.ROOK].concat(V.steps[V.BISHOP])) {
 535         if (
 536           V.OnBoard(x + step[0], y + step[1]) &&
 537           this.board[x + step[0]][y + step[1]] == V.EMPTY
 538         ) {
 539           const newDirCode = Object.keys(V.LANCER_DIRS).find(k => {
 540             const codeStep = V.LANCER_DIRS[k];
 541             return (codeStep[0] == step[0] && codeStep[1] == step[1]);
 542           });
 543           potentialNudges.push(
 544             this.getBasicMove(
 545               [x, y],
 546               [x + step[0], y + step[1]],
 547               { c: color, p: newDirCode }
 548             )
 549           );
 550         }
 551       }
 552       return monodirMoves.concat(potentialNudges);
 553     }
 554   }
 555
 556   getPotentialSentryMoves([x, y]) {
 557     // The sentry moves a priori like a bishop:
 558     let moves = super.getPotentialBishopMoves([x, y]);
 559     // ...but captures are replaced by special move, if and only if
 560     // "captured" piece can move now, considered as the capturer unit.
 561     // --> except is subTurn == 2, in this case I don't push anything.
 562     if (this.subTurn == 2) return moves.filter(m => m.vanish.length == 1);
 563     moves.forEach(m => {
 564       if (m.vanish.length == 2) {
 565         // Temporarily cancel the sentry capture:
 566         m.appear.pop();
 567         m.vanish.pop();
 568       }
 569     });
 570     const color = this.getColor(x, y);
 571     const fMoves = moves.filter(m => {
 572       // Can the pushed unit make any move? ...resulting in a non-self-check?
 573       if (m.appear.length == 0) {
 574         let res = false;
 575         this.play(m);
 576         let moves2 = this.getPotentialMovesFrom([m.end.x, m.end.y]);
 577         for (let m2 of moves2) {
 578           this.play(m2);
 579           res = !this.underCheck(color);
 580           this.undo(m2);
 581           if (res) break;
 582         }
 583         this.undo(m);
 584         return res;
 585       }
 586       return true;
 587     });
 588     return fMoves;
 589   }
 590
 591   getPotentialJailerMoves([x, y]) {
 592     return super.getPotentialRookMoves([x, y]).filter(m => {
 593       // Remove jailer captures
 594       return m.vanish[0].p != V.JAILER || m.vanish.length == 1;
 595     });
 596   }
 597
 598   getPotentialKingMoves(sq) {
 599     const moves = this.getSlideNJumpMoves(
 600       sq,
 601       V.steps[V.ROOK].concat(V.steps[V.BISHOP]),
 602       "oneStep"
 603     );
 604     return (
 605       this.subTurn == 1
 606         ? moves.concat(this.getCastleMoves(sq))
 607         : moves
 608     );
 609   }
 610
 611   // Adapted: castle with jailer possible
 612   getCastleMoves([x, y]) {
 613     const c = this.getColor(x, y);
 614     const firstRank = (c == "w" ? V.size.x - 1 : 0);
 615     if (x != firstRank || y != this.INIT_COL_KING[c])
 616       return [];
 617
 618     const oppCol = V.GetOppCol(c);
 619     let moves = [];
 620     let i = 0;
 621     // King, then rook or jailer:
 622     const finalSquares = [
 623       [2, 3],
 624       [V.size.y - 2, V.size.y - 3]
 625     ];
 626     castlingCheck: for (
 627       let castleSide = 0;
 628       castleSide < 2;
 629       castleSide++
 630     ) {
 631       if (this.castleFlags[c][castleSide] >= 8) continue;
 632       // Rook (or jailer) and king are on initial position
 633       const finDist = finalSquares[castleSide][0] - y;
 634       let step = finDist / Math.max(1, Math.abs(finDist));
 635       i = y;
 636       do {
 637         if (
 638           this.isAttacked([x, i], oppCol) ||
 639           (this.board[x][i] != V.EMPTY &&
 640             (this.getColor(x, i) != c ||
 641               ![V.KING, V.ROOK, V.JAILER].includes(this.getPiece(x, i))))
 642         ) {
 643           continue castlingCheck;
 644         }
 645         i += step;
 646       } while (i != finalSquares[castleSide][0]);
 647       step = castleSide == 0 ? -1 : 1;
 648       const rookOrJailerPos = this.castleFlags[c][castleSide];
 649       for (i = y + step; i != rookOrJailerPos; i += step)
 650         if (this.board[x][i] != V.EMPTY) continue castlingCheck;
 651
 652       // Nothing on final squares, except maybe king and castling rook or jailer?
 653       for (i = 0; i < 2; i++) {
 654         if (
 655           this.board[x][finalSquares[castleSide][i]] != V.EMPTY &&
 656           this.getPiece(x, finalSquares[castleSide][i]) != V.KING &&
 657           finalSquares[castleSide][i] != rookOrJailerPos
 658         ) {
 659           continue castlingCheck;
 660         }
 661       }
 662
 663       // If this code is reached, castle is valid
 664       const castlingPiece = this.getPiece(firstRank, rookOrJailerPos);
 665       moves.push(
 666         new Move({
 667           appear: [
 668             new PiPo({ x: x, y: finalSquares[castleSide][0], p: V.KING, c: c }),
 669             new PiPo({ x: x, y: finalSquares[castleSide][1], p: castlingPiece, c: c })
 670           ],
 671           vanish: [
 672             new PiPo({ x: x, y: y, p: V.KING, c: c }),
 673             new PiPo({ x: x, y: rookOrJailerPos, p: castlingPiece, c: c })
 674           ],
 675           end:
 676             Math.abs(y - rookOrJailerPos) <= 2
 677               ? { x: x, y: rookOrJailerPos }
 678               : { x: x, y: y + 2 * (castleSide == 0 ? -1 : 1) }
 679         })
 680       );
 681     }
 682
 683     return moves;
 684   }
 685
 686   atLeastOneMove() {
 687     // If in second-half of a move, we already know that a move is possible
 688     if (this.subTurn == 2) return true;
 689     return super.atLeastOneMove();
 690   }
 691
 692   filterValid(moves) {
 693     if (moves.length == 0) return [];
 694     const basicFilter = (m, c) => {
 695       this.play(m);
 696       const res = !this.underCheck(c);
 697       this.undo(m);
 698       return res;
 699     };
 700     // Disable check tests for sentry pushes,
 701     // because in this case the move isn't finished
 702     let movesWithoutSentryPushes = [];
 703     let movesWithSentryPushes = [];
 704     moves.forEach(m => {
 705       // Second condition below for special king "pass" moves
 706       if (m.appear.length > 0 || m.vanish.length == 0)
 707         movesWithoutSentryPushes.push(m);
 708       else movesWithSentryPushes.push(m);
 709     });
 710     const color = this.turn;
 711     const oppCol = V.GetOppCol(color);
 712     const filteredMoves =
 713       movesWithoutSentryPushes.filter(m => basicFilter(m, color));
 714     // If at least one full move made, everything is allowed.
 715     // Else: forbid checks and captures.
 716     return (
 717       this.movesCount >= 2
 718         ? filteredMoves
 719         : filteredMoves.filter(m => {
 720           return (m.vanish.length <= 1 && basicFilter(m, oppCol));
 721         })
 722     ).concat(movesWithSentryPushes);
 723   }
 724
 725   getAllValidMoves() {
 726     if (this.subTurn == 1) return super.getAllValidMoves();
 727     // Sentry push:
 728     const sentrySq = [this.sentryPos.x, this.sentryPos.y];
 729     return this.filterValid(this.getPotentialMovesFrom(sentrySq));
 730   }
 731
 732   prePlay(move) {
 733     if (move.appear.length == 0 && move.vanish.length == 1)
 734       // The sentry is about to push a piece: subTurn goes from 1 to 2
 735       this.sentryPos = { x: move.end.x, y: move.end.y };
 736     if (this.subTurn == 2 && move.vanish[0].p != V.PAWN) {
 737       // A piece is pushed: forbid array of squares between start and end
 738       // of move, included (except if it's a pawn)
 739       let squares = [];
 740       if ([V.KNIGHT,V.KING].includes(move.vanish[0].p))
 741         // short-range pieces: just forbid initial square
 742         squares.push({ x: move.start.x, y: move.start.y });
 743       else {
 744         const deltaX = move.end.x - move.start.x;
 745         const deltaY = move.end.y - move.start.y;
 746         const step = [
 747           deltaX / Math.abs(deltaX) || 0,
 748           deltaY / Math.abs(deltaY) || 0
 749         ];
 750         for (
 751           let sq = {x: move.start.x, y: move.start.y};
 752           sq.x != move.end.x || sq.y != move.end.y;
 753           sq.x += step[0], sq.y += step[1]
 754         ) {
 755           squares.push({ x: sq.x, y: sq.y });
 756         }
 757       }
 758       // Add end square as well, to know if I was pushed (useful for lancers)
 759       squares.push({ x: move.end.x, y: move.end.y });
 760       this.sentryPush.push(squares);
 761     } else this.sentryPush.push(null);
 762   }
 763
 764   play(move) {
 765 //    if (!this.states) this.states = [];
 766 //    const stateFen = this.getFen();
 767 //    this.states.push(stateFen);
 768
 769     this.prePlay(move);
 770     move.flags = JSON.stringify(this.aggregateFlags());
 771     this.epSquares.push(this.getEpSquare(move));
 772     V.PlayOnBoard(this.board, move);
 773     // Is it a sentry push? (useful for undo)
 774     move.sentryPush = (this.subTurn == 2);
 775     if (this.subTurn == 1) this.movesCount++;
 776     if (move.appear.length == 0 && move.vanish.length == 1) this.subTurn = 2;
 777     else {
 778       // Turn changes only if not a sentry "pre-push"
 779       this.turn = V.GetOppCol(this.turn);
 780       this.subTurn = 1;
 781     }
 782     this.postPlay(move);
 783   }
 784
 785   postPlay(move) {
 786     if (move.vanish.length == 0 || this.subTurn == 2)
 787       // Special pass move of the king, or sentry pre-push: nothing to update
 788       return;
 789     const c = move.vanish[0].c;
 790     const piece = move.vanish[0].p;
 791     const firstRank = c == "w" ? V.size.x - 1 : 0;
 792
 793     if (piece == V.KING) {
 794       this.kingPos[c][0] = move.appear[0].x;
 795       this.kingPos[c][1] = move.appear[0].y;
 796       this.castleFlags[c] = [V.size.y, V.size.y];
 797       return;
 798     }
 799     // Update castling flags if rooks are moved
 800     const oppCol = V.GetOppCol(c);
 801     const oppFirstRank = V.size.x - 1 - firstRank;
 802     if (
 803       move.start.x == firstRank && //our rook moves?
 804       this.castleFlags[c].includes(move.start.y)
 805     ) {
 806       const flagIdx = (move.start.y == this.castleFlags[c][0] ? 0 : 1);
 807       this.castleFlags[c][flagIdx] = V.size.y;
 808     } else if (
 809       move.end.x == oppFirstRank && //we took opponent rook?
 810       this.castleFlags[oppCol].includes(move.end.y)
 811     ) {
 812       const flagIdx = (move.end.y == this.castleFlags[oppCol][0] ? 0 : 1);
 813       this.castleFlags[oppCol][flagIdx] = V.size.y;
 814     }
 815   }
 816
 817   undo(move) {
 818     this.epSquares.pop();
 819     this.disaggregateFlags(JSON.parse(move.flags));
 820     V.UndoOnBoard(this.board, move);
 821     // Decrement movesCount except if the move is a sentry push
 822     if (!move.sentryPush) this.movesCount--;
 823     if (this.subTurn == 2) this.subTurn = 1;
 824     else {
 825       this.turn = V.GetOppCol(this.turn);
 826       if (move.sentryPush) this.subTurn = 2;
 827     }
 828     this.postUndo(move);
 829
 830 //    const stateFen = this.getFen();
 831 //    if (stateFen != this.states[this.states.length-1]) debugger;
 832 //    this.states.pop();
 833   }
 834
 835   postUndo(move) {
 836     super.postUndo(move);
 837     this.sentryPush.pop();
 838   }
 839
 840   isAttacked(sq, color) {
 841     return (
 842       super.isAttacked(sq, color) ||
 843       this.isAttackedByLancer(sq, color) ||
 844       this.isAttackedBySentry(sq, color)
 845     );
 846   }
 847
 848   isAttackedBySlideNJump([x, y], color, piece, steps, oneStep) {
 849     for (let step of steps) {
 850       let rx = x + step[0],
 851           ry = y + step[1];
 852       while (V.OnBoard(rx, ry) && this.board[rx][ry] == V.EMPTY && !oneStep) {
 853         rx += step[0];
 854         ry += step[1];
 855       }
 856       if (
 857         V.OnBoard(rx, ry) &&
 858         this.getPiece(rx, ry) == piece &&
 859         this.getColor(rx, ry) == color &&
 860         !this.isImmobilized([rx, ry])
 861       ) {
 862         return true;
 863       }
 864     }
 865     return false;
 866   }
 867
 868   isAttackedByPawn([x, y], color) {
 869     const pawnShift = (color == "w" ? 1 : -1);
 870     if (x + pawnShift >= 0 && x + pawnShift < V.size.x) {
 871       for (let i of [-1, 1]) {
 872         if (
 873           y + i >= 0 &&
 874           y + i < V.size.y &&
 875           this.getPiece(x + pawnShift, y + i) == V.PAWN &&
 876           this.getColor(x + pawnShift, y + i) == color &&
 877           !this.isImmobilized([x + pawnShift, y + i])
 878         ) {
 879           return true;
 880         }
 881       }
 882     }
 883     return false;
 884   }
 885
 886   isAttackedByLancer([x, y], color) {
 887     for (let step of V.steps[V.ROOK].concat(V.steps[V.BISHOP])) {
 888       // If in this direction there are only enemy pieces and empty squares,
 889       // and we meet a lancer: can he reach us?
 890       // NOTE: do not stop at first lancer, there might be several!
 891       let coord = { x: x + step[0], y: y + step[1] };
 892       let lancerPos = [];
 893       while (
 894         V.OnBoard(coord.x, coord.y) &&
 895         (
 896           this.board[coord.x][coord.y] == V.EMPTY ||
 897           this.getColor(coord.x, coord.y) == color
 898         )
 899       ) {
 900         if (
 901           this.getPiece(coord.x, coord.y) == V.LANCER &&
 902           !this.isImmobilized([coord.x, coord.y])
 903         ) {
 904           lancerPos.push({x: coord.x, y: coord.y});
 905         }
 906         coord.x += step[0];
 907         coord.y += step[1];
 908       }
 909       for (let xy of lancerPos) {
 910         const dir = V.LANCER_DIRS[this.board[xy.x][xy.y].charAt(1)];
 911         if (dir[0] == -step[0] && dir[1] == -step[1]) return true;
 912       }
 913     }
 914     return false;
 915   }
 916
 917   // Helper to check sentries attacks:
 918   selfAttack([x1, y1], [x2, y2]) {
 919     const color = this.getColor(x1, y1);
 920     const sliderAttack = (allowedSteps, lancer) => {
 921       const deltaX = x2 - x1,
 922             absDeltaX = Math.abs(deltaX);
 923       const deltaY = y2 - y1,
 924             absDeltaY = Math.abs(deltaY);
 925       const step = [ deltaX / absDeltaX || 0, deltaY / absDeltaY || 0 ];
 926       if (
 927         // Check that the step is a priori valid:
 928         (absDeltaX != absDeltaY && deltaX != 0 && deltaY != 0) ||
 929         allowedSteps.every(st => st[0] != step[0] || st[1] != step[1])
 930       ) {
 931         return false;
 932       }
 933       let sq = [ x1 + step[0], y1 + step[1] ];
 934       while (sq[0] != x2 || sq[1] != y2) {
 935         if (
 936           // NOTE: no need to check OnBoard in this special case
 937           (!lancer && this.board[sq[0]][sq[1]] != V.EMPTY) ||
 938           (!!lancer && this.getColor(sq[0], sq[1]) != color)
 939         ) {
 940           return false;
 941         }
 942         sq[0] += step[0];
 943         sq[1] += step[1];
 944       }
 945       return true;
 946     };
 947     switch (this.getPiece(x1, y1)) {
 948       case V.PAWN: {
 949         // Pushed pawns move as enemy pawns
 950         const shift = (color == 'w' ? 1 : -1);
 951         return (x1 + shift == x2 && Math.abs(y1 - y2) == 1);
 952       }
 953       case V.KNIGHT: {
 954         const deltaX = Math.abs(x1 - x2);
 955         const deltaY = Math.abs(y1 - y2);
 956         return (
 957           deltaX + deltaY == 3 &&
 958           [1, 2].includes(deltaX) &&
 959           [1, 2].includes(deltaY)
 960         );
 961       }
 962       case V.ROOK:
 963         return sliderAttack(V.steps[V.ROOK]);
 964       case V.BISHOP:
 965         return sliderAttack(V.steps[V.BISHOP]);
 966       case V.QUEEN:
 967         return sliderAttack(V.steps[V.ROOK].concat(V.steps[V.BISHOP]));
 968       case V.LANCER: {
 969         // Special case: as long as no enemy units stands in-between, it attacks
 970         // (if it points toward the king).
 971         const allowedStep = V.LANCER_DIRS[this.board[x1][y1].charAt(1)];
 972         return sliderAttack([allowedStep], "lancer");
 973       }
 974       // No sentries or jailer tests: they cannot self-capture
 975     }
 976     return false;
 977   }
 978
 979   isAttackedBySentry([x, y], color) {
 980     // Attacked by sentry means it can self-take our king.
 981     // Just check diagonals of enemy sentry(ies), and if it reaches
 982     // one of our pieces: can I self-take?
 983     const myColor = V.GetOppCol(color);
 984     let candidates = [];
 985     for (let i=0; i<V.size.x; i++) {
 986       for (let j=0; j<V.size.y; j++) {
 987         if (
 988           this.getPiece(i,j) == V.SENTRY &&
 989           this.getColor(i,j) == color &&
 990           !this.isImmobilized([i, j])
 991         ) {
 992           for (let step of V.steps[V.BISHOP]) {
 993             let sq = [ i + step[0], j + step[1] ];
 994             while (
 995               V.OnBoard(sq[0], sq[1]) &&
 996               this.board[sq[0]][sq[1]] == V.EMPTY
 997             ) {
 998               sq[0] += step[0];
 999               sq[1] += step[1];
1000             }
1001             if (
1002               V.OnBoard(sq[0], sq[1]) &&
1003               this.getColor(sq[0], sq[1]) == myColor
1004             ) {
1005               candidates.push([ sq[0], sq[1] ]);
1006             }
1007           }
1008         }
1009       }
1010     }
1011     for (let c of candidates)
1012       if (this.selfAttack(c, [x, y])) return true;
1013     return false;
1014   }
1015
1016   // Jailer doesn't capture or give check
1017
1018   static get VALUES() {
1019     return Object.assign(
1020       { l: 4.8, s: 2.8, j: 3.8 }, //Jeff K. estimations
1021       ChessRules.VALUES
1022     );
1023   }
1024
1025   getComputerMove() {
1026     const maxeval = V.INFINITY;
1027     const color = this.turn;
1028     let moves1 = this.getAllValidMoves();
1029
1030     if (moves1.length == 0)
1031       // TODO: this situation should not happen
1032       return null;
1033
1034     const setEval = (move, next) => {
1035       const score = this.getCurrentScore();
1036       const curEval = move.eval;
1037       if (score != "*") {
1038         move.eval =
1039           score == "1/2"
1040             ? 0
1041             : (score == "1-0" ? 1 : -1) * maxeval;
1042       } else move.eval = this.evalPosition();
1043       if (
1044         // "next" is defined after sentry pushes
1045         !!next && (
1046           !curEval ||
1047           color == 'w' && move.eval > curEval ||
1048           color == 'b' && move.eval < curEval
1049         )
1050       ) {
1051         move.second = next;
1052       }
1053     };
1054
1055     // Just search_depth == 1 (because of sentries. TODO: can do better...)
1056     moves1.forEach(m1 => {
1057       this.play(m1);
1058       if (this.subTurn == 1) setEval(m1);
1059       else {
1060         // Need to play every pushes and count:
1061         const moves2 = this.getAllValidMoves();
1062         moves2.forEach(m2 => {
1063           this.play(m2);
1064           setEval(m1, m2);
1065           this.undo(m2);
1066         });
1067       }
1068       this.undo(m1);
1069     });
1070
1071     moves1.sort((a, b) => {
1072       return (color == "w" ? 1 : -1) * (b.eval - a.eval);
1073     });
1074     let candidates = [0];
1075     for (let j = 1; j < moves1.length && moves1[j].eval == moves1[0].eval; j++)
1076       candidates.push(j);
1077     const choice = moves1[candidates[randInt(candidates.length)]];
1078     return (!choice.second ? choice : [choice, choice.second]);
1079   }
1080
1081   // For moves notation:
1082   static get LANCER_DIRNAMES() {
1083     return {
1084       'c': "N",
1085       'd': "NE",
1086       'e': "E",
1087       'f': "SE",
1088       'g': "S",
1089       'h': "SW",
1090       'm': "W",
1091       'o': "NW"
1092     };
1093   }
1094
1095   getNotation(move) {
1096     // Special case "king takes jailer" is a pass move
1097     if (move.appear.length == 0 && move.vanish.length == 0) return "pass";
1098     let notation = undefined;
1099     if (this.subTurn == 2) {
1100       // Do not consider appear[1] (sentry) for sentry pushes
1101       const simpleMove = {
1102         appear: [move.appear[0]],
1103         vanish: move.vanish,
1104         start: move.start,
1105         end: move.end
1106       };
1107       notation = super.getNotation(simpleMove);
1108     } else notation = super.getNotation(move);
1109     if (Object.keys(V.LANCER_DIRNAMES).includes(move.vanish[0].p))
1110       // Lancer: add direction info
1111       notation += "=" + V.LANCER_DIRNAMES[move.appear[0].p];
1112     return notation;
1113   }
1114 };