Draft Hiddenqueen, Grasshopper and Knightmate chess (rules unwritten)
[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]);
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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";
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393 }
394
395 //////////////////
396 // INITIALIZATION
397
6808d7a1 398 constructor(fen) {
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399 // In printDiagram() fen isn't supply because only getPpath() is used
400 if (fen)
401 this.re_init(fen);
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402 }
403
404 // Fen string fully describes the game state
6808d7a1 405 re_init(fen) {
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406 const fenParsed = V.ParseFen(fen);
407 this.board = V.GetBoard(fenParsed.position);
408 this.turn = fenParsed.turn[0]; //[0] to work with MarseilleRules
409 this.movesCount = parseInt(fenParsed.movesCount);
410 this.setOtherVariables(fen);
411 }
412
413 // Scan board for kings and rooks positions
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414 scanKingsRooks(fen) {
415 this.INIT_COL_KING = { w: -1, b: -1 };
416 this.INIT_COL_ROOK = { w: [-1, -1], b: [-1, -1] };
417 this.kingPos = { w: [-1, -1], b: [-1, -1] }; //squares of white and black king
1c9f093d 418 const fenRows = V.ParseFen(fen).position.split("/");
6808d7a1 419 for (let i = 0; i < fenRows.length; i++) {
1c9f093d 420 let k = 0; //column index on board
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421 for (let j = 0; j < fenRows[i].length; j++) {
422 switch (fenRows[i].charAt(j)) {
423 case "k":
424 this.kingPos["b"] = [i, k];
425 this.INIT_COL_KING["b"] = k;
1c9f093d 426 break;
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427 case "K":
428 this.kingPos["w"] = [i, k];
429 this.INIT_COL_KING["w"] = k;
1c9f093d 430 break;
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431 case "r":
432 if (this.INIT_COL_ROOK["b"][0] < 0) this.INIT_COL_ROOK["b"][0] = k;
433 else this.INIT_COL_ROOK["b"][1] = k;
1c9f093d 434 break;
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435 case "R":
436 if (this.INIT_COL_ROOK["w"][0] < 0) this.INIT_COL_ROOK["w"][0] = k;
437 else this.INIT_COL_ROOK["w"][1] = k;
1c9f093d 438 break;
6808d7a1 439 default: {
1c9f093d 440 const num = parseInt(fenRows[i].charAt(j));
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441 if (!isNaN(num)) k += num - 1;
442 }
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443 }
444 k++;
445 }
446 }
447 }
448
449 // Some additional variables from FEN (variant dependant)
6808d7a1 450 setOtherVariables(fen) {
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451 // Set flags and enpassant:
452 const parsedFen = V.ParseFen(fen);
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453 if (V.HasFlags) this.setFlags(parsedFen.flags);
454 if (V.HasEnpassant) {
455 const epSq =
456 parsedFen.enpassant != "-"
9bd6786b 457 ? this.getEpSquare(parsedFen.enpassant)
6808d7a1
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458 : undefined;
459 this.epSquares = [epSq];
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460 }
461 // Search for king and rooks positions:
462 this.scanKingsRooks(fen);
463 }
464
465 /////////////////////
466 // GETTERS & SETTERS
467
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468 static get size() {
469 return { x: 8, y: 8 };
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470 }
471
0ba6420d 472 // Color of thing on square (i,j). 'undefined' if square is empty
6808d7a1 473 getColor(i, j) {
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474 return this.board[i][j].charAt(0);
475 }
476
477 // Piece type on square (i,j). 'undefined' if square is empty
6808d7a1 478 getPiece(i, j) {
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479 return this.board[i][j].charAt(1);
480 }
481
482 // Get opponent color
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483 static GetOppCol(color) {
484 return color == "w" ? "b" : "w";
1c9f093d
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485 }
486
1c9f093d 487 // Pieces codes (for a clearer code)
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488 static get PAWN() {
489 return "p";
490 }
491 static get ROOK() {
492 return "r";
493 }
494 static get KNIGHT() {
495 return "n";
496 }
497 static get BISHOP() {
498 return "b";
499 }
500 static get QUEEN() {
501 return "q";
502 }
503 static get KING() {
504 return "k";
505 }
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506
507 // For FEN checking:
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508 static get PIECES() {
509 return [V.PAWN, V.ROOK, V.KNIGHT, V.BISHOP, V.QUEEN, V.KING];
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510 }
511
512 // Empty square
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513 static get EMPTY() {
514 return "";
515 }
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516
517 // Some pieces movements
6808d7a1 518 static get steps() {
1c9f093d 519 return {
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520 r: [
521 [-1, 0],
522 [1, 0],
523 [0, -1],
524 [0, 1]
525 ],
526 n: [
527 [-1, -2],
528 [-1, 2],
529 [1, -2],
530 [1, 2],
531 [-2, -1],
532 [-2, 1],
533 [2, -1],
534 [2, 1]
535 ],
536 b: [
537 [-1, -1],
538 [-1, 1],
539 [1, -1],
540 [1, 1]
541 ]
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542 };
543 }
544
545 ////////////////////
546 // MOVES GENERATION
547
0ba6420d 548 // All possible moves from selected square
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549 getPotentialMovesFrom([x, y]) {
550 switch (this.getPiece(x, y)) {
1c9f093d 551 case V.PAWN:
6808d7a1 552 return this.getPotentialPawnMoves([x, y]);
1c9f093d 553 case V.ROOK:
6808d7a1 554 return this.getPotentialRookMoves([x, y]);
1c9f093d 555 case V.KNIGHT:
6808d7a1 556 return this.getPotentialKnightMoves([x, y]);
1c9f093d 557 case V.BISHOP:
6808d7a1 558 return this.getPotentialBishopMoves([x, y]);
1c9f093d 559 case V.QUEEN:
6808d7a1 560 return this.getPotentialQueenMoves([x, y]);
1c9f093d 561 case V.KING:
6808d7a1 562 return this.getPotentialKingMoves([x, y]);
1c9f093d 563 }
6808d7a1 564 return []; //never reached
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565 }
566
567 // Build a regular move from its initial and destination squares.
568 // tr: transformation
6808d7a1 569 getBasicMove([sx, sy], [ex, ey], tr) {
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570 let mv = new Move({
571 appear: [
572 new PiPo({
573 x: ex,
574 y: ey,
6808d7a1
BA
575 c: tr ? tr.c : this.getColor(sx, sy),
576 p: tr ? tr.p : this.getPiece(sx, sy)
1c9f093d
BA
577 })
578 ],
579 vanish: [
580 new PiPo({
581 x: sx,
582 y: sy,
6808d7a1
BA
583 c: this.getColor(sx, sy),
584 p: this.getPiece(sx, sy)
1c9f093d
BA
585 })
586 ]
587 });
588
589 // The opponent piece disappears if we take it
6808d7a1 590 if (this.board[ex][ey] != V.EMPTY) {
1c9f093d
BA
591 mv.vanish.push(
592 new PiPo({
593 x: ex,
594 y: ey,
6808d7a1
BA
595 c: this.getColor(ex, ey),
596 p: this.getPiece(ex, ey)
1c9f093d
BA
597 })
598 );
599 }
1c5bfdf2 600
1c9f093d
BA
601 return mv;
602 }
603
604 // Generic method to find possible moves of non-pawn pieces:
605 // "sliding or jumping"
6808d7a1 606 getSlideNJumpMoves([x, y], steps, oneStep) {
1c9f093d 607 let moves = [];
6808d7a1 608 outerLoop: for (let step of steps) {
1c9f093d
BA
609 let i = x + step[0];
610 let j = y + step[1];
6808d7a1
BA
611 while (V.OnBoard(i, j) && this.board[i][j] == V.EMPTY) {
612 moves.push(this.getBasicMove([x, y], [i, j]));
d1be8046 613 if (oneStep) continue outerLoop;
1c9f093d
BA
614 i += step[0];
615 j += step[1];
616 }
6808d7a1
BA
617 if (V.OnBoard(i, j) && this.canTake([x, y], [i, j]))
618 moves.push(this.getBasicMove([x, y], [i, j]));
1c9f093d
BA
619 }
620 return moves;
621 }
622
623 // What are the pawn moves from square x,y ?
6808d7a1 624 getPotentialPawnMoves([x, y]) {
1c9f093d
BA
625 const color = this.turn;
626 let moves = [];
6808d7a1
BA
627 const [sizeX, sizeY] = [V.size.x, V.size.y];
628 const shiftX = color == "w" ? -1 : 1;
629 const firstRank = color == "w" ? sizeX - 1 : 0;
630 const startRank = color == "w" ? sizeX - 2 : 1;
631 const lastRank = color == "w" ? 0 : sizeX - 1;
632 const pawnColor = this.getColor(x, y); //can be different for checkered
1c9f093d
BA
633
634 // NOTE: next condition is generally true (no pawn on last rank)
6808d7a1
BA
635 if (x + shiftX >= 0 && x + shiftX < sizeX) {
636 const finalPieces =
637 x + shiftX == lastRank
638 ? [V.ROOK, V.KNIGHT, V.BISHOP, V.QUEEN]
639 : [V.PAWN];
6808d7a1 640 if (this.board[x + shiftX][y] == V.EMPTY) {
71ef1664 641 // One square forward
6808d7a1
BA
642 for (let piece of finalPieces) {
643 moves.push(
644 this.getBasicMove([x, y], [x + shiftX, y], {
645 c: pawnColor,
646 p: piece
647 })
648 );
1c9f093d
BA
649 }
650 // Next condition because pawns on 1st rank can generally jump
6808d7a1
BA
651 if (
652 [startRank, firstRank].includes(x) &&
653 this.board[x + 2 * shiftX][y] == V.EMPTY
654 ) {
1c9f093d 655 // Two squares jump
6808d7a1 656 moves.push(this.getBasicMove([x, y], [x + 2 * shiftX, y]));
1c9f093d
BA
657 }
658 }
659 // Captures
6808d7a1
BA
660 for (let shiftY of [-1, 1]) {
661 if (
662 y + shiftY >= 0 &&
663 y + shiftY < sizeY &&
664 this.board[x + shiftX][y + shiftY] != V.EMPTY &&
665 this.canTake([x, y], [x + shiftX, y + shiftY])
666 ) {
667 for (let piece of finalPieces) {
668 moves.push(
669 this.getBasicMove([x, y], [x + shiftX, y + shiftY], {
670 c: pawnColor,
671 p: piece
672 })
673 );
1c9f093d
BA
674 }
675 }
676 }
677 }
678
6808d7a1 679 if (V.HasEnpassant) {
1c9f093d
BA
680 // En passant
681 const Lep = this.epSquares.length;
6808d7a1
BA
682 const epSquare = this.epSquares[Lep - 1]; //always at least one element
683 if (
684 !!epSquare &&
685 epSquare.x == x + shiftX &&
686 Math.abs(epSquare.y - y) == 1
687 ) {
688 let enpassantMove = this.getBasicMove([x, y], [epSquare.x, epSquare.y]);
1c9f093d
BA
689 enpassantMove.vanish.push({
690 x: x,
691 y: epSquare.y,
6808d7a1
BA
692 p: "p",
693 c: this.getColor(x, epSquare.y)
1c9f093d
BA
694 });
695 moves.push(enpassantMove);
696 }
697 }
698
699 return moves;
700 }
701
702 // What are the rook moves from square x,y ?
6808d7a1 703 getPotentialRookMoves(sq) {
1c9f093d
BA
704 return this.getSlideNJumpMoves(sq, V.steps[V.ROOK]);
705 }
706
707 // What are the knight moves from square x,y ?
6808d7a1 708 getPotentialKnightMoves(sq) {
1c9f093d
BA
709 return this.getSlideNJumpMoves(sq, V.steps[V.KNIGHT], "oneStep");
710 }
711
712 // What are the bishop moves from square x,y ?
6808d7a1 713 getPotentialBishopMoves(sq) {
1c9f093d
BA
714 return this.getSlideNJumpMoves(sq, V.steps[V.BISHOP]);
715 }
716
717 // What are the queen moves from square x,y ?
6808d7a1
BA
718 getPotentialQueenMoves(sq) {
719 return this.getSlideNJumpMoves(
720 sq,
721 V.steps[V.ROOK].concat(V.steps[V.BISHOP])
722 );
1c9f093d
BA
723 }
724
725 // What are the king moves from square x,y ?
6808d7a1 726 getPotentialKingMoves(sq) {
1c9f093d 727 // Initialize with normal moves
6808d7a1
BA
728 let moves = this.getSlideNJumpMoves(
729 sq,
730 V.steps[V.ROOK].concat(V.steps[V.BISHOP]),
731 "oneStep"
732 );
1c9f093d
BA
733 return moves.concat(this.getCastleMoves(sq));
734 }
735
6808d7a1
BA
736 getCastleMoves([x, y]) {
737 const c = this.getColor(x, y);
738 if (x != (c == "w" ? V.size.x - 1 : 0) || y != this.INIT_COL_KING[c])
1c9f093d
BA
739 return []; //x isn't first rank, or king has moved (shortcut)
740
741 // Castling ?
742 const oppCol = V.GetOppCol(c);
743 let moves = [];
744 let i = 0;
9bd6786b 745 // King, then rook:
6808d7a1
BA
746 const finalSquares = [
747 [2, 3],
748 [V.size.y - 2, V.size.y - 3]
9bd6786b 749 ];
6808d7a1
BA
750 castlingCheck: for (
751 let castleSide = 0;
752 castleSide < 2;
753 castleSide++ //large, then small
754 ) {
755 if (!this.castleFlags[c][castleSide]) continue;
1c9f093d
BA
756 // If this code is reached, rooks and king are on initial position
757
2beba6db
BA
758 // Nothing on the path of the king ? (and no checks)
759 const finDist = finalSquares[castleSide][0] - y;
760 let step = finDist / Math.max(1, Math.abs(finDist));
761 i = y;
6808d7a1
BA
762 do {
763 if (
764 this.isAttacked([x, i], [oppCol]) ||
765 (this.board[x][i] != V.EMPTY &&
766 // NOTE: next check is enough, because of chessboard constraints
767 (this.getColor(x, i) != c ||
768 ![V.KING, V.ROOK].includes(this.getPiece(x, i))))
769 ) {
1c9f093d
BA
770 continue castlingCheck;
771 }
2beba6db 772 i += step;
6808d7a1 773 } while (i != finalSquares[castleSide][0]);
1c9f093d
BA
774
775 // Nothing on the path to the rook?
6808d7a1
BA
776 step = castleSide == 0 ? -1 : 1;
777 for (i = y + step; i != this.INIT_COL_ROOK[c][castleSide]; i += step) {
778 if (this.board[x][i] != V.EMPTY) continue castlingCheck;
1c9f093d
BA
779 }
780 const rookPos = this.INIT_COL_ROOK[c][castleSide];
781
782 // Nothing on final squares, except maybe king and castling rook?
6808d7a1
BA
783 for (i = 0; i < 2; i++) {
784 if (
785 this.board[x][finalSquares[castleSide][i]] != V.EMPTY &&
786 this.getPiece(x, finalSquares[castleSide][i]) != V.KING &&
787 finalSquares[castleSide][i] != rookPos
788 ) {
1c9f093d
BA
789 continue castlingCheck;
790 }
791 }
792
793 // If this code is reached, castle is valid
6808d7a1
BA
794 moves.push(
795 new Move({
796 appear: [
797 new PiPo({ x: x, y: finalSquares[castleSide][0], p: V.KING, c: c }),
798 new PiPo({ x: x, y: finalSquares[castleSide][1], p: V.ROOK, c: c })
799 ],
800 vanish: [
801 new PiPo({ x: x, y: y, p: V.KING, c: c }),
802 new PiPo({ x: x, y: rookPos, p: V.ROOK, c: c })
803 ],
804 end:
805 Math.abs(y - rookPos) <= 2
806 ? { x: x, y: rookPos }
807 : { x: x, y: y + 2 * (castleSide == 0 ? -1 : 1) }
808 })
809 );
1c9f093d
BA
810 }
811
812 return moves;
813 }
814
815 ////////////////////
816 // MOVES VALIDATION
817
818 // For the interface: possible moves for the current turn from square sq
6808d7a1
BA
819 getPossibleMovesFrom(sq) {
820 return this.filterValid(this.getPotentialMovesFrom(sq));
1c9f093d
BA
821 }
822
823 // TODO: promotions (into R,B,N,Q) should be filtered only once
6808d7a1
BA
824 filterValid(moves) {
825 if (moves.length == 0) return [];
1c9f093d
BA
826 const color = this.turn;
827 return moves.filter(m => {
828 this.play(m);
829 const res = !this.underCheck(color);
830 this.undo(m);
831 return res;
832 });
833 }
834
835 // Search for all valid moves considering current turn
836 // (for engine and game end)
6808d7a1 837 getAllValidMoves() {
1c9f093d 838 const color = this.turn;
1c9f093d 839 let potentialMoves = [];
6808d7a1
BA
840 for (let i = 0; i < V.size.x; i++) {
841 for (let j = 0; j < V.size.y; j++) {
d1be8046 842 if (this.getColor(i, j) == color) {
6808d7a1
BA
843 Array.prototype.push.apply(
844 potentialMoves,
845 this.getPotentialMovesFrom([i, j])
846 );
1c9f093d
BA
847 }
848 }
849 }
850 return this.filterValid(potentialMoves);
851 }
852
853 // Stop at the first move found
6808d7a1 854 atLeastOneMove() {
1c9f093d 855 const color = this.turn;
6808d7a1
BA
856 for (let i = 0; i < V.size.x; i++) {
857 for (let j = 0; j < V.size.y; j++) {
d1be8046 858 if (this.getColor(i, j) == color) {
6808d7a1
BA
859 const moves = this.getPotentialMovesFrom([i, j]);
860 if (moves.length > 0) {
861 for (let k = 0; k < moves.length; k++) {
862 if (this.filterValid([moves[k]]).length > 0) return true;
1c9f093d
BA
863 }
864 }
865 }
866 }
867 }
868 return false;
869 }
870
871 // Check if pieces of color in 'colors' are attacking (king) on square x,y
6808d7a1
BA
872 isAttacked(sq, colors) {
873 return (
874 this.isAttackedByPawn(sq, colors) ||
875 this.isAttackedByRook(sq, colors) ||
876 this.isAttackedByKnight(sq, colors) ||
877 this.isAttackedByBishop(sq, colors) ||
878 this.isAttackedByQueen(sq, colors) ||
879 this.isAttackedByKing(sq, colors)
880 );
1c9f093d
BA
881 }
882
d1be8046
BA
883 // Generic method for non-pawn pieces ("sliding or jumping"):
884 // is x,y attacked by a piece of color in array 'colors' ?
885 isAttackedBySlideNJump([x, y], colors, piece, steps, oneStep) {
886 for (let step of steps) {
887 let rx = x + step[0],
888 ry = y + step[1];
889 while (V.OnBoard(rx, ry) && this.board[rx][ry] == V.EMPTY && !oneStep) {
890 rx += step[0];
891 ry += step[1];
892 }
893 if (
894 V.OnBoard(rx, ry) &&
895 this.getPiece(rx, ry) === piece &&
896 colors.includes(this.getColor(rx, ry))
897 ) {
898 return true;
899 }
900 }
901 return false;
902 }
903
1c9f093d 904 // Is square x,y attacked by 'colors' pawns ?
6808d7a1
BA
905 isAttackedByPawn([x, y], colors) {
906 for (let c of colors) {
d1be8046 907 const pawnShift = c == "w" ? 1 : -1;
6808d7a1
BA
908 if (x + pawnShift >= 0 && x + pawnShift < V.size.x) {
909 for (let i of [-1, 1]) {
910 if (
911 y + i >= 0 &&
912 y + i < V.size.y &&
913 this.getPiece(x + pawnShift, y + i) == V.PAWN &&
914 this.getColor(x + pawnShift, y + i) == c
915 ) {
1c9f093d
BA
916 return true;
917 }
918 }
919 }
920 }
921 return false;
922 }
923
924 // Is square x,y attacked by 'colors' rooks ?
6808d7a1 925 isAttackedByRook(sq, colors) {
1c9f093d
BA
926 return this.isAttackedBySlideNJump(sq, colors, V.ROOK, V.steps[V.ROOK]);
927 }
928
929 // Is square x,y attacked by 'colors' knights ?
6808d7a1
BA
930 isAttackedByKnight(sq, colors) {
931 return this.isAttackedBySlideNJump(
932 sq,
933 colors,
934 V.KNIGHT,
935 V.steps[V.KNIGHT],
936 "oneStep"
937 );
1c9f093d
BA
938 }
939
940 // Is square x,y attacked by 'colors' bishops ?
6808d7a1 941 isAttackedByBishop(sq, colors) {
1c9f093d
BA
942 return this.isAttackedBySlideNJump(sq, colors, V.BISHOP, V.steps[V.BISHOP]);
943 }
944
945 // Is square x,y attacked by 'colors' queens ?
6808d7a1
BA
946 isAttackedByQueen(sq, colors) {
947 return this.isAttackedBySlideNJump(
948 sq,
949 colors,
950 V.QUEEN,
951 V.steps[V.ROOK].concat(V.steps[V.BISHOP])
952 );
1c9f093d
BA
953 }
954
955 // Is square x,y attacked by 'colors' king(s) ?
6808d7a1
BA
956 isAttackedByKing(sq, colors) {
957 return this.isAttackedBySlideNJump(
958 sq,
959 colors,
960 V.KING,
961 V.steps[V.ROOK].concat(V.steps[V.BISHOP]),
962 "oneStep"
963 );
1c9f093d
BA
964 }
965
1c9f093d 966 // Is color under check after his move ?
6808d7a1 967 underCheck(color) {
1c9f093d
BA
968 return this.isAttacked(this.kingPos[color], [V.GetOppCol(color)]);
969 }
970
971 /////////////////
972 // MOVES PLAYING
973
974 // Apply a move on board
6808d7a1
BA
975 static PlayOnBoard(board, move) {
976 for (let psq of move.vanish) board[psq.x][psq.y] = V.EMPTY;
977 for (let psq of move.appear) board[psq.x][psq.y] = psq.c + psq.p;
1c9f093d
BA
978 }
979 // Un-apply the played move
6808d7a1
BA
980 static UndoOnBoard(board, move) {
981 for (let psq of move.appear) board[psq.x][psq.y] = V.EMPTY;
982 for (let psq of move.vanish) board[psq.x][psq.y] = psq.c + psq.p;
1c9f093d
BA
983 }
984
985 // After move is played, update variables + flags
6808d7a1 986 updateVariables(move) {
1c9f093d 987 let piece = undefined;
78d64531
BA
988 // TODO: update variables before move is played, and just use this.turn ?
989 // (doesn't work in general, think MarseilleChess)
1c9f093d 990 let c = undefined;
6808d7a1 991 if (move.vanish.length >= 1) {
1c9f093d
BA
992 // Usual case, something is moved
993 piece = move.vanish[0].p;
994 c = move.vanish[0].c;
6808d7a1 995 } else {
1c9f093d
BA
996 // Crazyhouse-like variants
997 piece = move.appear[0].p;
998 c = move.appear[0].c;
999 }
78d64531
BA
1000 if (!['w','b'].includes(c)) {
1001 // Checkered, for example
1c9f093d
BA
1002 c = V.GetOppCol(this.turn);
1003 }
6808d7a1 1004 const firstRank = c == "w" ? V.size.x - 1 : 0;
1c9f093d
BA
1005
1006 // Update king position + flags
6808d7a1 1007 if (piece == V.KING && move.appear.length > 0) {
1c9f093d
BA
1008 this.kingPos[c][0] = move.appear[0].x;
1009 this.kingPos[c][1] = move.appear[0].y;
6808d7a1 1010 if (V.HasFlags) this.castleFlags[c] = [false, false];
1c9f093d
BA
1011 return;
1012 }
6808d7a1 1013 if (V.HasFlags) {
1c9f093d
BA
1014 // Update castling flags if rooks are moved
1015 const oppCol = V.GetOppCol(c);
6808d7a1
BA
1016 const oppFirstRank = V.size.x - 1 - firstRank;
1017 if (
1018 move.start.x == firstRank && //our rook moves?
1019 this.INIT_COL_ROOK[c].includes(move.start.y)
1020 ) {
1021 const flagIdx = move.start.y == this.INIT_COL_ROOK[c][0] ? 0 : 1;
1c9f093d 1022 this.castleFlags[c][flagIdx] = false;
6808d7a1
BA
1023 } else if (
1024 move.end.x == oppFirstRank && //we took opponent rook?
1025 this.INIT_COL_ROOK[oppCol].includes(move.end.y)
1026 ) {
1027 const flagIdx = move.end.y == this.INIT_COL_ROOK[oppCol][0] ? 0 : 1;
1c9f093d
BA
1028 this.castleFlags[oppCol][flagIdx] = false;
1029 }
1030 }
1031 }
1032
1033 // After move is undo-ed *and flags resetted*, un-update other variables
1034 // TODO: more symmetry, by storing flags increment in move (?!)
6808d7a1 1035 unupdateVariables(move) {
1c9f093d 1036 // (Potentially) Reset king position
6808d7a1
BA
1037 const c = this.getColor(move.start.x, move.start.y);
1038 if (this.getPiece(move.start.x, move.start.y) == V.KING)
1c9f093d
BA
1039 this.kingPos[c] = [move.start.x, move.start.y];
1040 }
1041
6808d7a1 1042 play(move) {
1c9f093d 1043 // DEBUG:
9bd6786b
BA
1044// if (!this.states) this.states = [];
1045// const stateFen = this.getBaseFen() + this.getTurnFen() + this.getFlagsFen();
1046// this.states.push(stateFen);
6808d7a1
BA
1047
1048 if (V.HasFlags) move.flags = JSON.stringify(this.aggregateFlags()); //save flags (for undo)
1049 if (V.HasEnpassant) this.epSquares.push(this.getEpSquare(move));
1c9f093d
BA
1050 V.PlayOnBoard(this.board, move);
1051 this.turn = V.GetOppCol(this.turn);
1052 this.movesCount++;
1053 this.updateVariables(move);
1054 }
1055
6808d7a1
BA
1056 undo(move) {
1057 if (V.HasEnpassant) this.epSquares.pop();
1058 if (V.HasFlags) this.disaggregateFlags(JSON.parse(move.flags));
1c9f093d
BA
1059 V.UndoOnBoard(this.board, move);
1060 this.turn = V.GetOppCol(this.turn);
1061 this.movesCount--;
1062 this.unupdateVariables(move);
1063
1064 // DEBUG:
9bd6786b
BA
1065// const stateFen = this.getBaseFen() + this.getTurnFen() + this.getFlagsFen();
1066// if (stateFen != this.states[this.states.length-1]) debugger;
1067// this.states.pop();
1c9f093d
BA
1068 }
1069
1070 ///////////////
1071 // END OF GAME
1072
1073 // What is the score ? (Interesting if game is over)
6808d7a1
BA
1074 getCurrentScore() {
1075 if (this.atLeastOneMove())
1c9f093d
BA
1076 return "*";
1077
1078 // Game over
1079 const color = this.turn;
1080 // No valid move: stalemate or checkmate?
1081 if (!this.isAttacked(this.kingPos[color], [V.GetOppCol(color)]))
1082 return "1/2";
1083 // OK, checkmate
6808d7a1 1084 return color == "w" ? "0-1" : "1-0";
1c9f093d
BA
1085 }
1086
1087 ///////////////
1088 // ENGINE PLAY
1089
1090 // Pieces values
6808d7a1 1091 static get VALUES() {
1c9f093d 1092 return {
6808d7a1
BA
1093 p: 1,
1094 r: 5,
1095 n: 3,
1096 b: 3,
1097 q: 9,
1098 k: 1000
1c9f093d
BA
1099 };
1100 }
1101
1102 // "Checkmate" (unreachable eval)
6808d7a1
BA
1103 static get INFINITY() {
1104 return 9999;
1105 }
1c9f093d
BA
1106
1107 // At this value or above, the game is over
6808d7a1
BA
1108 static get THRESHOLD_MATE() {
1109 return V.INFINITY;
1110 }
1c9f093d
BA
1111
1112 // Search depth: 2 for high branching factor, 4 for small (Loser chess, eg.)
6808d7a1
BA
1113 static get SEARCH_DEPTH() {
1114 return 3;
1115 }
1c9f093d 1116
6808d7a1 1117 getComputerMove() {
1c9f093d
BA
1118 const maxeval = V.INFINITY;
1119 const color = this.turn;
1120 // Some variants may show a bigger moves list to the human (Switching),
1121 // thus the argument "computer" below (which is generally ignored)
a97bdbda 1122 let moves1 = this.getAllValidMoves();
c322a844 1123
6808d7a1 1124 if (moves1.length == 0)
e71161fb 1125 // TODO: this situation should not happen
41cb9b94 1126 return null;
1c9f093d 1127
1c9f093d 1128 // Rank moves using a min-max at depth 2
6808d7a1 1129 for (let i = 0; i < moves1.length; i++) {
1c9f093d 1130 // Initial self evaluation is very low: "I'm checkmated"
6808d7a1 1131 moves1[i].eval = (color == "w" ? -1 : 1) * maxeval;
1c9f093d
BA
1132 this.play(moves1[i]);
1133 const score1 = this.getCurrentScore();
1134 let eval2 = undefined;
6808d7a1 1135 if (score1 == "*") {
1c9f093d 1136 // Initial enemy evaluation is very low too, for him
6808d7a1 1137 eval2 = (color == "w" ? 1 : -1) * maxeval;
1c9f093d 1138 // Second half-move:
a97bdbda 1139 let moves2 = this.getAllValidMoves();
6808d7a1 1140 for (let j = 0; j < moves2.length; j++) {
1c9f093d
BA
1141 this.play(moves2[j]);
1142 const score2 = this.getCurrentScore();
6808d7a1
BA
1143 let evalPos = 0; //1/2 value
1144 switch (score2) {
1145 case "*":
1146 evalPos = this.evalPosition();
1147 break;
1148 case "1-0":
1149 evalPos = maxeval;
1150 break;
1151 case "0-1":
1152 evalPos = -maxeval;
1153 break;
1154 }
1155 if (
1156 (color == "w" && evalPos < eval2) ||
1157 (color == "b" && evalPos > eval2)
1158 ) {
1c9f093d
BA
1159 eval2 = evalPos;
1160 }
1161 this.undo(moves2[j]);
1162 }
6808d7a1
BA
1163 } else eval2 = score1 == "1/2" ? 0 : (score1 == "1-0" ? 1 : -1) * maxeval;
1164 if (
1165 (color == "w" && eval2 > moves1[i].eval) ||
1166 (color == "b" && eval2 < moves1[i].eval)
1167 ) {
1c9f093d
BA
1168 moves1[i].eval = eval2;
1169 }
1170 this.undo(moves1[i]);
1171 }
6808d7a1
BA
1172 moves1.sort((a, b) => {
1173 return (color == "w" ? 1 : -1) * (b.eval - a.eval);
1174 });
a97bdbda 1175// console.log(moves1.map(m => { return [this.getNotation(m), m.eval]; }));
1c9f093d
BA
1176
1177 let candidates = [0]; //indices of candidates moves
6808d7a1 1178 for (let j = 1; j < moves1.length && moves1[j].eval == moves1[0].eval; j++)
1c9f093d 1179 candidates.push(j);
0c3fe8a6 1180 let currentBest = moves1[candidates[randInt(candidates.length)]];
1c9f093d 1181
1c9f093d 1182 // Skip depth 3+ if we found a checkmate (or if we are checkmated in 1...)
6808d7a1 1183 if (V.SEARCH_DEPTH >= 3 && Math.abs(moves1[0].eval) < V.THRESHOLD_MATE) {
656b1878
BA
1184 // From here, depth >= 3: may take a while, so we control time
1185 const timeStart = Date.now();
6808d7a1
BA
1186 for (let i = 0; i < moves1.length; i++) {
1187 if (Date.now() - timeStart >= 5000)
1188 //more than 5 seconds
1c9f093d
BA
1189 return currentBest; //depth 2 at least
1190 this.play(moves1[i]);
1191 // 0.1 * oldEval : heuristic to avoid some bad moves (not all...)
6808d7a1
BA
1192 moves1[i].eval =
1193 0.1 * moves1[i].eval +
1194 this.alphabeta(V.SEARCH_DEPTH - 1, -maxeval, maxeval);
1c9f093d
BA
1195 this.undo(moves1[i]);
1196 }
6808d7a1
BA
1197 moves1.sort((a, b) => {
1198 return (color == "w" ? 1 : -1) * (b.eval - a.eval);
1199 });
1200 } else return currentBest;
1c5bfdf2 1201// console.log(moves1.map(m => { return [this.getNotation(m), m.eval]; }));
1c9f093d
BA
1202
1203 candidates = [0];
6808d7a1 1204 for (let j = 1; j < moves1.length && moves1[j].eval == moves1[0].eval; j++)
1c9f093d 1205 candidates.push(j);
656b1878 1206 return moves1[candidates[randInt(candidates.length)]];
1c9f093d
BA
1207 }
1208
6808d7a1 1209 alphabeta(depth, alpha, beta) {
1c9f093d
BA
1210 const maxeval = V.INFINITY;
1211 const color = this.turn;
1212 const score = this.getCurrentScore();
1213 if (score != "*")
6808d7a1
BA
1214 return score == "1/2" ? 0 : (score == "1-0" ? 1 : -1) * maxeval;
1215 if (depth == 0) return this.evalPosition();
a97bdbda 1216 const moves = this.getAllValidMoves();
6808d7a1
BA
1217 let v = color == "w" ? -maxeval : maxeval;
1218 if (color == "w") {
1219 for (let i = 0; i < moves.length; i++) {
1c9f093d 1220 this.play(moves[i]);
6808d7a1 1221 v = Math.max(v, this.alphabeta(depth - 1, alpha, beta));
1c9f093d
BA
1222 this.undo(moves[i]);
1223 alpha = Math.max(alpha, v);
6808d7a1 1224 if (alpha >= beta) break; //beta cutoff
1c9f093d 1225 }
1c5bfdf2 1226 }
6808d7a1 1227 else {
1c5bfdf2 1228 // color=="b"
6808d7a1 1229 for (let i = 0; i < moves.length; i++) {
1c9f093d 1230 this.play(moves[i]);
6808d7a1 1231 v = Math.min(v, this.alphabeta(depth - 1, alpha, beta));
1c9f093d
BA
1232 this.undo(moves[i]);
1233 beta = Math.min(beta, v);
6808d7a1 1234 if (alpha >= beta) break; //alpha cutoff
1c9f093d
BA
1235 }
1236 }
1237 return v;
1238 }
1239
6808d7a1 1240 evalPosition() {
1c9f093d
BA
1241 let evaluation = 0;
1242 // Just count material for now
6808d7a1
BA
1243 for (let i = 0; i < V.size.x; i++) {
1244 for (let j = 0; j < V.size.y; j++) {
1245 if (this.board[i][j] != V.EMPTY) {
1246 const sign = this.getColor(i, j) == "w" ? 1 : -1;
1247 evaluation += sign * V.VALUES[this.getPiece(i, j)];
1c9f093d
BA
1248 }
1249 }
1250 }
1251 return evaluation;
1252 }
1253
1254 /////////////////////////
1255 // MOVES + GAME NOTATION
1256 /////////////////////////
1257
1258 // Context: just before move is played, turn hasn't changed
1259 // TODO: un-ambiguous notation (switch on piece type, check directions...)
6808d7a1
BA
1260 getNotation(move) {
1261 if (move.appear.length == 2 && move.appear[0].p == V.KING)
1cd3e362 1262 // Castle
6808d7a1 1263 return move.end.y < move.start.y ? "0-0-0" : "0-0";
1c9f093d
BA
1264
1265 // Translate final square
1266 const finalSquare = V.CoordsToSquare(move.end);
1267
1268 const piece = this.getPiece(move.start.x, move.start.y);
6808d7a1 1269 if (piece == V.PAWN) {
1c9f093d
BA
1270 // Pawn move
1271 let notation = "";
6808d7a1 1272 if (move.vanish.length > move.appear.length) {
1c9f093d
BA
1273 // Capture
1274 const startColumn = V.CoordToColumn(move.start.y);
1275 notation = startColumn + "x" + finalSquare;
78d64531 1276 }
6808d7a1
BA
1277 else notation = finalSquare;
1278 if (move.appear.length > 0 && move.appear[0].p != V.PAWN)
78d64531 1279 // Promotion
1c9f093d
BA
1280 notation += "=" + move.appear[0].p.toUpperCase();
1281 return notation;
1282 }
6808d7a1
BA
1283 // Piece movement
1284 return (
1285 piece.toUpperCase() +
1286 (move.vanish.length > move.appear.length ? "x" : "") +
1287 finalSquare
1288 );
1289 }
1290};