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