Fix some rules, complete rules translations
[vchess.git] / client / src / base_rules.js
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92342261
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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};
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29
30// NOTE: x coords = top to bottom; y = left to right (from white player perspective)
6808d7a1 31export const ChessRules = class ChessRules {
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32 //////////////
33 // MISC UTILS
34
20620465 35 // Some variants don't have flags:
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36 static get HasFlags() {
37 return true;
20620465 38 }
1c9f093d 39
20620465 40 // Some variants don't have en-passant
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41 static get HasEnpassant() {
42 return true;
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43 }
44
45 // Some variants cannot have analyse mode
8477e53d 46 static get CanAnalyze() {
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47 return true;
48 }
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49 // Patch: issues with javascript OOP, objects can't access static fields.
50 get canAnalyze() {
51 return V.CanAnalyze;
52 }
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53
54 // Some variants show incomplete information,
55 // and thus show only a partial moves list or no list at all.
56 static get ShowMoves() {
57 return "all";
58 }
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59 get showMoves() {
60 return V.ShowMoves;
61 }
1c9f093d 62
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63 // Some variants always show the same orientation
64 static get CanFlip() {
65 return true;
66 }
67 get canFlip() {
68 return V.CanFlip;
69 }
70
1c9f093d 71 // Turn "wb" into "B" (for FEN)
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72 static board2fen(b) {
73 return b[0] == "w" ? b[1].toUpperCase() : b[1];
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74 }
75
76 // Turn "p" into "bp" (for board)
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77 static fen2board(f) {
78 return f.charCodeAt() <= 90 ? "w" + f.toLowerCase() : "b" + f;
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79 }
80
89021f18 81 // Check if FEN describe a board situation correctly
6808d7a1 82 static IsGoodFen(fen) {
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83 const fenParsed = V.ParseFen(fen);
84 // 1) Check position
6808d7a1 85 if (!V.IsGoodPosition(fenParsed.position)) return false;
1c9f093d 86 // 2) Check turn
6808d7a1 87 if (!fenParsed.turn || !V.IsGoodTurn(fenParsed.turn)) return false;
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88 // 3) Check moves count
89 if (!fenParsed.movesCount || !(parseInt(fenParsed.movesCount) >= 0))
90 return false;
91 // 4) Check flags
92 if (V.HasFlags && (!fenParsed.flags || !V.IsGoodFlags(fenParsed.flags)))
93 return false;
94 // 5) Check enpassant
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95 if (
96 V.HasEnpassant &&
97 (!fenParsed.enpassant || !V.IsGoodEnpassant(fenParsed.enpassant))
98 ) {
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99 return false;
100 }
101 return true;
102 }
103
104 // Is position part of the FEN a priori correct?
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105 static IsGoodPosition(position) {
106 if (position.length == 0) return false;
1c9f093d 107 const rows = position.split("/");
6808d7a1 108 if (rows.length != V.size.x) return false;
d7c00f6a 109 let kings = {};
6808d7a1 110 for (let row of rows) {
1c9f093d 111 let sumElts = 0;
6808d7a1 112 for (let i = 0; i < row.length; i++) {
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113 if (['K','k'].includes(row[i]))
114 kings[row[i]] = true;
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115 if (V.PIECES.includes(row[i].toLowerCase())) sumElts++;
116 else {
1c9f093d 117 const num = parseInt(row[i]);
6808d7a1 118 if (isNaN(num)) return false;
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119 sumElts += num;
120 }
121 }
6808d7a1 122 if (sumElts != V.size.y) return false;
1c9f093d 123 }
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124 // Both kings should be on board:
125 if (Object.keys(kings).length != 2)
126 return false;
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127 return true;
128 }
129
130 // For FEN checking
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131 static IsGoodTurn(turn) {
132 return ["w", "b"].includes(turn);
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133 }
134
135 // For FEN checking
6808d7a1 136 static IsGoodFlags(flags) {
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137 return !!flags.match(/^[01]{4,4}$/);
138 }
139
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140 static IsGoodEnpassant(enpassant) {
141 if (enpassant != "-") {
142 const ep = V.SquareToCoords(enpassant);
143 if (isNaN(ep.x) || !V.OnBoard(ep)) return false;
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144 }
145 return true;
146 }
147
148 // 3 --> d (column number to letter)
6808d7a1 149 static CoordToColumn(colnum) {
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150 return String.fromCharCode(97 + colnum);
151 }
152
153 // d --> 3 (column letter to number)
6808d7a1 154 static ColumnToCoord(column) {
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155 return column.charCodeAt(0) - 97;
156 }
157
158 // a4 --> {x:3,y:0}
6808d7a1 159 static SquareToCoords(sq) {
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160 return {
161 // NOTE: column is always one char => max 26 columns
162 // row is counted from black side => subtraction
163 x: V.size.x - parseInt(sq.substr(1)),
164 y: sq[0].charCodeAt() - 97
165 };
166 }
167
168 // {x:0,y:4} --> e8
6808d7a1 169 static CoordsToSquare(coords) {
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170 return V.CoordToColumn(coords.y) + (V.size.x - coords.x);
171 }
172
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173 // Path to pieces
174 getPpath(b) {
175 return b; //usual pieces in pieces/ folder
176 }
177
1c9f093d 178 // Aggregates flags into one object
6808d7a1 179 aggregateFlags() {
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180 return this.castleFlags;
181 }
182
183 // Reverse operation
6808d7a1 184 disaggregateFlags(flags) {
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185 this.castleFlags = flags;
186 }
187
188 // En-passant square, if any
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189 getEpSquare(moveOrSquare) {
190 if (!moveOrSquare) return undefined;
191 if (typeof moveOrSquare === "string") {
1c9f093d 192 const square = moveOrSquare;
6808d7a1 193 if (square == "-") return undefined;
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194 return V.SquareToCoords(square);
195 }
196 // Argument is a move:
197 const move = moveOrSquare;
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198 const s = move.start,
199 e = move.end;
41cb9b94 200 // NOTE: next conditions are first for Atomic, and last for Checkered
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201 if (
202 move.appear.length > 0 &&
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203 Math.abs(s.x - e.x) == 2 &&
204 s.y == e.y &&
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205 move.appear[0].p == V.PAWN &&
206 ["w", "b"].includes(move.appear[0].c)
207 ) {
1c9f093d 208 return {
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209 x: (s.x + e.x) / 2,
210 y: s.y
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211 };
212 }
213 return undefined; //default
214 }
215
216 // Can thing on square1 take thing on square2
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217 canTake([x1, y1], [x2, y2]) {
218 return this.getColor(x1, y1) !== this.getColor(x2, y2);
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219 }
220
221 // Is (x,y) on the chessboard?
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222 static OnBoard(x, y) {
223 return x >= 0 && x < V.size.x && y >= 0 && y < V.size.y;
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224 }
225
226 // Used in interface: 'side' arg == player color
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227 canIplay(side, [x, y]) {
228 return this.turn == side && this.getColor(x, y) == side;
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229 }
230
231 // On which squares is color under check ? (for interface)
6808d7a1 232 getCheckSquares(color) {
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233 return this.isAttacked(this.kingPos[color], [V.GetOppCol(color)])
234 ? [JSON.parse(JSON.stringify(this.kingPos[color]))] //need to duplicate!
235 : [];
236 }
237
238 /////////////
239 // FEN UTILS
240
241 // Setup the initial random (assymetric) position
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242 static GenRandInitFen() {
243 let pieces = { w: new Array(8), b: new Array(8) };
1c9f093d 244 // Shuffle pieces on first and last rank
6808d7a1 245 for (let c of ["w", "b"]) {
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246 let positions = ArrayFun.range(8);
247
248 // Get random squares for bishops
656b1878 249 let randIndex = 2 * randInt(4);
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250 const bishop1Pos = positions[randIndex];
251 // The second bishop must be on a square of different color
656b1878 252 let randIndex_tmp = 2 * randInt(4) + 1;
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253 const bishop2Pos = positions[randIndex_tmp];
254 // Remove chosen squares
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255 positions.splice(Math.max(randIndex, randIndex_tmp), 1);
256 positions.splice(Math.min(randIndex, randIndex_tmp), 1);
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257
258 // Get random squares for knights
656b1878 259 randIndex = randInt(6);
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260 const knight1Pos = positions[randIndex];
261 positions.splice(randIndex, 1);
656b1878 262 randIndex = randInt(5);
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263 const knight2Pos = positions[randIndex];
264 positions.splice(randIndex, 1);
265
266 // Get random square for queen
656b1878 267 randIndex = randInt(4);
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268 const queenPos = positions[randIndex];
269 positions.splice(randIndex, 1);
270
271 // Rooks and king positions are now fixed,
272 // because of the ordering rook-king-rook
273 const rook1Pos = positions[0];
274 const kingPos = positions[1];
275 const rook2Pos = positions[2];
276
277 // Finally put the shuffled pieces in the board array
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278 pieces[c][rook1Pos] = "r";
279 pieces[c][knight1Pos] = "n";
280 pieces[c][bishop1Pos] = "b";
281 pieces[c][queenPos] = "q";
282 pieces[c][kingPos] = "k";
283 pieces[c][bishop2Pos] = "b";
284 pieces[c][knight2Pos] = "n";
285 pieces[c][rook2Pos] = "r";
1c9f093d 286 }
e3e2cc44 287 // Add turn + flags + enpassant
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288 return (
289 pieces["b"].join("") +
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290 "/pppppppp/8/8/8/8/PPPPPPPP/" +
291 pieces["w"].join("").toUpperCase() +
6808d7a1 292 " w 0 1111 -"
e3e2cc44 293 );
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294 }
295
296 // "Parse" FEN: just return untransformed string data
6808d7a1 297 static ParseFen(fen) {
1c9f093d 298 const fenParts = fen.split(" ");
6808d7a1 299 let res = {
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300 position: fenParts[0],
301 turn: fenParts[1],
6808d7a1 302 movesCount: fenParts[2]
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303 };
304 let nextIdx = 3;
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305 if (V.HasFlags) Object.assign(res, { flags: fenParts[nextIdx++] });
306 if (V.HasEnpassant) Object.assign(res, { enpassant: fenParts[nextIdx] });
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307 return res;
308 }
309
310 // Return current fen (game state)
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311 getFen() {
312 return (
313 this.getBaseFen() +
314 " " +
315 this.getTurnFen() +
316 " " +
317 this.movesCount +
318 (V.HasFlags ? " " + this.getFlagsFen() : "") +
319 (V.HasEnpassant ? " " + this.getEnpassantFen() : "")
320 );
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321 }
322
323 // Position part of the FEN string
6808d7a1 324 getBaseFen() {
1c9f093d 325 let position = "";
6808d7a1 326 for (let i = 0; i < V.size.x; i++) {
1c9f093d 327 let emptyCount = 0;
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328 for (let j = 0; j < V.size.y; j++) {
329 if (this.board[i][j] == V.EMPTY) emptyCount++;
330 else {
331 if (emptyCount > 0) {
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332 // Add empty squares in-between
333 position += emptyCount;
334 emptyCount = 0;
335 }
336 position += V.board2fen(this.board[i][j]);
337 }
338 }
6808d7a1 339 if (emptyCount > 0) {
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340 // "Flush remainder"
341 position += emptyCount;
342 }
6808d7a1 343 if (i < V.size.x - 1) position += "/"; //separate rows
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344 }
345 return position;
346 }
347
6808d7a1 348 getTurnFen() {
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349 return this.turn;
350 }
351
352 // Flags part of the FEN string
6808d7a1 353 getFlagsFen() {
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354 let flags = "";
355 // Add castling flags
6808d7a1
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356 for (let i of ["w", "b"]) {
357 for (let j = 0; j < 2; j++) flags += this.castleFlags[i][j] ? "1" : "0";
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358 }
359 return flags;
360 }
361
362 // Enpassant part of the FEN string
6808d7a1 363 getEnpassantFen() {
1c9f093d 364 const L = this.epSquares.length;
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365 if (!this.epSquares[L - 1]) return "-"; //no en-passant
366 return V.CoordsToSquare(this.epSquares[L - 1]);
1c9f093d
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367 }
368
369 // Turn position fen into double array ["wb","wp","bk",...]
6808d7a1 370 static GetBoard(position) {
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371 const rows = position.split("/");
372 let board = ArrayFun.init(V.size.x, V.size.y, "");
6808d7a1 373 for (let i = 0; i < rows.length; i++) {
1c9f093d 374 let j = 0;
6808d7a1 375 for (let indexInRow = 0; indexInRow < rows[i].length; indexInRow++) {
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376 const character = rows[i][indexInRow];
377 const num = parseInt(character);
a13cbc0f 378 // If num is a number, just shift j:
6808d7a1 379 if (!isNaN(num)) j += num;
a13cbc0f 380 // Else: something at position i,j
6808d7a1 381 else board[i][j++] = V.fen2board(character);
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382 }
383 }
384 return board;
385 }
386
387 // Extract (relevant) flags from fen
6808d7a1 388 setFlags(fenflags) {
1c9f093d 389 // white a-castle, h-castle, black a-castle, h-castle
6808d7a1 390 this.castleFlags = { w: [true, true], b: [true, true] };
6808d7a1
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391 for (let i = 0; i < 4; i++)
392 this.castleFlags[i < 2 ? "w" : "b"][i % 2] = fenflags.charAt(i) == "1";
1c9f093d
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393 }
394
395 //////////////////
396 // INITIALIZATION
397
37cdcbf3 398 // Fen string fully describes the game state
b627d118
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399 constructor(fen) {
400 if (!fen)
401 // In printDiagram() fen isn't supply because only getPpath() is used
402 // TODO: find a better solution!
403 return;
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404 const fenParsed = V.ParseFen(fen);
405 this.board = V.GetBoard(fenParsed.position);
406 this.turn = fenParsed.turn[0]; //[0] to work with MarseilleRules
407 this.movesCount = parseInt(fenParsed.movesCount);
408 this.setOtherVariables(fen);
409 }
410
411 // Scan board for kings and rooks positions
6808d7a1
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412 scanKingsRooks(fen) {
413 this.INIT_COL_KING = { w: -1, b: -1 };
414 this.INIT_COL_ROOK = { w: [-1, -1], b: [-1, -1] };
415 this.kingPos = { w: [-1, -1], b: [-1, -1] }; //squares of white and black king
1c9f093d 416 const fenRows = V.ParseFen(fen).position.split("/");
6808d7a1 417 for (let i = 0; i < fenRows.length; i++) {
1c9f093d 418 let k = 0; //column index on board
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BA
419 for (let j = 0; j < fenRows[i].length; j++) {
420 switch (fenRows[i].charAt(j)) {
421 case "k":
422 this.kingPos["b"] = [i, k];
423 this.INIT_COL_KING["b"] = k;
1c9f093d 424 break;
6808d7a1
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425 case "K":
426 this.kingPos["w"] = [i, k];
427 this.INIT_COL_KING["w"] = k;
1c9f093d 428 break;
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429 case "r":
430 if (this.INIT_COL_ROOK["b"][0] < 0) this.INIT_COL_ROOK["b"][0] = k;
431 else this.INIT_COL_ROOK["b"][1] = k;
1c9f093d 432 break;
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433 case "R":
434 if (this.INIT_COL_ROOK["w"][0] < 0) this.INIT_COL_ROOK["w"][0] = k;
435 else this.INIT_COL_ROOK["w"][1] = k;
1c9f093d 436 break;
6808d7a1 437 default: {
1c9f093d 438 const num = parseInt(fenRows[i].charAt(j));
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439 if (!isNaN(num)) k += num - 1;
440 }
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441 }
442 k++;
443 }
444 }
445 }
446
447 // Some additional variables from FEN (variant dependant)
6808d7a1 448 setOtherVariables(fen) {
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449 // Set flags and enpassant:
450 const parsedFen = V.ParseFen(fen);
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451 if (V.HasFlags) this.setFlags(parsedFen.flags);
452 if (V.HasEnpassant) {
453 const epSq =
454 parsedFen.enpassant != "-"
9bd6786b 455 ? this.getEpSquare(parsedFen.enpassant)
6808d7a1
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456 : undefined;
457 this.epSquares = [epSq];
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458 }
459 // Search for king and rooks positions:
460 this.scanKingsRooks(fen);
461 }
462
463 /////////////////////
464 // GETTERS & SETTERS
465
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466 static get size() {
467 return { x: 8, y: 8 };
1c9f093d
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468 }
469
0ba6420d 470 // Color of thing on square (i,j). 'undefined' if square is empty
6808d7a1 471 getColor(i, j) {
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472 return this.board[i][j].charAt(0);
473 }
474
475 // Piece type on square (i,j). 'undefined' if square is empty
6808d7a1 476 getPiece(i, j) {
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477 return this.board[i][j].charAt(1);
478 }
479
480 // Get opponent color
6808d7a1
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481 static GetOppCol(color) {
482 return color == "w" ? "b" : "w";
1c9f093d
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483 }
484
1c9f093d 485 // Pieces codes (for a clearer code)
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486 static get PAWN() {
487 return "p";
488 }
489 static get ROOK() {
490 return "r";
491 }
492 static get KNIGHT() {
493 return "n";
494 }
495 static get BISHOP() {
496 return "b";
497 }
498 static get QUEEN() {
499 return "q";
500 }
501 static get KING() {
502 return "k";
503 }
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504
505 // For FEN checking:
6808d7a1
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506 static get PIECES() {
507 return [V.PAWN, V.ROOK, V.KNIGHT, V.BISHOP, V.QUEEN, V.KING];
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508 }
509
510 // Empty square
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511 static get EMPTY() {
512 return "";
513 }
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514
515 // Some pieces movements
6808d7a1 516 static get steps() {
1c9f093d 517 return {
6808d7a1
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518 r: [
519 [-1, 0],
520 [1, 0],
521 [0, -1],
522 [0, 1]
523 ],
524 n: [
525 [-1, -2],
526 [-1, 2],
527 [1, -2],
528 [1, 2],
529 [-2, -1],
530 [-2, 1],
531 [2, -1],
532 [2, 1]
533 ],
534 b: [
535 [-1, -1],
536 [-1, 1],
537 [1, -1],
538 [1, 1]
539 ]
1c9f093d
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540 };
541 }
542
543 ////////////////////
544 // MOVES GENERATION
545
0ba6420d 546 // All possible moves from selected square
6808d7a1
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547 getPotentialMovesFrom([x, y]) {
548 switch (this.getPiece(x, y)) {
1c9f093d 549 case V.PAWN:
6808d7a1 550 return this.getPotentialPawnMoves([x, y]);
1c9f093d 551 case V.ROOK:
6808d7a1 552 return this.getPotentialRookMoves([x, y]);
1c9f093d 553 case V.KNIGHT:
6808d7a1 554 return this.getPotentialKnightMoves([x, y]);
1c9f093d 555 case V.BISHOP:
6808d7a1 556 return this.getPotentialBishopMoves([x, y]);
1c9f093d 557 case V.QUEEN:
6808d7a1 558 return this.getPotentialQueenMoves([x, y]);
1c9f093d 559 case V.KING:
6808d7a1 560 return this.getPotentialKingMoves([x, y]);
1c9f093d 561 }
6808d7a1 562 return []; //never reached
1c9f093d
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563 }
564
565 // Build a regular move from its initial and destination squares.
566 // tr: transformation
6808d7a1 567 getBasicMove([sx, sy], [ex, ey], tr) {
1c9f093d
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568 let mv = new Move({
569 appear: [
570 new PiPo({
571 x: ex,
572 y: ey,
6808d7a1
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573 c: tr ? tr.c : this.getColor(sx, sy),
574 p: tr ? tr.p : this.getPiece(sx, sy)
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575 })
576 ],
577 vanish: [
578 new PiPo({
579 x: sx,
580 y: sy,
6808d7a1
BA
581 c: this.getColor(sx, sy),
582 p: this.getPiece(sx, sy)
1c9f093d
BA
583 })
584 ]
585 });
586
587 // The opponent piece disappears if we take it
6808d7a1 588 if (this.board[ex][ey] != V.EMPTY) {
1c9f093d
BA
589 mv.vanish.push(
590 new PiPo({
591 x: ex,
592 y: ey,
6808d7a1
BA
593 c: this.getColor(ex, ey),
594 p: this.getPiece(ex, ey)
1c9f093d
BA
595 })
596 );
597 }
1c5bfdf2 598
1c9f093d
BA
599 return mv;
600 }
601
602 // Generic method to find possible moves of non-pawn pieces:
603 // "sliding or jumping"
6808d7a1 604 getSlideNJumpMoves([x, y], steps, oneStep) {
1c9f093d 605 let moves = [];
6808d7a1 606 outerLoop: for (let step of steps) {
1c9f093d
BA
607 let i = x + step[0];
608 let j = y + step[1];
6808d7a1
BA
609 while (V.OnBoard(i, j) && this.board[i][j] == V.EMPTY) {
610 moves.push(this.getBasicMove([x, y], [i, j]));
d1be8046 611 if (oneStep) continue outerLoop;
1c9f093d
BA
612 i += step[0];
613 j += step[1];
614 }
6808d7a1
BA
615 if (V.OnBoard(i, j) && this.canTake([x, y], [i, j]))
616 moves.push(this.getBasicMove([x, y], [i, j]));
1c9f093d
BA
617 }
618 return moves;
619 }
620
621 // What are the pawn moves from square x,y ?
6808d7a1 622 getPotentialPawnMoves([x, y]) {
1c9f093d
BA
623 const color = this.turn;
624 let moves = [];
6808d7a1
BA
625 const [sizeX, sizeY] = [V.size.x, V.size.y];
626 const shiftX = color == "w" ? -1 : 1;
627 const firstRank = color == "w" ? sizeX - 1 : 0;
628 const startRank = color == "w" ? sizeX - 2 : 1;
629 const lastRank = color == "w" ? 0 : sizeX - 1;
630 const pawnColor = this.getColor(x, y); //can be different for checkered
1c9f093d
BA
631
632 // NOTE: next condition is generally true (no pawn on last rank)
6808d7a1
BA
633 if (x + shiftX >= 0 && x + shiftX < sizeX) {
634 const finalPieces =
635 x + shiftX == lastRank
636 ? [V.ROOK, V.KNIGHT, V.BISHOP, V.QUEEN]
637 : [V.PAWN];
6808d7a1 638 if (this.board[x + shiftX][y] == V.EMPTY) {
71ef1664 639 // One square forward
6808d7a1
BA
640 for (let piece of finalPieces) {
641 moves.push(
642 this.getBasicMove([x, y], [x + shiftX, y], {
643 c: pawnColor,
644 p: piece
645 })
646 );
1c9f093d
BA
647 }
648 // Next condition because pawns on 1st rank can generally jump
6808d7a1
BA
649 if (
650 [startRank, firstRank].includes(x) &&
651 this.board[x + 2 * shiftX][y] == V.EMPTY
652 ) {
1c9f093d 653 // Two squares jump
6808d7a1 654 moves.push(this.getBasicMove([x, y], [x + 2 * shiftX, y]));
1c9f093d
BA
655 }
656 }
657 // Captures
6808d7a1
BA
658 for (let shiftY of [-1, 1]) {
659 if (
660 y + shiftY >= 0 &&
661 y + shiftY < sizeY &&
662 this.board[x + shiftX][y + shiftY] != V.EMPTY &&
663 this.canTake([x, y], [x + shiftX, y + shiftY])
664 ) {
665 for (let piece of finalPieces) {
666 moves.push(
667 this.getBasicMove([x, y], [x + shiftX, y + shiftY], {
668 c: pawnColor,
669 p: piece
670 })
671 );
1c9f093d
BA
672 }
673 }
674 }
675 }
676
6808d7a1 677 if (V.HasEnpassant) {
1c9f093d
BA
678 // En passant
679 const Lep = this.epSquares.length;
6808d7a1
BA
680 const epSquare = this.epSquares[Lep - 1]; //always at least one element
681 if (
682 !!epSquare &&
683 epSquare.x == x + shiftX &&
684 Math.abs(epSquare.y - y) == 1
685 ) {
686 let enpassantMove = this.getBasicMove([x, y], [epSquare.x, epSquare.y]);
1c9f093d
BA
687 enpassantMove.vanish.push({
688 x: x,
689 y: epSquare.y,
6808d7a1
BA
690 p: "p",
691 c: this.getColor(x, epSquare.y)
1c9f093d
BA
692 });
693 moves.push(enpassantMove);
694 }
695 }
696
697 return moves;
698 }
699
700 // What are the rook moves from square x,y ?
6808d7a1 701 getPotentialRookMoves(sq) {
1c9f093d
BA
702 return this.getSlideNJumpMoves(sq, V.steps[V.ROOK]);
703 }
704
705 // What are the knight moves from square x,y ?
6808d7a1 706 getPotentialKnightMoves(sq) {
1c9f093d
BA
707 return this.getSlideNJumpMoves(sq, V.steps[V.KNIGHT], "oneStep");
708 }
709
710 // What are the bishop moves from square x,y ?
6808d7a1 711 getPotentialBishopMoves(sq) {
1c9f093d
BA
712 return this.getSlideNJumpMoves(sq, V.steps[V.BISHOP]);
713 }
714
715 // What are the queen moves from square x,y ?
6808d7a1
BA
716 getPotentialQueenMoves(sq) {
717 return this.getSlideNJumpMoves(
718 sq,
719 V.steps[V.ROOK].concat(V.steps[V.BISHOP])
720 );
1c9f093d
BA
721 }
722
723 // What are the king moves from square x,y ?
6808d7a1 724 getPotentialKingMoves(sq) {
1c9f093d 725 // Initialize with normal moves
6808d7a1
BA
726 let moves = this.getSlideNJumpMoves(
727 sq,
728 V.steps[V.ROOK].concat(V.steps[V.BISHOP]),
729 "oneStep"
730 );
1c9f093d
BA
731 return moves.concat(this.getCastleMoves(sq));
732 }
733
6808d7a1
BA
734 getCastleMoves([x, y]) {
735 const c = this.getColor(x, y);
736 if (x != (c == "w" ? V.size.x - 1 : 0) || y != this.INIT_COL_KING[c])
1c9f093d
BA
737 return []; //x isn't first rank, or king has moved (shortcut)
738
739 // Castling ?
740 const oppCol = V.GetOppCol(c);
741 let moves = [];
742 let i = 0;
9bd6786b 743 // King, then rook:
6808d7a1
BA
744 const finalSquares = [
745 [2, 3],
746 [V.size.y - 2, V.size.y - 3]
9bd6786b 747 ];
6808d7a1
BA
748 castlingCheck: for (
749 let castleSide = 0;
750 castleSide < 2;
751 castleSide++ //large, then small
752 ) {
753 if (!this.castleFlags[c][castleSide]) continue;
1c9f093d
BA
754 // If this code is reached, rooks and king are on initial position
755
2beba6db
BA
756 // Nothing on the path of the king ? (and no checks)
757 const finDist = finalSquares[castleSide][0] - y;
758 let step = finDist / Math.max(1, Math.abs(finDist));
759 i = y;
6808d7a1
BA
760 do {
761 if (
762 this.isAttacked([x, i], [oppCol]) ||
763 (this.board[x][i] != V.EMPTY &&
764 // NOTE: next check is enough, because of chessboard constraints
765 (this.getColor(x, i) != c ||
766 ![V.KING, V.ROOK].includes(this.getPiece(x, i))))
767 ) {
1c9f093d
BA
768 continue castlingCheck;
769 }
2beba6db 770 i += step;
6808d7a1 771 } while (i != finalSquares[castleSide][0]);
1c9f093d
BA
772
773 // Nothing on the path to the rook?
6808d7a1
BA
774 step = castleSide == 0 ? -1 : 1;
775 for (i = y + step; i != this.INIT_COL_ROOK[c][castleSide]; i += step) {
776 if (this.board[x][i] != V.EMPTY) continue castlingCheck;
1c9f093d
BA
777 }
778 const rookPos = this.INIT_COL_ROOK[c][castleSide];
779
780 // Nothing on final squares, except maybe king and castling rook?
6808d7a1
BA
781 for (i = 0; i < 2; i++) {
782 if (
783 this.board[x][finalSquares[castleSide][i]] != V.EMPTY &&
784 this.getPiece(x, finalSquares[castleSide][i]) != V.KING &&
785 finalSquares[castleSide][i] != rookPos
786 ) {
1c9f093d
BA
787 continue castlingCheck;
788 }
789 }
790
791 // If this code is reached, castle is valid
6808d7a1
BA
792 moves.push(
793 new Move({
794 appear: [
795 new PiPo({ x: x, y: finalSquares[castleSide][0], p: V.KING, c: c }),
796 new PiPo({ x: x, y: finalSquares[castleSide][1], p: V.ROOK, c: c })
797 ],
798 vanish: [
799 new PiPo({ x: x, y: y, p: V.KING, c: c }),
800 new PiPo({ x: x, y: rookPos, p: V.ROOK, c: c })
801 ],
802 end:
803 Math.abs(y - rookPos) <= 2
804 ? { x: x, y: rookPos }
805 : { x: x, y: y + 2 * (castleSide == 0 ? -1 : 1) }
806 })
807 );
1c9f093d
BA
808 }
809
810 return moves;
811 }
812
813 ////////////////////
814 // MOVES VALIDATION
815
816 // For the interface: possible moves for the current turn from square sq
6808d7a1
BA
817 getPossibleMovesFrom(sq) {
818 return this.filterValid(this.getPotentialMovesFrom(sq));
1c9f093d
BA
819 }
820
821 // TODO: promotions (into R,B,N,Q) should be filtered only once
6808d7a1
BA
822 filterValid(moves) {
823 if (moves.length == 0) return [];
1c9f093d
BA
824 const color = this.turn;
825 return moves.filter(m => {
826 this.play(m);
827 const res = !this.underCheck(color);
828 this.undo(m);
829 return res;
830 });
831 }
832
833 // Search for all valid moves considering current turn
834 // (for engine and game end)
6808d7a1 835 getAllValidMoves() {
1c9f093d 836 const color = this.turn;
1c9f093d 837 let potentialMoves = [];
6808d7a1
BA
838 for (let i = 0; i < V.size.x; i++) {
839 for (let j = 0; j < V.size.y; j++) {
d1be8046 840 if (this.getColor(i, j) == color) {
6808d7a1
BA
841 Array.prototype.push.apply(
842 potentialMoves,
843 this.getPotentialMovesFrom([i, j])
844 );
1c9f093d
BA
845 }
846 }
847 }
848 return this.filterValid(potentialMoves);
849 }
850
851 // Stop at the first move found
6808d7a1 852 atLeastOneMove() {
1c9f093d 853 const color = this.turn;
6808d7a1
BA
854 for (let i = 0; i < V.size.x; i++) {
855 for (let j = 0; j < V.size.y; j++) {
d1be8046 856 if (this.getColor(i, j) == color) {
6808d7a1
BA
857 const moves = this.getPotentialMovesFrom([i, j]);
858 if (moves.length > 0) {
859 for (let k = 0; k < moves.length; k++) {
860 if (this.filterValid([moves[k]]).length > 0) return true;
1c9f093d
BA
861 }
862 }
863 }
864 }
865 }
866 return false;
867 }
868
869 // Check if pieces of color in 'colors' are attacking (king) on square x,y
6808d7a1
BA
870 isAttacked(sq, colors) {
871 return (
872 this.isAttackedByPawn(sq, colors) ||
873 this.isAttackedByRook(sq, colors) ||
874 this.isAttackedByKnight(sq, colors) ||
875 this.isAttackedByBishop(sq, colors) ||
876 this.isAttackedByQueen(sq, colors) ||
877 this.isAttackedByKing(sq, colors)
878 );
1c9f093d
BA
879 }
880
d1be8046
BA
881 // Generic method for non-pawn pieces ("sliding or jumping"):
882 // is x,y attacked by a piece of color in array 'colors' ?
883 isAttackedBySlideNJump([x, y], colors, piece, steps, oneStep) {
884 for (let step of steps) {
885 let rx = x + step[0],
886 ry = y + step[1];
887 while (V.OnBoard(rx, ry) && this.board[rx][ry] == V.EMPTY && !oneStep) {
888 rx += step[0];
889 ry += step[1];
890 }
891 if (
892 V.OnBoard(rx, ry) &&
893 this.getPiece(rx, ry) === piece &&
894 colors.includes(this.getColor(rx, ry))
895 ) {
896 return true;
897 }
898 }
899 return false;
900 }
901
1c9f093d 902 // Is square x,y attacked by 'colors' pawns ?
6808d7a1
BA
903 isAttackedByPawn([x, y], colors) {
904 for (let c of colors) {
d1be8046 905 const pawnShift = c == "w" ? 1 : -1;
6808d7a1
BA
906 if (x + pawnShift >= 0 && x + pawnShift < V.size.x) {
907 for (let i of [-1, 1]) {
908 if (
909 y + i >= 0 &&
910 y + i < V.size.y &&
911 this.getPiece(x + pawnShift, y + i) == V.PAWN &&
912 this.getColor(x + pawnShift, y + i) == c
913 ) {
1c9f093d
BA
914 return true;
915 }
916 }
917 }
918 }
919 return false;
920 }
921
922 // Is square x,y attacked by 'colors' rooks ?
6808d7a1 923 isAttackedByRook(sq, colors) {
1c9f093d
BA
924 return this.isAttackedBySlideNJump(sq, colors, V.ROOK, V.steps[V.ROOK]);
925 }
926
927 // Is square x,y attacked by 'colors' knights ?
6808d7a1
BA
928 isAttackedByKnight(sq, colors) {
929 return this.isAttackedBySlideNJump(
930 sq,
931 colors,
932 V.KNIGHT,
933 V.steps[V.KNIGHT],
934 "oneStep"
935 );
1c9f093d
BA
936 }
937
938 // Is square x,y attacked by 'colors' bishops ?
6808d7a1 939 isAttackedByBishop(sq, colors) {
1c9f093d
BA
940 return this.isAttackedBySlideNJump(sq, colors, V.BISHOP, V.steps[V.BISHOP]);
941 }
942
943 // Is square x,y attacked by 'colors' queens ?
6808d7a1
BA
944 isAttackedByQueen(sq, colors) {
945 return this.isAttackedBySlideNJump(
946 sq,
947 colors,
948 V.QUEEN,
949 V.steps[V.ROOK].concat(V.steps[V.BISHOP])
950 );
1c9f093d
BA
951 }
952
953 // Is square x,y attacked by 'colors' king(s) ?
6808d7a1
BA
954 isAttackedByKing(sq, colors) {
955 return this.isAttackedBySlideNJump(
956 sq,
957 colors,
958 V.KING,
959 V.steps[V.ROOK].concat(V.steps[V.BISHOP]),
960 "oneStep"
961 );
1c9f093d
BA
962 }
963
1c9f093d 964 // Is color under check after his move ?
6808d7a1 965 underCheck(color) {
1c9f093d
BA
966 return this.isAttacked(this.kingPos[color], [V.GetOppCol(color)]);
967 }
968
969 /////////////////
970 // MOVES PLAYING
971
972 // Apply a move on board
6808d7a1
BA
973 static PlayOnBoard(board, move) {
974 for (let psq of move.vanish) board[psq.x][psq.y] = V.EMPTY;
975 for (let psq of move.appear) board[psq.x][psq.y] = psq.c + psq.p;
1c9f093d
BA
976 }
977 // Un-apply the played move
6808d7a1
BA
978 static UndoOnBoard(board, move) {
979 for (let psq of move.appear) board[psq.x][psq.y] = V.EMPTY;
980 for (let psq of move.vanish) board[psq.x][psq.y] = psq.c + psq.p;
1c9f093d
BA
981 }
982
983 // After move is played, update variables + flags
6808d7a1 984 updateVariables(move) {
1c9f093d 985 let piece = undefined;
78d64531
BA
986 // TODO: update variables before move is played, and just use this.turn ?
987 // (doesn't work in general, think MarseilleChess)
1c9f093d 988 let c = undefined;
6808d7a1 989 if (move.vanish.length >= 1) {
1c9f093d
BA
990 // Usual case, something is moved
991 piece = move.vanish[0].p;
992 c = move.vanish[0].c;
6808d7a1 993 } else {
1c9f093d
BA
994 // Crazyhouse-like variants
995 piece = move.appear[0].p;
996 c = move.appear[0].c;
997 }
78d64531
BA
998 if (!['w','b'].includes(c)) {
999 // Checkered, for example
1c9f093d
BA
1000 c = V.GetOppCol(this.turn);
1001 }
6808d7a1 1002 const firstRank = c == "w" ? V.size.x - 1 : 0;
1c9f093d
BA
1003
1004 // Update king position + flags
6808d7a1 1005 if (piece == V.KING && move.appear.length > 0) {
1c9f093d
BA
1006 this.kingPos[c][0] = move.appear[0].x;
1007 this.kingPos[c][1] = move.appear[0].y;
6808d7a1 1008 if (V.HasFlags) this.castleFlags[c] = [false, false];
1c9f093d
BA
1009 return;
1010 }
6808d7a1 1011 if (V.HasFlags) {
1c9f093d
BA
1012 // Update castling flags if rooks are moved
1013 const oppCol = V.GetOppCol(c);
6808d7a1
BA
1014 const oppFirstRank = V.size.x - 1 - firstRank;
1015 if (
1016 move.start.x == firstRank && //our rook moves?
1017 this.INIT_COL_ROOK[c].includes(move.start.y)
1018 ) {
1019 const flagIdx = move.start.y == this.INIT_COL_ROOK[c][0] ? 0 : 1;
1c9f093d 1020 this.castleFlags[c][flagIdx] = false;
6808d7a1
BA
1021 } else if (
1022 move.end.x == oppFirstRank && //we took opponent rook?
1023 this.INIT_COL_ROOK[oppCol].includes(move.end.y)
1024 ) {
1025 const flagIdx = move.end.y == this.INIT_COL_ROOK[oppCol][0] ? 0 : 1;
1c9f093d
BA
1026 this.castleFlags[oppCol][flagIdx] = false;
1027 }
1028 }
1029 }
1030
1031 // After move is undo-ed *and flags resetted*, un-update other variables
1032 // TODO: more symmetry, by storing flags increment in move (?!)
6808d7a1 1033 unupdateVariables(move) {
1c9f093d 1034 // (Potentially) Reset king position
6808d7a1
BA
1035 const c = this.getColor(move.start.x, move.start.y);
1036 if (this.getPiece(move.start.x, move.start.y) == V.KING)
1c9f093d
BA
1037 this.kingPos[c] = [move.start.x, move.start.y];
1038 }
1039
6808d7a1 1040 play(move) {
1c9f093d 1041 // DEBUG:
9bd6786b
BA
1042// if (!this.states) this.states = [];
1043// const stateFen = this.getBaseFen() + this.getTurnFen() + this.getFlagsFen();
1044// this.states.push(stateFen);
6808d7a1
BA
1045
1046 if (V.HasFlags) move.flags = JSON.stringify(this.aggregateFlags()); //save flags (for undo)
1047 if (V.HasEnpassant) this.epSquares.push(this.getEpSquare(move));
1c9f093d
BA
1048 V.PlayOnBoard(this.board, move);
1049 this.turn = V.GetOppCol(this.turn);
1050 this.movesCount++;
1051 this.updateVariables(move);
1052 }
1053
6808d7a1
BA
1054 undo(move) {
1055 if (V.HasEnpassant) this.epSquares.pop();
1056 if (V.HasFlags) this.disaggregateFlags(JSON.parse(move.flags));
1c9f093d
BA
1057 V.UndoOnBoard(this.board, move);
1058 this.turn = V.GetOppCol(this.turn);
1059 this.movesCount--;
1060 this.unupdateVariables(move);
1061
1062 // DEBUG:
9bd6786b
BA
1063// const stateFen = this.getBaseFen() + this.getTurnFen() + this.getFlagsFen();
1064// if (stateFen != this.states[this.states.length-1]) debugger;
1065// this.states.pop();
1c9f093d
BA
1066 }
1067
1068 ///////////////
1069 // END OF GAME
1070
1071 // What is the score ? (Interesting if game is over)
6808d7a1
BA
1072 getCurrentScore() {
1073 if (this.atLeastOneMove())
1c9f093d
BA
1074 return "*";
1075
1076 // Game over
1077 const color = this.turn;
1078 // No valid move: stalemate or checkmate?
1079 if (!this.isAttacked(this.kingPos[color], [V.GetOppCol(color)]))
1080 return "1/2";
1081 // OK, checkmate
6808d7a1 1082 return color == "w" ? "0-1" : "1-0";
1c9f093d
BA
1083 }
1084
1085 ///////////////
1086 // ENGINE PLAY
1087
1088 // Pieces values
6808d7a1 1089 static get VALUES() {
1c9f093d 1090 return {
6808d7a1
BA
1091 p: 1,
1092 r: 5,
1093 n: 3,
1094 b: 3,
1095 q: 9,
1096 k: 1000
1c9f093d
BA
1097 };
1098 }
1099
1100 // "Checkmate" (unreachable eval)
6808d7a1
BA
1101 static get INFINITY() {
1102 return 9999;
1103 }
1c9f093d
BA
1104
1105 // At this value or above, the game is over
6808d7a1
BA
1106 static get THRESHOLD_MATE() {
1107 return V.INFINITY;
1108 }
1c9f093d
BA
1109
1110 // Search depth: 2 for high branching factor, 4 for small (Loser chess, eg.)
6808d7a1
BA
1111 static get SEARCH_DEPTH() {
1112 return 3;
1113 }
1c9f093d 1114
6808d7a1 1115 getComputerMove() {
1c9f093d
BA
1116 const maxeval = V.INFINITY;
1117 const color = this.turn;
1118 // Some variants may show a bigger moves list to the human (Switching),
1119 // thus the argument "computer" below (which is generally ignored)
a97bdbda 1120 let moves1 = this.getAllValidMoves();
c322a844 1121
6808d7a1 1122 if (moves1.length == 0)
e71161fb 1123 // TODO: this situation should not happen
41cb9b94 1124 return null;
1c9f093d 1125
1c9f093d 1126 // Rank moves using a min-max at depth 2
6808d7a1 1127 for (let i = 0; i < moves1.length; i++) {
1c9f093d 1128 // Initial self evaluation is very low: "I'm checkmated"
6808d7a1 1129 moves1[i].eval = (color == "w" ? -1 : 1) * maxeval;
1c9f093d
BA
1130 this.play(moves1[i]);
1131 const score1 = this.getCurrentScore();
1132 let eval2 = undefined;
6808d7a1 1133 if (score1 == "*") {
1c9f093d 1134 // Initial enemy evaluation is very low too, for him
6808d7a1 1135 eval2 = (color == "w" ? 1 : -1) * maxeval;
1c9f093d 1136 // Second half-move:
a97bdbda 1137 let moves2 = this.getAllValidMoves();
6808d7a1 1138 for (let j = 0; j < moves2.length; j++) {
1c9f093d
BA
1139 this.play(moves2[j]);
1140 const score2 = this.getCurrentScore();
6808d7a1
BA
1141 let evalPos = 0; //1/2 value
1142 switch (score2) {
1143 case "*":
1144 evalPos = this.evalPosition();
1145 break;
1146 case "1-0":
1147 evalPos = maxeval;
1148 break;
1149 case "0-1":
1150 evalPos = -maxeval;
1151 break;
1152 }
1153 if (
1154 (color == "w" && evalPos < eval2) ||
1155 (color == "b" && evalPos > eval2)
1156 ) {
1c9f093d
BA
1157 eval2 = evalPos;
1158 }
1159 this.undo(moves2[j]);
1160 }
6808d7a1
BA
1161 } else eval2 = score1 == "1/2" ? 0 : (score1 == "1-0" ? 1 : -1) * maxeval;
1162 if (
1163 (color == "w" && eval2 > moves1[i].eval) ||
1164 (color == "b" && eval2 < moves1[i].eval)
1165 ) {
1c9f093d
BA
1166 moves1[i].eval = eval2;
1167 }
1168 this.undo(moves1[i]);
1169 }
6808d7a1
BA
1170 moves1.sort((a, b) => {
1171 return (color == "w" ? 1 : -1) * (b.eval - a.eval);
1172 });
a97bdbda 1173// console.log(moves1.map(m => { return [this.getNotation(m), m.eval]; }));
1c9f093d
BA
1174
1175 let candidates = [0]; //indices of candidates moves
6808d7a1 1176 for (let j = 1; j < moves1.length && moves1[j].eval == moves1[0].eval; j++)
1c9f093d 1177 candidates.push(j);
0c3fe8a6 1178 let currentBest = moves1[candidates[randInt(candidates.length)]];
1c9f093d 1179
1c9f093d 1180 // Skip depth 3+ if we found a checkmate (or if we are checkmated in 1...)
6808d7a1 1181 if (V.SEARCH_DEPTH >= 3 && Math.abs(moves1[0].eval) < V.THRESHOLD_MATE) {
656b1878
BA
1182 // From here, depth >= 3: may take a while, so we control time
1183 const timeStart = Date.now();
6808d7a1
BA
1184 for (let i = 0; i < moves1.length; i++) {
1185 if (Date.now() - timeStart >= 5000)
1186 //more than 5 seconds
1c9f093d
BA
1187 return currentBest; //depth 2 at least
1188 this.play(moves1[i]);
1189 // 0.1 * oldEval : heuristic to avoid some bad moves (not all...)
6808d7a1
BA
1190 moves1[i].eval =
1191 0.1 * moves1[i].eval +
1192 this.alphabeta(V.SEARCH_DEPTH - 1, -maxeval, maxeval);
1c9f093d
BA
1193 this.undo(moves1[i]);
1194 }
6808d7a1
BA
1195 moves1.sort((a, b) => {
1196 return (color == "w" ? 1 : -1) * (b.eval - a.eval);
1197 });
1198 } else return currentBest;
1c5bfdf2 1199// console.log(moves1.map(m => { return [this.getNotation(m), m.eval]; }));
1c9f093d
BA
1200
1201 candidates = [0];
6808d7a1 1202 for (let j = 1; j < moves1.length && moves1[j].eval == moves1[0].eval; j++)
1c9f093d 1203 candidates.push(j);
656b1878 1204 return moves1[candidates[randInt(candidates.length)]];
1c9f093d
BA
1205 }
1206
6808d7a1 1207 alphabeta(depth, alpha, beta) {
1c9f093d
BA
1208 const maxeval = V.INFINITY;
1209 const color = this.turn;
1210 const score = this.getCurrentScore();
1211 if (score != "*")
6808d7a1
BA
1212 return score == "1/2" ? 0 : (score == "1-0" ? 1 : -1) * maxeval;
1213 if (depth == 0) return this.evalPosition();
a97bdbda 1214 const moves = this.getAllValidMoves();
6808d7a1
BA
1215 let v = color == "w" ? -maxeval : maxeval;
1216 if (color == "w") {
1217 for (let i = 0; i < moves.length; i++) {
1c9f093d 1218 this.play(moves[i]);
6808d7a1 1219 v = Math.max(v, this.alphabeta(depth - 1, alpha, beta));
1c9f093d
BA
1220 this.undo(moves[i]);
1221 alpha = Math.max(alpha, v);
6808d7a1 1222 if (alpha >= beta) break; //beta cutoff
1c9f093d 1223 }
1c5bfdf2 1224 }
6808d7a1 1225 else {
1c5bfdf2 1226 // color=="b"
6808d7a1 1227 for (let i = 0; i < moves.length; i++) {
1c9f093d 1228 this.play(moves[i]);
6808d7a1 1229 v = Math.min(v, this.alphabeta(depth - 1, alpha, beta));
1c9f093d
BA
1230 this.undo(moves[i]);
1231 beta = Math.min(beta, v);
6808d7a1 1232 if (alpha >= beta) break; //alpha cutoff
1c9f093d
BA
1233 }
1234 }
1235 return v;
1236 }
1237
6808d7a1 1238 evalPosition() {
1c9f093d
BA
1239 let evaluation = 0;
1240 // Just count material for now
6808d7a1
BA
1241 for (let i = 0; i < V.size.x; i++) {
1242 for (let j = 0; j < V.size.y; j++) {
1243 if (this.board[i][j] != V.EMPTY) {
1244 const sign = this.getColor(i, j) == "w" ? 1 : -1;
1245 evaluation += sign * V.VALUES[this.getPiece(i, j)];
1c9f093d
BA
1246 }
1247 }
1248 }
1249 return evaluation;
1250 }
1251
1252 /////////////////////////
1253 // MOVES + GAME NOTATION
1254 /////////////////////////
1255
1256 // Context: just before move is played, turn hasn't changed
1257 // TODO: un-ambiguous notation (switch on piece type, check directions...)
6808d7a1
BA
1258 getNotation(move) {
1259 if (move.appear.length == 2 && move.appear[0].p == V.KING)
1cd3e362 1260 // Castle
6808d7a1 1261 return move.end.y < move.start.y ? "0-0-0" : "0-0";
1c9f093d
BA
1262
1263 // Translate final square
1264 const finalSquare = V.CoordsToSquare(move.end);
1265
1266 const piece = this.getPiece(move.start.x, move.start.y);
6808d7a1 1267 if (piece == V.PAWN) {
1c9f093d
BA
1268 // Pawn move
1269 let notation = "";
6808d7a1 1270 if (move.vanish.length > move.appear.length) {
1c9f093d
BA
1271 // Capture
1272 const startColumn = V.CoordToColumn(move.start.y);
1273 notation = startColumn + "x" + finalSquare;
78d64531 1274 }
6808d7a1
BA
1275 else notation = finalSquare;
1276 if (move.appear.length > 0 && move.appear[0].p != V.PAWN)
78d64531 1277 // Promotion
1c9f093d
BA
1278 notation += "=" + move.appear[0].p.toUpperCase();
1279 return notation;
1280 }
6808d7a1
BA
1281 // Piece movement
1282 return (
1283 piece.toUpperCase() +
1284 (move.vanish.length > move.appear.length ? "x" : "") +
1285 finalSquare
1286 );
1287 }
1288};