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_moves_by_common(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                 moves.sort(function(a, b) { return b['num'] - a['num'] });
 135
 136                 if (your_move) {
 137                         $("#yourfraction").text(format_fraction(your_move['fraction']));
 138                         $("#yourawin").text(format_fraction(your_move['corrected_win_ratio']));
 139                         $("#yourrank").text(format_ordinal(your_index + 1) + ", based on " + root_move['num'] + " games");
 140                         var diff = your_move['corrected_win_ratio'] - root_move['corrected_win_ratio'];
 141                         $("#yourawindiff").css("color", "black");
 142                         if (diff === 0) {
 143                                 $("#yourawindiff").text("0.0%");
 144                         } else if (diff > 0) {
 145                                 $("#yourawindiff").text("+" + format_fraction(diff));
 146                                 $("#yourawindiff").css("color", "green");
 147                         } else {
 148                                 $("#yourawindiff").text(format_fraction(diff));
 149                                 if (diff < -0.02) {
 150                                         $("#yourawindiff").css("color", "red");
 151                                 }
 152                         }
 153                 } else {
 154                         $("#yourfraction").text("??.?%");
 155                         $("#yourrank").text("?th");
 156                         $("#yourawin").text("??.?%");
 157                         $("#yourawindiff").text("+?.?%");
 158                 }
 159         });
 160 }
 161
 162 var find_computer_move = function() {
 163         var fen = current_display_fen();
 164         $.ajax({
 165                 url: "/opening-stats.pl?fen=" + encodeURIComponent(fen) + ";includetransp=0"
 166         }).done(function(data, textstatus, xhr) {
 167                 var candidate_moves = [];
 168
 169                 var moves = data['moves'];
 170                 var root_move = sort_moves_by_common(moves, data);
 171
 172                 var practice_minimum_move_fraction;
 173                 if (move_override > 20) {
 174                         practice_minimum_move_fraction = practice_minimum_move_fraction_move5;
 175                 } else {
 176                         practice_minimum_move_fraction = practice_minimum_move_fraction_start +
 177                                 ((move_override-1)/10.0) * (practice_minimum_move_fraction_move5 - practice_minimum_move_fraction_start);
 178                 }
 179                 console.log(practice_minimum_move_fraction);
 180
 181                 for (var i = 0; i < Math.min(moves.length, practice_top_moves_limit); ++i) {
 182                         var move = moves[i];
 183                         if (i == 0 || move['fraction'] >= practice_minimum_move_fraction) {
 184                                 candidate_moves.push(move);
 185                         }
 186                 }
 187
 188                 // Pick one at random.
 189                 var chosen_index = Math.floor(Math.random() * candidate_moves.length);
 190                 var chosen = candidate_moves[chosen_index];
 191                 $("#compmove").text(chosen['move']);
 192                 $("#compfraction").text((100.0 * chosen['fraction']).toFixed(1) + "%");
 193                 if (candidate_moves.length == 1) {
 194                         $("#comprank").text("only candidate move");
 195                 } else {
 196                         $("#comprank").text(format_ordinal(chosen_index + 1) + " out of " + candidate_moves.length + " candidate moves");
 197                 }
 198                 make_move(chosen['move']);
 199         });
 200 }
 201
 202 // Add deried data and then sort moves to get the most common ones (in-place).
 203 // Remove the root mode and return it. Currently usable for practice mode only!
 204 var sort_moves_by_common = function(moves, data)
 205 {
 206         var total_num = find_total_games(moves);
 207         var root_move;
 208         for (var i = 0; i < moves.length; ++i) {
 209                 var move = moves[i];
 210                 calc_move_derived_data(move, total_num, data, (practice_side === 'W'));
 211                 if (!move['move']) {
 212                         root_move = (moves.splice(i, 1))[0];
 213                         --i;
 214                 }
 215         }
 216         moves.sort(function(a, b) { return b['num'] - a['num'] });
 217         return root_move;
 218 }
 219
 220 var add_td = function(tr, value) {
 221         var td = document.createElement("td");
 222         tr.appendChild(td);
 223         $(td).addClass("num");
 224         $(td).text(value);
 225 }
 226
 227 var format_ordinal = function(x) {
 228         var tens = Math.floor(x / 10) % 10;
 229         if (tens == 1) {
 230                 return x + "th";
 231         } else {
 232                 var ones = x % 10;
 233                 if (ones == 1) return x + "st";
 234                 if (ones == 2) return x + "nd";
 235                 if (ones == 3) return x + "rd";
 236                 return x + "th";
 237         }
 238 }
 239
 240 var format_fraction = function(x) {
 241         return (100.0 * x).toFixed(1) + '%';
 242 }
 243
 244 var TYPE_MOVE = 0;
 245 var TYPE_INTEGER = 1;
 246 var TYPE_FLOAT = 2;
 247 var TYPE_RATIO = 3;
 248
 249 var headings = [
 250         [ "Move", TYPE_MOVE ],
 251         [ "Games", TYPE_INTEGER ],
 252         [ "%", TYPE_RATIO ],
 253         [ "CGames", TYPE_INTEGER ],
 254         [ "Hum", TYPE_RATIO ],
 255         [ "Win%", TYPE_RATIO ],
 256         [ "WWin", TYPE_INTEGER ],
 257         [ "%WW", TYPE_RATIO ],
 258         [ "Bwin", TYPE_INTEGER ],
 259         [ "%BW", TYPE_RATIO ],
 260         [ "Draw", TYPE_INTEGER ],
 261         [ "Draw%", TYPE_RATIO ],
 262         [ "AvWElo", TYPE_FLOAT ],
 263         [ "AvBElo", TYPE_FLOAT ],
 264         [ "EloVar", TYPE_FLOAT ],
 265         [ "AWin%", TYPE_RATIO ],
 266 ];
 267 var sort_by = 1;
 268 var direction = 1;
 269
 270 var show_lines = function(data, game) {
 271         var moves = data['moves'];
 272         $('#numviewers').text(data['opening']);
 273
 274         if (data['root_game']) {
 275                 var text = escape_html(data['root_game']['white']);
 276                 if (data['root_game']['white_elo']) {
 277                         text += " (" + escape_html(data['root_game']['white_elo']) + ")";
 278                 }
 279                 text += " &ndash; " + escape_html(data['root_game']['black']);
 280                 if (data['root_game']['black_elo']) {
 281                         text += " (" + escape_html(data['root_game']['black_elo']) + ")";
 282                 }
 283                 text += " &nbsp;" + escape_html(data['root_game']['result']).replace(/-/, "&ndash;") + "<br />";
 284                 if (data['root_game']['eco']) {
 285                         text += "[" + escape_html(data['root_game']['eco']) + "] ";
 286                 }
 287                 text += "(" + data['root_game']['moves'] + ") ";
 288                 text += escape_html(data['root_game']['event']) + " &nbsp;" + escape_html(data['root_game']['date']);
 289                 $('#gamesummary').html(text);
 290         }
 291
 292         var total_num = find_total_games(moves);
 293
 294         var headings_tr = $("#headings");
 295         headings_tr.empty();
 296         for (var i = 0; i < headings.length; ++i) {
 297                 var th = document.createElement("th");
 298                 headings_tr.append(th);
 299                 $(th).text(headings[i][0]);
 300                 (function(new_sort_by) {
 301                         $(th).click(function() {
 302                                 if (sort_by == new_sort_by) {
 303                                         direction = -direction;
 304                                 } else {
 305                                         sort_by = new_sort_by;
 306                                         direction = 1;
 307                                 }
 308                                 show_lines(data, game);
 309                         });
 310                 })(i);
 311         }
 312
 313         var lines = [];
 314         var transpose_only = [];
 315         for (var i = 0; i < moves.length; ++i) {
 316                 var move = moves[i];
 317                 var line = [];
 318
 319                 calc_move_derived_data(move, total_num, data, (move_override % 2 == 0));
 320
 321                 var white = move['white'];
 322                 var draw = move['draw'];
 323                 var black = move['black'];
 324                 var computer = move['computer'];
 325
 326                 line.push(move['move']);  // Move.
 327                 transpose_only.push(move['transpose_only']);
 328                 line.push(move['num']);  // N.
 329                 line.push(move['fraction']);  // %.
 330                 line.push(computer);  // CGames.
 331                 line.push(move['human_index']);  // Hum.
 332                 line.push(move['win_ratio']);  // Win%.
 333
 334                 line.push(white);                // WWin.
 335                 line.push(white / move['num']);  // %WW.
 336                 line.push(black);                // BWin.
 337                 line.push(black / move['num']);  // %BW.
 338                 line.push(draw);                 // Draw.
 339                 line.push(draw / move['num']);   // %Draw.
 340
 341                 if (move['num_elo'] >= 10) {
 342                         // Elo.
 343                         line.push(move['white_avg_elo']);
 344                         line.push(move['black_avg_elo']);
 345                         line.push(move['white_avg_elo'] - move['black_avg_elo']);
 346                 } else {
 347                         line.push(null);
 348                         line.push(null);
 349                         line.push(null);
 350                 }
 351
 352                 line.push(move['corrected_win_ratio'] || null);
 353                 lines.push(line);
 354         }
 355
 356         lines.sort(function(a, b) { return direction * ( b[sort_by] - a[sort_by]); });
 357
 358         var tbl = $("#lines");
 359         tbl.empty();
 360
 361         for (var i = 0; i < moves.length; ++i) {
 362                 var line = lines[i];
 363                 var tr = document.createElement("tr");
 364
 365                 if (line[0] === undefined) {
 366                         $(tr).addClass("totals");
 367                 } else if (transpose_only[i]) {
 368                         $(tr).addClass("transponly");
 369                 }
 370
 371                 for (var j = 0; j < line.length; ++j) {
 372                         if (line[j] === null) {
 373                                 add_td(tr, "");
 374                         } else if (headings[j][1] == TYPE_MOVE) {
 375                                 var td = document.createElement("td");
 376                                 tr.appendChild(td);
 377                                 $(td).addClass("move");
 378                                 if (line[j] !== undefined) {
 379                                         if (move_override % 2 == 0) {
 380                                                 $(td).text(((move_override / 2) + 1) + ". ");
 381                                         } else {
 382                                                 $(td).text(((move_override / 2) + 0.5) + "…");
 383                                         }
 384                                 }
 385
 386                                 if (line[j] === '1-0' || line[j] === '1/2-1/2' || line[j] === '0-1') {
 387                                         $(td).text($(td).text() + line[j]);
 388                                 } else {
 389                                         var move_a = document.createElement("a");
 390                                         move_a.href = "javascript:make_move('" + line[j] + "')";
 391                                         td.appendChild(move_a);
 392                                         $(move_a).text(line[j]);
 393                                 }
 394                         } else if (headings[j][1] == TYPE_INTEGER) {
 395                                 add_td(tr, line[j] || 0);
 396                         } else if (headings[j][1] == TYPE_FLOAT) {
 397                                 if (isNaN(line[j]) || !isFinite(line[j])) {
 398                                         add_td(tr, '');
 399                                 } else {
 400                                         add_td(tr, line[j].toFixed(1));
 401                                 }
 402                         } else {
 403                                 if (isNaN(line[j]) || !isFinite(line[j])) {
 404                                         add_td(tr, '');
 405                                 } else {
 406                                         add_td(tr, format_fraction(line[j]));
 407                                 }
 408                         }
 409                 }
 410
 411                 tbl.append(tr);
 412         }
 413 }
 414
 415 var find_total_games = function(moves) {
 416         var total_num = 0;
 417         for (var i = 0; i < moves.length; ++i) {
 418                 var move = moves[i];
 419                 if (move['move']) {
 420                         total_num += move['white'];
 421                         total_num += move['draw'];
 422                         total_num += move['black'];
 423                 }
 424         }
 425         return total_num;
 426 }
 427
 428 var calc_move_derived_data = function(move, total_num, data, is_white) {
 429         var white = move['white'];
 430         var draw = move['draw'];
 431         var black = move['black'];
 432         var computer = move['computer'];
 433
 434         var num = white + draw + black;
 435         move['num'] = num;
 436         move['fraction'] = num / total_num;
 437
 438         // Adjust so that the human index is 50% overall.
 439         var exp = Math.log(0.5) / Math.log(data['computer_games'] / data['total_games']);
 440         move['human_index'] = 1.0 - Math.pow(computer / num, exp);
 441
 442         // Win%.
 443         var white_win_ratio = (white + 0.5 * draw) / num;
 444         var win_ratio = is_white ? white_win_ratio : 1.0 - white_win_ratio;
 445         move['win_ratio'] = win_ratio;
 446
 447         if (move['num_elo'] >= 10) {
 448                 // Win% corrected for Elo.
 449                 var win_elo = -400.0 * Math.log(1.0 / white_win_ratio - 1.0) / Math.LN10;
 450                 win_elo -= (move['white_avg_elo'] - move['black_avg_elo']);
 451                 white_win_ratio = 1.0 / (1.0 + Math.pow(10, win_elo / -400.0));
 452                 win_ratio = is_white ? white_win_ratio : 1.0 - white_win_ratio;
 453                 move['corrected_win_ratio'] = win_ratio;
 454         }
 455 };
 456
 457 var set_includetransp = function(value) {
 458         includetransp = value;
 459         update();
 460 }
 461 window['set_includetransp'] = set_includetransp;
 462
 463 var set_flipboard = function(value) {
 464         board.orientation(value ? 'black' : 'white');
 465 }
 466 window['set_flipboard'] = set_flipboard;
 467
 468 var set_practice = function(value) {
 469         practice_mode = value;
 470         if (practice_mode) {
 471                 practice_side = (move_override % 2 == 0) ? 'W' : 'B';
 472                 find_last_move_score();
 473                 $("#stats").hide();
 474                 $("#practiceoutput").show();
 475                 document.getElementById("includetransp").checked = false;
 476         } else {
 477                 $("#stats").show();
 478                 $("#practiceoutput").hide();
 479         }
 480         update();
 481 }
 482 window['set_practice'] = set_practice;
 483
 484 var make_move = function(move, do_update) {
 485         var history = game.history({ verbose: true });
 486         if (move_override < history.length && history[move_override].san == move) {
 487                 // User effectively only moved forward in history.
 488                 ++move_override;
 489         } else {
 490                 var moves = game.history();
 491                 // Truncate the history if needed.
 492                 if (move_override < moves.length) {
 493                         game = new Chess();
 494                         for (var i = 0; i < move_override; ++i) {
 495                                 game.move(moves[i]);
 496                         }
 497                         fens.length = move_override;
 498                 }
 499                 game.move(move);
 500                 fens.push(game.fen());
 501                 ++move_override;
 502         }
 503
 504         if (do_update !== false) {
 505                 update();
 506                 window.history.pushState(null, null, get_history_url());
 507         }
 508 }
 509 window['make_move'] = make_move;
 510
 511 var prev_move = function() {
 512         var moves_to_skip = practice_mode ? 2 : 1;
 513         if (move_override >= moves_to_skip) {
 514                 move_override -= moves_to_skip;
 515                 update();
 516                 window.history.replaceState(null, null, get_history_url());
 517         }
 518 }
 519 window['prev_move'] = prev_move;
 520
 521 var next_move = function() {
 522         if (move_override < game.history().length) {
 523                 ++move_override;
 524                 update();
 525                 window.history.replaceState(null, null, get_history_url());
 526         }
 527 }
 528 window['next_move'] = next_move;
 529
 530 var set_move = function(n, do_update) {
 531         move_override = n;
 532         if (do_update !== false) {
 533                 update();
 534                 window.history.replaceState(null, null, get_history_url());
 535         }
 536 }
 537 window['set_move'] = set_move;
 538
 539 // almost all of this stuff comes from the chessboard.js example page
 540 var onDragStart = function(source, piece, position, orientation) {
 541         var pseudogame = new Chess(current_display_fen());
 542         if (pseudogame.game_over() === true ||
 543             (pseudogame.turn() === 'w' && piece.search(/^b/) !== -1) ||
 544             (pseudogame.turn() === 'b' && piece.search(/^w/) !== -1)) {
 545                 return false;
 546         }
 547
 548         recommended_move = null;
 549         get_best_dest(pseudogame, source, null, function(src, dest) {
 550                 $("#board").find('.square-55d63').removeClass('nonuglyhighlight');
 551                 if (dest !== null) {
 552                         var squareEl = $('#board .square-' + dest);
 553                         squareEl.addClass('highlight1-32417');
 554                         recommended_move = [src, dest];
 555                 }
 556         });
 557 }
 558
 559 var mousedownSquare = function(e) {
 560         reverse_dragging_from = null;
 561         var square = $(this).attr('data-square');
 562
 563         var pseudogame = new Chess(current_display_fen());
 564         if (pseudogame.game_over() === true) {
 565                 return;
 566         }
 567
 568         // If the square is empty, or has a piece of the side not to move,
 569         // we handle it. If not, normal piece dragging will take it.
 570         var position = board.position();
 571         if (!position.hasOwnProperty(square) ||
 572             (pseudogame.turn() === 'w' && position[square].search(/^b/) !== -1) ||
 573             (pseudogame.turn() === 'b' && position[square].search(/^w/) !== -1)) {
 574                 reverse_dragging_from = square;
 575                 get_best_dest(pseudogame, null, square, function(src, dest) {
 576                         if (src !== null) {
 577                                 var squareEl = $('#board .square-' + src);
 578                                 squareEl.addClass('highlight1-32417');
 579                                 squareEl = $('#board .square-' + dest);
 580                                 squareEl.addClass('highlight1-32417');
 581                                 recommended_move = [src, dest];
 582                         }
 583                 });
 584         } else {
 585                 recommended_src = null;
 586         }
 587 }
 588
 589 var mouseupSquare = function(e) {
 590         if (reverse_dragging_from === null) {
 591                 return;
 592         }
 593         var source = $(this).attr('data-square');
 594         var target = reverse_dragging_from;
 595         reverse_dragging_from = null;
 596         if (onDrop(source, target) !== 'snapback') {
 597                 onSnapEnd(source, target);
 598         }
 599         $("#board").find('.square-55d63').removeClass('highlight1-32417');
 600 }
 601
 602 var get_best_dest = function(game, source, target, cb) {
 603         var moves = game.moves({ verbose: true });
 604         if (source !== null) {
 605                 moves = moves.filter(function(move) { return move.from == source; });
 606         }
 607         if (target !== null) {
 608                 moves = moves.filter(function(move) { return move.to == target; });
 609         }
 610         if (moves.length == 0) {
 611                 cb(null, null);
 612                 return;
 613         }
 614         if (moves.length == 1) {
 615                 cb(moves[0].from, moves[0].to);
 616                 return;
 617         }
 618
 619         // More than one move. Ask the engine to disambiguate.
 620         var uci_moves = moves.map(function(m) { return m.from + m.to; });
 621         var when_engine_is_ready = function() {
 622                 engine_running = true;
 623                 stockfish.onmessage = function(event) {
 624                         var res = event.data.match(/^bestmove (\S\S)(\S\S)/);
 625                         if (res !== null) {
 626                                 engine_running = false;
 627                                 if (engine_replacement_callback !== null) {
 628                                         // We are no longer interested in this query,
 629                                         // so just discard it and call this other callback.
 630                                         engine_replacement_callback();
 631                                         engine_replacement_callback = null;
 632                                 } else {
 633                                         cb(res[1], res[2]);
 634                                 }
 635                         }
 636                 };
 637                 stockfish.postMessage("position fen " + game.fen());
 638                 stockfish.postMessage("go depth 6 searchmoves " + uci_moves.join(" "));
 639         };
 640         if (engine_running) {
 641                 engine_replacement_callback = when_engine_is_ready;
 642         } else {
 643                 when_engine_is_ready();
 644         }
 645 }
 646
 647 var onDrop = function(source, target) {
 648         if (engine_running) {
 649                 // Snap end before the engine came back.
 650                 // Discard the result when it does.
 651                 engine_replacement_callback = function() {};
 652         }
 653         if (source == target) {
 654                 if (recommended_move === null) {
 655                         return 'snapback';
 656                 } else {
 657                         // Accept the move. It will be changed in onSnapEnd.
 658                         return;
 659                 }
 660         } else {
 661                 // Suggestion not asked for.
 662                 recommended_move = null;
 663         }
 664
 665         // see if the move is legal
 666         var pseudogame = new Chess(current_display_fen());
 667         var move = pseudogame.move({
 668                 from: source,
 669                 to: target,
 670                 promotion: 'q' // NOTE: always promote to a queen for example simplicity
 671         });
 672
 673         // illegal move
 674         if (move === null) return 'snapback';
 675 }
 676
 677 var onSnapEnd = function(source, target) {
 678         if (source == target && recommended_move !== null) {
 679                 source = recommended_move[0];
 680                 target = recommended_move[1];
 681         }
 682         recommended_move = null;
 683         var pseudogame = new Chess(current_display_fen());
 684         var move = pseudogame.move({
 685                 from: source,
 686                 to: target,
 687                 promotion: 'q' // NOTE: always promote to a queen for example simplicity
 688         });
 689
 690         make_move(pseudogame.history({ verbose: true }).pop().san);
 691 }
 692
 693 var onpopstate = function() {
 694         var old_moves = game.history({ verbose: true }).map(function(x) { return x.san; });
 695         var new_moves = document.location.search.replace(/^\?/, "").split(",");
 696
 697         if (new_moves.length == 1 && new_moves[0] == "") {
 698                 new_moves = [];
 699         }
 700
 701         var num_shared_moves;
 702         for (num_shared_moves = 0; num_shared_moves < Math.min(old_moves.length, new_moves.length); ++num_shared_moves) {
 703                 if (old_moves[i] != new_moves[i]) {
 704                         break;
 705                 }
 706         }
 707
 708         set_move(num_shared_moves, false);
 709         for (var i = num_shared_moves; i < new_moves.length; ++i) {
 710                 make_move(new_moves[i], false);
 711         }
 712         update();
 713         window.history.replaceState(null, null, get_history_url());
 714 }
 715
 716 var init = function() {
 717         // Create board.
 718         board = new window.ChessBoard('board', {
 719                 draggable: true,
 720                 position: 'start',
 721                 onDragStart: onDragStart,
 722                 onDrop: onDrop,
 723                 onSnapEnd: onSnapEnd
 724         });
 725         $("#board").on('mousedown', '.square-55d63', mousedownSquare);
 726         $("#board").on('mouseup', '.square-55d63', mouseupSquare);
 727
 728         window.onpopstate = onpopstate;
 729         onpopstate();
 730         set_practice(false);
 731
 732         $(window).keyup(function(event) {
 733                 if (event.which == 39) {
 734                         next_move();
 735                 } else if (event.which == 37) {
 736                         prev_move();
 737                 }
 738         });
 739
 740         // Seemingly the web worker is not started before we send it a message.
 741         stockfish.postMessage("uci");
 742 }
 743
 744 $(document).ready(init);
 745
 746 })();