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

   1 (function() {
   2
   3 /**
   4  * Version of this script. If the server returns a version larger than
   5  * this, it is a sign we should reload to upgrade ourselves.
   6  *
   7  * @type {Number}
   8  * @const
   9  * @private */
  10 var SCRIPT_VERSION = 2016032201;
  11
  12 /**
  13  * The current backend URL.
  14  *
  15  * @type {!string}
  16  * @private
  17  */
  18 var backend_url = "/analysis.pl";
  19 var backend_hash_url = "/hash";
  20
  21 /** @type {window.ChessBoard} @private */
  22 var board = null;
  23
  24 /** @type {boolean} @private */
  25 var board_is_animating = false;
  26
  27 /**
  28  * The most recent analysis data we have from the server
  29  * (about the most recent position).
  30  *
  31  * @type {?Object}
  32  * @private */
  33 var current_analysis_data = null;
  34
  35 /**
  36  * If we are displaying previous analysis or from hash, this is non-null,
  37  * and will override most of current_analysis_data.
  38  *
  39  * @type {?Object}
  40  * @private
  41  */
  42 var displayed_analysis_data = null;
  43
  44 /**
  45  * Games currently in progress, if any.
  46  *
  47  * @type {?Array.<{
  48  *      name: string,
  49  *      url: string,
  50  *      id: string,
  51  *      score: =Object,
  52  *      result: =string,
  53  * }>}
  54  * @private
  55  */
  56 var current_games = null;
  57
  58 /** @type {Array.<{
  59  *      from_col: number,
  60  *      from_row: number,
  61  *      to_col: number,
  62  *      to_row: number,
  63  *      line_width: number,
  64  *      arrow_size: number,
  65  *      fg_color: string
  66  * }>}
  67  * @private
  68  */
  69 var arrows = [];
  70
  71 /** @type {Array.<Array.<boolean>>} */
  72 var occupied_by_arrows = [];
  73
  74 /** Currently displayed refutation lines (on-screen).
  75  * Can either come from the current_analysis_data, displayed_analysis_data,
  76  * or hash_refutation_lines.
  77  */
  78 var refutation_lines = [];
  79
  80 /** Refutation lines from current hash probe.
  81  *
  82  * If non-null, will override refutation lines from the base position.
  83  * Note that these are relative to display_fen, not base_fen.
  84  */
  85 var hash_refutation_lines = null;
  86
  87 /** @type {!number} @private */
  88 var move_num = 1;
  89
  90 /** @type {!string} @private */
  91 var toplay = 'W';
  92
  93 /** @type {number} @private */
  94 var ims = 0;
  95
  96 /** @type {boolean} @private */
  97 var sort_refutation_lines_by_score = true;
  98
  99 /** @type {boolean} @private */
 100 var truncate_display_history = true;
 101
 102 /** @type {!string|undefined} @private */
 103 var highlight_from = undefined;
 104
 105 /** @type {!string|undefined} @private */
 106 var highlight_to = undefined;
 107
 108 /** The HTML object of the move currently being highlighted (in red).
 109  * @type {?jQuery}
 110  * @private */
 111 var highlighted_move = null;
 112
 113 /** Currently suggested/recommended move when dragging.
 114  * @type {?{from: !string, to: !string}}
 115  * @private
 116  */
 117 var recommended_move = null;
 118
 119 /** If reverse-dragging (dragging from the destination square to the
 120  * source square), the destination square.
 121  * @type {?string}
 122  * @private
 123  */
 124 var reverse_dragging_from = null;
 125
 126 /** @type {?number} @private */
 127 var unique = null;
 128
 129 /** @type {boolean} @private */
 130 var enable_sound = false;
 131
 132 /**
 133  * Our best estimate of how many milliseconds we need to add to
 134  * new Date() to get the true UTC time. Calibrated against the
 135  * server clock.
 136  *
 137  * @type {?number}
 138  * @private
 139  */
 140 var client_clock_offset_ms = null;
 141
 142 var clock_timer = null;
 143
 144 /** The current position being analyzed, represented as a FEN string.
 145  * Note that this is not necessarily the same as display_fen.
 146  * @type {?string}
 147  * @private
 148  */
 149 var base_fen = null;
 150
 151 /** The current position on the board, represented as a FEN string.
 152  * Note that board.fen() does not contain e.g. who is to play.
 153  * @type {?string}
 154  * @private
 155  */
 156 var display_fen = null;
 157
 158 /** @typedef {{
 159  *    start_fen: string,
 160  *    pretty_pv: Array.<string>,
 161  *    move_num: number,
 162  *    toplay: string,
 163  *    scores: Array<{first_move: number, score: Object}>,
 164  *    start_display_move_num: number
 165  * }} DisplayLine
 166  *
 167  * "start_display_move_num" is the (half-)move number to start displaying the PV at.
 168  * "score" is also evaluated at this point.
 169  */
 170
 171 /** All PVs that we currently know of.
 172  *
 173  * Element 0 is history (or null if no history).
 174  * Element 1 is current main PV, or explored line if nowhere else on the screen.
 175  * All remaining elements are refutation lines (multi-PV).
 176  *
 177  * @type {Array.<DisplayLine>}
 178  * @private
 179  */
 180 var display_lines = [];
 181
 182 /** @type {?DisplayLine} @private */
 183 var current_display_line = null;
 184
 185 /** @type {boolean} @private */
 186 var current_display_line_is_history = false;
 187
 188 /** @type {?number} @private */
 189 var current_display_move = null;
 190
 191 /**
 192  * The current backend request to get main analysis (not history), if any,
 193  * so that we can abort it.
 194  *
 195  * @type {?jqXHR}
 196  * @private
 197  */
 198 var current_analysis_xhr = null;
 199
 200 /**
 201  * The current timer to fire off a request to get main analysis (not history),
 202  * if any, so that we can abort it.
 203  *
 204  * @type {?Number}
 205  * @private
 206  */
 207 var current_analysis_request_timer = null;
 208
 209 /**
 210  * The current backend request to get historic data, if any.
 211  *
 212  * @type {?jqXHR}
 213  * @private
 214  */
 215 var current_historic_xhr = null;
 216
 217 /**
 218  * The current backend request to get hash probes, if any, so that we can abort it.
 219  *
 220  * @type {?jqXHR}
 221  * @private
 222  */
 223 var current_hash_xhr = null;
 224
 225 /**
 226  * The current timer to display hash probe information (it could be waiting on the
 227  * board to stop animating), if any, so that we can abort it.
 228  *
 229  * @type {?Number}
 230  * @private
 231  */
 232 var current_hash_display_timer = null;
 233
 234 var supports_html5_storage = function() {
 235         try {
 236                 return 'localStorage' in window && window['localStorage'] !== null;
 237         } catch (e) {
 238                 return false;
 239         }
 240 }
 241
 242 // Make the unique token persistent so people refreshing the page won't count twice.
 243 // Of course, you can never fully protect against people deliberately wanting to spam.
 244 var get_unique = function() {
 245         var use_local_storage = supports_html5_storage();
 246         if (use_local_storage && localStorage['unique']) {
 247                 return localStorage['unique'];
 248         }
 249         var unique = Math.random();
 250         if (use_local_storage) {
 251                 localStorage['unique'] = unique;
 252         }
 253         return unique;
 254 }
 255
 256 var request_update = function() {
 257         current_analysis_request_timer = null;
 258
 259         current_analysis_xhr = $.ajax({
 260                 url: backend_url + "?ims=" + ims + "&unique=" + unique
 261         }).done(function(data, textstatus, xhr) {
 262                 sync_server_clock(xhr.getResponseHeader('Date'));
 263                 ims = xhr.getResponseHeader('X-RGLM');
 264                 var num_viewers = xhr.getResponseHeader('X-RGNV');
 265                 var new_data;
 266                 if (Array.isArray(data)) {
 267                         new_data = JSON.parse(JSON.stringify(current_analysis_data));
 268                         JSON_delta.patch(new_data, data);
 269                 } else {
 270                         new_data = data;
 271                 }
 272
 273                 var minimum_version = xhr.getResponseHeader('X-RGMV');
 274                 if (minimum_version && minimum_version > SCRIPT_VERSION) {
 275                         // Upgrade to latest version with a force-reload.
 276                         location.reload(true);
 277                 }
 278
 279                 possibly_play_sound(current_analysis_data, new_data);
 280                 current_analysis_data = new_data;
 281                 update_board();
 282                 update_num_viewers(num_viewers);
 283
 284                 // Next update.
 285                 current_analysis_request_timer = setTimeout(function() { request_update(); }, 100);
 286         }).fail(function(jqXHR, textStatus, errorThrown) {
 287                 if (textStatus === "abort") {
 288                         // Aborted because we are switching backends. Abandon and don't retry,
 289                         // because another one is already started for us.
 290                 } else {
 291                         // Backend error or similar. Wait ten seconds, then try again.
 292                         current_analysis_request_timer = setTimeout(function() { request_update(); }, 10000);
 293                 }
 294         });
 295 }
 296
 297 var possibly_play_sound = function(old_data, new_data) {
 298         if (!enable_sound) {
 299                 return;
 300         }
 301         if (old_data === null) {
 302                 return;
 303         }
 304         var ding = document.getElementById('ding');
 305         if (ding && ding.play) {
 306                 if (old_data['position'] && old_data['position']['fen'] &&
 307                     new_data['position'] && new_data['position']['fen'] &&
 308                     (old_data['position']['fen'] !== new_data['position']['fen'] ||
 309                      old_data['position']['move_num'] !== new_data['position']['move_num'])) {
 310                         ding.play();
 311                 }
 312         }
 313 }
 314
 315 /**
 316  * @type {!string} server_date_string
 317  */
 318 var sync_server_clock = function(server_date_string) {
 319         var server_time_ms = new Date(server_date_string).getTime();
 320         var client_time_ms = new Date().getTime();
 321         var estimated_offset_ms = server_time_ms - client_time_ms;
 322
 323         // In order not to let the noise move us too much back and forth
 324         // (the server only has one-second resolution anyway), we only
 325         // change an existing skew if we are at least five seconds off.
 326         if (client_clock_offset_ms === null ||
 327             Math.abs(estimated_offset_ms - client_clock_offset_ms) > 5000) {
 328                 client_clock_offset_ms = estimated_offset_ms;
 329         }
 330 }
 331
 332 var clear_arrows = function() {
 333         for (var i = 0; i < arrows.length; ++i) {
 334                 if (arrows[i].svg) {
 335                         if (arrows[i].svg.parentElement) {
 336                                 arrows[i].svg.parentElement.removeChild(arrows[i].svg);
 337                         }
 338                         delete arrows[i].svg;
 339                 }
 340         }
 341         arrows = [];
 342
 343         occupied_by_arrows = [];
 344         for (var y = 0; y < 8; ++y) {
 345                 occupied_by_arrows.push([false, false, false, false, false, false, false, false]);
 346         }
 347 }
 348
 349 var redraw_arrows = function() {
 350         for (var i = 0; i < arrows.length; ++i) {
 351                 position_arrow(arrows[i]);
 352         }
 353 }
 354
 355 /** @param {!number} x
 356  * @return {!number}
 357  */
 358 var sign = function(x) {
 359         if (x > 0) {
 360                 return 1;
 361         } else if (x < 0) {
 362                 return -1;
 363         } else {
 364                 return 0;
 365         }
 366 }
 367
 368 /** See if drawing this arrow on the board would cause unduly amount of confusion.
 369  * @param {!string} from The square the arrow is from (e.g. e4).
 370  * @param {!string} to The square the arrow is to (e.g. e4).
 371  * @return {boolean}
 372  */
 373 var interfering_arrow = function(from, to) {
 374         var from_col = from.charCodeAt(0) - "a1".charCodeAt(0);
 375         var from_row = from.charCodeAt(1) - "a1".charCodeAt(1);
 376         var to_col   = to.charCodeAt(0) - "a1".charCodeAt(0);
 377         var to_row   = to.charCodeAt(1) - "a1".charCodeAt(1);
 378
 379         occupied_by_arrows[from_row][from_col] = true;
 380
 381         // Knight move: Just check that we haven't been at the destination before.
 382         if ((Math.abs(to_col - from_col) == 2 && Math.abs(to_row - from_row) == 1) ||
 383             (Math.abs(to_col - from_col) == 1 && Math.abs(to_row - from_row) == 2)) {
 384                 return occupied_by_arrows[to_row][to_col];
 385         }
 386
 387         // Sliding piece: Check if anything except the from-square is seen before.
 388         var dx = sign(to_col - from_col);
 389         var dy = sign(to_row - from_row);
 390         var x = from_col;
 391         var y = from_row;
 392         do {
 393                 x += dx;
 394                 y += dy;
 395                 if (occupied_by_arrows[y][x]) {
 396                         return true;
 397                 }
 398                 occupied_by_arrows[y][x] = true;
 399         } while (x != to_col || y != to_row);
 400
 401         return false;
 402 }
 403
 404 /** Find a point along the coordinate system given by the given line,
 405  * <t> units forward from the start of the line, <u> units to the right of it.
 406  * @param {!number} x1
 407  * @param {!number} x2
 408  * @param {!number} y1
 409  * @param {!number} y2
 410  * @param {!number} t
 411  * @param {!number} u
 412  * @return {!string} The point in "x y" form, suitable for SVG paths.
 413  */
 414 var point_from_start = function(x1, y1, x2, y2, t, u) {
 415         var dx = x2 - x1;
 416         var dy = y2 - y1;
 417
 418         var norm = 1.0 / Math.sqrt(dx * dx + dy * dy);
 419         dx *= norm;
 420         dy *= norm;
 421
 422         var x = x1 + dx * t + dy * u;
 423         var y = y1 + dy * t - dx * u;
 424         return x + " " + y;
 425 }
 426
 427 /** Find a point along the coordinate system given by the given line,
 428  * <t> units forward from the end of the line, <u> units to the right of it.
 429  * @param {!number} x1
 430  * @param {!number} x2
 431  * @param {!number} y1
 432  * @param {!number} y2
 433  * @param {!number} t
 434  * @param {!number} u
 435  * @return {!string} The point in "x y" form, suitable for SVG paths.
 436  */
 437 var point_from_end = function(x1, y1, x2, y2, t, u) {
 438         var dx = x2 - x1;
 439         var dy = y2 - y1;
 440
 441         var norm = 1.0 / Math.sqrt(dx * dx + dy * dy);
 442         dx *= norm;
 443         dy *= norm;
 444
 445         var x = x2 + dx * t + dy * u;
 446         var y = y2 + dy * t - dx * u;
 447         return x + " " + y;
 448 }
 449
 450 var position_arrow = function(arrow) {
 451         if (arrow.svg) {
 452                 if (arrow.svg.parentElement) {
 453                         arrow.svg.parentElement.removeChild(arrow.svg);
 454                 }
 455                 delete arrow.svg;
 456         }
 457         if (current_display_line !== null && !current_display_line_is_history) {
 458                 return;
 459         }
 460
 461         var pos = $(".square-a8").position();
 462
 463         var zoom_factor = $("#board").width() / 400.0;
 464         var line_width = arrow.line_width * zoom_factor;
 465         var arrow_size = arrow.arrow_size * zoom_factor;
 466
 467         var square_width = $(".square-a8").width();
 468         var from_y = (7 - arrow.from_row + 0.5)*square_width;
 469         var to_y = (7 - arrow.to_row + 0.5)*square_width;
 470         var from_x = (arrow.from_col + 0.5)*square_width;
 471         var to_x = (arrow.to_col + 0.5)*square_width;
 472
 473         var SVG_NS = "http://www.w3.org/2000/svg";
 474         var XHTML_NS = "http://www.w3.org/1999/xhtml";
 475         var svg = document.createElementNS(SVG_NS, "svg");
 476         svg.setAttribute("width", /** @type{number} */ ($("#board").width()));
 477         svg.setAttribute("height", /** @type{number} */ ($("#board").height()));
 478         svg.setAttribute("style", "position: absolute");
 479         svg.setAttribute("position", "absolute");
 480         svg.setAttribute("version", "1.1");
 481         svg.setAttribute("class", "c1");
 482         svg.setAttribute("xmlns", XHTML_NS);
 483
 484         var x1 = from_x;
 485         var y1 = from_y;
 486         var x2 = to_x;
 487         var y2 = to_y;
 488
 489         // Draw the line.
 490         var outline = document.createElementNS(SVG_NS, "path");
 491         outline.setAttribute("d", "M " + point_from_start(x1, y1, x2, y2, arrow_size / 2, 0) + " L " + point_from_end(x1, y1, x2, y2, -arrow_size / 2, 0));
 492         outline.setAttribute("xmlns", XHTML_NS);
 493         outline.setAttribute("stroke", "#666");
 494         outline.setAttribute("stroke-width", line_width + 2);
 495         outline.setAttribute("fill", "none");
 496         svg.appendChild(outline);
 497
 498         var path = document.createElementNS(SVG_NS, "path");
 499         path.setAttribute("d", "M " + point_from_start(x1, y1, x2, y2, arrow_size / 2, 0) + " L " + point_from_end(x1, y1, x2, y2, -arrow_size / 2, 0));
 500         path.setAttribute("xmlns", XHTML_NS);
 501         path.setAttribute("stroke", arrow.fg_color);
 502         path.setAttribute("stroke-width", line_width);
 503         path.setAttribute("fill", "none");
 504         svg.appendChild(path);
 505
 506         // Then the arrow head.
 507         var head = document.createElementNS(SVG_NS, "path");
 508         head.setAttribute("d",
 509                 "M " +  point_from_end(x1, y1, x2, y2, 0, 0) +
 510                 " L " + point_from_end(x1, y1, x2, y2, -arrow_size, -arrow_size / 2) +
 511                 " L " + point_from_end(x1, y1, x2, y2, -arrow_size * .623, 0.0) +
 512                 " L " + point_from_end(x1, y1, x2, y2, -arrow_size, arrow_size / 2) +
 513                 " L " + point_from_end(x1, y1, x2, y2, 0, 0));
 514         head.setAttribute("xmlns", XHTML_NS);
 515         head.setAttribute("stroke", "#000");
 516         head.setAttribute("stroke-width", "1");
 517         head.setAttribute("fill", arrow.fg_color);
 518         svg.appendChild(head);
 519
 520         $(svg).css({ top: pos.top, left: pos.left, 'pointer-events': 'none' });
 521         document.body.appendChild(svg);
 522         arrow.svg = svg;
 523 }
 524
 525 /**
 526  * @param {!string} from_square
 527  * @param {!string} to_square
 528  * @param {!string} fg_color
 529  * @param {number} line_width
 530  * @param {number} arrow_size
 531  */
 532 var create_arrow = function(from_square, to_square, fg_color, line_width, arrow_size) {
 533         var from_col = from_square.charCodeAt(0) - "a1".charCodeAt(0);
 534         var from_row = from_square.charCodeAt(1) - "a1".charCodeAt(1);
 535         var to_col   = to_square.charCodeAt(0) - "a1".charCodeAt(0);
 536         var to_row   = to_square.charCodeAt(1) - "a1".charCodeAt(1);
 537
 538         // Create arrow.
 539         var arrow = {
 540                 from_col: from_col,
 541                 from_row: from_row,
 542                 to_col: to_col,
 543                 to_row: to_row,
 544                 line_width: line_width,
 545                 arrow_size: arrow_size,
 546                 fg_color: fg_color
 547         };
 548
 549         position_arrow(arrow);
 550         arrows.push(arrow);
 551 }
 552
 553 // Note: invert is ignored.
 554 var compare_by_sort_key = function(refutation_lines, invert, a, b) {
 555         var ska = refutation_lines[a]['sort_key'];
 556         var skb = refutation_lines[b]['sort_key'];
 557         if (ska < skb) return -1;
 558         if (ska > skb) return 1;
 559         return 0;
 560 };
 561
 562 var compare_by_score = function(refutation_lines, invert, a, b) {
 563         var sa = compute_score_sort_key(refutation_lines[b]['score'], refutation_lines[b]['depth'], invert);
 564         var sb = compute_score_sort_key(refutation_lines[a]['score'], refutation_lines[a]['depth'], invert);
 565         return sa - sb;
 566 }
 567
 568 /**
 569  * Fake multi-PV using the refutation lines. Find all “relevant” moves,
 570  * sorted by quality, descending.
 571  *
 572  * @param {!Object} data
 573  * @param {number} margin The maximum number of centipawns worse than the
 574  *     best move can be and still be included.
 575  * @param {boolean} margin Whether black is to play.
 576  * @return {Array.<string>} The UCI representation (e.g. e1g1) of all
 577  *     moves, in score order.
 578  */
 579 var find_nonstupid_moves = function(data, margin, invert) {
 580         // First of all, if there are any moves that are more than 0.5 ahead of
 581         // the primary move, the refutation lines are probably bunk, so just
 582         // kill them all.
 583         var best_score = undefined;
 584         var pv_score = undefined;
 585         for (var move in data['refutation_lines']) {
 586                 var line = data['refutation_lines'][move];
 587                 var score = compute_score_sort_key(line['score'], line['depth'], invert);
 588                 if (move == data['pv_uci'][0]) {
 589                         pv_score = score;
 590                 }
 591                 if (best_score === undefined || score > best_score) {
 592                         best_score = score;
 593                 }
 594                 if (line['depth'] < 8) {
 595                         return [];
 596                 }
 597         }
 598
 599         if (best_score - pv_score > 50) {
 600                 return [];
 601         }
 602
 603         // Now find all moves that are within “margin” of the best score.
 604         // The PV move will always be first.
 605         var moves = [];
 606         for (var move in data['refutation_lines']) {
 607                 var line = data['refutation_lines'][move];
 608                 var score = compute_score_sort_key(line['score'], line['depth'], invert);
 609                 if (move != data['pv_uci'][0] && best_score - score <= margin) {
 610                         moves.push(move);
 611                 }
 612         }
 613         moves = moves.sort(function(a, b) { return compare_by_score(data['refutation_lines'], data['position']['toplay'] === 'B', a, b) });
 614         moves.unshift(data['pv_uci'][0]);
 615
 616         return moves;
 617 }
 618
 619 /**
 620  * @param {number} x
 621  * @return {!string}
 622  */
 623 var thousands = function(x) {
 624         return String(x).split('').reverse().join('').replace(/(\d{3}\B)/g, '$1,').split('').reverse().join('');
 625 }
 626
 627 /**
 628  * @param {!string} start_fen
 629  * @param {Array.<string>} pretty_pv
 630  * @param {number} move_num
 631  * @param {!string} toplay
 632  * @param {Array<{ first_move: integer, score: Object }>} scores
 633  * @param {number} start_display_move_num
 634  * @param {number=} opt_limit
 635  * @param {boolean=} opt_showlast
 636  */
 637 var add_pv = function(start_fen, pretty_pv, move_num, toplay, scores, start_display_move_num, opt_limit, opt_showlast) {
 638         display_lines.push({
 639                 start_fen: start_fen,
 640                 pretty_pv: pretty_pv,
 641                 move_num: parseInt(move_num),
 642                 toplay: toplay,
 643                 scores: scores,
 644                 start_display_move_num: start_display_move_num
 645         });
 646         return print_pv(display_lines.length - 1, opt_limit, opt_showlast);
 647 }
 648
 649 /**
 650  * @param {number} line_num
 651  * @param {number=} opt_limit If set, show at most this number of moves.
 652  * @param {boolean=} opt_showlast If limit is set, show the last moves instead of the first ones.
 653  */
 654 var print_pv = function(line_num, opt_limit, opt_showlast) {
 655         var display_line = display_lines[line_num];
 656         var pretty_pv = display_line.pretty_pv;
 657         var move_num = display_line.move_num;
 658         var toplay = display_line.toplay;
 659
 660         // Truncate PV at the start if needed.
 661         var start_display_move_num = display_line.start_display_move_num;
 662         if (start_display_move_num > 0) {
 663                 pretty_pv = pretty_pv.slice(start_display_move_num);
 664                 var to_add = start_display_move_num;
 665                 if (toplay === 'B') {
 666                         ++move_num;
 667                         toplay = 'W';
 668                         --to_add;
 669                 }
 670                 if (to_add % 2 == 1) {
 671                         toplay = 'B';
 672                         --to_add;
 673                 }
 674                 move_num += to_add / 2;
 675         }
 676
 677         var pv = '';
 678         var i = 0;
 679         if (opt_limit && opt_showlast && pretty_pv.length > opt_limit) {
 680                 // Truncate the PV at the beginning (instead of at the end).
 681                 // We assume here that toplay is 'W'. We also assume that if
 682                 // opt_showlast is set, then it is the history, and thus,
 683                 // the UI should be to expand the history.
 684                 pv = '(<a class="move" href="javascript:collapse_history(false)">…</a>) ';
 685                 i = pretty_pv.length - opt_limit;
 686                 if (i % 2 == 1) {
 687                         ++i;
 688                 }
 689                 move_num += i / 2;
 690         } else if (toplay == 'B' && pretty_pv.length > 0) {
 691                 var move = "<a class=\"move\" id=\"automove" + line_num + "-0\" href=\"javascript:show_line(" + line_num + ", " + 0 + ");\">" + pretty_pv[0] + "</a>";
 692                 pv = move_num + '. … ' + move;
 693                 toplay = 'W';
 694                 ++i;
 695                 ++move_num;
 696         }
 697         for ( ; i < pretty_pv.length; ++i) {
 698                 var move = "<a class=\"move\" id=\"automove" + line_num + "-" + i + "\" href=\"javascript:show_line(" + line_num + ", " + i + ");\">" + pretty_pv[i] + "</a>";
 699
 700                 if (toplay == 'W') {
 701                         if (i > opt_limit && !opt_showlast) {
 702                                 return pv + ' (…)';
 703                         }
 704                         if (pv != '') {
 705                                 pv += ' ';
 706                         }
 707                         pv += move_num + '. ' + move;
 708                         ++move_num;
 709                         toplay = 'B';
 710                 } else {
 711                         pv += ' ' + move;
 712                         toplay = 'W';
 713                 }
 714         }
 715         return pv;
 716 }
 717
 718 /** Update the highlighted to/from squares on the board.
 719  * Based on the global "highlight_from" and "highlight_to" variables.
 720  */
 721 var update_board_highlight = function() {
 722         $("#board").find('.square-55d63').removeClass('nonuglyhighlight');
 723         if ((current_display_line === null || current_display_line_is_history) &&
 724             highlight_from !== undefined && highlight_to !== undefined) {
 725                 $("#board").find('.square-' + highlight_from).addClass('nonuglyhighlight');
 726                 $("#board").find('.square-' + highlight_to).addClass('nonuglyhighlight');
 727         }
 728 }
 729
 730 var update_history = function() {
 731         if (display_lines[0] === null || display_lines[0].pretty_pv.length == 0) {
 732                 $("#history").html("No history");
 733         } else if (truncate_display_history) {
 734                 $("#history").html(print_pv(0, 8, true));
 735         } else {
 736                 $("#history").html(
 737                         '(<a class="move" href="javascript:collapse_history(true)">collapse</a>) ' +
 738                         print_pv(0));
 739         }
 740 }
 741
 742 /**
 743  * @param {!boolean} truncate_history
 744  */
 745 var collapse_history = function(truncate_history) {
 746         truncate_display_history = truncate_history;
 747         update_history();
 748 }
 749 window['collapse_history'] = collapse_history;
 750
 751 /** Update the HTML display of multi-PV from the global "refutation_lines".
 752  *
 753  * Also recreates the global "display_lines".
 754  */
 755 var update_refutation_lines = function() {
 756         if (base_fen === null) {
 757                 return;
 758         }
 759         if (display_lines.length > 2) {
 760                 // Truncate so that only the history and PV is left.
 761                 display_lines = [ display_lines[0], display_lines[1] ];
 762         }
 763         var tbl = $("#refutationlines");
 764         tbl.empty();
 765
 766         // Find out where the lines start from.
 767         var base_line = [];
 768         var base_scores = [];
 769         var start_display_move_num = 0;
 770         if (hash_refutation_lines) {
 771                 base_line = current_display_line.pretty_pv.slice(0, current_display_move + 1);
 772                 base_scores = current_display_line.scores;
 773                 start_display_move_num = base_line.length;
 774         }
 775
 776         var moves = [];
 777         for (var move in refutation_lines) {
 778                 moves.push(move);
 779         }
 780
 781         var invert = (toplay === 'B');
 782         if (current_display_line && current_display_move % 2 == 0) {
 783                 invert = !invert;
 784         }
 785         var compare = sort_refutation_lines_by_score ? compare_by_score : compare_by_sort_key;
 786         moves = moves.sort(function(a, b) { return compare(refutation_lines, invert, a, b) });
 787         for (var i = 0; i < moves.length; ++i) {
 788                 var line = refutation_lines[moves[i]];
 789
 790                 var tr = document.createElement("tr");
 791
 792                 var move_td = document.createElement("td");
 793                 tr.appendChild(move_td);
 794                 $(move_td).addClass("move");
 795
 796                 var scores = base_scores.concat([{ first_move: start_display_move_num, score: line['score'] }]);
 797
 798                 if (line['pv_pretty'].length == 0) {
 799                         // Not found, so just make a one-move PV.
 800                         var move = "<a class=\"move\" href=\"javascript:show_line(" + display_lines.length + ", " + 0 + ");\">" + line['pretty_move'] + "</a>";
 801                         $(move_td).html(move);
 802                         var score_td = document.createElement("td");
 803
 804                         $(score_td).addClass("score");
 805                         $(score_td).text("—");
 806                         tr.appendChild(score_td);
 807
 808                         var depth_td = document.createElement("td");
 809                         tr.appendChild(depth_td);
 810                         $(depth_td).addClass("depth");
 811                         $(depth_td).text("—");
 812
 813                         var pv_td = document.createElement("td");
 814                         tr.appendChild(pv_td);
 815                         $(pv_td).addClass("pv");
 816                         $(pv_td).html(add_pv(base_fen, base_line.concat([ line['pretty_move'] ]), move_num, toplay, scores, start_display_move_num));
 817
 818                         tbl.append(tr);
 819                         continue;
 820                 }
 821
 822                 var move = "<a class=\"move\" href=\"javascript:show_line(" + display_lines.length + ", " + 0 + ");\">" + line['pretty_move'] + "</a>";
 823                 $(move_td).html(move);
 824
 825                 var score_td = document.createElement("td");
 826                 tr.appendChild(score_td);
 827                 $(score_td).addClass("score");
 828                 $(score_td).text(format_short_score(line['score']));
 829
 830                 var depth_td = document.createElement("td");
 831                 tr.appendChild(depth_td);
 832                 $(depth_td).addClass("depth");
 833                 if (line['depth'] && line['depth'] >= 0) {
 834                         $(depth_td).text("d" + line['depth']);
 835                 } else {
 836                         $(depth_td).text("—");
 837                 }
 838
 839                 var pv_td = document.createElement("td");
 840                 tr.appendChild(pv_td);
 841                 $(pv_td).addClass("pv");
 842                 $(pv_td).html(add_pv(base_fen, base_line.concat(line['pv_pretty']), move_num, toplay, scores, start_display_move_num, 10));
 843
 844                 tbl.append(tr);
 845         }
 846
 847         // Make one of the links clickable and the other nonclickable.
 848         if (sort_refutation_lines_by_score) {
 849                 $("#sortbyscore0").html("<a href=\"javascript:resort_refutation_lines(false)\">Move</a>");
 850                 $("#sortbyscore1").html("<strong>Score</strong>");
 851         } else {
 852                 $("#sortbyscore0").html("<strong>Move</strong>");
 853                 $("#sortbyscore1").html("<a href=\"javascript:resort_refutation_lines(true)\">Score</a>");
 854         }
 855
 856         // Update the move highlight, as we've rewritten all the HTML.
 857         update_move_highlight();
 858 }
 859
 860 /**
 861  * Create a Chess.js board object, containing the given position plus the given moves,
 862  * up to the given limit.
 863  *
 864  * @param {?string} fen
 865  * @param {Array.<string>} moves
 866  * @param {number} last_move
 867  */
 868 var chess_from = function(fen, moves, last_move) {
 869         var hiddenboard = new Chess();
 870         if (fen !== null) {
 871                 hiddenboard.load(fen);
 872         }
 873         for (var i = 0; i <= last_move; ++i) {
 874                 if (moves[i] === '0-0') {
 875                         hiddenboard.move('O-O');
 876                 } else if (moves[i] === '0-0-0') {
 877                         hiddenboard.move('O-O-O');
 878                 } else {
 879                         hiddenboard.move(moves[i]);
 880                 }
 881         }
 882         return hiddenboard;
 883 }
 884
 885 var update_game_list = function(games) {
 886         $("#games").text("");
 887         if (games === null) {
 888                 return;
 889         }
 890
 891         var games_div = document.getElementById('games');
 892         for (var game_num = 0; game_num < games.length; ++game_num) {
 893                 var game = games[game_num];
 894                 var game_span = document.createElement("span");
 895                 game_span.setAttribute("class", "game");
 896
 897                 var game_name = document.createTextNode(game['name']);
 898                 if (game['url'] === backend_url) {
 899                         // This game.
 900                         game_span.appendChild(game_name);
 901
 902                         var score;
 903                         if (current_analysis_data['position']['result']) {
 904                                 score = " (" + current_analysis_data['position']['result'] + ")";
 905                         } else {
 906                                 score = " (" + format_short_score(current_analysis_data['score']) + ")";
 907                         }
 908                         game_span.appendChild(document.createTextNode(score));
 909                 } else {
 910                         // Some other game.
 911                         var game_a = document.createElement("a");
 912                         game_a.setAttribute("href", "#" + game['id']);
 913                         game_a.appendChild(game_name);
 914                         game_span.appendChild(game_a);
 915
 916                         var score;
 917                         if (game['result']) {
 918                                 score = " (" + game['result'] + ")";
 919                         } else {
 920                                 score = " (" + format_short_score(game['score']) + ")";
 921                         }
 922                         game_span.appendChild(document.createTextNode(score));
 923                 }
 924
 925                 games_div.appendChild(game_span);
 926         }
 927 }
 928
 929 /**
 930  * Try to find a running game that matches with the current hash,
 931  * and switch to it if we're not already displaying it.
 932  */
 933 var possibly_switch_game_from_hash = function() {
 934         if (current_games === null) {
 935                 return;
 936         }
 937
 938         var hash = window.location.hash.replace(/^#/,'');
 939         for (var i = 0; i < current_games.length; ++i) {
 940                 if (current_games[i]['id'] === hash) {
 941                         if (backend_url !== current_games[i]['url']) {
 942                                 switch_backend(current_games[i]['url'], current_games[i]['hashurl']);
 943                         }
 944                         return;
 945                 }
 946         }
 947 }
 948
 949 /** Update all the HTML on the page, based on current global state.
 950  */
 951 var update_board = function() {
 952         var data = displayed_analysis_data || current_analysis_data;
 953         var current_data = current_analysis_data;  // Convenience alias.
 954
 955         display_lines = [];
 956
 957         // Print the history. This is pretty much the only thing that's
 958         // unconditionally taken from current_data (we're not interested in
 959         // historic history).
 960         if (current_data['position']['pretty_history']) {
 961                 add_pv('start', current_data['position']['pretty_history'], 1, 'W', null, 0, 8, true);
 962         } else {
 963                 display_lines.push(null);
 964         }
 965         update_history();
 966
 967         // Games currently in progress, if any.
 968         if (current_data['games']) {
 969                 current_games = current_data['games'];
 970                 possibly_switch_game_from_hash();
 971         } else {
 972                 current_games = null;
 973         }
 974         update_game_list(current_games);
 975
 976         // The headline. Names are always fetched from current_data;
 977         // the rest can depend a bit.
 978         var headline;
 979         if (current_data &&
 980             current_data['position']['player_w'] && current_data['position']['player_b']) {
 981                 headline = current_data['position']['player_w'] + '–' +
 982                         current_data['position']['player_b'] + ', analysis';
 983         } else {
 984                 headline = 'Analysis';
 985         }
 986
 987         // Credits, where applicable. Note that we don't want the footer to change a lot
 988         // when e.g. viewing history, so if any of these changed during the game,
 989         // use the current one still.
 990         if (current_data['using_lomonosov']) {
 991                 $("#lomonosov").show();
 992         } else {
 993                 $("#lomonosov").hide();
 994         }
 995
 996         // Credits: The engine name/version.
 997         if (current_data['engine'] && current_data['engine']['name'] !== null) {
 998                 $("#engineid").text(current_data['engine']['name']);
 999         }
1000
1001         // Credits: The engine URL.
1002         if (current_data['engine'] && current_data['engine']['url']) {
1003                 $("#engineid").attr("href", current_data['engine']['url']);
1004         } else {
1005                 $("#engineid").removeAttr("href");
1006         }
1007
1008         // Credits: Engine details.
1009         if (current_data['engine'] && current_data['engine']['details']) {
1010                 $("#enginedetails").text(" (" + current_data['engine']['details'] + ")");
1011         } else {
1012                 $("#enginedetails").text("");
1013         }
1014
1015         // Credits: Move source, possibly with URL.
1016         if (current_data['move_source'] && current_data['move_source_url']) {
1017                 $("#movesource").text("Moves provided by ");
1018                 var movesource_a = document.createElement("a");
1019                 movesource_a.setAttribute("href", current_data['move_source_url']);
1020                 var movesource_text = document.createTextNode(current_data['move_source']);
1021                 movesource_a.appendChild(movesource_text);
1022                 var movesource_period = document.createTextNode(".");
1023                 document.getElementById("movesource").appendChild(movesource_a);
1024                 document.getElementById("movesource").appendChild(movesource_period);
1025         } else if (current_data['move_source']) {
1026                 $("#movesource").text("Moves provided by " + current_data['move_source'] + ".");
1027         } else {
1028                 $("#movesource").text("");
1029         }
1030
1031         var last_move;
1032         if (displayed_analysis_data) {
1033                 // Displaying some non-current position, pick out the last move
1034                 // from the history. This will work even if the fetch failed.
1035                 last_move = format_halfmove_with_number(
1036                         current_display_line.pretty_pv[current_display_move],
1037                         current_display_move + 1);
1038                 headline += ' after ' + last_move;
1039         } else if (data['position']['last_move'] !== 'none') {
1040                 last_move = format_move_with_number(
1041                         data['position']['last_move'],
1042                         data['position']['move_num'],
1043                         data['position']['toplay'] == 'W');
1044                 headline += ' after ' + last_move;
1045         } else {
1046                 last_move = null;
1047         }
1048         $("#headline").text(headline);
1049
1050         // The <title> contains a very brief headline.
1051         var title_elems = [];
1052         if (data['position'] && data['position']['result']) {
1053                 title_elems.push(data['position']['result']);
1054         } else if (data['score']) {
1055                 title_elems.push(format_short_score(data['score']));
1056         }
1057         if (last_move !== null) {
1058                 title_elems.push(last_move);
1059         }
1060
1061         if (title_elems.length != 0) {
1062                 document.title = '(' + title_elems.join(', ') + ') analysis.sesse.net';
1063         } else {
1064                 document.title = 'analysis.sesse.net';
1065         }
1066
1067         // The last move (shown by highlighting the from and to squares).
1068         if (data['position'] && data['position']['last_move_uci']) {
1069                 highlight_from = data['position']['last_move_uci'].substr(0, 2);
1070                 highlight_to = data['position']['last_move_uci'].substr(2, 2);
1071         } else if (current_display_line_is_history && current_display_move >= 0) {
1072                 // We don't have historic analysis for this position, but we
1073                 // can reconstruct what the last move was by just replaying
1074                 // from the start.
1075                 var hiddenboard = chess_from(null, current_display_line.pretty_pv, current_display_move);
1076                 var moves = hiddenboard.history({ verbose: true });
1077                 var last_move = moves.pop();
1078                 highlight_from = last_move.from;
1079                 highlight_to = last_move.to;
1080         } else {
1081                 highlight_from = highlight_to = undefined;
1082         }
1083         update_board_highlight();
1084
1085         if (data['failed']) {
1086                 $("#score").text("No analysis for this move");
1087                 $("#pvtitle").text("PV:");
1088                 $("#pv").empty();
1089                 $("#searchstats").html("&nbsp;");
1090                 $("#refutationlines").empty();
1091                 $("#whiteclock").empty();
1092                 $("#blackclock").empty();
1093                 refutation_lines = [];
1094                 update_refutation_lines();
1095                 clear_arrows();
1096                 update_displayed_line();
1097                 update_move_highlight();
1098                 return;
1099         }
1100
1101         update_clock();
1102
1103         // The score.
1104         if (current_display_line && !current_display_line_is_history) {
1105                 if (current_display_line.scores && current_display_line.scores.length > 0) {
1106                         var score;
1107                         for (var i = 0; i < current_display_line.scores.length; ++i) {
1108                                 if (current_display_move < current_display_line.scores[i].first_move) {
1109                                         break;
1110                                 }
1111                                 score = current_display_line.scores[i].score;
1112                         }
1113                         $("#score").text(format_long_score(score));
1114                 } else {
1115                         $("#score").text("No score for this move");
1116                 }
1117         } else if (data['score']) {
1118                 $("#score").text(format_long_score(data['score']));
1119         }
1120
1121         // The search stats.
1122         if (data['searchstats']) {
1123                 $("#searchstats").html(data['searchstats']);
1124         } else if (data['tablebase'] == 1) {
1125                 $("#searchstats").text("Tablebase result");
1126         } else if (data['nodes'] && data['nps'] && data['depth']) {
1127                 var stats = thousands(data['nodes']) + ' nodes, ' + thousands(data['nps']) + ' nodes/sec, depth ' + data['depth'] + ' ply';
1128                 if (data['seldepth']) {
1129                         stats += ' (' + data['seldepth'] + ' selective)';
1130                 }
1131                 if (data['tbhits'] && data['tbhits'] > 0) {
1132                         if (data['tbhits'] == 1) {
1133                                 stats += ', one Syzygy hit';
1134                         } else {
1135                                 stats += ', ' + thousands(data['tbhits']) + ' Syzygy hits';
1136                         }
1137                 }
1138
1139                 $("#searchstats").text(stats);
1140         } else {
1141                 $("#searchstats").text("");
1142         }
1143
1144         // Update the board itself.
1145         base_fen = data['position']['fen'];
1146         update_displayed_line();
1147
1148         // Print the PV.
1149         $("#pvtitle").text("PV:");
1150
1151         var scores = [{ first_move: 0, score: data['score'] }];
1152         $("#pv").html(add_pv(data['position']['fen'], data['pv_pretty'], data['position']['move_num'], data['position']['toplay'], scores, 0));
1153
1154         // Update the PV arrow.
1155         clear_arrows();
1156         if (data['pv_uci'].length >= 1) {
1157                 // draw a continuation arrow as long as it's the same piece
1158                 for (var i = 0; i < data['pv_uci'].length; i += 2) {
1159                         var from = data['pv_uci'][i].substr(0, 2);
1160                         var to = data['pv_uci'][i].substr(2,4);
1161                         if ((i >= 2 && from != data['pv_uci'][i - 2].substr(2, 2)) ||
1162                              interfering_arrow(from, to)) {
1163                                 break;
1164                         }
1165                         create_arrow(from, to, '#f66', 6, 20);
1166                 }
1167
1168                 var alt_moves = find_nonstupid_moves(data, 30, data['position']['toplay'] === 'B');
1169                 for (var i = 1; i < alt_moves.length && i < 3; ++i) {
1170                         create_arrow(alt_moves[i].substr(0, 2),
1171                                      alt_moves[i].substr(2, 2), '#f66', 1, 10);
1172                 }
1173         }
1174
1175         // See if all semi-reasonable moves have only one possible response.
1176         if (data['pv_uci'].length >= 2) {
1177                 var nonstupid_moves = find_nonstupid_moves(data, 300, data['position']['toplay'] === 'B');
1178                 var response = data['pv_uci'][1];
1179                 for (var i = 0; i < nonstupid_moves.length; ++i) {
1180                         if (nonstupid_moves[i] == data['pv_uci'][0]) {
1181                                 // ignore the PV move for refutation lines.
1182                                 continue;
1183                         }
1184                         if (!data['refutation_lines'] ||
1185                             !data['refutation_lines'][nonstupid_moves[i]] ||
1186                             !data['refutation_lines'][nonstupid_moves[i]]['pv_uci'] ||
1187                             data['refutation_lines'][nonstupid_moves[i]]['pv_uci'].length < 1) {
1188                                 // Incomplete PV, abort.
1189                                 response = undefined;
1190                                 break;
1191                         }
1192                         var this_response = data['refutation_lines'][nonstupid_moves[i]]['pv_uci'][1];
1193                         if (response !== this_response) {
1194                                 // Different response depending on lines, abort.
1195                                 response = undefined;
1196                                 break;
1197                         }
1198                 }
1199
1200                 if (nonstupid_moves.length > 0 && response !== undefined) {
1201                         create_arrow(response.substr(0, 2),
1202                                      response.substr(2, 2), '#66f', 6, 20);
1203                 }
1204         }
1205
1206         // Update the refutation lines.
1207         base_fen = data['position']['fen'];
1208         move_num = parseInt(data['position']['move_num']);
1209         toplay = data['position']['toplay'];
1210         refutation_lines = hash_refutation_lines || data['refutation_lines'];
1211         update_refutation_lines();
1212
1213         // Update the sparkline last, since its size depends on how everything else reflowed.
1214         update_sparkline(data);
1215 }
1216
1217 var update_sparkline = function(data) {
1218         if (data && data['score_history']) {
1219                 var first_move_num = undefined;
1220                 for (var halfmove_num in data['score_history']) {
1221                         halfmove_num = parseInt(halfmove_num);
1222                         if (first_move_num === undefined || halfmove_num < first_move_num) {
1223                                 first_move_num = halfmove_num;
1224                         }
1225                 }
1226                 if (first_move_num !== undefined) {
1227                         var last_move_num = data['position']['move_num'] * 2 - 3;
1228                         if (data['position']['toplay'] === 'B') {
1229                                 ++last_move_num;
1230                         }
1231
1232                         // Possibly truncate some moves if we don't have enough width.
1233                         // FIXME: Sometimes width() for #scorecontainer (and by extent,
1234                         // #scoresparkcontainer) on Chrome for mobile seems to start off
1235                         // at something very small, and then suddenly snap back into place.
1236                         // Figure out why.
1237                         var max_moves = Math.floor($("#scoresparkcontainer").width() / 5) - 5;
1238                         if (last_move_num - first_move_num > max_moves) {
1239                                 first_move_num = last_move_num - max_moves;
1240                         }
1241
1242                         var min_score = -100;
1243                         var max_score = 100;
1244                         var last_score = null;
1245                         var scores = [];
1246                         for (var halfmove_num = first_move_num; halfmove_num <= last_move_num; ++halfmove_num) {
1247                                 if (data['score_history'][halfmove_num]) {
1248                                         var score = compute_plot_score(data['score_history'][halfmove_num]);
1249                                         last_score = score;
1250                                         if (score < min_score) min_score = score;
1251                                         if (score > max_score) max_score = score;
1252                                 }
1253                                 scores.push(last_score);
1254                         }
1255                         if (data['score']) {
1256                                 scores.push(compute_plot_score(data['score']));
1257                         }
1258                         // FIXME: at some widths, calling sparkline() seems to push
1259                         // #scorecontainer under the board.
1260                         $("#scorespark").sparkline(scores, {
1261                                 type: 'bar',
1262                                 zeroColor: 'gray',
1263                                 chartRangeMin: min_score,
1264                                 chartRangeMax: max_score,
1265                                 tooltipFormatter: function(sparkline, options, fields) {
1266                                         return format_tooltip(data, fields[0].offset + first_move_num);
1267                                 }
1268                         });
1269                 } else {
1270                         $("#scorespark").text("");
1271                 }
1272         } else {
1273                 $("#scorespark").text("");
1274         }
1275 }
1276
1277 /**
1278  * @param {number} num_viewers
1279  */
1280 var update_num_viewers = function(num_viewers) {
1281         if (num_viewers === null) {
1282                 $("#numviewers").text("");
1283         } else if (num_viewers == 1) {
1284                 $("#numviewers").text("You are the only current viewer");
1285         } else {
1286                 $("#numviewers").text(num_viewers + " current viewers");
1287         }
1288 }
1289
1290 var update_clock = function() {
1291         clearTimeout(clock_timer);
1292
1293         var data = displayed_analysis_data || current_analysis_data;
1294         if (data['position']) {
1295                 var result = data['position']['result'];
1296                 if (result === '1-0') {
1297                         $("#whiteclock").text("1");
1298                         $("#blackclock").text("0");
1299                         $("#whiteclock").removeClass("running-clock");
1300                         $("#blackclock").removeClass("running-clock");
1301                         return;
1302                 }
1303                 if (result === '1/2-1/2') {
1304                         $("#whiteclock").text("1/2");
1305                         $("#blackclock").text("1/2");
1306                         $("#whiteclock").removeClass("running-clock");
1307                         $("#blackclock").removeClass("running-clock");
1308                         return;
1309                 }
1310                 if (result === '0-1') {
1311                         $("#whiteclock").text("0");
1312                         $("#blackclock").text("1");
1313                         $("#whiteclock").removeClass("running-clock");
1314                         $("#blackclock").removeClass("running-clock");
1315                         return;
1316                 }
1317         }
1318
1319         var white_clock_ms = null;
1320         var black_clock_ms = null;
1321         var show_seconds = false;
1322
1323         // Static clocks.
1324         if (data['position'] &&
1325             data['position']['white_clock'] &&
1326             data['position']['black_clock']) {
1327                 white_clock_ms = data['position']['white_clock'] * 1000;
1328                 black_clock_ms = data['position']['black_clock'] * 1000;
1329         }
1330
1331         // Dynamic clock (only one, obviously).
1332         var color;
1333         if (data['position']['white_clock_target']) {
1334                 color = "white";
1335                 $("#whiteclock").addClass("running-clock");
1336                 $("#blackclock").removeClass("running-clock");
1337         } else if (data['position']['black_clock_target']) {
1338                 color = "black";
1339                 $("#whiteclock").removeClass("running-clock");
1340                 $("#blackclock").addClass("running-clock");
1341         } else {
1342                 $("#whiteclock").removeClass("running-clock");
1343                 $("#blackclock").removeClass("running-clock");
1344         }
1345         var remaining_ms;
1346         if (color) {
1347                 var now = new Date().getTime() + client_clock_offset_ms;
1348                 remaining_ms = data['position'][color + '_clock_target'] * 1000 - now;
1349                 if (color === "white") {
1350                         white_clock_ms = remaining_ms;
1351                 } else {
1352                         black_clock_ms = remaining_ms;
1353                 }
1354         }
1355
1356         if (white_clock_ms === null || black_clock_ms === null) {
1357                 $("#whiteclock").empty();
1358                 $("#blackclock").empty();
1359                 return;
1360         }
1361
1362         // If either player has ten minutes or less left, add the second counters.
1363         var show_seconds = (white_clock_ms < 60 * 10 * 1000 || black_clock_ms < 60 * 10 * 1000);
1364
1365         if (color) {
1366                 // See when the clock will change next, and update right after that.
1367                 var next_update_ms;
1368                 if (show_seconds) {
1369                         next_update_ms = remaining_ms % 1000 + 100;
1370                 } else {
1371                         next_update_ms = remaining_ms % 60000 + 100;
1372                 }
1373                 clock_timer = setTimeout(update_clock, next_update_ms);
1374         }
1375
1376         $("#whiteclock").text(format_clock(white_clock_ms, show_seconds));
1377         $("#blackclock").text(format_clock(black_clock_ms, show_seconds));
1378 }
1379
1380 /**
1381  * @param {Number} remaining_ms
1382  * @param {boolean} show_seconds
1383  */
1384 var format_clock = function(remaining_ms, show_seconds) {
1385         if (remaining_ms <= 0) {
1386                 if (show_seconds) {
1387                         return "00:00:00";
1388                 } else {
1389                         return "00:00";
1390                 }
1391         }
1392
1393         var remaining = Math.floor(remaining_ms / 1000);
1394         var seconds = remaining % 60;
1395         remaining = (remaining - seconds) / 60;
1396         var minutes = remaining % 60;
1397         remaining = (remaining - minutes) / 60;
1398         var hours = remaining;
1399         if (show_seconds) {
1400                 return format_2d(hours) + ":" + format_2d(minutes) + ":" + format_2d(seconds);
1401         } else {
1402                 return format_2d(hours) + ":" + format_2d(minutes);
1403         }
1404 }
1405
1406 /**
1407  * @param {Number} x
1408  */
1409 var format_2d = function(x) {
1410         if (x >= 10) {
1411                 return x;
1412         } else {
1413                 return "0" + x;
1414         }
1415 }
1416
1417 /**
1418  * @param {string} move
1419  * @param {Number} move_num
1420  * @param {boolean} white_to_play
1421  */
1422 var format_move_with_number = function(move, move_num, white_to_play) {
1423         var ret;
1424         if (white_to_play) {
1425                 ret = (move_num - 1) + '… ';
1426         } else {
1427                 ret = move_num + '. ';
1428         }
1429         ret += move;
1430         return ret;
1431 }
1432
1433 /**
1434  * @param {string} move
1435  * @param {Number} halfmove_num
1436  */
1437 var format_halfmove_with_number = function(move, halfmove_num) {
1438         return format_move_with_number(
1439                 move,
1440                 Math.floor(halfmove_num / 2) + 1,
1441                 halfmove_num % 2 == 0);
1442 }
1443
1444 /**
1445  * @param {Object} data
1446  * @param {Number} halfmove_num
1447  */
1448 var format_tooltip = function(data, halfmove_num) {
1449         if (data['score_history'][halfmove_num] ||
1450             halfmove_num === data['position']['pretty_history'].length) {
1451                 var move;
1452                 var short_score;
1453                 if (halfmove_num === data['position']['pretty_history'].length) {
1454                         move = data['position']['last_move'];
1455                         short_score = format_short_score(data['score']);
1456                 } else {
1457                         move = data['position']['pretty_history'][halfmove_num];
1458                         short_score = format_short_score(data['score_history'][halfmove_num]);
1459                 }
1460                 var move_with_number = format_halfmove_with_number(move, halfmove_num);
1461
1462                 return "After " + move_with_number + ": " + short_score;
1463         } else {
1464                 for (var i = halfmove_num; i --> 0; ) {
1465                         if (data['score_history'][i]) {
1466                                 var move = data['position']['pretty_history'][i];
1467                                 return "[Analysis kept from " + format_halfmove_with_number(move, i) + "]";
1468                         }
1469                 }
1470         }
1471 }
1472
1473 /**
1474  * @param {boolean} sort_by_score
1475  */
1476 var resort_refutation_lines = function(sort_by_score) {
1477         sort_refutation_lines_by_score = sort_by_score;
1478         if (supports_html5_storage()) {
1479                 localStorage['sort_refutation_lines_by_score'] = sort_by_score ? 1 : 0;
1480         }
1481         update_refutation_lines();
1482 }
1483 window['resort_refutation_lines'] = resort_refutation_lines;
1484
1485 /**
1486  * @param {boolean} truncate_history
1487  */
1488 var set_truncate_history = function(truncate_history) {
1489         truncate_display_history = truncate_history;
1490         update_refutation_lines();
1491 }
1492 window['set_truncate_history'] = set_truncate_history;
1493
1494 /**
1495  * @param {number} line_num
1496  * @param {number} move_num
1497  */
1498 var show_line = function(line_num, move_num) {
1499         if (line_num == -1) {
1500                 current_display_line = null;
1501                 current_display_move = null;
1502                 hash_refutation_lines = null;
1503                 if (displayed_analysis_data) {
1504                         // TODO: Support exiting to history position if we are in an
1505                         // analysis line of a history position.
1506                         displayed_analysis_data = null;
1507                 }
1508                 update_board();
1509                 return;
1510         } else {
1511                 current_display_line = jQuery.extend({}, display_lines[line_num]);  // Shallow clone.
1512                 current_display_move = move_num + current_display_line.start_display_move_num;
1513         }
1514         current_display_line_is_history = (line_num == 0);
1515
1516         update_historic_analysis();
1517         update_displayed_line();
1518         update_board_highlight();
1519         update_move_highlight();
1520         redraw_arrows();
1521 }
1522 window['show_line'] = show_line;
1523
1524 var prev_move = function() {
1525         if (current_display_line &&
1526             current_display_move >= current_display_line.start_display_move_num) {
1527                 --current_display_move;
1528         }
1529         update_historic_analysis();
1530         update_displayed_line();
1531         update_move_highlight();
1532 }
1533 window['prev_move'] = prev_move;
1534
1535 var next_move = function() {
1536         if (current_display_line &&
1537             current_display_move < current_display_line.pretty_pv.length - 1) {
1538                 ++current_display_move;
1539         }
1540         update_historic_analysis();
1541         update_displayed_line();
1542         update_move_highlight();
1543 }
1544 window['next_move'] = next_move;
1545
1546 var next_game = function() {
1547         if (current_games === null) {
1548                 return;
1549         }
1550
1551         // Try to find the game we are currently looking at.
1552         for (var game_num = 0; game_num < current_games.length; ++game_num) {
1553                 var game = current_games[game_num];
1554                 if (game['url'] === backend_url) {
1555                         var next_game_num = (game_num + 1) % current_games.length;
1556                         switch_backend(current_games[next_game_num]['url'], current_games[next_game_num]['hashurl']);
1557                         return;
1558                 }
1559         }
1560
1561         // Couldn't find it; give up.
1562 }
1563
1564 var update_historic_analysis = function() {
1565         if (!current_display_line_is_history) {
1566                 return;
1567         }
1568         if (current_display_move == current_display_line.pretty_pv.length - 1) {
1569                 displayed_analysis_data = null;
1570                 update_board();
1571         }
1572
1573         // Fetch old analysis for this line if it exists.
1574         var hiddenboard = chess_from(null, current_display_line.pretty_pv, current_display_move);
1575         var filename = "/history/move" + (current_display_move + 1) + "-" +
1576                 hiddenboard.fen().replace(/ /g, '_').replace(/\//g, '-') + ".json";
1577
1578         current_historic_xhr = $.ajax({
1579                 url: filename
1580         }).done(function(data, textstatus, xhr) {
1581                 displayed_analysis_data = data;
1582                 update_board();
1583         }).fail(function(jqXHR, textStatus, errorThrown) {
1584                 if (textStatus === "abort") {
1585                         // Aborted because we are switching backends. Don't do anything;
1586                         // we will already have been cleared.
1587                 } else {
1588                         displayed_analysis_data = {'failed': true};
1589                         update_board();
1590                 }
1591         });
1592 }
1593
1594 /**
1595  * @param {string} fen
1596  */
1597 var update_imbalance = function(fen) {
1598         var hiddenboard = new Chess(fen);
1599         var imbalance = {'k': 0, 'q': 0, 'r': 0, 'b': 0, 'n': 0, 'p': 0};
1600         for (var row = 0; row < 8; ++row) {
1601                 for (var col = 0; col < 8; ++col) {
1602                         var col_text = String.fromCharCode('a1'.charCodeAt(0) + col);
1603                         var row_text = String.fromCharCode('a1'.charCodeAt(1) + row);
1604                         var square = col_text + row_text;
1605                         var contents = hiddenboard.get(square);
1606                         if (contents !== null) {
1607                                 if (contents.color === 'w') {
1608                                         ++imbalance[contents.type];
1609                                 } else {
1610                                         --imbalance[contents.type];
1611                                 }
1612                         }
1613                 }
1614         }
1615         var white_imbalance = '';
1616         var black_imbalance = '';
1617         for (var piece in imbalance) {
1618                 for (var i = 0; i < imbalance[piece]; ++i) {
1619                         white_imbalance += '<img src="img/chesspieces/wikipedia/w' + piece.toUpperCase() + '.png" alt="" style="width: 15px;height: 15px;">';
1620                 }
1621                 for (var i = 0; i < -imbalance[piece]; ++i) {
1622                         black_imbalance += '<img src="img/chesspieces/wikipedia/b' + piece.toUpperCase() + '.png" alt="" style="width: 15px;height: 15px;">';
1623                 }
1624         }
1625         $('#whiteimbalance').html(white_imbalance);
1626         $('#blackimbalance').html(black_imbalance);
1627 }
1628
1629 /** Mark the currently selected move in red.
1630  * Also replaces the PV with the current displayed line if it's not shown
1631  * anywhere else on the screen.
1632  */
1633 var update_move_highlight = function() {
1634         if (highlighted_move !== null) {
1635                 highlighted_move.removeClass('highlight');
1636         }
1637         if (current_display_line) {
1638                 var display_line_num = find_display_line_matching_num();
1639                 if (display_line_num === null) {
1640                         // Replace the PV with the (complete) line.
1641                         $("#pvtitle").text("Exploring:");
1642                         current_display_line.start_display_move_num = 0;
1643                         display_lines.push(current_display_line);
1644                         $("#pv").html(print_pv(display_lines.length - 1));
1645                         display_line_num = display_lines.length - 1;
1646                 }
1647
1648                 highlighted_move = $("#automove" + display_line_num + "-" + (current_display_move - current_display_line.start_display_move_num));
1649                 highlighted_move.addClass('highlight');
1650         }
1651 }
1652
1653 /**
1654  * See if the current displayed line is identical to any of the ones
1655  * we have on screen. (It might not be if e.g. the analysis reloaded
1656  * since we started looking.)
1657  *
1658  * @return {?number}
1659  */
1660 var find_display_line_matching_num = function() {
1661         for (var i = 0; i < display_lines.length; ++i) {
1662                 var line = display_lines[i];
1663                 if (line.start_display_move_num > 0) continue;
1664                 if (current_display_line.start_fen !== line.start_fen) continue;
1665                 if (current_display_line.pretty_pv.length !== line.pretty_pv.length) continue;
1666                 var ok = true;
1667                 for (var j = 0; j < line.pretty_pv.length; ++j) {
1668                         if (current_display_line.pretty_pv[j] !== line.pretty_pv[j]) {
1669                                 ok = false;
1670                                 break;
1671                         }
1672                 }
1673                 if (ok) {
1674                         return i;
1675                 }
1676         }
1677         return null;
1678 }
1679
1680 var update_displayed_line = function() {
1681         if (current_display_line === null) {
1682                 $("#linenav").hide();
1683                 $("#linemsg").show();
1684                 display_fen = base_fen;
1685                 board.position(base_fen);
1686                 update_imbalance(base_fen);
1687                 return;
1688         }
1689
1690         $("#linenav").show();
1691         $("#linemsg").hide();
1692
1693         if (current_display_move <= 0) {
1694                 $("#prevmove").html("Previous");
1695         } else {
1696                 $("#prevmove").html("<a href=\"javascript:prev_move();\">Previous</a></span>");
1697         }
1698         if (current_display_move == current_display_line.pretty_pv.length - 1) {
1699                 $("#nextmove").html("Next");
1700         } else {
1701                 $("#nextmove").html("<a href=\"javascript:next_move();\">Next</a></span>");
1702         }
1703
1704         var hiddenboard = chess_from(current_display_line.start_fen, current_display_line.pretty_pv, current_display_move);
1705         display_fen = hiddenboard.fen();
1706         board_is_animating = true;
1707         var old_fen = board.fen();
1708         board.position(hiddenboard.fen());
1709         if (board.fen() === old_fen) {
1710                 board_is_animating = false;
1711         } else if (!current_display_line_is_history) {
1712                 // Fire off a hash request, since we're now off the main position
1713                 // and it just changed.
1714                 explore_hash(display_fen);
1715         }
1716         update_imbalance(hiddenboard.fen());
1717 }
1718
1719 /**
1720  * @param {boolean} param_enable_sound
1721  */
1722 var set_sound = function(param_enable_sound) {
1723         enable_sound = param_enable_sound;
1724         if (enable_sound) {
1725                 $("#soundon").html("<strong>On</strong>");
1726                 $("#soundoff").html("<a href=\"javascript:set_sound(false)\">Off</a>");
1727
1728                 // Seemingly at least Firefox prefers MP3 over Opus; tell it otherwise,
1729                 // and also preload the file since the user has selected audio.
1730                 var ding = document.getElementById('ding');
1731                 if (ding && ding.canPlayType && ding.canPlayType('audio/ogg; codecs="opus"') === 'probably') {
1732                         ding.src = 'ding.opus';
1733                         ding.load();
1734                 }
1735         } else {
1736                 $("#soundon").html("<a href=\"javascript:set_sound(true)\">On</a>");
1737                 $("#soundoff").html("<strong>Off</strong>");
1738         }
1739         if (supports_html5_storage()) {
1740                 localStorage['enable_sound'] = enable_sound ? 1 : 0;
1741         }
1742 }
1743 window['set_sound'] = set_sound;
1744
1745 /** Send off a hash probe request to the backend.
1746  * @param {string} fen
1747  */
1748 var explore_hash = function(fen) {
1749         // If we already have a backend response going, abort it.
1750         if (current_hash_xhr) {
1751                 current_hash_xhr.abort();
1752         }
1753         if (current_hash_display_timer) {
1754                 clearTimeout(current_hash_display_timer);
1755                 current_hash_display_timer = null;
1756         }
1757         $("#refutationlines").empty();
1758         current_hash_xhr = $.ajax({
1759                 url: backend_hash_url + "?fen=" + fen
1760         }).done(function(data, textstatus, xhr) {
1761                 show_explore_hash_results(data, fen);
1762         });
1763 }
1764
1765 /** Process the JSON response from a hash probe request.
1766  * @param {!Object} data
1767  * @param {string} fen
1768  */
1769 var show_explore_hash_results = function(data, fen) {
1770         if (board_is_animating) {
1771                 // Updating while the animation is still going causes
1772                 // the animation to jerk. This is pretty crude, but it will do.
1773                 current_hash_display_timer = setTimeout(function() { show_explore_hash_results(data, fen); }, 100);
1774                 return;
1775         }
1776         current_hash_display_timer = null;
1777         hash_refutation_lines = data['lines'];
1778         update_board();
1779 }
1780
1781 // almost all of this stuff comes from the chessboard.js example page
1782 var onDragStart = function(source, piece, position, orientation) {
1783         var pseudogame = new Chess(display_fen);
1784         if (pseudogame.game_over() === true ||
1785             (pseudogame.turn() === 'w' && piece.search(/^b/) !== -1) ||
1786             (pseudogame.turn() === 'b' && piece.search(/^w/) !== -1)) {
1787                 return false;
1788         }
1789
1790         recommended_move = get_best_move(pseudogame, source, null, pseudogame.turn() === 'b');
1791         if (recommended_move) {
1792                 var squareEl = $('#board .square-' + recommended_move.to);
1793                 squareEl.addClass('highlight1-32417');
1794         }
1795         return true;
1796 }
1797
1798 var mousedownSquare = function(e) {
1799         reverse_dragging_from = null;
1800         var square = $(this).attr('data-square');
1801
1802         var pseudogame = new Chess(display_fen);
1803         if (pseudogame.game_over() === true) {
1804                 return;
1805         }
1806
1807         // If the square is empty, or has a piece of the side not to move,
1808         // we handle it. If not, normal piece dragging will take it.
1809         var position = board.position();
1810         if (!position.hasOwnProperty(square) ||
1811             (pseudogame.turn() === 'w' && position[square].search(/^b/) !== -1) ||
1812             (pseudogame.turn() === 'b' && position[square].search(/^w/) !== -1)) {
1813                 reverse_dragging_from = square;
1814                 recommended_move = get_best_move(pseudogame, null, square, pseudogame.turn() === 'b');
1815                 if (recommended_move) {
1816                         var squareEl = $('#board .square-' + recommended_move.from);
1817                         squareEl.addClass('highlight1-32417');
1818                         squareEl = $('#board .square-' + recommended_move.to);
1819                         squareEl.addClass('highlight1-32417');
1820                 }
1821         }
1822 }
1823
1824 var mouseupSquare = function(e) {
1825         if (reverse_dragging_from === null) {
1826                 return;
1827         }
1828         var source = $(this).attr('data-square');
1829         var target = reverse_dragging_from;
1830         reverse_dragging_from = null;
1831         if (onDrop(source, target) !== 'snapback') {
1832                 onSnapEnd(source, target);
1833         }
1834         $("#board").find('.square-55d63').removeClass('highlight1-32417');
1835 }
1836
1837 var get_best_move = function(game, source, target, invert) {
1838         var moves = game.moves({ verbose: true });
1839         if (source !== null) {
1840                 moves = moves.filter(function(move) { return move.from == source; });
1841         }
1842         if (target !== null) {
1843                 moves = moves.filter(function(move) { return move.to == target; });
1844         }
1845         if (moves.length == 0) {
1846                 return null;
1847         }
1848         if (moves.length == 1) {
1849                 return moves[0];
1850         }
1851
1852         // More than one move. Use the display lines (if we have them)
1853         // to disambiguate; otherwise, we have no information.
1854         var move_hash = {};
1855         for (var i = 0; i < moves.length; ++i) {
1856                 move_hash[moves[i].san] = moves[i];
1857         }
1858
1859         // See if we're already exploring some line.
1860         if (current_display_line &&
1861             current_display_move < current_display_line.pretty_pv.length - 1) {
1862                 var first_move = current_display_line.pretty_pv[current_display_move + 1];
1863                 if (move_hash[first_move]) {
1864                         return move_hash[first_move];
1865                 }
1866         }
1867
1868         // History and PV take priority over the display lines.
1869         for (var i = 0; i < 2; ++i) {
1870                 var line = display_lines[i];
1871                 var first_move = line.pretty_pv[line.start_display_move_num];
1872                 if (move_hash[first_move]) {
1873                         return move_hash[first_move];
1874                 }
1875         }
1876
1877         var best_move = null;
1878         var best_move_score = null;
1879
1880         for (var move in refutation_lines) {
1881                 var line = refutation_lines[move];
1882                 if (!line['score']) {
1883                         continue;
1884                 }
1885                 var first_move = line['pv_pretty'][0];
1886                 if (move_hash[first_move]) {
1887                         var score = compute_score_sort_key(line['score'], line['depth'], invert);
1888                         if (best_move_score === null || score > best_move_score) {
1889                                 best_move = move_hash[first_move];
1890                                 best_move_score = score;
1891                         }
1892                 }
1893         }
1894         return best_move;
1895 }
1896
1897 var onDrop = function(source, target) {
1898         if (source === target) {
1899                 if (recommended_move === null) {
1900                         return 'snapback';
1901                 } else {
1902                         // Accept the move. It will be changed in onSnapEnd.
1903                         return;
1904                 }
1905         } else {
1906                 // Suggestion not asked for.
1907                 recommended_move = null;
1908         }
1909
1910         // see if the move is legal
1911         var pseudogame = new Chess(display_fen);
1912         var move = pseudogame.move({
1913                 from: source,
1914                 to: target,
1915                 promotion: 'q' // NOTE: always promote to a queen for example simplicity
1916         });
1917
1918         // illegal move
1919         if (move === null) return 'snapback';
1920 }
1921
1922 var onSnapEnd = function(source, target) {
1923         if (source === target && recommended_move !== null) {
1924                 source = recommended_move.from;
1925                 target = recommended_move.to;
1926         }
1927         recommended_move = null;
1928         var pseudogame = new Chess(display_fen);
1929         var move = pseudogame.move({
1930                 from: source,
1931                 to: target,
1932                 promotion: 'q' // NOTE: always promote to a queen for example simplicity
1933         });
1934
1935         if (current_display_line &&
1936             current_display_move < current_display_line.pretty_pv.length - 1 &&
1937             current_display_line.pretty_pv[current_display_move + 1] === move.san) {
1938                 next_move();
1939                 return;
1940         }
1941
1942         // Walk down the displayed lines until we find one that starts with
1943         // this move, then select that. Note that this gives us a good priority
1944         // order (history first, then PV, then multi-PV lines).
1945         for (var i = 0; i < display_lines.length; ++i) {
1946                 var line = display_lines[i];
1947                 if (line.pretty_pv[line.start_display_move_num] === move.san) {
1948                         show_line(i, 0);
1949                         return;
1950                 }
1951         }
1952
1953         // Shouldn't really be here if we have hash probes, but there's really
1954         // nothing we can do.
1955 }
1956 // End of dragging-related code.
1957
1958 var fmt_cp = function(v) {
1959         if (v === 0) {
1960                 return "0.00";
1961         } else if (v > 0) {
1962                 return "+" + (v / 100).toFixed(2);
1963         } else {
1964                 v = -v;
1965                 return "-" + (v / 100).toFixed(2);
1966         }
1967 }
1968
1969 var format_short_score = function(score) {
1970         if (!score) {
1971                 return "???";
1972         }
1973         if (score[0] === 'm') {
1974                 if (score[2]) {  // Is a bound.
1975                         return score[2] + "\u00a0M " + score[1];
1976                 } else {
1977                         return "M " + score[1];
1978                 }
1979         } else if (score[0] === 'd') {
1980                 return "TB draw";
1981         } else if (score[0] === 'cp') {
1982                 if (score[2]) {  // Is a bound.
1983                         return score[2] + "\u00a0" + fmt_cp(score[1]);
1984                 } else {
1985                         return fmt_cp(score[1]);
1986                 }
1987         }
1988         return null;
1989 }
1990
1991 var format_long_score = function(score) {
1992         if (score[0] === 'm') {
1993                 if (score[1] > 0) {
1994                         return "White mates in " + score[1];
1995                 } else {
1996                         return "Black mates in " + (-score[1]);
1997                 }
1998         } else if (score[0] === 'd') {
1999                 return "Theoretical draw";
2000         } else if (score[0] === 'cp') {
2001                 return "Score: " + format_short_score(score);
2002         }
2003         return null;
2004 }
2005
2006 var compute_plot_score = function(score) {
2007         if (score[0] === 'm') {
2008                 if (score[1] > 0) {
2009                         return 500;
2010                 } else {
2011                         return -500;
2012                 }
2013         } else if (score[0] === 'd') {
2014                 return 0;
2015         } else if (score[0] === 'cp') {
2016                 if (score[1] > 500) {
2017                         return 500;
2018                 } else if (score[1] < -500) {
2019                         return -500;
2020                 } else {
2021                         return score[1];
2022                 }
2023         }
2024         return null;
2025 }
2026
2027 /**
2028  * @param score The score digest tuple.
2029  * @param {?number} depth Depth the move has been computed to, or null.
2030  * @param {boolean} invert Whether black is to play.
2031  * @return {number}
2032  */
2033 var compute_score_sort_key = function(score, depth, invert) {
2034         var s;
2035         if (!score) {
2036                 return -10000000;
2037         }
2038         if (score[0] === 'm') {
2039                 if (score[1] > 0) {
2040                         // White mates.
2041                         s = 99999 - score[1];
2042                 } else {
2043                         // Black mates (note the double negative for score[1]).
2044                         s = -99999 - score[1];
2045                 }
2046         } else if (score[0] === 'd') {
2047                 s = 0;
2048         } else if (score[0] === 'cp') {
2049                 s = score[1];
2050         }
2051         if (s) {
2052                 if (invert) s = -s;
2053                 return s * 200 + (depth || 0);
2054         } else {
2055                 return null;
2056         }
2057 }
2058
2059 /**
2060  * @param {string} new_backend_url
2061  */
2062 var switch_backend = function(new_backend_url, new_backend_hash_url) {
2063         // Stop looking at historic data.
2064         current_display_line = null;
2065         current_display_move = null;
2066         displayed_analysis_data = null;
2067         if (current_historic_xhr) {
2068                 current_historic_xhr.abort();
2069         }
2070
2071         // If we already have a backend response going, abort it.
2072         if (current_analysis_xhr) {
2073                 current_analysis_xhr.abort();
2074         }
2075         if (current_hash_xhr) {
2076                 current_hash_xhr.abort();
2077         }
2078
2079         // Otherwise, we should have a timer going to start a new one.
2080         // Kill that, too.
2081         if (current_analysis_request_timer) {
2082                 clearTimeout(current_analysis_request_timer);
2083                 current_analysis_request_timer = null;
2084         }
2085         if (current_hash_display_timer) {
2086                 clearTimeout(current_hash_display_timer);
2087                 current_hash_display_timer = null;
2088         }
2089
2090         // Request an immediate fetch with the new backend.
2091         backend_url = new_backend_url;
2092         backend_hash_url = new_backend_hash_url;
2093         current_analysis_data = null;
2094         ims = 0;
2095         request_update();
2096 }
2097 window['switch_backend'] = switch_backend;
2098
2099 var init = function() {
2100         unique = get_unique();
2101
2102         // Load settings from HTML5 local storage if available.
2103         if (supports_html5_storage() && localStorage['enable_sound']) {
2104                 set_sound(parseInt(localStorage['enable_sound']));
2105         } else {
2106                 set_sound(false);
2107         }
2108         if (supports_html5_storage() && localStorage['sort_refutation_lines_by_score']) {
2109                 sort_refutation_lines_by_score = parseInt(localStorage['sort_refutation_lines_by_score']);
2110         } else {
2111                 sort_refutation_lines_by_score = true;
2112         }
2113
2114         // Create board.
2115         board = new window.ChessBoard('board', {
2116                 onMoveEnd: function() { board_is_animating = false; },
2117
2118                 draggable: true,
2119                 onDragStart: onDragStart,
2120                 onDrop: onDrop,
2121                 onSnapEnd: onSnapEnd
2122         });
2123         $("#board").on('mousedown', '.square-55d63', mousedownSquare);
2124         $("#board").on('mouseup', '.square-55d63', mouseupSquare);
2125
2126         request_update();
2127         $(window).resize(function() {
2128                 board.resize();
2129                 update_sparkline(displayed_analysis_data || current_analysis_data);
2130                 update_board_highlight();
2131                 redraw_arrows();
2132         });
2133         $(window).keyup(function(event) {
2134                 if (event.which == 39) {  // Left arrow.
2135                         next_move();
2136                 } else if (event.which == 37) {  // Right arrow.
2137                         prev_move();
2138                 } else if (event.which >= 49 && event.which <= 57) {  // 1-9.
2139                         var num = event.which - 49;
2140                         if (current_games && current_games.length >= num) {
2141                                 switch_backend(current_games[num]['url'], current_games[num]['hashurl']);
2142                         }
2143                 } else if (event.which == 78) {  // N.
2144                         next_game();
2145                 }
2146         });
2147         window.addEventListener('hashchange', possibly_switch_game_from_hash, false);
2148 };
2149 $(document).ready(init);
2150
2151 })();