Fix README
[vchess.git] / public / javascripts / base_rules.js
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BA
1// (Orthodox) Chess rules are defined in ChessRules class.
2// Variants generally inherit from it, and modify some parts.
3
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4class PiPo //Piece+Position
5{
6 // o: {piece[p], color[c], posX[x], posY[y]}
7 constructor(o)
8 {
9 this.p = o.p;
10 this.c = o.c;
11 this.x = o.x;
12 this.y = o.y;
13 }
14}
15
098e8468 16// TODO: for animation, moves should contains "moving" and "fading" maybe...
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17class Move
18{
19 // o: {appear, vanish, [start,] [end,]}
20 // appear,vanish = arrays of PiPo
21 // start,end = coordinates to apply to trigger move visually (think castle)
22 constructor(o)
23 {
24 this.appear = o.appear;
25 this.vanish = o.vanish;
26 this.start = !!o.start ? o.start : {x:o.vanish[0].x, y:o.vanish[0].y};
27 this.end = !!o.end ? o.end : {x:o.appear[0].x, y:o.appear[0].y};
28 }
29}
30
31// NOTE: x coords = top to bottom; y = left to right (from white player perspective)
32class ChessRules
33{
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34 //////////////
35 // MISC UTILS
36
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37 static get HasFlags() { return true; } //some variants don't have flags
38
39 static get HasEnpassant() { return true; } //some variants don't have ep.
40
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41 // Path to pieces
42 static getPpath(b)
43 {
44 return b; //usual pieces in pieces/ folder
45 }
1a788978 46
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47 // Turn "wb" into "B" (for FEN)
48 static board2fen(b)
49 {
50 return b[0]=='w' ? b[1].toUpperCase() : b[1];
51 }
1a788978 52
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53 // Turn "p" into "bp" (for board)
54 static fen2board(f)
55 {
56 return f.charCodeAt()<=90 ? "w"+f.toLowerCase() : "b"+f;
57 }
58
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59 // Check if FEN describe a position
60 static IsGoodFen(fen)
61 {
1a788978 62 const fenParsed = V.ParseFen(fen);
7931e479 63 // 1) Check position
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64 if (!V.IsGoodPosition(fenParsed.position))
65 return false;
66 // 2) Check turn
6e62b1c7 67 if (!fenParsed.turn || !V.IsGoodTurn(fenParsed.turn))
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68 return false;
69 // 3) Check flags
70 if (V.HasFlags && (!fenParsed.flags || !V.IsGoodFlags(fenParsed.flags)))
71 return false;
72 // 4) Check enpassant
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73 if (V.HasEnpassant &&
74 (!fenParsed.enpassant || !V.IsGoodEnpassant(fenParsed.enpassant)))
2d7194bd 75 {
6e62b1c7 76 return false;
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77 }
78 return true;
79 }
80
81 // Is position part of the FEN a priori correct?
82 static IsGoodPosition(position)
83 {
84 if (position.length == 0)
85 return false;
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86 const rows = position.split("/");
87 if (rows.length != V.size.x)
88 return false;
89 for (let row of rows)
90 {
91 let sumElts = 0;
92 for (let i=0; i<row.length; i++)
93 {
94 if (V.PIECES.includes(row[i].toLowerCase()))
95 sumElts++;
96 else
97 {
98 const num = parseInt(row[i]);
99 if (isNaN(num))
100 return false;
101 sumElts += num;
102 }
103 }
104 if (sumElts != V.size.y)
105 return false;
106 }
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107 return true;
108 }
109
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110 // For FEN checking
111 static IsGoodTurn(turn)
112 {
113 return ["w","b"].includes(turn);
114 }
115
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116 // For FEN checking
117 static IsGoodFlags(flags)
118 {
119 return !!flags.match(/^[01]{4,4}$/);
120 }
121
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122 static IsGoodEnpassant(enpassant)
123 {
124 if (enpassant != "-")
125 {
126 const ep = V.SquareToCoords(fenParsed.enpassant);
127 if (isNaN(ep.x) || !V.OnBoard(ep))
128 return false;
129 }
130 return true;
131 }
132
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133 // 3 --> d (column number to letter)
134 static CoordToColumn(colnum)
135 {
136 return String.fromCharCode(97 + colnum);
137 }
138
139 // d --> 3 (column letter to number)
5915f720 140 static ColumnToCoord(column)
2d7194bd 141 {
5915f720 142 return column.charCodeAt(0) - 97;
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143 }
144
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145 // a4 --> {x:3,y:0}
146 static SquareToCoords(sq)
147 {
148 return {
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149 // NOTE: column is always one char => max 26 columns
150 // row is counted from black side => subtraction
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151 x: V.size.x - parseInt(sq.substr(1)),
152 y: sq[0].charCodeAt() - 97
153 };
154 }
155
156 // {x:0,y:4} --> e8
157 static CoordsToSquare(coords)
158 {
26c1e3bd 159 return V.CoordToColumn(coords.y) + (V.size.x - coords.x);
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160 }
161
162 // Aggregates flags into one object
163 aggregateFlags()
164 {
165 return this.castleFlags;
166 }
167
168 // Reverse operation
169 disaggregateFlags(flags)
170 {
171 this.castleFlags = flags;
172 }
173
174 // En-passant square, if any
175 getEpSquare(moveOrSquare)
176 {
177 if (!moveOrSquare)
178 return undefined;
179 if (typeof moveOrSquare === "string")
180 {
181 const square = moveOrSquare;
182 if (square == "-")
183 return undefined;
2d7194bd 184 return V.SquareToCoords(square);
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185 }
186 // Argument is a move:
187 const move = moveOrSquare;
188 const [sx,sy,ex] = [move.start.x,move.start.y,move.end.x];
189 if (this.getPiece(sx,sy) == V.PAWN && Math.abs(sx - ex) == 2)
190 {
191 return {
192 x: (sx + ex)/2,
193 y: sy
194 };
195 }
196 return undefined; //default
197 }
198
199 // Can thing on square1 take thing on square2
200 canTake([x1,y1], [x2,y2])
201 {
202 return this.getColor(x1,y1) !== this.getColor(x2,y2);
203 }
204
205 // Is (x,y) on the chessboard?
206 static OnBoard(x,y)
207 {
208 return (x>=0 && x<V.size.x && y>=0 && y<V.size.y);
209 }
210
211 // Used in interface: 'side' arg == player color
212 canIplay(side, [x,y])
213 {
214 return (this.turn == side && this.getColor(x,y) == side);
215 }
216
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217 // On which squares is color under check ? (for interface)
218 getCheckSquares(color)
1a788978 219 {
f6dbe8e3 220 return this.isAttacked(this.kingPos[color], [this.getOppCol(color)])
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221 ? [JSON.parse(JSON.stringify(this.kingPos[color]))] //need to duplicate!
222 : [];
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223 }
224
225 /////////////
226 // FEN UTILS
227
228 // Setup the initial random (assymetric) position
229 static GenRandInitFen()
230 {
231 let pieces = { "w": new Array(8), "b": new Array(8) };
232 // Shuffle pieces on first and last rank
233 for (let c of ["w","b"])
234 {
235 let positions = _.range(8);
236
237 // Get random squares for bishops
238 let randIndex = 2 * _.random(3);
26c1e3bd 239 const bishop1Pos = positions[randIndex];
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240 // The second bishop must be on a square of different color
241 let randIndex_tmp = 2 * _.random(3) + 1;
26c1e3bd 242 const bishop2Pos = positions[randIndex_tmp];
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243 // Remove chosen squares
244 positions.splice(Math.max(randIndex,randIndex_tmp), 1);
245 positions.splice(Math.min(randIndex,randIndex_tmp), 1);
246
247 // Get random squares for knights
248 randIndex = _.random(5);
26c1e3bd 249 const knight1Pos = positions[randIndex];
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250 positions.splice(randIndex, 1);
251 randIndex = _.random(4);
26c1e3bd 252 const knight2Pos = positions[randIndex];
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253 positions.splice(randIndex, 1);
254
255 // Get random square for queen
256 randIndex = _.random(3);
26c1e3bd 257 const queenPos = positions[randIndex];
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258 positions.splice(randIndex, 1);
259
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260 // Rooks and king positions are now fixed,
261 // because of the ordering rook-king-rook
262 const rook1Pos = positions[0];
263 const kingPos = positions[1];
264 const rook2Pos = positions[2];
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265
266 // Finally put the shuffled pieces in the board array
267 pieces[c][rook1Pos] = 'r';
268 pieces[c][knight1Pos] = 'n';
269 pieces[c][bishop1Pos] = 'b';
270 pieces[c][queenPos] = 'q';
271 pieces[c][kingPos] = 'k';
272 pieces[c][bishop2Pos] = 'b';
273 pieces[c][knight2Pos] = 'n';
274 pieces[c][rook2Pos] = 'r';
275 }
276 return pieces["b"].join("") +
277 "/pppppppp/8/8/8/8/PPPPPPPP/" +
278 pieces["w"].join("").toUpperCase() +
279 " w 1111 -"; //add turn + flags + enpassant
280 }
281
282 // "Parse" FEN: just return untransformed string data
283 static ParseFen(fen)
284 {
285 const fenParts = fen.split(" ");
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286 let res =
287 {
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288 position: fenParts[0],
289 turn: fenParts[1],
1a788978 290 };
2d7194bd 291 let nextIdx = 2;
45109880 292 if (V.HasFlags)
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293 Object.assign(res, {flags: fenParts[nextIdx++]});
294 if (V.HasEnpassant)
295 Object.assign(res, {enpassant: fenParts[nextIdx]});
296 return res;
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297 }
298
299 // Return current fen (game state)
300 getFen()
301 {
6e62b1c7 302 return this.getBaseFen() + " " + this.getTurnFen() +
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303 (V.HasFlags ? (" " + this.getFlagsFen()) : "") +
304 (V.HasEnpassant ? (" " + this.getEnpassantFen()) : "");
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305 }
306
307 // Position part of the FEN string
308 getBaseFen()
309 {
310 let position = "";
311 for (let i=0; i<V.size.x; i++)
312 {
313 let emptyCount = 0;
314 for (let j=0; j<V.size.y; j++)
315 {
316 if (this.board[i][j] == V.EMPTY)
317 emptyCount++;
318 else
319 {
320 if (emptyCount > 0)
321 {
322 // Add empty squares in-between
323 position += emptyCount;
324 emptyCount = 0;
325 }
45109880 326 position += V.board2fen(this.board[i][j]);
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327 }
328 }
329 if (emptyCount > 0)
330 {
331 // "Flush remainder"
332 position += emptyCount;
333 }
334 if (i < V.size.x - 1)
335 position += "/"; //separate rows
336 }
337 return position;
338 }
339
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340 getTurnFen()
341 {
342 return this.turn;
343 }
344
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345 // Flags part of the FEN string
346 getFlagsFen()
347 {
348 let flags = "";
349 // Add castling flags
350 for (let i of ['w','b'])
351 {
352 for (let j=0; j<2; j++)
353 flags += (this.castleFlags[i][j] ? '1' : '0');
354 }
355 return flags;
356 }
357
358 // Enpassant part of the FEN string
359 getEnpassantFen()
360 {
361 const L = this.epSquares.length;
2d7194bd 362 if (!this.epSquares[L-1])
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363 return "-"; //no en-passant
364 return V.CoordsToSquare(this.epSquares[L-1]);
365 }
366
367 // Turn position fen into double array ["wb","wp","bk",...]
368 static GetBoard(position)
1d184b4c 369 {
1a788978 370 const rows = position.split("/");
0b7d99ec 371 let board = doubleArray(V.size.x, V.size.y, "");
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372 for (let i=0; i<rows.length; i++)
373 {
374 let j = 0;
375 for (let indexInRow = 0; indexInRow < rows[i].length; indexInRow++)
376 {
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377 const character = rows[i][indexInRow];
378 const num = parseInt(character);
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379 if (!isNaN(num))
380 j += num; //just shift j
381 else //something at position i,j
0b7d99ec 382 board[i][j++] = V.fen2board(character);
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383 }
384 }
385 return board;
386 }
387
dda21a71 388 // Extract (relevant) flags from fen
7931e479 389 setFlags(fenflags)
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390 {
391 // white a-castle, h-castle, black a-castle, h-castle
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392 this.castleFlags = {'w': [true,true], 'b': [true,true]};
393 if (!fenflags)
394 return;
1d184b4c 395 for (let i=0; i<4; i++)
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396 this.castleFlags[i < 2 ? 'w' : 'b'][i%2] = (fenflags.charAt(i) == '1');
397 }
398
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399 //////////////////
400 // INITIALIZATION
401
402 // Fen string fully describes the game state
403 constructor(fen, moves)
7931e479 404 {
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405 this.moves = moves;
406 const fenParsed = V.ParseFen(fen);
407 this.board = V.GetBoard(fenParsed.position);
6e62b1c7 408 this.turn = fenParsed.turn[0]; //[0] to work with MarseilleRules
1a788978 409 this.setOtherVariables(fen);
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410 }
411
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412 // Scan board for kings and rooks positions
413 scanKingsRooks(fen)
1a788978 414 {
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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
2d7194bd 418 const fenRows = V.ParseFen(fen).position.split("/");
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419 for (let i=0; i<fenRows.length; i++)
420 {
421 let k = 0; //column index on board
422 for (let j=0; j<fenRows[i].length; j++)
423 {
424 switch (fenRows[i].charAt(j))
425 {
426 case 'k':
427 this.kingPos['b'] = [i,k];
428 this.INIT_COL_KING['b'] = k;
429 break;
430 case 'K':
431 this.kingPos['w'] = [i,k];
432 this.INIT_COL_KING['w'] = k;
433 break;
434 case 'r':
435 if (this.INIT_COL_ROOK['b'][0] < 0)
436 this.INIT_COL_ROOK['b'][0] = k;
437 else
438 this.INIT_COL_ROOK['b'][1] = k;
439 break;
440 case 'R':
441 if (this.INIT_COL_ROOK['w'][0] < 0)
442 this.INIT_COL_ROOK['w'][0] = k;
443 else
444 this.INIT_COL_ROOK['w'][1] = k;
445 break;
446 default:
447 const num = parseInt(fenRows[i].charAt(j));
448 if (!isNaN(num))
449 k += (num-1);
450 }
451 k++;
452 }
453 }
454 }
455
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456 // Some additional variables from FEN (variant dependant)
457 setOtherVariables(fen)
458 {
459 // Set flags and enpassant:
460 const parsedFen = V.ParseFen(fen);
461 if (V.HasFlags)
45109880 462 this.setFlags(parsedFen.flags);
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463 if (V.HasEnpassant)
464 {
465 const epSq = parsedFen.enpassant != "-"
466 ? V.SquareToCoords(parsedFen.enpassant)
467 : undefined;
468 this.epSquares = [ epSq ];
469 }
470 // Search for king and rooks positions:
471 this.scanKingsRooks(fen);
472 }
473
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474 /////////////////////
475 // GETTERS & SETTERS
476
477 static get size()
478 {
479 return {x:8, y:8};
480 }
1d184b4c 481
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482 // Color of thing on suqare (i,j). 'undefined' if square is empty
483 getColor(i,j)
484 {
485 return this.board[i][j].charAt(0);
486 }
0b7d99ec 487
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488 // Piece type on square (i,j). 'undefined' if square is empty
489 getPiece(i,j)
490 {
491 return this.board[i][j].charAt(1);
492 }
1d184b4c 493
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494 // Get opponent color
495 getOppCol(color)
496 {
497 return (color=="w" ? "b" : "w");
498 }
1d184b4c 499
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500 get lastMove()
501 {
1d184b4c 502 const L = this.moves.length;
0b7d99ec 503 return (L>0 ? this.moves[L-1] : null);
1d184b4c 504 }
0b7d99ec 505
1a788978 506 // Pieces codes (for a clearer code)
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507 static get PAWN() { return 'p'; }
508 static get ROOK() { return 'r'; }
509 static get KNIGHT() { return 'n'; }
510 static get BISHOP() { return 'b'; }
511 static get QUEEN() { return 'q'; }
512 static get KING() { return 'k'; }
513
7931e479 514 // For FEN checking:
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515 static get PIECES()
516 {
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517 return [V.PAWN,V.ROOK,V.KNIGHT,V.BISHOP,V.QUEEN,V.KING];
518 }
519
1d184b4c 520 // Empty square
1a788978 521 static get EMPTY() { return ""; }
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522
523 // Some pieces movements
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524 static get steps()
525 {
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526 return {
527 'r': [ [-1,0],[1,0],[0,-1],[0,1] ],
528 'n': [ [-1,-2],[-1,2],[1,-2],[1,2],[-2,-1],[-2,1],[2,-1],[2,1] ],
529 'b': [ [-1,-1],[-1,1],[1,-1],[1,1] ],
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530 };
531 }
532
1a788978 533 ////////////////////
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534 // MOVES GENERATION
535
536 // All possible moves from selected square (assumption: color is OK)
537 getPotentialMovesFrom([x,y])
538 {
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539 switch (this.getPiece(x,y))
540 {
0b7d99ec 541 case V.PAWN:
46302e64 542 return this.getPotentialPawnMoves([x,y]);
0b7d99ec 543 case V.ROOK:
46302e64 544 return this.getPotentialRookMoves([x,y]);
0b7d99ec 545 case V.KNIGHT:
46302e64 546 return this.getPotentialKnightMoves([x,y]);
0b7d99ec 547 case V.BISHOP:
46302e64 548 return this.getPotentialBishopMoves([x,y]);
0b7d99ec 549 case V.QUEEN:
46302e64 550 return this.getPotentialQueenMoves([x,y]);
0b7d99ec 551 case V.KING:
46302e64 552 return this.getPotentialKingMoves([x,y]);
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553 }
554 }
555
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556 // Build a regular move from its initial and destination squares.
557 // tr: transformation
46302e64 558 getBasicMove([sx,sy], [ex,ey], tr)
1d184b4c 559 {
2526c041 560 let mv = new Move({
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561 appear: [
562 new PiPo({
563 x: ex,
564 y: ey,
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565 c: !!tr ? tr.c : this.getColor(sx,sy),
566 p: !!tr ? tr.p : this.getPiece(sx,sy)
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567 })
568 ],
569 vanish: [
570 new PiPo({
571 x: sx,
572 y: sy,
573 c: this.getColor(sx,sy),
574 p: this.getPiece(sx,sy)
575 })
576 ]
577 });
578
579 // The opponent piece disappears if we take it
0b7d99ec 580 if (this.board[ex][ey] != V.EMPTY)
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581 {
582 mv.vanish.push(
583 new PiPo({
584 x: ex,
585 y: ey,
586 c: this.getColor(ex,ey),
587 p: this.getPiece(ex,ey)
588 })
589 );
590 }
591 return mv;
592 }
593
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594 // Generic method to find possible moves of non-pawn pieces:
595 // "sliding or jumping"
46302e64 596 getSlideNJumpMoves([x,y], steps, oneStep)
1d184b4c 597 {
46302e64 598 const color = this.getColor(x,y);
2526c041 599 let moves = [];
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600 outerLoop:
601 for (let step of steps)
602 {
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603 let i = x + step[0];
604 let j = y + step[1];
0b7d99ec 605 while (V.OnBoard(i,j) && this.board[i][j] == V.EMPTY)
1d184b4c 606 {
46302e64 607 moves.push(this.getBasicMove([x,y], [i,j]));
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608 if (oneStep !== undefined)
609 continue outerLoop;
610 i += step[0];
611 j += step[1];
612 }
0b7d99ec 613 if (V.OnBoard(i,j) && this.canTake([x,y], [i,j]))
46302e64 614 moves.push(this.getBasicMove([x,y], [i,j]));
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615 }
616 return moves;
617 }
618
dda21a71 619 // What are the pawn moves from square x,y ?
46302e64 620 getPotentialPawnMoves([x,y])
1d184b4c 621 {
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622 const color = this.turn;
623 let moves = [];
0b7d99ec 624 const [sizeX,sizeY] = [V.size.x,V.size.y];
375ecdd1 625 const shiftX = (color == "w" ? -1 : 1);
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626 const firstRank = (color == 'w' ? sizeX-1 : 0);
627 const startRank = (color == "w" ? sizeX-2 : 1);
628 const lastRank = (color == "w" ? 0 : sizeX-1);
375ecdd1 629 const pawnColor = this.getColor(x,y); //can be different for checkered
1d184b4c 630
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631 // NOTE: next condition is generally true (no pawn on last rank)
632 if (x+shiftX >= 0 && x+shiftX < sizeX)
1d184b4c 633 {
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634 const finalPieces = x + shiftX == lastRank
635 ? [V.ROOK,V.KNIGHT,V.BISHOP,V.QUEEN]
636 : [V.PAWN]
637 // One square forward
638 if (this.board[x+shiftX][y] == V.EMPTY)
1d184b4c 639 {
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640 for (let piece of finalPieces)
641 {
642 moves.push(this.getBasicMove([x,y], [x+shiftX,y],
643 {c:pawnColor,p:piece}));
644 }
645 // Next condition because pawns on 1st rank can generally jump
646 if ([startRank,firstRank].includes(x)
647 && this.board[x+2*shiftX][y] == V.EMPTY)
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648 {
649 // Two squares jump
375ecdd1 650 moves.push(this.getBasicMove([x,y], [x+2*shiftX,y]));
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651 }
652 }
653 // Captures
375ecdd1 654 for (let shiftY of [-1,1])
1221ac47 655 {
375ecdd1
BA
656 if (y + shiftY >= 0 && y + shiftY < sizeY
657 && this.board[x+shiftX][y+shiftY] != V.EMPTY
658 && this.canTake([x,y], [x+shiftX,y+shiftY]))
1221ac47 659 {
375ecdd1
BA
660 for (let piece of finalPieces)
661 {
662 moves.push(this.getBasicMove([x,y], [x+shiftX,y+shiftY],
663 {c:pawnColor,p:piece}));
664 }
1221ac47 665 }
375ecdd1 666 }
1d184b4c
BA
667 }
668
375ecdd1 669 if (V.HasEnpassant)
1d184b4c 670 {
375ecdd1
BA
671 // En passant
672 const Lep = this.epSquares.length;
673 const epSquare = this.epSquares[Lep-1]; //always at least one element
674 if (!!epSquare && epSquare.x == x+shiftX && Math.abs(epSquare.y - y) == 1)
675 {
676 let enpassantMove = this.getBasicMove([x,y], [epSquare.x,epSquare.y]);
677 enpassantMove.vanish.push({
678 x: x,
679 y: epSquare.y,
680 p: 'p',
681 c: this.getColor(x,epSquare.y)
682 });
683 moves.push(enpassantMove);
684 }
1d184b4c
BA
685 }
686
687 return moves;
688 }
689
690 // What are the rook moves from square x,y ?
46302e64 691 getPotentialRookMoves(sq)
1d184b4c 692 {
0b7d99ec 693 return this.getSlideNJumpMoves(sq, V.steps[V.ROOK]);
1d184b4c
BA
694 }
695
696 // What are the knight moves from square x,y ?
46302e64 697 getPotentialKnightMoves(sq)
1d184b4c 698 {
0b7d99ec 699 return this.getSlideNJumpMoves(sq, V.steps[V.KNIGHT], "oneStep");
1d184b4c
BA
700 }
701
702 // What are the bishop moves from square x,y ?
46302e64 703 getPotentialBishopMoves(sq)
1d184b4c 704 {
0b7d99ec 705 return this.getSlideNJumpMoves(sq, V.steps[V.BISHOP]);
1d184b4c
BA
706 }
707
708 // What are the queen moves from square x,y ?
46302e64 709 getPotentialQueenMoves(sq)
1d184b4c 710 {
26c1e3bd
BA
711 return this.getSlideNJumpMoves(sq,
712 V.steps[V.ROOK].concat(V.steps[V.BISHOP]));
1d184b4c
BA
713 }
714
715 // What are the king moves from square x,y ?
46302e64 716 getPotentialKingMoves(sq)
1d184b4c
BA
717 {
718 // Initialize with normal moves
a37076f1
BA
719 let moves = this.getSlideNJumpMoves(sq,
720 V.steps[V.ROOK].concat(V.steps[V.BISHOP]), "oneStep");
46302e64 721 return moves.concat(this.getCastleMoves(sq));
1d184b4c
BA
722 }
723
46302e64 724 getCastleMoves([x,y])
1d184b4c 725 {
46302e64 726 const c = this.getColor(x,y);
0b7d99ec 727 if (x != (c=="w" ? V.size.x-1 : 0) || y != this.INIT_COL_KING[c])
1d184b4c
BA
728 return []; //x isn't first rank, or king has moved (shortcut)
729
1d184b4c
BA
730 // Castling ?
731 const oppCol = this.getOppCol(c);
732 let moves = [];
733 let i = 0;
0b7d99ec 734 const finalSquares = [ [2,3], [V.size.y-2,V.size.y-3] ]; //king, then rook
1d184b4c
BA
735 castlingCheck:
736 for (let castleSide=0; castleSide < 2; castleSide++) //large, then small
737 {
2526c041 738 if (!this.castleFlags[c][castleSide])
1d184b4c
BA
739 continue;
740 // If this code is reached, rooks and king are on initial position
741
26c1e3bd
BA
742 // Nothing on the path of the king ?
743 // (And no checks; OK also if y==finalSquare)
1d184b4c
BA
744 let step = finalSquares[castleSide][0] < y ? -1 : 1;
745 for (i=y; i!=finalSquares[castleSide][0]; i+=step)
746 {
cf130369 747 if (this.isAttacked([x,i], [oppCol]) || (this.board[x][i] != V.EMPTY &&
1d184b4c 748 // NOTE: next check is enough, because of chessboard constraints
26c1e3bd
BA
749 (this.getColor(x,i) != c
750 || ![V.KING,V.ROOK].includes(this.getPiece(x,i)))))
1d184b4c
BA
751 {
752 continue castlingCheck;
753 }
754 }
755
756 // Nothing on the path to the rook?
757 step = castleSide == 0 ? -1 : 1;
758 for (i = y + step; i != this.INIT_COL_ROOK[c][castleSide]; i += step)
759 {
760 if (this.board[x][i] != V.EMPTY)
761 continue castlingCheck;
762 }
763 const rookPos = this.INIT_COL_ROOK[c][castleSide];
764
765 // Nothing on final squares, except maybe king and castling rook?
766 for (i=0; i<2; i++)
767 {
768 if (this.board[x][finalSquares[castleSide][i]] != V.EMPTY &&
769 this.getPiece(x,finalSquares[castleSide][i]) != V.KING &&
770 finalSquares[castleSide][i] != rookPos)
771 {
772 continue castlingCheck;
773 }
774 }
775
776 // If this code is reached, castle is valid
777 moves.push( new Move({
778 appear: [
779 new PiPo({x:x,y:finalSquares[castleSide][0],p:V.KING,c:c}),
780 new PiPo({x:x,y:finalSquares[castleSide][1],p:V.ROOK,c:c})],
781 vanish: [
782 new PiPo({x:x,y:y,p:V.KING,c:c}),
783 new PiPo({x:x,y:rookPos,p:V.ROOK,c:c})],
784 end: Math.abs(y - rookPos) <= 2
785 ? {x:x, y:rookPos}
786 : {x:x, y:y + 2 * (castleSide==0 ? -1 : 1)}
787 }) );
788 }
789
790 return moves;
791 }
792
1a788978 793 ////////////////////
1d184b4c
BA
794 // MOVES VALIDATION
795
f6dbe8e3 796 // For the interface: possible moves for the current turn from square sq
1d184b4c
BA
797 getPossibleMovesFrom(sq)
798 {
1d184b4c
BA
799 return this.filterValid( this.getPotentialMovesFrom(sq) );
800 }
801
92342261 802 // TODO: promotions (into R,B,N,Q) should be filtered only once
1d184b4c
BA
803 filterValid(moves)
804 {
805 if (moves.length == 0)
806 return [];
f6dbe8e3
BA
807 const color = this.turn;
808 return moves.filter(m => {
809 this.play(m);
810 const res = !this.underCheck(color);
811 this.undo(m);
812 return res;
813 });
1d184b4c
BA
814 }
815
26c1e3bd
BA
816 // Search for all valid moves considering current turn
817 // (for engine and game end)
46302e64 818 getAllValidMoves()
1d184b4c 819 {
46302e64 820 const color = this.turn;
1d184b4c 821 const oppCol = this.getOppCol(color);
c6052161 822 let potentialMoves = [];
0b7d99ec 823 for (let i=0; i<V.size.x; i++)
1d184b4c 824 {
0b7d99ec 825 for (let j=0; j<V.size.y; j++)
1d184b4c 826 {
26c1e3bd 827 // Next condition "!= oppCol" to work with checkered variant
0b7d99ec 828 if (this.board[i][j] != V.EMPTY && this.getColor(i,j) != oppCol)
26c1e3bd
BA
829 {
830 Array.prototype.push.apply(potentialMoves,
831 this.getPotentialMovesFrom([i,j]));
832 }
1d184b4c
BA
833 }
834 }
1d184b4c
BA
835 return this.filterValid(potentialMoves);
836 }
9de73b71 837
e64a4eff 838 // Stop at the first move found
46302e64 839 atLeastOneMove()
e64a4eff 840 {
46302e64 841 const color = this.turn;
e64a4eff 842 const oppCol = this.getOppCol(color);
0b7d99ec 843 for (let i=0; i<V.size.x; i++)
e64a4eff 844 {
0b7d99ec 845 for (let j=0; j<V.size.y; j++)
e64a4eff 846 {
0b7d99ec 847 if (this.board[i][j] != V.EMPTY && this.getColor(i,j) != oppCol)
e64a4eff
BA
848 {
849 const moves = this.getPotentialMovesFrom([i,j]);
850 if (moves.length > 0)
851 {
9de73b71 852 for (let k=0; k<moves.length; k++)
e64a4eff 853 {
9de73b71 854 if (this.filterValid([moves[k]]).length > 0)
e64a4eff
BA
855 return true;
856 }
857 }
858 }
859 }
860 }
861 return false;
862 }
1d184b4c 863
26c1e3bd 864 // Check if pieces of color in 'colors' are attacking (king) on square x,y
46302e64 865 isAttacked(sq, colors)
1d184b4c 866 {
46302e64
BA
867 return (this.isAttackedByPawn(sq, colors)
868 || this.isAttackedByRook(sq, colors)
869 || this.isAttackedByKnight(sq, colors)
870 || this.isAttackedByBishop(sq, colors)
871 || this.isAttackedByQueen(sq, colors)
872 || this.isAttackedByKing(sq, colors));
1d184b4c
BA
873 }
874
dda21a71 875 // Is square x,y attacked by 'colors' pawns ?
46302e64 876 isAttackedByPawn([x,y], colors)
1d184b4c 877 {
46302e64 878 for (let c of colors)
1d184b4c 879 {
46302e64 880 let pawnShift = (c=="w" ? 1 : -1);
0b7d99ec 881 if (x+pawnShift>=0 && x+pawnShift<V.size.x)
1d184b4c 882 {
46302e64 883 for (let i of [-1,1])
1d184b4c 884 {
0b7d99ec 885 if (y+i>=0 && y+i<V.size.y && this.getPiece(x+pawnShift,y+i)==V.PAWN
46302e64
BA
886 && this.getColor(x+pawnShift,y+i)==c)
887 {
888 return true;
889 }
1d184b4c
BA
890 }
891 }
892 }
893 return false;
894 }
895
dda21a71 896 // Is square x,y attacked by 'colors' rooks ?
46302e64 897 isAttackedByRook(sq, colors)
1d184b4c 898 {
0b7d99ec 899 return this.isAttackedBySlideNJump(sq, colors, V.ROOK, V.steps[V.ROOK]);
1d184b4c
BA
900 }
901
dda21a71 902 // Is square x,y attacked by 'colors' knights ?
46302e64 903 isAttackedByKnight(sq, colors)
1d184b4c 904 {
46302e64 905 return this.isAttackedBySlideNJump(sq, colors,
0b7d99ec 906 V.KNIGHT, V.steps[V.KNIGHT], "oneStep");
1d184b4c
BA
907 }
908
dda21a71 909 // Is square x,y attacked by 'colors' bishops ?
46302e64 910 isAttackedByBishop(sq, colors)
1d184b4c 911 {
0b7d99ec 912 return this.isAttackedBySlideNJump(sq, colors, V.BISHOP, V.steps[V.BISHOP]);
1d184b4c
BA
913 }
914
dda21a71 915 // Is square x,y attacked by 'colors' queens ?
46302e64 916 isAttackedByQueen(sq, colors)
1d184b4c 917 {
a37076f1
BA
918 return this.isAttackedBySlideNJump(sq, colors, V.QUEEN,
919 V.steps[V.ROOK].concat(V.steps[V.BISHOP]));
1d184b4c
BA
920 }
921
dda21a71 922 // Is square x,y attacked by 'colors' king(s) ?
46302e64 923 isAttackedByKing(sq, colors)
1d184b4c 924 {
a37076f1
BA
925 return this.isAttackedBySlideNJump(sq, colors, V.KING,
926 V.steps[V.ROOK].concat(V.steps[V.BISHOP]), "oneStep");
1d184b4c
BA
927 }
928
1221ac47 929 // Generic method for non-pawn pieces ("sliding or jumping"):
dda21a71 930 // is x,y attacked by a piece of color in array 'colors' ?
46302e64 931 isAttackedBySlideNJump([x,y], colors, piece, steps, oneStep)
1d184b4c
BA
932 {
933 for (let step of steps)
934 {
935 let rx = x+step[0], ry = y+step[1];
0b7d99ec 936 while (V.OnBoard(rx,ry) && this.board[rx][ry] == V.EMPTY && !oneStep)
1d184b4c
BA
937 {
938 rx += step[0];
939 ry += step[1];
940 }
0b7d99ec
BA
941 if (V.OnBoard(rx,ry) && this.getPiece(rx,ry) === piece
942 && colors.includes(this.getColor(rx,ry)))
1d184b4c
BA
943 {
944 return true;
945 }
946 }
947 return false;
948 }
949
f6dbe8e3
BA
950 // Is color under check after his move ?
951 underCheck(color)
1d184b4c 952 {
f6dbe8e3 953 return this.isAttacked(this.kingPos[color], [this.getOppCol(color)]);
1d184b4c
BA
954 }
955
1a788978
BA
956 /////////////////
957 // MOVES PLAYING
4b5fe306 958
1d184b4c
BA
959 // Apply a move on board
960 static PlayOnBoard(board, move)
961 {
962 for (let psq of move.vanish)
0b7d99ec 963 board[psq.x][psq.y] = V.EMPTY;
1d184b4c
BA
964 for (let psq of move.appear)
965 board[psq.x][psq.y] = psq.c + psq.p;
966 }
967 // Un-apply the played move
968 static UndoOnBoard(board, move)
969 {
970 for (let psq of move.appear)
0b7d99ec 971 board[psq.x][psq.y] = V.EMPTY;
1d184b4c
BA
972 for (let psq of move.vanish)
973 board[psq.x][psq.y] = psq.c + psq.p;
974 }
975
4f7723a1 976 // After move is played, update variables + flags
1d184b4c
BA
977 updateVariables(move)
978 {
dbcc32e9
BA
979 let piece = undefined;
980 let c = undefined;
981 if (move.vanish.length >= 1)
982 {
983 // Usual case, something is moved
984 piece = move.vanish[0].p;
985 c = move.vanish[0].c;
986 }
987 else
988 {
989 // Crazyhouse-like variants
990 piece = move.appear[0].p;
991 c = move.appear[0].c;
992 }
6e62b1c7
BA
993 if (c == "c") //if (!["w","b"].includes(c))
994 {
995 // 'c = move.vanish[0].c' doesn't work for Checkered
996 c = this.getOppCol(this.turn);
997 }
0b7d99ec 998 const firstRank = (c == "w" ? V.size.x-1 : 0);
1d184b4c
BA
999
1000 // Update king position + flags
0b7d99ec 1001 if (piece == V.KING && move.appear.length > 0)
1d184b4c
BA
1002 {
1003 this.kingPos[c][0] = move.appear[0].x;
1004 this.kingPos[c][1] = move.appear[0].y;
69f3d801
BA
1005 if (V.HasFlags)
1006 this.castleFlags[c] = [false,false];
1d184b4c
BA
1007 return;
1008 }
69f3d801 1009 if (V.HasFlags)
1d184b4c 1010 {
69f3d801
BA
1011 // Update castling flags if rooks are moved
1012 const oppCol = this.getOppCol(c);
1013 const oppFirstRank = (V.size.x-1) - firstRank;
1014 if (move.start.x == firstRank //our rook moves?
1015 && this.INIT_COL_ROOK[c].includes(move.start.y))
1016 {
1017 const flagIdx = (move.start.y == this.INIT_COL_ROOK[c][0] ? 0 : 1);
1018 this.castleFlags[c][flagIdx] = false;
1019 }
1020 else if (move.end.x == oppFirstRank //we took opponent rook?
1021 && this.INIT_COL_ROOK[oppCol].includes(move.end.y))
1022 {
1023 const flagIdx = (move.end.y == this.INIT_COL_ROOK[oppCol][0] ? 0 : 1);
1024 this.castleFlags[oppCol][flagIdx] = false;
1025 }
1d184b4c
BA
1026 }
1027 }
1028
1a788978
BA
1029 // After move is undo-ed *and flags resetted*, un-update other variables
1030 // TODO: more symmetry, by storing flags increment in move (?!)
d3334c3a 1031 unupdateVariables(move)
1d184b4c 1032 {
d3334c3a
BA
1033 // (Potentially) Reset king position
1034 const c = this.getColor(move.start.x,move.start.y);
0b7d99ec 1035 if (this.getPiece(move.start.x,move.start.y) == V.KING)
d3334c3a
BA
1036 this.kingPos[c] = [move.start.x, move.start.y];
1037 }
1d184b4c 1038
d3334c3a
BA
1039 play(move, ingame)
1040 {
a3c86ec9
BA
1041 // DEBUG:
1042// if (!this.states) this.states = [];
1a788978 1043// if (!ingame) this.states.push(this.getFen());
a3c86ec9 1044
dfb4afc1 1045 if (!!ingame)
6752407b 1046 move.notation = [this.getNotation(move), this.getLongNotation(move)];
dfb4afc1 1047
2d7194bd
BA
1048 if (V.HasFlags)
1049 move.flags = JSON.stringify(this.aggregateFlags()); //save flags (for undo)
2d7194bd
BA
1050 if (V.HasEnpassant)
1051 this.epSquares.push( this.getEpSquare(move) );
0b7d99ec 1052 V.PlayOnBoard(this.board, move);
388e4c40
BA
1053 this.turn = this.getOppCol(this.turn);
1054 this.moves.push(move);
1055 this.updateVariables(move);
331fc58c
BA
1056
1057 if (!!ingame)
1a788978
BA
1058 {
1059 // Hash of current game state *after move*, to detect repetitions
45109880 1060 move.hash = hex_md5(this.getFen());
1a788978 1061 }
1d184b4c
BA
1062 }
1063
cd4cad04 1064 undo(move)
1d184b4c 1065 {
2d7194bd
BA
1066 if (V.HasEnpassant)
1067 this.epSquares.pop();
2d7194bd
BA
1068 if (V.HasFlags)
1069 this.disaggregateFlags(JSON.parse(move.flags));
388e4c40
BA
1070 V.UndoOnBoard(this.board, move);
1071 this.turn = this.getOppCol(this.turn);
1072 this.moves.pop();
1073 this.unupdateVariables(move);
a3c86ec9
BA
1074
1075 // DEBUG:
1a788978 1076// if (this.getFen() != this.states[this.states.length-1])
a3c86ec9
BA
1077// debugger;
1078// this.states.pop();
1d184b4c
BA
1079 }
1080
1a788978 1081 ///////////////
1d184b4c
BA
1082 // END OF GAME
1083
331fc58c 1084 // Check for 3 repetitions (position + flags + turn)
1af36beb 1085 checkRepetition()
1d184b4c 1086 {
15c1295a
BA
1087 if (!this.hashStates)
1088 this.hashStates = {};
1089 const startIndex =
1090 Object.values(this.hashStates).reduce((a,b) => { return a+b; }, 0)
1091 // Update this.hashStates with last move (or all moves if continuation)
1092 // NOTE: redundant storage, but faster and moderate size
1093 for (let i=startIndex; i<this.moves.length; i++)
1094 {
1095 const move = this.moves[i];
1096 if (!this.hashStates[move.hash])
1097 this.hashStates[move.hash] = 1;
1098 else
1099 this.hashStates[move.hash]++;
1100 }
331fc58c 1101 return Object.values(this.hashStates).some(elt => { return (elt >= 3); });
1af36beb 1102 }
1d184b4c 1103
dda21a71 1104 // Is game over ? And if yes, what is the score ?
1af36beb
BA
1105 checkGameOver()
1106 {
1107 if (this.checkRepetition())
1108 return "1/2";
1109
1110 if (this.atLeastOneMove()) // game not over
1d184b4c 1111 return "*";
1d184b4c
BA
1112
1113 // Game over
46302e64 1114 return this.checkGameEnd();
1d184b4c
BA
1115 }
1116
46302e64
BA
1117 // No moves are possible: compute score
1118 checkGameEnd()
1d184b4c 1119 {
46302e64 1120 const color = this.turn;
1d184b4c 1121 // No valid move: stalemate or checkmate?
cf130369 1122 if (!this.isAttacked(this.kingPos[color], [this.getOppCol(color)]))
1d184b4c
BA
1123 return "1/2";
1124 // OK, checkmate
6e62b1c7 1125 return (color == "w" ? "0-1" : "1-0");
1d184b4c
BA
1126 }
1127
1a788978
BA
1128 ///////////////
1129 // ENGINE PLAY
1d184b4c
BA
1130
1131 // Pieces values
1a788978
BA
1132 static get VALUES()
1133 {
1d184b4c
BA
1134 return {
1135 'p': 1,
1136 'r': 5,
1137 'n': 3,
1138 'b': 3,
1139 'q': 9,
1140 'k': 1000
1141 };
1142 }
1143
1a788978
BA
1144 // "Checkmate" (unreachable eval)
1145 static get INFINITY() { return 9999; }
9e42b4dd 1146
1a788978
BA
1147 // At this value or above, the game is over
1148 static get THRESHOLD_MATE() { return V.INFINITY; }
9e42b4dd 1149
1a788978
BA
1150 // Search depth: 2 for high branching factor, 4 for small (Loser chess, eg.)
1151 static get SEARCH_DEPTH() { return 3; }
3c09dc49 1152
1d184b4c 1153 // Assumption: at least one legal move
a6abf094
BA
1154 // NOTE: works also for extinction chess because depth is 3...
1155 getComputerMove()
1d184b4c 1156 {
0b7d99ec 1157 const maxeval = V.INFINITY;
46302e64 1158 const color = this.turn;
15952ada
BA
1159 // Some variants may show a bigger moves list to the human (Switching),
1160 // thus the argument "computer" below (which is generally ignored)
1161 let moves1 = this.getAllValidMoves("computer");
a6abf094
BA
1162
1163 // Can I mate in 1 ? (for Magnetic & Extinction)
1164 for (let i of _.shuffle(_.range(moves1.length)))
1165 {
1166 this.play(moves1[i]);
0b7d99ec
BA
1167 let finish = (Math.abs(this.evalPosition()) >= V.THRESHOLD_MATE);
1168 if (!finish && !this.atLeastOneMove())
1169 {
1a788978 1170 // Test mate (for other variants)
0b7d99ec
BA
1171 const score = this.checkGameEnd();
1172 if (score != "1/2")
1173 finish = true;
1174 }
a6abf094
BA
1175 this.undo(moves1[i]);
1176 if (finish)
1177 return moves1[i];
1178 }
1d184b4c 1179
06ddfe34 1180 // Rank moves using a min-max at depth 2
1d184b4c
BA
1181 for (let i=0; i<moves1.length; i++)
1182 {
26c1e3bd
BA
1183 // Initial self evaluation is very low: "I'm checkmated"
1184 moves1[i].eval = (color=="w" ? -1 : 1) * maxeval;
1d184b4c 1185 this.play(moves1[i]);
68f5ccc8
BA
1186 let eval2 = undefined;
1187 if (this.atLeastOneMove())
1d184b4c 1188 {
26c1e3bd
BA
1189 // Initial enemy evaluation is very low too, for him
1190 eval2 = (color=="w" ? 1 : -1) * maxeval;
68f5ccc8 1191 // Second half-move:
15952ada 1192 let moves2 = this.getAllValidMoves("computer");
68f5ccc8
BA
1193 for (let j=0; j<moves2.length; j++)
1194 {
1195 this.play(moves2[j]);
1196 let evalPos = undefined;
1197 if (this.atLeastOneMove())
1198 evalPos = this.evalPosition()
1199 else
1200 {
1a788978 1201 // Working with scores is more accurate (necessary for Loser variant)
68f5ccc8
BA
1202 const score = this.checkGameEnd();
1203 evalPos = (score=="1/2" ? 0 : (score=="1-0" ? 1 : -1) * maxeval);
1204 }
26c1e3bd
BA
1205 if ((color == "w" && evalPos < eval2)
1206 || (color=="b" && evalPos > eval2))
1207 {
68f5ccc8 1208 eval2 = evalPos;
26c1e3bd 1209 }
68f5ccc8
BA
1210 this.undo(moves2[j]);
1211 }
1212 }
1213 else
1214 {
1215 const score = this.checkGameEnd();
1216 eval2 = (score=="1/2" ? 0 : (score=="1-0" ? 1 : -1) * maxeval);
1d184b4c 1217 }
92342261
BA
1218 if ((color=="w" && eval2 > moves1[i].eval)
1219 || (color=="b" && eval2 < moves1[i].eval))
1220 {
1d184b4c 1221 moves1[i].eval = eval2;
92342261 1222 }
1d184b4c
BA
1223 this.undo(moves1[i]);
1224 }
1225 moves1.sort( (a,b) => { return (color=="w" ? 1 : -1) * (b.eval - a.eval); });
1226
3c09dc49
BA
1227 let candidates = [0]; //indices of candidates moves
1228 for (let j=1; j<moves1.length && moves1[j].eval == moves1[0].eval; j++)
1229 candidates.push(j);
1230 let currentBest = moves1[_.sample(candidates, 1)];
1231
e82cd979
BA
1232 // From here, depth >= 3: may take a while, so we control time
1233 const timeStart = Date.now();
1234
a6abf094 1235 // Skip depth 3+ if we found a checkmate (or if we are checkmated in 1...)
0b7d99ec 1236 if (V.SEARCH_DEPTH >= 3 && Math.abs(moves1[0].eval) < V.THRESHOLD_MATE)
e64a4eff 1237 {
9e42b4dd
BA
1238 for (let i=0; i<moves1.length; i++)
1239 {
e82cd979
BA
1240 if (Date.now()-timeStart >= 5000) //more than 5 seconds
1241 return currentBest; //depth 2 at least
9e42b4dd
BA
1242 this.play(moves1[i]);
1243 // 0.1 * oldEval : heuristic to avoid some bad moves (not all...)
3c09dc49 1244 moves1[i].eval = 0.1*moves1[i].eval +
0b7d99ec 1245 this.alphabeta(V.SEARCH_DEPTH-1, -maxeval, maxeval);
9e42b4dd
BA
1246 this.undo(moves1[i]);
1247 }
26c1e3bd
BA
1248 moves1.sort( (a,b) => {
1249 return (color=="w" ? 1 : -1) * (b.eval - a.eval); });
e64a4eff 1250 }
3c09dc49
BA
1251 else
1252 return currentBest;
69f3d801 1253// console.log(moves1.map(m => { return [this.getNotation(m), m.eval]; }));
1d184b4c 1254
3c09dc49 1255 candidates = [0];
1d184b4c
BA
1256 for (let j=1; j<moves1.length && moves1[j].eval == moves1[0].eval; j++)
1257 candidates.push(j);
1d184b4c
BA
1258 return moves1[_.sample(candidates, 1)];
1259 }
1260
46302e64 1261 alphabeta(depth, alpha, beta)
1d184b4c 1262 {
0b7d99ec 1263 const maxeval = V.INFINITY;
46302e64
BA
1264 const color = this.turn;
1265 if (!this.atLeastOneMove())
1d184b4c 1266 {
46302e64 1267 switch (this.checkGameEnd())
1d184b4c 1268 {
68f5ccc8
BA
1269 case "1/2":
1270 return 0;
1271 default:
1272 const score = this.checkGameEnd();
1273 return (score=="1/2" ? 0 : (score=="1-0" ? 1 : -1) * maxeval);
1d184b4c
BA
1274 }
1275 }
1276 if (depth == 0)
1277 return this.evalPosition();
15952ada 1278 const moves = this.getAllValidMoves("computer");
9e42b4dd 1279 let v = color=="w" ? -maxeval : maxeval;
1d184b4c
BA
1280 if (color == "w")
1281 {
1282 for (let i=0; i<moves.length; i++)
1283 {
1284 this.play(moves[i]);
46302e64 1285 v = Math.max(v, this.alphabeta(depth-1, alpha, beta));
1d184b4c
BA
1286 this.undo(moves[i]);
1287 alpha = Math.max(alpha, v);
1288 if (alpha >= beta)
1289 break; //beta cutoff
1290 }
1291 }
1292 else //color=="b"
1293 {
1294 for (let i=0; i<moves.length; i++)
1295 {
1296 this.play(moves[i]);
46302e64 1297 v = Math.min(v, this.alphabeta(depth-1, alpha, beta));
1d184b4c
BA
1298 this.undo(moves[i]);
1299 beta = Math.min(beta, v);
1300 if (alpha >= beta)
1301 break; //alpha cutoff
1302 }
1303 }
1304 return v;
1305 }
1306
1307 evalPosition()
1308 {
1d184b4c 1309 let evaluation = 0;
a6abf094 1310 // Just count material for now
0b7d99ec 1311 for (let i=0; i<V.size.x; i++)
1d184b4c 1312 {
0b7d99ec 1313 for (let j=0; j<V.size.y; j++)
1d184b4c 1314 {
0b7d99ec 1315 if (this.board[i][j] != V.EMPTY)
1d184b4c
BA
1316 {
1317 const sign = this.getColor(i,j) == "w" ? 1 : -1;
0b7d99ec 1318 evaluation += sign * V.VALUES[this.getPiece(i,j)];
1d184b4c
BA
1319 }
1320 }
1321 }
1322 return evaluation;
1323 }
1324
1a788978
BA
1325 /////////////////////////
1326 // MOVES + GAME NOTATION
1327 /////////////////////////
1d184b4c
BA
1328
1329 // Context: just before move is played, turn hasn't changed
1330 getNotation(move)
1331 {
0b7d99ec 1332 if (move.appear.length == 2 && move.appear[0].p == V.KING) //castle
15952ada 1333 return (move.end.y < move.start.y ? "0-0-0" : "0-0");
1d184b4c
BA
1334
1335 // Translate final square
1a788978 1336 const finalSquare = V.CoordsToSquare(move.end);
1d184b4c 1337
270968d6 1338 const piece = this.getPiece(move.start.x, move.start.y);
0b7d99ec 1339 if (piece == V.PAWN)
1d184b4c
BA
1340 {
1341 // Pawn move
1342 let notation = "";
5bfb0956 1343 if (move.vanish.length > move.appear.length)
1d184b4c
BA
1344 {
1345 // Capture
26c1e3bd 1346 const startColumn = V.CoordToColumn(move.start.y);
1d184b4c
BA
1347 notation = startColumn + "x" + finalSquare;
1348 }
1349 else //no capture
1350 notation = finalSquare;
26c1e3bd 1351 if (move.appear.length > 0 && move.appear[0].p != V.PAWN) //promotion
1d184b4c
BA
1352 notation += "=" + move.appear[0].p.toUpperCase();
1353 return notation;
1354 }
1355
1356 else
1357 {
1358 // Piece movement
f3c10e18
BA
1359 return piece.toUpperCase() +
1360 (move.vanish.length > move.appear.length ? "x" : "") + finalSquare;
1d184b4c
BA
1361 }
1362 }
dfb4afc1 1363
6752407b
BA
1364 // Complete the usual notation, may be required for de-ambiguification
1365 getLongNotation(move)
1366 {
1a788978
BA
1367 // Not encoding move. But short+long is enough
1368 return V.CoordsToSquare(move.start) + V.CoordsToSquare(move.end);
6752407b
BA
1369 }
1370
dfb4afc1 1371 // The score is already computed when calling this function
01a135e2 1372 getPGN(mycolor, score, fenStart, mode)
dfb4afc1
BA
1373 {
1374 let pgn = "";
1375 pgn += '[Site "vchess.club"]<br>';
5e622704 1376 const opponent = mode=="human" ? "Anonymous" : "Computer";
0f51ef98 1377 pgn += '[Variant "' + variant + '"]<br>';
c794dbb8 1378 pgn += '[Date "' + getDate(new Date()) + '"]<br>';
01a135e2
BA
1379 pgn += '[White "' + (mycolor=='w'?'Myself':opponent) + '"]<br>';
1380 pgn += '[Black "' + (mycolor=='b'?'Myself':opponent) + '"]<br>';
04449c97
BA
1381 pgn += '[FenStart "' + fenStart + '"]<br>';
1382 pgn += '[Fen "' + this.getFen() + '"]<br>';
762b7c9c 1383 pgn += '[Result "' + score + '"]<br><br>';
dfb4afc1 1384
6752407b 1385 // Standard PGN
dfb4afc1
BA
1386 for (let i=0; i<this.moves.length; i++)
1387 {
1388 if (i % 2 == 0)
1389 pgn += ((i/2)+1) + ".";
6752407b 1390 pgn += this.moves[i].notation[0] + " ";
dfb4afc1 1391 }
97fc8bf7 1392 pgn += "<br><br>";
dfb4afc1 1393
6752407b
BA
1394 // "Complete moves" PGN (helping in ambiguous cases)
1395 for (let i=0; i<this.moves.length; i++)
1396 {
1397 if (i % 2 == 0)
1398 pgn += ((i/2)+1) + ".";
1399 pgn += this.moves[i].notation[1] + " ";
1400 }
6752407b 1401
dfb4afc1
BA
1402 return pgn;
1403 }
1d184b4c 1404}