Fix Dynamo diagrams
[vchess.git] / client / src / base_rules.js
1 // (Orthodox) Chess rules are defined in ChessRules class.
2 // Variants generally inherit from it, and modify some parts.
3
4 import { ArrayFun } from "@/utils/array";
5 import { randInt, shuffle } from "@/utils/alea";
6
7 // class "PiPo": Piece + Position
8 export const PiPo = class PiPo {
9 // o: {piece[p], color[c], posX[x], posY[y]}
10 constructor(o) {
11 this.p = o.p;
12 this.c = o.c;
13 this.x = o.x;
14 this.y = o.y;
15 }
16 };
17
18 export const Move = class Move {
19 // o: {appear, vanish, [start,] [end,]}
20 // appear,vanish = arrays of PiPo
21 // start,end = coordinates to apply to trigger move visually (think castle)
22 constructor(o) {
23 this.appear = o.appear;
24 this.vanish = o.vanish;
25 this.start = o.start ? o.start : { x: o.vanish[0].x, y: o.vanish[0].y };
26 this.end = o.end ? o.end : { x: o.appear[0].x, y: o.appear[0].y };
27 }
28 };
29
30 // NOTE: x coords = top to bottom; y = left to right
31 // (from white player perspective)
32 export const ChessRules = class ChessRules {
33 //////////////
34 // MISC UTILS
35
36 // Some variants don't have flags:
37 static get HasFlags() {
38 return true;
39 }
40
41 // Or castle
42 static get HasCastle() {
43 return V.HasFlags;
44 }
45
46 // Pawns specifications
47 static get PawnSpecs() {
48 return {
49 directions: { 'w': -1, 'b': 1 },
50 initShift: { w: 1, b: 1 },
51 twoSquares: true,
52 threeSquares: false,
53 promotions: [V.ROOK, V.KNIGHT, V.BISHOP, V.QUEEN],
54 canCapture: true,
55 captureBackward: false,
56 bidirectional: false
57 };
58 }
59
60 // En-passant captures need a stack of squares:
61 static get HasEnpassant() {
62 return true;
63 }
64
65 // Some variants cannot have analyse mode
66 static get CanAnalyze() {
67 return true;
68 }
69 // Patch: issues with javascript OOP, objects can't access static fields.
70 get canAnalyze() {
71 return V.CanAnalyze;
72 }
73
74 // Some variants show incomplete information,
75 // and thus show only a partial moves list or no list at all.
76 static get ShowMoves() {
77 return "all";
78 }
79 get showMoves() {
80 return V.ShowMoves;
81 }
82
83 // Some variants always show the same orientation
84 static get CanFlip() {
85 return true;
86 }
87 get canFlip() {
88 return V.CanFlip;
89 }
90
91 // Some variants use click infos:
92 doClick() {
93 return null;
94 }
95
96 static get IMAGE_EXTENSION() {
97 // All pieces should be in the SVG format
98 return ".svg";
99 }
100
101 // Turn "wb" into "B" (for FEN)
102 static board2fen(b) {
103 return b[0] == "w" ? b[1].toUpperCase() : b[1];
104 }
105
106 // Turn "p" into "bp" (for board)
107 static fen2board(f) {
108 return f.charCodeAt() <= 90 ? "w" + f.toLowerCase() : "b" + f;
109 }
110
111 // Check if FEN describes a board situation correctly
112 static IsGoodFen(fen) {
113 const fenParsed = V.ParseFen(fen);
114 // 1) Check position
115 if (!V.IsGoodPosition(fenParsed.position)) return false;
116 // 2) Check turn
117 if (!fenParsed.turn || !V.IsGoodTurn(fenParsed.turn)) return false;
118 // 3) Check moves count
119 if (!fenParsed.movesCount || !(parseInt(fenParsed.movesCount) >= 0))
120 return false;
121 // 4) Check flags
122 if (V.HasFlags && (!fenParsed.flags || !V.IsGoodFlags(fenParsed.flags)))
123 return false;
124 // 5) Check enpassant
125 if (
126 V.HasEnpassant &&
127 (!fenParsed.enpassant || !V.IsGoodEnpassant(fenParsed.enpassant))
128 ) {
129 return false;
130 }
131 return true;
132 }
133
134 // Is position part of the FEN a priori correct?
135 static IsGoodPosition(position) {
136 if (position.length == 0) return false;
137 const rows = position.split("/");
138 if (rows.length != V.size.x) return false;
139 let kings = { "k": 0, "K": 0 };
140 for (let row of rows) {
141 let sumElts = 0;
142 for (let i = 0; i < row.length; i++) {
143 if (['K','k'].includes(row[i])) kings[row[i]]++;
144 if (V.PIECES.includes(row[i].toLowerCase())) sumElts++;
145 else {
146 const num = parseInt(row[i]);
147 if (isNaN(num)) return false;
148 sumElts += num;
149 }
150 }
151 if (sumElts != V.size.y) return false;
152 }
153 // Both kings should be on board. Exactly one per color.
154 if (Object.values(kings).some(v => v != 1)) return false;
155 return true;
156 }
157
158 // For FEN checking
159 static IsGoodTurn(turn) {
160 return ["w", "b"].includes(turn);
161 }
162
163 // For FEN checking
164 static IsGoodFlags(flags) {
165 // NOTE: a little too permissive to work with more variants
166 return !!flags.match(/^[a-z]{4,4}$/);
167 }
168
169 // NOTE: not with regexp to adapt to different board sizes. (TODO?)
170 static IsGoodEnpassant(enpassant) {
171 if (enpassant != "-") {
172 const ep = V.SquareToCoords(enpassant);
173 if (isNaN(ep.x) || !V.OnBoard(ep)) return false;
174 }
175 return true;
176 }
177
178 // 3 --> d (column number to letter)
179 static CoordToColumn(colnum) {
180 return String.fromCharCode(97 + colnum);
181 }
182
183 // d --> 3 (column letter to number)
184 static ColumnToCoord(column) {
185 return column.charCodeAt(0) - 97;
186 }
187
188 // a4 --> {x:3,y:0}
189 static SquareToCoords(sq) {
190 return {
191 // NOTE: column is always one char => max 26 columns
192 // row is counted from black side => subtraction
193 x: V.size.x - parseInt(sq.substr(1)),
194 y: sq[0].charCodeAt() - 97
195 };
196 }
197
198 // {x:0,y:4} --> e8
199 static CoordsToSquare(coords) {
200 return V.CoordToColumn(coords.y) + (V.size.x - coords.x);
201 }
202
203 // Path to pieces (standard ones in pieces/ folder)
204 getPpath(b) {
205 return b;
206 }
207
208 // Path to promotion pieces (usually the same)
209 getPPpath(m) {
210 return this.getPpath(m.appear[0].c + m.appear[0].p);
211 }
212
213 // Aggregates flags into one object
214 aggregateFlags() {
215 return this.castleFlags;
216 }
217
218 // Reverse operation
219 disaggregateFlags(flags) {
220 this.castleFlags = flags;
221 }
222
223 // En-passant square, if any
224 getEpSquare(moveOrSquare) {
225 if (!moveOrSquare) return undefined;
226 if (typeof moveOrSquare === "string") {
227 const square = moveOrSquare;
228 if (square == "-") return undefined;
229 return V.SquareToCoords(square);
230 }
231 // Argument is a move:
232 const move = moveOrSquare;
233 const s = move.start,
234 e = move.end;
235 if (
236 s.y == e.y &&
237 Math.abs(s.x - e.x) == 2 &&
238 // Next conditions for variants like Atomic or Rifle, Recycle...
239 (move.appear.length > 0 && move.appear[0].p == V.PAWN) &&
240 (move.vanish.length > 0 && move.vanish[0].p == V.PAWN)
241 ) {
242 return {
243 x: (s.x + e.x) / 2,
244 y: s.y
245 };
246 }
247 return undefined; //default
248 }
249
250 // Can thing on square1 take thing on square2
251 canTake([x1, y1], [x2, y2]) {
252 return this.getColor(x1, y1) !== this.getColor(x2, y2);
253 }
254
255 // Is (x,y) on the chessboard?
256 static OnBoard(x, y) {
257 return x >= 0 && x < V.size.x && y >= 0 && y < V.size.y;
258 }
259
260 // Used in interface: 'side' arg == player color
261 canIplay(side, [x, y]) {
262 return this.turn == side && this.getColor(x, y) == side;
263 }
264
265 // On which squares is color under check ? (for interface)
266 getCheckSquares(color) {
267 return (
268 this.underCheck(color)
269 // kingPos must be duplicated, because it may change:
270 ? [JSON.parse(JSON.stringify(this.kingPos[color]))]
271 : []
272 );
273 }
274
275 /////////////
276 // FEN UTILS
277
278 // Setup the initial random (asymmetric) position
279 static GenRandInitFen(randomness) {
280 if (randomness == 0)
281 // Deterministic:
282 return "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w 0 ahah -";
283
284 let pieces = { w: new Array(8), b: new Array(8) };
285 let flags = "";
286 // Shuffle pieces on first (and last rank if randomness == 2)
287 for (let c of ["w", "b"]) {
288 if (c == 'b' && randomness == 1) {
289 pieces['b'] = pieces['w'];
290 flags += flags;
291 break;
292 }
293
294 let positions = ArrayFun.range(8);
295
296 // Get random squares for bishops
297 let randIndex = 2 * randInt(4);
298 const bishop1Pos = positions[randIndex];
299 // The second bishop must be on a square of different color
300 let randIndex_tmp = 2 * randInt(4) + 1;
301 const bishop2Pos = positions[randIndex_tmp];
302 // Remove chosen squares
303 positions.splice(Math.max(randIndex, randIndex_tmp), 1);
304 positions.splice(Math.min(randIndex, randIndex_tmp), 1);
305
306 // Get random squares for knights
307 randIndex = randInt(6);
308 const knight1Pos = positions[randIndex];
309 positions.splice(randIndex, 1);
310 randIndex = randInt(5);
311 const knight2Pos = positions[randIndex];
312 positions.splice(randIndex, 1);
313
314 // Get random square for queen
315 randIndex = randInt(4);
316 const queenPos = positions[randIndex];
317 positions.splice(randIndex, 1);
318
319 // Rooks and king positions are now fixed,
320 // because of the ordering rook-king-rook
321 const rook1Pos = positions[0];
322 const kingPos = positions[1];
323 const rook2Pos = positions[2];
324
325 // Finally put the shuffled pieces in the board array
326 pieces[c][rook1Pos] = "r";
327 pieces[c][knight1Pos] = "n";
328 pieces[c][bishop1Pos] = "b";
329 pieces[c][queenPos] = "q";
330 pieces[c][kingPos] = "k";
331 pieces[c][bishop2Pos] = "b";
332 pieces[c][knight2Pos] = "n";
333 pieces[c][rook2Pos] = "r";
334 flags += V.CoordToColumn(rook1Pos) + V.CoordToColumn(rook2Pos);
335 }
336 // Add turn + flags + enpassant
337 return (
338 pieces["b"].join("") +
339 "/pppppppp/8/8/8/8/PPPPPPPP/" +
340 pieces["w"].join("").toUpperCase() +
341 " w 0 " + flags + " -"
342 );
343 }
344
345 // "Parse" FEN: just return untransformed string data
346 static ParseFen(fen) {
347 const fenParts = fen.split(" ");
348 let res = {
349 position: fenParts[0],
350 turn: fenParts[1],
351 movesCount: fenParts[2]
352 };
353 let nextIdx = 3;
354 if (V.HasFlags) Object.assign(res, { flags: fenParts[nextIdx++] });
355 if (V.HasEnpassant) Object.assign(res, { enpassant: fenParts[nextIdx] });
356 return res;
357 }
358
359 // Return current fen (game state)
360 getFen() {
361 return (
362 this.getBaseFen() + " " +
363 this.getTurnFen() + " " +
364 this.movesCount +
365 (V.HasFlags ? " " + this.getFlagsFen() : "") +
366 (V.HasEnpassant ? " " + this.getEnpassantFen() : "")
367 );
368 }
369
370 getFenForRepeat() {
371 // Omit movesCount, only variable allowed to differ
372 return (
373 this.getBaseFen() + "_" +
374 this.getTurnFen() +
375 (V.HasFlags ? "_" + this.getFlagsFen() : "") +
376 (V.HasEnpassant ? "_" + this.getEnpassantFen() : "")
377 );
378 }
379
380 // Position part of the FEN string
381 getBaseFen() {
382 const format = (count) => {
383 // if more than 9 consecutive free spaces, break the integer,
384 // otherwise FEN parsing will fail.
385 if (count <= 9) return count;
386 // Currently only boards of size up to 11 or 12:
387 return "9" + (count - 9);
388 };
389 let position = "";
390 for (let i = 0; i < V.size.x; i++) {
391 let emptyCount = 0;
392 for (let j = 0; j < V.size.y; j++) {
393 if (this.board[i][j] == V.EMPTY) emptyCount++;
394 else {
395 if (emptyCount > 0) {
396 // Add empty squares in-between
397 position += format(emptyCount);
398 emptyCount = 0;
399 }
400 position += V.board2fen(this.board[i][j]);
401 }
402 }
403 if (emptyCount > 0) {
404 // "Flush remainder"
405 position += format(emptyCount);
406 }
407 if (i < V.size.x - 1) position += "/"; //separate rows
408 }
409 return position;
410 }
411
412 getTurnFen() {
413 return this.turn;
414 }
415
416 // Flags part of the FEN string
417 getFlagsFen() {
418 let flags = "";
419 // Castling flags
420 for (let c of ["w", "b"])
421 flags += this.castleFlags[c].map(V.CoordToColumn).join("");
422 return flags;
423 }
424
425 // Enpassant part of the FEN string
426 getEnpassantFen() {
427 const L = this.epSquares.length;
428 if (!this.epSquares[L - 1]) return "-"; //no en-passant
429 return V.CoordsToSquare(this.epSquares[L - 1]);
430 }
431
432 // Turn position fen into double array ["wb","wp","bk",...]
433 static GetBoard(position) {
434 const rows = position.split("/");
435 let board = ArrayFun.init(V.size.x, V.size.y, "");
436 for (let i = 0; i < rows.length; i++) {
437 let j = 0;
438 for (let indexInRow = 0; indexInRow < rows[i].length; indexInRow++) {
439 const character = rows[i][indexInRow];
440 const num = parseInt(character);
441 // If num is a number, just shift j:
442 if (!isNaN(num)) j += num;
443 // Else: something at position i,j
444 else board[i][j++] = V.fen2board(character);
445 }
446 }
447 return board;
448 }
449
450 // Extract (relevant) flags from fen
451 setFlags(fenflags) {
452 // white a-castle, h-castle, black a-castle, h-castle
453 this.castleFlags = { w: [-1, -1], b: [-1, -1] };
454 for (let i = 0; i < 4; i++) {
455 this.castleFlags[i < 2 ? "w" : "b"][i % 2] =
456 V.ColumnToCoord(fenflags.charAt(i));
457 }
458 }
459
460 //////////////////
461 // INITIALIZATION
462
463 // Fen string fully describes the game state
464 constructor(fen) {
465 if (!fen)
466 // In printDiagram() fen isn't supply because only getPpath() is used
467 // TODO: find a better solution!
468 return;
469 const fenParsed = V.ParseFen(fen);
470 this.board = V.GetBoard(fenParsed.position);
471 this.turn = fenParsed.turn[0]; //[0] to work with MarseilleRules
472 this.movesCount = parseInt(fenParsed.movesCount);
473 this.setOtherVariables(fen);
474 }
475
476 // Scan board for kings positions
477 scanKings(fen) {
478 this.INIT_COL_KING = { w: -1, b: -1 };
479 // Squares of white and black king:
480 this.kingPos = { w: [-1, -1], b: [-1, -1] };
481 const fenRows = V.ParseFen(fen).position.split("/");
482 const startRow = { 'w': V.size.x - 1, 'b': 0 };
483 for (let i = 0; i < fenRows.length; i++) {
484 let k = 0; //column index on board
485 for (let j = 0; j < fenRows[i].length; j++) {
486 switch (fenRows[i].charAt(j)) {
487 case "k":
488 this.kingPos["b"] = [i, k];
489 this.INIT_COL_KING["b"] = k;
490 break;
491 case "K":
492 this.kingPos["w"] = [i, k];
493 this.INIT_COL_KING["w"] = k;
494 break;
495 default: {
496 const num = parseInt(fenRows[i].charAt(j));
497 if (!isNaN(num)) k += num - 1;
498 }
499 }
500 k++;
501 }
502 }
503 }
504
505 // Some additional variables from FEN (variant dependant)
506 setOtherVariables(fen) {
507 // Set flags and enpassant:
508 const parsedFen = V.ParseFen(fen);
509 if (V.HasFlags) this.setFlags(parsedFen.flags);
510 if (V.HasEnpassant) {
511 const epSq =
512 parsedFen.enpassant != "-"
513 ? this.getEpSquare(parsedFen.enpassant)
514 : undefined;
515 this.epSquares = [epSq];
516 }
517 // Search for kings positions:
518 this.scanKings(fen);
519 }
520
521 /////////////////////
522 // GETTERS & SETTERS
523
524 static get size() {
525 return { x: 8, y: 8 };
526 }
527
528 // Color of thing on square (i,j). 'undefined' if square is empty
529 getColor(i, j) {
530 return this.board[i][j].charAt(0);
531 }
532
533 // Piece type on square (i,j). 'undefined' if square is empty
534 getPiece(i, j) {
535 return this.board[i][j].charAt(1);
536 }
537
538 // Get opponent color
539 static GetOppCol(color) {
540 return color == "w" ? "b" : "w";
541 }
542
543 // Pieces codes (for a clearer code)
544 static get PAWN() {
545 return "p";
546 }
547 static get ROOK() {
548 return "r";
549 }
550 static get KNIGHT() {
551 return "n";
552 }
553 static get BISHOP() {
554 return "b";
555 }
556 static get QUEEN() {
557 return "q";
558 }
559 static get KING() {
560 return "k";
561 }
562
563 // For FEN checking:
564 static get PIECES() {
565 return [V.PAWN, V.ROOK, V.KNIGHT, V.BISHOP, V.QUEEN, V.KING];
566 }
567
568 // Empty square
569 static get EMPTY() {
570 return "";
571 }
572
573 // Some pieces movements
574 static get steps() {
575 return {
576 r: [
577 [-1, 0],
578 [1, 0],
579 [0, -1],
580 [0, 1]
581 ],
582 n: [
583 [-1, -2],
584 [-1, 2],
585 [1, -2],
586 [1, 2],
587 [-2, -1],
588 [-2, 1],
589 [2, -1],
590 [2, 1]
591 ],
592 b: [
593 [-1, -1],
594 [-1, 1],
595 [1, -1],
596 [1, 1]
597 ]
598 };
599 }
600
601 ////////////////////
602 // MOVES GENERATION
603
604 // All possible moves from selected square
605 getPotentialMovesFrom([x, y]) {
606 switch (this.getPiece(x, y)) {
607 case V.PAWN:
608 return this.getPotentialPawnMoves([x, y]);
609 case V.ROOK:
610 return this.getPotentialRookMoves([x, y]);
611 case V.KNIGHT:
612 return this.getPotentialKnightMoves([x, y]);
613 case V.BISHOP:
614 return this.getPotentialBishopMoves([x, y]);
615 case V.QUEEN:
616 return this.getPotentialQueenMoves([x, y]);
617 case V.KING:
618 return this.getPotentialKingMoves([x, y]);
619 }
620 return []; //never reached
621 }
622
623 // Build a regular move from its initial and destination squares.
624 // tr: transformation
625 getBasicMove([sx, sy], [ex, ey], tr) {
626 const initColor = this.getColor(sx, sy);
627 const initPiece = this.getPiece(sx, sy);
628 let mv = new Move({
629 appear: [
630 new PiPo({
631 x: ex,
632 y: ey,
633 c: tr ? tr.c : initColor,
634 p: tr ? tr.p : initPiece
635 })
636 ],
637 vanish: [
638 new PiPo({
639 x: sx,
640 y: sy,
641 c: initColor,
642 p: initPiece
643 })
644 ]
645 });
646
647 // The opponent piece disappears if we take it
648 if (this.board[ex][ey] != V.EMPTY) {
649 mv.vanish.push(
650 new PiPo({
651 x: ex,
652 y: ey,
653 c: this.getColor(ex, ey),
654 p: this.getPiece(ex, ey)
655 })
656 );
657 }
658
659 return mv;
660 }
661
662 // Generic method to find possible moves of non-pawn pieces:
663 // "sliding or jumping"
664 getSlideNJumpMoves([x, y], steps, oneStep) {
665 let moves = [];
666 outerLoop: for (let step of steps) {
667 let i = x + step[0];
668 let j = y + step[1];
669 while (V.OnBoard(i, j) && this.board[i][j] == V.EMPTY) {
670 moves.push(this.getBasicMove([x, y], [i, j]));
671 if (oneStep) continue outerLoop;
672 i += step[0];
673 j += step[1];
674 }
675 if (V.OnBoard(i, j) && this.canTake([x, y], [i, j]))
676 moves.push(this.getBasicMove([x, y], [i, j]));
677 }
678 return moves;
679 }
680
681 // Special case of en-passant captures: treated separately
682 getEnpassantCaptures([x, y], shiftX) {
683 const Lep = this.epSquares.length;
684 const epSquare = this.epSquares[Lep - 1]; //always at least one element
685 let enpassantMove = null;
686 if (
687 !!epSquare &&
688 epSquare.x == x + shiftX &&
689 Math.abs(epSquare.y - y) == 1
690 ) {
691 enpassantMove = this.getBasicMove([x, y], [epSquare.x, epSquare.y]);
692 enpassantMove.vanish.push({
693 x: x,
694 y: epSquare.y,
695 // Captured piece is usually a pawn, but next line seems harmless
696 p: this.getPiece(x, epSquare.y),
697 c: this.getColor(x, epSquare.y)
698 });
699 }
700 return !!enpassantMove ? [enpassantMove] : [];
701 }
702
703 // Consider all potential promotions:
704 addPawnMoves([x1, y1], [x2, y2], moves, promotions) {
705 let finalPieces = [V.PAWN];
706 const color = this.turn;
707 const lastRank = (color == "w" ? 0 : V.size.x - 1);
708 if (x2 == lastRank) {
709 // promotions arg: special override for Hiddenqueen variant
710 if (!!promotions) finalPieces = promotions;
711 else if (!!V.PawnSpecs.promotions)
712 finalPieces = V.PawnSpecs.promotions;
713 }
714 let tr = null;
715 for (let piece of finalPieces) {
716 tr = (piece != V.PAWN ? { c: color, p: piece } : null);
717 moves.push(this.getBasicMove([x1, y1], [x2, y2], tr));
718 }
719 }
720
721 // What are the pawn moves from square x,y ?
722 getPotentialPawnMoves([x, y], promotions) {
723 const color = this.turn;
724 const [sizeX, sizeY] = [V.size.x, V.size.y];
725 const pawnShiftX = V.PawnSpecs.directions[color];
726 const firstRank = (color == "w" ? sizeX - 1 : 0);
727
728 // Pawn movements in shiftX direction:
729 const getPawnMoves = (shiftX) => {
730 let moves = [];
731 // NOTE: next condition is generally true (no pawn on last rank)
732 if (x + shiftX >= 0 && x + shiftX < sizeX) {
733 if (this.board[x + shiftX][y] == V.EMPTY) {
734 // One square forward
735 this.addPawnMoves([x, y], [x + shiftX, y], moves, promotions);
736 // Next condition because pawns on 1st rank can generally jump
737 if (
738 V.PawnSpecs.twoSquares &&
739 (
740 (color == 'w' && x >= V.size.x - 1 - V.PawnSpecs.initShift['w'])
741 ||
742 (color == 'b' && x <= V.PawnSpecs.initShift['b'])
743 )
744 ) {
745 if (this.board[x + 2 * shiftX][y] == V.EMPTY) {
746 // Two squares jump
747 moves.push(this.getBasicMove([x, y], [x + 2 * shiftX, y]));
748 if (
749 V.PawnSpecs.threeSquares &&
750 this.board[x + 3 * shiftX][y] == V.EMPTY
751 ) {
752 // Three squares jump
753 moves.push(this.getBasicMove([x, y], [x + 3 * shiftX, y]));
754 }
755 }
756 }
757 }
758 // Captures
759 if (V.PawnSpecs.canCapture) {
760 for (let shiftY of [-1, 1]) {
761 if (
762 y + shiftY >= 0 &&
763 y + shiftY < sizeY
764 ) {
765 if (
766 this.board[x + shiftX][y + shiftY] != V.EMPTY &&
767 this.canTake([x, y], [x + shiftX, y + shiftY])
768 ) {
769 this.addPawnMoves(
770 [x, y], [x + shiftX, y + shiftY],
771 moves, promotions
772 );
773 }
774 if (
775 V.PawnSpecs.captureBackward &&
776 x - shiftX >= 0 && x - shiftX < V.size.x &&
777 this.board[x - shiftX][y + shiftY] != V.EMPTY &&
778 this.canTake([x, y], [x - shiftX, y + shiftY])
779 ) {
780 this.addPawnMoves(
781 [x, y], [x + shiftX, y + shiftY],
782 moves, promotions
783 );
784 }
785 }
786 }
787 }
788 }
789 return moves;
790 }
791
792 let pMoves = getPawnMoves(pawnShiftX);
793 if (V.PawnSpecs.bidirectional)
794 pMoves = pMoves.concat(getPawnMoves(-pawnShiftX));
795
796 if (V.HasEnpassant) {
797 // NOTE: backward en-passant captures are not considered
798 // because no rules define them (for now).
799 Array.prototype.push.apply(
800 pMoves,
801 this.getEnpassantCaptures([x, y], pawnShiftX)
802 );
803 }
804
805 return pMoves;
806 }
807
808 // What are the rook moves from square x,y ?
809 getPotentialRookMoves(sq) {
810 return this.getSlideNJumpMoves(sq, V.steps[V.ROOK]);
811 }
812
813 // What are the knight moves from square x,y ?
814 getPotentialKnightMoves(sq) {
815 return this.getSlideNJumpMoves(sq, V.steps[V.KNIGHT], "oneStep");
816 }
817
818 // What are the bishop moves from square x,y ?
819 getPotentialBishopMoves(sq) {
820 return this.getSlideNJumpMoves(sq, V.steps[V.BISHOP]);
821 }
822
823 // What are the queen moves from square x,y ?
824 getPotentialQueenMoves(sq) {
825 return this.getSlideNJumpMoves(
826 sq,
827 V.steps[V.ROOK].concat(V.steps[V.BISHOP])
828 );
829 }
830
831 // What are the king moves from square x,y ?
832 getPotentialKingMoves(sq) {
833 // Initialize with normal moves
834 let moves = this.getSlideNJumpMoves(
835 sq,
836 V.steps[V.ROOK].concat(V.steps[V.BISHOP]),
837 "oneStep"
838 );
839 if (V.HasCastle) moves = moves.concat(this.getCastleMoves(sq));
840 return moves;
841 }
842
843 // "castleInCheck" arg to let some variants castle under check
844 getCastleMoves([x, y], castleInCheck) {
845 const c = this.getColor(x, y);
846 if (x != (c == "w" ? V.size.x - 1 : 0) || y != this.INIT_COL_KING[c])
847 return []; //x isn't first rank, or king has moved (shortcut)
848
849 // Castling ?
850 const oppCol = V.GetOppCol(c);
851 let moves = [];
852 let i = 0;
853 // King, then rook:
854 const finalSquares = [
855 [2, 3],
856 [V.size.y - 2, V.size.y - 3]
857 ];
858 castlingCheck: for (
859 let castleSide = 0;
860 castleSide < 2;
861 castleSide++ //large, then small
862 ) {
863 if (this.castleFlags[c][castleSide] >= V.size.y) continue;
864 // If this code is reached, rook and king are on initial position
865
866 // NOTE: in some variants this is not a rook
867 const rookPos = this.castleFlags[c][castleSide];
868 if (this.board[x][rookPos] == V.EMPTY || this.getColor(x, rookPos) != c)
869 // Rook is not here, or changed color (see Benedict)
870 continue;
871
872 // Nothing on the path of the king ? (and no checks)
873 const castlingPiece = this.getPiece(x, rookPos);
874 const finDist = finalSquares[castleSide][0] - y;
875 let step = finDist / Math.max(1, Math.abs(finDist));
876 i = y;
877 do {
878 if (
879 // NOTE: "castling" arg is used by some variants (Monster),
880 // where "isAttacked" is overloaded in an infinite-recursive way.
881 (!castleInCheck && this.isAttacked([x, i], oppCol, "castling")) ||
882 (this.board[x][i] != V.EMPTY &&
883 // NOTE: next check is enough, because of chessboard constraints
884 (this.getColor(x, i) != c ||
885 ![V.KING, castlingPiece].includes(this.getPiece(x, i))))
886 ) {
887 continue castlingCheck;
888 }
889 i += step;
890 } while (i != finalSquares[castleSide][0]);
891
892 // Nothing on the path to the rook?
893 step = castleSide == 0 ? -1 : 1;
894 for (i = y + step; i != rookPos; i += step) {
895 if (this.board[x][i] != V.EMPTY) continue castlingCheck;
896 }
897
898 // Nothing on final squares, except maybe king and castling rook?
899 for (i = 0; i < 2; i++) {
900 if (
901 finalSquares[castleSide][i] != rookPos &&
902 this.board[x][finalSquares[castleSide][i]] != V.EMPTY &&
903 (
904 this.getPiece(x, finalSquares[castleSide][i]) != V.KING ||
905 this.getColor(x, finalSquares[castleSide][i]) != c
906 )
907 ) {
908 continue castlingCheck;
909 }
910 }
911
912 // If this code is reached, castle is valid
913 moves.push(
914 new Move({
915 appear: [
916 new PiPo({
917 x: x,
918 y: finalSquares[castleSide][0],
919 p: V.KING,
920 c: c
921 }),
922 new PiPo({
923 x: x,
924 y: finalSquares[castleSide][1],
925 p: castlingPiece,
926 c: c
927 })
928 ],
929 vanish: [
930 new PiPo({ x: x, y: y, p: V.KING, c: c }),
931 new PiPo({ x: x, y: rookPos, p: castlingPiece, c: c })
932 ],
933 end:
934 Math.abs(y - rookPos) <= 2
935 ? { x: x, y: rookPos }
936 : { x: x, y: y + 2 * (castleSide == 0 ? -1 : 1) }
937 })
938 );
939 }
940
941 return moves;
942 }
943
944 ////////////////////
945 // MOVES VALIDATION
946
947 // For the interface: possible moves for the current turn from square sq
948 getPossibleMovesFrom(sq) {
949 return this.filterValid(this.getPotentialMovesFrom(sq));
950 }
951
952 // TODO: promotions (into R,B,N,Q) should be filtered only once
953 filterValid(moves) {
954 if (moves.length == 0) return [];
955 const color = this.turn;
956 return moves.filter(m => {
957 this.play(m);
958 const res = !this.underCheck(color);
959 this.undo(m);
960 return res;
961 });
962 }
963
964 getAllPotentialMoves() {
965 const color = this.turn;
966 let potentialMoves = [];
967 for (let i = 0; i < V.size.x; i++) {
968 for (let j = 0; j < V.size.y; j++) {
969 if (this.board[i][j] != V.EMPTY && this.getColor(i, j) == color) {
970 Array.prototype.push.apply(
971 potentialMoves,
972 this.getPotentialMovesFrom([i, j])
973 );
974 }
975 }
976 }
977 return potentialMoves;
978 }
979
980 // Search for all valid moves considering current turn
981 // (for engine and game end)
982 getAllValidMoves() {
983 return this.filterValid(this.getAllPotentialMoves());
984 }
985
986 // Stop at the first move found
987 // TODO: not really, it explores all moves from a square (one is enough).
988 atLeastOneMove() {
989 const color = this.turn;
990 for (let i = 0; i < V.size.x; i++) {
991 for (let j = 0; j < V.size.y; j++) {
992 if (this.getColor(i, j) == color) {
993 const moves = this.getPotentialMovesFrom([i, j]);
994 if (moves.length > 0) {
995 for (let k = 0; k < moves.length; k++) {
996 if (this.filterValid([moves[k]]).length > 0) return true;
997 }
998 }
999 }
1000 }
1001 }
1002 return false;
1003 }
1004
1005 // Check if pieces of given color are attacking (king) on square x,y
1006 isAttacked(sq, color) {
1007 return (
1008 this.isAttackedByPawn(sq, color) ||
1009 this.isAttackedByRook(sq, color) ||
1010 this.isAttackedByKnight(sq, color) ||
1011 this.isAttackedByBishop(sq, color) ||
1012 this.isAttackedByQueen(sq, color) ||
1013 this.isAttackedByKing(sq, color)
1014 );
1015 }
1016
1017 // Generic method for non-pawn pieces ("sliding or jumping"):
1018 // is x,y attacked by a piece of given color ?
1019 isAttackedBySlideNJump([x, y], color, piece, steps, oneStep) {
1020 for (let step of steps) {
1021 let rx = x + step[0],
1022 ry = y + step[1];
1023 while (V.OnBoard(rx, ry) && this.board[rx][ry] == V.EMPTY && !oneStep) {
1024 rx += step[0];
1025 ry += step[1];
1026 }
1027 if (
1028 V.OnBoard(rx, ry) &&
1029 this.getPiece(rx, ry) == piece &&
1030 this.getColor(rx, ry) == color
1031 ) {
1032 return true;
1033 }
1034 }
1035 return false;
1036 }
1037
1038 // Is square x,y attacked by 'color' pawns ?
1039 isAttackedByPawn([x, y], color) {
1040 const pawnShift = (color == "w" ? 1 : -1);
1041 if (x + pawnShift >= 0 && x + pawnShift < V.size.x) {
1042 for (let i of [-1, 1]) {
1043 if (
1044 y + i >= 0 &&
1045 y + i < V.size.y &&
1046 this.getPiece(x + pawnShift, y + i) == V.PAWN &&
1047 this.getColor(x + pawnShift, y + i) == color
1048 ) {
1049 return true;
1050 }
1051 }
1052 }
1053 return false;
1054 }
1055
1056 // Is square x,y attacked by 'color' rooks ?
1057 isAttackedByRook(sq, color) {
1058 return this.isAttackedBySlideNJump(sq, color, V.ROOK, V.steps[V.ROOK]);
1059 }
1060
1061 // Is square x,y attacked by 'color' knights ?
1062 isAttackedByKnight(sq, color) {
1063 return this.isAttackedBySlideNJump(
1064 sq,
1065 color,
1066 V.KNIGHT,
1067 V.steps[V.KNIGHT],
1068 "oneStep"
1069 );
1070 }
1071
1072 // Is square x,y attacked by 'color' bishops ?
1073 isAttackedByBishop(sq, color) {
1074 return this.isAttackedBySlideNJump(sq, color, V.BISHOP, V.steps[V.BISHOP]);
1075 }
1076
1077 // Is square x,y attacked by 'color' queens ?
1078 isAttackedByQueen(sq, color) {
1079 return this.isAttackedBySlideNJump(
1080 sq,
1081 color,
1082 V.QUEEN,
1083 V.steps[V.ROOK].concat(V.steps[V.BISHOP])
1084 );
1085 }
1086
1087 // Is square x,y attacked by 'color' king(s) ?
1088 isAttackedByKing(sq, color) {
1089 return this.isAttackedBySlideNJump(
1090 sq,
1091 color,
1092 V.KING,
1093 V.steps[V.ROOK].concat(V.steps[V.BISHOP]),
1094 "oneStep"
1095 );
1096 }
1097
1098 // Is color under check after his move ?
1099 underCheck(color) {
1100 return this.isAttacked(this.kingPos[color], V.GetOppCol(color));
1101 }
1102
1103 /////////////////
1104 // MOVES PLAYING
1105
1106 // Apply a move on board
1107 static PlayOnBoard(board, move) {
1108 for (let psq of move.vanish) board[psq.x][psq.y] = V.EMPTY;
1109 for (let psq of move.appear) board[psq.x][psq.y] = psq.c + psq.p;
1110 }
1111 // Un-apply the played move
1112 static UndoOnBoard(board, move) {
1113 for (let psq of move.appear) board[psq.x][psq.y] = V.EMPTY;
1114 for (let psq of move.vanish) board[psq.x][psq.y] = psq.c + psq.p;
1115 }
1116
1117 prePlay() {}
1118
1119 play(move) {
1120 // DEBUG:
1121 // if (!this.states) this.states = [];
1122 // const stateFen = this.getFen() + JSON.stringify(this.kingPos);
1123 // this.states.push(stateFen);
1124
1125 this.prePlay(move);
1126 // Save flags (for undo)
1127 if (V.HasFlags) move.flags = JSON.stringify(this.aggregateFlags());
1128 if (V.HasEnpassant) this.epSquares.push(this.getEpSquare(move));
1129 V.PlayOnBoard(this.board, move);
1130 this.turn = V.GetOppCol(this.turn);
1131 this.movesCount++;
1132 this.postPlay(move);
1133 }
1134
1135 updateCastleFlags(move, piece) {
1136 const c = V.GetOppCol(this.turn);
1137 const firstRank = (c == "w" ? V.size.x - 1 : 0);
1138 // Update castling flags if rooks are moved
1139 const oppCol = this.turn;
1140 const oppFirstRank = V.size.x - 1 - firstRank;
1141 if (piece == V.KING && move.appear.length > 0)
1142 this.castleFlags[c] = [V.size.y, V.size.y];
1143 else if (
1144 move.start.x == firstRank && //our rook moves?
1145 this.castleFlags[c].includes(move.start.y)
1146 ) {
1147 const flagIdx = (move.start.y == this.castleFlags[c][0] ? 0 : 1);
1148 this.castleFlags[c][flagIdx] = V.size.y;
1149 }
1150 // NOTE: not "else if" because a rook could take an opposing rook
1151 if (
1152 move.end.x == oppFirstRank && //we took opponent rook?
1153 this.castleFlags[oppCol].includes(move.end.y)
1154 ) {
1155 const flagIdx = (move.end.y == this.castleFlags[oppCol][0] ? 0 : 1);
1156 this.castleFlags[oppCol][flagIdx] = V.size.y;
1157 }
1158 }
1159
1160 // After move is played, update variables + flags
1161 postPlay(move) {
1162 const c = V.GetOppCol(this.turn);
1163 let piece = undefined;
1164 if (move.vanish.length >= 1)
1165 // Usual case, something is moved
1166 piece = move.vanish[0].p;
1167 else
1168 // Crazyhouse-like variants
1169 piece = move.appear[0].p;
1170
1171 // Update king position + flags
1172 if (piece == V.KING && move.appear.length > 0) {
1173 this.kingPos[c][0] = move.appear[0].x;
1174 this.kingPos[c][1] = move.appear[0].y;
1175 }
1176 if (V.HasCastle) this.updateCastleFlags(move, piece);
1177 }
1178
1179 preUndo() {}
1180
1181 undo(move) {
1182 this.preUndo(move);
1183 if (V.HasEnpassant) this.epSquares.pop();
1184 if (V.HasFlags) this.disaggregateFlags(JSON.parse(move.flags));
1185 V.UndoOnBoard(this.board, move);
1186 this.turn = V.GetOppCol(this.turn);
1187 this.movesCount--;
1188 this.postUndo(move);
1189
1190 // DEBUG:
1191 // const stateFen = this.getFen() + JSON.stringify(this.kingPos);
1192 // if (stateFen != this.states[this.states.length-1]) debugger;
1193 // this.states.pop();
1194 }
1195
1196 // After move is undo-ed *and flags resetted*, un-update other variables
1197 // TODO: more symmetry, by storing flags increment in move (?!)
1198 postUndo(move) {
1199 // (Potentially) Reset king position
1200 const c = this.getColor(move.start.x, move.start.y);
1201 if (this.getPiece(move.start.x, move.start.y) == V.KING)
1202 this.kingPos[c] = [move.start.x, move.start.y];
1203 }
1204
1205 ///////////////
1206 // END OF GAME
1207
1208 // What is the score ? (Interesting if game is over)
1209 getCurrentScore() {
1210 if (this.atLeastOneMove()) return "*";
1211 // Game over
1212 const color = this.turn;
1213 // No valid move: stalemate or checkmate?
1214 if (!this.underCheck(color)) return "1/2";
1215 // OK, checkmate
1216 return (color == "w" ? "0-1" : "1-0");
1217 }
1218
1219 ///////////////
1220 // ENGINE PLAY
1221
1222 // Pieces values
1223 static get VALUES() {
1224 return {
1225 p: 1,
1226 r: 5,
1227 n: 3,
1228 b: 3,
1229 q: 9,
1230 k: 1000
1231 };
1232 }
1233
1234 // "Checkmate" (unreachable eval)
1235 static get INFINITY() {
1236 return 9999;
1237 }
1238
1239 // At this value or above, the game is over
1240 static get THRESHOLD_MATE() {
1241 return V.INFINITY;
1242 }
1243
1244 // Search depth: 1,2 for e.g. higher branching factor, 4 for smaller
1245 static get SEARCH_DEPTH() {
1246 return 3;
1247 }
1248
1249 getComputerMove() {
1250 const maxeval = V.INFINITY;
1251 const color = this.turn;
1252 let moves1 = this.getAllValidMoves();
1253
1254 if (moves1.length == 0)
1255 // TODO: this situation should not happen
1256 return null;
1257
1258 // Rank moves using a min-max at depth 2 (if search_depth >= 2!)
1259 for (let i = 0; i < moves1.length; i++) {
1260 this.play(moves1[i]);
1261 const score1 = this.getCurrentScore();
1262 if (score1 != "*") {
1263 moves1[i].eval =
1264 score1 == "1/2"
1265 ? 0
1266 : (score1 == "1-0" ? 1 : -1) * maxeval;
1267 }
1268 if (V.SEARCH_DEPTH == 1 || score1 != "*") {
1269 if (!moves1[i].eval) moves1[i].eval = this.evalPosition();
1270 this.undo(moves1[i]);
1271 continue;
1272 }
1273 // Initial self evaluation is very low: "I'm checkmated"
1274 moves1[i].eval = (color == "w" ? -1 : 1) * maxeval;
1275 // Initial enemy evaluation is very low too, for him
1276 let eval2 = (color == "w" ? 1 : -1) * maxeval;
1277 // Second half-move:
1278 let moves2 = this.getAllValidMoves();
1279 for (let j = 0; j < moves2.length; j++) {
1280 this.play(moves2[j]);
1281 const score2 = this.getCurrentScore();
1282 let evalPos = 0; //1/2 value
1283 switch (score2) {
1284 case "*":
1285 evalPos = this.evalPosition();
1286 break;
1287 case "1-0":
1288 evalPos = maxeval;
1289 break;
1290 case "0-1":
1291 evalPos = -maxeval;
1292 break;
1293 }
1294 if (
1295 (color == "w" && evalPos < eval2) ||
1296 (color == "b" && evalPos > eval2)
1297 ) {
1298 eval2 = evalPos;
1299 }
1300 this.undo(moves2[j]);
1301 }
1302 if (
1303 (color == "w" && eval2 > moves1[i].eval) ||
1304 (color == "b" && eval2 < moves1[i].eval)
1305 ) {
1306 moves1[i].eval = eval2;
1307 }
1308 this.undo(moves1[i]);
1309 }
1310 moves1.sort((a, b) => {
1311 return (color == "w" ? 1 : -1) * (b.eval - a.eval);
1312 });
1313 // console.log(moves1.map(m => { return [this.getNotation(m), m.eval]; }));
1314
1315 // Skip depth 3+ if we found a checkmate (or if we are checkmated in 1...)
1316 if (V.SEARCH_DEPTH >= 3 && Math.abs(moves1[0].eval) < V.THRESHOLD_MATE) {
1317 for (let i = 0; i < moves1.length; i++) {
1318 this.play(moves1[i]);
1319 // 0.1 * oldEval : heuristic to avoid some bad moves (not all...)
1320 moves1[i].eval =
1321 0.1 * moves1[i].eval +
1322 this.alphabeta(V.SEARCH_DEPTH - 1, -maxeval, maxeval);
1323 this.undo(moves1[i]);
1324 }
1325 moves1.sort((a, b) => {
1326 return (color == "w" ? 1 : -1) * (b.eval - a.eval);
1327 });
1328 }
1329
1330 let candidates = [0];
1331 for (let i = 1; i < moves1.length && moves1[i].eval == moves1[0].eval; i++)
1332 candidates.push(i);
1333 return moves1[candidates[randInt(candidates.length)]];
1334 }
1335
1336 alphabeta(depth, alpha, beta) {
1337 const maxeval = V.INFINITY;
1338 const color = this.turn;
1339 const score = this.getCurrentScore();
1340 if (score != "*")
1341 return score == "1/2" ? 0 : (score == "1-0" ? 1 : -1) * maxeval;
1342 if (depth == 0) return this.evalPosition();
1343 const moves = this.getAllValidMoves();
1344 let v = color == "w" ? -maxeval : maxeval;
1345 if (color == "w") {
1346 for (let i = 0; i < moves.length; i++) {
1347 this.play(moves[i]);
1348 v = Math.max(v, this.alphabeta(depth - 1, alpha, beta));
1349 this.undo(moves[i]);
1350 alpha = Math.max(alpha, v);
1351 if (alpha >= beta) break; //beta cutoff
1352 }
1353 }
1354 else {
1355 // color=="b"
1356 for (let i = 0; i < moves.length; i++) {
1357 this.play(moves[i]);
1358 v = Math.min(v, this.alphabeta(depth - 1, alpha, beta));
1359 this.undo(moves[i]);
1360 beta = Math.min(beta, v);
1361 if (alpha >= beta) break; //alpha cutoff
1362 }
1363 }
1364 return v;
1365 }
1366
1367 evalPosition() {
1368 let evaluation = 0;
1369 // Just count material for now
1370 for (let i = 0; i < V.size.x; i++) {
1371 for (let j = 0; j < V.size.y; j++) {
1372 if (this.board[i][j] != V.EMPTY) {
1373 const sign = this.getColor(i, j) == "w" ? 1 : -1;
1374 evaluation += sign * V.VALUES[this.getPiece(i, j)];
1375 }
1376 }
1377 }
1378 return evaluation;
1379 }
1380
1381 /////////////////////////
1382 // MOVES + GAME NOTATION
1383 /////////////////////////
1384
1385 // Context: just before move is played, turn hasn't changed
1386 // TODO: un-ambiguous notation (switch on piece type, check directions...)
1387 getNotation(move) {
1388 if (move.appear.length == 2 && move.appear[0].p == V.KING)
1389 // Castle
1390 return move.end.y < move.start.y ? "0-0-0" : "0-0";
1391
1392 // Translate final square
1393 const finalSquare = V.CoordsToSquare(move.end);
1394
1395 const piece = this.getPiece(move.start.x, move.start.y);
1396 if (piece == V.PAWN) {
1397 // Pawn move
1398 let notation = "";
1399 if (move.vanish.length > move.appear.length) {
1400 // Capture
1401 const startColumn = V.CoordToColumn(move.start.y);
1402 notation = startColumn + "x" + finalSquare;
1403 }
1404 else notation = finalSquare;
1405 if (move.appear.length > 0 && move.appear[0].p != V.PAWN)
1406 // Promotion
1407 notation += "=" + move.appear[0].p.toUpperCase();
1408 return notation;
1409 }
1410 // Piece movement
1411 return (
1412 piece.toUpperCase() +
1413 (move.vanish.length > move.appear.length ? "x" : "") +
1414 finalSquare
1415 );
1416 }
1417
1418 static GetUnambiguousNotation(move) {
1419 // Machine-readable format with all the informations about the move
1420 return (
1421 (!!move.start && V.OnBoard(move.start.x, move.start.y)
1422 ? V.CoordsToSquare(move.start)
1423 : "-"
1424 ) + "." +
1425 (!!move.end && V.OnBoard(move.end.x, move.end.y)
1426 ? V.CoordsToSquare(move.end)
1427 : "-"
1428 ) + " " +
1429 (!!move.appear && move.appear.length > 0
1430 ? move.appear.map(a =>
1431 a.c + a.p + V.CoordsToSquare({ x: a.x, y: a.y })).join(".")
1432 : "-"
1433 ) + "/" +
1434 (!!move.vanish && move.vanish.length > 0
1435 ? move.vanish.map(a =>
1436 a.c + a.p + V.CoordsToSquare({ x: a.x, y: a.y })).join(".")
1437 : "-"
1438 )
1439 );
1440 }
1441 };