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