Early draft of Paco-Sako + some fixes
[vchess.git] / client / src / base_rules.js
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1// (Orthodox) Chess rules are defined in ChessRules class.
2// Variants generally inherit from it, and modify some parts.
3
e2732923 4import { ArrayFun } from "@/utils/array";
0c3fe8a6 5import { randInt, shuffle } from "@/utils/alea";
e2732923 6
910d631b 7// class "PiPo": Piece + Position
6808d7a1 8export const PiPo = class PiPo {
1c9f093d 9 // o: {piece[p], color[c], posX[x], posY[y]}
6808d7a1 10 constructor(o) {
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11 this.p = o.p;
12 this.c = o.c;
13 this.x = o.x;
14 this.y = o.y;
15 }
6808d7a1 16};
1d184b4c 17
6808d7a1 18export const Move = class Move {
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19 // o: {appear, vanish, [start,] [end,]}
20 // appear,vanish = arrays of PiPo
21 // start,end = coordinates to apply to trigger move visually (think castle)
6808d7a1 22 constructor(o) {
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23 this.appear = o.appear;
24 this.vanish = o.vanish;
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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 };
1c9f093d 27 }
6808d7a1 28};
1d184b4c 29
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30// NOTE: x coords = top to bottom; y = left to right
31// (from white player perspective)
6808d7a1 32export const ChessRules = class ChessRules {
7e8a7ea1 33
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34 //////////////
35 // MISC UTILS
36
20620465 37 // Some variants don't have flags:
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38 static get HasFlags() {
39 return true;
20620465 40 }
1c9f093d 41
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42 // Or castle
43 static get HasCastle() {
44 return V.HasFlags;
45 }
46
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47 // Pawns specifications
48 static get PawnSpecs() {
49 return {
50 directions: { 'w': -1, 'b': 1 },
472c0c4f 51 initShift: { w: 1, b: 1 },
32f6285e 52 twoSquares: true,
472c0c4f 53 threeSquares: false,
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54 promotions: [V.ROOK, V.KNIGHT, V.BISHOP, V.QUEEN],
55 canCapture: true,
56 captureBackward: false,
57 bidirectional: false
58 };
59 }
60
61 // En-passant captures need a stack of squares:
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62 static get HasEnpassant() {
63 return true;
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64 }
65
66 // Some variants cannot have analyse mode
8477e53d 67 static get CanAnalyze() {
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68 return true;
69 }
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70 // Patch: issues with javascript OOP, objects can't access static fields.
71 get canAnalyze() {
72 return V.CanAnalyze;
73 }
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74
75 // Some variants show incomplete information,
76 // and thus show only a partial moves list or no list at all.
77 static get ShowMoves() {
78 return "all";
79 }
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80 get showMoves() {
81 return V.ShowMoves;
82 }
1c9f093d 83
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84 // Sometimes moves must remain hidden until game ends
85 static get SomeHiddenMoves() {
86 return false;
87 }
88 get someHiddenMoves() {
89 return V.SomeHiddenMoves;
90 }
91
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92 // Generally true, unless the variant includes random effects
93 static get CorrConfirm() {
94 return true;
95 }
96
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97 // Used for Monochrome variant (TODO: harmonize: !canFlip ==> showFirstTurn)
98 get showFirstTurn() {
99 return false;
100 }
101
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102 // Some variants always show the same orientation
103 static get CanFlip() {
104 return true;
105 }
106 get canFlip() {
107 return V.CanFlip;
108 }
109
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110 // For (generally old) variants without checkered board
111 static get Monochrome() {
112 return false;
113 }
114
173f11dc 115 // Some games are drawn unusually (bottom right corner is black)
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116 static get DarkBottomRight() {
117 return false;
118 }
119
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120 // Some variants require lines drawing
121 static get Lines() {
122 if (V.Monochrome) {
123 let lines = [];
124 // Draw all inter-squares lines
125 for (let i = 0; i <= V.size.x; i++)
126 lines.push([[i, 0], [i, V.size.y]]);
127 for (let j = 0; j <= V.size.y; j++)
128 lines.push([[0, j], [V.size.x, j]]);
129 return lines;
130 }
131 return null;
132 }
133
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134 // In some variants, the player who repeat a position loses
135 static get LoseOnRepetition() {
136 return false;
137 }
138
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139 // Some variants use click infos:
140 doClick() {
141 return null;
142 }
143
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144 // Some variants may need to highlight squares on hover (Hamilton, Weiqi...)
145 hoverHighlight() {
146 return false;
147 }
148
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149 static get IMAGE_EXTENSION() {
150 // All pieces should be in the SVG format
151 return ".svg";
152 }
153
1c9f093d 154 // Turn "wb" into "B" (for FEN)
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155 static board2fen(b) {
156 return b[0] == "w" ? b[1].toUpperCase() : b[1];
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157 }
158
159 // Turn "p" into "bp" (for board)
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160 static fen2board(f) {
161 return f.charCodeAt() <= 90 ? "w" + f.toLowerCase() : "b" + f;
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162 }
163
68e19a44 164 // Check if FEN describes a board situation correctly
6808d7a1 165 static IsGoodFen(fen) {
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166 const fenParsed = V.ParseFen(fen);
167 // 1) Check position
6808d7a1 168 if (!V.IsGoodPosition(fenParsed.position)) return false;
1c9f093d 169 // 2) Check turn
6808d7a1 170 if (!fenParsed.turn || !V.IsGoodTurn(fenParsed.turn)) return false;
1c9f093d 171 // 3) Check moves count
e50a8025 172 if (!fenParsed.movesCount || !(parseInt(fenParsed.movesCount, 10) >= 0))
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173 return false;
174 // 4) Check flags
175 if (V.HasFlags && (!fenParsed.flags || !V.IsGoodFlags(fenParsed.flags)))
176 return false;
177 // 5) Check enpassant
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178 if (
179 V.HasEnpassant &&
180 (!fenParsed.enpassant || !V.IsGoodEnpassant(fenParsed.enpassant))
181 ) {
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182 return false;
183 }
184 return true;
185 }
186
187 // Is position part of the FEN a priori correct?
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188 static IsGoodPosition(position) {
189 if (position.length == 0) return false;
1c9f093d 190 const rows = position.split("/");
6808d7a1 191 if (rows.length != V.size.x) return false;
6f2f9437 192 let kings = { "k": 0, "K": 0 };
6808d7a1 193 for (let row of rows) {
1c9f093d 194 let sumElts = 0;
6808d7a1 195 for (let i = 0; i < row.length; i++) {
6f2f9437 196 if (['K','k'].includes(row[i])) kings[row[i]]++;
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197 if (V.PIECES.includes(row[i].toLowerCase())) sumElts++;
198 else {
e50a8025 199 const num = parseInt(row[i], 10);
173f11dc 200 if (isNaN(num) || num <= 0) return false;
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201 sumElts += num;
202 }
203 }
6808d7a1 204 if (sumElts != V.size.y) return false;
1c9f093d 205 }
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206 // Both kings should be on board. Exactly one per color.
207 if (Object.values(kings).some(v => v != 1)) return false;
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208 return true;
209 }
210
211 // For FEN checking
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212 static IsGoodTurn(turn) {
213 return ["w", "b"].includes(turn);
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214 }
215
216 // For FEN checking
6808d7a1 217 static IsGoodFlags(flags) {
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218 // NOTE: a little too permissive to work with more variants
219 return !!flags.match(/^[a-z]{4,4}$/);
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220 }
221
472c0c4f 222 // NOTE: not with regexp to adapt to different board sizes. (TODO?)
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223 static IsGoodEnpassant(enpassant) {
224 if (enpassant != "-") {
225 const ep = V.SquareToCoords(enpassant);
226 if (isNaN(ep.x) || !V.OnBoard(ep)) return false;
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227 }
228 return true;
229 }
230
231 // 3 --> d (column number to letter)
6808d7a1 232 static CoordToColumn(colnum) {
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233 return String.fromCharCode(97 + colnum);
234 }
235
236 // d --> 3 (column letter to number)
6808d7a1 237 static ColumnToCoord(column) {
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238 return column.charCodeAt(0) - 97;
239 }
240
241 // a4 --> {x:3,y:0}
6808d7a1 242 static SquareToCoords(sq) {
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243 return {
244 // NOTE: column is always one char => max 26 columns
245 // row is counted from black side => subtraction
e50a8025 246 x: V.size.x - parseInt(sq.substr(1), 10),
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247 y: sq[0].charCodeAt() - 97
248 };
249 }
250
251 // {x:0,y:4} --> e8
6808d7a1 252 static CoordsToSquare(coords) {
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253 return V.CoordToColumn(coords.y) + (V.size.x - coords.x);
254 }
255
305ede7e 256 // Path to pieces (standard ones in pieces/ folder)
241bf8f2 257 getPpath(b) {
305ede7e 258 return b;
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259 }
260
3a2a7b5f 261 // Path to promotion pieces (usually the same)
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262 getPPpath(m) {
263 return this.getPpath(m.appear[0].c + m.appear[0].p);
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264 }
265
1c9f093d 266 // Aggregates flags into one object
6808d7a1 267 aggregateFlags() {
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268 return this.castleFlags;
269 }
270
271 // Reverse operation
6808d7a1 272 disaggregateFlags(flags) {
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273 this.castleFlags = flags;
274 }
275
276 // En-passant square, if any
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277 getEpSquare(moveOrSquare) {
278 if (!moveOrSquare) return undefined;
279 if (typeof moveOrSquare === "string") {
1c9f093d 280 const square = moveOrSquare;
6808d7a1 281 if (square == "-") return undefined;
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282 return V.SquareToCoords(square);
283 }
284 // Argument is a move:
285 const move = moveOrSquare;
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286 const s = move.start,
287 e = move.end;
6808d7a1 288 if (
1c5bfdf2 289 s.y == e.y &&
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290 Math.abs(s.x - e.x) == 2 &&
291 // Next conditions for variants like Atomic or Rifle, Recycle...
292 (move.appear.length > 0 && move.appear[0].p == V.PAWN) &&
293 (move.vanish.length > 0 && move.vanish[0].p == V.PAWN)
6808d7a1 294 ) {
1c9f093d 295 return {
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296 x: (s.x + e.x) / 2,
297 y: s.y
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298 };
299 }
300 return undefined; //default
301 }
302
303 // Can thing on square1 take thing on square2
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304 canTake([x1, y1], [x2, y2]) {
305 return this.getColor(x1, y1) !== this.getColor(x2, y2);
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306 }
307
308 // Is (x,y) on the chessboard?
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309 static OnBoard(x, y) {
310 return x >= 0 && x < V.size.x && y >= 0 && y < V.size.y;
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311 }
312
313 // Used in interface: 'side' arg == player color
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314 canIplay(side, [x, y]) {
315 return this.turn == side && this.getColor(x, y) == side;
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316 }
317
318 // On which squares is color under check ? (for interface)
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319 getCheckSquares() {
320 const color = this.turn;
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321 return (
322 this.underCheck(color)
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323 // kingPos must be duplicated, because it may change:
324 ? [JSON.parse(JSON.stringify(this.kingPos[color]))]
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325 : []
326 );
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327 }
328
329 /////////////
330 // FEN UTILS
331
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332 // Setup the initial random (asymmetric) position
333 static GenRandInitFen(randomness) {
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334 if (randomness == 0)
335 // Deterministic:
3a2a7b5f 336 return "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w 0 ahah -";
7ba4a5bc 337
6808d7a1 338 let pieces = { w: new Array(8), b: new Array(8) };
3a2a7b5f 339 let flags = "";
7ba4a5bc 340 // Shuffle pieces on first (and last rank if randomness == 2)
6808d7a1 341 for (let c of ["w", "b"]) {
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342 if (c == 'b' && randomness == 1) {
343 pieces['b'] = pieces['w'];
3a2a7b5f 344 flags += flags;
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345 break;
346 }
347
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348 let positions = ArrayFun.range(8);
349
350 // Get random squares for bishops
656b1878 351 let randIndex = 2 * randInt(4);
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352 const bishop1Pos = positions[randIndex];
353 // The second bishop must be on a square of different color
656b1878 354 let randIndex_tmp = 2 * randInt(4) + 1;
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355 const bishop2Pos = positions[randIndex_tmp];
356 // Remove chosen squares
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357 positions.splice(Math.max(randIndex, randIndex_tmp), 1);
358 positions.splice(Math.min(randIndex, randIndex_tmp), 1);
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359
360 // Get random squares for knights
656b1878 361 randIndex = randInt(6);
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362 const knight1Pos = positions[randIndex];
363 positions.splice(randIndex, 1);
656b1878 364 randIndex = randInt(5);
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365 const knight2Pos = positions[randIndex];
366 positions.splice(randIndex, 1);
367
368 // Get random square for queen
656b1878 369 randIndex = randInt(4);
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370 const queenPos = positions[randIndex];
371 positions.splice(randIndex, 1);
372
373 // Rooks and king positions are now fixed,
374 // because of the ordering rook-king-rook
375 const rook1Pos = positions[0];
376 const kingPos = positions[1];
377 const rook2Pos = positions[2];
378
379 // Finally put the shuffled pieces in the board array
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380 pieces[c][rook1Pos] = "r";
381 pieces[c][knight1Pos] = "n";
382 pieces[c][bishop1Pos] = "b";
383 pieces[c][queenPos] = "q";
384 pieces[c][kingPos] = "k";
385 pieces[c][bishop2Pos] = "b";
386 pieces[c][knight2Pos] = "n";
387 pieces[c][rook2Pos] = "r";
3a2a7b5f 388 flags += V.CoordToColumn(rook1Pos) + V.CoordToColumn(rook2Pos);
1c9f093d 389 }
e3e2cc44 390 // Add turn + flags + enpassant
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391 return (
392 pieces["b"].join("") +
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393 "/pppppppp/8/8/8/8/PPPPPPPP/" +
394 pieces["w"].join("").toUpperCase() +
3a2a7b5f 395 " w 0 " + flags + " -"
e3e2cc44 396 );
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397 }
398
399 // "Parse" FEN: just return untransformed string data
6808d7a1 400 static ParseFen(fen) {
1c9f093d 401 const fenParts = fen.split(" ");
6808d7a1 402 let res = {
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403 position: fenParts[0],
404 turn: fenParts[1],
6808d7a1 405 movesCount: fenParts[2]
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406 };
407 let nextIdx = 3;
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408 if (V.HasFlags) Object.assign(res, { flags: fenParts[nextIdx++] });
409 if (V.HasEnpassant) Object.assign(res, { enpassant: fenParts[nextIdx] });
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410 return res;
411 }
412
413 // Return current fen (game state)
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414 getFen() {
415 return (
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416 this.getBaseFen() + " " +
417 this.getTurnFen() + " " +
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418 this.movesCount +
419 (V.HasFlags ? " " + this.getFlagsFen() : "") +
420 (V.HasEnpassant ? " " + this.getEnpassantFen() : "")
421 );
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422 }
423
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424 getFenForRepeat() {
425 // Omit movesCount, only variable allowed to differ
426 return (
427 this.getBaseFen() + "_" +
428 this.getTurnFen() +
429 (V.HasFlags ? "_" + this.getFlagsFen() : "") +
430 (V.HasEnpassant ? "_" + this.getEnpassantFen() : "")
431 );
432 }
433
1c9f093d 434 // Position part of the FEN string
6808d7a1 435 getBaseFen() {
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436 const format = (count) => {
437 // if more than 9 consecutive free spaces, break the integer,
438 // otherwise FEN parsing will fail.
439 if (count <= 9) return count;
440 // Currently only boards of size up to 11 or 12:
441 return "9" + (count - 9);
442 };
1c9f093d 443 let position = "";
6808d7a1 444 for (let i = 0; i < V.size.x; i++) {
1c9f093d 445 let emptyCount = 0;
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446 for (let j = 0; j < V.size.y; j++) {
447 if (this.board[i][j] == V.EMPTY) emptyCount++;
448 else {
449 if (emptyCount > 0) {
1c9f093d 450 // Add empty squares in-between
6f2f9437 451 position += format(emptyCount);
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452 emptyCount = 0;
453 }
454 position += V.board2fen(this.board[i][j]);
455 }
456 }
6808d7a1 457 if (emptyCount > 0) {
1c9f093d 458 // "Flush remainder"
6f2f9437 459 position += format(emptyCount);
1c9f093d 460 }
6808d7a1 461 if (i < V.size.x - 1) position += "/"; //separate rows
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462 }
463 return position;
464 }
465
6808d7a1 466 getTurnFen() {
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467 return this.turn;
468 }
469
470 // Flags part of the FEN string
6808d7a1 471 getFlagsFen() {
1c9f093d 472 let flags = "";
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473 // Castling flags
474 for (let c of ["w", "b"])
475 flags += this.castleFlags[c].map(V.CoordToColumn).join("");
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476 return flags;
477 }
478
479 // Enpassant part of the FEN string
6808d7a1 480 getEnpassantFen() {
1c9f093d 481 const L = this.epSquares.length;
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482 if (!this.epSquares[L - 1]) return "-"; //no en-passant
483 return V.CoordsToSquare(this.epSquares[L - 1]);
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484 }
485
486 // Turn position fen into double array ["wb","wp","bk",...]
6808d7a1 487 static GetBoard(position) {
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488 const rows = position.split("/");
489 let board = ArrayFun.init(V.size.x, V.size.y, "");
6808d7a1 490 for (let i = 0; i < rows.length; i++) {
1c9f093d 491 let j = 0;
6808d7a1 492 for (let indexInRow = 0; indexInRow < rows[i].length; indexInRow++) {
1c9f093d 493 const character = rows[i][indexInRow];
e50a8025 494 const num = parseInt(character, 10);
a13cbc0f 495 // If num is a number, just shift j:
6808d7a1 496 if (!isNaN(num)) j += num;
a13cbc0f 497 // Else: something at position i,j
6808d7a1 498 else board[i][j++] = V.fen2board(character);
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499 }
500 }
501 return board;
502 }
503
504 // Extract (relevant) flags from fen
6808d7a1 505 setFlags(fenflags) {
1c9f093d 506 // white a-castle, h-castle, black a-castle, h-castle
bb688df5 507 this.castleFlags = { w: [-1, -1], b: [-1, -1] };
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508 for (let i = 0; i < 4; i++) {
509 this.castleFlags[i < 2 ? "w" : "b"][i % 2] =
510 V.ColumnToCoord(fenflags.charAt(i));
511 }
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512 }
513
514 //////////////////
515 // INITIALIZATION
516
37cdcbf3 517 // Fen string fully describes the game state
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518 constructor(fen) {
519 if (!fen)
520 // In printDiagram() fen isn't supply because only getPpath() is used
521 // TODO: find a better solution!
522 return;
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523 const fenParsed = V.ParseFen(fen);
524 this.board = V.GetBoard(fenParsed.position);
af34341d 525 this.turn = fenParsed.turn;
e50a8025 526 this.movesCount = parseInt(fenParsed.movesCount, 10);
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527 this.setOtherVariables(fen);
528 }
529
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530 // Scan board for kings positions
531 scanKings(fen) {
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532 // Squares of white and black king:
533 this.kingPos = { w: [-1, -1], b: [-1, -1] };
1c9f093d 534 const fenRows = V.ParseFen(fen).position.split("/");
90e814b6 535 const startRow = { 'w': V.size.x - 1, 'b': 0 };
6808d7a1 536 for (let i = 0; i < fenRows.length; i++) {
1c9f093d 537 let k = 0; //column index on board
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538 for (let j = 0; j < fenRows[i].length; j++) {
539 switch (fenRows[i].charAt(j)) {
540 case "k":
541 this.kingPos["b"] = [i, k];
1c9f093d 542 break;
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543 case "K":
544 this.kingPos["w"] = [i, k];
1c9f093d 545 break;
6808d7a1 546 default: {
e50a8025 547 const num = parseInt(fenRows[i].charAt(j), 10);
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548 if (!isNaN(num)) k += num - 1;
549 }
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550 }
551 k++;
552 }
553 }
554 }
555
556 // Some additional variables from FEN (variant dependant)
6808d7a1 557 setOtherVariables(fen) {
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558 // Set flags and enpassant:
559 const parsedFen = V.ParseFen(fen);
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560 if (V.HasFlags) this.setFlags(parsedFen.flags);
561 if (V.HasEnpassant) {
562 const epSq =
563 parsedFen.enpassant != "-"
9bd6786b 564 ? this.getEpSquare(parsedFen.enpassant)
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BA
565 : undefined;
566 this.epSquares = [epSq];
1c9f093d 567 }
3a2a7b5f
BA
568 // Search for kings positions:
569 this.scanKings(fen);
1c9f093d
BA
570 }
571
572 /////////////////////
573 // GETTERS & SETTERS
574
6808d7a1
BA
575 static get size() {
576 return { x: 8, y: 8 };
1c9f093d
BA
577 }
578
0ba6420d 579 // Color of thing on square (i,j). 'undefined' if square is empty
6808d7a1 580 getColor(i, j) {
1c9f093d
BA
581 return this.board[i][j].charAt(0);
582 }
583
584 // Piece type on square (i,j). 'undefined' if square is empty
6808d7a1 585 getPiece(i, j) {
1c9f093d
BA
586 return this.board[i][j].charAt(1);
587 }
588
589 // Get opponent color
6808d7a1
BA
590 static GetOppCol(color) {
591 return color == "w" ? "b" : "w";
1c9f093d
BA
592 }
593
1c9f093d 594 // Pieces codes (for a clearer code)
6808d7a1
BA
595 static get PAWN() {
596 return "p";
597 }
598 static get ROOK() {
599 return "r";
600 }
601 static get KNIGHT() {
602 return "n";
603 }
604 static get BISHOP() {
605 return "b";
606 }
607 static get QUEEN() {
608 return "q";
609 }
610 static get KING() {
611 return "k";
612 }
1c9f093d
BA
613
614 // For FEN checking:
6808d7a1
BA
615 static get PIECES() {
616 return [V.PAWN, V.ROOK, V.KNIGHT, V.BISHOP, V.QUEEN, V.KING];
1c9f093d
BA
617 }
618
619 // Empty square
6808d7a1
BA
620 static get EMPTY() {
621 return "";
622 }
1c9f093d
BA
623
624 // Some pieces movements
6808d7a1 625 static get steps() {
1c9f093d 626 return {
6808d7a1
BA
627 r: [
628 [-1, 0],
629 [1, 0],
630 [0, -1],
631 [0, 1]
632 ],
633 n: [
634 [-1, -2],
635 [-1, 2],
636 [1, -2],
637 [1, 2],
638 [-2, -1],
639 [-2, 1],
640 [2, -1],
641 [2, 1]
642 ],
643 b: [
644 [-1, -1],
645 [-1, 1],
646 [1, -1],
647 [1, 1]
648 ]
1c9f093d
BA
649 };
650 }
651
652 ////////////////////
653 // MOVES GENERATION
654
0ba6420d 655 // All possible moves from selected square
173f11dc
BA
656 getPotentialMovesFrom(sq) {
657 switch (this.getPiece(sq[0], sq[1])) {
658 case V.PAWN: return this.getPotentialPawnMoves(sq);
659 case V.ROOK: return this.getPotentialRookMoves(sq);
660 case V.KNIGHT: return this.getPotentialKnightMoves(sq);
661 case V.BISHOP: return this.getPotentialBishopMoves(sq);
662 case V.QUEEN: return this.getPotentialQueenMoves(sq);
663 case V.KING: return this.getPotentialKingMoves(sq);
1c9f093d 664 }
6808d7a1 665 return []; //never reached
1c9f093d
BA
666 }
667
668 // Build a regular move from its initial and destination squares.
669 // tr: transformation
6808d7a1 670 getBasicMove([sx, sy], [ex, ey], tr) {
1c58eb76 671 const initColor = this.getColor(sx, sy);
7e8a7ea1 672 const initPiece = this.board[sx][sy].charAt(1);
1c9f093d
BA
673 let mv = new Move({
674 appear: [
675 new PiPo({
676 x: ex,
677 y: ey,
173f11dc
BA
678 c: !!tr ? tr.c : initColor,
679 p: !!tr ? tr.p : initPiece
1c9f093d
BA
680 })
681 ],
682 vanish: [
683 new PiPo({
684 x: sx,
685 y: sy,
1c58eb76
BA
686 c: initColor,
687 p: initPiece
1c9f093d
BA
688 })
689 ]
690 });
691
692 // The opponent piece disappears if we take it
6808d7a1 693 if (this.board[ex][ey] != V.EMPTY) {
1c9f093d
BA
694 mv.vanish.push(
695 new PiPo({
696 x: ex,
697 y: ey,
6808d7a1 698 c: this.getColor(ex, ey),
7e8a7ea1 699 p: this.board[ex][ey].charAt(1)
1c9f093d
BA
700 })
701 );
702 }
1c5bfdf2 703
1c9f093d
BA
704 return mv;
705 }
706
707 // Generic method to find possible moves of non-pawn pieces:
708 // "sliding or jumping"
6808d7a1 709 getSlideNJumpMoves([x, y], steps, oneStep) {
1c9f093d 710 let moves = [];
6808d7a1 711 outerLoop: for (let step of steps) {
1c9f093d
BA
712 let i = x + step[0];
713 let j = y + step[1];
6808d7a1
BA
714 while (V.OnBoard(i, j) && this.board[i][j] == V.EMPTY) {
715 moves.push(this.getBasicMove([x, y], [i, j]));
d1be8046 716 if (oneStep) continue outerLoop;
1c9f093d
BA
717 i += step[0];
718 j += step[1];
719 }
6808d7a1
BA
720 if (V.OnBoard(i, j) && this.canTake([x, y], [i, j]))
721 moves.push(this.getBasicMove([x, y], [i, j]));
1c9f093d
BA
722 }
723 return moves;
724 }
725
32f6285e
BA
726 // Special case of en-passant captures: treated separately
727 getEnpassantCaptures([x, y], shiftX) {
728 const Lep = this.epSquares.length;
729 const epSquare = this.epSquares[Lep - 1]; //always at least one element
730 let enpassantMove = null;
731 if (
732 !!epSquare &&
733 epSquare.x == x + shiftX &&
734 Math.abs(epSquare.y - y) == 1
735 ) {
736 enpassantMove = this.getBasicMove([x, y], [epSquare.x, epSquare.y]);
737 enpassantMove.vanish.push({
738 x: x,
739 y: epSquare.y,
7e8a7ea1 740 p: this.board[x][epSquare.y].charAt(1),
32f6285e
BA
741 c: this.getColor(x, epSquare.y)
742 });
743 }
744 return !!enpassantMove ? [enpassantMove] : [];
745 }
746
1c58eb76
BA
747 // Consider all potential promotions:
748 addPawnMoves([x1, y1], [x2, y2], moves, promotions) {
749 let finalPieces = [V.PAWN];
af34341d 750 const color = this.turn; //this.getColor(x1, y1);
1c58eb76
BA
751 const lastRank = (color == "w" ? 0 : V.size.x - 1);
752 if (x2 == lastRank) {
753 // promotions arg: special override for Hiddenqueen variant
754 if (!!promotions) finalPieces = promotions;
15d69043 755 else if (!!V.PawnSpecs.promotions) finalPieces = V.PawnSpecs.promotions;
1c58eb76
BA
756 }
757 let tr = null;
758 for (let piece of finalPieces) {
759 tr = (piece != V.PAWN ? { c: color, p: piece } : null);
760 moves.push(this.getBasicMove([x1, y1], [x2, y2], tr));
761 }
762 }
763
1c9f093d 764 // What are the pawn moves from square x,y ?
32f6285e 765 getPotentialPawnMoves([x, y], promotions) {
af34341d 766 const color = this.turn; //this.getColor(x, y);
6808d7a1 767 const [sizeX, sizeY] = [V.size.x, V.size.y];
32f6285e 768 const pawnShiftX = V.PawnSpecs.directions[color];
1c58eb76 769 const firstRank = (color == "w" ? sizeX - 1 : 0);
0b8bd121 770 const forward = (color == 'w' ? -1 : 1);
32f6285e
BA
771
772 // Pawn movements in shiftX direction:
773 const getPawnMoves = (shiftX) => {
774 let moves = [];
775 // NOTE: next condition is generally true (no pawn on last rank)
776 if (x + shiftX >= 0 && x + shiftX < sizeX) {
777 if (this.board[x + shiftX][y] == V.EMPTY) {
0b8bd121 778 // One square forward (or backward)
1c58eb76 779 this.addPawnMoves([x, y], [x + shiftX, y], moves, promotions);
32f6285e
BA
780 // Next condition because pawns on 1st rank can generally jump
781 if (
782 V.PawnSpecs.twoSquares &&
472c0c4f
BA
783 (
784 (color == 'w' && x >= V.size.x - 1 - V.PawnSpecs.initShift['w'])
785 ||
786 (color == 'b' && x <= V.PawnSpecs.initShift['b'])
787 )
32f6285e 788 ) {
0b8bd121
BA
789 if (
790 shiftX == forward &&
791 this.board[x + 2 * shiftX][y] == V.EMPTY
792 ) {
472c0c4f
BA
793 // Two squares jump
794 moves.push(this.getBasicMove([x, y], [x + 2 * shiftX, y]));
795 if (
796 V.PawnSpecs.threeSquares &&
797 this.board[x + 3 * shiftX][y] == V.EMPTY
798 ) {
799 // Three squares jump
800 moves.push(this.getBasicMove([x, y], [x + 3 * shiftX, y]));
801 }
802 }
32f6285e
BA
803 }
804 }
805 // Captures
806 if (V.PawnSpecs.canCapture) {
807 for (let shiftY of [-1, 1]) {
15d69043 808 if (y + shiftY >= 0 && y + shiftY < sizeY) {
32f6285e
BA
809 if (
810 this.board[x + shiftX][y + shiftY] != V.EMPTY &&
811 this.canTake([x, y], [x + shiftX, y + shiftY])
812 ) {
1c58eb76
BA
813 this.addPawnMoves(
814 [x, y], [x + shiftX, y + shiftY],
815 moves, promotions
816 );
32f6285e
BA
817 }
818 if (
0b8bd121 819 V.PawnSpecs.captureBackward && shiftX == forward &&
32f6285e
BA
820 x - shiftX >= 0 && x - shiftX < V.size.x &&
821 this.board[x - shiftX][y + shiftY] != V.EMPTY &&
822 this.canTake([x, y], [x - shiftX, y + shiftY])
823 ) {
1c58eb76 824 this.addPawnMoves(
0b8bd121 825 [x, y], [x - shiftX, y + shiftY],
1c58eb76
BA
826 moves, promotions
827 );
32f6285e
BA
828 }
829 }
1c9f093d
BA
830 }
831 }
832 }
32f6285e 833 return moves;
1c9f093d
BA
834 }
835
32f6285e
BA
836 let pMoves = getPawnMoves(pawnShiftX);
837 if (V.PawnSpecs.bidirectional)
838 pMoves = pMoves.concat(getPawnMoves(-pawnShiftX));
839
6808d7a1 840 if (V.HasEnpassant) {
32f6285e
BA
841 // NOTE: backward en-passant captures are not considered
842 // because no rules define them (for now).
843 Array.prototype.push.apply(
844 pMoves,
845 this.getEnpassantCaptures([x, y], pawnShiftX)
846 );
1c9f093d 847 }
294fe29f 848
32f6285e 849 return pMoves;
1c9f093d
BA
850 }
851
852 // What are the rook moves from square x,y ?
6808d7a1 853 getPotentialRookMoves(sq) {
1c9f093d
BA
854 return this.getSlideNJumpMoves(sq, V.steps[V.ROOK]);
855 }
856
857 // What are the knight moves from square x,y ?
6808d7a1 858 getPotentialKnightMoves(sq) {
1c9f093d
BA
859 return this.getSlideNJumpMoves(sq, V.steps[V.KNIGHT], "oneStep");
860 }
861
862 // What are the bishop moves from square x,y ?
6808d7a1 863 getPotentialBishopMoves(sq) {
1c9f093d
BA
864 return this.getSlideNJumpMoves(sq, V.steps[V.BISHOP]);
865 }
866
867 // What are the queen moves from square x,y ?
6808d7a1
BA
868 getPotentialQueenMoves(sq) {
869 return this.getSlideNJumpMoves(
870 sq,
871 V.steps[V.ROOK].concat(V.steps[V.BISHOP])
872 );
1c9f093d
BA
873 }
874
875 // What are the king moves from square x,y ?
6808d7a1 876 getPotentialKingMoves(sq) {
1c9f093d 877 // Initialize with normal moves
c583ef1c 878 let moves = this.getSlideNJumpMoves(
6808d7a1
BA
879 sq,
880 V.steps[V.ROOK].concat(V.steps[V.BISHOP]),
881 "oneStep"
882 );
7e8a7ea1
BA
883 if (V.HasCastle && this.castleFlags[this.turn].some(v => v < V.size.y))
884 moves = moves.concat(this.getCastleMoves(sq));
c583ef1c 885 return moves;
1c9f093d
BA
886 }
887
a6836242 888 // "castleInCheck" arg to let some variants castle under check
7e8a7ea1 889 getCastleMoves([x, y], finalSquares, castleInCheck, castleWith) {
6808d7a1 890 const c = this.getColor(x, y);
1c9f093d
BA
891
892 // Castling ?
893 const oppCol = V.GetOppCol(c);
894 let moves = [];
895 let i = 0;
9bd6786b 896 // King, then rook:
7e8a7ea1
BA
897 finalSquares = finalSquares || [ [2, 3], [V.size.y - 2, V.size.y - 3] ];
898 const castlingKing = this.board[x][y].charAt(1);
6808d7a1
BA
899 castlingCheck: for (
900 let castleSide = 0;
901 castleSide < 2;
902 castleSide++ //large, then small
903 ) {
3a2a7b5f 904 if (this.castleFlags[c][castleSide] >= V.size.y) continue;
3f22c2c3 905 // If this code is reached, rook and king are on initial position
1c9f093d 906
2c5d7b20 907 // NOTE: in some variants this is not a rook
32f6285e 908 const rookPos = this.castleFlags[c][castleSide];
7e8a7ea1 909 const castlingPiece = this.board[x][rookPos].charAt(1);
85a1dcba
BA
910 if (
911 this.board[x][rookPos] == V.EMPTY ||
912 this.getColor(x, rookPos) != c ||
7e8a7ea1 913 (!!castleWith && !castleWith.includes(castlingPiece))
85a1dcba 914 ) {
61656127 915 // Rook is not here, or changed color (see Benedict)
32f6285e 916 continue;
85a1dcba 917 }
32f6285e 918
2beba6db
BA
919 // Nothing on the path of the king ? (and no checks)
920 const finDist = finalSquares[castleSide][0] - y;
921 let step = finDist / Math.max(1, Math.abs(finDist));
922 i = y;
6808d7a1
BA
923 do {
924 if (
7e8a7ea1
BA
925 (!castleInCheck && this.isAttacked([x, i], oppCol)) ||
926 (
927 this.board[x][i] != V.EMPTY &&
6808d7a1 928 // NOTE: next check is enough, because of chessboard constraints
7e8a7ea1
BA
929 (this.getColor(x, i) != c || ![y, rookPos].includes(i))
930 )
6808d7a1 931 ) {
1c9f093d
BA
932 continue castlingCheck;
933 }
2beba6db 934 i += step;
6808d7a1 935 } while (i != finalSquares[castleSide][0]);
1c9f093d
BA
936
937 // Nothing on the path to the rook?
6808d7a1 938 step = castleSide == 0 ? -1 : 1;
3a2a7b5f 939 for (i = y + step; i != rookPos; i += step) {
6808d7a1 940 if (this.board[x][i] != V.EMPTY) continue castlingCheck;
1c9f093d 941 }
1c9f093d
BA
942
943 // Nothing on final squares, except maybe king and castling rook?
6808d7a1
BA
944 for (i = 0; i < 2; i++) {
945 if (
5e1bc651 946 finalSquares[castleSide][i] != rookPos &&
6808d7a1 947 this.board[x][finalSquares[castleSide][i]] != V.EMPTY &&
5e1bc651 948 (
7e8a7ea1 949 finalSquares[castleSide][i] != y ||
5e1bc651
BA
950 this.getColor(x, finalSquares[castleSide][i]) != c
951 )
6808d7a1 952 ) {
1c9f093d
BA
953 continue castlingCheck;
954 }
955 }
956
957 // If this code is reached, castle is valid
6808d7a1
BA
958 moves.push(
959 new Move({
960 appear: [
2c5d7b20
BA
961 new PiPo({
962 x: x,
963 y: finalSquares[castleSide][0],
7e8a7ea1 964 p: castlingKing,
2c5d7b20
BA
965 c: c
966 }),
967 new PiPo({
968 x: x,
969 y: finalSquares[castleSide][1],
970 p: castlingPiece,
971 c: c
972 })
6808d7a1
BA
973 ],
974 vanish: [
7e8a7ea1 975 // King might be initially disguised (Titan...)
a19caec0 976 new PiPo({ x: x, y: y, p: castlingKing, c: c }),
a6836242 977 new PiPo({ x: x, y: rookPos, p: castlingPiece, c: c })
6808d7a1
BA
978 ],
979 end:
980 Math.abs(y - rookPos) <= 2
981 ? { x: x, y: rookPos }
982 : { x: x, y: y + 2 * (castleSide == 0 ? -1 : 1) }
983 })
984 );
1c9f093d
BA
985 }
986
987 return moves;
988 }
989
990 ////////////////////
991 // MOVES VALIDATION
992
993 // For the interface: possible moves for the current turn from square sq
6808d7a1
BA
994 getPossibleMovesFrom(sq) {
995 return this.filterValid(this.getPotentialMovesFrom(sq));
1c9f093d
BA
996 }
997
998 // TODO: promotions (into R,B,N,Q) should be filtered only once
6808d7a1
BA
999 filterValid(moves) {
1000 if (moves.length == 0) return [];
1c9f093d
BA
1001 const color = this.turn;
1002 return moves.filter(m => {
1003 this.play(m);
1004 const res = !this.underCheck(color);
1005 this.undo(m);
1006 return res;
1007 });
1008 }
1009
5e1bc651 1010 getAllPotentialMoves() {
1c9f093d 1011 const color = this.turn;
1c9f093d 1012 let potentialMoves = [];
6808d7a1
BA
1013 for (let i = 0; i < V.size.x; i++) {
1014 for (let j = 0; j < V.size.y; j++) {
156986e6 1015 if (this.board[i][j] != V.EMPTY && this.getColor(i, j) == color) {
6808d7a1
BA
1016 Array.prototype.push.apply(
1017 potentialMoves,
1018 this.getPotentialMovesFrom([i, j])
1019 );
1c9f093d
BA
1020 }
1021 }
1022 }
5e1bc651
BA
1023 return potentialMoves;
1024 }
1025
1026 // Search for all valid moves considering current turn
1027 // (for engine and game end)
1028 getAllValidMoves() {
1029 return this.filterValid(this.getAllPotentialMoves());
1c9f093d
BA
1030 }
1031
1032 // Stop at the first move found
2c5d7b20 1033 // TODO: not really, it explores all moves from a square (one is enough).
6808d7a1 1034 atLeastOneMove() {
1c9f093d 1035 const color = this.turn;
6808d7a1
BA
1036 for (let i = 0; i < V.size.x; i++) {
1037 for (let j = 0; j < V.size.y; j++) {
665eed90 1038 if (this.board[i][j] != V.EMPTY && this.getColor(i, j) == color) {
6808d7a1
BA
1039 const moves = this.getPotentialMovesFrom([i, j]);
1040 if (moves.length > 0) {
107dc1bd 1041 for (let k = 0; k < moves.length; k++)
6808d7a1 1042 if (this.filterValid([moves[k]]).length > 0) return true;
1c9f093d
BA
1043 }
1044 }
1045 }
1046 }
1047 return false;
1048 }
1049
68e19a44
BA
1050 // Check if pieces of given color are attacking (king) on square x,y
1051 isAttacked(sq, color) {
6808d7a1 1052 return (
68e19a44
BA
1053 this.isAttackedByPawn(sq, color) ||
1054 this.isAttackedByRook(sq, color) ||
1055 this.isAttackedByKnight(sq, color) ||
1056 this.isAttackedByBishop(sq, color) ||
1057 this.isAttackedByQueen(sq, color) ||
1058 this.isAttackedByKing(sq, color)
6808d7a1 1059 );
1c9f093d
BA
1060 }
1061
d1be8046 1062 // Generic method for non-pawn pieces ("sliding or jumping"):
68e19a44
BA
1063 // is x,y attacked by a piece of given color ?
1064 isAttackedBySlideNJump([x, y], color, piece, steps, oneStep) {
d1be8046
BA
1065 for (let step of steps) {
1066 let rx = x + step[0],
1067 ry = y + step[1];
1068 while (V.OnBoard(rx, ry) && this.board[rx][ry] == V.EMPTY && !oneStep) {
1069 rx += step[0];
1070 ry += step[1];
1071 }
1072 if (
1073 V.OnBoard(rx, ry) &&
68e19a44
BA
1074 this.getPiece(rx, ry) == piece &&
1075 this.getColor(rx, ry) == color
d1be8046
BA
1076 ) {
1077 return true;
1078 }
1079 }
1080 return false;
1081 }
1082
68e19a44 1083 // Is square x,y attacked by 'color' pawns ?
107dc1bd 1084 isAttackedByPawn(sq, color) {
68e19a44 1085 const pawnShift = (color == "w" ? 1 : -1);
107dc1bd
BA
1086 return this.isAttackedBySlideNJump(
1087 sq,
1088 color,
1089 V.PAWN,
1090 [[pawnShift, 1], [pawnShift, -1]],
1091 "oneStep"
1092 );
1c9f093d
BA
1093 }
1094
68e19a44
BA
1095 // Is square x,y attacked by 'color' rooks ?
1096 isAttackedByRook(sq, color) {
1097 return this.isAttackedBySlideNJump(sq, color, V.ROOK, V.steps[V.ROOK]);
1c9f093d
BA
1098 }
1099
68e19a44
BA
1100 // Is square x,y attacked by 'color' knights ?
1101 isAttackedByKnight(sq, color) {
6808d7a1
BA
1102 return this.isAttackedBySlideNJump(
1103 sq,
68e19a44 1104 color,
6808d7a1
BA
1105 V.KNIGHT,
1106 V.steps[V.KNIGHT],
1107 "oneStep"
1108 );
1c9f093d
BA
1109 }
1110
68e19a44
BA
1111 // Is square x,y attacked by 'color' bishops ?
1112 isAttackedByBishop(sq, color) {
1113 return this.isAttackedBySlideNJump(sq, color, V.BISHOP, V.steps[V.BISHOP]);
1c9f093d
BA
1114 }
1115
68e19a44
BA
1116 // Is square x,y attacked by 'color' queens ?
1117 isAttackedByQueen(sq, color) {
6808d7a1
BA
1118 return this.isAttackedBySlideNJump(
1119 sq,
68e19a44 1120 color,
6808d7a1
BA
1121 V.QUEEN,
1122 V.steps[V.ROOK].concat(V.steps[V.BISHOP])
1123 );
1c9f093d
BA
1124 }
1125
68e19a44
BA
1126 // Is square x,y attacked by 'color' king(s) ?
1127 isAttackedByKing(sq, color) {
6808d7a1
BA
1128 return this.isAttackedBySlideNJump(
1129 sq,
68e19a44 1130 color,
6808d7a1
BA
1131 V.KING,
1132 V.steps[V.ROOK].concat(V.steps[V.BISHOP]),
1133 "oneStep"
1134 );
1c9f093d
BA
1135 }
1136
1c9f093d 1137 // Is color under check after his move ?
6808d7a1 1138 underCheck(color) {
1c58eb76 1139 return this.isAttacked(this.kingPos[color], V.GetOppCol(color));
1c9f093d
BA
1140 }
1141
1142 /////////////////
1143 // MOVES PLAYING
1144
1145 // Apply a move on board
6808d7a1
BA
1146 static PlayOnBoard(board, move) {
1147 for (let psq of move.vanish) board[psq.x][psq.y] = V.EMPTY;
1148 for (let psq of move.appear) board[psq.x][psq.y] = psq.c + psq.p;
1c9f093d
BA
1149 }
1150 // Un-apply the played move
6808d7a1
BA
1151 static UndoOnBoard(board, move) {
1152 for (let psq of move.appear) board[psq.x][psq.y] = V.EMPTY;
1153 for (let psq of move.vanish) board[psq.x][psq.y] = psq.c + psq.p;
1c9f093d
BA
1154 }
1155
3a2a7b5f
BA
1156 prePlay() {}
1157
1158 play(move) {
1159 // DEBUG:
1160// if (!this.states) this.states = [];
1c58eb76 1161// const stateFen = this.getFen() + JSON.stringify(this.kingPos);
3a2a7b5f
BA
1162// this.states.push(stateFen);
1163
1164 this.prePlay(move);
2c5d7b20
BA
1165 // Save flags (for undo)
1166 if (V.HasFlags) move.flags = JSON.stringify(this.aggregateFlags());
3a2a7b5f
BA
1167 if (V.HasEnpassant) this.epSquares.push(this.getEpSquare(move));
1168 V.PlayOnBoard(this.board, move);
1169 this.turn = V.GetOppCol(this.turn);
1170 this.movesCount++;
1171 this.postPlay(move);
1172 }
1173
a9e1202b
BA
1174 updateCastleFlags(move, piece, color) {
1175 const c = color || V.GetOppCol(this.turn);
1c58eb76
BA
1176 const firstRank = (c == "w" ? V.size.x - 1 : 0);
1177 // Update castling flags if rooks are moved
c7550017 1178 const oppCol = this.turn;
1c58eb76 1179 const oppFirstRank = V.size.x - 1 - firstRank;
bb688df5
BA
1180 if (piece == V.KING && move.appear.length > 0)
1181 this.castleFlags[c] = [V.size.y, V.size.y];
1182 else if (
1c58eb76
BA
1183 move.start.x == firstRank && //our rook moves?
1184 this.castleFlags[c].includes(move.start.y)
1185 ) {
1186 const flagIdx = (move.start.y == this.castleFlags[c][0] ? 0 : 1);
1187 this.castleFlags[c][flagIdx] = V.size.y;
305ede7e
BA
1188 }
1189 // NOTE: not "else if" because a rook could take an opposing rook
1190 if (
1c58eb76
BA
1191 move.end.x == oppFirstRank && //we took opponent rook?
1192 this.castleFlags[oppCol].includes(move.end.y)
1193 ) {
1194 const flagIdx = (move.end.y == this.castleFlags[oppCol][0] ? 0 : 1);
1195 this.castleFlags[oppCol][flagIdx] = V.size.y;
1196 }
1197 }
1198
1c9f093d 1199 // After move is played, update variables + flags
3a2a7b5f
BA
1200 postPlay(move) {
1201 const c = V.GetOppCol(this.turn);
1c9f093d 1202 let piece = undefined;
3a2a7b5f 1203 if (move.vanish.length >= 1)
1c9f093d
BA
1204 // Usual case, something is moved
1205 piece = move.vanish[0].p;
3a2a7b5f 1206 else
1c9f093d
BA
1207 // Crazyhouse-like variants
1208 piece = move.appear[0].p;
1c9f093d
BA
1209
1210 // Update king position + flags
964eda04
BA
1211 if (piece == V.KING && move.appear.length > 0)
1212 this.kingPos[c] = [move.appear[0].x, move.appear[0].y];
bb688df5 1213 if (V.HasCastle) this.updateCastleFlags(move, piece);
1c9f093d
BA
1214 }
1215
3a2a7b5f 1216 preUndo() {}
1c9f093d 1217
6808d7a1 1218 undo(move) {
3a2a7b5f 1219 this.preUndo(move);
6808d7a1
BA
1220 if (V.HasEnpassant) this.epSquares.pop();
1221 if (V.HasFlags) this.disaggregateFlags(JSON.parse(move.flags));
1c9f093d
BA
1222 V.UndoOnBoard(this.board, move);
1223 this.turn = V.GetOppCol(this.turn);
1224 this.movesCount--;
3a2a7b5f 1225 this.postUndo(move);
1c9f093d
BA
1226
1227 // DEBUG:
1c58eb76 1228// const stateFen = this.getFen() + JSON.stringify(this.kingPos);
9bd6786b
BA
1229// if (stateFen != this.states[this.states.length-1]) debugger;
1230// this.states.pop();
1c9f093d
BA
1231 }
1232
3a2a7b5f
BA
1233 // After move is undo-ed *and flags resetted*, un-update other variables
1234 // TODO: more symmetry, by storing flags increment in move (?!)
1235 postUndo(move) {
1236 // (Potentially) Reset king position
1237 const c = this.getColor(move.start.x, move.start.y);
1238 if (this.getPiece(move.start.x, move.start.y) == V.KING)
1239 this.kingPos[c] = [move.start.x, move.start.y];
1240 }
1241
1c9f093d
BA
1242 ///////////////
1243 // END OF GAME
1244
1245 // What is the score ? (Interesting if game is over)
6808d7a1 1246 getCurrentScore() {
bb688df5 1247 if (this.atLeastOneMove()) return "*";
1c9f093d
BA
1248 // Game over
1249 const color = this.turn;
1250 // No valid move: stalemate or checkmate?
bb688df5 1251 if (!this.underCheck(color)) return "1/2";
1c9f093d 1252 // OK, checkmate
68e19a44 1253 return (color == "w" ? "0-1" : "1-0");
1c9f093d
BA
1254 }
1255
1256 ///////////////
1257 // ENGINE PLAY
1258
1259 // Pieces values
6808d7a1 1260 static get VALUES() {
1c9f093d 1261 return {
6808d7a1
BA
1262 p: 1,
1263 r: 5,
1264 n: 3,
1265 b: 3,
1266 q: 9,
1267 k: 1000
1c9f093d
BA
1268 };
1269 }
1270
1271 // "Checkmate" (unreachable eval)
6808d7a1
BA
1272 static get INFINITY() {
1273 return 9999;
1274 }
1c9f093d
BA
1275
1276 // At this value or above, the game is over
6808d7a1
BA
1277 static get THRESHOLD_MATE() {
1278 return V.INFINITY;
1279 }
1c9f093d 1280
2c5d7b20 1281 // Search depth: 1,2 for e.g. higher branching factor, 4 for smaller
6808d7a1
BA
1282 static get SEARCH_DEPTH() {
1283 return 3;
1284 }
1c9f093d 1285
af34341d
BA
1286 // 'movesList' arg for some variants to provide a custom list
1287 getComputerMove(movesList) {
1c9f093d
BA
1288 const maxeval = V.INFINITY;
1289 const color = this.turn;
af34341d 1290 let moves1 = movesList || this.getAllValidMoves();
c322a844 1291
6808d7a1 1292 if (moves1.length == 0)
e71161fb 1293 // TODO: this situation should not happen
41cb9b94 1294 return null;
1c9f093d 1295
b83a675a 1296 // Rank moves using a min-max at depth 2 (if search_depth >= 2!)
6808d7a1 1297 for (let i = 0; i < moves1.length; i++) {
afbf3ca7
BA
1298 this.play(moves1[i]);
1299 const score1 = this.getCurrentScore();
1300 if (score1 != "*") {
1301 moves1[i].eval =
1302 score1 == "1/2"
1303 ? 0
1304 : (score1 == "1-0" ? 1 : -1) * maxeval;
1305 }
1306 if (V.SEARCH_DEPTH == 1 || score1 != "*") {
1307 if (!moves1[i].eval) moves1[i].eval = this.evalPosition();
1308 this.undo(moves1[i]);
b83a675a
BA
1309 continue;
1310 }
1c9f093d 1311 // Initial self evaluation is very low: "I'm checkmated"
6808d7a1 1312 moves1[i].eval = (color == "w" ? -1 : 1) * maxeval;
afbf3ca7
BA
1313 // Initial enemy evaluation is very low too, for him
1314 let eval2 = (color == "w" ? 1 : -1) * maxeval;
1315 // Second half-move:
1316 let moves2 = this.getAllValidMoves();
1317 for (let j = 0; j < moves2.length; j++) {
1318 this.play(moves2[j]);
1319 const score2 = this.getCurrentScore();
1320 let evalPos = 0; //1/2 value
1321 switch (score2) {
1322 case "*":
1323 evalPos = this.evalPosition();
1324 break;
1325 case "1-0":
1326 evalPos = maxeval;
1327 break;
1328 case "0-1":
1329 evalPos = -maxeval;
1330 break;
1c9f093d 1331 }
afbf3ca7
BA
1332 if (
1333 (color == "w" && evalPos < eval2) ||
1334 (color == "b" && evalPos > eval2)
1335 ) {
1336 eval2 = evalPos;
1337 }
1338 this.undo(moves2[j]);
1339 }
6808d7a1
BA
1340 if (
1341 (color == "w" && eval2 > moves1[i].eval) ||
1342 (color == "b" && eval2 < moves1[i].eval)
1343 ) {
1c9f093d
BA
1344 moves1[i].eval = eval2;
1345 }
1346 this.undo(moves1[i]);
1347 }
6808d7a1
BA
1348 moves1.sort((a, b) => {
1349 return (color == "w" ? 1 : -1) * (b.eval - a.eval);
1350 });
a97bdbda 1351// console.log(moves1.map(m => { return [this.getNotation(m), m.eval]; }));
1c9f093d 1352
1c9f093d 1353 // Skip depth 3+ if we found a checkmate (or if we are checkmated in 1...)
6808d7a1 1354 if (V.SEARCH_DEPTH >= 3 && Math.abs(moves1[0].eval) < V.THRESHOLD_MATE) {
6808d7a1 1355 for (let i = 0; i < moves1.length; i++) {
1c9f093d
BA
1356 this.play(moves1[i]);
1357 // 0.1 * oldEval : heuristic to avoid some bad moves (not all...)
6808d7a1
BA
1358 moves1[i].eval =
1359 0.1 * moves1[i].eval +
1360 this.alphabeta(V.SEARCH_DEPTH - 1, -maxeval, maxeval);
1c9f093d
BA
1361 this.undo(moves1[i]);
1362 }
6808d7a1
BA
1363 moves1.sort((a, b) => {
1364 return (color == "w" ? 1 : -1) * (b.eval - a.eval);
1365 });
b83a675a 1366 }
1c9f093d 1367
b83a675a 1368 let candidates = [0];
d54f6261
BA
1369 for (let i = 1; i < moves1.length && moves1[i].eval == moves1[0].eval; i++)
1370 candidates.push(i);
656b1878 1371 return moves1[candidates[randInt(candidates.length)]];
1c9f093d
BA
1372 }
1373
6808d7a1 1374 alphabeta(depth, alpha, beta) {
1c9f093d
BA
1375 const maxeval = V.INFINITY;
1376 const color = this.turn;
1377 const score = this.getCurrentScore();
1378 if (score != "*")
6808d7a1
BA
1379 return score == "1/2" ? 0 : (score == "1-0" ? 1 : -1) * maxeval;
1380 if (depth == 0) return this.evalPosition();
a97bdbda 1381 const moves = this.getAllValidMoves();
6808d7a1
BA
1382 let v = color == "w" ? -maxeval : maxeval;
1383 if (color == "w") {
1384 for (let i = 0; i < moves.length; i++) {
1c9f093d 1385 this.play(moves[i]);
6808d7a1 1386 v = Math.max(v, this.alphabeta(depth - 1, alpha, beta));
1c9f093d
BA
1387 this.undo(moves[i]);
1388 alpha = Math.max(alpha, v);
6808d7a1 1389 if (alpha >= beta) break; //beta cutoff
1c9f093d 1390 }
1c5bfdf2 1391 }
6808d7a1 1392 else {
1c5bfdf2 1393 // color=="b"
6808d7a1 1394 for (let i = 0; i < moves.length; i++) {
1c9f093d 1395 this.play(moves[i]);
6808d7a1 1396 v = Math.min(v, this.alphabeta(depth - 1, alpha, beta));
1c9f093d
BA
1397 this.undo(moves[i]);
1398 beta = Math.min(beta, v);
6808d7a1 1399 if (alpha >= beta) break; //alpha cutoff
1c9f093d
BA
1400 }
1401 }
1402 return v;
1403 }
1404
6808d7a1 1405 evalPosition() {
1c9f093d
BA
1406 let evaluation = 0;
1407 // Just count material for now
6808d7a1
BA
1408 for (let i = 0; i < V.size.x; i++) {
1409 for (let j = 0; j < V.size.y; j++) {
1410 if (this.board[i][j] != V.EMPTY) {
1411 const sign = this.getColor(i, j) == "w" ? 1 : -1;
1412 evaluation += sign * V.VALUES[this.getPiece(i, j)];
1c9f093d
BA
1413 }
1414 }
1415 }
1416 return evaluation;
1417 }
1418
1419 /////////////////////////
1420 // MOVES + GAME NOTATION
1421 /////////////////////////
1422
1423 // Context: just before move is played, turn hasn't changed
1424 // TODO: un-ambiguous notation (switch on piece type, check directions...)
6808d7a1
BA
1425 getNotation(move) {
1426 if (move.appear.length == 2 && move.appear[0].p == V.KING)
1cd3e362 1427 // Castle
6808d7a1 1428 return move.end.y < move.start.y ? "0-0-0" : "0-0";
1c9f093d
BA
1429
1430 // Translate final square
1431 const finalSquare = V.CoordsToSquare(move.end);
1432
1433 const piece = this.getPiece(move.start.x, move.start.y);
6808d7a1 1434 if (piece == V.PAWN) {
1c9f093d
BA
1435 // Pawn move
1436 let notation = "";
6808d7a1 1437 if (move.vanish.length > move.appear.length) {
1c9f093d
BA
1438 // Capture
1439 const startColumn = V.CoordToColumn(move.start.y);
1440 notation = startColumn + "x" + finalSquare;
78d64531 1441 }
6808d7a1
BA
1442 else notation = finalSquare;
1443 if (move.appear.length > 0 && move.appear[0].p != V.PAWN)
78d64531 1444 // Promotion
1c9f093d
BA
1445 notation += "=" + move.appear[0].p.toUpperCase();
1446 return notation;
1447 }
6808d7a1
BA
1448 // Piece movement
1449 return (
1450 piece.toUpperCase() +
1451 (move.vanish.length > move.appear.length ? "x" : "") +
1452 finalSquare
1453 );
1454 }
2c5d7b20
BA
1455
1456 static GetUnambiguousNotation(move) {
1457 // Machine-readable format with all the informations about the move
1458 return (
1459 (!!move.start && V.OnBoard(move.start.x, move.start.y)
1460 ? V.CoordsToSquare(move.start)
1461 : "-"
1462 ) + "." +
1463 (!!move.end && V.OnBoard(move.end.x, move.end.y)
1464 ? V.CoordsToSquare(move.end)
1465 : "-"
1466 ) + " " +
1467 (!!move.appear && move.appear.length > 0
1468 ? move.appear.map(a =>
1469 a.c + a.p + V.CoordsToSquare({ x: a.x, y: a.y })).join(".")
1470 : "-"
1471 ) + "/" +
1472 (!!move.vanish && move.vanish.length > 0
1473 ? move.vanish.map(a =>
1474 a.c + a.p + V.CoordsToSquare({ x: a.x, y: a.y })).join(".")
1475 : "-"
1476 )
1477 );
1478 }
7e8a7ea1 1479
6808d7a1 1480};