Fix another off-by-one bug that was introduced while fixing the others.
[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 = 2016091401;
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                         location.reload(true);
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                 if (current_display_move !== -1) {
1057                         last_move = format_halfmove_with_number(
1058                                 current_display_line.pv[current_display_move],
1059                                 current_display_move);
1060                         headline += ' after ' + last_move;
1061                 }
1062         } else if (data['position']['last_move'] !== 'none') {
1063                 // Find the previous move.
1064                 var previous_move_num, previous_toplay;
1065                 if (data['position']['toplay'] == 'B') {
1066                         previous_move_num = data['position']['move_num'];
1067                         previous_toplay = 'W';
1068                 } else {
1069                         previous_move_num = data['position']['move_num'] - 1;
1070                         previous_toplay = 'B';
1071                 }
1072
1073                 last_move = format_move_with_number(
1074                         data['position']['last_move'],
1075                         previous_move_num,
1076                         previous_toplay == 'W');
1077                 headline += ' after ' + last_move;
1078         } else {
1079                 last_move = null;
1080         }
1081         $("#headline").text(headline);
1082
1083         // The <title> contains a very brief headline.
1084         var title_elems = [];
1085         if (data['position'] && data['position']['result']) {
1086                 title_elems.push(data['position']['result']);
1087         } else if (data['score']) {
1088                 title_elems.push(format_short_score(data['score']));
1089         }
1090         if (last_move !== null) {
1091                 title_elems.push(last_move);
1092         }
1093
1094         if (title_elems.length != 0) {
1095                 document.title = '(' + title_elems.join(', ') + ') analysis.sesse.net';
1096         } else {
1097                 document.title = 'analysis.sesse.net';
1098         }
1099
1100         // The last move (shown by highlighting the from and to squares).
1101         if (data['position'] && data['position']['last_move_uci']) {
1102                 highlight_from = data['position']['last_move_uci'].substr(0, 2);
1103                 highlight_to = data['position']['last_move_uci'].substr(2, 2);
1104         } else if (current_display_line_is_history && current_display_line && current_display_move >= 0) {
1105                 // We don't have historic analysis for this position, but we
1106                 // can reconstruct what the last move was by just replaying
1107                 // from the start.
1108                 var hiddenboard = chess_from(null, current_display_line.pv, current_display_move);
1109                 var moves = hiddenboard.history({ verbose: true });
1110                 last_move = moves.pop();
1111                 highlight_from = last_move.from;
1112                 highlight_to = last_move.to;
1113         } else {
1114                 highlight_from = highlight_to = undefined;
1115         }
1116         update_board_highlight();
1117
1118         if (data['failed']) {
1119                 $("#score").text("No analysis for this move");
1120                 $("#pvtitle").text("PV:");
1121                 $("#pv").empty();
1122                 $("#searchstats").html("&nbsp;");
1123                 $("#refutationlines").empty();
1124                 $("#whiteclock").empty();
1125                 $("#blackclock").empty();
1126                 refutation_lines = [];
1127                 update_refutation_lines();
1128                 clear_arrows();
1129                 update_displayed_line();
1130                 update_move_highlight();
1131                 return;
1132         }
1133
1134         update_clock();
1135
1136         // The score.
1137         if (current_display_line && !current_display_line_is_history) {
1138                 var score;
1139                 if (current_display_line.scores && current_display_line.scores.length > 0) {
1140                         for (var i = 0; i < current_display_line.scores.length; ++i) {
1141                                 if (current_display_move < current_display_line.scores[i].first_move) {
1142                                         break;
1143                                 }
1144                                 score = current_display_line.scores[i].score;
1145                         }
1146                 }
1147                 if (score) {
1148                         $("#score").text(format_long_score(score));
1149                 } else {
1150                         $("#score").text("No score for this line");
1151                 }
1152         } else if (data['score']) {
1153                 $("#score").text(format_long_score(data['score']));
1154         }
1155
1156         // The search stats.
1157         if (data['searchstats']) {
1158                 $("#searchstats").html(data['searchstats']);
1159         } else if (data['tablebase'] == 1) {
1160                 $("#searchstats").text("Tablebase result");
1161         } else if (data['nodes'] && data['nps'] && data['depth']) {
1162                 var stats = thousands(data['nodes']) + ' nodes, ' + thousands(data['nps']) + ' nodes/sec, depth ' + data['depth'] + ' ply';
1163                 if (data['seldepth']) {
1164                         stats += ' (' + data['seldepth'] + ' selective)';
1165                 }
1166                 if (data['tbhits'] && data['tbhits'] > 0) {
1167                         if (data['tbhits'] == 1) {
1168                                 stats += ', one Syzygy hit';
1169                         } else {
1170                                 stats += ', ' + thousands(data['tbhits']) + ' Syzygy hits';
1171                         }
1172                 }
1173
1174                 $("#searchstats").text(stats);
1175         } else {
1176                 $("#searchstats").text("");
1177         }
1178
1179         // Update the board itself.
1180         base_fen = data['position']['fen'];
1181         update_displayed_line();
1182
1183         // Print the PV.
1184         $("#pvtitle").text("PV:");
1185
1186         var scores = [{ first_move: -1, score: data['score'] }];
1187         $("#pv").html(add_pv(data['position']['fen'], data['pv'], data['position']['move_num'], data['position']['toplay'], scores, 0));
1188
1189         // Update the PV arrow.
1190         clear_arrows();
1191         if (data['pv'].length >= 1) {
1192                 var hiddenboard = new Chess(base_fen);
1193
1194                 // draw a continuation arrow as long as it's the same piece
1195                 var last_to;
1196                 for (var i = 0; i < data['pv'].length; i += 2) {
1197                         var move = hiddenboard.move(data['pv'][i]);
1198                         if ((i >= 2 && move.from != last_to) ||
1199                              interfering_arrow(move.from, move.to)) {
1200                                 break;
1201                         }
1202                         create_arrow(move.from, move.to, '#f66', 6, 20);
1203                         last_to = move.from;
1204                         hiddenboard.move(data['pv'][i + 1]);  // To keep continuity.
1205                 }
1206
1207                 var alt_moves = find_nonstupid_moves(data, 30, data['position']['toplay'] === 'B');
1208                 for (var i = 1; i < alt_moves.length && i < 3; ++i) {
1209                         hiddenboard = new Chess(base_fen);
1210                         var move = hiddenboard.move(alt_moves[i]);
1211                         create_arrow(move.from, move.to, '#f66', 1, 10);
1212                 }
1213         }
1214
1215         // See if all semi-reasonable moves have only one possible response.
1216         if (data['pv'].length >= 2) {
1217                 var nonstupid_moves = find_nonstupid_moves(data, 300, data['position']['toplay'] === 'B');
1218                 var response;
1219                 {
1220                         var hiddenboard = new Chess(base_fen);
1221                         hiddenboard.move(data['pv'][0]);
1222                         response = hiddenboard.move(data['pv'][1]);
1223                 }
1224                 for (var i = 0; i < nonstupid_moves.length; ++i) {
1225                         if (nonstupid_moves[i] == data['pv'][0]) {
1226                                 // ignore the PV move for refutation lines.
1227                                 continue;
1228                         }
1229                         if (!data['refutation_lines'] ||
1230                             !data['refutation_lines'][nonstupid_moves[i]] ||
1231                             !data['refutation_lines'][nonstupid_moves[i]]['pv'] ||
1232                             data['refutation_lines'][nonstupid_moves[i]]['pv'].length < 1) {
1233                                 // Incomplete PV, abort.
1234                                 response = undefined;
1235                                 break;
1236                         }
1237                         var line = data['refutation_lines'][nonstupid_moves[i]];
1238                         hiddenboard = new Chess(base_fen);
1239                         hiddenboard.move(line['pv'][0]);
1240                         var this_response = hiddenboard.move(line['pv'][1]);
1241                         if (response.from !== this_response.from || response.to !== this_response.to) {
1242                                 // Different response depending on lines, abort.
1243                                 response = undefined;
1244                                 break;
1245                         }
1246                 }
1247
1248                 if (nonstupid_moves.length > 0 && response !== undefined) {
1249                         create_arrow(response.from, response.to, '#66f', 6, 20);
1250                 }
1251         }
1252
1253         // Update the refutation lines.
1254         base_fen = data['position']['fen'];
1255         move_num = parseInt(data['position']['move_num']);
1256         toplay = data['position']['toplay'];
1257         refutation_lines = hash_refutation_lines || data['refutation_lines'];
1258         update_refutation_lines();
1259
1260         // Update the sparkline last, since its size depends on how everything else reflowed.
1261         update_sparkline(data);
1262 }
1263
1264 var update_sparkline = function(data) {
1265         if (data && data['score_history']) {
1266                 var first_move_num = undefined;
1267                 for (var halfmove_num in data['score_history']) {
1268                         halfmove_num = parseInt(halfmove_num);
1269                         if (first_move_num === undefined || halfmove_num < first_move_num) {
1270                                 first_move_num = halfmove_num;
1271                         }
1272                 }
1273                 if (first_move_num !== undefined) {
1274                         var last_move_num = data['position']['move_num'] * 2 - 3;
1275                         if (data['position']['toplay'] === 'B') {
1276                                 ++last_move_num;
1277                         }
1278
1279                         // Possibly truncate some moves if we don't have enough width.
1280                         // FIXME: Sometimes width() for #scorecontainer (and by extent,
1281                         // #scoresparkcontainer) on Chrome for mobile seems to start off
1282                         // at something very small, and then suddenly snap back into place.
1283                         // Figure out why.
1284                         var max_moves = Math.floor($("#scoresparkcontainer").width() / 5) - 5;
1285                         if (last_move_num - first_move_num > max_moves) {
1286                                 first_move_num = last_move_num - max_moves;
1287                         }
1288
1289                         var min_score = -100;
1290                         var max_score = 100;
1291                         var last_score = null;
1292                         var scores = [];
1293                         for (var halfmove_num = first_move_num; halfmove_num <= last_move_num; ++halfmove_num) {
1294                                 if (data['score_history'][halfmove_num]) {
1295                                         var score = compute_plot_score(data['score_history'][halfmove_num]);
1296                                         last_score = score;
1297                                         if (score < min_score) min_score = score;
1298                                         if (score > max_score) max_score = score;
1299                                 }
1300                                 scores.push(last_score);
1301                         }
1302                         if (data['score']) {
1303                                 scores.push(compute_plot_score(data['score']));
1304                         }
1305                         // FIXME: at some widths, calling sparkline() seems to push
1306                         // #scorecontainer under the board.
1307                         $("#scorespark").sparkline(scores, {
1308                                 type: 'bar',
1309                                 zeroColor: 'gray',
1310                                 chartRangeMin: min_score,
1311                                 chartRangeMax: max_score,
1312                                 tooltipFormatter: function(sparkline, options, fields) {
1313                                         // score_history contains the Nth _position_, but format_tooltip
1314                                         // wants to format the Nth _move_; thus the -1.
1315                                         return format_tooltip(data, fields[0].offset + first_move_num - 1);
1316                                 }
1317                         });
1318                 } else {
1319                         $("#scorespark").text("");
1320                 }
1321         } else {
1322                 $("#scorespark").text("");
1323         }
1324 }
1325
1326 /**
1327  * @param {number} num_viewers
1328  */
1329 var update_num_viewers = function(num_viewers) {
1330         if (num_viewers === null) {
1331                 $("#numviewers").text("");
1332         } else if (num_viewers == 1) {
1333                 $("#numviewers").text("You are the only current viewer");
1334         } else {
1335                 $("#numviewers").text(num_viewers + " current viewers");
1336         }
1337 }
1338
1339 var update_clock = function() {
1340         clearTimeout(clock_timer);
1341
1342         var data = displayed_analysis_data || current_analysis_data;
1343         if (!data) return;
1344
1345         if (data['position']) {
1346                 var result = data['position']['result'];
1347                 if (result === '1-0') {
1348                         $("#whiteclock").text("1");
1349                         $("#blackclock").text("0");
1350                         $("#whiteclock").removeClass("running-clock");
1351                         $("#blackclock").removeClass("running-clock");
1352                         return;
1353                 }
1354                 if (result === '1/2-1/2') {
1355                         $("#whiteclock").text("1/2");
1356                         $("#blackclock").text("1/2");
1357                         $("#whiteclock").removeClass("running-clock");
1358                         $("#blackclock").removeClass("running-clock");
1359                         return;
1360                 }       
1361                 if (result === '0-1') {
1362                         $("#whiteclock").text("0");
1363                         $("#blackclock").text("1");
1364                         $("#whiteclock").removeClass("running-clock");
1365                         $("#blackclock").removeClass("running-clock");
1366                         return;
1367                 }
1368         }
1369
1370         var white_clock_ms = null;
1371         var black_clock_ms = null;
1372
1373         // Static clocks.
1374         if (data['position'] &&
1375             data['position']['white_clock'] &&
1376             data['position']['black_clock']) {
1377                 white_clock_ms = data['position']['white_clock'] * 1000;
1378                 black_clock_ms = data['position']['black_clock'] * 1000;
1379         }
1380
1381         // Dynamic clock (only one, obviously).
1382         var color;
1383         if (data['position']['white_clock_target']) {
1384                 color = "white";
1385                 $("#whiteclock").addClass("running-clock");
1386                 $("#blackclock").removeClass("running-clock");
1387         } else if (data['position']['black_clock_target']) {
1388                 color = "black";
1389                 $("#whiteclock").removeClass("running-clock");
1390                 $("#blackclock").addClass("running-clock");
1391         } else {
1392                 $("#whiteclock").removeClass("running-clock");
1393                 $("#blackclock").removeClass("running-clock");
1394         }
1395         var remaining_ms;
1396         if (color) {
1397                 var now = new Date().getTime() + client_clock_offset_ms;
1398                 remaining_ms = data['position'][color + '_clock_target'] * 1000 - now;
1399                 if (color === "white") {
1400                         white_clock_ms = remaining_ms;
1401                 } else {
1402                         black_clock_ms = remaining_ms;
1403                 }
1404         }
1405
1406         if (white_clock_ms === null || black_clock_ms === null) {
1407                 $("#whiteclock").empty();
1408                 $("#blackclock").empty();
1409                 return;
1410         }
1411
1412         // If either player has ten minutes or less left, add the second counters.
1413         var show_seconds = (white_clock_ms < 60 * 10 * 1000 || black_clock_ms < 60 * 10 * 1000);
1414
1415         if (color) {
1416                 // See when the clock will change next, and update right after that.
1417                 var next_update_ms;
1418                 if (show_seconds) {
1419                         next_update_ms = remaining_ms % 1000 + 100;
1420                 } else {
1421                         next_update_ms = remaining_ms % 60000 + 100;
1422                 }
1423                 clock_timer = setTimeout(update_clock, next_update_ms);
1424         }
1425
1426         $("#whiteclock").text(format_clock(white_clock_ms, show_seconds));
1427         $("#blackclock").text(format_clock(black_clock_ms, show_seconds));
1428 }
1429
1430 /**
1431  * @param {Number} remaining_ms
1432  * @param {boolean} show_seconds
1433  */
1434 var format_clock = function(remaining_ms, show_seconds) {
1435         if (remaining_ms <= 0) {
1436                 if (show_seconds) {
1437                         return "00:00:00";
1438                 } else {
1439                         return "00:00";
1440                 }
1441         }
1442
1443         var remaining = Math.floor(remaining_ms / 1000);
1444         var seconds = remaining % 60;
1445         remaining = (remaining - seconds) / 60;
1446         var minutes = remaining % 60;
1447         remaining = (remaining - minutes) / 60;
1448         var hours = remaining;
1449         if (show_seconds) {
1450                 return format_2d(hours) + ":" + format_2d(minutes) + ":" + format_2d(seconds);
1451         } else {
1452                 return format_2d(hours) + ":" + format_2d(minutes);
1453         }
1454 }
1455
1456 /**
1457  * @param {Number} x
1458  */
1459 var format_2d = function(x) {
1460         if (x >= 10) {
1461                 return x;
1462         } else {
1463                 return "0" + x;
1464         }
1465 }
1466
1467 /**
1468  * @param {string} move
1469  * @param {Number} move_num Move number of this move.
1470  * @param {boolean} white_to_play Whether white is to play this move.
1471  */
1472 var format_move_with_number = function(move, move_num, white_to_play) {
1473         var ret;
1474         if (white_to_play) {
1475                 ret = move_num + '. ';
1476         } else {
1477                 ret = move_num + '… ';
1478         }
1479         ret += move;
1480         return ret;
1481 }
1482
1483 /**
1484  * @param {string} move
1485  * @param {Number} halfmove_num Half-move number that is to be played,
1486  *   starting from 0.
1487  */
1488 var format_halfmove_with_number = function(move, halfmove_num) {
1489         return format_move_with_number(
1490                 move,
1491                 Math.floor(halfmove_num / 2) + 1,
1492                 halfmove_num % 2 == 0);
1493 }
1494
1495 /**
1496  * @param {Object} data
1497  * @param {Number} halfmove_num
1498  */
1499 var format_tooltip = function(data, halfmove_num) {
1500         if (data['score_history'][halfmove_num + 1] ||
1501             (halfmove_num + 1) === data['position']['history'].length) {
1502                 // Position is in the history, or it is the current position
1503                 // (which is implicitly tacked onto the history).
1504                 var move;
1505                 var short_score;
1506                 if ((halfmove_num + 1) === data['position']['history'].length) {
1507                         move = data['position']['last_move'];
1508                         short_score = format_short_score(data['score']);
1509                 } else {
1510                         move = data['position']['history'][halfmove_num];
1511                         short_score = format_short_score(data['score_history'][halfmove_num + 1]);
1512                 }
1513                 if (halfmove_num === -1) {
1514                         return "Start position: " + short_score;
1515                 } else {
1516                         var move_with_number = format_halfmove_with_number(move, halfmove_num);
1517                         return "After " + move_with_number + ": " + short_score;
1518                 }
1519         } else {
1520                 for (var i = halfmove_num; i --> -1; ) {
1521                         if (data['score_history'][i]) {
1522                                 var move = data['position']['history'][i];
1523                                 if (i === -1) {
1524                                         return "[Analysis kept from start position]";
1525                                 } else {
1526                                         return "[Analysis kept from " + format_halfmove_with_number(move, i) + "]";
1527                                 }
1528                         }
1529                 }
1530         }
1531 }
1532
1533 /**
1534  * @param {boolean} sort_by_score
1535  */
1536 var resort_refutation_lines = function(sort_by_score) {
1537         sort_refutation_lines_by_score = sort_by_score;
1538         if (supports_html5_storage()) {
1539                 localStorage['sort_refutation_lines_by_score'] = sort_by_score ? 1 : 0;
1540         }
1541         update_refutation_lines();
1542 }
1543 window['resort_refutation_lines'] = resort_refutation_lines;
1544
1545 /**
1546  * @param {boolean} truncate_history
1547  */
1548 var set_truncate_history = function(truncate_history) {
1549         truncate_display_history = truncate_history;
1550         update_refutation_lines();
1551 }
1552 window['set_truncate_history'] = set_truncate_history;
1553
1554 /**
1555  * @param {number} line_num
1556  * @param {number} move_num
1557  */
1558 var show_line = function(line_num, move_num) {
1559         if (line_num == -1) {
1560                 current_display_line = null;
1561                 current_display_move = null;
1562                 hash_refutation_lines = null;
1563                 if (displayed_analysis_data) {
1564                         // TODO: Support exiting to history position if we are in an
1565                         // analysis line of a history position.
1566                         displayed_analysis_data = null;
1567                 }
1568                 update_board();
1569                 return;
1570         } else {
1571                 current_display_line = jQuery.extend({}, display_lines[line_num]);  // Shallow clone.
1572                 current_display_move = move_num + current_display_line.start_display_move_num;
1573         }
1574         current_display_line_is_history = (line_num == 0);
1575
1576         update_historic_analysis();
1577         update_displayed_line();
1578         update_board_highlight();
1579         update_move_highlight();
1580         redraw_arrows();
1581 }
1582 window['show_line'] = show_line;
1583
1584 var prev_move = function() {
1585         if (current_display_line &&
1586             current_display_move >= current_display_line.start_display_move_num) {
1587                 --current_display_move;
1588         }
1589         update_historic_analysis();
1590         update_displayed_line();
1591         update_move_highlight();
1592 }
1593 window['prev_move'] = prev_move;
1594
1595 var next_move = function() {
1596         if (current_display_line &&
1597             current_display_move < current_display_line.pv.length - 1) {
1598                 ++current_display_move;
1599         }
1600         update_historic_analysis();
1601         update_displayed_line();
1602         update_move_highlight();
1603 }
1604 window['next_move'] = next_move;
1605
1606 var next_game = function() {
1607         if (current_games === null) {
1608                 return;
1609         }
1610
1611         // Try to find the game we are currently looking at.
1612         for (var game_num = 0; game_num < current_games.length; ++game_num) {
1613                 var game = current_games[game_num];
1614                 if (game['url'] === backend_url) {
1615                         var next_game_num = (game_num + 1) % current_games.length;
1616                         switch_backend(current_games[next_game_num]);
1617                         return;
1618                 }
1619         }
1620
1621         // Couldn't find it; give up.
1622 }
1623
1624 var update_historic_analysis = function() {
1625         if (!current_display_line_is_history) {
1626                 return;
1627         }
1628         if (current_display_move == current_display_line.pv.length - 1) {
1629                 displayed_analysis_data = null;
1630                 update_board();
1631         }
1632
1633         // Fetch old analysis for this line if it exists.
1634         var hiddenboard = chess_from(null, current_display_line.pv, current_display_move);
1635         var filename = "/history/move" + (current_display_move + 1) + "-" +
1636                 hiddenboard.fen().replace(/ /g, '_').replace(/\//g, '-') + ".json";
1637
1638         current_historic_xhr = $.ajax({
1639                 url: filename
1640         }).done(function(data, textstatus, xhr) {
1641                 displayed_analysis_data = data;
1642                 update_board();
1643         }).fail(function(jqXHR, textStatus, errorThrown) {
1644                 if (textStatus === "abort") {
1645                         // Aborted because we are switching backends. Don't do anything;
1646                         // we will already have been cleared.
1647                 } else {
1648                         displayed_analysis_data = {'failed': true};
1649                         update_board();
1650                 }
1651         });
1652 }
1653
1654 /**
1655  * @param {string} fen
1656  */
1657 var update_imbalance = function(fen) {
1658         var hiddenboard = new Chess(fen);
1659         var imbalance = {'k': 0, 'q': 0, 'r': 0, 'b': 0, 'n': 0, 'p': 0};
1660         for (var row = 0; row < 8; ++row) {
1661                 for (var col = 0; col < 8; ++col) {
1662                         var col_text = String.fromCharCode('a1'.charCodeAt(0) + col);
1663                         var row_text = String.fromCharCode('a1'.charCodeAt(1) + row);
1664                         var square = col_text + row_text;
1665                         var contents = hiddenboard.get(square);
1666                         if (contents !== null) {
1667                                 if (contents.color === 'w') {
1668                                         ++imbalance[contents.type];
1669                                 } else {
1670                                         --imbalance[contents.type];
1671                                 }
1672                         }
1673                 }
1674         }
1675         var white_imbalance = '';
1676         var black_imbalance = '';
1677         for (var piece in imbalance) {
1678                 for (var i = 0; i < imbalance[piece]; ++i) {
1679                         white_imbalance += '<img src="img/chesspieces/wikipedia/w' + piece.toUpperCase() + '.png" alt="" style="width: 15px;height: 15px;">';
1680                 }
1681                 for (var i = 0; i < -imbalance[piece]; ++i) {
1682                         black_imbalance += '<img src="img/chesspieces/wikipedia/b' + piece.toUpperCase() + '.png" alt="" style="width: 15px;height: 15px;">';
1683                 }
1684         }
1685         $('#whiteimbalance').html(white_imbalance);
1686         $('#blackimbalance').html(black_imbalance);
1687 }
1688
1689 /** Mark the currently selected move in red.
1690  * Also replaces the PV with the current displayed line if it's not shown
1691  * anywhere else on the screen.
1692  */
1693 var update_move_highlight = function() {
1694         if (highlighted_move !== null) {
1695                 highlighted_move.removeClass('highlight'); 
1696         }
1697         if (current_display_line) {
1698                 var display_line_num = find_display_line_matching_num();
1699                 if (display_line_num === null) {
1700                         // Replace the PV with the (complete) line.
1701                         $("#pvtitle").text("Exploring:");
1702                         current_display_line.start_display_move_num = 0;
1703                         display_lines.push(current_display_line);
1704                         $("#pv").html(print_pv(display_lines.length - 1));
1705                         display_line_num = display_lines.length - 1;
1706
1707                         // Clear out the PV, so it's not selected by anything later.
1708                         display_lines[1].pv = [];
1709                 }
1710
1711                 highlighted_move = $("#automove" + display_line_num + "-" + (current_display_move - current_display_line.start_display_move_num));
1712                 highlighted_move.addClass('highlight');
1713         }
1714 }
1715
1716 /**
1717  * See if the current displayed line is identical to any of the ones
1718  * we have on screen. (It might not be if e.g. the analysis reloaded
1719  * since we started looking.)
1720  *
1721  * @return {?number}
1722  */
1723 var find_display_line_matching_num = function() {
1724         for (var i = 0; i < display_lines.length; ++i) {
1725                 var line = display_lines[i];
1726                 if (line.start_display_move_num > 0) continue;
1727                 if (current_display_line.start_fen !== line.start_fen) continue;
1728                 if (current_display_line.pv.length !== line.pv.length) continue;
1729                 var ok = true;
1730                 for (var j = 0; j < line.pv.length; ++j) {
1731                         if (current_display_line.pv[j] !== line.pv[j]) {
1732                                 ok = false;
1733                                 break;
1734                         }
1735                 }
1736                 if (ok) {
1737                         return i;
1738                 }
1739         }
1740         return null;
1741 }
1742
1743 /** Update the board based on the currently displayed line.
1744  * 
1745  * TODO: This should really be called only whenever something changes,
1746  * instead of all the time.
1747  */
1748 var update_displayed_line = function() {
1749         if (current_display_line === null) {
1750                 $("#linenav").hide();
1751                 $("#linemsg").show();
1752                 display_fen = base_fen;
1753                 set_board_position(base_fen);
1754                 update_imbalance(base_fen);
1755                 return;
1756         }
1757
1758         $("#linenav").show();
1759         $("#linemsg").hide();
1760
1761         if (current_display_move <= 0) {
1762                 $("#prevmove").html("Previous");
1763         } else {
1764                 $("#prevmove").html("<a href=\"javascript:prev_move();\">Previous</a></span>");
1765         }
1766         if (current_display_move == current_display_line.pv.length - 1) {
1767                 $("#nextmove").html("Next");
1768         } else {
1769                 $("#nextmove").html("<a href=\"javascript:next_move();\">Next</a></span>");
1770         }
1771
1772         var hiddenboard = chess_from(current_display_line.start_fen, current_display_line.pv, current_display_move);
1773         set_board_position(hiddenboard.fen());
1774         if (display_fen !== hiddenboard.fen() && !current_display_line_is_history) {
1775                 // Fire off a hash request, since we're now off the main position
1776                 // and it just changed.
1777                 explore_hash(hiddenboard.fen());
1778         }
1779         display_fen = hiddenboard.fen();
1780         update_imbalance(hiddenboard.fen());
1781 }
1782
1783 var set_board_position = function(new_fen) {
1784         board_is_animating = true;
1785         var old_fen = board.fen();
1786         board.position(new_fen);
1787         if (board.fen() === old_fen) {
1788                 board_is_animating = false;
1789         }
1790 }
1791
1792 /**
1793  * @param {boolean} param_enable_sound
1794  */
1795 var set_sound = function(param_enable_sound) {
1796         enable_sound = param_enable_sound;
1797         if (enable_sound) {
1798                 $("#soundon").html("<strong>On</strong>");
1799                 $("#soundoff").html("<a href=\"javascript:set_sound(false)\">Off</a>");
1800
1801                 // Seemingly at least Firefox prefers MP3 over Opus; tell it otherwise,
1802                 // and also preload the file since the user has selected audio.
1803                 var ding = document.getElementById('ding');
1804                 if (ding && ding.canPlayType && ding.canPlayType('audio/ogg; codecs="opus"') === 'probably') {
1805                         ding.src = 'ding.opus';
1806                         ding.load();
1807                 }
1808         } else {
1809                 $("#soundon").html("<a href=\"javascript:set_sound(true)\">On</a>");
1810                 $("#soundoff").html("<strong>Off</strong>");
1811         }
1812         if (supports_html5_storage()) {
1813                 localStorage['enable_sound'] = enable_sound ? 1 : 0;
1814         }
1815 }
1816 window['set_sound'] = set_sound;
1817
1818 /** Send off a hash probe request to the backend.
1819  * @param {string} fen
1820  */
1821 var explore_hash = function(fen) {
1822         // If we already have a backend response going, abort it.
1823         if (current_hash_xhr) {
1824                 current_hash_xhr.abort();
1825         }
1826         if (current_hash_display_timer) {
1827                 clearTimeout(current_hash_display_timer);
1828                 current_hash_display_timer = null;
1829         }
1830         $("#refutationlines").empty();
1831         current_hash_xhr = $.ajax({
1832                 url: backend_hash_url + "?fen=" + fen
1833         }).done(function(data, textstatus, xhr) {
1834                 show_explore_hash_results(data, fen);
1835         });
1836 }
1837
1838 /** Process the JSON response from a hash probe request.
1839  * @param {!Object} data
1840  * @param {string} fen
1841  */
1842 var show_explore_hash_results = function(data, fen) {
1843         if (board_is_animating) {
1844                 // Updating while the animation is still going causes
1845                 // the animation to jerk. This is pretty crude, but it will do.
1846                 current_hash_display_timer = setTimeout(function() { show_explore_hash_results(data, fen); }, 100);
1847                 return;
1848         }
1849         current_hash_display_timer = null;
1850         hash_refutation_lines = data['lines'];
1851         update_board();
1852 }
1853
1854 // almost all of this stuff comes from the chessboard.js example page
1855 var onDragStart = function(source, piece, position, orientation) {
1856         var pseudogame = new Chess(display_fen);
1857         if (pseudogame.game_over() === true ||
1858             (pseudogame.turn() === 'w' && piece.search(/^b/) !== -1) ||
1859             (pseudogame.turn() === 'b' && piece.search(/^w/) !== -1)) {
1860                 return false;
1861         }
1862
1863         recommended_move = get_best_move(pseudogame, source, null, pseudogame.turn() === 'b');
1864         if (recommended_move) {
1865                 var squareEl = $('#board .square-' + recommended_move.to);
1866                 squareEl.addClass('highlight1-32417');
1867         }
1868         return true;
1869 }
1870
1871 var mousedownSquare = function(e) {
1872         reverse_dragging_from = null;
1873         var square = $(this).attr('data-square');
1874
1875         var pseudogame = new Chess(display_fen);
1876         if (pseudogame.game_over() === true) {
1877                 return;
1878         }
1879
1880         // If the square is empty, or has a piece of the side not to move,
1881         // we handle it. If not, normal piece dragging will take it.
1882         var position = board.position();
1883         if (!position.hasOwnProperty(square) ||
1884             (pseudogame.turn() === 'w' && position[square].search(/^b/) !== -1) ||
1885             (pseudogame.turn() === 'b' && position[square].search(/^w/) !== -1)) {
1886                 reverse_dragging_from = square;
1887                 recommended_move = get_best_move(pseudogame, null, square, pseudogame.turn() === 'b');
1888                 if (recommended_move) {
1889                         var squareEl = $('#board .square-' + recommended_move.from);
1890                         squareEl.addClass('highlight1-32417');
1891                         squareEl = $('#board .square-' + recommended_move.to);
1892                         squareEl.addClass('highlight1-32417');
1893                 }
1894         }
1895 }
1896
1897 var mouseupSquare = function(e) {
1898         if (reverse_dragging_from === null) {
1899                 return;
1900         }
1901         var source = $(this).attr('data-square');
1902         var target = reverse_dragging_from;
1903         reverse_dragging_from = null;
1904         if (onDrop(source, target) !== 'snapback') {
1905                 onSnapEnd(source, target);
1906         }
1907         $("#board").find('.square-55d63').removeClass('highlight1-32417');
1908 }
1909
1910 var get_best_move = function(game, source, target, invert) {
1911         var moves = game.moves({ verbose: true });
1912         if (source !== null) {
1913                 moves = moves.filter(function(move) { return move.from == source; });
1914         }
1915         if (target !== null) {
1916                 moves = moves.filter(function(move) { return move.to == target; });
1917         }
1918         if (moves.length == 0) {
1919                 return null;
1920         }
1921         if (moves.length == 1) {
1922                 return moves[0];
1923         }
1924
1925         // More than one move. Use the display lines (if we have them)
1926         // to disambiguate; otherwise, we have no information.
1927         var move_hash = {};
1928         for (var i = 0; i < moves.length; ++i) {
1929                 move_hash[moves[i].san] = moves[i];
1930         }
1931
1932         // See if we're already exploring some line.
1933         if (current_display_line &&
1934             current_display_move < current_display_line.pv.length - 1) {
1935                 var first_move = current_display_line.pv[current_display_move + 1];
1936                 if (move_hash[first_move]) {
1937                         return move_hash[first_move];
1938                 }
1939         }
1940
1941         // History and PV take priority over the display lines.
1942         for (var i = 0; i < 2; ++i) {
1943                 var line = display_lines[i];
1944                 var first_move = line.pv[line.start_display_move_num];
1945                 if (move_hash[first_move]) {
1946                         return move_hash[first_move];
1947                 }
1948         }
1949
1950         var best_move = null;
1951         var best_move_score = null;
1952
1953         for (var move in refutation_lines) {
1954                 var line = refutation_lines[move];
1955                 if (!line['score']) {
1956                         continue;
1957                 }
1958                 var first_move = line['pv'][0];
1959                 if (move_hash[first_move]) {
1960                         var score = compute_score_sort_key(line['score'], line['depth'], invert);
1961                         if (best_move_score === null || score > best_move_score) {
1962                                 best_move = move_hash[first_move];
1963                                 best_move_score = score;
1964                         }
1965                 }
1966         }
1967         return best_move;
1968 }
1969
1970 var onDrop = function(source, target) {
1971         if (source === target) {
1972                 if (recommended_move === null) {
1973                         return 'snapback';
1974                 } else {
1975                         // Accept the move. It will be changed in onSnapEnd.
1976                         return;
1977                 }
1978         } else {
1979                 // Suggestion not asked for.
1980                 recommended_move = null;
1981         }
1982
1983         // see if the move is legal
1984         var pseudogame = new Chess(display_fen);
1985         var move = pseudogame.move({
1986                 from: source,
1987                 to: target,
1988                 promotion: 'q' // NOTE: always promote to a queen for example simplicity
1989         });
1990
1991         // illegal move
1992         if (move === null) return 'snapback';
1993 }
1994
1995 var onSnapEnd = function(source, target) {
1996         if (source === target && recommended_move !== null) {
1997                 source = recommended_move.from;
1998                 target = recommended_move.to;
1999         }
2000         recommended_move = null;
2001         var pseudogame = new Chess(display_fen);
2002         var move = pseudogame.move({
2003                 from: source,
2004                 to: target,
2005                 promotion: 'q' // NOTE: always promote to a queen for example simplicity
2006         });
2007
2008         if (current_display_line &&
2009             current_display_move < current_display_line.pv.length - 1 &&
2010             current_display_line.pv[current_display_move + 1] === move.san) {
2011                 next_move();
2012                 return;
2013         }
2014
2015         // Walk down the displayed lines until we find one that starts with
2016         // this move, then select that. Note that this gives us a good priority
2017         // order (history first, then PV, then multi-PV lines).
2018         for (var i = 0; i < display_lines.length; ++i) {
2019                 if (i == 1 && current_display_line) {
2020                         // Do not choose PV if not on it.
2021                         continue;
2022                 }
2023                 var line = display_lines[i];
2024                 if (line.pv[line.start_display_move_num] === move.san) {
2025                         show_line(i, 0);
2026                         return;
2027                 }
2028         }
2029
2030         // Shouldn't really be here if we have hash probes, but there's really
2031         // nothing we can do.
2032 }
2033 // End of dragging-related code.
2034
2035 var fmt_cp = function(v) {
2036         if (v === 0) {
2037                 return "0.00";
2038         } else if (v > 0) {
2039                 return "+" + (v / 100).toFixed(2);
2040         } else {
2041                 v = -v;
2042                 return "-" + (v / 100).toFixed(2);
2043         }
2044 }
2045
2046 var format_short_score = function(score) {
2047         if (!score) {
2048                 return "???";
2049         }
2050         if (score[0] === 'm') {
2051                 if (score[2]) {  // Is a bound.
2052                         return score[2] + "\u00a0M " + score[1];
2053                 } else {
2054                         return "M " + score[1];
2055                 }
2056         } else if (score[0] === 'd') {
2057                 return "TB draw";
2058         } else if (score[0] === 'cp') {
2059                 if (score[2]) {  // Is a bound.
2060                         return score[2] + "\u00a0" + fmt_cp(score[1]);
2061                 } else {
2062                         return fmt_cp(score[1]);
2063                 }
2064         }
2065         return null;
2066 }
2067
2068 var format_long_score = function(score) {
2069         if (!score) {
2070                 return "???";
2071         }
2072         if (score[0] === 'm') {
2073                 if (score[1] > 0) {
2074                         return "White mates in " + score[1];
2075                 } else {
2076                         return "Black mates in " + (-score[1]);
2077                 }
2078         } else if (score[0] === 'd') {
2079                 return "Theoretical draw";
2080         } else if (score[0] === 'cp') {
2081                 return "Score: " + format_short_score(score);
2082         }
2083         return null;
2084 }
2085
2086 var compute_plot_score = function(score) {
2087         if (score[0] === 'm') {
2088                 if (score[1] > 0) {
2089                         return 500;
2090                 } else {
2091                         return -500;
2092                 }
2093         } else if (score[0] === 'd') {
2094                 return 0;
2095         } else if (score[0] === 'cp') {
2096                 if (score[1] > 500) {
2097                         return 500;
2098                 } else if (score[1] < -500) {
2099                         return -500;
2100                 } else {
2101                         return score[1];
2102                 }
2103         }
2104         return null;
2105 }
2106
2107 /**
2108  * @param score The score digest tuple.
2109  * @param {?number} depth Depth the move has been computed to, or null.
2110  * @param {boolean} invert Whether black is to play.
2111  * @param {boolean=} depth_secondary_key
2112  * @return {number}
2113  */
2114 var compute_score_sort_key = function(score, depth, invert, depth_secondary_key) {
2115         var s;
2116         if (!score) {
2117                 return -10000000;
2118         }
2119         if (score[0] === 'm') {
2120                 if (score[1] > 0) {
2121                         // White mates.
2122                         s = 99999 - score[1];
2123                 } else {
2124                         // Black mates (note the double negative for score[1]).
2125                         s = -99999 - score[1];
2126                 }
2127         } else if (score[0] === 'd') {
2128                 s = 0;
2129         } else if (score[0] === 'cp') {
2130                 s = score[1];
2131         }
2132         if (s) {
2133                 if (invert) s = -s;
2134                 if (depth_secondary_key) {
2135                         return s * 200 + (depth || 0);
2136                 } else {
2137                         return s;
2138                 }
2139         } else {
2140                 return null;
2141         }
2142 }
2143
2144 /**
2145  * @param {Object} game
2146  */
2147 var switch_backend = function(game) {
2148         // Stop looking at historic data.
2149         current_display_line = null;
2150         current_display_move = null;
2151         displayed_analysis_data = null;
2152         if (current_historic_xhr) {
2153                 current_historic_xhr.abort();
2154         }
2155
2156         // If we already have a backend response going, abort it.
2157         if (current_analysis_xhr) {
2158                 current_analysis_xhr.abort();
2159         }
2160         if (current_hash_xhr) {
2161                 current_hash_xhr.abort();
2162         }
2163
2164         // Otherwise, we should have a timer going to start a new one.
2165         // Kill that, too.
2166         if (current_analysis_request_timer) {
2167                 clearTimeout(current_analysis_request_timer);
2168                 current_analysis_request_timer = null;
2169         }
2170         if (current_hash_display_timer) {
2171                 clearTimeout(current_hash_display_timer);
2172                 current_hash_display_timer = null;
2173         }
2174
2175         // Request an immediate fetch with the new backend.
2176         backend_url = game['url'];
2177         backend_hash_url = game['hashurl'];
2178         window.location.hash = '#' + game['id'];
2179         current_analysis_data = null;
2180         ims = 0;
2181         request_update();
2182 }
2183 window['switch_backend'] = switch_backend;
2184
2185 var init = function() {
2186         unique = get_unique();
2187
2188         // Load settings from HTML5 local storage if available.
2189         if (supports_html5_storage() && localStorage['enable_sound']) {
2190                 set_sound(parseInt(localStorage['enable_sound']));
2191         } else {
2192                 set_sound(false);
2193         }
2194         if (supports_html5_storage() && localStorage['sort_refutation_lines_by_score']) {
2195                 sort_refutation_lines_by_score = parseInt(localStorage['sort_refutation_lines_by_score']);
2196         } else {
2197                 sort_refutation_lines_by_score = true;
2198         }
2199
2200         // Create board.
2201         board = new window.ChessBoard('board', {
2202                 onMoveEnd: function() { board_is_animating = false; },
2203
2204                 draggable: true,
2205                 onDragStart: onDragStart,
2206                 onDrop: onDrop,
2207                 onSnapEnd: onSnapEnd
2208         });
2209         $("#board").on('mousedown', '.square-55d63', mousedownSquare);
2210         $("#board").on('mouseup', '.square-55d63', mouseupSquare);
2211
2212         request_update();
2213         $(window).resize(function() {
2214                 board.resize();
2215                 update_sparkline(displayed_analysis_data || current_analysis_data);
2216                 update_board_highlight();
2217                 redraw_arrows();
2218         });
2219         $(window).keyup(function(event) {
2220                 if (event.which == 39) {  // Left arrow.
2221                         next_move();
2222                 } else if (event.which == 37) {  // Right arrow.
2223                         prev_move();
2224                 } else if (event.which >= 49 && event.which <= 57) {  // 1-9.
2225                         var num = event.which - 49;
2226                         if (current_games && current_games.length >= num) {
2227                                 switch_backend(current_games[num]);
2228                         }
2229                 } else if (event.which == 78) {  // N.
2230                         next_game();
2231                 }
2232         });
2233         window.addEventListener('hashchange', possibly_switch_game_from_hash, false);
2234 };
2235 $(document).ready(init);
2236
2237 })();