Fix an issue where the URL hash would override the game choice the user just made...
[remoteglot] / 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 = 2016032202;
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  *      hashurl: string,
51  *      id: string,
52  *      score: Object=,
53  *      result: string=,
54  * }>}
55  * @private
56  */
57 var current_games = null;
58
59 /** @type {Array.<{
60  *      from_col: number,
61  *      from_row: number,
62  *      to_col: number,
63  *      to_row: number,
64  *      line_width: number,
65  *      arrow_size: number,
66  *      fg_color: string
67  * }>}
68  * @private
69  */
70 var arrows = [];
71
72 /** @type {Array.<Array.<boolean>>} */
73 var occupied_by_arrows = [];
74
75 /** Currently displayed refutation lines (on-screen).
76  * Can either come from the current_analysis_data, displayed_analysis_data,
77  * or hash_refutation_lines.
78  */
79 var refutation_lines = [];
80
81 /** Refutation lines from current hash probe.
82  *
83  * If non-null, will override refutation lines from the base position.
84  * Note that these are relative to display_fen, not base_fen.
85  */
86 var hash_refutation_lines = null;
87
88 /** @type {!number} @private */
89 var move_num = 1;
90
91 /** @type {!string} @private */
92 var toplay = 'W';
93
94 /** @type {number} @private */
95 var ims = 0;
96
97 /** @type {boolean} @private */
98 var sort_refutation_lines_by_score = true;
99
100 /** @type {boolean} @private */
101 var truncate_display_history = true;
102
103 /** @type {!string|undefined} @private */
104 var highlight_from = undefined;
105
106 /** @type {!string|undefined} @private */
107 var highlight_to = undefined;
108
109 /** The HTML object of the move currently being highlighted (in red).
110  * @type {?jQuery}
111  * @private */
112 var highlighted_move = null;
113
114 /** Currently suggested/recommended move when dragging.
115  * @type {?{from: !string, to: !string}}
116  * @private
117  */
118 var recommended_move = null;
119
120 /** If reverse-dragging (dragging from the destination square to the
121  * source square), the destination square.
122  * @type {?string}
123  * @private
124  */
125 var reverse_dragging_from = null;
126
127 /** @type {?number} @private */
128 var unique = null;
129
130 /** @type {boolean} @private */
131 var enable_sound = false;
132
133 /**
134  * Our best estimate of how many milliseconds we need to add to 
135  * new Date() to get the true UTC time. Calibrated against the
136  * server clock.
137  *
138  * @type {?number}
139  * @private
140  */
141 var client_clock_offset_ms = null;
142
143 var clock_timer = null;
144
145 /** The current position being analyzed, represented as a FEN string.
146  * Note that this is not necessarily the same as display_fen.
147  * @type {?string}
148  * @private
149  */
150 var base_fen = null;
151
152 /** The current position on the board, represented as a FEN string.
153  * Note that board.fen() does not contain e.g. who is to play.
154  * @type {?string}
155  * @private
156  */
157 var display_fen = null;
158
159 /** @typedef {{
160  *    start_fen: string,
161  *    pv: Array.<string>,
162  *    move_num: number,
163  *    toplay: string,
164  *    scores: Array<{first_move: number, score: Object}>,
165  *    start_display_move_num: number
166  * }} DisplayLine
167  *
168  * "start_display_move_num" is the (half-)move number to start displaying the PV at.
169  * "score" is also evaluated at this point.
170  */
171
172 /** All PVs that we currently know of.
173  *
174  * Element 0 is history (or null if no history).
175  * Element 1 is current main PV, or explored line if nowhere else on the screen.
176  * All remaining elements are refutation lines (multi-PV).
177  *
178  * @type {Array.<DisplayLine>}
179  * @private
180  */
181 var display_lines = [];
182
183 /** @type {?DisplayLine} @private */
184 var current_display_line = null;
185
186 /** @type {boolean} @private */
187 var current_display_line_is_history = false;
188
189 /** @type {?number} @private */
190 var current_display_move = null;
191
192 /**
193  * The current backend request to get main analysis (not history), if any,
194  * so that we can abort it.
195  *
196  * @type {?jqXHR}
197  * @private
198  */
199 var current_analysis_xhr = null;
200
201 /**
202  * The current timer to fire off a request to get main analysis (not history),
203  * if any, so that we can abort it.
204  *
205  * @type {?Number}
206  * @private
207  */
208 var current_analysis_request_timer = null;
209
210 /**
211  * The current backend request to get historic data, if any.
212  *
213  * @type {?jqXHR}
214  * @private
215  */
216 var current_historic_xhr = null;
217
218 /**
219  * The current backend request to get hash probes, if any, so that we can abort it.
220  *
221  * @type {?jqXHR}
222  * @private
223  */
224 var current_hash_xhr = null;
225
226 /**
227  * The current timer to display hash probe information (it could be waiting on the
228  * board to stop animating), if any, so that we can abort it.
229  *
230  * @type {?Number}
231  * @private
232  */
233 var current_hash_display_timer = null;
234
235 var supports_html5_storage = function() {
236         try {
237                 return 'localStorage' in window && window['localStorage'] !== null;
238         } catch (e) {
239                 return false;
240         }
241 }
242
243 // Make the unique token persistent so people refreshing the page won't count twice.
244 // Of course, you can never fully protect against people deliberately wanting to spam.
245 var get_unique = function() {
246         var use_local_storage = supports_html5_storage();
247         if (use_local_storage && localStorage['unique']) {
248                 return localStorage['unique'];
249         }
250         var unique = Math.random();
251         if (use_local_storage) {
252                 localStorage['unique'] = unique;
253         }
254         return unique;
255 }
256
257 var request_update = function() {
258         current_analysis_request_timer = null;
259
260         current_analysis_xhr = $.ajax({
261                 url: backend_url + "?ims=" + ims + "&unique=" + unique
262         }).done(function(data, textstatus, xhr) {
263                 sync_server_clock(xhr.getResponseHeader('Date'));
264                 ims = xhr.getResponseHeader('X-RGLM');
265                 var num_viewers = xhr.getResponseHeader('X-RGNV');
266                 var new_data;
267                 if (Array.isArray(data)) {
268                         new_data = JSON.parse(JSON.stringify(current_analysis_data));
269                         JSON_delta.patch(new_data, data);
270                 } else {
271                         new_data = data;
272                 }
273
274                 var minimum_version = xhr.getResponseHeader('X-RGMV');
275                 if (minimum_version && minimum_version > SCRIPT_VERSION) {
276                         // Upgrade to latest version with a force-reload.
277                         location.reload(true);
278                 }
279
280                 possibly_play_sound(current_analysis_data, new_data);
281                 current_analysis_data = new_data;
282                 update_board();
283                 update_num_viewers(num_viewers);
284
285                 // Next update.
286                 current_analysis_request_timer = setTimeout(function() { request_update(); }, 100);
287         }).fail(function(jqXHR, textStatus, errorThrown) {
288                 if (textStatus === "abort") {
289                         // Aborted because we are switching backends. Abandon and don't retry,
290                         // because another one is already started for us.
291                 } else {
292                         // Backend error or similar. Wait ten seconds, then try again.
293                         current_analysis_request_timer = setTimeout(function() { request_update(); }, 10000);
294                 }
295         });
296 }
297
298 var possibly_play_sound = function(old_data, new_data) {
299         if (!enable_sound) {
300                 return;
301         }
302         if (old_data === null) {
303                 return;
304         }
305         var ding = document.getElementById('ding');
306         if (ding && ding.play) {
307                 if (old_data['position'] && old_data['position']['fen'] &&
308                     new_data['position'] && new_data['position']['fen'] &&
309                     (old_data['position']['fen'] !== new_data['position']['fen'] ||
310                      old_data['position']['move_num'] !== new_data['position']['move_num'])) {
311                         ding.play();
312                 }
313         }
314 }
315
316 /**
317  * @type {!string} server_date_string
318  */
319 var sync_server_clock = function(server_date_string) {
320         var server_time_ms = new Date(server_date_string).getTime();
321         var client_time_ms = new Date().getTime();
322         var estimated_offset_ms = server_time_ms - client_time_ms;
323
324         // In order not to let the noise move us too much back and forth
325         // (the server only has one-second resolution anyway), we only
326         // change an existing skew if we are at least five seconds off.
327         if (client_clock_offset_ms === null ||
328             Math.abs(estimated_offset_ms - client_clock_offset_ms) > 5000) {
329                 client_clock_offset_ms = estimated_offset_ms;
330         }
331 }
332
333 var clear_arrows = function() {
334         for (var i = 0; i < arrows.length; ++i) {
335                 if (arrows[i].svg) {
336                         if (arrows[i].svg.parentElement) {
337                                 arrows[i].svg.parentElement.removeChild(arrows[i].svg);
338                         }
339                         delete arrows[i].svg;
340                 }
341         }
342         arrows = [];
343
344         occupied_by_arrows = [];
345         for (var y = 0; y < 8; ++y) {
346                 occupied_by_arrows.push([false, false, false, false, false, false, false, false]);
347         }
348 }
349
350 var redraw_arrows = function() {
351         for (var i = 0; i < arrows.length; ++i) {
352                 position_arrow(arrows[i]);
353         }
354 }
355
356 /** @param {!number} x
357  * @return {!number}
358  */
359 var sign = function(x) {
360         if (x > 0) {
361                 return 1;
362         } else if (x < 0) {
363                 return -1;
364         } else {
365                 return 0;
366         }
367 }
368
369 /** See if drawing this arrow on the board would cause unduly amount of confusion.
370  * @param {!string} from The square the arrow is from (e.g. e4).
371  * @param {!string} to The square the arrow is to (e.g. e4).
372  * @return {boolean}
373  */
374 var interfering_arrow = function(from, to) {
375         var from_col = from.charCodeAt(0) - "a1".charCodeAt(0);
376         var from_row = from.charCodeAt(1) - "a1".charCodeAt(1);
377         var to_col   = to.charCodeAt(0) - "a1".charCodeAt(0);
378         var to_row   = to.charCodeAt(1) - "a1".charCodeAt(1);
379
380         occupied_by_arrows[from_row][from_col] = true;
381
382         // Knight move: Just check that we haven't been at the destination before.
383         if ((Math.abs(to_col - from_col) == 2 && Math.abs(to_row - from_row) == 1) ||
384             (Math.abs(to_col - from_col) == 1 && Math.abs(to_row - from_row) == 2)) {
385                 return occupied_by_arrows[to_row][to_col];
386         }
387
388         // Sliding piece: Check if anything except the from-square is seen before.
389         var dx = sign(to_col - from_col);
390         var dy = sign(to_row - from_row);
391         var x = from_col;
392         var y = from_row;
393         do {
394                 x += dx;
395                 y += dy;
396                 if (occupied_by_arrows[y][x]) {
397                         return true;
398                 }
399                 occupied_by_arrows[y][x] = true;
400         } while (x != to_col || y != to_row);
401
402         return false;
403 }
404
405 /** Find a point along the coordinate system given by the given line,
406  * <t> units forward from the start of the line, <u> units to the right of it.
407  * @param {!number} x1
408  * @param {!number} x2
409  * @param {!number} y1
410  * @param {!number} y2
411  * @param {!number} t
412  * @param {!number} u
413  * @return {!string} The point in "x y" form, suitable for SVG paths.
414  */
415 var point_from_start = function(x1, y1, x2, y2, t, u) {
416         var dx = x2 - x1;
417         var dy = y2 - y1;
418
419         var norm = 1.0 / Math.sqrt(dx * dx + dy * dy);
420         dx *= norm;
421         dy *= norm;
422
423         var x = x1 + dx * t + dy * u;
424         var y = y1 + dy * t - dx * u;
425         return x + " " + y;
426 }
427
428 /** Find a point along the coordinate system given by the given line,
429  * <t> units forward from the end of the line, <u> units to the right of it.
430  * @param {!number} x1
431  * @param {!number} x2
432  * @param {!number} y1
433  * @param {!number} y2
434  * @param {!number} t
435  * @param {!number} u
436  * @return {!string} The point in "x y" form, suitable for SVG paths.
437  */
438 var point_from_end = function(x1, y1, x2, y2, t, u) {
439         var dx = x2 - x1;
440         var dy = y2 - y1;
441
442         var norm = 1.0 / Math.sqrt(dx * dx + dy * dy);
443         dx *= norm;
444         dy *= norm;
445
446         var x = x2 + dx * t + dy * u;
447         var y = y2 + dy * t - dx * u;
448         return x + " " + y;
449 }
450
451 var position_arrow = function(arrow) {
452         if (arrow.svg) {
453                 if (arrow.svg.parentElement) {
454                         arrow.svg.parentElement.removeChild(arrow.svg);
455                 }
456                 delete arrow.svg;
457         }
458         if (current_display_line !== null && !current_display_line_is_history) {
459                 return;
460         }
461
462         var pos = $(".square-a8").position();
463
464         var zoom_factor = $("#board").width() / 400.0;
465         var line_width = arrow.line_width * zoom_factor;
466         var arrow_size = arrow.arrow_size * zoom_factor;
467
468         var square_width = $(".square-a8").width();
469         var from_y = (7 - arrow.from_row + 0.5)*square_width;
470         var to_y = (7 - arrow.to_row + 0.5)*square_width;
471         var from_x = (arrow.from_col + 0.5)*square_width;
472         var to_x = (arrow.to_col + 0.5)*square_width;
473
474         var SVG_NS = "http://www.w3.org/2000/svg";
475         var XHTML_NS = "http://www.w3.org/1999/xhtml";
476         var svg = document.createElementNS(SVG_NS, "svg");
477         svg.setAttribute("width", /** @type{number} */ ($("#board").width()));
478         svg.setAttribute("height", /** @type{number} */ ($("#board").height()));
479         svg.setAttribute("style", "position: absolute");
480         svg.setAttribute("position", "absolute");
481         svg.setAttribute("version", "1.1");
482         svg.setAttribute("class", "c1");
483         svg.setAttribute("xmlns", XHTML_NS);
484
485         var x1 = from_x;
486         var y1 = from_y;
487         var x2 = to_x;
488         var y2 = to_y;
489
490         // Draw the line.
491         var outline = document.createElementNS(SVG_NS, "path");
492         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));
493         outline.setAttribute("xmlns", XHTML_NS);
494         outline.setAttribute("stroke", "#666");
495         outline.setAttribute("stroke-width", line_width + 2);
496         outline.setAttribute("fill", "none");
497         svg.appendChild(outline);
498
499         var path = document.createElementNS(SVG_NS, "path");
500         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));
501         path.setAttribute("xmlns", XHTML_NS);
502         path.setAttribute("stroke", arrow.fg_color);
503         path.setAttribute("stroke-width", line_width);
504         path.setAttribute("fill", "none");
505         svg.appendChild(path);
506
507         // Then the arrow head.
508         var head = document.createElementNS(SVG_NS, "path");
509         head.setAttribute("d",
510                 "M " +  point_from_end(x1, y1, x2, y2, 0, 0) +
511                 " L " + point_from_end(x1, y1, x2, y2, -arrow_size, -arrow_size / 2) +
512                 " L " + point_from_end(x1, y1, x2, y2, -arrow_size * .623, 0.0) +
513                 " L " + point_from_end(x1, y1, x2, y2, -arrow_size, arrow_size / 2) +
514                 " L " + point_from_end(x1, y1, x2, y2, 0, 0));
515         head.setAttribute("xmlns", XHTML_NS);
516         head.setAttribute("stroke", "#000");
517         head.setAttribute("stroke-width", "1");
518         head.setAttribute("fill", arrow.fg_color);
519         svg.appendChild(head);
520
521         $(svg).css({ top: pos.top, left: pos.left, 'pointer-events': 'none' });
522         document.body.appendChild(svg);
523         arrow.svg = svg;
524 }
525
526 /**
527  * @param {!string} from_square
528  * @param {!string} to_square
529  * @param {!string} fg_color
530  * @param {number} line_width
531  * @param {number} arrow_size
532  */
533 var create_arrow = function(from_square, to_square, fg_color, line_width, arrow_size) {
534         var from_col = from_square.charCodeAt(0) - "a1".charCodeAt(0);
535         var from_row = from_square.charCodeAt(1) - "a1".charCodeAt(1);
536         var to_col   = to_square.charCodeAt(0) - "a1".charCodeAt(0);
537         var to_row   = to_square.charCodeAt(1) - "a1".charCodeAt(1);
538
539         // Create arrow.
540         var arrow = {
541                 from_col: from_col,
542                 from_row: from_row,
543                 to_col: to_col,
544                 to_row: to_row,
545                 line_width: line_width,
546                 arrow_size: arrow_size,
547                 fg_color: fg_color
548         };
549
550         position_arrow(arrow);
551         arrows.push(arrow);
552 }
553
554 // Note: invert is ignored.
555 var compare_by_name = function(refutation_lines, invert, a, b) {
556         var ska = refutation_lines[a]['move'];
557         var skb = refutation_lines[b]['move'];
558         if (ska < skb) return -1;
559         if (ska > skb) return 1;
560         return 0;
561 };
562
563 var compare_by_score = function(refutation_lines, invert, a, b) {
564         var sa = compute_score_sort_key(refutation_lines[b]['score'], refutation_lines[b]['depth'], invert);
565         var sb = compute_score_sort_key(refutation_lines[a]['score'], refutation_lines[a]['depth'], invert);
566         return sa - sb;
567 }
568
569 /**
570  * Fake multi-PV using the refutation lines. Find all “relevant” moves,
571  * sorted by quality, descending.
572  *
573  * @param {!Object} data
574  * @param {number} margin The maximum number of centipawns worse than the
575  *     best move can be and still be included.
576  * @param {boolean} invert Whether black is to play.
577  * @return {Array.<string>} The FEN representation (e.g. Ne4) of all
578  *     moves, in score order.
579  */
580 var find_nonstupid_moves = function(data, margin, invert) {
581         // First of all, if there are any moves that are more than 0.5 ahead of
582         // the primary move, the refutation lines are probably bunk, so just
583         // kill them all. 
584         var best_score = undefined;
585         var pv_score = undefined;
586         for (var move in data['refutation_lines']) {
587                 var line = data['refutation_lines'][move];
588                 var score = compute_score_sort_key(line['score'], line['depth'], invert, false);
589                 if (move == data['pv'][0]) {
590                         pv_score = score;
591                 }
592                 if (best_score === undefined || score > best_score) {
593                         best_score = score;
594                 }
595                 if (line['depth'] < 8) {
596                         return [];
597                 }
598         }
599
600         if (best_score - pv_score > 50) {
601                 return [];
602         }
603
604         // Now find all moves that are within “margin” of the best score.
605         // The PV move will always be first.
606         var moves = [];
607         for (var move in data['refutation_lines']) {
608                 var line = data['refutation_lines'][move];
609                 var score = compute_score_sort_key(line['score'], line['depth'], invert);
610                 if (move != data['pv'][0] && best_score - score <= margin) {
611                         moves.push(move);
612                 }
613         }
614         moves = moves.sort(function(a, b) { return compare_by_score(data['refutation_lines'], data['position']['toplay'] === 'B', a, b) });
615         moves.unshift(data['pv'][0]);
616
617         return moves;
618 }
619
620 /**
621  * @param {number} x
622  * @return {!string}
623  */
624 var thousands = function(x) {
625         return String(x).split('').reverse().join('').replace(/(\d{3}\B)/g, '$1,').split('').reverse().join('');
626 }
627
628 /**
629  * @param {!string} start_fen
630  * @param {Array.<string>} pv
631  * @param {number} move_num
632  * @param {!string} toplay
633  * @param {Array<{ first_move: integer, score: Object }>} scores
634  * @param {number} start_display_move_num
635  * @param {number=} opt_limit
636  * @param {boolean=} opt_showlast
637  */
638 var add_pv = function(start_fen, pv, move_num, toplay, scores, start_display_move_num, opt_limit, opt_showlast) {
639         display_lines.push({
640                 start_fen: start_fen,
641                 pv: pv,
642                 move_num: parseInt(move_num),
643                 toplay: toplay,
644                 scores: scores,
645                 start_display_move_num: start_display_move_num
646         });
647         return print_pv(display_lines.length - 1, opt_limit, opt_showlast);
648 }
649
650 /**
651  * @param {number} line_num
652  * @param {number=} opt_limit If set, show at most this number of moves.
653  * @param {boolean=} opt_showlast If limit is set, show the last moves instead of the first ones.
654  */
655 var print_pv = function(line_num, opt_limit, opt_showlast) {
656         var display_line = display_lines[line_num];
657         var pv = display_line.pv;
658         var move_num = display_line.move_num;
659         var toplay = display_line.toplay;
660
661         // Truncate PV at the start if needed.
662         var start_display_move_num = display_line.start_display_move_num;
663         if (start_display_move_num > 0) {
664                 pv = pv.slice(start_display_move_num);
665                 var to_add = start_display_move_num;
666                 if (toplay === 'B') {
667                         ++move_num;
668                         toplay = 'W';
669                         --to_add;
670                 }
671                 if (to_add % 2 == 1) {
672                         toplay = 'B';
673                         --to_add;
674                 }
675                 move_num += to_add / 2;
676         }
677
678         var ret = '';
679         var i = 0;
680         if (opt_limit && opt_showlast && pv.length > opt_limit) {
681                 // Truncate the PV at the beginning (instead of at the end).
682                 // We assume here that toplay is 'W'. We also assume that if
683                 // opt_showlast is set, then it is the history, and thus,
684                 // the UI should be to expand the history.
685                 ret = '(<a class="move" href="javascript:collapse_history(false)">…</a>) ';
686                 i = pv.length - opt_limit;
687                 if (i % 2 == 1) {
688                         ++i;
689                 }
690                 move_num += i / 2;
691         } else if (toplay == 'B' && pv.length > 0) {
692                 var move = "<a class=\"move\" id=\"automove" + line_num + "-0\" href=\"javascript:show_line(" + line_num + ", " + 0 + ");\">" + pv[0] + "</a>";
693                 ret = move_num + '. … ' + move;
694                 toplay = 'W';
695                 ++i;
696                 ++move_num;
697         }
698         for ( ; i < pv.length; ++i) {
699                 var move = "<a class=\"move\" id=\"automove" + line_num + "-" + i + "\" href=\"javascript:show_line(" + line_num + ", " + i + ");\">" + pv[i] + "</a>";
700
701                 if (toplay == 'W') {
702                         if (i > opt_limit && !opt_showlast) {
703                                 return ret + ' (…)';
704                         }
705                         if (ret != '') {
706                                 ret += ' ';
707                         }
708                         ret += move_num + '. ' + move;
709                         ++move_num;
710                         toplay = 'B';
711                 } else {
712                         ret += ' ' + move;
713                         toplay = 'W';
714                 }
715         }
716         return ret;
717 }
718
719 /** Update the highlighted to/from squares on the board.
720  * Based on the global "highlight_from" and "highlight_to" variables.
721  */
722 var update_board_highlight = function() {
723         $("#board").find('.square-55d63').removeClass('nonuglyhighlight');
724         if ((current_display_line === null || current_display_line_is_history) &&
725             highlight_from !== undefined && highlight_to !== undefined) {
726                 $("#board").find('.square-' + highlight_from).addClass('nonuglyhighlight');
727                 $("#board").find('.square-' + highlight_to).addClass('nonuglyhighlight');
728         }
729 }
730
731 var update_history = function() {
732         if (display_lines[0] === null || display_lines[0].pv.length == 0) {
733                 $("#history").html("No history");
734         } else if (truncate_display_history) {
735                 $("#history").html(print_pv(0, 8, true));
736         } else {
737                 $("#history").html(
738                         '(<a class="move" href="javascript:collapse_history(true)">collapse</a>) ' +
739                         print_pv(0));
740         }
741 }
742
743 /**
744  * @param {!boolean} truncate_history
745  */
746 var collapse_history = function(truncate_history) {
747         truncate_display_history = truncate_history;
748         update_history();
749 }
750 window['collapse_history'] = collapse_history;
751
752 /** Update the HTML display of multi-PV from the global "refutation_lines".
753  *
754  * Also recreates the global "display_lines".
755  */
756 var update_refutation_lines = function() {
757         if (base_fen === null) {
758                 return;
759         }
760         if (display_lines.length > 2) {
761                 // Truncate so that only the history and PV is left.
762                 display_lines = [ display_lines[0], display_lines[1] ];
763         }
764         var tbl = $("#refutationlines");
765         tbl.empty();
766
767         // Find out where the lines start from.
768         var base_line = [];
769         var base_scores = display_lines[1].scores;
770         var start_display_move_num = 0;
771         if (hash_refutation_lines) {
772                 base_line = current_display_line.pv.slice(0, current_display_move + 1);
773                 base_scores = current_display_line.scores;
774                 start_display_move_num = base_line.length;
775         }
776
777         var moves = [];
778         for (var move in refutation_lines) {
779                 moves.push(move);
780         }
781
782         var invert = (toplay === 'B');
783         if (current_display_line && current_display_move % 2 == 0) {
784                 invert = !invert;
785         }
786         var compare = sort_refutation_lines_by_score ? compare_by_score : compare_by_name;
787         moves = moves.sort(function(a, b) { return compare(refutation_lines, invert, a, b) });
788         for (var i = 0; i < moves.length; ++i) {
789                 var line = refutation_lines[moves[i]];
790
791                 var tr = document.createElement("tr");
792
793                 var move_td = document.createElement("td");
794                 tr.appendChild(move_td);
795                 $(move_td).addClass("move");
796
797                 var scores = base_scores.concat([{ first_move: start_display_move_num, score: line['score'] }]);
798
799                 if (line['pv'].length == 0) {
800                         // Not found, so just make a one-move PV.
801                         var move = "<a class=\"move\" href=\"javascript:show_line(" + display_lines.length + ", " + 0 + ");\">" + line['move'] + "</a>";
802                         $(move_td).html(move);
803                         var score_td = document.createElement("td");
804
805                         $(score_td).addClass("score");
806                         $(score_td).text("—");
807                         tr.appendChild(score_td);
808
809                         var depth_td = document.createElement("td");
810                         tr.appendChild(depth_td);
811                         $(depth_td).addClass("depth");
812                         $(depth_td).text("—");
813
814                         var pv_td = document.createElement("td");
815                         tr.appendChild(pv_td);
816                         $(pv_td).addClass("pv");
817                         $(pv_td).html(add_pv(base_fen, base_line.concat([ line['move'] ]), move_num, toplay, scores, start_display_move_num));
818
819                         tbl.append(tr);
820                         continue;
821                 }
822
823                 var move = "<a class=\"move\" href=\"javascript:show_line(" + display_lines.length + ", " + 0 + ");\">" + line['move'] + "</a>";
824                 $(move_td).html(move);
825
826                 var score_td = document.createElement("td");
827                 tr.appendChild(score_td);
828                 $(score_td).addClass("score");
829                 $(score_td).text(format_short_score(line['score']));
830
831                 var depth_td = document.createElement("td");
832                 tr.appendChild(depth_td);
833                 $(depth_td).addClass("depth");
834                 if (line['depth'] && line['depth'] >= 0) {
835                         $(depth_td).text("d" + line['depth']);
836                 } else {
837                         $(depth_td).text("—");
838                 }
839
840                 var pv_td = document.createElement("td");
841                 tr.appendChild(pv_td);
842                 $(pv_td).addClass("pv");
843                 $(pv_td).html(add_pv(base_fen, base_line.concat(line['pv']), move_num, toplay, scores, start_display_move_num, 10));
844
845                 tbl.append(tr);
846         }
847
848         // Make one of the links clickable and the other nonclickable.
849         if (sort_refutation_lines_by_score) {
850                 $("#sortbyscore0").html("<a href=\"javascript:resort_refutation_lines(false)\">Move</a>");
851                 $("#sortbyscore1").html("<strong>Score</strong>");
852         } else {
853                 $("#sortbyscore0").html("<strong>Move</strong>");
854                 $("#sortbyscore1").html("<a href=\"javascript:resort_refutation_lines(true)\">Score</a>");
855         }
856
857         // Update the move highlight, as we've rewritten all the HTML.
858         update_move_highlight();
859 }
860
861 /**
862  * Create a Chess.js board object, containing the given position plus the given moves,
863  * up to the given limit.
864  *
865  * @param {?string} fen
866  * @param {Array.<string>} moves
867  * @param {number} last_move
868  */
869 var chess_from = function(fen, moves, last_move) {
870         var hiddenboard = new Chess();
871         if (fen !== null) {
872                 hiddenboard.load(fen);
873         }
874         for (var i = 0; i <= last_move; ++i) {
875                 if (moves[i] === '0-0') {
876                         hiddenboard.move('O-O');
877                 } else if (moves[i] === '0-0-0') {
878                         hiddenboard.move('O-O-O');
879                 } else {
880                         hiddenboard.move(moves[i]);
881                 }
882         }
883         return hiddenboard;
884 }
885
886 var update_game_list = function(games) {
887         $("#games").text("");
888         if (games === null) {
889                 return;
890         }
891
892         var games_div = document.getElementById('games');
893         for (var game_num = 0; game_num < games.length; ++game_num) {
894                 var game = games[game_num];
895                 var game_span = document.createElement("span");
896                 game_span.setAttribute("class", "game");
897
898                 var game_name = document.createTextNode(game['name']);
899                 if (game['url'] === backend_url) {
900                         // This game.
901                         game_span.appendChild(game_name);
902
903                         if (current_analysis_data && current_analysis_data['position']) {
904                                 var score;
905                                 if (current_analysis_data['position']['result']) {
906                                         score = " (" + current_analysis_data['position']['result'] + ")";
907                                 } else {
908                                         score = " (" + format_short_score(current_analysis_data['score']) + ")";
909                                 }
910                                 game_span.appendChild(document.createTextNode(score));
911                         }
912                 } else {
913                         // Some other game.
914                         var game_a = document.createElement("a");
915                         game_a.setAttribute("href", "#" + game['id']);
916                         game_a.appendChild(game_name);
917                         game_span.appendChild(game_a);
918
919                         var score;
920                         if (game['result']) {
921                                 score = " (" + game['result'] + ")";
922                         } else {
923                                 score = " (" + format_short_score(game['score']) + ")";
924                         }
925                         game_span.appendChild(document.createTextNode(score));
926                 }
927
928                 games_div.appendChild(game_span);
929         }
930 }
931
932 /**
933  * Try to find a running game that matches with the current hash,
934  * and switch to it if we're not already displaying it.
935  */
936 var possibly_switch_game_from_hash = function() {
937         if (current_games === null) {
938                 return;
939         }
940
941         var hash = window.location.hash.replace(/^#/,'');
942         for (var i = 0; i < current_games.length; ++i) {
943                 if (current_games[i]['id'] === hash) {
944                         if (backend_url !== current_games[i]['url']) {
945                                 switch_backend(current_games[i]);
946                         }
947                         return;
948                 }
949         }
950 }
951
952 /** Update all the HTML on the page, based on current global state.
953  */
954 var update_board = function() {
955         var data = displayed_analysis_data || current_analysis_data;
956         var current_data = current_analysis_data;  // Convenience alias.
957
958         display_lines = [];
959
960         // Print the history. This is pretty much the only thing that's
961         // unconditionally taken from current_data (we're not interested in
962         // historic history).
963         if (current_data['position']['history']) {
964                 add_pv('start', current_data['position']['history'], 1, 'W', null, 0, 8, true);
965         } else {
966                 display_lines.push(null);
967         }
968         update_history();
969
970         // Games currently in progress, if any.
971         if (current_data['games']) {
972                 current_games = current_data['games'];
973                 possibly_switch_game_from_hash();
974         } else {
975                 current_games = null;
976         }
977         update_game_list(current_games);
978
979         // The headline. Names are always fetched from current_data;
980         // the rest can depend a bit.
981         var headline;
982         if (current_data &&
983             current_data['position']['player_w'] && current_data['position']['player_b']) {
984                 headline = current_data['position']['player_w'] + '–' +
985                         current_data['position']['player_b'] + ', analysis';
986         } else {
987                 headline = 'Analysis';
988         }
989
990         // Credits, where applicable. Note that we don't want the footer to change a lot
991         // when e.g. viewing history, so if any of these changed during the game,
992         // use the current one still.
993         if (current_data['using_lomonosov']) {
994                 $("#lomonosov").show();
995         } else {
996                 $("#lomonosov").hide();
997         }
998
999         // Credits: The engine name/version.
1000         if (current_data['engine'] && current_data['engine']['name'] !== null) {
1001                 $("#engineid").text(current_data['engine']['name']);
1002         }
1003
1004         // Credits: The engine URL.
1005         if (current_data['engine'] && current_data['engine']['url']) {
1006                 $("#engineid").attr("href", current_data['engine']['url']);
1007         } else {
1008                 $("#engineid").removeAttr("href");
1009         }
1010
1011         // Credits: Engine details.
1012         if (current_data['engine'] && current_data['engine']['details']) {
1013                 $("#enginedetails").text(" (" + current_data['engine']['details'] + ")");
1014         } else {
1015                 $("#enginedetails").text("");
1016         }
1017
1018         // Credits: Move source, possibly with URL.
1019         if (current_data['move_source'] && current_data['move_source_url']) {
1020                 $("#movesource").text("Moves provided by ");
1021                 var movesource_a = document.createElement("a");
1022                 movesource_a.setAttribute("href", current_data['move_source_url']);
1023                 var movesource_text = document.createTextNode(current_data['move_source']);
1024                 movesource_a.appendChild(movesource_text);
1025                 var movesource_period = document.createTextNode(".");
1026                 document.getElementById("movesource").appendChild(movesource_a);
1027                 document.getElementById("movesource").appendChild(movesource_period);
1028         } else if (current_data['move_source']) {
1029                 $("#movesource").text("Moves provided by " + current_data['move_source'] + ".");
1030         } else {
1031                 $("#movesource").text("");
1032         }
1033
1034         var last_move;
1035         if (displayed_analysis_data) {
1036                 // Displaying some non-current position, pick out the last move
1037                 // from the history. This will work even if the fetch failed.
1038                 last_move = format_halfmove_with_number(
1039                         current_display_line.pv[current_display_move],
1040                         current_display_move + 1);
1041                 headline += ' after ' + last_move;
1042         } else if (data['position']['last_move'] !== 'none') {
1043                 last_move = format_move_with_number(
1044                         data['position']['last_move'],
1045                         data['position']['move_num'],
1046                         data['position']['toplay'] == 'W');
1047                 headline += ' after ' + last_move;
1048         } else {
1049                 last_move = null;
1050         }
1051         $("#headline").text(headline);
1052
1053         // The <title> contains a very brief headline.
1054         var title_elems = [];
1055         if (data['position'] && data['position']['result']) {
1056                 title_elems.push(data['position']['result']);
1057         } else if (data['score']) {
1058                 title_elems.push(format_short_score(data['score']));
1059         }
1060         if (last_move !== null) {
1061                 title_elems.push(last_move);
1062         }
1063
1064         if (title_elems.length != 0) {
1065                 document.title = '(' + title_elems.join(', ') + ') analysis.sesse.net';
1066         } else {
1067                 document.title = 'analysis.sesse.net';
1068         }
1069
1070         // The last move (shown by highlighting the from and to squares).
1071         if (data['position'] && data['position']['last_move_uci']) {
1072                 highlight_from = data['position']['last_move_uci'].substr(0, 2);
1073                 highlight_to = data['position']['last_move_uci'].substr(2, 2);
1074         } else if (current_display_line_is_history && current_display_move >= 0) {
1075                 // We don't have historic analysis for this position, but we
1076                 // can reconstruct what the last move was by just replaying
1077                 // from the start.
1078                 var hiddenboard = chess_from(null, current_display_line.pv, current_display_move);
1079                 var moves = hiddenboard.history({ verbose: true });
1080                 last_move = moves.pop();
1081                 highlight_from = last_move.from;
1082                 highlight_to = last_move.to;
1083         } else {
1084                 highlight_from = highlight_to = undefined;
1085         }
1086         update_board_highlight();
1087
1088         if (data['failed']) {
1089                 $("#score").text("No analysis for this move");
1090                 $("#pvtitle").text("PV:");
1091                 $("#pv").empty();
1092                 $("#searchstats").html("&nbsp;");
1093                 $("#refutationlines").empty();
1094                 $("#whiteclock").empty();
1095                 $("#blackclock").empty();
1096                 refutation_lines = [];
1097                 update_refutation_lines();
1098                 clear_arrows();
1099                 update_displayed_line();
1100                 update_move_highlight();
1101                 return;
1102         }
1103
1104         update_clock();
1105
1106         // The score.
1107         if (current_display_line && !current_display_line_is_history) {
1108                 var score;
1109                 if (current_display_line.scores && current_display_line.scores.length > 0) {
1110                         for (var i = 0; i < current_display_line.scores.length; ++i) {
1111                                 if (current_display_move < current_display_line.scores[i].first_move) {
1112                                         break;
1113                                 }
1114                                 score = current_display_line.scores[i].score;
1115                         }
1116                 }
1117                 if (score) {
1118                         $("#score").text(format_long_score(score));
1119                 } else {
1120                         $("#score").text("No score for this line");
1121                 }
1122         } else if (data['score']) {
1123                 $("#score").text(format_long_score(data['score']));
1124         }
1125
1126         // The search stats.
1127         if (data['searchstats']) {
1128                 $("#searchstats").html(data['searchstats']);
1129         } else if (data['tablebase'] == 1) {
1130                 $("#searchstats").text("Tablebase result");
1131         } else if (data['nodes'] && data['nps'] && data['depth']) {
1132                 var stats = thousands(data['nodes']) + ' nodes, ' + thousands(data['nps']) + ' nodes/sec, depth ' + data['depth'] + ' ply';
1133                 if (data['seldepth']) {
1134                         stats += ' (' + data['seldepth'] + ' selective)';
1135                 }
1136                 if (data['tbhits'] && data['tbhits'] > 0) {
1137                         if (data['tbhits'] == 1) {
1138                                 stats += ', one Syzygy hit';
1139                         } else {
1140                                 stats += ', ' + thousands(data['tbhits']) + ' Syzygy hits';
1141                         }
1142                 }
1143
1144                 $("#searchstats").text(stats);
1145         } else {
1146                 $("#searchstats").text("");
1147         }
1148
1149         // Update the board itself.
1150         base_fen = data['position']['fen'];
1151         update_displayed_line();
1152
1153         // Print the PV.
1154         $("#pvtitle").text("PV:");
1155
1156         var scores = [{ first_move: -1, score: data['score'] }];
1157         $("#pv").html(add_pv(data['position']['fen'], data['pv'], data['position']['move_num'], data['position']['toplay'], scores, 0));
1158
1159         // Update the PV arrow.
1160         clear_arrows();
1161         if (data['pv'].length >= 1) {
1162                 var hiddenboard = new Chess(base_fen);
1163
1164                 // draw a continuation arrow as long as it's the same piece
1165                 var last_to;
1166                 for (var i = 0; i < data['pv'].length; i += 2) {
1167                         var move = hiddenboard.move(data['pv'][i]);
1168                         if ((i >= 2 && move.from != last_to) ||
1169                              interfering_arrow(move.from, move.to)) {
1170                                 break;
1171                         }
1172                         create_arrow(move.from, move.to, '#f66', 6, 20);
1173                         last_to = move.from;
1174                         hiddenboard.move(data['pv'][i + 1]);  // To keep continuity.
1175                 }
1176
1177                 var alt_moves = find_nonstupid_moves(data, 30, data['position']['toplay'] === 'B');
1178                 for (var i = 1; i < alt_moves.length && i < 3; ++i) {
1179                         hiddenboard = new Chess(base_fen);
1180                         var move = hiddenboard.move(alt_moves[i]);
1181                         create_arrow(move.from, move.to, '#f66', 1, 10);
1182                 }
1183         }
1184
1185         // See if all semi-reasonable moves have only one possible response.
1186         if (data['pv'].length >= 2) {
1187                 var nonstupid_moves = find_nonstupid_moves(data, 300, data['position']['toplay'] === 'B');
1188                 var response;
1189                 {
1190                         var hiddenboard = new Chess(base_fen);
1191                         hiddenboard.move(data['pv'][0]);
1192                         response = hiddenboard.move(data['pv'][1]);
1193                 }
1194                 for (var i = 0; i < nonstupid_moves.length; ++i) {
1195                         if (nonstupid_moves[i] == data['pv'][0]) {
1196                                 // ignore the PV move for refutation lines.
1197                                 continue;
1198                         }
1199                         if (!data['refutation_lines'] ||
1200                             !data['refutation_lines'][nonstupid_moves[i]] ||
1201                             !data['refutation_lines'][nonstupid_moves[i]]['pv'] ||
1202                             data['refutation_lines'][nonstupid_moves[i]]['pv'].length < 1) {
1203                                 // Incomplete PV, abort.
1204                                 response = undefined;
1205                                 break;
1206                         }
1207                         var line = data['refutation_lines'][nonstupid_moves[i]];
1208                         hiddenboard = new Chess(base_fen);
1209                         hiddenboard.move(line['pv'][0]);
1210                         var this_response = hiddenboard.move(line['pv'][1]);
1211                         if (response.from !== this_response.from || response.to !== this_response.to) {
1212                                 // Different response depending on lines, abort.
1213                                 response = undefined;
1214                                 break;
1215                         }
1216                 }
1217
1218                 if (nonstupid_moves.length > 0 && response !== undefined) {
1219                         create_arrow(response.from, response.to, '#66f', 6, 20);
1220                 }
1221         }
1222
1223         // Update the refutation lines.
1224         base_fen = data['position']['fen'];
1225         move_num = parseInt(data['position']['move_num']);
1226         toplay = data['position']['toplay'];
1227         refutation_lines = hash_refutation_lines || data['refutation_lines'];
1228         update_refutation_lines();
1229
1230         // Update the sparkline last, since its size depends on how everything else reflowed.
1231         update_sparkline(data);
1232 }
1233
1234 var update_sparkline = function(data) {
1235         if (data && data['score_history']) {
1236                 var first_move_num = undefined;
1237                 for (var halfmove_num in data['score_history']) {
1238                         halfmove_num = parseInt(halfmove_num);
1239                         if (first_move_num === undefined || halfmove_num < first_move_num) {
1240                                 first_move_num = halfmove_num;
1241                         }
1242                 }
1243                 if (first_move_num !== undefined) {
1244                         var last_move_num = data['position']['move_num'] * 2 - 3;
1245                         if (data['position']['toplay'] === 'B') {
1246                                 ++last_move_num;
1247                         }
1248
1249                         // Possibly truncate some moves if we don't have enough width.
1250                         // FIXME: Sometimes width() for #scorecontainer (and by extent,
1251                         // #scoresparkcontainer) on Chrome for mobile seems to start off
1252                         // at something very small, and then suddenly snap back into place.
1253                         // Figure out why.
1254                         var max_moves = Math.floor($("#scoresparkcontainer").width() / 5) - 5;
1255                         if (last_move_num - first_move_num > max_moves) {
1256                                 first_move_num = last_move_num - max_moves;
1257                         }
1258
1259                         var min_score = -100;
1260                         var max_score = 100;
1261                         var last_score = null;
1262                         var scores = [];
1263                         for (var halfmove_num = first_move_num; halfmove_num <= last_move_num; ++halfmove_num) {
1264                                 if (data['score_history'][halfmove_num]) {
1265                                         var score = compute_plot_score(data['score_history'][halfmove_num]);
1266                                         last_score = score;
1267                                         if (score < min_score) min_score = score;
1268                                         if (score > max_score) max_score = score;
1269                                 }
1270                                 scores.push(last_score);
1271                         }
1272                         if (data['score']) {
1273                                 scores.push(compute_plot_score(data['score']));
1274                         }
1275                         // FIXME: at some widths, calling sparkline() seems to push
1276                         // #scorecontainer under the board.
1277                         $("#scorespark").sparkline(scores, {
1278                                 type: 'bar',
1279                                 zeroColor: 'gray',
1280                                 chartRangeMin: min_score,
1281                                 chartRangeMax: max_score,
1282                                 tooltipFormatter: function(sparkline, options, fields) {
1283                                         return format_tooltip(data, fields[0].offset + first_move_num);
1284                                 }
1285                         });
1286                 } else {
1287                         $("#scorespark").text("");
1288                 }
1289         } else {
1290                 $("#scorespark").text("");
1291         }
1292 }
1293
1294 /**
1295  * @param {number} num_viewers
1296  */
1297 var update_num_viewers = function(num_viewers) {
1298         if (num_viewers === null) {
1299                 $("#numviewers").text("");
1300         } else if (num_viewers == 1) {
1301                 $("#numviewers").text("You are the only current viewer");
1302         } else {
1303                 $("#numviewers").text(num_viewers + " current viewers");
1304         }
1305 }
1306
1307 var update_clock = function() {
1308         clearTimeout(clock_timer);
1309
1310         var data = displayed_analysis_data || current_analysis_data;
1311         if (!data) return;
1312
1313         if (data['position']) {
1314                 var result = data['position']['result'];
1315                 if (result === '1-0') {
1316                         $("#whiteclock").text("1");
1317                         $("#blackclock").text("0");
1318                         $("#whiteclock").removeClass("running-clock");
1319                         $("#blackclock").removeClass("running-clock");
1320                         return;
1321                 }
1322                 if (result === '1/2-1/2') {
1323                         $("#whiteclock").text("1/2");
1324                         $("#blackclock").text("1/2");
1325                         $("#whiteclock").removeClass("running-clock");
1326                         $("#blackclock").removeClass("running-clock");
1327                         return;
1328                 }       
1329                 if (result === '0-1') {
1330                         $("#whiteclock").text("0");
1331                         $("#blackclock").text("1");
1332                         $("#whiteclock").removeClass("running-clock");
1333                         $("#blackclock").removeClass("running-clock");
1334                         return;
1335                 }
1336         }
1337
1338         var white_clock_ms = null;
1339         var black_clock_ms = null;
1340
1341         // Static clocks.
1342         if (data['position'] &&
1343             data['position']['white_clock'] &&
1344             data['position']['black_clock']) {
1345                 white_clock_ms = data['position']['white_clock'] * 1000;
1346                 black_clock_ms = data['position']['black_clock'] * 1000;
1347         }
1348
1349         // Dynamic clock (only one, obviously).
1350         var color;
1351         if (data['position']['white_clock_target']) {
1352                 color = "white";
1353                 $("#whiteclock").addClass("running-clock");
1354                 $("#blackclock").removeClass("running-clock");
1355         } else if (data['position']['black_clock_target']) {
1356                 color = "black";
1357                 $("#whiteclock").removeClass("running-clock");
1358                 $("#blackclock").addClass("running-clock");
1359         } else {
1360                 $("#whiteclock").removeClass("running-clock");
1361                 $("#blackclock").removeClass("running-clock");
1362         }
1363         var remaining_ms;
1364         if (color) {
1365                 var now = new Date().getTime() + client_clock_offset_ms;
1366                 remaining_ms = data['position'][color + '_clock_target'] * 1000 - now;
1367                 if (color === "white") {
1368                         white_clock_ms = remaining_ms;
1369                 } else {
1370                         black_clock_ms = remaining_ms;
1371                 }
1372         }
1373
1374         if (white_clock_ms === null || black_clock_ms === null) {
1375                 $("#whiteclock").empty();
1376                 $("#blackclock").empty();
1377                 return;
1378         }
1379
1380         // If either player has ten minutes or less left, add the second counters.
1381         var show_seconds = (white_clock_ms < 60 * 10 * 1000 || black_clock_ms < 60 * 10 * 1000);
1382
1383         if (color) {
1384                 // See when the clock will change next, and update right after that.
1385                 var next_update_ms;
1386                 if (show_seconds) {
1387                         next_update_ms = remaining_ms % 1000 + 100;
1388                 } else {
1389                         next_update_ms = remaining_ms % 60000 + 100;
1390                 }
1391                 clock_timer = setTimeout(update_clock, next_update_ms);
1392         }
1393
1394         $("#whiteclock").text(format_clock(white_clock_ms, show_seconds));
1395         $("#blackclock").text(format_clock(black_clock_ms, show_seconds));
1396 }
1397
1398 /**
1399  * @param {Number} remaining_ms
1400  * @param {boolean} show_seconds
1401  */
1402 var format_clock = function(remaining_ms, show_seconds) {
1403         if (remaining_ms <= 0) {
1404                 if (show_seconds) {
1405                         return "00:00:00";
1406                 } else {
1407                         return "00:00";
1408                 }
1409         }
1410
1411         var remaining = Math.floor(remaining_ms / 1000);
1412         var seconds = remaining % 60;
1413         remaining = (remaining - seconds) / 60;
1414         var minutes = remaining % 60;
1415         remaining = (remaining - minutes) / 60;
1416         var hours = remaining;
1417         if (show_seconds) {
1418                 return format_2d(hours) + ":" + format_2d(minutes) + ":" + format_2d(seconds);
1419         } else {
1420                 return format_2d(hours) + ":" + format_2d(minutes);
1421         }
1422 }
1423
1424 /**
1425  * @param {Number} x
1426  */
1427 var format_2d = function(x) {
1428         if (x >= 10) {
1429                 return x;
1430         } else {
1431                 return "0" + x;
1432         }
1433 }
1434
1435 /**
1436  * @param {string} move
1437  * @param {Number} move_num
1438  * @param {boolean} white_to_play
1439  */
1440 var format_move_with_number = function(move, move_num, white_to_play) {
1441         var ret;
1442         if (white_to_play) {
1443                 ret = (move_num - 1) + '… ';
1444         } else {
1445                 ret = move_num + '. ';
1446         }
1447         ret += move;
1448         return ret;
1449 }
1450
1451 /**
1452  * @param {string} move
1453  * @param {Number} halfmove_num
1454  */
1455 var format_halfmove_with_number = function(move, halfmove_num) {
1456         return format_move_with_number(
1457                 move,
1458                 Math.floor(halfmove_num / 2) + 1,
1459                 halfmove_num % 2 == 0);
1460 }
1461
1462 /**
1463  * @param {Object} data
1464  * @param {Number} halfmove_num
1465  */
1466 var format_tooltip = function(data, halfmove_num) {
1467         if (data['score_history'][halfmove_num] ||
1468             halfmove_num === data['position']['history'].length) {
1469                 var move;
1470                 var short_score;
1471                 if (halfmove_num === data['position']['history'].length) {
1472                         move = data['position']['last_move'];
1473                         short_score = format_short_score(data['score']);
1474                 } else {
1475                         move = data['position']['history'][halfmove_num];
1476                         short_score = format_short_score(data['score_history'][halfmove_num]);
1477                 }
1478                 var move_with_number = format_halfmove_with_number(move, halfmove_num);
1479
1480                 return "After " + move_with_number + ": " + short_score;
1481         } else {
1482                 for (var i = halfmove_num; i --> 0; ) {
1483                         if (data['score_history'][i]) {
1484                                 var move = data['position']['history'][i];
1485                                 return "[Analysis kept from " + format_halfmove_with_number(move, i) + "]";
1486                         }
1487                 }
1488         }
1489 }
1490
1491 /**
1492  * @param {boolean} sort_by_score
1493  */
1494 var resort_refutation_lines = function(sort_by_score) {
1495         sort_refutation_lines_by_score = sort_by_score;
1496         if (supports_html5_storage()) {
1497                 localStorage['sort_refutation_lines_by_score'] = sort_by_score ? 1 : 0;
1498         }
1499         update_refutation_lines();
1500 }
1501 window['resort_refutation_lines'] = resort_refutation_lines;
1502
1503 /**
1504  * @param {boolean} truncate_history
1505  */
1506 var set_truncate_history = function(truncate_history) {
1507         truncate_display_history = truncate_history;
1508         update_refutation_lines();
1509 }
1510 window['set_truncate_history'] = set_truncate_history;
1511
1512 /**
1513  * @param {number} line_num
1514  * @param {number} move_num
1515  */
1516 var show_line = function(line_num, move_num) {
1517         if (line_num == -1) {
1518                 current_display_line = null;
1519                 current_display_move = null;
1520                 hash_refutation_lines = null;
1521                 if (displayed_analysis_data) {
1522                         // TODO: Support exiting to history position if we are in an
1523                         // analysis line of a history position.
1524                         displayed_analysis_data = null;
1525                 }
1526                 update_board();
1527                 return;
1528         } else {
1529                 current_display_line = jQuery.extend({}, display_lines[line_num]);  // Shallow clone.
1530                 current_display_move = move_num + current_display_line.start_display_move_num;
1531         }
1532         current_display_line_is_history = (line_num == 0);
1533
1534         update_historic_analysis();
1535         update_displayed_line();
1536         update_board_highlight();
1537         update_move_highlight();
1538         redraw_arrows();
1539 }
1540 window['show_line'] = show_line;
1541
1542 var prev_move = function() {
1543         if (current_display_line &&
1544             current_display_move >= current_display_line.start_display_move_num) {
1545                 --current_display_move;
1546         }
1547         update_historic_analysis();
1548         update_displayed_line();
1549         update_move_highlight();
1550 }
1551 window['prev_move'] = prev_move;
1552
1553 var next_move = function() {
1554         if (current_display_line &&
1555             current_display_move < current_display_line.pv.length - 1) {
1556                 ++current_display_move;
1557         }
1558         update_historic_analysis();
1559         update_displayed_line();
1560         update_move_highlight();
1561 }
1562 window['next_move'] = next_move;
1563
1564 var next_game = function() {
1565         if (current_games === null) {
1566                 return;
1567         }
1568
1569         // Try to find the game we are currently looking at.
1570         for (var game_num = 0; game_num < current_games.length; ++game_num) {
1571                 var game = current_games[game_num];
1572                 if (game['url'] === backend_url) {
1573                         var next_game_num = (game_num + 1) % current_games.length;
1574                         switch_backend(current_games[next_game_num]);
1575                         return;
1576                 }
1577         }
1578
1579         // Couldn't find it; give up.
1580 }
1581
1582 var update_historic_analysis = function() {
1583         if (!current_display_line_is_history) {
1584                 return;
1585         }
1586         if (current_display_move == current_display_line.pv.length - 1) {
1587                 displayed_analysis_data = null;
1588                 update_board();
1589         }
1590
1591         // Fetch old analysis for this line if it exists.
1592         var hiddenboard = chess_from(null, current_display_line.pv, current_display_move);
1593         var filename = "/history/move" + (current_display_move + 1) + "-" +
1594                 hiddenboard.fen().replace(/ /g, '_').replace(/\//g, '-') + ".json";
1595
1596         current_historic_xhr = $.ajax({
1597                 url: filename
1598         }).done(function(data, textstatus, xhr) {
1599                 displayed_analysis_data = data;
1600                 update_board();
1601         }).fail(function(jqXHR, textStatus, errorThrown) {
1602                 if (textStatus === "abort") {
1603                         // Aborted because we are switching backends. Don't do anything;
1604                         // we will already have been cleared.
1605                 } else {
1606                         displayed_analysis_data = {'failed': true};
1607                         update_board();
1608                 }
1609         });
1610 }
1611
1612 /**
1613  * @param {string} fen
1614  */
1615 var update_imbalance = function(fen) {
1616         var hiddenboard = new Chess(fen);
1617         var imbalance = {'k': 0, 'q': 0, 'r': 0, 'b': 0, 'n': 0, 'p': 0};
1618         for (var row = 0; row < 8; ++row) {
1619                 for (var col = 0; col < 8; ++col) {
1620                         var col_text = String.fromCharCode('a1'.charCodeAt(0) + col);
1621                         var row_text = String.fromCharCode('a1'.charCodeAt(1) + row);
1622                         var square = col_text + row_text;
1623                         var contents = hiddenboard.get(square);
1624                         if (contents !== null) {
1625                                 if (contents.color === 'w') {
1626                                         ++imbalance[contents.type];
1627                                 } else {
1628                                         --imbalance[contents.type];
1629                                 }
1630                         }
1631                 }
1632         }
1633         var white_imbalance = '';
1634         var black_imbalance = '';
1635         for (var piece in imbalance) {
1636                 for (var i = 0; i < imbalance[piece]; ++i) {
1637                         white_imbalance += '<img src="img/chesspieces/wikipedia/w' + piece.toUpperCase() + '.png" alt="" style="width: 15px;height: 15px;">';
1638                 }
1639                 for (var i = 0; i < -imbalance[piece]; ++i) {
1640                         black_imbalance += '<img src="img/chesspieces/wikipedia/b' + piece.toUpperCase() + '.png" alt="" style="width: 15px;height: 15px;">';
1641                 }
1642         }
1643         $('#whiteimbalance').html(white_imbalance);
1644         $('#blackimbalance').html(black_imbalance);
1645 }
1646
1647 /** Mark the currently selected move in red.
1648  * Also replaces the PV with the current displayed line if it's not shown
1649  * anywhere else on the screen.
1650  */
1651 var update_move_highlight = function() {
1652         if (highlighted_move !== null) {
1653                 highlighted_move.removeClass('highlight'); 
1654         }
1655         if (current_display_line) {
1656                 var display_line_num = find_display_line_matching_num();
1657                 if (display_line_num === null) {
1658                         // Replace the PV with the (complete) line.
1659                         $("#pvtitle").text("Exploring:");
1660                         current_display_line.start_display_move_num = 0;
1661                         display_lines.push(current_display_line);
1662                         $("#pv").html(print_pv(display_lines.length - 1));
1663                         display_line_num = display_lines.length - 1;
1664
1665                         // Clear out the PV, so it's not selected by anything later.
1666                         display_lines[1].pv = [];
1667                 }
1668
1669                 highlighted_move = $("#automove" + display_line_num + "-" + (current_display_move - current_display_line.start_display_move_num));
1670                 highlighted_move.addClass('highlight');
1671         }
1672 }
1673
1674 /**
1675  * See if the current displayed line is identical to any of the ones
1676  * we have on screen. (It might not be if e.g. the analysis reloaded
1677  * since we started looking.)
1678  *
1679  * @return {?number}
1680  */
1681 var find_display_line_matching_num = function() {
1682         for (var i = 0; i < display_lines.length; ++i) {
1683                 var line = display_lines[i];
1684                 if (line.start_display_move_num > 0) continue;
1685                 if (current_display_line.start_fen !== line.start_fen) continue;
1686                 if (current_display_line.pv.length !== line.pv.length) continue;
1687                 var ok = true;
1688                 for (var j = 0; j < line.pv.length; ++j) {
1689                         if (current_display_line.pv[j] !== line.pv[j]) {
1690                                 ok = false;
1691                                 break;
1692                         }
1693                 }
1694                 if (ok) {
1695                         return i;
1696                 }
1697         }
1698         return null;
1699 }
1700
1701 /** Update the board based on the currently displayed line.
1702  * 
1703  * TODO: This should really be called only whenever something changes,
1704  * instead of all the time.
1705  */
1706 var update_displayed_line = function() {
1707         if (current_display_line === null) {
1708                 $("#linenav").hide();
1709                 $("#linemsg").show();
1710                 display_fen = base_fen;
1711                 set_board_position(base_fen);
1712                 update_imbalance(base_fen);
1713                 return;
1714         }
1715
1716         $("#linenav").show();
1717         $("#linemsg").hide();
1718
1719         if (current_display_move <= 0) {
1720                 $("#prevmove").html("Previous");
1721         } else {
1722                 $("#prevmove").html("<a href=\"javascript:prev_move();\">Previous</a></span>");
1723         }
1724         if (current_display_move == current_display_line.pv.length - 1) {
1725                 $("#nextmove").html("Next");
1726         } else {
1727                 $("#nextmove").html("<a href=\"javascript:next_move();\">Next</a></span>");
1728         }
1729
1730         var hiddenboard = chess_from(current_display_line.start_fen, current_display_line.pv, current_display_move);
1731         set_board_position(hiddenboard.fen());
1732         if (display_fen !== hiddenboard.fen() && !current_display_line_is_history) {
1733                 // Fire off a hash request, since we're now off the main position
1734                 // and it just changed.
1735                 explore_hash(hiddenboard.fen());
1736         }
1737         display_fen = hiddenboard.fen();
1738         update_imbalance(hiddenboard.fen());
1739 }
1740
1741 var set_board_position = function(new_fen) {
1742         board_is_animating = true;
1743         var old_fen = board.fen();
1744         board.position(new_fen);
1745         if (board.fen() === old_fen) {
1746                 board_is_animating = false;
1747         }
1748 }
1749
1750 /**
1751  * @param {boolean} param_enable_sound
1752  */
1753 var set_sound = function(param_enable_sound) {
1754         enable_sound = param_enable_sound;
1755         if (enable_sound) {
1756                 $("#soundon").html("<strong>On</strong>");
1757                 $("#soundoff").html("<a href=\"javascript:set_sound(false)\">Off</a>");
1758
1759                 // Seemingly at least Firefox prefers MP3 over Opus; tell it otherwise,
1760                 // and also preload the file since the user has selected audio.
1761                 var ding = document.getElementById('ding');
1762                 if (ding && ding.canPlayType && ding.canPlayType('audio/ogg; codecs="opus"') === 'probably') {
1763                         ding.src = 'ding.opus';
1764                         ding.load();
1765                 }
1766         } else {
1767                 $("#soundon").html("<a href=\"javascript:set_sound(true)\">On</a>");
1768                 $("#soundoff").html("<strong>Off</strong>");
1769         }
1770         if (supports_html5_storage()) {
1771                 localStorage['enable_sound'] = enable_sound ? 1 : 0;
1772         }
1773 }
1774 window['set_sound'] = set_sound;
1775
1776 /** Send off a hash probe request to the backend.
1777  * @param {string} fen
1778  */
1779 var explore_hash = function(fen) {
1780         // If we already have a backend response going, abort it.
1781         if (current_hash_xhr) {
1782                 current_hash_xhr.abort();
1783         }
1784         if (current_hash_display_timer) {
1785                 clearTimeout(current_hash_display_timer);
1786                 current_hash_display_timer = null;
1787         }
1788         $("#refutationlines").empty();
1789         current_hash_xhr = $.ajax({
1790                 url: backend_hash_url + "?fen=" + fen
1791         }).done(function(data, textstatus, xhr) {
1792                 show_explore_hash_results(data, fen);
1793         });
1794 }
1795
1796 /** Process the JSON response from a hash probe request.
1797  * @param {!Object} data
1798  * @param {string} fen
1799  */
1800 var show_explore_hash_results = function(data, fen) {
1801         if (board_is_animating) {
1802                 // Updating while the animation is still going causes
1803                 // the animation to jerk. This is pretty crude, but it will do.
1804                 current_hash_display_timer = setTimeout(function() { show_explore_hash_results(data, fen); }, 100);
1805                 return;
1806         }
1807         current_hash_display_timer = null;
1808         hash_refutation_lines = data['lines'];
1809         update_board();
1810 }
1811
1812 // almost all of this stuff comes from the chessboard.js example page
1813 var onDragStart = function(source, piece, position, orientation) {
1814         var pseudogame = new Chess(display_fen);
1815         if (pseudogame.game_over() === true ||
1816             (pseudogame.turn() === 'w' && piece.search(/^b/) !== -1) ||
1817             (pseudogame.turn() === 'b' && piece.search(/^w/) !== -1)) {
1818                 return false;
1819         }
1820
1821         recommended_move = get_best_move(pseudogame, source, null, pseudogame.turn() === 'b');
1822         if (recommended_move) {
1823                 var squareEl = $('#board .square-' + recommended_move.to);
1824                 squareEl.addClass('highlight1-32417');
1825         }
1826         return true;
1827 }
1828
1829 var mousedownSquare = function(e) {
1830         reverse_dragging_from = null;
1831         var square = $(this).attr('data-square');
1832
1833         var pseudogame = new Chess(display_fen);
1834         if (pseudogame.game_over() === true) {
1835                 return;
1836         }
1837
1838         // If the square is empty, or has a piece of the side not to move,
1839         // we handle it. If not, normal piece dragging will take it.
1840         var position = board.position();
1841         if (!position.hasOwnProperty(square) ||
1842             (pseudogame.turn() === 'w' && position[square].search(/^b/) !== -1) ||
1843             (pseudogame.turn() === 'b' && position[square].search(/^w/) !== -1)) {
1844                 reverse_dragging_from = square;
1845                 recommended_move = get_best_move(pseudogame, null, square, pseudogame.turn() === 'b');
1846                 if (recommended_move) {
1847                         var squareEl = $('#board .square-' + recommended_move.from);
1848                         squareEl.addClass('highlight1-32417');
1849                         squareEl = $('#board .square-' + recommended_move.to);
1850                         squareEl.addClass('highlight1-32417');
1851                 }
1852         }
1853 }
1854
1855 var mouseupSquare = function(e) {
1856         if (reverse_dragging_from === null) {
1857                 return;
1858         }
1859         var source = $(this).attr('data-square');
1860         var target = reverse_dragging_from;
1861         reverse_dragging_from = null;
1862         if (onDrop(source, target) !== 'snapback') {
1863                 onSnapEnd(source, target);
1864         }
1865         $("#board").find('.square-55d63').removeClass('highlight1-32417');
1866 }
1867
1868 var get_best_move = function(game, source, target, invert) {
1869         var moves = game.moves({ verbose: true });
1870         if (source !== null) {
1871                 moves = moves.filter(function(move) { return move.from == source; });
1872         }
1873         if (target !== null) {
1874                 moves = moves.filter(function(move) { return move.to == target; });
1875         }
1876         if (moves.length == 0) {
1877                 return null;
1878         }
1879         if (moves.length == 1) {
1880                 return moves[0];
1881         }
1882
1883         // More than one move. Use the display lines (if we have them)
1884         // to disambiguate; otherwise, we have no information.
1885         var move_hash = {};
1886         for (var i = 0; i < moves.length; ++i) {
1887                 move_hash[moves[i].san] = moves[i];
1888         }
1889
1890         // See if we're already exploring some line.
1891         if (current_display_line &&
1892             current_display_move < current_display_line.pv.length - 1) {
1893                 var first_move = current_display_line.pv[current_display_move + 1];
1894                 if (move_hash[first_move]) {
1895                         return move_hash[first_move];
1896                 }
1897         }
1898
1899         // History and PV take priority over the display lines.
1900         for (var i = 0; i < 2; ++i) {
1901                 var line = display_lines[i];
1902                 var first_move = line.pv[line.start_display_move_num];
1903                 if (move_hash[first_move]) {
1904                         return move_hash[first_move];
1905                 }
1906         }
1907
1908         var best_move = null;
1909         var best_move_score = null;
1910
1911         for (var move in refutation_lines) {
1912                 var line = refutation_lines[move];
1913                 if (!line['score']) {
1914                         continue;
1915                 }
1916                 var first_move = line['pv'][0];
1917                 if (move_hash[first_move]) {
1918                         var score = compute_score_sort_key(line['score'], line['depth'], invert);
1919                         if (best_move_score === null || score > best_move_score) {
1920                                 best_move = move_hash[first_move];
1921                                 best_move_score = score;
1922                         }
1923                 }
1924         }
1925         return best_move;
1926 }
1927
1928 var onDrop = function(source, target) {
1929         if (source === target) {
1930                 if (recommended_move === null) {
1931                         return 'snapback';
1932                 } else {
1933                         // Accept the move. It will be changed in onSnapEnd.
1934                         return;
1935                 }
1936         } else {
1937                 // Suggestion not asked for.
1938                 recommended_move = null;
1939         }
1940
1941         // see if the move is legal
1942         var pseudogame = new Chess(display_fen);
1943         var move = pseudogame.move({
1944                 from: source,
1945                 to: target,
1946                 promotion: 'q' // NOTE: always promote to a queen for example simplicity
1947         });
1948
1949         // illegal move
1950         if (move === null) return 'snapback';
1951 }
1952
1953 var onSnapEnd = function(source, target) {
1954         if (source === target && recommended_move !== null) {
1955                 source = recommended_move.from;
1956                 target = recommended_move.to;
1957         }
1958         recommended_move = null;
1959         var pseudogame = new Chess(display_fen);
1960         var move = pseudogame.move({
1961                 from: source,
1962                 to: target,
1963                 promotion: 'q' // NOTE: always promote to a queen for example simplicity
1964         });
1965
1966         if (current_display_line &&
1967             current_display_move < current_display_line.pv.length - 1 &&
1968             current_display_line.pv[current_display_move + 1] === move.san) {
1969                 next_move();
1970                 return;
1971         }
1972
1973         // Walk down the displayed lines until we find one that starts with
1974         // this move, then select that. Note that this gives us a good priority
1975         // order (history first, then PV, then multi-PV lines).
1976         for (var i = 0; i < display_lines.length; ++i) {
1977                 if (i == 1 && current_display_line) {
1978                         // Do not choose PV if not on it.
1979                         continue;
1980                 }
1981                 var line = display_lines[i];
1982                 if (line.pv[line.start_display_move_num] === move.san) {
1983                         show_line(i, 0);
1984                         return;
1985                 }
1986         }
1987
1988         // Shouldn't really be here if we have hash probes, but there's really
1989         // nothing we can do.
1990 }
1991 // End of dragging-related code.
1992
1993 var fmt_cp = function(v) {
1994         if (v === 0) {
1995                 return "0.00";
1996         } else if (v > 0) {
1997                 return "+" + (v / 100).toFixed(2);
1998         } else {
1999                 v = -v;
2000                 return "-" + (v / 100).toFixed(2);
2001         }
2002 }
2003
2004 var format_short_score = function(score) {
2005         if (!score) {
2006                 return "???";
2007         }
2008         if (score[0] === 'm') {
2009                 if (score[2]) {  // Is a bound.
2010                         return score[2] + "\u00a0M " + score[1];
2011                 } else {
2012                         return "M " + score[1];
2013                 }
2014         } else if (score[0] === 'd') {
2015                 return "TB draw";
2016         } else if (score[0] === 'cp') {
2017                 if (score[2]) {  // Is a bound.
2018                         return score[2] + "\u00a0" + fmt_cp(score[1]);
2019                 } else {
2020                         return fmt_cp(score[1]);
2021                 }
2022         }
2023         return null;
2024 }
2025
2026 var format_long_score = function(score) {
2027         if (!score) {
2028                 return "???";
2029         }
2030         if (score[0] === 'm') {
2031                 if (score[1] > 0) {
2032                         return "White mates in " + score[1];
2033                 } else {
2034                         return "Black mates in " + (-score[1]);
2035                 }
2036         } else if (score[0] === 'd') {
2037                 return "Theoretical draw";
2038         } else if (score[0] === 'cp') {
2039                 return "Score: " + format_short_score(score);
2040         }
2041         return null;
2042 }
2043
2044 var compute_plot_score = function(score) {
2045         if (score[0] === 'm') {
2046                 if (score[1] > 0) {
2047                         return 500;
2048                 } else {
2049                         return -500;
2050                 }
2051         } else if (score[0] === 'd') {
2052                 return 0;
2053         } else if (score[0] === 'cp') {
2054                 if (score[1] > 500) {
2055                         return 500;
2056                 } else if (score[1] < -500) {
2057                         return -500;
2058                 } else {
2059                         return score[1];
2060                 }
2061         }
2062         return null;
2063 }
2064
2065 /**
2066  * @param score The score digest tuple.
2067  * @param {?number} depth Depth the move has been computed to, or null.
2068  * @param {boolean} invert Whether black is to play.
2069  * @param {boolean=} depth_secondary_key
2070  * @return {number}
2071  */
2072 var compute_score_sort_key = function(score, depth, invert, depth_secondary_key) {
2073         var s;
2074         if (!score) {
2075                 return -10000000;
2076         }
2077         if (score[0] === 'm') {
2078                 if (score[1] > 0) {
2079                         // White mates.
2080                         s = 99999 - score[1];
2081                 } else {
2082                         // Black mates (note the double negative for score[1]).
2083                         s = -99999 - score[1];
2084                 }
2085         } else if (score[0] === 'd') {
2086                 s = 0;
2087         } else if (score[0] === 'cp') {
2088                 s = score[1];
2089         }
2090         if (s) {
2091                 if (invert) s = -s;
2092                 if (depth_secondary_key) {
2093                         return s * 200 + (depth || 0);
2094                 } else {
2095                         return s;
2096                 }
2097         } else {
2098                 return null;
2099         }
2100 }
2101
2102 /**
2103  * @param {Object} game
2104  */
2105 var switch_backend = function(game) {
2106         // Stop looking at historic data.
2107         current_display_line = null;
2108         current_display_move = null;
2109         displayed_analysis_data = null;
2110         if (current_historic_xhr) {
2111                 current_historic_xhr.abort();
2112         }
2113
2114         // If we already have a backend response going, abort it.
2115         if (current_analysis_xhr) {
2116                 current_analysis_xhr.abort();
2117         }
2118         if (current_hash_xhr) {
2119                 current_hash_xhr.abort();
2120         }
2121
2122         // Otherwise, we should have a timer going to start a new one.
2123         // Kill that, too.
2124         if (current_analysis_request_timer) {
2125                 clearTimeout(current_analysis_request_timer);
2126                 current_analysis_request_timer = null;
2127         }
2128         if (current_hash_display_timer) {
2129                 clearTimeout(current_hash_display_timer);
2130                 current_hash_display_timer = null;
2131         }
2132
2133         // Request an immediate fetch with the new backend.
2134         backend_url = game['url'];
2135         backend_hash_url = game['hashurl'];
2136         window.location.hash = '#' + game['id'];
2137         current_analysis_data = null;
2138         ims = 0;
2139         request_update();
2140 }
2141 window['switch_backend'] = switch_backend;
2142
2143 var init = function() {
2144         unique = get_unique();
2145
2146         // Load settings from HTML5 local storage if available.
2147         if (supports_html5_storage() && localStorage['enable_sound']) {
2148                 set_sound(parseInt(localStorage['enable_sound']));
2149         } else {
2150                 set_sound(false);
2151         }
2152         if (supports_html5_storage() && localStorage['sort_refutation_lines_by_score']) {
2153                 sort_refutation_lines_by_score = parseInt(localStorage['sort_refutation_lines_by_score']);
2154         } else {
2155                 sort_refutation_lines_by_score = true;
2156         }
2157
2158         // Create board.
2159         board = new window.ChessBoard('board', {
2160                 onMoveEnd: function() { board_is_animating = false; },
2161
2162                 draggable: true,
2163                 onDragStart: onDragStart,
2164                 onDrop: onDrop,
2165                 onSnapEnd: onSnapEnd
2166         });
2167         $("#board").on('mousedown', '.square-55d63', mousedownSquare);
2168         $("#board").on('mouseup', '.square-55d63', mouseupSquare);
2169
2170         request_update();
2171         $(window).resize(function() {
2172                 board.resize();
2173                 update_sparkline(displayed_analysis_data || current_analysis_data);
2174                 update_board_highlight();
2175                 redraw_arrows();
2176         });
2177         $(window).keyup(function(event) {
2178                 if (event.which == 39) {  // Left arrow.
2179                         next_move();
2180                 } else if (event.which == 37) {  // Right arrow.
2181                         prev_move();
2182                 } else if (event.which >= 49 && event.which <= 57) {  // 1-9.
2183                         var num = event.which - 49;
2184                         if (current_games && current_games.length >= num) {
2185                                 switch_backend(current_games[num]);
2186                         }
2187                 } else if (event.which == 78) {  // N.
2188                         next_game();
2189                 }
2190         });
2191         window.addEventListener('hashchange', possibly_switch_game_from_hash, false);
2192 };
2193 $(document).ready(init);
2194
2195 })();