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Speed up computer thinking, fix Zen ep
[vchess.git] / public / javascripts / base_rules.js
1 class PiPo //Piece+Position
2 {
3 // o: {piece[p], color[c], posX[x], posY[y]}
4 constructor(o)
5 {
6 this.p = o.p;
7 this.c = o.c;
8 this.x = o.x;
9 this.y = o.y;
10 }
11 }
12
13 class Move
14 {
15 // o: {appear, vanish, [start,] [end,]}
16 // appear,vanish = arrays of PiPo
17 // start,end = coordinates to apply to trigger move visually (think castle)
18 constructor(o)
19 {
20 this.appear = o.appear;
21 this.vanish = o.vanish;
22 this.start = !!o.start ? o.start : {x:o.vanish[0].x, y:o.vanish[0].y};
23 this.end = !!o.end ? o.end : {x:o.appear[0].x, y:o.appear[0].y};
24 }
25 }
26
27 // NOTE: x coords = top to bottom; y = left to right (from white player perspective)
28 class ChessRules
29 {
30 // Path to pieces
31 static getPpath(b)
32 {
33 return b; //usual pieces in pieces/ folder
34 }
35 // Turn "wb" into "B" (for FEN)
36 static board2fen(b)
37 {
38 return b[0]=='w' ? b[1].toUpperCase() : b[1];
39 }
40 // Turn "p" into "bp" (for board)
41 static fen2board(f)
42 {
43 return f.charCodeAt()<=90 ? "w"+f.toLowerCase() : "b"+f;
44 }
45
46 /////////////////
47 // INITIALIZATION
48
49 // fen = "position flags epSquare movesCount"
50 constructor(fen, moves)
51 {
52 this.moves = moves;
53 // Use fen string to initialize variables, flags and board
54 this.initVariables(fen);
55 this.flags = VariantRules.GetFlags(fen);
56 this.board = VariantRules.GetBoard(fen);
57 }
58
59 initVariables(fen)
60 {
61 this.INIT_COL_KING = {'w':-1, 'b':-1};
62 this.INIT_COL_ROOK = {'w':[-1,-1], 'b':[-1,-1]};
63 this.kingPos = {'w':[-1,-1], 'b':[-1,-1]}; //respective squares of white and black king
64 const fenParts = fen.split(" ");
65 const position = fenParts[0].split("/");
66 for (let i=0; i<position.length; i++)
67 {
68 let j = 0;
69 while (j < position[i].length)
70 {
71 switch (position[i].charAt(j))
72 {
73 case 'k':
74 this.kingPos['b'] = [i,j];
75 this.INIT_COL_KING['b'] = j;
76 break;
77 case 'K':
78 this.kingPos['w'] = [i,j];
79 this.INIT_COL_KING['w'] = j;
80 break;
81 case 'r':
82 if (this.INIT_COL_ROOK['b'][0] < 0)
83 this.INIT_COL_ROOK['b'][0] = j;
84 else
85 this.INIT_COL_ROOK['b'][1] = j;
86 break;
87 case 'R':
88 if (this.INIT_COL_ROOK['w'][0] < 0)
89 this.INIT_COL_ROOK['w'][0] = j;
90 else
91 this.INIT_COL_ROOK['w'][1] = j;
92 break;
93 default:
94 let num = parseInt(position[i].charAt(j));
95 if (!isNaN(num))
96 j += (num-1);
97 }
98 j++;
99 }
100 }
101 // TODO: since we keep moves stack, next 2 are redundant
102 let epSq = undefined;
103 if (fenParts[2] != "-")
104 {
105 const digits = fenParts[2].split(","); //3,2 ...
106 epSq = { x:Number.parseInt(digits[0]), y:Number.parseInt(digits[1]) };
107 }
108 this.epSquares = [ epSq ];
109 this.movesCount = Number.parseInt(fenParts[3]);
110 }
111
112 // Turn diagram fen into double array ["wb","wp","bk",...]
113 static GetBoard(fen)
114 {
115 let rows = fen.split(" ")[0].split("/");
116 let [sizeX,sizeY] = VariantRules.size;
117 let board = doubleArray(sizeX, sizeY, "");
118 for (let i=0; i<rows.length; i++)
119 {
120 let j = 0;
121 for (let indexInRow = 0; indexInRow < rows[i].length; indexInRow++)
122 {
123 let character = rows[i][indexInRow];
124 let num = parseInt(character);
125 if (!isNaN(num))
126 j += num; //just shift j
127 else //something at position i,j
128 board[i][j++] = VariantRules.fen2board(character);
129 }
130 }
131 return board;
132 }
133
134 // Overridable: flags can change a lot
135 static GetFlags(fen)
136 {
137 // white a-castle, h-castle, black a-castle, h-castle
138 let flags = {'w': new Array(2), 'b': new Array(2)};
139 let fenFlags = fen.split(" ")[1]; //flags right after position
140 for (let i=0; i<4; i++)
141 flags[i < 2 ? 'w' : 'b'][i%2] = (fenFlags.charAt(i) == '1');
142 return flags;
143 }
144
145 ///////////////////
146 // GETTERS, SETTERS
147
148 // Simple useful getters
149 static get size() { return [8,8]; }
150 // Two next functions return 'undefined' if called on empty square
151 getColor(i,j) { return this.board[i][j].charAt(0); }
152 getPiece(i,j) { return this.board[i][j].charAt(1); }
153
154 // Color
155 getOppCol(color) { return color=="w" ? "b" : "w"; }
156
157 get lastMove() {
158 const L = this.moves.length;
159 return L>0 ? this.moves[L-1] : null;
160 }
161 get turn() {
162 return this.movesCount%2==0 ? 'w' : 'b';
163 }
164
165 // Pieces codes
166 static get PAWN() { return 'p'; }
167 static get ROOK() { return 'r'; }
168 static get KNIGHT() { return 'n'; }
169 static get BISHOP() { return 'b'; }
170 static get QUEEN() { return 'q'; }
171 static get KING() { return 'k'; }
172
173 // Empty square
174 static get EMPTY() { return ''; }
175
176 // Some pieces movements
177 static get steps() {
178 return {
179 'r': [ [-1,0],[1,0],[0,-1],[0,1] ],
180 'n': [ [-1,-2],[-1,2],[1,-2],[1,2],[-2,-1],[-2,1],[2,-1],[2,1] ],
181 'b': [ [-1,-1],[-1,1],[1,-1],[1,1] ],
182 'q': [ [-1,0],[1,0],[0,-1],[0,1],[-1,-1],[-1,1],[1,-1],[1,1] ]
183 };
184 }
185
186 // En-passant square, if any
187 getEpSquare(move)
188 {
189 const [sx,sy,ex] = [move.start.x,move.start.y,move.end.x];
190 if (this.getPiece(sx,sy) == VariantRules.PAWN && Math.abs(sx - ex) == 2)
191 {
192 return {
193 x: (sx + ex)/2,
194 y: sy
195 };
196 }
197 return undefined; //default
198 }
199
200 // can color1 take color2?
201 canTake(color1, color2)
202 {
203 return color1 != color2;
204 }
205
206 ///////////////////
207 // MOVES GENERATION
208
209 // All possible moves from selected square (assumption: color is OK)
210 getPotentialMovesFrom([x,y])
211 {
212 let c = this.getColor(x,y);
213 // Fill possible moves according to piece type
214 switch (this.getPiece(x,y))
215 {
216 case VariantRules.PAWN:
217 return this.getPotentialPawnMoves(x,y,c);
218 case VariantRules.ROOK:
219 return this.getPotentialRookMoves(x,y,c);
220 case VariantRules.KNIGHT:
221 return this.getPotentialKnightMoves(x,y,c);
222 case VariantRules.BISHOP:
223 return this.getPotentialBishopMoves(x,y,c);
224 case VariantRules.QUEEN:
225 return this.getPotentialQueenMoves(x,y,c);
226 case VariantRules.KING:
227 return this.getPotentialKingMoves(x,y,c);
228 }
229 }
230
231 // Build a regular move from its initial and destination squares; tr: transformation
232 getBasicMove(sx, sy, ex, ey, tr)
233 {
234 var mv = new Move({
235 appear: [
236 new PiPo({
237 x: ex,
238 y: ey,
239 c: this.getColor(sx,sy),
240 p: !!tr ? tr : this.getPiece(sx,sy)
241 })
242 ],
243 vanish: [
244 new PiPo({
245 x: sx,
246 y: sy,
247 c: this.getColor(sx,sy),
248 p: this.getPiece(sx,sy)
249 })
250 ]
251 });
252
253 // The opponent piece disappears if we take it
254 if (this.board[ex][ey] != VariantRules.EMPTY)
255 {
256 mv.vanish.push(
257 new PiPo({
258 x: ex,
259 y: ey,
260 c: this.getColor(ex,ey),
261 p: this.getPiece(ex,ey)
262 })
263 );
264 }
265 return mv;
266 }
267
268 // Generic method to find possible moves of non-pawn pieces ("sliding or jumping")
269 getSlideNJumpMoves(x, y, color, steps, oneStep)
270 {
271 var moves = [];
272 let [sizeX,sizeY] = VariantRules.size;
273 outerLoop:
274 for (let step of steps)
275 {
276 var i = x + step[0];
277 var j = y + step[1];
278 while (i>=0 && i<sizeX && j>=0 && j<sizeY
279 && this.board[i][j] == VariantRules.EMPTY)
280 {
281 moves.push(this.getBasicMove(x, y, i, j));
282 if (oneStep !== undefined)
283 continue outerLoop;
284 i += step[0];
285 j += step[1];
286 }
287 if (i>=0 && i<8 && j>=0 && j<8 && this.canTake(color, this.getColor(i,j)))
288 moves.push(this.getBasicMove(x, y, i, j));
289 }
290 return moves;
291 }
292
293 // What are the pawn moves from square x,y considering color "color" ?
294 getPotentialPawnMoves(x, y, color)
295 {
296 var moves = [];
297 var V = VariantRules;
298 let [sizeX,sizeY] = VariantRules.size;
299 let shift = (color == "w" ? -1 : 1);
300 let startRank = (color == "w" ? sizeY-2 : 1);
301 let lastRank = (color == "w" ? 0 : sizeY-1);
302
303 if (x+shift >= 0 && x+shift < sizeX && x+shift != lastRank)
304 {
305 // Normal moves
306 if (this.board[x+shift][y] == V.EMPTY)
307 {
308 moves.push(this.getBasicMove(x, y, x+shift, y));
309 if (x==startRank && this.board[x+2*shift][y] == V.EMPTY)
310 {
311 // Two squares jump
312 moves.push(this.getBasicMove(x, y, x+2*shift, y));
313 }
314 }
315 // Captures
316 if (y>0 && this.canTake(this.getColor(x,y), this.getColor(x+shift,y-1))
317 && this.board[x+shift][y-1] != V.EMPTY)
318 {
319 moves.push(this.getBasicMove(x, y, x+shift, y-1));
320 }
321 if (y<sizeY-1 && this.canTake(this.getColor(x,y), this.getColor(x+shift,y+1))
322 && this.board[x+shift][y+1] != V.EMPTY)
323 {
324 moves.push(this.getBasicMove(x, y, x+shift, y+1));
325 }
326 }
327
328 if (x+shift == lastRank)
329 {
330 // Promotion
331 let promotionPieces = [V.ROOK,V.KNIGHT,V.BISHOP,V.QUEEN];
332 promotionPieces.forEach(p => {
333 // Normal move
334 if (this.board[x+shift][y] == V.EMPTY)
335 moves.push(this.getBasicMove(x, y, x+shift, y, p));
336 // Captures
337 if (y>0 && this.canTake(this.getColor(x,y), this.getColor(x+shift,y-1))
338 && this.board[x+shift][y-1] != V.EMPTY)
339 {
340 moves.push(this.getBasicMove(x, y, x+shift, y-1, p));
341 }
342 if (y<sizeY-1 && this.canTake(this.getColor(x,y), this.getColor(x+shift,y+1))
343 && this.board[x+shift][y+1] != V.EMPTY)
344 {
345 moves.push(this.getBasicMove(x, y, x+shift, y+1, p));
346 }
347 });
348 }
349
350 // En passant
351 const Lep = this.epSquares.length;
352 const epSquare = Lep>0 ? this.epSquares[Lep-1] : undefined;
353 if (!!epSquare && epSquare.x == x+shift && Math.abs(epSquare.y - y) == 1)
354 {
355 let epStep = epSquare.y - y;
356 var enpassantMove = this.getBasicMove(x, y, x+shift, y+epStep);
357 enpassantMove.vanish.push({
358 x: x,
359 y: y+epStep,
360 p: 'p',
361 c: this.getColor(x,y+epStep)
362 });
363 moves.push(enpassantMove);
364 }
365
366 return moves;
367 }
368
369 // What are the rook moves from square x,y ?
370 getPotentialRookMoves(x, y, color)
371 {
372 return this.getSlideNJumpMoves(
373 x, y, color, VariantRules.steps[VariantRules.ROOK]);
374 }
375
376 // What are the knight moves from square x,y ?
377 getPotentialKnightMoves(x, y, color)
378 {
379 return this.getSlideNJumpMoves(
380 x, y, color, VariantRules.steps[VariantRules.KNIGHT], "oneStep");
381 }
382
383 // What are the bishop moves from square x,y ?
384 getPotentialBishopMoves(x, y, color)
385 {
386 return this.getSlideNJumpMoves(
387 x, y, color, VariantRules.steps[VariantRules.BISHOP]);
388 }
389
390 // What are the queen moves from square x,y ?
391 getPotentialQueenMoves(x, y, color)
392 {
393 return this.getSlideNJumpMoves(
394 x, y, color, VariantRules.steps[VariantRules.QUEEN]);
395 }
396
397 // What are the king moves from square x,y ?
398 getPotentialKingMoves(x, y, c)
399 {
400 // Initialize with normal moves
401 var moves = this.getSlideNJumpMoves(x, y, c,
402 VariantRules.steps[VariantRules.QUEEN], "oneStep");
403
404 return moves.concat(this.getCastleMoves(x,y,c));
405 }
406
407 getCastleMoves(x,y,c)
408 {
409 if (x != (c=="w" ? 7 : 0) || y != this.INIT_COL_KING[c])
410 return []; //x isn't first rank, or king has moved (shortcut)
411
412 const V = VariantRules;
413
414 // Castling ?
415 const oppCol = this.getOppCol(c);
416 let moves = [];
417 let i = 0;
418 const finalSquares = [ [2,3], [6,5] ]; //king, then rook
419 castlingCheck:
420 for (let castleSide=0; castleSide < 2; castleSide++) //large, then small
421 {
422 if (!this.flags[c][castleSide])
423 continue;
424 // If this code is reached, rooks and king are on initial position
425
426 // Nothing on the path of the king (and no checks; OK also if y==finalSquare)?
427 let step = finalSquares[castleSide][0] < y ? -1 : 1;
428 for (i=y; i!=finalSquares[castleSide][0]; i+=step)
429 {
430 if (this.isAttacked([x,i], oppCol) || (this.board[x][i] != V.EMPTY &&
431 // NOTE: next check is enough, because of chessboard constraints
432 (this.getColor(x,i) != c || ![V.KING,V.ROOK].includes(this.getPiece(x,i)))))
433 {
434 continue castlingCheck;
435 }
436 }
437
438 // Nothing on the path to the rook?
439 step = castleSide == 0 ? -1 : 1;
440 for (i = y + step; i != this.INIT_COL_ROOK[c][castleSide]; i += step)
441 {
442 if (this.board[x][i] != V.EMPTY)
443 continue castlingCheck;
444 }
445 const rookPos = this.INIT_COL_ROOK[c][castleSide];
446
447 // Nothing on final squares, except maybe king and castling rook?
448 for (i=0; i<2; i++)
449 {
450 if (this.board[x][finalSquares[castleSide][i]] != V.EMPTY &&
451 this.getPiece(x,finalSquares[castleSide][i]) != V.KING &&
452 finalSquares[castleSide][i] != rookPos)
453 {
454 continue castlingCheck;
455 }
456 }
457
458 // If this code is reached, castle is valid
459 moves.push( new Move({
460 appear: [
461 new PiPo({x:x,y:finalSquares[castleSide][0],p:V.KING,c:c}),
462 new PiPo({x:x,y:finalSquares[castleSide][1],p:V.ROOK,c:c})],
463 vanish: [
464 new PiPo({x:x,y:y,p:V.KING,c:c}),
465 new PiPo({x:x,y:rookPos,p:V.ROOK,c:c})],
466 end: Math.abs(y - rookPos) <= 2
467 ? {x:x, y:rookPos}
468 : {x:x, y:y + 2 * (castleSide==0 ? -1 : 1)}
469 }) );
470 }
471
472 return moves;
473 }
474
475 ///////////////////
476 // MOVES VALIDATION
477
478 canIplay(color, sq)
479 {
480 return ((color=='w' && this.movesCount%2==0)
481 || (color=='b' && this.movesCount%2==1))
482 && this.getColor(sq[0], sq[1]) == color;
483 }
484
485 getPossibleMovesFrom(sq)
486 {
487 // Assuming color is right (already checked)
488 return this.filterValid( this.getPotentialMovesFrom(sq) );
489 }
490
491 // TODO: once a promotion is filtered, the others results are same: useless computations
492 filterValid(moves)
493 {
494 if (moves.length == 0)
495 return [];
496 let color = this.getColor( moves[0].start.x, moves[0].start.y );
497 return moves.filter(m => {
498 return !this.underCheck(m, color);
499 });
500 }
501
502 // Search for all valid moves considering current turn (for engine and game end)
503 getAllValidMoves(color)
504 {
505 const oppCol = this.getOppCol(color);
506 var potentialMoves = [];
507 let [sizeX,sizeY] = VariantRules.size;
508 for (var i=0; i<sizeX; i++)
509 {
510 for (var j=0; j<sizeY; j++)
511 {
512 // Next condition ... != oppCol is a little HACK to work with checkered variant
513 if (this.board[i][j] != VariantRules.EMPTY && this.getColor(i,j) != oppCol)
514 Array.prototype.push.apply(potentialMoves, this.getPotentialMovesFrom([i,j]));
515 }
516 }
517 // NOTE: prefer lazy undercheck tests, letting the king being taken?
518 // No: if happen on last 1/2 move, could lead to forbidden moves, wrong evals
519 return this.filterValid(potentialMoves);
520 }
521
522 // Stop at the first move found
523 atLeastOneMove(color)
524 {
525 const oppCol = this.getOppCol(color);
526 let [sizeX,sizeY] = VariantRules.size;
527 for (var i=0; i<sizeX; i++)
528 {
529 for (var j=0; j<sizeY; j++)
530 {
531 if (this.board[i][j] != VariantRules.EMPTY && this.getColor(i,j) != oppCol)
532 {
533 const moves = this.getPotentialMovesFrom([i,j]);
534 if (moves.length > 0)
535 {
536 for (let i=0; i<moves.length; i++)
537 {
538 if (this.filterValid([moves[i]]).length > 0)
539 return true;
540 }
541 }
542 }
543 }
544 }
545 return false;
546 }
547
548 // Check if pieces of color 'color' are attacking square x,y
549 isAttacked(sq, color)
550 {
551 return (this.isAttackedByPawn(sq, color)
552 || this.isAttackedByRook(sq, color)
553 || this.isAttackedByKnight(sq, color)
554 || this.isAttackedByBishop(sq, color)
555 || this.isAttackedByQueen(sq, color)
556 || this.isAttackedByKing(sq, color));
557 }
558
559 // Is square x,y attacked by pawns of color c ?
560 isAttackedByPawn([x,y], c)
561 {
562 let pawnShift = (c=="w" ? 1 : -1);
563 if (x+pawnShift>=0 && x+pawnShift<8)
564 {
565 for (let i of [-1,1])
566 {
567 if (y+i>=0 && y+i<8 && this.getPiece(x+pawnShift,y+i)==VariantRules.PAWN
568 && this.getColor(x+pawnShift,y+i)==c)
569 {
570 return true;
571 }
572 }
573 }
574 return false;
575 }
576
577 // Is square x,y attacked by rooks of color c ?
578 isAttackedByRook(sq, color)
579 {
580 return this.isAttackedBySlideNJump(sq, color,
581 VariantRules.ROOK, VariantRules.steps[VariantRules.ROOK]);
582 }
583
584 // Is square x,y attacked by knights of color c ?
585 isAttackedByKnight(sq, color)
586 {
587 return this.isAttackedBySlideNJump(sq, color,
588 VariantRules.KNIGHT, VariantRules.steps[VariantRules.KNIGHT], "oneStep");
589 }
590
591 // Is square x,y attacked by bishops of color c ?
592 isAttackedByBishop(sq, color)
593 {
594 return this.isAttackedBySlideNJump(sq, color,
595 VariantRules.BISHOP, VariantRules.steps[VariantRules.BISHOP]);
596 }
597
598 // Is square x,y attacked by queens of color c ?
599 isAttackedByQueen(sq, color)
600 {
601 return this.isAttackedBySlideNJump(sq, color,
602 VariantRules.QUEEN, VariantRules.steps[VariantRules.QUEEN]);
603 }
604
605 // Is square x,y attacked by king of color c ?
606 isAttackedByKing(sq, color)
607 {
608 return this.isAttackedBySlideNJump(sq, color,
609 VariantRules.KING, VariantRules.steps[VariantRules.QUEEN], "oneStep");
610 }
611
612 // Generic method for non-pawn pieces ("sliding or jumping"): is x,y attacked by piece != color ?
613 isAttackedBySlideNJump([x,y], c,piece,steps,oneStep)
614 {
615 for (let step of steps)
616 {
617 let rx = x+step[0], ry = y+step[1];
618 while (rx>=0 && rx<8 && ry>=0 && ry<8 && this.board[rx][ry] == VariantRules.EMPTY
619 && !oneStep)
620 {
621 rx += step[0];
622 ry += step[1];
623 }
624 if (rx>=0 && rx<8 && ry>=0 && ry<8 && this.board[rx][ry] != VariantRules.EMPTY
625 && this.getPiece(rx,ry) == piece && this.getColor(rx,ry) == c)
626 {
627 return true;
628 }
629 }
630 return false;
631 }
632
633 // Is color c under check after move ?
634 underCheck(move, c)
635 {
636 this.play(move);
637 let res = this.isAttacked(this.kingPos[c], this.getOppCol(c));
638 this.undo(move);
639 return res;
640 }
641
642 // On which squares is color c under check (after move) ?
643 getCheckSquares(move, c)
644 {
645 this.play(move);
646 let res = this.isAttacked(this.kingPos[c], this.getOppCol(c))
647 ? [ JSON.parse(JSON.stringify(this.kingPos[c])) ] //need to duplicate!
648 : [ ];
649 this.undo(move);
650 return res;
651 }
652
653 // Apply a move on board
654 static PlayOnBoard(board, move)
655 {
656 for (let psq of move.vanish)
657 board[psq.x][psq.y] = VariantRules.EMPTY;
658 for (let psq of move.appear)
659 board[psq.x][psq.y] = psq.c + psq.p;
660 }
661 // Un-apply the played move
662 static UndoOnBoard(board, move)
663 {
664 for (let psq of move.appear)
665 board[psq.x][psq.y] = VariantRules.EMPTY;
666 for (let psq of move.vanish)
667 board[psq.x][psq.y] = psq.c + psq.p;
668 }
669
670 // Before move is played:
671 updateVariables(move)
672 {
673 const piece = this.getPiece(move.start.x,move.start.y);
674 const c = this.getColor(move.start.x,move.start.y);
675 const firstRank = (c == "w" ? 7 : 0);
676
677 // Update king position + flags
678 if (piece == VariantRules.KING && move.appear.length > 0)
679 {
680 this.kingPos[c][0] = move.appear[0].x;
681 this.kingPos[c][1] = move.appear[0].y;
682 this.flags[c] = [false,false];
683 return;
684 }
685 const oppCol = this.getOppCol(c);
686 const oppFirstRank = 7 - firstRank;
687 if (move.start.x == firstRank //our rook moves?
688 && this.INIT_COL_ROOK[c].includes(move.start.y))
689 {
690 const flagIdx = move.start.y == this.INIT_COL_ROOK[c][0] ? 0 : 1;
691 this.flags[c][flagIdx] = false;
692 }
693 else if (move.end.x == oppFirstRank //we took opponent rook?
694 && this.INIT_COL_ROOK[c].includes(move.end.y))
695 {
696 const flagIdx = move.end.y == this.INIT_COL_ROOK[oppCol][0] ? 0 : 1;
697 this.flags[oppCol][flagIdx] = false;
698 }
699 }
700
701 play(move, ingame)
702 {
703 // Save flags (for undo)
704 move.flags = JSON.stringify(this.flags); //TODO: less costly
705 this.updateVariables(move);
706
707 if (!!ingame)
708 {
709 move.notation = this.getNotation(move);
710 this.moves.push(move);
711 }
712
713 this.epSquares.push( this.getEpSquare(move) );
714 VariantRules.PlayOnBoard(this.board, move);
715 this.movesCount++;
716 }
717
718 undo(move, ingame)
719 {
720 VariantRules.UndoOnBoard(this.board, move);
721 this.epSquares.pop();
722 this.movesCount--;
723
724 if (!!ingame)
725 this.moves.pop();
726
727 // Update king position, and reset stored/computed flags
728 const c = this.getColor(move.start.x,move.start.y);
729 if (this.getPiece(move.start.x,move.start.y) == VariantRules.KING)
730 this.kingPos[c] = [move.start.x, move.start.y];
731
732 this.flags = JSON.parse(move.flags);
733 }
734
735 //////////////
736 // END OF GAME
737
738 checkGameOver(color)
739 {
740 // Check for 3 repetitions
741 if (this.moves.length >= 8)
742 {
743 // NOTE: crude detection, only moves repetition
744 const L = this.moves.length;
745 if (_.isEqual(this.moves[L-1], this.moves[L-5]) &&
746 _.isEqual(this.moves[L-2], this.moves[L-6]) &&
747 _.isEqual(this.moves[L-3], this.moves[L-7]) &&
748 _.isEqual(this.moves[L-4], this.moves[L-8]))
749 {
750 return "1/2 (repetition)";
751 }
752 }
753
754 if (this.atLeastOneMove(color))
755 {
756 // game not over
757 return "*";
758 }
759
760 // Game over
761 return this.checkGameEnd(color);
762 }
763
764 // Useful stand-alone for engine
765 checkGameEnd(color)
766 {
767 // No valid move: stalemate or checkmate?
768 if (!this.isAttacked(this.kingPos[color], this.getOppCol(color)))
769 return "1/2";
770 // OK, checkmate
771 return color == "w" ? "0-1" : "1-0";
772 }
773
774 ////////
775 //ENGINE
776
777 // Pieces values
778 static get VALUES() {
779 return {
780 'p': 1,
781 'r': 5,
782 'n': 3,
783 'b': 3,
784 'q': 9,
785 'k': 1000
786 };
787 }
788
789 // Assumption: at least one legal move
790 getComputerMove(color)
791 {
792 const oppCol = this.getOppCol(color);
793
794 // Rank moves using a min-max at depth 2
795 let moves1 = this.getAllValidMoves(color);
796
797 for (let i=0; i<moves1.length; i++)
798 {
799 moves1[i].eval = (color=="w" ? -1 : 1) * 1000; //very low, I'm checkmated
800 let eval2 = (color=="w" ? 1 : -1) * 1000; //initialized with very high (checkmate) value
801 this.play(moves1[i]);
802 // Second half-move:
803 let moves2 = this.getAllValidMoves(oppCol);
804 // If no possible moves AND underCheck, eval2 is correct.
805 // If !underCheck, eval2 is 0 (stalemate).
806 if (moves2.length == 0 && this.checkGameEnd(oppCol) == "1/2")
807 eval2 = 0;
808 for (let j=0; j<moves2.length; j++)
809 {
810 this.play(moves2[j]);
811 let evalPos = this.evalPosition();
812 if ((color == "w" && evalPos < eval2) || (color=="b" && evalPos > eval2))
813 eval2 = evalPos;
814 this.undo(moves2[j]);
815 }
816 if ((color=="w" && eval2 > moves1[i].eval) || (color=="b" && eval2 < moves1[i].eval))
817 moves1[i].eval = eval2;
818 this.undo(moves1[i]);
819 }
820 moves1.sort( (a,b) => { return (color=="w" ? 1 : -1) * (b.eval - a.eval); });
821
822 // TODO: show current analyzed move for depth 3, allow stopping eval (return moves1[0])
823 for (let i=0; i<moves1.length; i++)
824 {
825 this.play(moves1[i]);
826 // 0.1 * oldEval : heuristic to avoid some bad moves (not all...)
827 moves1[i].eval = 0.1*moves1[i].eval + this.alphabeta(oppCol, color, 2, -1000, 1000);
828 this.undo(moves1[i]);
829 }
830 moves1.sort( (a,b) => { return (color=="w" ? 1 : -1) * (b.eval - a.eval); });
831
832 let candidates = [0]; //indices of candidates moves
833 for (let j=1; j<moves1.length && moves1[j].eval == moves1[0].eval; j++)
834 candidates.push(j);
835
836 //console.log(moves1.map(m => { return [this.getNotation(m), m.eval]; }));
837 return moves1[_.sample(candidates, 1)];
838 }
839
840 alphabeta(color, oppCol, depth, alpha, beta)
841 {
842 if (!this.atLeastOneMove(color))
843 {
844 switch (this.checkGameEnd(color))
845 {
846 case "1/2": return 0;
847 default: return color=="w" ? -1000 : 1000;
848 }
849 }
850 if (depth == 0)
851 return this.evalPosition();
852 const moves = this.getAllValidMoves(color);
853 let v = color=="w" ? -1000 : 1000;
854 if (color == "w")
855 {
856 for (let i=0; i<moves.length; i++)
857 {
858 this.play(moves[i]);
859 v = Math.max(v, this.alphabeta(oppCol, color, depth-1, alpha, beta));
860 this.undo(moves[i]);
861 alpha = Math.max(alpha, v);
862 if (alpha >= beta)
863 break; //beta cutoff
864 }
865 }
866 else //color=="b"
867 {
868 for (let i=0; i<moves.length; i++)
869 {
870 this.play(moves[i]);
871 v = Math.min(v, this.alphabeta(oppCol, color, depth-1, alpha, beta));
872 this.undo(moves[i]);
873 beta = Math.min(beta, v);
874 if (alpha >= beta)
875 break; //alpha cutoff
876 }
877 }
878 return v;
879 }
880
881 evalPosition()
882 {
883 const [sizeX,sizeY] = VariantRules.size;
884 let evaluation = 0;
885 //Just count material for now
886 for (let i=0; i<sizeX; i++)
887 {
888 for (let j=0; j<sizeY; j++)
889 {
890 if (this.board[i][j] != VariantRules.EMPTY)
891 {
892 const sign = this.getColor(i,j) == "w" ? 1 : -1;
893 evaluation += sign * VariantRules.VALUES[this.getPiece(i,j)];
894 }
895 }
896 }
897 return evaluation;
898 }
899
900 ////////////
901 // FEN utils
902
903 // Overridable..
904 static GenRandInitFen()
905 {
906 let pieces = [new Array(8), new Array(8)];
907 // Shuffle pieces on first and last rank
908 for (let c = 0; c <= 1; c++)
909 {
910 let positions = _.range(8);
911
912 // Get random squares for bishops
913 let randIndex = 2 * _.random(3);
914 let bishop1Pos = positions[randIndex];
915 // The second bishop must be on a square of different color
916 let randIndex_tmp = 2 * _.random(3) + 1;
917 let bishop2Pos = positions[randIndex_tmp];
918 // Remove chosen squares
919 positions.splice(Math.max(randIndex,randIndex_tmp), 1);
920 positions.splice(Math.min(randIndex,randIndex_tmp), 1);
921
922 // Get random squares for knights
923 randIndex = _.random(5);
924 let knight1Pos = positions[randIndex];
925 positions.splice(randIndex, 1);
926 randIndex = _.random(4);
927 let knight2Pos = positions[randIndex];
928 positions.splice(randIndex, 1);
929
930 // Get random square for queen
931 randIndex = _.random(3);
932 let queenPos = positions[randIndex];
933 positions.splice(randIndex, 1);
934
935 // Rooks and king positions are now fixed, because of the ordering rook-king-rook
936 let rook1Pos = positions[0];
937 let kingPos = positions[1];
938 let rook2Pos = positions[2];
939
940 // Finally put the shuffled pieces in the board array
941 pieces[c][rook1Pos] = 'r';
942 pieces[c][knight1Pos] = 'n';
943 pieces[c][bishop1Pos] = 'b';
944 pieces[c][queenPos] = 'q';
945 pieces[c][kingPos] = 'k';
946 pieces[c][bishop2Pos] = 'b';
947 pieces[c][knight2Pos] = 'n';
948 pieces[c][rook2Pos] = 'r';
949 }
950 let fen = pieces[0].join("") +
951 "/pppppppp/8/8/8/8/PPPPPPPP/" +
952 pieces[1].join("").toUpperCase() +
953 " 1111 - 0"; //flags + enPassant + movesCount
954 return fen;
955 }
956
957 // Return current fen according to pieces+colors state
958 getFen()
959 {
960 const L = this.epSquares.length;
961 const epSq = this.epSquares[L-1]===undefined
962 ? "-"
963 : this.epSquares[L-1].x+","+this.epSquares[L-1].y;
964 return this.getBaseFen() + " " + this.getFlagsFen()
965 + " " + epSq + " " + this.movesCount;
966 }
967
968 getBaseFen()
969 {
970 let fen = "";
971 let [sizeX,sizeY] = VariantRules.size;
972 for (let i=0; i<sizeX; i++)
973 {
974 let emptyCount = 0;
975 for (let j=0; j<sizeY; j++)
976 {
977 if (this.board[i][j] == VariantRules.EMPTY)
978 emptyCount++;
979 else
980 {
981 if (emptyCount > 0)
982 {
983 // Add empty squares in-between
984 fen += emptyCount;
985 emptyCount = 0;
986 }
987 fen += VariantRules.board2fen(this.board[i][j]);
988 }
989 }
990 if (emptyCount > 0)
991 {
992 // "Flush remainder"
993 fen += emptyCount;
994 }
995 if (i < sizeX - 1)
996 fen += "/"; //separate rows
997 }
998 return fen;
999 }
1000
1001 // Overridable..
1002 getFlagsFen()
1003 {
1004 let fen = "";
1005 // Add castling flags
1006 for (let i of ['w','b'])
1007 {
1008 for (let j=0; j<2; j++)
1009 fen += this.flags[i][j] ? '1' : '0';
1010 }
1011 return fen;
1012 }
1013
1014 // Context: just before move is played, turn hasn't changed
1015 getNotation(move)
1016 {
1017 if (move.appear.length == 2)
1018 {
1019 // Castle
1020 if (move.end.y < move.start.y)
1021 return "0-0-0";
1022 else
1023 return "0-0";
1024 }
1025
1026 // Translate final square
1027 let finalSquare =
1028 String.fromCharCode(97 + move.end.y) + (VariantRules.size[0]-move.end.x);
1029
1030 let piece = this.getPiece(move.start.x, move.start.y);
1031 if (piece == VariantRules.PAWN)
1032 {
1033 // Pawn move
1034 let notation = "";
1035 if (move.vanish.length > 1)
1036 {
1037 // Capture
1038 let startColumn = String.fromCharCode(97 + move.start.y);
1039 notation = startColumn + "x" + finalSquare;
1040 }
1041 else //no capture
1042 notation = finalSquare;
1043 if (move.appear.length > 0 && piece != move.appear[0].p) //promotion
1044 notation += "=" + move.appear[0].p.toUpperCase();
1045 return notation;
1046 }
1047
1048 else
1049 {
1050 // Piece movement
1051 return piece.toUpperCase() + (move.vanish.length > 1 ? "x" : "") + finalSquare;
1052 }
1053 }
1054
1055 // The score is already computed when calling this function
1056 getPGN(mycolor, score, fenStart)
1057 {
1058 let pgn = "";
1059 pgn += '[Site "vchess.club"]<br>';
1060 const d = new Date();
1061 pgn += '[Date "' + d.getFullYear() + '-' + d.getMonth() + '-' + d.getDate() + '"]<br>';
1062 pgn += '[White "' + (mycolor=='w'?'Myself':'Anonymous') + '"]<br>';
1063 pgn += '[Black "' + (mycolor=='b'?'Myself':'Anonymous') + '"]<br>';
1064 pgn += '[Fen "' + fenStart + '"]<br>';
1065 pgn += '[Result "' + score + '"]<br><br>';
1066
1067 for (let i=0; i<this.moves.length; i++)
1068 {
1069 if (i % 2 == 0)
1070 pgn += ((i/2)+1) + ".";
1071 pgn += this.moves[i].notation + " ";
1072 }
1073
1074 pgn += score;
1075 return pgn;
1076 }
1077 }
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