Get rid of some cruft (pv_uci and sort_key), and rename pv_pretty/pretty_pv to just pv.
[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  *      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  *    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_name = function(refutation_lines, invert, a, b) {
555         var ska = refutation_lines[a]['pretty_move'];
556         var skb = refutation_lines[b]['pretty_move'];
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 FEN representation (e.g. Ne4) 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'][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'][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'][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>} 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, pv, move_num, toplay, scores, start_display_move_num, opt_limit, opt_showlast) {
638         display_lines.push({
639                 start_fen: start_fen,
640                 pv: 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 pv = display_line.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                 pv = 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 ret = '';
678         var i = 0;
679         if (opt_limit && opt_showlast && 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                 ret = '(<a class="move" href="javascript:collapse_history(false)">…</a>) ';
685                 i = pv.length - opt_limit;
686                 if (i % 2 == 1) {
687                         ++i;
688                 }
689                 move_num += i / 2;
690         } else if (toplay == 'B' && pv.length > 0) {
691                 var move = "<a class=\"move\" id=\"automove" + line_num + "-0\" href=\"javascript:show_line(" + line_num + ", " + 0 + ");\">" + pv[0] + "</a>";
692                 ret = move_num + '. … ' + move;
693                 toplay = 'W';
694                 ++i;
695                 ++move_num;
696         }
697         for ( ; i < pv.length; ++i) {
698                 var move = "<a class=\"move\" id=\"automove" + line_num + "-" + i + "\" href=\"javascript:show_line(" + line_num + ", " + i + ");\">" + pv[i] + "</a>";
699
700                 if (toplay == 'W') {
701                         if (i > opt_limit && !opt_showlast) {
702                                 return ret + ' (…)';
703                         }
704                         if (ret != '') {
705                                 ret += ' ';
706                         }
707                         ret += move_num + '. ' + move;
708                         ++move_num;
709                         toplay = 'B';
710                 } else {
711                         ret += ' ' + move;
712                         toplay = 'W';
713                 }
714         }
715         return ret;
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].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 = display_lines[1].scores;
769         var start_display_move_num = 0;
770         if (hash_refutation_lines) {
771                 base_line = current_display_line.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_name;
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'].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']), 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                         if (current_analysis_data && current_analysis_data['position']) {
903                                 var score;
904                                 if (current_analysis_data['position']['result']) {
905                                         score = " (" + current_analysis_data['position']['result'] + ")";
906                                 } else {
907                                         score = " (" + format_short_score(current_analysis_data['score']) + ")";
908                                 }
909                                 game_span.appendChild(document.createTextNode(score));
910                         }
911                 } else {
912                         // Some other game.
913                         var game_a = document.createElement("a");
914                         game_a.setAttribute("href", "#" + game['id']);
915                         game_a.appendChild(game_name);
916                         game_span.appendChild(game_a);
917
918                         var score;
919                         if (game['result']) {
920                                 score = " (" + game['result'] + ")";
921                         } else {
922                                 score = " (" + format_short_score(game['score']) + ")";
923                         }
924                         game_span.appendChild(document.createTextNode(score));
925                 }
926
927                 games_div.appendChild(game_span);
928         }
929 }
930
931 /**
932  * Try to find a running game that matches with the current hash,
933  * and switch to it if we're not already displaying it.
934  */
935 var possibly_switch_game_from_hash = function() {
936         if (current_games === null) {
937                 return;
938         }
939
940         var hash = window.location.hash.replace(/^#/,'');
941         for (var i = 0; i < current_games.length; ++i) {
942                 if (current_games[i]['id'] === hash) {
943                         if (backend_url !== current_games[i]['url']) {
944                                 switch_backend(current_games[i]['url'], current_games[i]['hashurl']);
945                         }
946                         return;
947                 }
948         }
949 }
950
951 /** Update all the HTML on the page, based on current global state.
952  */
953 var update_board = function() {
954         var data = displayed_analysis_data || current_analysis_data;
955         var current_data = current_analysis_data;  // Convenience alias.
956
957         display_lines = [];
958
959         // Print the history. This is pretty much the only thing that's
960         // unconditionally taken from current_data (we're not interested in
961         // historic history).
962         if (current_data['position']['pretty_history']) {
963                 add_pv('start', current_data['position']['pretty_history'], 1, 'W', null, 0, 8, true);
964         } else {
965                 display_lines.push(null);
966         }
967         update_history();
968
969         // Games currently in progress, if any.
970         if (current_data['games']) {
971                 current_games = current_data['games'];
972                 possibly_switch_game_from_hash();
973         } else {
974                 current_games = null;
975         }
976         update_game_list(current_games);
977
978         // The headline. Names are always fetched from current_data;
979         // the rest can depend a bit.
980         var headline;
981         if (current_data &&
982             current_data['position']['player_w'] && current_data['position']['player_b']) {
983                 headline = current_data['position']['player_w'] + '–' +
984                         current_data['position']['player_b'] + ', analysis';
985         } else {
986                 headline = 'Analysis';
987         }
988
989         // Credits, where applicable. Note that we don't want the footer to change a lot
990         // when e.g. viewing history, so if any of these changed during the game,
991         // use the current one still.
992         if (current_data['using_lomonosov']) {
993                 $("#lomonosov").show();
994         } else {
995                 $("#lomonosov").hide();
996         }
997
998         // Credits: The engine name/version.
999         if (current_data['engine'] && current_data['engine']['name'] !== null) {
1000                 $("#engineid").text(current_data['engine']['name']);
1001         }
1002
1003         // Credits: The engine URL.
1004         if (current_data['engine'] && current_data['engine']['url']) {
1005                 $("#engineid").attr("href", current_data['engine']['url']);
1006         } else {
1007                 $("#engineid").removeAttr("href");
1008         }
1009
1010         // Credits: Engine details.
1011         if (current_data['engine'] && current_data['engine']['details']) {
1012                 $("#enginedetails").text(" (" + current_data['engine']['details'] + ")");
1013         } else {
1014                 $("#enginedetails").text("");
1015         }
1016
1017         // Credits: Move source, possibly with URL.
1018         if (current_data['move_source'] && current_data['move_source_url']) {
1019                 $("#movesource").text("Moves provided by ");
1020                 var movesource_a = document.createElement("a");
1021                 movesource_a.setAttribute("href", current_data['move_source_url']);
1022                 var movesource_text = document.createTextNode(current_data['move_source']);
1023                 movesource_a.appendChild(movesource_text);
1024                 var movesource_period = document.createTextNode(".");
1025                 document.getElementById("movesource").appendChild(movesource_a);
1026                 document.getElementById("movesource").appendChild(movesource_period);
1027         } else if (current_data['move_source']) {
1028                 $("#movesource").text("Moves provided by " + current_data['move_source'] + ".");
1029         } else {
1030                 $("#movesource").text("");
1031         }
1032
1033         var last_move;
1034         if (displayed_analysis_data) {
1035                 // Displaying some non-current position, pick out the last move
1036                 // from the history. This will work even if the fetch failed.
1037                 last_move = format_halfmove_with_number(
1038                         current_display_line.pv[current_display_move],
1039                         current_display_move + 1);
1040                 headline += ' after ' + last_move;
1041         } else if (data['position']['last_move'] !== 'none') {
1042                 last_move = format_move_with_number(
1043                         data['position']['last_move'],
1044                         data['position']['move_num'],
1045                         data['position']['toplay'] == 'W');
1046                 headline += ' after ' + last_move;
1047         } else {
1048                 last_move = null;
1049         }
1050         $("#headline").text(headline);
1051
1052         // The <title> contains a very brief headline.
1053         var title_elems = [];
1054         if (data['position'] && data['position']['result']) {
1055                 title_elems.push(data['position']['result']);
1056         } else if (data['score']) {
1057                 title_elems.push(format_short_score(data['score']));
1058         }
1059         if (last_move !== null) {
1060                 title_elems.push(last_move);
1061         }
1062
1063         if (title_elems.length != 0) {
1064                 document.title = '(' + title_elems.join(', ') + ') analysis.sesse.net';
1065         } else {
1066                 document.title = 'analysis.sesse.net';
1067         }
1068
1069         // The last move (shown by highlighting the from and to squares).
1070         if (data['position'] && data['position']['last_move_uci']) {
1071                 highlight_from = data['position']['last_move_uci'].substr(0, 2);
1072                 highlight_to = data['position']['last_move_uci'].substr(2, 2);
1073         } else if (current_display_line_is_history && current_display_move >= 0) {
1074                 // We don't have historic analysis for this position, but we
1075                 // can reconstruct what the last move was by just replaying
1076                 // from the start.
1077                 var hiddenboard = chess_from(null, current_display_line.pv, current_display_move);
1078                 var moves = hiddenboard.history({ verbose: true });
1079                 var last_move = moves.pop();
1080                 highlight_from = last_move.from;
1081                 highlight_to = last_move.to;
1082         } else {
1083                 highlight_from = highlight_to = undefined;
1084         }
1085         update_board_highlight();
1086
1087         if (data['failed']) {
1088                 $("#score").text("No analysis for this move");
1089                 $("#pvtitle").text("PV:");
1090                 $("#pv").empty();
1091                 $("#searchstats").html("&nbsp;");
1092                 $("#refutationlines").empty();
1093                 $("#whiteclock").empty();
1094                 $("#blackclock").empty();
1095                 refutation_lines = [];
1096                 update_refutation_lines();
1097                 clear_arrows();
1098                 update_displayed_line();
1099                 update_move_highlight();
1100                 return;
1101         }
1102
1103         update_clock();
1104
1105         // The score.
1106         if (current_display_line && !current_display_line_is_history) {
1107                 var score;
1108                 if (current_display_line.scores && current_display_line.scores.length > 0) {
1109                         for (var i = 0; i < current_display_line.scores.length; ++i) {
1110                                 if (current_display_move < current_display_line.scores[i].first_move) {
1111                                         break;
1112                                 }
1113                                 score = current_display_line.scores[i].score;
1114                         }
1115                 }
1116                 if (score) {
1117                         $("#score").text(format_long_score(score));
1118                 } else {
1119                         $("#score").text("No score for this line");
1120                 }
1121         } else if (data['score']) {
1122                 $("#score").text(format_long_score(data['score']));
1123         }
1124
1125         // The search stats.
1126         if (data['searchstats']) {
1127                 $("#searchstats").html(data['searchstats']);
1128         } else if (data['tablebase'] == 1) {
1129                 $("#searchstats").text("Tablebase result");
1130         } else if (data['nodes'] && data['nps'] && data['depth']) {
1131                 var stats = thousands(data['nodes']) + ' nodes, ' + thousands(data['nps']) + ' nodes/sec, depth ' + data['depth'] + ' ply';
1132                 if (data['seldepth']) {
1133                         stats += ' (' + data['seldepth'] + ' selective)';
1134                 }
1135                 if (data['tbhits'] && data['tbhits'] > 0) {
1136                         if (data['tbhits'] == 1) {
1137                                 stats += ', one Syzygy hit';
1138                         } else {
1139                                 stats += ', ' + thousands(data['tbhits']) + ' Syzygy hits';
1140                         }
1141                 }
1142
1143                 $("#searchstats").text(stats);
1144         } else {
1145                 $("#searchstats").text("");
1146         }
1147
1148         // Update the board itself.
1149         base_fen = data['position']['fen'];
1150         update_displayed_line();
1151
1152         // Print the PV.
1153         $("#pvtitle").text("PV:");
1154
1155         var scores = [{ first_move: -1, score: data['score'] }];
1156         $("#pv").html(add_pv(data['position']['fen'], data['pv'], data['position']['move_num'], data['position']['toplay'], scores, 0));
1157
1158         // Update the PV arrow.
1159         clear_arrows();
1160         if (data['pv'].length >= 1) {
1161                 var hiddenboard = new Chess(base_fen);
1162
1163                 // draw a continuation arrow as long as it's the same piece
1164                 var last_to;
1165                 for (var i = 0; i < data['pv'].length; i += 2) {
1166                         var move = hiddenboard.move(data['pv'][i]);
1167                         if ((i >= 2 && move.from != last_to) ||
1168                              interfering_arrow(move.from, move.to)) {
1169                                 break;
1170                         }
1171                         create_arrow(move.from, move.to, '#f66', 6, 20);
1172                         last_to = move.from;
1173                         hiddenboard.move(data['pv'][i + 1]);  // To keep continuity.
1174                 }
1175
1176                 var alt_moves = find_nonstupid_moves(data, 30, data['position']['toplay'] === 'B');
1177                 for (var i = 1; i < alt_moves.length && i < 3; ++i) {
1178                         hiddenboard = new Chess(base_fen);
1179                         var move = hiddenboard.move(alt_moves[i]);
1180                         create_arrow(move.from, move.to, '#f66', 1, 10);
1181                 }
1182         }
1183
1184         // See if all semi-reasonable moves have only one possible response.
1185         if (data['pv'].length >= 2) {
1186                 var nonstupid_moves = find_nonstupid_moves(data, 300, data['position']['toplay'] === 'B');
1187                 var response;
1188                 {
1189                         var hiddenboard = new Chess(base_fen);
1190                         hiddenboard.move(data['pv'][0]);
1191                         response = hiddenboard.move(data['pv'][1]);
1192                 }
1193                 for (var i = 0; i < nonstupid_moves.length; ++i) {
1194                         if (nonstupid_moves[i] == data['pv'][0]) {
1195                                 // ignore the PV move for refutation lines.
1196                                 continue;
1197                         }
1198                         if (!data['refutation_lines'] ||
1199                             !data['refutation_lines'][nonstupid_moves[i]] ||
1200                             !data['refutation_lines'][nonstupid_moves[i]]['pv'] ||
1201                             data['refutation_lines'][nonstupid_moves[i]]['pv'].length < 1) {
1202                                 // Incomplete PV, abort.
1203                                 response = undefined;
1204                                 break;
1205                         }
1206                         var line = data['refutation_lines'][nonstupid_moves[i]];
1207                         var hiddenboard = new Chess(base_fen);
1208                         hiddenboard.move(line['pv'][0]);
1209                         var this_response = hiddenboard.move(line['pv'][1]);
1210                         if (response.from !== this_response.from || response.to !== this_response.to) {
1211                                 // Different response depending on lines, abort.
1212                                 response = undefined;
1213                                 break;
1214                         }
1215                 }
1216
1217                 if (nonstupid_moves.length > 0 && response !== undefined) {
1218                         create_arrow(response.from, response.to, '#66f', 6, 20);
1219                 }
1220         }
1221
1222         // Update the refutation lines.
1223         base_fen = data['position']['fen'];
1224         move_num = parseInt(data['position']['move_num']);
1225         toplay = data['position']['toplay'];
1226         refutation_lines = hash_refutation_lines || data['refutation_lines'];
1227         update_refutation_lines();
1228
1229         // Update the sparkline last, since its size depends on how everything else reflowed.
1230         update_sparkline(data);
1231 }
1232
1233 var update_sparkline = function(data) {
1234         if (data && data['score_history']) {
1235                 var first_move_num = undefined;
1236                 for (var halfmove_num in data['score_history']) {
1237                         halfmove_num = parseInt(halfmove_num);
1238                         if (first_move_num === undefined || halfmove_num < first_move_num) {
1239                                 first_move_num = halfmove_num;
1240                         }
1241                 }
1242                 if (first_move_num !== undefined) {
1243                         var last_move_num = data['position']['move_num'] * 2 - 3;
1244                         if (data['position']['toplay'] === 'B') {
1245                                 ++last_move_num;
1246                         }
1247
1248                         // Possibly truncate some moves if we don't have enough width.
1249                         // FIXME: Sometimes width() for #scorecontainer (and by extent,
1250                         // #scoresparkcontainer) on Chrome for mobile seems to start off
1251                         // at something very small, and then suddenly snap back into place.
1252                         // Figure out why.
1253                         var max_moves = Math.floor($("#scoresparkcontainer").width() / 5) - 5;
1254                         if (last_move_num - first_move_num > max_moves) {
1255                                 first_move_num = last_move_num - max_moves;
1256                         }
1257
1258                         var min_score = -100;
1259                         var max_score = 100;
1260                         var last_score = null;
1261                         var scores = [];
1262                         for (var halfmove_num = first_move_num; halfmove_num <= last_move_num; ++halfmove_num) {
1263                                 if (data['score_history'][halfmove_num]) {
1264                                         var score = compute_plot_score(data['score_history'][halfmove_num]);
1265                                         last_score = score;
1266                                         if (score < min_score) min_score = score;
1267                                         if (score > max_score) max_score = score;
1268                                 }
1269                                 scores.push(last_score);
1270                         }
1271                         if (data['score']) {
1272                                 scores.push(compute_plot_score(data['score']));
1273                         }
1274                         // FIXME: at some widths, calling sparkline() seems to push
1275                         // #scorecontainer under the board.
1276                         $("#scorespark").sparkline(scores, {
1277                                 type: 'bar',
1278                                 zeroColor: 'gray',
1279                                 chartRangeMin: min_score,
1280                                 chartRangeMax: max_score,
1281                                 tooltipFormatter: function(sparkline, options, fields) {
1282                                         return format_tooltip(data, fields[0].offset + first_move_num);
1283                                 }
1284                         });
1285                 } else {
1286                         $("#scorespark").text("");
1287                 }
1288         } else {
1289                 $("#scorespark").text("");
1290         }
1291 }
1292
1293 /**
1294  * @param {number} num_viewers
1295  */
1296 var update_num_viewers = function(num_viewers) {
1297         if (num_viewers === null) {
1298                 $("#numviewers").text("");
1299         } else if (num_viewers == 1) {
1300                 $("#numviewers").text("You are the only current viewer");
1301         } else {
1302                 $("#numviewers").text(num_viewers + " current viewers");
1303         }
1304 }
1305
1306 var update_clock = function() {
1307         clearTimeout(clock_timer);
1308
1309         var data = displayed_analysis_data || current_analysis_data;
1310         if (!data) return;
1311
1312         if (data['position']) {
1313                 var result = data['position']['result'];
1314                 if (result === '1-0') {
1315                         $("#whiteclock").text("1");
1316                         $("#blackclock").text("0");
1317                         $("#whiteclock").removeClass("running-clock");
1318                         $("#blackclock").removeClass("running-clock");
1319                         return;
1320                 }
1321                 if (result === '1/2-1/2') {
1322                         $("#whiteclock").text("1/2");
1323                         $("#blackclock").text("1/2");
1324                         $("#whiteclock").removeClass("running-clock");
1325                         $("#blackclock").removeClass("running-clock");
1326                         return;
1327                 }       
1328                 if (result === '0-1') {
1329                         $("#whiteclock").text("0");
1330                         $("#blackclock").text("1");
1331                         $("#whiteclock").removeClass("running-clock");
1332                         $("#blackclock").removeClass("running-clock");
1333                         return;
1334                 }
1335         }
1336
1337         var white_clock_ms = null;
1338         var black_clock_ms = null;
1339         var show_seconds = false;
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']['pretty_history'].length) {
1469                 var move;
1470                 var short_score;
1471                 if (halfmove_num === data['position']['pretty_history'].length) {
1472                         move = data['position']['last_move'];
1473                         short_score = format_short_score(data['score']);
1474                 } else {
1475                         move = data['position']['pretty_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']['pretty_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]['url'], current_games[next_game_num]['hashurl']);
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                 var line = display_lines[i];
1978                 if (line.pv[line.start_display_move_num] === move.san) {
1979                         show_line(i, 0);
1980                         return;
1981                 }
1982         }
1983
1984         // Shouldn't really be here if we have hash probes, but there's really
1985         // nothing we can do.
1986 }
1987 // End of dragging-related code.
1988
1989 var fmt_cp = function(v) {
1990         if (v === 0) {
1991                 return "0.00";
1992         } else if (v > 0) {
1993                 return "+" + (v / 100).toFixed(2);
1994         } else {
1995                 v = -v;
1996                 return "-" + (v / 100).toFixed(2);
1997         }
1998 }
1999
2000 var format_short_score = function(score) {
2001         if (!score) {
2002                 return "???";
2003         }
2004         if (score[0] === 'm') {
2005                 if (score[2]) {  // Is a bound.
2006                         return score[2] + "\u00a0M " + score[1];
2007                 } else {
2008                         return "M " + score[1];
2009                 }
2010         } else if (score[0] === 'd') {
2011                 return "TB draw";
2012         } else if (score[0] === 'cp') {
2013                 if (score[2]) {  // Is a bound.
2014                         return score[2] + "\u00a0" + fmt_cp(score[1]);
2015                 } else {
2016                         return fmt_cp(score[1]);
2017                 }
2018         }
2019         return null;
2020 }
2021
2022 var format_long_score = function(score) {
2023         if (!score) {
2024                 return "???";
2025         }
2026         if (score[0] === 'm') {
2027                 if (score[1] > 0) {
2028                         return "White mates in " + score[1];
2029                 } else {
2030                         return "Black mates in " + (-score[1]);
2031                 }
2032         } else if (score[0] === 'd') {
2033                 return "Theoretical draw";
2034         } else if (score[0] === 'cp') {
2035                 return "Score: " + format_short_score(score);
2036         }
2037         return null;
2038 }
2039
2040 var compute_plot_score = function(score) {
2041         if (score[0] === 'm') {
2042                 if (score[1] > 0) {
2043                         return 500;
2044                 } else {
2045                         return -500;
2046                 }
2047         } else if (score[0] === 'd') {
2048                 return 0;
2049         } else if (score[0] === 'cp') {
2050                 if (score[1] > 500) {
2051                         return 500;
2052                 } else if (score[1] < -500) {
2053                         return -500;
2054                 } else {
2055                         return score[1];
2056                 }
2057         }
2058         return null;
2059 }
2060
2061 /**
2062  * @param score The score digest tuple.
2063  * @param {?number} depth Depth the move has been computed to, or null.
2064  * @param {boolean} invert Whether black is to play.
2065  * @return {number}
2066  */
2067 var compute_score_sort_key = function(score, depth, invert) {
2068         var s;
2069         if (!score) {
2070                 return -10000000;
2071         }
2072         if (score[0] === 'm') {
2073                 if (score[1] > 0) {
2074                         // White mates.
2075                         s = 99999 - score[1];
2076                 } else {
2077                         // Black mates (note the double negative for score[1]).
2078                         s = -99999 - score[1];
2079                 }
2080         } else if (score[0] === 'd') {
2081                 s = 0;
2082         } else if (score[0] === 'cp') {
2083                 s = score[1];
2084         }
2085         if (s) {
2086                 if (invert) s = -s;
2087                 return s * 200 + (depth || 0);
2088         } else {
2089                 return null;
2090         }
2091 }
2092
2093 /**
2094  * @param {string} new_backend_url
2095  */
2096 var switch_backend = function(new_backend_url, new_backend_hash_url) {
2097         // Stop looking at historic data.
2098         current_display_line = null;
2099         current_display_move = null;
2100         displayed_analysis_data = null;
2101         if (current_historic_xhr) {
2102                 current_historic_xhr.abort();
2103         }
2104
2105         // If we already have a backend response going, abort it.
2106         if (current_analysis_xhr) {
2107                 current_analysis_xhr.abort();
2108         }
2109         if (current_hash_xhr) {
2110                 current_hash_xhr.abort();
2111         }
2112
2113         // Otherwise, we should have a timer going to start a new one.
2114         // Kill that, too.
2115         if (current_analysis_request_timer) {
2116                 clearTimeout(current_analysis_request_timer);
2117                 current_analysis_request_timer = null;
2118         }
2119         if (current_hash_display_timer) {
2120                 clearTimeout(current_hash_display_timer);
2121                 current_hash_display_timer = null;
2122         }
2123
2124         // Request an immediate fetch with the new backend.
2125         backend_url = new_backend_url;
2126         backend_hash_url = new_backend_hash_url;
2127         current_analysis_data = null;
2128         ims = 0;
2129         request_update();
2130 }
2131 window['switch_backend'] = switch_backend;
2132
2133 var init = function() {
2134         unique = get_unique();
2135
2136         // Load settings from HTML5 local storage if available.
2137         if (supports_html5_storage() && localStorage['enable_sound']) {
2138                 set_sound(parseInt(localStorage['enable_sound']));
2139         } else {
2140                 set_sound(false);
2141         }
2142         if (supports_html5_storage() && localStorage['sort_refutation_lines_by_score']) {
2143                 sort_refutation_lines_by_score = parseInt(localStorage['sort_refutation_lines_by_score']);
2144         } else {
2145                 sort_refutation_lines_by_score = true;
2146         }
2147
2148         // Create board.
2149         board = new window.ChessBoard('board', {
2150                 onMoveEnd: function() { board_is_animating = false; },
2151
2152                 draggable: true,
2153                 onDragStart: onDragStart,
2154                 onDrop: onDrop,
2155                 onSnapEnd: onSnapEnd
2156         });
2157         $("#board").on('mousedown', '.square-55d63', mousedownSquare);
2158         $("#board").on('mouseup', '.square-55d63', mouseupSquare);
2159
2160         request_update();
2161         $(window).resize(function() {
2162                 board.resize();
2163                 update_sparkline(displayed_analysis_data || current_analysis_data);
2164                 update_board_highlight();
2165                 redraw_arrows();
2166         });
2167         $(window).keyup(function(event) {
2168                 if (event.which == 39) {  // Left arrow.
2169                         next_move();
2170                 } else if (event.which == 37) {  // Right arrow.
2171                         prev_move();
2172                 } else if (event.which >= 49 && event.which <= 57) {  // 1-9.
2173                         var num = event.which - 49;
2174                         if (current_games && current_games.length >= num) {
2175                                 switch_backend(current_games[num]['url'], current_games[num]['hashurl']);
2176                         }
2177                 } else if (event.which == 78) {  // N.
2178                         next_game();
2179                 }
2180         });
2181         window.addEventListener('hashchange', possibly_switch_game_from_hash, false);
2182 };
2183 $(document).ready(init);
2184
2185 })();