git.sesse.net Git - remoteglot-book/blob - www/js/book.js

   1 (function() {
   2
   3 var board = null;
   4 var game = new Chess();
   5 var fens = [];  // Position after each.
   6 var move_override = 0;
   7 var includetransp = true;
   8 var stockfish = new Worker('/js/stockfish.js');
   9 var engine_running = false;
  10 var engine_replacement_callback = null;
  11 var recommended_move = null;
  12 var reverse_dragging_from = null;
  13 var practice_mode = false;
  14 var practice_side = 'W';
  15
  16 // TODO: Make this configurable.
  17 var practice_top_moves_limit = 5;
  18 var practice_minimum_move_fraction_start = 0.05;
  19 var practice_minimum_move_fraction_move5 = 0.30;
  20
  21 var entity_map = {
  22         "&": "&amp;",
  23         "<": "&lt;",
  24         ">": "&gt;",
  25         '"': '&quot;',
  26         "'": '&#39;',
  27 };
  28
  29 function escape_html(string) {
  30         return String(string).replace(/[&<>"']/g, function (s) {
  31                 return entity_map[s];
  32         });
  33 }
  34
  35 var current_display_fen = function() {
  36         return fen_before_move(move_override);
  37 }
  38
  39 var fen_before_move = function(move_num) {
  40         if (move_num == 0) {
  41                 return 'rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1';
  42         } else {
  43                 return fens[move_num - 1];
  44         }
  45 }
  46
  47 var update = function() {
  48         var text = "";
  49         var history = game.history({ verbose: true });
  50         for (var i = 0; i < history.length; ++i) {
  51                 if (i % 2 == 0) {
  52                         text += (i/2 + 1) + ". ";
  53                 }
  54                 if (i + 1 == move_override) {
  55                         text += '<strong>' + history[i].san + '</strong>';
  56                 } else {
  57                         text += '<a href="javascript:set_move(' + (i + 1) + ')">' + history[i].san + '</a>';
  58                 }
  59                 text += " ";
  60         }
  61         $('#gamehistory').html(text);
  62
  63         if (board.fen() != current_display_fen()) {
  64                 board.position(current_display_fen());
  65         }
  66
  67         $("#board").find('.square-55d63').removeClass('nonuglyhighlight');
  68         if (move_override > 0) {
  69                 var last_move = history[move_override - 1];
  70                 var highlight_from = last_move.from;
  71                 var highlight_to = last_move.to;
  72                 $("#board").find('.square-' + highlight_from).addClass('nonuglyhighlight');
  73                 $("#board").find('.square-' + highlight_to).addClass('nonuglyhighlight');
  74         }
  75
  76         if (practice_mode) {
  77                 find_last_move_score();
  78                 var side_to_move = (move_override % 2 == 0) ? 'W' : 'B';
  79                 if (side_to_move !== practice_side) {
  80                         find_computer_move();
  81                 }
  82                 // Fall through to get the line name and such.
  83         }
  84
  85         fetch_analysis();
  86 }
  87
  88 var get_history_url = function() {
  89         var history = game.history({ verbose: true }).map(function(x) { return x.san; });
  90         history.length = move_override;
  91         return '/?' + history.join(',');
  92 }
  93
  94 var fetch_analysis = function() {
  95         var fen = current_display_fen();
  96         $.ajax({
  97                 url: "/opening-stats.pl?fen=" + encodeURIComponent(fen) +
  98                         ";includetransp=" + (includetransp ? 1 : 0)
  99         }).done(function(data, textstatus, xhr) {
 100                 show_lines(data, game);
 101         });
 102 }
 103
 104 var find_last_move_score = function() {
 105         var history = game.history({ verbose: true });
 106         var side_to_move = (move_override % 2 == 0) ? 'W' : 'B';
 107         var move_num = (side_to_move === practice_side) ? (move_override - 2) : (move_override - 1);
 108         if (move_num < 0) {
 109                 $("#yourmove").text("(none)");
 110                 $("#yourfraction").text("N/A");
 111                 $("#yourrank").text("N/A");
 112                 $("#yourawin").text("??.?%");
 113                 $("#yourawindiff").text("+?.?%");
 114                 return;
 115         }
 116
 117         var chosen_move = history[move_num].san;
 118         $("#yourmove").text(chosen_move);
 119         $.ajax({
 120                 url: "/opening-stats.pl?fen=" + encodeURIComponent(fen_before_move(move_num)) +
 121                         ";includetransp=0"
 122         }).done(function(data, textstatus, xhr) {
 123                 var moves = data['moves'];
 124                 var root_move = sort_move_by_frequency(moves, data);
 125                 var your_move, your_index;
 126
 127                 for (var i = 0; i < moves.length; ++i) {
 128                         var move = moves[i];
 129                         if (move['move'] === chosen_move) {
 130                                 your_move = move;
 131                                 your_index = i;
 132                         }
 133                 }
 134
 135                 if (your_move) {
 136                         $("#yourfraction").text(format_fraction(your_move['fraction']));
 137                         $("#yourawin").text(format_fraction(your_move['corrected_win_ratio']));
 138                         $("#yourrank").text(format_ordinal(your_index + 1) + ", based on " + root_move['num'] + " games");
 139                         var diff = your_move['corrected_win_ratio'] - root_move['corrected_win_ratio'];
 140                         $("#yourawindiff").css("color", "black");
 141                         if (diff === 0) {
 142                                 $("#yourawindiff").text("0.0%");
 143                         } else if (diff > 0) {
 144                                 $("#yourawindiff").text("+" + format_fraction(diff));
 145                                 $("#yourawindiff").css("color", "green");
 146                         } else {
 147                                 $("#yourawindiff").text(format_fraction(diff));
 148                                 if (diff < -0.02) {
 149                                         $("#yourawindiff").css("color", "red");
 150                                 }
 151                         }
 152                 } else {
 153                         $("#yourfraction").text("??.?%");
 154                         $("#yourrank").text("?th");
 155                         $("#yourawin").text("??.?%");
 156                         $("#yourawindiff").text("+?.?%");
 157                 }
 158         });
 159 }
 160
 161 var find_computer_move = function() {
 162         var fen = current_display_fen();
 163         $.ajax({
 164                 url: "/opening-stats.pl?fen=" + encodeURIComponent(fen) + ";includetransp=0"
 165         }).done(function(data, textstatus, xhr) {
 166                 var candidate_moves = [];
 167
 168                 var moves = data['moves'];
 169                 var root_move = sort_move_by_frequency(moves, data);
 170
 171                 var practice_minimum_move_fraction;
 172                 if (move_override > 20) {
 173                         practice_minimum_move_fraction = practice_minimum_move_fraction_move5;
 174                 } else {
 175                         practice_minimum_move_fraction = practice_minimum_move_fraction_start +
 176                                 ((move_override-1)/10.0) * (practice_minimum_move_fraction_move5 - practice_minimum_move_fraction_start);
 177                 }
 178                 console.log(practice_minimum_move_fraction);
 179
 180                 for (var i = 0; i < Math.min(moves.length, practice_top_moves_limit); ++i) {
 181                         var move = moves[i];
 182                         if (i == 0 || move['fraction'] >= practice_minimum_move_fraction) {
 183                                 candidate_moves.push(move);
 184                         }
 185                 }
 186
 187                 // Pick one at random.
 188                 var chosen_index = Math.floor(Math.random() * candidate_moves.length);
 189                 var chosen = candidate_moves[chosen_index];
 190                 $("#compmove").text(chosen['move']);
 191                 $("#compfraction").text((100.0 * chosen['fraction']).toFixed(1) + "%");
 192                 if (candidate_moves.length == 1) {
 193                         $("#comprank").text("only candidate move");
 194                 } else {
 195                         $("#comprank").text(format_ordinal(chosen_index + 1) + " out of " + candidate_moves.length + " candidate moves");
 196                 }
 197                 make_move(chosen['move']);
 198         });
 199 }
 200
 201 // Add deried data and then sort moves to get the most common ones (in-place).
 202 // Remove the root mode and return it. Currently usable for practice mode only!
 203 var sort_move_by_frequency = function(moves, data)
 204 {
 205         var total_num = find_total_games(moves);
 206         var root_move;
 207         for (var i = 0; i < moves.length; ++i) {
 208                 var move = moves[i];
 209                 calc_move_derived_data(move, total_num, data, (practice_side === 'W'));
 210                 if (!move['move']) {
 211                         root_move = (moves.splice(i, 1))[0];
 212                         --i;
 213                 }
 214         }
 215         moves.sort(function(a, b) { return b['num'] - a['num'] });
 216         return root_move;
 217 }
 218
 219 var add_td = function(tr, value) {
 220         var td = document.createElement("td");
 221         tr.appendChild(td);
 222         $(td).addClass("num");
 223         $(td).text(value);
 224 }
 225
 226 var format_ordinal = function(x) {
 227         var tens = Math.floor(x / 10) % 10;
 228         if (tens == 1) {
 229                 return x + "th";
 230         } else {
 231                 var ones = x % 10;
 232                 if (ones == 1) return x + "st";
 233                 if (ones == 2) return x + "nd";
 234                 if (ones == 3) return x + "rd";
 235                 return x + "th";
 236         }
 237 }
 238
 239 var format_fraction = function(x) {
 240         return (100.0 * x).toFixed(1) + '%';
 241 }
 242
 243 var TYPE_MOVE = 0;
 244 var TYPE_INTEGER = 1;
 245 var TYPE_FLOAT = 2;
 246 var TYPE_RATIO = 3;
 247
 248 var headings = [
 249         [ "Move", TYPE_MOVE ],
 250         [ "Games", TYPE_INTEGER ],
 251         [ "%", TYPE_RATIO ],
 252         [ "CGames", TYPE_INTEGER ],
 253         [ "Hum", TYPE_RATIO ],
 254         [ "Win%", TYPE_RATIO ],
 255         [ "WWin", TYPE_INTEGER ],
 256         [ "%WW", TYPE_RATIO ],
 257         [ "Bwin", TYPE_INTEGER ],
 258         [ "%BW", TYPE_RATIO ],
 259         [ "Draw", TYPE_INTEGER ],
 260         [ "Draw%", TYPE_RATIO ],
 261         [ "AvWElo", TYPE_FLOAT ],
 262         [ "AvBElo", TYPE_FLOAT ],
 263         [ "EloVar", TYPE_FLOAT ],
 264         [ "AWin%", TYPE_RATIO ],
 265 ];
 266 var sort_by = 1;
 267 var direction = 1;
 268
 269 var show_lines = function(data, game) {
 270         var moves = data['moves'];
 271         $('#numviewers').text(data['opening']);
 272
 273         if (data['root_game']) {
 274                 var text = escape_html(data['root_game']['white']);
 275                 if (data['root_game']['white_elo']) {
 276                         text += " (" + escape_html(data['root_game']['white_elo']) + ")";
 277                 }
 278                 text += " &ndash; " + escape_html(data['root_game']['black']);
 279                 if (data['root_game']['black_elo']) {
 280                         text += " (" + escape_html(data['root_game']['black_elo']) + ")";
 281                 }
 282                 text += " &nbsp;" + escape_html(data['root_game']['result']).replace(/-/, "&ndash;") + "<br />";
 283                 if (data['root_game']['eco']) {
 284                         text += "[" + escape_html(data['root_game']['eco']) + "] ";
 285                 }
 286                 text += "(" + data['root_game']['moves'] + ") ";
 287                 text += escape_html(data['root_game']['event']) + " &nbsp;" + escape_html(data['root_game']['date']);
 288                 $('#gamesummary').html(text);
 289         }
 290
 291         var total_num = find_total_games(moves);
 292
 293         var headings_tr = $("#headings");
 294         headings_tr.empty();
 295         for (var i = 0; i < headings.length; ++i) {
 296                 var th = document.createElement("th");
 297                 headings_tr.append(th);
 298                 $(th).text(headings[i][0]);
 299                 (function(new_sort_by) {
 300                         $(th).click(function() {
 301                                 if (sort_by == new_sort_by) {
 302                                         direction = -direction;
 303                                 } else {
 304                                         sort_by = new_sort_by;
 305                                         direction = 1;
 306                                 }
 307                                 show_lines(data, game);
 308                         });
 309                 })(i);
 310         }
 311
 312         var lines = [];
 313         var transpose_only = [];
 314         for (var i = 0; i < moves.length; ++i) {
 315                 var move = moves[i];
 316                 var line = [];
 317
 318                 calc_move_derived_data(move, total_num, data, (move_override % 2 == 0));
 319
 320                 var white = move['white'];
 321                 var draw = move['draw'];
 322                 var black = move['black'];
 323                 var computer = move['computer'];
 324
 325                 line.push(move['move']);  // Move.
 326                 transpose_only.push(move['transpose_only']);
 327                 line.push(move['num']);  // N.
 328                 line.push(move['fraction']);  // %.
 329                 line.push(computer);  // CGames.
 330                 line.push(move['human_index']);  // Hum.
 331                 line.push(move['win_ratio']);  // Win%.
 332
 333                 line.push(white);                // WWin.
 334                 line.push(white / move['num']);  // %WW.
 335                 line.push(black);                // BWin.
 336                 line.push(black / move['num']);  // %BW.
 337                 line.push(draw);                 // Draw.
 338                 line.push(draw / move['num']);   // %Draw.
 339
 340                 if (move['num_elo'] >= 10) {
 341                         // Elo.
 342                         line.push(move['white_avg_elo']);
 343                         line.push(move['black_avg_elo']);
 344                         line.push(move['white_avg_elo'] - move['black_avg_elo']);
 345                 } else {
 346                         line.push(null);
 347                         line.push(null);
 348                         line.push(null);
 349                 }
 350
 351                 line.push(move['corrected_win_ratio'] || null);
 352                 lines.push(line);
 353         }
 354
 355         lines.sort(function(a, b) { return direction * ( b[sort_by] - a[sort_by]); });
 356
 357         var tbl = $("#lines");
 358         tbl.empty();
 359
 360         for (var i = 0; i < moves.length; ++i) {
 361                 var line = lines[i];
 362                 var tr = document.createElement("tr");
 363
 364                 if (line[0] === undefined) {
 365                         $(tr).addClass("totals");
 366                 } else if (transpose_only[i]) {
 367                         $(tr).addClass("transponly");
 368                 }
 369
 370                 for (var j = 0; j < line.length; ++j) {
 371                         if (line[j] === null) {
 372                                 add_td(tr, "");
 373                         } else if (headings[j][1] == TYPE_MOVE) {
 374                                 var td = document.createElement("td");
 375                                 tr.appendChild(td);
 376                                 $(td).addClass("move");
 377                                 if (line[j] !== undefined) {
 378                                         if (move_override % 2 == 0) {
 379                                                 $(td).text(((move_override / 2) + 1) + ". ");
 380                                         } else {
 381                                                 $(td).text(((move_override / 2) + 0.5) + "…");
 382                                         }
 383                                 }
 384
 385                                 if (line[j] === '1-0' || line[j] === '1/2-1/2' || line[j] === '0-1') {
 386                                         $(td).text($(td).text() + line[j]);
 387                                 } else {
 388                                         var move_a = document.createElement("a");
 389                                         move_a.href = "javascript:make_move('" + line[j] + "')";
 390                                         td.appendChild(move_a);
 391                                         $(move_a).text(line[j]);
 392                                 }
 393                         } else if (headings[j][1] == TYPE_INTEGER) {
 394                                 add_td(tr, line[j] || 0);
 395                         } else if (headings[j][1] == TYPE_FLOAT) {
 396                                 if (isNaN(line[j]) || !isFinite(line[j])) {
 397                                         add_td(tr, '');
 398                                 } else {
 399                                         add_td(tr, line[j].toFixed(1));
 400                                 }
 401                         } else {
 402                                 if (isNaN(line[j]) || !isFinite(line[j])) {
 403                                         add_td(tr, '');
 404                                 } else {
 405                                         add_td(tr, format_fraction(line[j]));
 406                                 }
 407                         }
 408                 }
 409
 410                 tbl.append(tr);
 411         }
 412 }
 413
 414 var find_total_games = function(moves) {
 415         var total_num = 0;
 416         for (var i = 0; i < moves.length; ++i) {
 417                 var move = moves[i];
 418                 if (move['move']) {
 419                         total_num += move['white'];
 420                         total_num += move['draw'];
 421                         total_num += move['black'];
 422                 }
 423         }
 424         return total_num;
 425 }
 426
 427 var calc_move_derived_data = function(move, total_num, data, is_white) {
 428         var white = move['white'];
 429         var draw = move['draw'];
 430         var black = move['black'];
 431         var computer = move['computer'];
 432
 433         var num = white + draw + black;
 434         move['num'] = num;
 435         move['fraction'] = num / total_num;
 436
 437         // Adjust so that the human index is 50% overall.
 438         var exp = Math.log(0.5) / Math.log(data['computer_games'] / data['total_games']);
 439         move['human_index'] = 1.0 - Math.pow(computer / num, exp);
 440
 441         // Win%.
 442         var white_win_ratio = (white + 0.5 * draw) / num;
 443         var win_ratio = is_white ? white_win_ratio : 1.0 - white_win_ratio;
 444         move['win_ratio'] = win_ratio;
 445
 446         if (move['num_elo'] >= 10) {
 447                 // Win% corrected for Elo.
 448                 var win_elo = -400.0 * Math.log(1.0 / white_win_ratio - 1.0) / Math.LN10;
 449                 win_elo -= (move['white_avg_elo'] - move['black_avg_elo']);
 450                 white_win_ratio = 1.0 / (1.0 + Math.pow(10, win_elo / -400.0));
 451                 win_ratio = is_white ? white_win_ratio : 1.0 - white_win_ratio;
 452                 move['corrected_win_ratio'] = win_ratio;
 453         }
 454 };
 455
 456 var set_includetransp = function(value) {
 457         includetransp = value;
 458         update();
 459 }
 460 window['set_includetransp'] = set_includetransp;
 461
 462 var set_flipboard = function(value) {
 463         board.orientation(value ? 'black' : 'white');
 464 }
 465 window['set_flipboard'] = set_flipboard;
 466
 467 var set_practice = function(value) {
 468         practice_mode = value;
 469         if (practice_mode) {
 470                 practice_side = (move_override % 2 == 0) ? 'W' : 'B';
 471                 find_last_move_score();
 472                 $("#stats").hide();
 473                 $("#practiceoutput").show();
 474                 document.getElementById("includetransp").checked = false;
 475         } else {
 476                 $("#stats").show();
 477                 $("#practiceoutput").hide();
 478         }
 479         update();
 480 }
 481 window['set_practice'] = set_practice;
 482
 483 var make_move = function(move, do_update) {
 484         var history = game.history({ verbose: true });
 485         if (move_override < history.length && history[move_override].san == move) {
 486                 // User effectively only moved forward in history.
 487                 ++move_override;
 488         } else {
 489                 var moves = game.history();
 490                 // Truncate the history if needed.
 491                 if (move_override < moves.length) {
 492                         game = new Chess();
 493                         for (var i = 0; i < move_override; ++i) {
 494                                 game.move(moves[i]);
 495                         }
 496                         fens.length = move_override;
 497                 }
 498                 game.move(move);
 499                 fens.push(game.fen());
 500                 ++move_override;
 501         }
 502
 503         if (do_update !== false) {
 504                 update();
 505                 window.history.pushState(null, null, get_history_url());
 506         }
 507 }
 508 window['make_move'] = make_move;
 509
 510 var prev_move = function() {
 511         var moves_to_skip = practice_mode ? 2 : 1;
 512         if (move_override >= moves_to_skip) {
 513                 move_override -= moves_to_skip;
 514                 update();
 515                 window.history.replaceState(null, null, get_history_url());
 516         }
 517 }
 518 window['prev_move'] = prev_move;
 519
 520 var next_move = function() {
 521         if (move_override < game.history().length) {
 522                 ++move_override;
 523                 update();
 524                 window.history.replaceState(null, null, get_history_url());
 525         }
 526 }
 527 window['next_move'] = next_move;
 528
 529 var set_move = function(n, do_update) {
 530         move_override = n;
 531         if (do_update !== false) {
 532                 update();
 533                 window.history.replaceState(null, null, get_history_url());
 534         }
 535 }
 536 window['set_move'] = set_move;
 537
 538 // almost all of this stuff comes from the chessboard.js example page
 539 var onDragStart = function(source, piece, position, orientation) {
 540         var pseudogame = new Chess(current_display_fen());
 541         if (pseudogame.game_over() === true ||
 542             (pseudogame.turn() === 'w' && piece.search(/^b/) !== -1) ||
 543             (pseudogame.turn() === 'b' && piece.search(/^w/) !== -1)) {
 544                 return false;
 545         }
 546
 547         recommended_move = null;
 548         get_best_dest(pseudogame, source, null, function(src, dest) {
 549                 $("#board").find('.square-55d63').removeClass('nonuglyhighlight');
 550                 if (dest !== null) {
 551                         var squareEl = $('#board .square-' + dest);
 552                         squareEl.addClass('highlight1-32417');
 553                         recommended_move = [src, dest];
 554                 }
 555         });
 556 }
 557
 558 var mousedownSquare = function(e) {
 559         reverse_dragging_from = null;
 560         var square = $(this).attr('data-square');
 561
 562         var pseudogame = new Chess(current_display_fen());
 563         if (pseudogame.game_over() === true) {
 564                 return;
 565         }
 566
 567         // If the square is empty, or has a piece of the side not to move,
 568         // we handle it. If not, normal piece dragging will take it.
 569         var position = board.position();
 570         if (!position.hasOwnProperty(square) ||
 571             (pseudogame.turn() === 'w' && position[square].search(/^b/) !== -1) ||
 572             (pseudogame.turn() === 'b' && position[square].search(/^w/) !== -1)) {
 573                 reverse_dragging_from = square;
 574                 get_best_dest(pseudogame, null, square, function(src, dest) {
 575                         if (src !== null) {
 576                                 var squareEl = $('#board .square-' + src);
 577                                 squareEl.addClass('highlight1-32417');
 578                                 squareEl = $('#board .square-' + dest);
 579                                 squareEl.addClass('highlight1-32417');
 580                                 recommended_move = [src, dest];
 581                         }
 582                 });
 583         } else {
 584                 recommended_src = null;
 585         }
 586 }
 587
 588 var mouseupSquare = function(e) {
 589         if (reverse_dragging_from === null) {
 590                 return;
 591         }
 592         var source = $(this).attr('data-square');
 593         var target = reverse_dragging_from;
 594         reverse_dragging_from = null;
 595         if (onDrop(source, target) !== 'snapback') {
 596                 onSnapEnd(source, target);
 597         }
 598         $("#board").find('.square-55d63').removeClass('highlight1-32417');
 599 }
 600
 601 var get_best_dest = function(game, source, target, cb) {
 602         var moves = game.moves({ verbose: true });
 603         if (source !== null) {
 604                 moves = moves.filter(function(move) { return move.from == source; });
 605         }
 606         if (target !== null) {
 607                 moves = moves.filter(function(move) { return move.to == target; });
 608         }
 609         if (moves.length == 0) {
 610                 cb(null, null);
 611                 return;
 612         }
 613         if (moves.length == 1) {
 614                 cb(moves[0].from, moves[0].to);
 615                 return;
 616         }
 617
 618         // More than one move. Ask the engine to disambiguate.
 619         var uci_moves = moves.map(function(m) { return m.from + m.to; });
 620         var when_engine_is_ready = function() {
 621                 engine_running = true;
 622                 stockfish.onmessage = function(event) {
 623                         var res = event.data.match(/^bestmove (\S\S)(\S\S)/);
 624                         if (res !== null) {
 625                                 engine_running = false;
 626                                 if (engine_replacement_callback !== null) {
 627                                         // We are no longer interested in this query,
 628                                         // so just discard it and call this other callback.
 629                                         engine_replacement_callback();
 630                                         engine_replacement_callback = null;
 631                                 } else {
 632                                         cb(res[1], res[2]);
 633                                 }
 634                         }
 635                 };
 636                 stockfish.postMessage("position fen " + game.fen());
 637                 stockfish.postMessage("go depth 6 searchmoves " + uci_moves.join(" "));
 638         };
 639         if (engine_running) {
 640                 engine_replacement_callback = when_engine_is_ready;
 641         } else {
 642                 when_engine_is_ready();
 643         }
 644 }
 645
 646 var onDrop = function(source, target) {
 647         if (engine_running) {
 648                 // Snap end before the engine came back.
 649                 // Discard the result when it does.
 650                 engine_replacement_callback = function() {};
 651         }
 652         if (source == target) {
 653                 if (recommended_move === null) {
 654                         return 'snapback';
 655                 } else {
 656                         // Accept the move. It will be changed in onSnapEnd.
 657                         return;
 658                 }
 659         } else {
 660                 // Suggestion not asked for.
 661                 recommended_move = null;
 662         }
 663
 664         // see if the move is legal
 665         var pseudogame = new Chess(current_display_fen());
 666         var move = pseudogame.move({
 667                 from: source,
 668                 to: target,
 669                 promotion: 'q' // NOTE: always promote to a queen for example simplicity
 670         });
 671
 672         // illegal move
 673         if (move === null) return 'snapback';
 674 }
 675
 676 var onSnapEnd = function(source, target) {
 677         if (source == target && recommended_move !== null) {
 678                 source = recommended_move[0];
 679                 target = recommended_move[1];
 680         }
 681         recommended_move = null;
 682         var pseudogame = new Chess(current_display_fen());
 683         var move = pseudogame.move({
 684                 from: source,
 685                 to: target,
 686                 promotion: 'q' // NOTE: always promote to a queen for example simplicity
 687         });
 688
 689         make_move(pseudogame.history({ verbose: true }).pop().san);
 690 }
 691
 692 var onpopstate = function() {
 693         var old_moves = game.history({ verbose: true }).map(function(x) { return x.san; });
 694         var new_moves = document.location.search.replace(/^\?/, "").split(",");
 695
 696         if (new_moves.length == 1 && new_moves[0] == "") {
 697                 new_moves = [];
 698         }
 699
 700         var num_shared_moves;
 701         for (num_shared_moves = 0; num_shared_moves < Math.min(old_moves.length, new_moves.length); ++num_shared_moves) {
 702                 if (old_moves[i] != new_moves[i]) {
 703                         break;
 704                 }
 705         }
 706
 707         set_move(num_shared_moves, false);
 708         for (var i = num_shared_moves; i < new_moves.length; ++i) {
 709                 make_move(new_moves[i], false);
 710         }
 711         update();
 712         window.history.replaceState(null, null, get_history_url());
 713 }
 714
 715 var init = function() {
 716         // Create board.
 717         board = new window.ChessBoard('board', {
 718                 draggable: true,
 719                 position: 'start',
 720                 onDragStart: onDragStart,
 721                 onDrop: onDrop,
 722                 onSnapEnd: onSnapEnd
 723         });
 724         $("#board").on('mousedown', '.square-55d63', mousedownSquare);
 725         $("#board").on('mouseup', '.square-55d63', mouseupSquare);
 726
 727         window.onpopstate = onpopstate;
 728         onpopstate();
 729         set_practice(false);
 730
 731         $(window).keyup(function(event) {
 732                 if (event.which == 39) {
 733                         next_move();
 734                 } else if (event.which == 37) {
 735                         prev_move();
 736                 }
 737         });
 738
 739         // Seemingly the web worker is not started before we send it a message.
 740         stockfish.postMessage("uci");
 741 }
 742
 743 $(document).ready(init);
 744
 745 })();