Fix the PV check.
[remoteglot] / www / js / remoteglot.js
1 (function() {
2
3 /**
4  * Version of this script. If the server returns a version larger than
5  * this, it is a sign we should reload to upgrade ourselves.
6  *
7  * @type {Number}
8  * @const
9  * @private */
10 var SCRIPT_VERSION = 2016032202;
11
12 /**
13  * The current backend URL.
14  *
15  * @type {!string}
16  * @private
17  */
18 var backend_url = "/analysis.pl";
19 var backend_hash_url = "/hash";
20
21 /** @type {window.ChessBoard} @private */
22 var board = null;
23
24 /** @type {boolean} @private */
25 var board_is_animating = false;
26
27 /**
28  * The most recent analysis data we have from the server
29  * (about the most recent position).
30  *
31  * @type {?Object}
32  * @private */
33 var current_analysis_data = null;
34
35 /**
36  * If we are displaying previous analysis or from hash, this is non-null,
37  * and will override most of current_analysis_data.
38  *
39  * @type {?Object}
40  * @private
41  */
42 var displayed_analysis_data = null;
43
44 /**
45  * Games currently in progress, if any.
46  *
47  * @type {?Array.<{
48  *      name: string,
49  *      url: string,
50  *      hashurl: string,
51  *      id: string,
52  *      score: Object=,
53  *      result: string=,
54  * }>}
55  * @private
56  */
57 var current_games = null;
58
59 /** @type {Array.<{
60  *      from_col: number,
61  *      from_row: number,
62  *      to_col: number,
63  *      to_row: number,
64  *      line_width: number,
65  *      arrow_size: number,
66  *      fg_color: string
67  * }>}
68  * @private
69  */
70 var arrows = [];
71
72 /** @type {Array.<Array.<boolean>>} */
73 var occupied_by_arrows = [];
74
75 /** Currently displayed refutation lines (on-screen).
76  * Can either come from the current_analysis_data, displayed_analysis_data,
77  * or hash_refutation_lines.
78  */
79 var refutation_lines = [];
80
81 /** Refutation lines from current hash probe.
82  *
83  * If non-null, will override refutation lines from the base position.
84  * Note that these are relative to display_fen, not base_fen.
85  */
86 var hash_refutation_lines = null;
87
88 /** @type {!number} @private */
89 var move_num = 1;
90
91 /** @type {!string} @private */
92 var toplay = 'W';
93
94 /** @type {number} @private */
95 var ims = 0;
96
97 /** @type {boolean} @private */
98 var sort_refutation_lines_by_score = true;
99
100 /** @type {boolean} @private */
101 var truncate_display_history = true;
102
103 /** @type {!string|undefined} @private */
104 var highlight_from = undefined;
105
106 /** @type {!string|undefined} @private */
107 var highlight_to = undefined;
108
109 /** The HTML object of the move currently being highlighted (in red).
110  * @type {?jQuery}
111  * @private */
112 var highlighted_move = null;
113
114 /** Currently suggested/recommended move when dragging.
115  * @type {?{from: !string, to: !string}}
116  * @private
117  */
118 var recommended_move = null;
119
120 /** If reverse-dragging (dragging from the destination square to the
121  * source square), the destination square.
122  * @type {?string}
123  * @private
124  */
125 var reverse_dragging_from = null;
126
127 /** @type {?number} @private */
128 var unique = null;
129
130 /** @type {boolean} @private */
131 var enable_sound = false;
132
133 /**
134  * Our best estimate of how many milliseconds we need to add to 
135  * new Date() to get the true UTC time. Calibrated against the
136  * server clock.
137  *
138  * @type {?number}
139  * @private
140  */
141 var client_clock_offset_ms = null;
142
143 var clock_timer = null;
144
145 /** The current position being analyzed, represented as a FEN string.
146  * Note that this is not necessarily the same as display_fen.
147  * @type {?string}
148  * @private
149  */
150 var base_fen = null;
151
152 /** The current position on the board, represented as a FEN string.
153  * Note that board.fen() does not contain e.g. who is to play.
154  * @type {?string}
155  * @private
156  */
157 var display_fen = null;
158
159 /** @typedef {{
160  *    start_fen: string,
161  *    pv: Array.<string>,
162  *    move_num: number,
163  *    toplay: string,
164  *    scores: Array<{first_move: number, score: Object}>,
165  *    start_display_move_num: number
166  * }} DisplayLine
167  *
168  * "start_display_move_num" is the (half-)move number to start displaying the PV at.
169  * "score" is also evaluated at this point.
170  */
171
172 /** All PVs that we currently know of.
173  *
174  * Element 0 is history (or null if no history).
175  * Element 1 is current main PV, or explored line if nowhere else on the screen.
176  * All remaining elements are refutation lines (multi-PV).
177  *
178  * @type {Array.<DisplayLine>}
179  * @private
180  */
181 var display_lines = [];
182
183 /** @type {?DisplayLine} @private */
184 var current_display_line = null;
185
186 /** @type {boolean} @private */
187 var current_display_line_is_history = false;
188
189 /** @type {?number} @private */
190 var current_display_move = null;
191
192 /**
193  * The current backend request to get main analysis (not history), if any,
194  * so that we can abort it.
195  *
196  * @type {?jqXHR}
197  * @private
198  */
199 var current_analysis_xhr = null;
200
201 /**
202  * The current timer to fire off a request to get main analysis (not history),
203  * if any, so that we can abort it.
204  *
205  * @type {?Number}
206  * @private
207  */
208 var current_analysis_request_timer = null;
209
210 /**
211  * The current backend request to get historic data, if any.
212  *
213  * @type {?jqXHR}
214  * @private
215  */
216 var current_historic_xhr = null;
217
218 /**
219  * The current backend request to get hash probes, if any, so that we can abort it.
220  *
221  * @type {?jqXHR}
222  * @private
223  */
224 var current_hash_xhr = null;
225
226 /**
227  * The current timer to display hash probe information (it could be waiting on the
228  * board to stop animating), if any, so that we can abort it.
229  *
230  * @type {?Number}
231  * @private
232  */
233 var current_hash_display_timer = null;
234
235 var supports_html5_storage = function() {
236         try {
237                 return 'localStorage' in window && window['localStorage'] !== null;
238         } catch (e) {
239                 return false;
240         }
241 }
242
243 // Make the unique token persistent so people refreshing the page won't count twice.
244 // Of course, you can never fully protect against people deliberately wanting to spam.
245 var get_unique = function() {
246         var use_local_storage = supports_html5_storage();
247         if (use_local_storage && localStorage['unique']) {
248                 return localStorage['unique'];
249         }
250         var unique = Math.random();
251         if (use_local_storage) {
252                 localStorage['unique'] = unique;
253         }
254         return unique;
255 }
256
257 var request_update = function() {
258         current_analysis_request_timer = null;
259
260         current_analysis_xhr = $.ajax({
261                 url: backend_url + "?ims=" + ims + "&unique=" + unique
262         }).done(function(data, textstatus, xhr) {
263                 sync_server_clock(xhr.getResponseHeader('Date'));
264                 ims = xhr.getResponseHeader('X-RGLM');
265                 var num_viewers = xhr.getResponseHeader('X-RGNV');
266                 var new_data;
267                 if (Array.isArray(data)) {
268                         new_data = JSON.parse(JSON.stringify(current_analysis_data));
269                         JSON_delta.patch(new_data, data);
270                 } else {
271                         new_data = data;
272                 }
273
274                 var minimum_version = xhr.getResponseHeader('X-RGMV');
275                 if (minimum_version && minimum_version > SCRIPT_VERSION) {
276                         // Upgrade to latest version with a force-reload.
277                         location.reload(true);
278                 }
279
280                 // Verify that the PV makes sense.
281                 var valid = true;
282                 if (new_data['pv']) {
283                         var hiddenboard = new Chess(new_data['position']['fen']);
284                         for (var i = 0; i < new_data['pv'].length; ++i) {
285                                 if (hiddenboard.move(new_data['pv'][i]) === null) {
286                                         valid = false;
287                                         break;
288                                 }
289                         }
290                 }
291
292                 var timeout = 100;
293                 if (valid) {
294                         possibly_play_sound(current_analysis_data, new_data);
295                         current_analysis_data = new_data;
296                         update_board();
297                         update_num_viewers(num_viewers);
298                 } else {
299                         console.log("Received invalid update, waiting five seconds and trying again.");
300                         timeout = 5000;
301                 }
302
303                 // Next update.
304                 current_analysis_request_timer = setTimeout(function() { request_update(); }, timeout);
305         }).fail(function(jqXHR, textStatus, errorThrown) {
306                 if (textStatus === "abort") {
307                         // Aborted because we are switching backends. Abandon and don't retry,
308                         // because another one is already started for us.
309                 } else {
310                         // Backend error or similar. Wait ten seconds, then try again.
311                         current_analysis_request_timer = setTimeout(function() { request_update(); }, 10000);
312                 }
313         });
314 }
315
316 var possibly_play_sound = function(old_data, new_data) {
317         if (!enable_sound) {
318                 return;
319         }
320         if (old_data === null) {
321                 return;
322         }
323         var ding = document.getElementById('ding');
324         if (ding && ding.play) {
325                 if (old_data['position'] && old_data['position']['fen'] &&
326                     new_data['position'] && new_data['position']['fen'] &&
327                     (old_data['position']['fen'] !== new_data['position']['fen'] ||
328                      old_data['position']['move_num'] !== new_data['position']['move_num'])) {
329                         ding.play();
330                 }
331         }
332 }
333
334 /**
335  * @type {!string} server_date_string
336  */
337 var sync_server_clock = function(server_date_string) {
338         var server_time_ms = new Date(server_date_string).getTime();
339         var client_time_ms = new Date().getTime();
340         var estimated_offset_ms = server_time_ms - client_time_ms;
341
342         // In order not to let the noise move us too much back and forth
343         // (the server only has one-second resolution anyway), we only
344         // change an existing skew if we are at least five seconds off.
345         if (client_clock_offset_ms === null ||
346             Math.abs(estimated_offset_ms - client_clock_offset_ms) > 5000) {
347                 client_clock_offset_ms = estimated_offset_ms;
348         }
349 }
350
351 var clear_arrows = function() {
352         for (var i = 0; i < arrows.length; ++i) {
353                 if (arrows[i].svg) {
354                         if (arrows[i].svg.parentElement) {
355                                 arrows[i].svg.parentElement.removeChild(arrows[i].svg);
356                         }
357                         delete arrows[i].svg;
358                 }
359         }
360         arrows = [];
361
362         occupied_by_arrows = [];
363         for (var y = 0; y < 8; ++y) {
364                 occupied_by_arrows.push([false, false, false, false, false, false, false, false]);
365         }
366 }
367
368 var redraw_arrows = function() {
369         for (var i = 0; i < arrows.length; ++i) {
370                 position_arrow(arrows[i]);
371         }
372 }
373
374 /** @param {!number} x
375  * @return {!number}
376  */
377 var sign = function(x) {
378         if (x > 0) {
379                 return 1;
380         } else if (x < 0) {
381                 return -1;
382         } else {
383                 return 0;
384         }
385 }
386
387 /** See if drawing this arrow on the board would cause unduly amount of confusion.
388  * @param {!string} from The square the arrow is from (e.g. e4).
389  * @param {!string} to The square the arrow is to (e.g. e4).
390  * @return {boolean}
391  */
392 var interfering_arrow = function(from, to) {
393         var from_col = from.charCodeAt(0) - "a1".charCodeAt(0);
394         var from_row = from.charCodeAt(1) - "a1".charCodeAt(1);
395         var to_col   = to.charCodeAt(0) - "a1".charCodeAt(0);
396         var to_row   = to.charCodeAt(1) - "a1".charCodeAt(1);
397
398         occupied_by_arrows[from_row][from_col] = true;
399
400         // Knight move: Just check that we haven't been at the destination before.
401         if ((Math.abs(to_col - from_col) == 2 && Math.abs(to_row - from_row) == 1) ||
402             (Math.abs(to_col - from_col) == 1 && Math.abs(to_row - from_row) == 2)) {
403                 return occupied_by_arrows[to_row][to_col];
404         }
405
406         // Sliding piece: Check if anything except the from-square is seen before.
407         var dx = sign(to_col - from_col);
408         var dy = sign(to_row - from_row);
409         var x = from_col;
410         var y = from_row;
411         do {
412                 x += dx;
413                 y += dy;
414                 if (occupied_by_arrows[y][x]) {
415                         return true;
416                 }
417                 occupied_by_arrows[y][x] = true;
418         } while (x != to_col || y != to_row);
419
420         return false;
421 }
422
423 /** Find a point along the coordinate system given by the given line,
424  * <t> units forward from the start of the line, <u> units to the right of it.
425  * @param {!number} x1
426  * @param {!number} x2
427  * @param {!number} y1
428  * @param {!number} y2
429  * @param {!number} t
430  * @param {!number} u
431  * @return {!string} The point in "x y" form, suitable for SVG paths.
432  */
433 var point_from_start = function(x1, y1, x2, y2, t, u) {
434         var dx = x2 - x1;
435         var dy = y2 - y1;
436
437         var norm = 1.0 / Math.sqrt(dx * dx + dy * dy);
438         dx *= norm;
439         dy *= norm;
440
441         var x = x1 + dx * t + dy * u;
442         var y = y1 + dy * t - dx * u;
443         return x + " " + y;
444 }
445
446 /** Find a point along the coordinate system given by the given line,
447  * <t> units forward from the end of the line, <u> units to the right of it.
448  * @param {!number} x1
449  * @param {!number} x2
450  * @param {!number} y1
451  * @param {!number} y2
452  * @param {!number} t
453  * @param {!number} u
454  * @return {!string} The point in "x y" form, suitable for SVG paths.
455  */
456 var point_from_end = function(x1, y1, x2, y2, t, u) {
457         var dx = x2 - x1;
458         var dy = y2 - y1;
459
460         var norm = 1.0 / Math.sqrt(dx * dx + dy * dy);
461         dx *= norm;
462         dy *= norm;
463
464         var x = x2 + dx * t + dy * u;
465         var y = y2 + dy * t - dx * u;
466         return x + " " + y;
467 }
468
469 var position_arrow = function(arrow) {
470         if (arrow.svg) {
471                 if (arrow.svg.parentElement) {
472                         arrow.svg.parentElement.removeChild(arrow.svg);
473                 }
474                 delete arrow.svg;
475         }
476         if (current_display_line !== null && !current_display_line_is_history) {
477                 return;
478         }
479
480         var pos = $(".square-a8").position();
481
482         var zoom_factor = $("#board").width() / 400.0;
483         var line_width = arrow.line_width * zoom_factor;
484         var arrow_size = arrow.arrow_size * zoom_factor;
485
486         var square_width = $(".square-a8").width();
487         var from_y = (7 - arrow.from_row + 0.5)*square_width;
488         var to_y = (7 - arrow.to_row + 0.5)*square_width;
489         var from_x = (arrow.from_col + 0.5)*square_width;
490         var to_x = (arrow.to_col + 0.5)*square_width;
491
492         var SVG_NS = "http://www.w3.org/2000/svg";
493         var XHTML_NS = "http://www.w3.org/1999/xhtml";
494         var svg = document.createElementNS(SVG_NS, "svg");
495         svg.setAttribute("width", /** @type{number} */ ($("#board").width()));
496         svg.setAttribute("height", /** @type{number} */ ($("#board").height()));
497         svg.setAttribute("style", "position: absolute");
498         svg.setAttribute("position", "absolute");
499         svg.setAttribute("version", "1.1");
500         svg.setAttribute("class", "c1");
501         svg.setAttribute("xmlns", XHTML_NS);
502
503         var x1 = from_x;
504         var y1 = from_y;
505         var x2 = to_x;
506         var y2 = to_y;
507
508         // Draw the line.
509         var outline = document.createElementNS(SVG_NS, "path");
510         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));
511         outline.setAttribute("xmlns", XHTML_NS);
512         outline.setAttribute("stroke", "#666");
513         outline.setAttribute("stroke-width", line_width + 2);
514         outline.setAttribute("fill", "none");
515         svg.appendChild(outline);
516
517         var path = document.createElementNS(SVG_NS, "path");
518         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));
519         path.setAttribute("xmlns", XHTML_NS);
520         path.setAttribute("stroke", arrow.fg_color);
521         path.setAttribute("stroke-width", line_width);
522         path.setAttribute("fill", "none");
523         svg.appendChild(path);
524
525         // Then the arrow head.
526         var head = document.createElementNS(SVG_NS, "path");
527         head.setAttribute("d",
528                 "M " +  point_from_end(x1, y1, x2, y2, 0, 0) +
529                 " L " + point_from_end(x1, y1, x2, y2, -arrow_size, -arrow_size / 2) +
530                 " L " + point_from_end(x1, y1, x2, y2, -arrow_size * .623, 0.0) +
531                 " L " + point_from_end(x1, y1, x2, y2, -arrow_size, arrow_size / 2) +
532                 " L " + point_from_end(x1, y1, x2, y2, 0, 0));
533         head.setAttribute("xmlns", XHTML_NS);
534         head.setAttribute("stroke", "#000");
535         head.setAttribute("stroke-width", "1");
536         head.setAttribute("fill", arrow.fg_color);
537         svg.appendChild(head);
538
539         $(svg).css({ top: pos.top, left: pos.left, 'pointer-events': 'none' });
540         document.body.appendChild(svg);
541         arrow.svg = svg;
542 }
543
544 /**
545  * @param {!string} from_square
546  * @param {!string} to_square
547  * @param {!string} fg_color
548  * @param {number} line_width
549  * @param {number} arrow_size
550  */
551 var create_arrow = function(from_square, to_square, fg_color, line_width, arrow_size) {
552         var from_col = from_square.charCodeAt(0) - "a1".charCodeAt(0);
553         var from_row = from_square.charCodeAt(1) - "a1".charCodeAt(1);
554         var to_col   = to_square.charCodeAt(0) - "a1".charCodeAt(0);
555         var to_row   = to_square.charCodeAt(1) - "a1".charCodeAt(1);
556
557         // Create arrow.
558         var arrow = {
559                 from_col: from_col,
560                 from_row: from_row,
561                 to_col: to_col,
562                 to_row: to_row,
563                 line_width: line_width,
564                 arrow_size: arrow_size,
565                 fg_color: fg_color
566         };
567
568         position_arrow(arrow);
569         arrows.push(arrow);
570 }
571
572 // Note: invert is ignored.
573 var compare_by_name = function(refutation_lines, invert, a, b) {
574         var ska = refutation_lines[a]['move'];
575         var skb = refutation_lines[b]['move'];
576         if (ska < skb) return -1;
577         if (ska > skb) return 1;
578         return 0;
579 };
580
581 var compare_by_score = function(refutation_lines, invert, a, b) {
582         var sa = compute_score_sort_key(refutation_lines[b]['score'], refutation_lines[b]['depth'], invert);
583         var sb = compute_score_sort_key(refutation_lines[a]['score'], refutation_lines[a]['depth'], invert);
584         return sa - sb;
585 }
586
587 /**
588  * Fake multi-PV using the refutation lines. Find all “relevant” moves,
589  * sorted by quality, descending.
590  *
591  * @param {!Object} data
592  * @param {number} margin The maximum number of centipawns worse than the
593  *     best move can be and still be included.
594  * @param {boolean} invert Whether black is to play.
595  * @return {Array.<string>} The FEN representation (e.g. Ne4) of all
596  *     moves, in score order.
597  */
598 var find_nonstupid_moves = function(data, margin, invert) {
599         // First of all, if there are any moves that are more than 0.5 ahead of
600         // the primary move, the refutation lines are probably bunk, so just
601         // kill them all. 
602         var best_score = undefined;
603         var pv_score = undefined;
604         for (var move in data['refutation_lines']) {
605                 var line = data['refutation_lines'][move];
606                 var score = compute_score_sort_key(line['score'], line['depth'], invert, false);
607                 if (move == data['pv'][0]) {
608                         pv_score = score;
609                 }
610                 if (best_score === undefined || score > best_score) {
611                         best_score = score;
612                 }
613                 if (line['depth'] < 8) {
614                         return [];
615                 }
616         }
617
618         if (best_score - pv_score > 50) {
619                 return [];
620         }
621
622         // Now find all moves that are within “margin” of the best score.
623         // The PV move will always be first.
624         var moves = [];
625         for (var move in data['refutation_lines']) {
626                 var line = data['refutation_lines'][move];
627                 var score = compute_score_sort_key(line['score'], line['depth'], invert);
628                 if (move != data['pv'][0] && best_score - score <= margin) {
629                         moves.push(move);
630                 }
631         }
632         moves = moves.sort(function(a, b) { return compare_by_score(data['refutation_lines'], data['position']['toplay'] === 'B', a, b) });
633         moves.unshift(data['pv'][0]);
634
635         return moves;
636 }
637
638 /**
639  * @param {number} x
640  * @return {!string}
641  */
642 var thousands = function(x) {
643         return String(x).split('').reverse().join('').replace(/(\d{3}\B)/g, '$1,').split('').reverse().join('');
644 }
645
646 /**
647  * @param {!string} start_fen
648  * @param {Array.<string>} pv
649  * @param {number} move_num
650  * @param {!string} toplay
651  * @param {Array<{ first_move: integer, score: Object }>} scores
652  * @param {number} start_display_move_num
653  * @param {number=} opt_limit
654  * @param {boolean=} opt_showlast
655  */
656 var add_pv = function(start_fen, pv, move_num, toplay, scores, start_display_move_num, opt_limit, opt_showlast) {
657         display_lines.push({
658                 start_fen: start_fen,
659                 pv: pv,
660                 move_num: parseInt(move_num),
661                 toplay: toplay,
662                 scores: scores,
663                 start_display_move_num: start_display_move_num
664         });
665         return print_pv(display_lines.length - 1, opt_limit, opt_showlast);
666 }
667
668 /**
669  * @param {number} line_num
670  * @param {number=} opt_limit If set, show at most this number of moves.
671  * @param {boolean=} opt_showlast If limit is set, show the last moves instead of the first ones.
672  */
673 var print_pv = function(line_num, opt_limit, opt_showlast) {
674         var display_line = display_lines[line_num];
675         var pv = display_line.pv;
676         var move_num = display_line.move_num;
677         var toplay = display_line.toplay;
678
679         // Truncate PV at the start if needed.
680         var start_display_move_num = display_line.start_display_move_num;
681         if (start_display_move_num > 0) {
682                 pv = pv.slice(start_display_move_num);
683                 var to_add = start_display_move_num;
684                 if (toplay === 'B') {
685                         ++move_num;
686                         toplay = 'W';
687                         --to_add;
688                 }
689                 if (to_add % 2 == 1) {
690                         toplay = 'B';
691                         --to_add;
692                 }
693                 move_num += to_add / 2;
694         }
695
696         var ret = '';
697         var i = 0;
698         if (opt_limit && opt_showlast && pv.length > opt_limit) {
699                 // Truncate the PV at the beginning (instead of at the end).
700                 // We assume here that toplay is 'W'. We also assume that if
701                 // opt_showlast is set, then it is the history, and thus,
702                 // the UI should be to expand the history.
703                 ret = '(<a class="move" href="javascript:collapse_history(false)">…</a>) ';
704                 i = pv.length - opt_limit;
705                 if (i % 2 == 1) {
706                         ++i;
707                 }
708                 move_num += i / 2;
709         } else if (toplay == 'B' && pv.length > 0) {
710                 var move = "<a class=\"move\" id=\"automove" + line_num + "-0\" href=\"javascript:show_line(" + line_num + ", " + 0 + ");\">" + pv[0] + "</a>";
711                 ret = move_num + '. … ' + move;
712                 toplay = 'W';
713                 ++i;
714                 ++move_num;
715         }
716         for ( ; i < pv.length; ++i) {
717                 var move = "<a class=\"move\" id=\"automove" + line_num + "-" + i + "\" href=\"javascript:show_line(" + line_num + ", " + i + ");\">" + pv[i] + "</a>";
718
719                 if (toplay == 'W') {
720                         if (i > opt_limit && !opt_showlast) {
721                                 return ret + ' (…)';
722                         }
723                         if (ret != '') {
724                                 ret += ' ';
725                         }
726                         ret += move_num + '. ' + move;
727                         ++move_num;
728                         toplay = 'B';
729                 } else {
730                         ret += ' ' + move;
731                         toplay = 'W';
732                 }
733         }
734         return ret;
735 }
736
737 /** Update the highlighted to/from squares on the board.
738  * Based on the global "highlight_from" and "highlight_to" variables.
739  */
740 var update_board_highlight = function() {
741         $("#board").find('.square-55d63').removeClass('nonuglyhighlight');
742         if ((current_display_line === null || current_display_line_is_history) &&
743             highlight_from !== undefined && highlight_to !== undefined) {
744                 $("#board").find('.square-' + highlight_from).addClass('nonuglyhighlight');
745                 $("#board").find('.square-' + highlight_to).addClass('nonuglyhighlight');
746         }
747 }
748
749 var update_history = function() {
750         if (display_lines[0] === null || display_lines[0].pv.length == 0) {
751                 $("#history").html("No history");
752         } else if (truncate_display_history) {
753                 $("#history").html(print_pv(0, 8, true));
754         } else {
755                 $("#history").html(
756                         '(<a class="move" href="javascript:collapse_history(true)">collapse</a>) ' +
757                         print_pv(0));
758         }
759 }
760
761 /**
762  * @param {!boolean} truncate_history
763  */
764 var collapse_history = function(truncate_history) {
765         truncate_display_history = truncate_history;
766         update_history();
767 }
768 window['collapse_history'] = collapse_history;
769
770 /** Update the HTML display of multi-PV from the global "refutation_lines".
771  *
772  * Also recreates the global "display_lines".
773  */
774 var update_refutation_lines = function() {
775         if (base_fen === null) {
776                 return;
777         }
778         if (display_lines.length > 2) {
779                 // Truncate so that only the history and PV is left.
780                 display_lines = [ display_lines[0], display_lines[1] ];
781         }
782         var tbl = $("#refutationlines");
783         tbl.empty();
784
785         // Find out where the lines start from.
786         var base_line = [];
787         var base_scores = display_lines[1].scores;
788         var start_display_move_num = 0;
789         if (hash_refutation_lines) {
790                 base_line = current_display_line.pv.slice(0, current_display_move + 1);
791                 base_scores = current_display_line.scores;
792                 start_display_move_num = base_line.length;
793         }
794
795         var moves = [];
796         for (var move in refutation_lines) {
797                 moves.push(move);
798         }
799
800         var invert = (toplay === 'B');
801         if (current_display_line && current_display_move % 2 == 0) {
802                 invert = !invert;
803         }
804         var compare = sort_refutation_lines_by_score ? compare_by_score : compare_by_name;
805         moves = moves.sort(function(a, b) { return compare(refutation_lines, invert, a, b) });
806         for (var i = 0; i < moves.length; ++i) {
807                 var line = refutation_lines[moves[i]];
808
809                 var tr = document.createElement("tr");
810
811                 var move_td = document.createElement("td");
812                 tr.appendChild(move_td);
813                 $(move_td).addClass("move");
814
815                 var scores = base_scores.concat([{ first_move: start_display_move_num, score: line['score'] }]);
816
817                 if (line['pv'].length == 0) {
818                         // Not found, so just make a one-move PV.
819                         var move = "<a class=\"move\" href=\"javascript:show_line(" + display_lines.length + ", " + 0 + ");\">" + line['move'] + "</a>";
820                         $(move_td).html(move);
821                         var score_td = document.createElement("td");
822
823                         $(score_td).addClass("score");
824                         $(score_td).text("—");
825                         tr.appendChild(score_td);
826
827                         var depth_td = document.createElement("td");
828                         tr.appendChild(depth_td);
829                         $(depth_td).addClass("depth");
830                         $(depth_td).text("—");
831
832                         var pv_td = document.createElement("td");
833                         tr.appendChild(pv_td);
834                         $(pv_td).addClass("pv");
835                         $(pv_td).html(add_pv(base_fen, base_line.concat([ line['move'] ]), move_num, toplay, scores, start_display_move_num));
836
837                         tbl.append(tr);
838                         continue;
839                 }
840
841                 var move = "<a class=\"move\" href=\"javascript:show_line(" + display_lines.length + ", " + 0 + ");\">" + line['move'] + "</a>";
842                 $(move_td).html(move);
843
844                 var score_td = document.createElement("td");
845                 tr.appendChild(score_td);
846                 $(score_td).addClass("score");
847                 $(score_td).text(format_short_score(line['score']));
848
849                 var depth_td = document.createElement("td");
850                 tr.appendChild(depth_td);
851                 $(depth_td).addClass("depth");
852                 if (line['depth'] && line['depth'] >= 0) {
853                         $(depth_td).text("d" + line['depth']);
854                 } else {
855                         $(depth_td).text("—");
856                 }
857
858                 var pv_td = document.createElement("td");
859                 tr.appendChild(pv_td);
860                 $(pv_td).addClass("pv");
861                 $(pv_td).html(add_pv(base_fen, base_line.concat(line['pv']), move_num, toplay, scores, start_display_move_num, 10));
862
863                 tbl.append(tr);
864         }
865
866         // Make one of the links clickable and the other nonclickable.
867         if (sort_refutation_lines_by_score) {
868                 $("#sortbyscore0").html("<a href=\"javascript:resort_refutation_lines(false)\">Move</a>");
869                 $("#sortbyscore1").html("<strong>Score</strong>");
870         } else {
871                 $("#sortbyscore0").html("<strong>Move</strong>");
872                 $("#sortbyscore1").html("<a href=\"javascript:resort_refutation_lines(true)\">Score</a>");
873         }
874
875         // Update the move highlight, as we've rewritten all the HTML.
876         update_move_highlight();
877 }
878
879 /**
880  * Create a Chess.js board object, containing the given position plus the given moves,
881  * up to the given limit.
882  *
883  * @param {?string} fen
884  * @param {Array.<string>} moves
885  * @param {number} last_move
886  */
887 var chess_from = function(fen, moves, last_move) {
888         var hiddenboard = new Chess();
889         if (fen !== null) {
890                 hiddenboard.load(fen);
891         }
892         for (var i = 0; i <= last_move; ++i) {
893                 if (moves[i] === '0-0') {
894                         hiddenboard.move('O-O');
895                 } else if (moves[i] === '0-0-0') {
896                         hiddenboard.move('O-O-O');
897                 } else {
898                         hiddenboard.move(moves[i]);
899                 }
900         }
901         return hiddenboard;
902 }
903
904 var update_game_list = function(games) {
905         $("#games").text("");
906         if (games === null) {
907                 return;
908         }
909
910         var games_div = document.getElementById('games');
911         for (var game_num = 0; game_num < games.length; ++game_num) {
912                 var game = games[game_num];
913                 var game_span = document.createElement("span");
914                 game_span.setAttribute("class", "game");
915
916                 var game_name = document.createTextNode(game['name']);
917                 if (game['url'] === backend_url) {
918                         // This game.
919                         game_span.appendChild(game_name);
920
921                         if (current_analysis_data && current_analysis_data['position']) {
922                                 var score;
923                                 if (current_analysis_data['position']['result']) {
924                                         score = " (" + current_analysis_data['position']['result'] + ")";
925                                 } else {
926                                         score = " (" + format_short_score(current_analysis_data['score']) + ")";
927                                 }
928                                 game_span.appendChild(document.createTextNode(score));
929                         }
930                 } else {
931                         // Some other game.
932                         var game_a = document.createElement("a");
933                         game_a.setAttribute("href", "#" + game['id']);
934                         game_a.appendChild(game_name);
935                         game_span.appendChild(game_a);
936
937                         var score;
938                         if (game['result']) {
939                                 score = " (" + game['result'] + ")";
940                         } else {
941                                 score = " (" + format_short_score(game['score']) + ")";
942                         }
943                         game_span.appendChild(document.createTextNode(score));
944                 }
945
946                 games_div.appendChild(game_span);
947         }
948 }
949
950 /**
951  * Try to find a running game that matches with the current hash,
952  * and switch to it if we're not already displaying it.
953  */
954 var possibly_switch_game_from_hash = function() {
955         if (current_games === null) {
956                 return;
957         }
958
959         var hash = window.location.hash.replace(/^#/,'');
960         for (var i = 0; i < current_games.length; ++i) {
961                 if (current_games[i]['id'] === hash) {
962                         if (backend_url !== current_games[i]['url']) {
963                                 switch_backend(current_games[i]);
964                         }
965                         return;
966                 }
967         }
968 }
969
970 /** Update all the HTML on the page, based on current global state.
971  */
972 var update_board = function() {
973         var data = displayed_analysis_data || current_analysis_data;
974         var current_data = current_analysis_data;  // Convenience alias.
975
976         display_lines = [];
977
978         // Print the history. This is pretty much the only thing that's
979         // unconditionally taken from current_data (we're not interested in
980         // historic history).
981         if (current_data['position']['history']) {
982                 add_pv('start', current_data['position']['history'], 1, 'W', null, 0, 8, true);
983         } else {
984                 display_lines.push(null);
985         }
986         update_history();
987
988         // Games currently in progress, if any.
989         if (current_data['games']) {
990                 current_games = current_data['games'];
991                 possibly_switch_game_from_hash();
992         } else {
993                 current_games = null;
994         }
995         update_game_list(current_games);
996
997         // The headline. Names are always fetched from current_data;
998         // the rest can depend a bit.
999         var headline;
1000         if (current_data &&
1001             current_data['position']['player_w'] && current_data['position']['player_b']) {
1002                 headline = current_data['position']['player_w'] + '–' +
1003                         current_data['position']['player_b'] + ', analysis';
1004         } else {
1005                 headline = 'Analysis';
1006         }
1007
1008         // Credits, where applicable. Note that we don't want the footer to change a lot
1009         // when e.g. viewing history, so if any of these changed during the game,
1010         // use the current one still.
1011         if (current_data['using_lomonosov']) {
1012                 $("#lomonosov").show();
1013         } else {
1014                 $("#lomonosov").hide();
1015         }
1016
1017         // Credits: The engine name/version.
1018         if (current_data['engine'] && current_data['engine']['name'] !== null) {
1019                 $("#engineid").text(current_data['engine']['name']);
1020         }
1021
1022         // Credits: The engine URL.
1023         if (current_data['engine'] && current_data['engine']['url']) {
1024                 $("#engineid").attr("href", current_data['engine']['url']);
1025         } else {
1026                 $("#engineid").removeAttr("href");
1027         }
1028
1029         // Credits: Engine details.
1030         if (current_data['engine'] && current_data['engine']['details']) {
1031                 $("#enginedetails").text(" (" + current_data['engine']['details'] + ")");
1032         } else {
1033                 $("#enginedetails").text("");
1034         }
1035
1036         // Credits: Move source, possibly with URL.
1037         if (current_data['move_source'] && current_data['move_source_url']) {
1038                 $("#movesource").text("Moves provided by ");
1039                 var movesource_a = document.createElement("a");
1040                 movesource_a.setAttribute("href", current_data['move_source_url']);
1041                 var movesource_text = document.createTextNode(current_data['move_source']);
1042                 movesource_a.appendChild(movesource_text);
1043                 var movesource_period = document.createTextNode(".");
1044                 document.getElementById("movesource").appendChild(movesource_a);
1045                 document.getElementById("movesource").appendChild(movesource_period);
1046         } else if (current_data['move_source']) {
1047                 $("#movesource").text("Moves provided by " + current_data['move_source'] + ".");
1048         } else {
1049                 $("#movesource").text("");
1050         }
1051
1052         var last_move;
1053         if (displayed_analysis_data) {
1054                 // Displaying some non-current position, pick out the last move
1055                 // from the history. This will work even if the fetch failed.
1056                 last_move = format_halfmove_with_number(
1057                         current_display_line.pv[current_display_move],
1058                         current_display_move + 1);
1059                 headline += ' after ' + last_move;
1060         } else if (data['position']['last_move'] !== 'none') {
1061                 last_move = format_move_with_number(
1062                         data['position']['last_move'],
1063                         data['position']['move_num'],
1064                         data['position']['toplay'] == 'W');
1065                 headline += ' after ' + last_move;
1066         } else {
1067                 last_move = null;
1068         }
1069         $("#headline").text(headline);
1070
1071         // The <title> contains a very brief headline.
1072         var title_elems = [];
1073         if (data['position'] && data['position']['result']) {
1074                 title_elems.push(data['position']['result']);
1075         } else if (data['score']) {
1076                 title_elems.push(format_short_score(data['score']));
1077         }
1078         if (last_move !== null) {
1079                 title_elems.push(last_move);
1080         }
1081
1082         if (title_elems.length != 0) {
1083                 document.title = '(' + title_elems.join(', ') + ') analysis.sesse.net';
1084         } else {
1085                 document.title = 'analysis.sesse.net';
1086         }
1087
1088         // The last move (shown by highlighting the from and to squares).
1089         if (data['position'] && data['position']['last_move_uci']) {
1090                 highlight_from = data['position']['last_move_uci'].substr(0, 2);
1091                 highlight_to = data['position']['last_move_uci'].substr(2, 2);
1092         } else if (current_display_line_is_history && current_display_line && current_display_move >= 0) {
1093                 // We don't have historic analysis for this position, but we
1094                 // can reconstruct what the last move was by just replaying
1095                 // from the start.
1096                 var hiddenboard = chess_from(null, current_display_line.pv, current_display_move);
1097                 var moves = hiddenboard.history({ verbose: true });
1098                 last_move = moves.pop();
1099                 highlight_from = last_move.from;
1100                 highlight_to = last_move.to;
1101         } else {
1102                 highlight_from = highlight_to = undefined;
1103         }
1104         update_board_highlight();
1105
1106         if (data['failed']) {
1107                 $("#score").text("No analysis for this move");
1108                 $("#pvtitle").text("PV:");
1109                 $("#pv").empty();
1110                 $("#searchstats").html("&nbsp;");
1111                 $("#refutationlines").empty();
1112                 $("#whiteclock").empty();
1113                 $("#blackclock").empty();
1114                 refutation_lines = [];
1115                 update_refutation_lines();
1116                 clear_arrows();
1117                 update_displayed_line();
1118                 update_move_highlight();
1119                 return;
1120         }
1121
1122         update_clock();
1123
1124         // The score.
1125         if (current_display_line && !current_display_line_is_history) {
1126                 var score;
1127                 if (current_display_line.scores && current_display_line.scores.length > 0) {
1128                         for (var i = 0; i < current_display_line.scores.length; ++i) {
1129                                 if (current_display_move < current_display_line.scores[i].first_move) {
1130                                         break;
1131                                 }
1132                                 score = current_display_line.scores[i].score;
1133                         }
1134                 }
1135                 if (score) {
1136                         $("#score").text(format_long_score(score));
1137                 } else {
1138                         $("#score").text("No score for this line");
1139                 }
1140         } else if (data['score']) {
1141                 $("#score").text(format_long_score(data['score']));
1142         }
1143
1144         // The search stats.
1145         if (data['searchstats']) {
1146                 $("#searchstats").html(data['searchstats']);
1147         } else if (data['tablebase'] == 1) {
1148                 $("#searchstats").text("Tablebase result");
1149         } else if (data['nodes'] && data['nps'] && data['depth']) {
1150                 var stats = thousands(data['nodes']) + ' nodes, ' + thousands(data['nps']) + ' nodes/sec, depth ' + data['depth'] + ' ply';
1151                 if (data['seldepth']) {
1152                         stats += ' (' + data['seldepth'] + ' selective)';
1153                 }
1154                 if (data['tbhits'] && data['tbhits'] > 0) {
1155                         if (data['tbhits'] == 1) {
1156                                 stats += ', one Syzygy hit';
1157                         } else {
1158                                 stats += ', ' + thousands(data['tbhits']) + ' Syzygy hits';
1159                         }
1160                 }
1161
1162                 $("#searchstats").text(stats);
1163         } else {
1164                 $("#searchstats").text("");
1165         }
1166
1167         // Update the board itself.
1168         base_fen = data['position']['fen'];
1169         update_displayed_line();
1170
1171         // Print the PV.
1172         $("#pvtitle").text("PV:");
1173
1174         var scores = [{ first_move: -1, score: data['score'] }];
1175         $("#pv").html(add_pv(data['position']['fen'], data['pv'], data['position']['move_num'], data['position']['toplay'], scores, 0));
1176
1177         // Update the PV arrow.
1178         clear_arrows();
1179         if (data['pv'].length >= 1) {
1180                 var hiddenboard = new Chess(base_fen);
1181
1182                 // draw a continuation arrow as long as it's the same piece
1183                 var last_to;
1184                 for (var i = 0; i < data['pv'].length; i += 2) {
1185                         var move = hiddenboard.move(data['pv'][i]);
1186                         if ((i >= 2 && move.from != last_to) ||
1187                              interfering_arrow(move.from, move.to)) {
1188                                 break;
1189                         }
1190                         create_arrow(move.from, move.to, '#f66', 6, 20);
1191                         last_to = move.from;
1192                         hiddenboard.move(data['pv'][i + 1]);  // To keep continuity.
1193                 }
1194
1195                 var alt_moves = find_nonstupid_moves(data, 30, data['position']['toplay'] === 'B');
1196                 for (var i = 1; i < alt_moves.length && i < 3; ++i) {
1197                         hiddenboard = new Chess(base_fen);
1198                         var move = hiddenboard.move(alt_moves[i]);
1199                         create_arrow(move.from, move.to, '#f66', 1, 10);
1200                 }
1201         }
1202
1203         // See if all semi-reasonable moves have only one possible response.
1204         if (data['pv'].length >= 2) {
1205                 var nonstupid_moves = find_nonstupid_moves(data, 300, data['position']['toplay'] === 'B');
1206                 var response;
1207                 {
1208                         var hiddenboard = new Chess(base_fen);
1209                         hiddenboard.move(data['pv'][0]);
1210                         response = hiddenboard.move(data['pv'][1]);
1211                 }
1212                 for (var i = 0; i < nonstupid_moves.length; ++i) {
1213                         if (nonstupid_moves[i] == data['pv'][0]) {
1214                                 // ignore the PV move for refutation lines.
1215                                 continue;
1216                         }
1217                         if (!data['refutation_lines'] ||
1218                             !data['refutation_lines'][nonstupid_moves[i]] ||
1219                             !data['refutation_lines'][nonstupid_moves[i]]['pv'] ||
1220                             data['refutation_lines'][nonstupid_moves[i]]['pv'].length < 1) {
1221                                 // Incomplete PV, abort.
1222                                 response = undefined;
1223                                 break;
1224                         }
1225                         var line = data['refutation_lines'][nonstupid_moves[i]];
1226                         hiddenboard = new Chess(base_fen);
1227                         hiddenboard.move(line['pv'][0]);
1228                         var this_response = hiddenboard.move(line['pv'][1]);
1229                         if (response.from !== this_response.from || response.to !== this_response.to) {
1230                                 // Different response depending on lines, abort.
1231                                 response = undefined;
1232                                 break;
1233                         }
1234                 }
1235
1236                 if (nonstupid_moves.length > 0 && response !== undefined) {
1237                         create_arrow(response.from, response.to, '#66f', 6, 20);
1238                 }
1239         }
1240
1241         // Update the refutation lines.
1242         base_fen = data['position']['fen'];
1243         move_num = parseInt(data['position']['move_num']);
1244         toplay = data['position']['toplay'];
1245         refutation_lines = hash_refutation_lines || data['refutation_lines'];
1246         update_refutation_lines();
1247
1248         // Update the sparkline last, since its size depends on how everything else reflowed.
1249         update_sparkline(data);
1250 }
1251
1252 var update_sparkline = function(data) {
1253         if (data && data['score_history']) {
1254                 var first_move_num = undefined;
1255                 for (var halfmove_num in data['score_history']) {
1256                         halfmove_num = parseInt(halfmove_num);
1257                         if (first_move_num === undefined || halfmove_num < first_move_num) {
1258                                 first_move_num = halfmove_num;
1259                         }
1260                 }
1261                 if (first_move_num !== undefined) {
1262                         var last_move_num = data['position']['move_num'] * 2 - 3;
1263                         if (data['position']['toplay'] === 'B') {
1264                                 ++last_move_num;
1265                         }
1266
1267                         // Possibly truncate some moves if we don't have enough width.
1268                         // FIXME: Sometimes width() for #scorecontainer (and by extent,
1269                         // #scoresparkcontainer) on Chrome for mobile seems to start off
1270                         // at something very small, and then suddenly snap back into place.
1271                         // Figure out why.
1272                         var max_moves = Math.floor($("#scoresparkcontainer").width() / 5) - 5;
1273                         if (last_move_num - first_move_num > max_moves) {
1274                                 first_move_num = last_move_num - max_moves;
1275                         }
1276
1277                         var min_score = -100;
1278                         var max_score = 100;
1279                         var last_score = null;
1280                         var scores = [];
1281                         for (var halfmove_num = first_move_num; halfmove_num <= last_move_num; ++halfmove_num) {
1282                                 if (data['score_history'][halfmove_num]) {
1283                                         var score = compute_plot_score(data['score_history'][halfmove_num]);
1284                                         last_score = score;
1285                                         if (score < min_score) min_score = score;
1286                                         if (score > max_score) max_score = score;
1287                                 }
1288                                 scores.push(last_score);
1289                         }
1290                         if (data['score']) {
1291                                 scores.push(compute_plot_score(data['score']));
1292                         }
1293                         // FIXME: at some widths, calling sparkline() seems to push
1294                         // #scorecontainer under the board.
1295                         $("#scorespark").sparkline(scores, {
1296                                 type: 'bar',
1297                                 zeroColor: 'gray',
1298                                 chartRangeMin: min_score,
1299                                 chartRangeMax: max_score,
1300                                 tooltipFormatter: function(sparkline, options, fields) {
1301                                         return format_tooltip(data, fields[0].offset + first_move_num);
1302                                 }
1303                         });
1304                 } else {
1305                         $("#scorespark").text("");
1306                 }
1307         } else {
1308                 $("#scorespark").text("");
1309         }
1310 }
1311
1312 /**
1313  * @param {number} num_viewers
1314  */
1315 var update_num_viewers = function(num_viewers) {
1316         if (num_viewers === null) {
1317                 $("#numviewers").text("");
1318         } else if (num_viewers == 1) {
1319                 $("#numviewers").text("You are the only current viewer");
1320         } else {
1321                 $("#numviewers").text(num_viewers + " current viewers");
1322         }
1323 }
1324
1325 var update_clock = function() {
1326         clearTimeout(clock_timer);
1327
1328         var data = displayed_analysis_data || current_analysis_data;
1329         if (!data) return;
1330
1331         if (data['position']) {
1332                 var result = data['position']['result'];
1333                 if (result === '1-0') {
1334                         $("#whiteclock").text("1");
1335                         $("#blackclock").text("0");
1336                         $("#whiteclock").removeClass("running-clock");
1337                         $("#blackclock").removeClass("running-clock");
1338                         return;
1339                 }
1340                 if (result === '1/2-1/2') {
1341                         $("#whiteclock").text("1/2");
1342                         $("#blackclock").text("1/2");
1343                         $("#whiteclock").removeClass("running-clock");
1344                         $("#blackclock").removeClass("running-clock");
1345                         return;
1346                 }       
1347                 if (result === '0-1') {
1348                         $("#whiteclock").text("0");
1349                         $("#blackclock").text("1");
1350                         $("#whiteclock").removeClass("running-clock");
1351                         $("#blackclock").removeClass("running-clock");
1352                         return;
1353                 }
1354         }
1355
1356         var white_clock_ms = null;
1357         var black_clock_ms = null;
1358
1359         // Static clocks.
1360         if (data['position'] &&
1361             data['position']['white_clock'] &&
1362             data['position']['black_clock']) {
1363                 white_clock_ms = data['position']['white_clock'] * 1000;
1364                 black_clock_ms = data['position']['black_clock'] * 1000;
1365         }
1366
1367         // Dynamic clock (only one, obviously).
1368         var color;
1369         if (data['position']['white_clock_target']) {
1370                 color = "white";
1371                 $("#whiteclock").addClass("running-clock");
1372                 $("#blackclock").removeClass("running-clock");
1373         } else if (data['position']['black_clock_target']) {
1374                 color = "black";
1375                 $("#whiteclock").removeClass("running-clock");
1376                 $("#blackclock").addClass("running-clock");
1377         } else {
1378                 $("#whiteclock").removeClass("running-clock");
1379                 $("#blackclock").removeClass("running-clock");
1380         }
1381         var remaining_ms;
1382         if (color) {
1383                 var now = new Date().getTime() + client_clock_offset_ms;
1384                 remaining_ms = data['position'][color + '_clock_target'] * 1000 - now;
1385                 if (color === "white") {
1386                         white_clock_ms = remaining_ms;
1387                 } else {
1388                         black_clock_ms = remaining_ms;
1389                 }
1390         }
1391
1392         if (white_clock_ms === null || black_clock_ms === null) {
1393                 $("#whiteclock").empty();
1394                 $("#blackclock").empty();
1395                 return;
1396         }
1397
1398         // If either player has ten minutes or less left, add the second counters.
1399         var show_seconds = (white_clock_ms < 60 * 10 * 1000 || black_clock_ms < 60 * 10 * 1000);
1400
1401         if (color) {
1402                 // See when the clock will change next, and update right after that.
1403                 var next_update_ms;
1404                 if (show_seconds) {
1405                         next_update_ms = remaining_ms % 1000 + 100;
1406                 } else {
1407                         next_update_ms = remaining_ms % 60000 + 100;
1408                 }
1409                 clock_timer = setTimeout(update_clock, next_update_ms);
1410         }
1411
1412         $("#whiteclock").text(format_clock(white_clock_ms, show_seconds));
1413         $("#blackclock").text(format_clock(black_clock_ms, show_seconds));
1414 }
1415
1416 /**
1417  * @param {Number} remaining_ms
1418  * @param {boolean} show_seconds
1419  */
1420 var format_clock = function(remaining_ms, show_seconds) {
1421         if (remaining_ms <= 0) {
1422                 if (show_seconds) {
1423                         return "00:00:00";
1424                 } else {
1425                         return "00:00";
1426                 }
1427         }
1428
1429         var remaining = Math.floor(remaining_ms / 1000);
1430         var seconds = remaining % 60;
1431         remaining = (remaining - seconds) / 60;
1432         var minutes = remaining % 60;
1433         remaining = (remaining - minutes) / 60;
1434         var hours = remaining;
1435         if (show_seconds) {
1436                 return format_2d(hours) + ":" + format_2d(minutes) + ":" + format_2d(seconds);
1437         } else {
1438                 return format_2d(hours) + ":" + format_2d(minutes);
1439         }
1440 }
1441
1442 /**
1443  * @param {Number} x
1444  */
1445 var format_2d = function(x) {
1446         if (x >= 10) {
1447                 return x;
1448         } else {
1449                 return "0" + x;
1450         }
1451 }
1452
1453 /**
1454  * @param {string} move
1455  * @param {Number} move_num
1456  * @param {boolean} white_to_play
1457  */
1458 var format_move_with_number = function(move, move_num, white_to_play) {
1459         var ret;
1460         if (white_to_play) {
1461                 ret = (move_num - 1) + '… ';
1462         } else {
1463                 ret = move_num + '. ';
1464         }
1465         ret += move;
1466         return ret;
1467 }
1468
1469 /**
1470  * @param {string} move
1471  * @param {Number} halfmove_num
1472  */
1473 var format_halfmove_with_number = function(move, halfmove_num) {
1474         return format_move_with_number(
1475                 move,
1476                 Math.floor(halfmove_num / 2) + 1,
1477                 halfmove_num % 2 == 0);
1478 }
1479
1480 /**
1481  * @param {Object} data
1482  * @param {Number} halfmove_num
1483  */
1484 var format_tooltip = function(data, halfmove_num) {
1485         if (data['score_history'][halfmove_num] ||
1486             halfmove_num === data['position']['history'].length) {
1487                 var move;
1488                 var short_score;
1489                 if (halfmove_num === data['position']['history'].length) {
1490                         move = data['position']['last_move'];
1491                         short_score = format_short_score(data['score']);
1492                 } else {
1493                         move = data['position']['history'][halfmove_num];
1494                         short_score = format_short_score(data['score_history'][halfmove_num]);
1495                 }
1496                 var move_with_number = format_halfmove_with_number(move, halfmove_num);
1497
1498                 return "After " + move_with_number + ": " + short_score;
1499         } else {
1500                 for (var i = halfmove_num; i --> 0; ) {
1501                         if (data['score_history'][i]) {
1502                                 var move = data['position']['history'][i];
1503                                 return "[Analysis kept from " + format_halfmove_with_number(move, i) + "]";
1504                         }
1505                 }
1506         }
1507 }
1508
1509 /**
1510  * @param {boolean} sort_by_score
1511  */
1512 var resort_refutation_lines = function(sort_by_score) {
1513         sort_refutation_lines_by_score = sort_by_score;
1514         if (supports_html5_storage()) {
1515                 localStorage['sort_refutation_lines_by_score'] = sort_by_score ? 1 : 0;
1516         }
1517         update_refutation_lines();
1518 }
1519 window['resort_refutation_lines'] = resort_refutation_lines;
1520
1521 /**
1522  * @param {boolean} truncate_history
1523  */
1524 var set_truncate_history = function(truncate_history) {
1525         truncate_display_history = truncate_history;
1526         update_refutation_lines();
1527 }
1528 window['set_truncate_history'] = set_truncate_history;
1529
1530 /**
1531  * @param {number} line_num
1532  * @param {number} move_num
1533  */
1534 var show_line = function(line_num, move_num) {
1535         if (line_num == -1) {
1536                 current_display_line = null;
1537                 current_display_move = null;
1538                 hash_refutation_lines = null;
1539                 if (displayed_analysis_data) {
1540                         // TODO: Support exiting to history position if we are in an
1541                         // analysis line of a history position.
1542                         displayed_analysis_data = null;
1543                 }
1544                 update_board();
1545                 return;
1546         } else {
1547                 current_display_line = jQuery.extend({}, display_lines[line_num]);  // Shallow clone.
1548                 current_display_move = move_num + current_display_line.start_display_move_num;
1549         }
1550         current_display_line_is_history = (line_num == 0);
1551
1552         update_historic_analysis();
1553         update_displayed_line();
1554         update_board_highlight();
1555         update_move_highlight();
1556         redraw_arrows();
1557 }
1558 window['show_line'] = show_line;
1559
1560 var prev_move = function() {
1561         if (current_display_line &&
1562             current_display_move >= current_display_line.start_display_move_num) {
1563                 --current_display_move;
1564         }
1565         update_historic_analysis();
1566         update_displayed_line();
1567         update_move_highlight();
1568 }
1569 window['prev_move'] = prev_move;
1570
1571 var next_move = function() {
1572         if (current_display_line &&
1573             current_display_move < current_display_line.pv.length - 1) {
1574                 ++current_display_move;
1575         }
1576         update_historic_analysis();
1577         update_displayed_line();
1578         update_move_highlight();
1579 }
1580 window['next_move'] = next_move;
1581
1582 var next_game = function() {
1583         if (current_games === null) {
1584                 return;
1585         }
1586
1587         // Try to find the game we are currently looking at.
1588         for (var game_num = 0; game_num < current_games.length; ++game_num) {
1589                 var game = current_games[game_num];
1590                 if (game['url'] === backend_url) {
1591                         var next_game_num = (game_num + 1) % current_games.length;
1592                         switch_backend(current_games[next_game_num]);
1593                         return;
1594                 }
1595         }
1596
1597         // Couldn't find it; give up.
1598 }
1599
1600 var update_historic_analysis = function() {
1601         if (!current_display_line_is_history) {
1602                 return;
1603         }
1604         if (current_display_move == current_display_line.pv.length - 1) {
1605                 displayed_analysis_data = null;
1606                 update_board();
1607         }
1608
1609         // Fetch old analysis for this line if it exists.
1610         var hiddenboard = chess_from(null, current_display_line.pv, current_display_move);
1611         var filename = "/history/move" + (current_display_move + 1) + "-" +
1612                 hiddenboard.fen().replace(/ /g, '_').replace(/\//g, '-') + ".json";
1613
1614         current_historic_xhr = $.ajax({
1615                 url: filename
1616         }).done(function(data, textstatus, xhr) {
1617                 displayed_analysis_data = data;
1618                 update_board();
1619         }).fail(function(jqXHR, textStatus, errorThrown) {
1620                 if (textStatus === "abort") {
1621                         // Aborted because we are switching backends. Don't do anything;
1622                         // we will already have been cleared.
1623                 } else {
1624                         displayed_analysis_data = {'failed': true};
1625                         update_board();
1626                 }
1627         });
1628 }
1629
1630 /**
1631  * @param {string} fen
1632  */
1633 var update_imbalance = function(fen) {
1634         var hiddenboard = new Chess(fen);
1635         var imbalance = {'k': 0, 'q': 0, 'r': 0, 'b': 0, 'n': 0, 'p': 0};
1636         for (var row = 0; row < 8; ++row) {
1637                 for (var col = 0; col < 8; ++col) {
1638                         var col_text = String.fromCharCode('a1'.charCodeAt(0) + col);
1639                         var row_text = String.fromCharCode('a1'.charCodeAt(1) + row);
1640                         var square = col_text + row_text;
1641                         var contents = hiddenboard.get(square);
1642                         if (contents !== null) {
1643                                 if (contents.color === 'w') {
1644                                         ++imbalance[contents.type];
1645                                 } else {
1646                                         --imbalance[contents.type];
1647                                 }
1648                         }
1649                 }
1650         }
1651         var white_imbalance = '';
1652         var black_imbalance = '';
1653         for (var piece in imbalance) {
1654                 for (var i = 0; i < imbalance[piece]; ++i) {
1655                         white_imbalance += '<img src="img/chesspieces/wikipedia/w' + piece.toUpperCase() + '.png" alt="" style="width: 15px;height: 15px;">';
1656                 }
1657                 for (var i = 0; i < -imbalance[piece]; ++i) {
1658                         black_imbalance += '<img src="img/chesspieces/wikipedia/b' + piece.toUpperCase() + '.png" alt="" style="width: 15px;height: 15px;">';
1659                 }
1660         }
1661         $('#whiteimbalance').html(white_imbalance);
1662         $('#blackimbalance').html(black_imbalance);
1663 }
1664
1665 /** Mark the currently selected move in red.
1666  * Also replaces the PV with the current displayed line if it's not shown
1667  * anywhere else on the screen.
1668  */
1669 var update_move_highlight = function() {
1670         if (highlighted_move !== null) {
1671                 highlighted_move.removeClass('highlight'); 
1672         }
1673         if (current_display_line) {
1674                 var display_line_num = find_display_line_matching_num();
1675                 if (display_line_num === null) {
1676                         // Replace the PV with the (complete) line.
1677                         $("#pvtitle").text("Exploring:");
1678                         current_display_line.start_display_move_num = 0;
1679                         display_lines.push(current_display_line);
1680                         $("#pv").html(print_pv(display_lines.length - 1));
1681                         display_line_num = display_lines.length - 1;
1682
1683                         // Clear out the PV, so it's not selected by anything later.
1684                         display_lines[1].pv = [];
1685                 }
1686
1687                 highlighted_move = $("#automove" + display_line_num + "-" + (current_display_move - current_display_line.start_display_move_num));
1688                 highlighted_move.addClass('highlight');
1689         }
1690 }
1691
1692 /**
1693  * See if the current displayed line is identical to any of the ones
1694  * we have on screen. (It might not be if e.g. the analysis reloaded
1695  * since we started looking.)
1696  *
1697  * @return {?number}
1698  */
1699 var find_display_line_matching_num = function() {
1700         for (var i = 0; i < display_lines.length; ++i) {
1701                 var line = display_lines[i];
1702                 if (line.start_display_move_num > 0) continue;
1703                 if (current_display_line.start_fen !== line.start_fen) continue;
1704                 if (current_display_line.pv.length !== line.pv.length) continue;
1705                 var ok = true;
1706                 for (var j = 0; j < line.pv.length; ++j) {
1707                         if (current_display_line.pv[j] !== line.pv[j]) {
1708                                 ok = false;
1709                                 break;
1710                         }
1711                 }
1712                 if (ok) {
1713                         return i;
1714                 }
1715         }
1716         return null;
1717 }
1718
1719 /** Update the board based on the currently displayed line.
1720  * 
1721  * TODO: This should really be called only whenever something changes,
1722  * instead of all the time.
1723  */
1724 var update_displayed_line = function() {
1725         if (current_display_line === null) {
1726                 $("#linenav").hide();
1727                 $("#linemsg").show();
1728                 display_fen = base_fen;
1729                 set_board_position(base_fen);
1730                 update_imbalance(base_fen);
1731                 return;
1732         }
1733
1734         $("#linenav").show();
1735         $("#linemsg").hide();
1736
1737         if (current_display_move <= 0) {
1738                 $("#prevmove").html("Previous");
1739         } else {
1740                 $("#prevmove").html("<a href=\"javascript:prev_move();\">Previous</a></span>");
1741         }
1742         if (current_display_move == current_display_line.pv.length - 1) {
1743                 $("#nextmove").html("Next");
1744         } else {
1745                 $("#nextmove").html("<a href=\"javascript:next_move();\">Next</a></span>");
1746         }
1747
1748         var hiddenboard = chess_from(current_display_line.start_fen, current_display_line.pv, current_display_move);
1749         set_board_position(hiddenboard.fen());
1750         if (display_fen !== hiddenboard.fen() && !current_display_line_is_history) {
1751                 // Fire off a hash request, since we're now off the main position
1752                 // and it just changed.
1753                 explore_hash(hiddenboard.fen());
1754         }
1755         display_fen = hiddenboard.fen();
1756         update_imbalance(hiddenboard.fen());
1757 }
1758
1759 var set_board_position = function(new_fen) {
1760         board_is_animating = true;
1761         var old_fen = board.fen();
1762         board.position(new_fen);
1763         if (board.fen() === old_fen) {
1764                 board_is_animating = false;
1765         }
1766 }
1767
1768 /**
1769  * @param {boolean} param_enable_sound
1770  */
1771 var set_sound = function(param_enable_sound) {
1772         enable_sound = param_enable_sound;
1773         if (enable_sound) {
1774                 $("#soundon").html("<strong>On</strong>");
1775                 $("#soundoff").html("<a href=\"javascript:set_sound(false)\">Off</a>");
1776
1777                 // Seemingly at least Firefox prefers MP3 over Opus; tell it otherwise,
1778                 // and also preload the file since the user has selected audio.
1779                 var ding = document.getElementById('ding');
1780                 if (ding && ding.canPlayType && ding.canPlayType('audio/ogg; codecs="opus"') === 'probably') {
1781                         ding.src = 'ding.opus';
1782                         ding.load();
1783                 }
1784         } else {
1785                 $("#soundon").html("<a href=\"javascript:set_sound(true)\">On</a>");
1786                 $("#soundoff").html("<strong>Off</strong>");
1787         }
1788         if (supports_html5_storage()) {
1789                 localStorage['enable_sound'] = enable_sound ? 1 : 0;
1790         }
1791 }
1792 window['set_sound'] = set_sound;
1793
1794 /** Send off a hash probe request to the backend.
1795  * @param {string} fen
1796  */
1797 var explore_hash = function(fen) {
1798         // If we already have a backend response going, abort it.
1799         if (current_hash_xhr) {
1800                 current_hash_xhr.abort();
1801         }
1802         if (current_hash_display_timer) {
1803                 clearTimeout(current_hash_display_timer);
1804                 current_hash_display_timer = null;
1805         }
1806         $("#refutationlines").empty();
1807         current_hash_xhr = $.ajax({
1808                 url: backend_hash_url + "?fen=" + fen
1809         }).done(function(data, textstatus, xhr) {
1810                 show_explore_hash_results(data, fen);
1811         });
1812 }
1813
1814 /** Process the JSON response from a hash probe request.
1815  * @param {!Object} data
1816  * @param {string} fen
1817  */
1818 var show_explore_hash_results = function(data, fen) {
1819         if (board_is_animating) {
1820                 // Updating while the animation is still going causes
1821                 // the animation to jerk. This is pretty crude, but it will do.
1822                 current_hash_display_timer = setTimeout(function() { show_explore_hash_results(data, fen); }, 100);
1823                 return;
1824         }
1825         current_hash_display_timer = null;
1826         hash_refutation_lines = data['lines'];
1827         update_board();
1828 }
1829
1830 // almost all of this stuff comes from the chessboard.js example page
1831 var onDragStart = function(source, piece, position, orientation) {
1832         var pseudogame = new Chess(display_fen);
1833         if (pseudogame.game_over() === true ||
1834             (pseudogame.turn() === 'w' && piece.search(/^b/) !== -1) ||
1835             (pseudogame.turn() === 'b' && piece.search(/^w/) !== -1)) {
1836                 return false;
1837         }
1838
1839         recommended_move = get_best_move(pseudogame, source, null, pseudogame.turn() === 'b');
1840         if (recommended_move) {
1841                 var squareEl = $('#board .square-' + recommended_move.to);
1842                 squareEl.addClass('highlight1-32417');
1843         }
1844         return true;
1845 }
1846
1847 var mousedownSquare = function(e) {
1848         reverse_dragging_from = null;
1849         var square = $(this).attr('data-square');
1850
1851         var pseudogame = new Chess(display_fen);
1852         if (pseudogame.game_over() === true) {
1853                 return;
1854         }
1855
1856         // If the square is empty, or has a piece of the side not to move,
1857         // we handle it. If not, normal piece dragging will take it.
1858         var position = board.position();
1859         if (!position.hasOwnProperty(square) ||
1860             (pseudogame.turn() === 'w' && position[square].search(/^b/) !== -1) ||
1861             (pseudogame.turn() === 'b' && position[square].search(/^w/) !== -1)) {
1862                 reverse_dragging_from = square;
1863                 recommended_move = get_best_move(pseudogame, null, square, pseudogame.turn() === 'b');
1864                 if (recommended_move) {
1865                         var squareEl = $('#board .square-' + recommended_move.from);
1866                         squareEl.addClass('highlight1-32417');
1867                         squareEl = $('#board .square-' + recommended_move.to);
1868                         squareEl.addClass('highlight1-32417');
1869                 }
1870         }
1871 }
1872
1873 var mouseupSquare = function(e) {
1874         if (reverse_dragging_from === null) {
1875                 return;
1876         }
1877         var source = $(this).attr('data-square');
1878         var target = reverse_dragging_from;
1879         reverse_dragging_from = null;
1880         if (onDrop(source, target) !== 'snapback') {
1881                 onSnapEnd(source, target);
1882         }
1883         $("#board").find('.square-55d63').removeClass('highlight1-32417');
1884 }
1885
1886 var get_best_move = function(game, source, target, invert) {
1887         var moves = game.moves({ verbose: true });
1888         if (source !== null) {
1889                 moves = moves.filter(function(move) { return move.from == source; });
1890         }
1891         if (target !== null) {
1892                 moves = moves.filter(function(move) { return move.to == target; });
1893         }
1894         if (moves.length == 0) {
1895                 return null;
1896         }
1897         if (moves.length == 1) {
1898                 return moves[0];
1899         }
1900
1901         // More than one move. Use the display lines (if we have them)
1902         // to disambiguate; otherwise, we have no information.
1903         var move_hash = {};
1904         for (var i = 0; i < moves.length; ++i) {
1905                 move_hash[moves[i].san] = moves[i];
1906         }
1907
1908         // See if we're already exploring some line.
1909         if (current_display_line &&
1910             current_display_move < current_display_line.pv.length - 1) {
1911                 var first_move = current_display_line.pv[current_display_move + 1];
1912                 if (move_hash[first_move]) {
1913                         return move_hash[first_move];
1914                 }
1915         }
1916
1917         // History and PV take priority over the display lines.
1918         for (var i = 0; i < 2; ++i) {
1919                 var line = display_lines[i];
1920                 var first_move = line.pv[line.start_display_move_num];
1921                 if (move_hash[first_move]) {
1922                         return move_hash[first_move];
1923                 }
1924         }
1925
1926         var best_move = null;
1927         var best_move_score = null;
1928
1929         for (var move in refutation_lines) {
1930                 var line = refutation_lines[move];
1931                 if (!line['score']) {
1932                         continue;
1933                 }
1934                 var first_move = line['pv'][0];
1935                 if (move_hash[first_move]) {
1936                         var score = compute_score_sort_key(line['score'], line['depth'], invert);
1937                         if (best_move_score === null || score > best_move_score) {
1938                                 best_move = move_hash[first_move];
1939                                 best_move_score = score;
1940                         }
1941                 }
1942         }
1943         return best_move;
1944 }
1945
1946 var onDrop = function(source, target) {
1947         if (source === target) {
1948                 if (recommended_move === null) {
1949                         return 'snapback';
1950                 } else {
1951                         // Accept the move. It will be changed in onSnapEnd.
1952                         return;
1953                 }
1954         } else {
1955                 // Suggestion not asked for.
1956                 recommended_move = null;
1957         }
1958
1959         // see if the move is legal
1960         var pseudogame = new Chess(display_fen);
1961         var move = pseudogame.move({
1962                 from: source,
1963                 to: target,
1964                 promotion: 'q' // NOTE: always promote to a queen for example simplicity
1965         });
1966
1967         // illegal move
1968         if (move === null) return 'snapback';
1969 }
1970
1971 var onSnapEnd = function(source, target) {
1972         if (source === target && recommended_move !== null) {
1973                 source = recommended_move.from;
1974                 target = recommended_move.to;
1975         }
1976         recommended_move = null;
1977         var pseudogame = new Chess(display_fen);
1978         var move = pseudogame.move({
1979                 from: source,
1980                 to: target,
1981                 promotion: 'q' // NOTE: always promote to a queen for example simplicity
1982         });
1983
1984         if (current_display_line &&
1985             current_display_move < current_display_line.pv.length - 1 &&
1986             current_display_line.pv[current_display_move + 1] === move.san) {
1987                 next_move();
1988                 return;
1989         }
1990
1991         // Walk down the displayed lines until we find one that starts with
1992         // this move, then select that. Note that this gives us a good priority
1993         // order (history first, then PV, then multi-PV lines).
1994         for (var i = 0; i < display_lines.length; ++i) {
1995                 if (i == 1 && current_display_line) {
1996                         // Do not choose PV if not on it.
1997                         continue;
1998                 }
1999                 var line = display_lines[i];
2000                 if (line.pv[line.start_display_move_num] === move.san) {
2001                         show_line(i, 0);
2002                         return;
2003                 }
2004         }
2005
2006         // Shouldn't really be here if we have hash probes, but there's really
2007         // nothing we can do.
2008 }
2009 // End of dragging-related code.
2010
2011 var fmt_cp = function(v) {
2012         if (v === 0) {
2013                 return "0.00";
2014         } else if (v > 0) {
2015                 return "+" + (v / 100).toFixed(2);
2016         } else {
2017                 v = -v;
2018                 return "-" + (v / 100).toFixed(2);
2019         }
2020 }
2021
2022 var format_short_score = function(score) {
2023         if (!score) {
2024                 return "???";
2025         }
2026         if (score[0] === 'm') {
2027                 if (score[2]) {  // Is a bound.
2028                         return score[2] + "\u00a0M " + score[1];
2029                 } else {
2030                         return "M " + score[1];
2031                 }
2032         } else if (score[0] === 'd') {
2033                 return "TB draw";
2034         } else if (score[0] === 'cp') {
2035                 if (score[2]) {  // Is a bound.
2036                         return score[2] + "\u00a0" + fmt_cp(score[1]);
2037                 } else {
2038                         return fmt_cp(score[1]);
2039                 }
2040         }
2041         return null;
2042 }
2043
2044 var format_long_score = function(score) {
2045         if (!score) {
2046                 return "???";
2047         }
2048         if (score[0] === 'm') {
2049                 if (score[1] > 0) {
2050                         return "White mates in " + score[1];
2051                 } else {
2052                         return "Black mates in " + (-score[1]);
2053                 }
2054         } else if (score[0] === 'd') {
2055                 return "Theoretical draw";
2056         } else if (score[0] === 'cp') {
2057                 return "Score: " + format_short_score(score);
2058         }
2059         return null;
2060 }
2061
2062 var compute_plot_score = function(score) {
2063         if (score[0] === 'm') {
2064                 if (score[1] > 0) {
2065                         return 500;
2066                 } else {
2067                         return -500;
2068                 }
2069         } else if (score[0] === 'd') {
2070                 return 0;
2071         } else if (score[0] === 'cp') {
2072                 if (score[1] > 500) {
2073                         return 500;
2074                 } else if (score[1] < -500) {
2075                         return -500;
2076                 } else {
2077                         return score[1];
2078                 }
2079         }
2080         return null;
2081 }
2082
2083 /**
2084  * @param score The score digest tuple.
2085  * @param {?number} depth Depth the move has been computed to, or null.
2086  * @param {boolean} invert Whether black is to play.
2087  * @param {boolean=} depth_secondary_key
2088  * @return {number}
2089  */
2090 var compute_score_sort_key = function(score, depth, invert, depth_secondary_key) {
2091         var s;
2092         if (!score) {
2093                 return -10000000;
2094         }
2095         if (score[0] === 'm') {
2096                 if (score[1] > 0) {
2097                         // White mates.
2098                         s = 99999 - score[1];
2099                 } else {
2100                         // Black mates (note the double negative for score[1]).
2101                         s = -99999 - score[1];
2102                 }
2103         } else if (score[0] === 'd') {
2104                 s = 0;
2105         } else if (score[0] === 'cp') {
2106                 s = score[1];
2107         }
2108         if (s) {
2109                 if (invert) s = -s;
2110                 if (depth_secondary_key) {
2111                         return s * 200 + (depth || 0);
2112                 } else {
2113                         return s;
2114                 }
2115         } else {
2116                 return null;
2117         }
2118 }
2119
2120 /**
2121  * @param {Object} game
2122  */
2123 var switch_backend = function(game) {
2124         // Stop looking at historic data.
2125         current_display_line = null;
2126         current_display_move = null;
2127         displayed_analysis_data = null;
2128         if (current_historic_xhr) {
2129                 current_historic_xhr.abort();
2130         }
2131
2132         // If we already have a backend response going, abort it.
2133         if (current_analysis_xhr) {
2134                 current_analysis_xhr.abort();
2135         }
2136         if (current_hash_xhr) {
2137                 current_hash_xhr.abort();
2138         }
2139
2140         // Otherwise, we should have a timer going to start a new one.
2141         // Kill that, too.
2142         if (current_analysis_request_timer) {
2143                 clearTimeout(current_analysis_request_timer);
2144                 current_analysis_request_timer = null;
2145         }
2146         if (current_hash_display_timer) {
2147                 clearTimeout(current_hash_display_timer);
2148                 current_hash_display_timer = null;
2149         }
2150
2151         // Request an immediate fetch with the new backend.
2152         backend_url = game['url'];
2153         backend_hash_url = game['hashurl'];
2154         window.location.hash = '#' + game['id'];
2155         current_analysis_data = null;
2156         ims = 0;
2157         request_update();
2158 }
2159 window['switch_backend'] = switch_backend;
2160
2161 var init = function() {
2162         unique = get_unique();
2163
2164         // Load settings from HTML5 local storage if available.
2165         if (supports_html5_storage() && localStorage['enable_sound']) {
2166                 set_sound(parseInt(localStorage['enable_sound']));
2167         } else {
2168                 set_sound(false);
2169         }
2170         if (supports_html5_storage() && localStorage['sort_refutation_lines_by_score']) {
2171                 sort_refutation_lines_by_score = parseInt(localStorage['sort_refutation_lines_by_score']);
2172         } else {
2173                 sort_refutation_lines_by_score = true;
2174         }
2175
2176         // Create board.
2177         board = new window.ChessBoard('board', {
2178                 onMoveEnd: function() { board_is_animating = false; },
2179
2180                 draggable: true,
2181                 onDragStart: onDragStart,
2182                 onDrop: onDrop,
2183                 onSnapEnd: onSnapEnd
2184         });
2185         $("#board").on('mousedown', '.square-55d63', mousedownSquare);
2186         $("#board").on('mouseup', '.square-55d63', mouseupSquare);
2187
2188         request_update();
2189         $(window).resize(function() {
2190                 board.resize();
2191                 update_sparkline(displayed_analysis_data || current_analysis_data);
2192                 update_board_highlight();
2193                 redraw_arrows();
2194         });
2195         $(window).keyup(function(event) {
2196                 if (event.which == 39) {  // Left arrow.
2197                         next_move();
2198                 } else if (event.which == 37) {  // Right arrow.
2199                         prev_move();
2200                 } else if (event.which >= 49 && event.which <= 57) {  // 1-9.
2201                         var num = event.which - 49;
2202                         if (current_games && current_games.length >= num) {
2203                                 switch_backend(current_games[num]);
2204                         }
2205                 } else if (event.which == 78) {  // N.
2206                         next_game();
2207                 }
2208         });
2209         window.addEventListener('hashchange', possibly_switch_game_from_hash, false);
2210 };
2211 $(document).ready(init);
2212
2213 })();