Clarify Synchrone rules
[vchess.git] / client / src / variants / Synchrone.js
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1import { ChessRules } from "@/base_rules";
2import { randInt } from "@/utils/alea";
3
4export class SynchroneRules extends ChessRules {
5 static get CanAnalyze() {
6 return true; //false;
7 }
8
9 static get ShowMoves() {
10 return "byrow";
11 }
12
13 static IsGoodFen(fen) {
14 if (!ChessRules.IsGoodFen(fen)) return false;
15 const fenParsed = V.ParseFen(fen);
16 // 5) Check whiteMove
17 if (
18 (
19 fenParsed.turn == "b" &&
20 // NOTE: do not check really JSON stringified move...
21 (!fenParsed.whiteMove || fenParsed.whiteMove == "-")
22 )
23 ||
24 (fenParsed.turn == "w" && fenParsed.whiteMove != "-")
25 ) {
26 return false;
27 }
28 return true;
29 }
30
31 static IsGoodEnpassant(enpassant) {
32 const epArray = enpassant.split(",");
33 if (![2, 3].includes(epArray.length)) return false;
34 epArray.forEach(epsq => {
35 if (epsq != "-") {
36 const ep = V.SquareToCoords(epsq);
37 if (isNaN(ep.x) || !V.OnBoard(ep)) return false;
38 }
39 });
40 return true;
41 }
42
43 static ParseFen(fen) {
44 const fenParts = fen.split(" ");
45 return Object.assign(
46 ChessRules.ParseFen(fen),
47 { whiteMove: fenParts[5] }
48 );
49 }
50
51 static GenRandInitFen(randomness) {
52 return ChessRules.GenRandInitFen(randomness).slice(0, -1) + "-,- -";
53 }
54
55 getFen() {
56 return super.getFen() + " " + this.getWhitemoveFen();
57 }
58
59 getFenForRepeat() {
60 return super.getFenForRepeat() + "_" + this.getWhitemoveFen();
61 }
62
63 setOtherVariables(fen) {
64 const parsedFen = V.ParseFen(fen);
65 this.setFlags(parsedFen.flags);
66 const epArray = parsedFen.enpassant.split(",");
67 this.epSquares = [];
68 epArray.forEach(epsq => this.epSquares.push(this.getEpSquare(epsq)));
69 super.scanKings(fen);
70 // Also init whiteMove
71 this.whiteMove =
72 parsedFen.whiteMove != "-"
73 ? JSON.parse(parsedFen.whiteMove)
74 : null;
75 }
76
77 // After undo(): no need to re-set INIT_COL_KING
78 scanKings() {
79 this.kingPos = { w: [-1, -1], b: [-1, -1] };
80 for (let i = 0; i < V.size.x; i++) {
81 for (let j = 0; j < V.size.y; j++) {
82 if (this.getPiece(i, j) == V.KING)
83 this.kingPos[this.getColor(i, j)] = [i, j];
84 }
85 }
86 }
87
88 getEnpassantFen() {
89 const L = this.epSquares.length;
90 let res = "";
91 const start = L - 2 - (this.turn == 'b' ? 1 : 0);
92 for (let i=start; i < L; i++) {
93 if (!this.epSquares[i]) res += "-,";
94 else res += V.CoordsToSquare(this.epSquares[i]) + ",";
95 }
96 return res.slice(0, -1);
97 }
98
99 getWhitemoveFen() {
100 if (!this.whiteMove) return "-";
101 return JSON.stringify({
102 start: this.whiteMove.start,
103 end: this.whiteMove.end,
104 appear: this.whiteMove.appear,
105 vanish: this.whiteMove.vanish
106 });
107 }
108
109 getPossibleMovesFrom([x, y]) {
110 let moves = this.filterValid(super.getPotentialMovesFrom([x, y]));
111 if (!this.underCheck(this.getColor(x, y)))
112 // Augment with potential recaptures, except if we are under check
113 Array.prototype.push.apply(moves, this.getRecaptures([x, y]));
114 return moves;
115 }
116
117 // Aux function used to find opponent and self captures
118 getCaptures(from, to, color) {
119 const sliderAttack = (xx, yy, allowedSteps) => {
120 const deltaX = xx - to[0],
121 absDeltaX = Math.abs(deltaX);
122 const deltaY = yy - to[1],
123 absDeltaY = Math.abs(deltaY);
124 const step = [ deltaX / absDeltaX || 0, deltaY / absDeltaY || 0 ];
125 if (
126 // Check that the step is a priori valid:
127 (absDeltaX != absDeltaY && deltaX != 0 && deltaY != 0) ||
128 allowedSteps.every(st => st[0] != step[0] || st[1] != step[1])
129 ) {
130 return null;
131 }
132 let sq = [ to[0] + step[0], to[1] + step[1] ];
133 while (sq[0] != xx || sq[1] != yy) {
134 // NOTE: no need to check OnBoard in this special case
135 if (this.board[sq[0]][sq[1]] != V.EMPTY) return null;
136 sq[0] += step[0];
137 sq[1] += step[1];
138 }
139 return this.getBasicMove([xx, yy], [to[0], to[1]]);
140 };
141 // Can I take on the square 'to' ?
142 // If yes, return the (list of) capturing move(s)
143 const getTargetedCaptures = ([i, j]) => {
144 let move = null;
145 // From [i, j]:
146 switch (this.getPiece(i, j)) {
147 case V.PAWN: {
148 // Pushed pawns move as enemy pawns
149 const shift = (color == 'w' ? 1 : -1);
150 if (to[0] + shift == i && Math.abs(to[1] - j) == 1)
151 move = this.getBasicMove([i, j], to);
152 break;
153 }
154 case V.KNIGHT: {
155 const deltaX = Math.abs(i - to[0]);
156 const deltaY = Math.abs(j - to[1]);
157 if (
158 deltaX + deltaY == 3 &&
159 [1, 2].includes(deltaX) &&
160 [1, 2].includes(deltaY)
161 ) {
162 move = this.getBasicMove([i, j], to);
163 }
164 break;
165 }
166 case V.KING:
167 if (Math.abs(i - to[0]) <= 1 && Math.abs(j - to[1]) <= 1)
168 move = this.getBasicMove([i, j], to);
169 break;
170 case V.ROOK: {
171 move = sliderAttack(i, j, V.steps[V.ROOK]);
172 break;
173 }
174 case V.BISHOP: {
175 move = sliderAttack(i, j, V.steps[V.BISHOP]);
176 break;
177 }
178 case V.QUEEN: {
179 move = sliderAttack(i, j, V.steps[V.ROOK].concat(V.steps[V.BISHOP]));
180 break;
181 }
182 }
183 return move;
184 };
185 let moves = [];
186 if (!!from) {
187 const theMove = getTargetedCaptures(from);
188 if (!!theMove) moves.push(theMove);
189 }
190 else {
191 for (let i=0; i<8; i++) {
192 for (let j=0; j<8; j++) {
193 if (this.getColor(i, j) == color) {
194 const newMove = getTargetedCaptures([i, j]);
195 if (!!newMove) moves.push(newMove);
196 }
197 }
198 }
199 }
200 return this.filterValid(moves);
201 }
202
203 getRecaptures(from) {
204 // 1) Generate all opponent's capturing moves
205 let oppCaptureMoves = [];
206 const color = this.turn;
207 const oppCol = V.GetOppCol(color);
208 for (let i=0; i<8; i++) {
209 for (let j=0; j<8; j++) {
210 if (
211 this.getColor(i, j) == color &&
212 // Do not consider king captures: self-captures of king are forbidden
213 this.getPiece(i, j) != V.KING
214 ) {
215 Array.prototype.push.apply(
216 oppCaptureMoves,
217 this.getCaptures(null, [i, j], oppCol)
218 );
219 }
220 }
221 }
222 // 2) Play each opponent's capture, and see if back-captures are possible:
223 // Lookup table to quickly decide if a move is already in list:
224 let moveSet = {};
225 let moves = [];
226 oppCaptureMoves.forEach(m => {
227 // If another opponent capture with same endpoint already processed, skip
228 const mHash = "m" + m.end.x + m.end.y;
229 if (!moveSet[mHash]) {
230 moveSet[mHash] = true;
231 // Just make enemy piece disappear, to clear potential path:
232 const justDisappear = {
233 appear: [],
234 vanish: [m.vanish[0]]
235 };
236 V.PlayOnBoard(this.board, justDisappear);
237 // Can I take on [m.end.x, m.end.y] ? If yes, add to list:
238 this.getCaptures(from, [m.end.x, m.end.y], color)
239 .forEach(cm => moves.push(cm));
240 V.UndoOnBoard(this.board, justDisappear);
241 }
242 });
243 return moves;
244 }
245
246 getAllValidMoves() {
247 // Return possible moves + potential recaptures
248 return super.getAllValidMoves().concat(this.getRecaptures());
249 }
250
251 filterValid(moves) {
252 if (moves.length == 0) return [];
253 // filterValid can be called when it's "not our turn":
254 const color = moves[0].vanish[0].c;
255 return moves.filter(m => {
256 const piece = m.vanish[0].p;
257 if (piece == V.KING) {
258 this.kingPos[color][0] = m.appear[0].x;
259 this.kingPos[color][1] = m.appear[0].y;
260 }
261 V.PlayOnBoard(this.board, m);
262 let res = !this.underCheck(color);
263 V.UndoOnBoard(this.board, m);
264 if (piece == V.KING) this.kingPos[color] = [m.start.x, m.start.y];
265 return res;
266 });
267 }
268
269 atLeastOneMove(color) {
270 const curTurn = this.turn;
271 this.turn = color;
272 const res = super.atLeastOneMove();
273 this.turn = curTurn;
274 return res;
275 }
276
277 // White and black (partial) moves were played: merge
278 resolveSynchroneMove(move) {
279 const m1 = this.whiteMove;
280 const m2 = move;
281 // For PlayOnBoard (no need for start / end, irrelevant)
282 let smove = {
283 appear: [],
284 vanish: [
285 m1.vanish[0],
286 m2.vanish[0]
287 ]
288 };
289 if ((m1.end.x != m2.end.x) || (m1.end.y != m2.end.y)) {
290 // Easy case: two independant moves (which may (self-)capture)
291 smove.appear.push(m1.appear[0]);
292 smove.appear.push(m2.appear[0]);
293 // "Captured" pieces may have moved:
294 if (m1.appear.length == 2) {
295 // Castle
296 smove.appear.push(m1.appear[1]);
297 smove.vanish.push(m1.vanish[1]);
298 } else if (
299 m1.vanish.length == 2 &&
300 (
301 m1.vanish[1].x != m2.start.x ||
302 m1.vanish[1].y != m2.start.y
303 )
304 ) {
305 smove.vanish.push(m1.vanish[1]);
306 }
307 if (m2.appear.length == 2) {
308 // Castle
309 smove.appear.push(m2.appear[1]);
310 smove.vanish.push(m2.vanish[1]);
311 } else if (
312 m2.vanish.length == 2 &&
313 (
314 m2.vanish[1].x != m1.start.x ||
315 m2.vanish[1].y != m1.start.y
316 )
317 ) {
318 smove.vanish.push(m2.vanish[1]);
319 }
320 } else {
321 // Collision:
322 if (m1.vanish.length == 1 && m2.vanish.length == 1) {
323 // Easy case: both disappear except if one is a king
324 const p1 = m1.vanish[0].p;
325 const p2 = m2.vanish[0].p;
326 if ([p1, p2].includes(V.KING)) {
327 smove.appear.push({
328 x: m1.end.x,
329 y: m1.end.y,
330 p: V.KING,
331 c: (p1 == V.KING ? 'w' : 'b')
332 });
333 }
334 } else {
335 // One move is a self-capture and the other a normal capture:
336 // only the self-capture appears
337 const selfCaptureMove =
338 m1.vanish[1].c == m1.vanish[0].c
339 ? m1
340 : m2;
341 smove.appear.push({
342 x: m1.end.x,
343 y: m1.end.y,
344 p: selfCaptureMove.appear[0].p,
345 c: selfCaptureMove.vanish[0].c
346 });
347 smove.vanish.push({
348 x: m1.end.x,
349 y: m1.end.y,
350 p: selfCaptureMove.vanish[1].p,
351 c: selfCaptureMove.vanish[0].c
352 });
353 }
354 }
355 return smove;
356 }
357
358 play(move) {
359 move.flags = JSON.stringify(this.aggregateFlags()); //save flags (for undo)
360 this.epSquares.push(this.getEpSquare(move));
361 // Do not play on board (would reveal the move...)
362 this.turn = V.GetOppCol(this.turn);
363 this.movesCount++;
364 this.postPlay(move);
365 }
366
367 updateCastleFlags(move) {
368 const firstRank = { 'w': V.size.x - 1, 'b': 0 };
369 move.appear.concat(move.vanish).forEach(av => {
370 for (let c of ['w', 'b']) {
371 if (av.x == firstRank[c] && this.castleFlags[c].includes(av.y)) {
372 const flagIdx = (av.y == this.castleFlags[c][0] ? 0 : 1);
373 this.castleFlags[c][flagIdx] = 8;
374 }
375 }
376 });
377 }
378
379 postPlay(move) {
380 if (this.turn == 'b') {
381 // NOTE: whiteMove is used read-only, so no need to copy
382 this.whiteMove = move;
383 return;
384 }
385
386 // A full turn just ended:
387 const smove = this.resolveSynchroneMove(move);
388 V.PlayOnBoard(this.board, smove);
389 move.whiteMove = this.whiteMove; //for undo
390 this.whiteMove = null;
391
392 // Update king position + flags
393 let kingAppear = { 'w': false, 'b': false };
394 for (let i=0; i<smove.appear.length; i++) {
395 if (smove.appear[i].p == V.KING) {
396 const c = smove.appear[i].c;
397 kingAppear[c] = true;
398 this.kingPos[c][0] = smove.appear[i].x;
399 this.kingPos[c][1] = smove.appear[i].y;
400 }
401 }
402 for (let i=0; i<smove.vanish.length; i++) {
403 if (smove.vanish[i].p == V.KING) {
404 const c = smove.vanish[i].c;
405 if (!kingAppear[c]) {
406 this.kingPos[c][0] = -1;
407 this.kingPos[c][1] = -1;
408 }
409 break;
410 }
411 }
412 this.updateCastleFlags(smove);
413 move.smove = smove;
414 }
415
416 undo(move) {
417 this.epSquares.pop();
418 this.disaggregateFlags(JSON.parse(move.flags));
419 if (this.turn == 'w')
420 // Back to the middle of the move
421 V.UndoOnBoard(this.board, move.smove);
422 this.turn = V.GetOppCol(this.turn);
423 this.movesCount--;
424 this.postUndo(move);
425 }
426
427 postUndo(move) {
428 if (this.turn == 'w') {
429 // Reset king positions: scan board
430 this.scanKings();
431 // Also reset whiteMove
432 this.whiteMove = null;
433 } else this.whiteMove = move.whiteMove;
434 }
435
436 getCheckSquares(color) {
437 if (color == 'b') {
438 // kingPos must be reset for appropriate highlighting:
439 var lastMove = JSON.parse(JSON.stringify(this.whiteMove));
440 this.undo(lastMove); //will erase whiteMove, thus saved above
441 }
442 let res = [];
443 if (this.kingPos['w'][0] >= 0 && this.underCheck('w'))
444 res.push(JSON.parse(JSON.stringify(this.kingPos['w'])));
445 if (this.kingPos['b'][0] >= 0 && this.underCheck('b'))
446 res.push(JSON.parse(JSON.stringify(this.kingPos['b'])));
447 if (color == 'b') this.play(lastMove);
448 return res;
449 }
450
451 getCurrentScore() {
452 if (this.turn == 'b')
453 // Turn (white + black) not over yet
454 return "*";
455 // Was a king captured?
456 if (this.kingPos['w'][0] < 0) return "0-1";
457 if (this.kingPos['b'][0] < 0) return "1-0";
458 const whiteCanMove = this.atLeastOneMove('w');
459 const blackCanMove = this.atLeastOneMove('b');
460 if (whiteCanMove && blackCanMove) return "*";
461 // Game over
462 const whiteInCheck = this.underCheck('w');
463 const blackInCheck = this.underCheck('b');
464 if (
465 (whiteCanMove && !this.underCheck('b')) ||
466 (blackCanMove && !this.underCheck('w'))
467 ) {
468 return "1/2";
469 }
470 // Checkmate: could be mutual
471 if (!whiteCanMove && !blackCanMove) return "1/2";
472 return (whiteCanMove ? "1-0" : "0-1");
473 }
474
475 getComputerMove() {
476 const maxeval = V.INFINITY;
477 const color = this.turn;
478 let moves = this.getAllValidMoves();
479 if (moves.length == 0)
480 // TODO: this situation should not happen
481 return null;
482
483 if (Math.random() < 0.5)
484 // Return a random move
485 return moves[randInt(moves.length)];
486
487 // Rank moves at depth 1:
488 // try to capture something (not re-capturing)
489 moves.forEach(m => {
490 V.PlayOnBoard(this.board, m);
491 m.eval = this.evalPosition();
492 V.UndoOnBoard(this.board, m);
493 });
494 moves.sort((a, b) => {
495 return (color == "w" ? 1 : -1) * (b.eval - a.eval);
496 });
497 let candidates = [0];
498 for (let i = 1; i < moves.length && moves[i].eval == moves[0].eval; i++)
499 candidates.push(i);
500 return moves[candidates[randInt(candidates.length)]];
501 }
502
503 getNotation(move) {
504 if (move.appear.length == 2 && move.appear[0].p == V.KING)
505 // Castle
506 return move.end.y < move.start.y ? "0-0-0" : "0-0";
507 // Basic system: piece + init + dest square
508 return (
509 move.vanish[0].p.toUpperCase() +
510 V.CoordsToSquare(move.start) +
511 V.CoordsToSquare(move.end)
512 );
513 }
514};