X-Git-Url: https://git.sesse.net/?p=remoteglot;a=blobdiff_plain;f=www%2Fjs%2Fremoteglot.js;h=da9f70a17f49522d464f8ba6236d47beaeccf8c1;hp=ac3f8e97adc6d29a08f92ed4027de9f5dac5e582;hb=e013c00f3db60d47d7911b7c2e6c2219d5e1a148;hpb=80661ee7ca9f379b14dfd660362b05b7c455b7aa

diff --git a/www/js/remoteglot.js b/www/js/remoteglot.js
index ac3f8e9..da9f70a 100644
--- a/www/js/remoteglot.js
+++ b/www/js/remoteglot.js
@@ -1,8 +1,28 @@
 (function() {
 
+/**
+ * Version of this script. If the server returns a version larger than
+ * this, it is a sign we should reload to upgrade ourselves.
+ *
+ * @type {Number}
+ * @const
+ * @private */
+var SCRIPT_VERSION = 2015062104;
+
+/**
+ * The current backend URL.
+ *
+ * @type {!string}
+ * @private
+ */
+var backend_url = "/analysis.pl";
+
 /** @type {window.ChessBoard} @private */
 var board = null;
 
+/** @type {boolean} @private */
+var board_is_animating = false;
+
 /**
  * The most recent analysis data we have from the server
  * (about the most recent position).
@@ -20,6 +40,18 @@ var current_analysis_data = null;
  */
 var displayed_analysis_data = null;
 
+/**
+ * Games currently in progress, if any.
+ *
+ * @type {?Array.<{
+ *      name: string,
+ *      url: string,
+ *      id: string,
+ * }>}
+ * @private
+ */
+var current_games = null;
+
 /** @type {Array.<{
  *      from_col: number,
  *      from_row: number,
@@ -59,7 +91,9 @@ var highlight_from = undefined;
 /** @type {!string|undefined} @private */
 var highlight_to = undefined;
 
-/** @type {?jQuery} @private */
+/** The HTML object of the move currently being highlighted (in red).
+ * @type {?jQuery}
+ * @private */
 var highlighted_move = null;
 
 /** @type {?number} @private */
@@ -68,6 +102,18 @@ var unique = null;
 /** @type {boolean} @private */
 var enable_sound = false;
 
+/**
+ * Our best estimate of how many milliseconds we need to add to 
+ * new Date() to get the true UTC time. Calibrated against the
+ * server clock.
+ *
+ * @type {?number}
+ * @private
+ */
+var client_clock_offset_ms = null;
+
+var clock_timer = null;
+
 /** The current position on the board, represented as a FEN string.
  * @type {?string}
  * @private
@@ -76,13 +122,17 @@ var fen = null;
 
 /** @typedef {{
  *    start_fen: string,
- *    uci_pv: Array.<string>,
  *    pretty_pv: Array.<string>,
- *    line_num: number
  * }} DisplayLine
  */
 
-/** @type {Array.<DisplayLine>}
+/** All PVs that we currently know of.
+ *
+ * Element 0 is history (or null if no history).
+ * Element 1 is current main PV.
+ * All remaining elements are refutation lines (multi-PV).
+ *
+ * @type {Array.<DisplayLine>}
  * @private
  */
 var display_lines = [];
@@ -96,6 +146,32 @@ var current_display_line_is_history = false;
 /** @type {?number} @private */
 var current_display_move = null;
 
+/**
+ * The current backend request to get main analysis (not history), if any,
+ * so that we can abort it.
+ *
+ * @type {?jqXHR}
+ * @private
+ */
+var current_analysis_xhr = null;
+
+/**
+ * The current timer to fire off a request to get main analysis (not history),
+ * if any, so that we can abort it.
+ *
+ * @type {?Number}
+ * @private
+ */
+var current_analysis_request_timer = null;
+
+/**
+ * The current backend request to get historic data, if any.
+ *
+ * @type {?jqXHR}
+ * @private
+ */
+var current_historic_xhr = null;
+
 var supports_html5_storage = function() {
 	try {
 		return 'localStorage' in window && window['localStorage'] !== null;
@@ -119,21 +195,43 @@ var get_unique = function() {
 }
 
 var request_update = function() {
-	$.ajax({
-		url: "/analysis.pl?ims=" + ims + "&unique=" + unique
+	current_analysis_request_timer = null;
+
+	current_analysis_xhr = $.ajax({
+		url: backend_url + "?ims=" + ims + "&unique=" + unique
 	}).done(function(data, textstatus, xhr) {
-		ims = xhr.getResponseHeader('X-Remoteglot-Last-Modified');
-		var num_viewers = xhr.getResponseHeader('X-Remoteglot-Num-Viewers');
-		possibly_play_sound(current_analysis_data, data);
-		current_analysis_data = data;
-		update_board(current_analysis_data, displayed_analysis_data);
+		sync_server_clock(xhr.getResponseHeader('Date'));
+		ims = xhr.getResponseHeader('X-RGLM');
+		var num_viewers = xhr.getResponseHeader('X-RGNV');
+		var new_data;
+		if (Array.isArray(data)) {
+			new_data = JSON.parse(JSON.stringify(current_analysis_data));
+			JSON_delta.patch(new_data, data);
+		} else {
+			new_data = data;
+		}
+
+		var minimum_version = xhr.getResponseHeader('X-RGMV');
+		if (minimum_version && minimum_version > SCRIPT_VERSION) {
+			// Upgrade to latest version with a force-reload.
+			location.reload(true);
+		}
+
+		possibly_play_sound(current_analysis_data, new_data);
+		current_analysis_data = new_data;
+		update_board();
 		update_num_viewers(num_viewers);
 
 		// Next update.
-		setTimeout(function() { request_update(); }, 100);
-	}).fail(function() {
-		// Wait ten seconds, then try again.
-		setTimeout(function() { request_update(); }, 10000);
+		current_analysis_request_timer = setTimeout(function() { request_update(); }, 100);
+	}).fail(function(jqXHR, textStatus, errorThrown) {
+		if (textStatus === "abort") {
+			// Aborted because we are switching backends. Abandon and don't retry,
+			// because another one is already started for us.
+		} else {
+			// Backend error or similar. Wait ten seconds, then try again.
+			current_analysis_request_timer = setTimeout(function() { request_update(); }, 10000);
+		}
 	});
 }
 
@@ -145,7 +243,7 @@ var possibly_play_sound = function(old_data, new_data) {
 		return;
 	}
 	var ding = document.getElementById('ding');
-	if (ding && ding.play !== undefined) {
+	if (ding && ding.play) {
 		if (old_data['position'] && old_data['position']['fen'] &&
 		    new_data['position'] && new_data['position']['fen'] &&
 		    (old_data['position']['fen'] !== new_data['position']['fen'] ||
@@ -155,10 +253,29 @@ var possibly_play_sound = function(old_data, new_data) {
 	}
 }
 
+/**
+ * @type {!string} server_date_string
+ */
+var sync_server_clock = function(server_date_string) {
+	var server_time_ms = new Date(server_date_string).getTime();
+	var client_time_ms = new Date().getTime();
+	var estimated_offset_ms = server_time_ms - client_time_ms;
+
+	// In order not to let the noise move us too much back and forth
+	// (the server only has one-second resolution anyway), we only
+	// change an existing skew if we are at least five seconds off.
+	if (client_clock_offset_ms === null ||
+	    Math.abs(estimated_offset_ms - client_clock_offset_ms) > 5000) {
+		client_clock_offset_ms = estimated_offset_ms;
+	}
+}
+
 var clear_arrows = function() {
 	for (var i = 0; i < arrows.length; ++i) {
 		if (arrows[i].svg) {
-			arrows[i].svg.parentElement.removeChild(arrows[i].svg);
+			if (arrows[i].svg.parentElement) {
+				arrows[i].svg.parentElement.removeChild(arrows[i].svg);
+			}
 			delete arrows[i].svg;
 		}
 	}
@@ -273,7 +390,9 @@ var point_from_end = function(x1, y1, x2, y2, t, u) {
 
 var position_arrow = function(arrow) {
 	if (arrow.svg) {
-		arrow.svg.parentElement.removeChild(arrow.svg);
+		if (arrow.svg.parentElement) {
+			arrow.svg.parentElement.removeChild(arrow.svg);
+		}
 		delete arrow.svg;
 	}
 	if (current_display_line !== null && !current_display_line_is_history) {
@@ -454,7 +573,6 @@ var add_pv = function(fen, pretty_pv, move_num, toplay, opt_limit, opt_showlast)
 	display_lines.push({
 		start_fen: fen,
 		pretty_pv: pretty_pv,
-		line_number: display_lines.length
 	});
 	return print_pv(display_lines.length - 1, pretty_pv, move_num, toplay, opt_limit, opt_showlast);
 }
@@ -509,7 +627,10 @@ var print_pv = function(line_num, pretty_pv, move_num, toplay, opt_limit, opt_sh
 	return pv;
 }
 
-var update_highlight = function() {
+/** Update the highlighted to/from squares on the board.
+ * Based on the global "highlight_from" and "highlight_to" variables.
+ */
+var update_board_highlight = function() {
 	$("#board").find('.square-55d63').removeClass('nonuglyhighlight');
 	if ((current_display_line === null || current_display_line_is_history) &&
 	    highlight_from !== undefined && highlight_to !== undefined) {
@@ -539,11 +660,16 @@ var collapse_history = function(truncate_history) {
 }
 window['collapse_history'] = collapse_history;
 
+/** Update the HTML display of multi-PV from the global "refutation_lines".
+ *
+ * Also recreates the global "display_lines".
+ */
 var update_refutation_lines = function() {
 	if (fen === null) {
 		return;
 	}
 	if (display_lines.length > 2) {
+		// Truncate so that only the history and PV is left.
 		display_lines = [ display_lines[0], display_lines[1] ];
 	}
 
@@ -597,14 +723,86 @@ var update_refutation_lines = function() {
 		$("#sortbyscore0").html("<strong>Move</strong>");
 		$("#sortbyscore1").html("<a href=\"javascript:resort_refutation_lines(true)\">Score</a>");
 	}
+
+	// Update the move highlight, as we've rewritten all the HTML.
+	update_move_highlight();
 }
 
 /**
- * @param {Object} data
- * @param {?Object} display_data
+ * Create a Chess.js board object, containing the given position plus the given moves,
+ * up to the given limit.
+ *
+ * @param {?string} fen
+ * @param {Array.<string>} moves
+ * @param {number} last_move
+ */
+var chess_from = function(fen, moves, last_move) {
+	var hiddenboard = new Chess();
+	if (fen !== null) {
+		hiddenboard.load(fen);
+	}
+	for (var i = 0; i <= last_move; ++i) {
+		if (moves[i] === '0-0') {
+			hiddenboard.move('O-O');
+		} else if (moves[i] === '0-0-0') {
+			hiddenboard.move('O-O-O');
+		} else {
+			hiddenboard.move(moves[i]);
+		}
+	}
+	return hiddenboard;
+}
+
+var update_game_list = function(games) {
+	$("#games").text("");
+	if (games === null) {
+		return;
+	}
+
+	var games_div = document.getElementById('games');
+	for (var game_num = 0; game_num < games.length; ++game_num) {
+		var game = games[game_num];
+		var game_span = document.createElement("span");
+		game_span.setAttribute("class", "game");
+
+		var game_name = document.createTextNode(game['name']);
+		if (game['url'] === backend_url) {
+			game_span.appendChild(game_name);
+		} else {
+			var game_a = document.createElement("a");
+			game_a.setAttribute("href", "#" + game['id']);
+			game_a.appendChild(game_name);
+			game_span.appendChild(game_a);
+		}
+		games_div.appendChild(game_span);
+	}
+}
+
+/**
+ * Try to find a running game that matches with the current hash,
+ * and switch to it if we're not already displaying it.
  */
-var update_board = function(current_data, display_data) {
-	var data = display_data || current_data;
+var possibly_switch_game_from_hash = function() {
+	if (current_games === null) {
+		return;
+	}
+
+	var hash = window.location.hash.replace(/^#/,'');
+	for (var i = 0; i < current_games.length; ++i) {
+		if (current_games[i]['id'] === hash) {
+			if (backend_url !== current_games[i]['url']) {
+				switch_backend(current_games[i]['url']);
+			}
+			return;
+		}
+	}
+}
+
+/** Update all the HTML on the page, based on current global state.
+ */
+var update_board = function() {
+	var data = displayed_analysis_data || current_analysis_data;
+	var current_data = current_analysis_data;  // Convenience alias.
 
 	display_lines = [];
 
@@ -618,6 +816,16 @@ var update_board = function(current_data, display_data) {
 	}
 	update_history();
 
+	// Games currently in progress, if any.
+	if (current_data['games']) {
+		current_games = current_data['games'];
+		possibly_switch_game_from_hash();
+		update_game_list(current_data['games']);
+	} else {
+		current_games = null;
+		update_game_list(null);
+	}
+
 	// The headline. Names are always fetched from current_data;
 	// the rest can depend a bit.
 	var headline;
@@ -629,14 +837,57 @@ var update_board = function(current_data, display_data) {
 		headline = 'Analysis';
 	}
 
+	// Credits, where applicable. Note that we don't want the footer to change a lot
+	// when e.g. viewing history, so if any of these changed during the game,
+	// use the current one still.
+	if (current_data['using_lomonosov']) {
+		$("#lomonosov").show();
+	} else {
+		$("#lomonosov").hide();
+	}
+
+	// Credits: The engine name/version.
+	if (current_data['engine'] && current_data['engine']['name'] !== null) {
+		$("#engineid").text(current_data['engine']['name']);
+	}
+
+	// Credits: The engine URL.
+	if (current_data['engine'] && current_data['engine']['url']) {
+		$("#engineid").attr("href", current_data['engine']['url']);
+	} else {
+		$("#engineid").removeAttr("href");
+	}
+
+	// Credits: Engine details.
+	if (current_data['engine'] && current_data['engine']['details']) {
+		$("#enginedetails").text(" (" + current_data['engine']['details'] + ")");
+	} else {
+		$("#enginedetails").text("");
+	}
+
+	// Credits: Move source, possibly with URL.
+	if (current_data['move_source'] && current_data['move_source_url']) {
+		$("#movesource").text("Moves provided by ");
+		var movesource_a = document.createElement("a");
+		movesource_a.setAttribute("href", current_data['move_source_url']);
+		var movesource_text = document.createTextNode(current_data['move_source']);
+		movesource_a.appendChild(movesource_text);
+		var movesource_period = document.createTextNode(".");
+		document.getElementById("movesource").appendChild(movesource_a);
+		document.getElementById("movesource").appendChild(movesource_period);
+	} else if (current_data['move_source']) {
+		$("#movesource").text("Moves provided by " + current_data['move_source'] + ".");
+	} else {
+		$("#movesource").text("");
+	}
+
 	var last_move;
-	if (display_data) {
+	if (displayed_analysis_data) {
 		// Displaying some non-current position, pick out the last move
 		// from the history. This will work even if the fetch failed.
-		last_move = format_move_with_number(
+		last_move = format_halfmove_with_number(
 			current_display_line.pretty_pv[current_display_move],
-			Math.floor((current_display_move + 1) / 2) + 1,
-			(current_display_move % 2 == 1));
+			current_display_move + 1);
 		headline += ' after ' + last_move;
 	} else if (data['position']['last_move'] !== 'none') {
 		last_move = format_move_with_number(
@@ -652,7 +903,7 @@ var update_board = function(current_data, display_data) {
 	// The <title> contains a very brief headline.
 	var title_elems = [];
 	if (data['short_score'] !== undefined && data['short_score'] !== null) {
-		title_elems.push(data['short_score']);
+		title_elems.push(data['short_score'].replace(/^ /, ""));
 	}
 	if (last_move !== null) {
 		title_elems.push(last_move);
@@ -672,10 +923,7 @@ var update_board = function(current_data, display_data) {
 		// We don't have historic analysis for this position, but we
 		// can reconstruct what the last move was by just replaying
 		// from the start.
-		var hiddenboard = new Chess();
-		for (var i = 0; i <= current_display_move; ++i) {
-			hiddenboard.move(current_display_line.pretty_pv[i]);
-		}
+		var hiddenboard = chess_from(null, current_display_line.pretty_pv, current_display_move);
 		var moves = hiddenboard.history({ verbose: true });
 		var last_move = moves.pop();
 		highlight_from = last_move.from;
@@ -683,24 +931,25 @@ var update_board = function(current_data, display_data) {
 	} else {
 		highlight_from = highlight_to = undefined;
 	}
-	update_highlight();
+	update_board_highlight();
 
 	if (data['failed']) {
 		$("#score").text("No analysis for this move");
+		$("#pvtitle").text("PV:");
 		$("#pv").empty();
 		$("#searchstats").html("&nbsp;");
 		$("#refutationlines").empty();
+		$("#whiteclock").empty();
+		$("#blackclock").empty();
 		refutation_lines = [];
 		update_refutation_lines();
 		clear_arrows();
 		update_displayed_line();
+		update_move_highlight();
 		return;
 	}
 
-	// The engine id.
-	if (data['id'] && data['id']['name'] !== null) {
-		$("#engineid").text(data['id']['name']);
-	}
+	update_clock();
 
 	// The score.
 	if (data['score'] !== null) {
@@ -733,6 +982,7 @@ var update_board = function(current_data, display_data) {
 	update_displayed_line();
 
 	// Print the PV.
+	$("#pvtitle").text("PV:");
 	$("#pv").html(add_pv(data['position']['fen'], data['pv_pretty'], data['position']['move_num'], data['position']['toplay']));
 
 	// Update the PV arrow.
@@ -793,6 +1043,69 @@ var update_board = function(current_data, display_data) {
 	toplay = data['position']['toplay'];
 	refutation_lines = data['refutation_lines'];
 	update_refutation_lines();
+
+	// Update the sparkline last, since its size depends on how everything else reflowed.
+	update_sparkline(data);
+}
+
+var update_sparkline = function(data) {
+	if (data && data['score_history']) {
+		var first_move_num = undefined;
+		for (var halfmove_num in data['score_history']) {
+			halfmove_num = parseInt(halfmove_num);
+			if (first_move_num === undefined || halfmove_num < first_move_num) {
+				first_move_num = halfmove_num;
+			}
+		}
+		if (first_move_num !== undefined) {
+			var last_move_num = data['position']['move_num'] * 2 - 3;
+			if (data['position']['toplay'] === 'B') {
+				++last_move_num;
+			}
+
+			// Possibly truncate some moves if we don't have enough width.
+			// FIXME: Sometimes width() for #scorecontainer (and by extent,
+			// #scoresparkcontainer) on Chrome for mobile seems to start off
+			// at something very small, and then suddenly snap back into place.
+			// Figure out why.
+			var max_moves = Math.floor($("#scoresparkcontainer").width() / 5) - 5;
+			if (last_move_num - first_move_num > max_moves) {
+				first_move_num = last_move_num - max_moves;
+			}
+
+			var min_score = -100;
+			var max_score = 100;
+			var last_score = null;
+			var scores = [];
+			for (var halfmove_num = first_move_num; halfmove_num <= last_move_num; ++halfmove_num) {
+				if (data['score_history'][halfmove_num]) {
+					var score = data['score_history'][halfmove_num][0];
+					if (score < min_score) min_score = score;
+					if (score > max_score) max_score = score;
+					last_score = data['score_history'][halfmove_num][0];
+				}
+				scores.push(last_score);
+			}
+			if (data['plot_score']) {
+				scores.push(data['plot_score']);
+			}
+			// FIXME: at some widths, calling sparkline() seems to push
+			// #scorecontainer under the board.
+			$("#scorespark").sparkline(scores, {
+				type: 'bar',
+				zeroColor: 'gray',
+				chartRangeMin: min_score,
+				chartRangeMax: max_score,
+				tooltipFormatter: function(sparkline, options, fields) {
+					return format_tooltip(data, fields[0].offset + first_move_num);
+				}
+			});
+		} else {
+			$("#scorespark").text("");
+		}
+	} else {
+		$("#scorespark").text("");
+	}
 }
 
 /**
@@ -808,6 +1121,133 @@ var update_num_viewers = function(num_viewers) {
 	}
 }
 
+var update_clock = function() {
+	clearTimeout(clock_timer);
+
+	var data = displayed_analysis_data || current_analysis_data;
+	if (data['position']) {
+		var result = data['position']['result'];
+		if (result === '1-0') {
+			$("#whiteclock").text("1");
+			$("#blackclock").text("0");
+			$("#whiteclock").removeClass("running-clock");
+			$("#blackclock").removeClass("running-clock");
+			return;
+		}
+		if (result === '1/2-1/2') {
+			$("#whiteclock").text("1/2");
+			$("#blackclock").text("1/2");
+			$("#whiteclock").removeClass("running-clock");
+			$("#blackclock").removeClass("running-clock");
+			return;
+		}	
+		if (result === '0-1') {
+			$("#whiteclock").text("0");
+			$("#blackclock").text("1");
+			$("#whiteclock").removeClass("running-clock");
+			$("#blackclock").removeClass("running-clock");
+			return;
+		}
+	}
+
+	var white_clock_ms = null;
+	var black_clock_ms = null;
+	var show_seconds = false;
+
+	// Static clocks.
+	if (data['position'] &&
+	    data['position']['white_clock'] &&
+	    data['position']['black_clock']) {
+		white_clock_ms = data['position']['white_clock'] * 1000;
+		black_clock_ms = data['position']['black_clock'] * 1000;
+	}
+
+	// Dynamic clock (only one, obviously).
+	var color;
+	if (data['position']['white_clock_target']) {
+		color = "white";
+		$("#whiteclock").addClass("running-clock");
+		$("#blackclock").removeClass("running-clock");
+	} else if (data['position']['black_clock_target']) {
+		color = "black";
+		$("#whiteclock").removeClass("running-clock");
+		$("#blackclock").addClass("running-clock");
+	} else {
+		$("#whiteclock").removeClass("running-clock");
+		$("#blackclock").removeClass("running-clock");
+	}
+	var remaining_ms;
+	if (color) {
+		var now = new Date().getTime() + client_clock_offset_ms;
+		remaining_ms = data['position'][color + '_clock_target'] * 1000 - now;
+		if (color === "white") {
+			white_clock_ms = remaining_ms;
+		} else {
+			black_clock_ms = remaining_ms;
+		}
+	}
+
+	if (white_clock_ms === null || black_clock_ms === null) {
+		$("#whiteclock").empty();
+		$("#blackclock").empty();
+		return;
+	}
+
+	// If either player has ten minutes or less left, add the second counters.
+	var show_seconds = (white_clock_ms < 60 * 10 * 1000 || black_clock_ms < 60 * 10 * 1000);
+
+	if (color) {
+		// See when the clock will change next, and update right after that.
+		var next_update_ms;
+		if (show_seconds) {
+			next_update_ms = remaining_ms % 1000 + 100;
+		} else {
+			next_update_ms = remaining_ms % 60000 + 100;
+		}
+		clock_timer = setTimeout(update_clock, next_update_ms);
+	}
+
+	$("#whiteclock").text(format_clock(white_clock_ms, show_seconds));
+	$("#blackclock").text(format_clock(black_clock_ms, show_seconds));
+}
+
+/**
+ * @param {Number} remaining_ms
+ * @param {boolean} show_seconds
+ */
+var format_clock = function(remaining_ms, show_seconds) {
+	if (remaining_ms <= 0) {
+		if (show_seconds) {
+			return "00:00:00";
+		} else {
+			return "00:00";
+		}
+	}
+
+	var remaining = Math.floor(remaining_ms / 1000);
+	var seconds = remaining % 60;
+	remaining = (remaining - seconds) / 60;
+	var minutes = remaining % 60;
+	remaining = (remaining - minutes) / 60;
+	var hours = remaining;
+	if (show_seconds) {
+		return format_2d(hours) + ":" + format_2d(minutes) + ":" + format_2d(seconds);
+	} else {
+		return format_2d(hours) + ":" + format_2d(minutes);
+	}
+}
+
+/**
+ * @param {Number} x
+ */
+var format_2d = function(x) {
+	if (x >= 10) {
+		return x;
+	} else {
+		return "0" + x;
+	}
+}
+
 /**
  * @param {string} move
  * @param {Number} move_num
@@ -824,6 +1264,46 @@ var format_move_with_number = function(move, move_num, white_to_play) {
 	return ret;
 }
 
+/**
+ * @param {string} move
+ * @param {Number} halfmove_num
+ */
+var format_halfmove_with_number = function(move, halfmove_num) {
+	return format_move_with_number(
+		move,
+		Math.floor(halfmove_num / 2) + 1,
+		halfmove_num % 2 == 0);
+}
+
+/**
+ * @param {Object} data
+ * @param {Number} halfmove_num
+ */
+var format_tooltip = function(data, halfmove_num) {
+	if (data['score_history'][halfmove_num] ||
+	    halfmove_num === data['position']['pretty_history'].length) {
+		var move;
+		var short_score;
+		if (halfmove_num === data['position']['pretty_history'].length) {
+			move = data['position']['last_move'];
+			short_score = data['short_score'];
+		} else {
+			move = data['position']['pretty_history'][halfmove_num];
+			short_score = data['score_history'][halfmove_num][1];
+		}
+		var move_with_number = format_halfmove_with_number(move, halfmove_num);
+
+		return "After " + move_with_number + ": " + short_score;
+	} else {
+		for (var i = halfmove_num; i --> 0; ) {
+			if (data['score_history'][i]) {
+				var move = data['position']['pretty_history'][i];
+				return "[Analysis kept from " + format_halfmove_with_number(move, i) + "]";
+			}
+		}
+	}
+}
+
 /**
  * @param {boolean} sort_by_score
  */
@@ -857,17 +1337,18 @@ var show_line = function(line_num, move_num) {
 			// TODO: Support exiting to history position if we are in an
 			// analysis line of a history position.
 			displayed_analysis_data = null;
-			update_board(current_analysis_data, displayed_analysis_data);
+			update_board();
 		}
 	} else {
-		current_display_line = display_lines[line_num];
+		current_display_line = jQuery.extend({}, display_lines[line_num]);  // Shallow clone.
 		current_display_move = move_num;
 	}
 	current_display_line_is_history = (line_num == 0);
 
 	update_historic_analysis();
 	update_displayed_line();
-	update_highlight();
+	update_board_highlight();
+	update_move_highlight();
 	redraw_arrows();
 }
 window['show_line'] = show_line;
@@ -878,6 +1359,7 @@ var prev_move = function() {
 	}
 	update_historic_analysis();
 	update_displayed_line();
+	update_move_highlight();
 }
 window['prev_move'] = prev_move;
 
@@ -887,6 +1369,7 @@ var next_move = function() {
 	}
 	update_historic_analysis();
 	update_displayed_line();
+	update_move_highlight();
 }
 window['next_move'] = next_move;
 
@@ -896,36 +1379,101 @@ var update_historic_analysis = function() {
 	}
 	if (current_display_move == current_display_line.pretty_pv.length - 1) {
 		displayed_analysis_data = null;
-		update_board(current_analysis_data, displayed_analysis_data);
+		update_board();
 	}
 
 	// Fetch old analysis for this line if it exists.
-	var hiddenboard = new Chess();
-	for (var i = 0; i <= current_display_move; ++i) {
-		hiddenboard.move(current_display_line.pretty_pv[i]);
-	}
+	var hiddenboard = chess_from(null, current_display_line.pretty_pv, current_display_move);
 	var filename = "/history/move" + (current_display_move + 1) + "-" +
 		hiddenboard.fen().replace(/ /g, '_').replace(/\//g, '-') + ".json";
 
-	$.ajax({
+	current_historic_xhr = $.ajax({
 		url: filename
 	}).done(function(data, textstatus, xhr) {
 		displayed_analysis_data = data;
-		update_board(current_analysis_data, displayed_analysis_data);
-	}).fail(function() {
-		displayed_analysis_data = {'failed': true};
-		update_board(current_analysis_data, displayed_analysis_data);
+		update_board();
+	}).fail(function(jqXHR, textStatus, errorThrown) {
+		if (textStatus === "abort") {
+			// Aborted because we are switching backends. Don't do anything;
+			// we will already have been cleared.
+		} else {
+			displayed_analysis_data = {'failed': true};
+			update_board();
+		}
 	});
 }
 
-var update_displayed_line = function() {
+/**
+ * @param {string} fen
+ */
+var update_imbalance = function(fen) {
+	var hiddenboard = new Chess(fen);
+	var imbalance = {'k': 0, 'q': 0, 'r': 0, 'b': 0, 'n': 0, 'p': 0};
+	for (var row = 0; row < 8; ++row) {
+		for (var col = 0; col < 8; ++col) {
+			var col_text = String.fromCharCode('a1'.charCodeAt(0) + col);
+			var row_text = String.fromCharCode('a1'.charCodeAt(1) + row);
+			var square = col_text + row_text;
+			var contents = hiddenboard.get(square);
+			if (contents !== null) {
+				if (contents.color === 'w') {
+					++imbalance[contents.type];
+				} else {
+					--imbalance[contents.type];
+				}
+			}
+		}
+	}
+	var white_imbalance = '';
+	var black_imbalance = '';
+	for (var piece in imbalance) {
+		for (var i = 0; i < imbalance[piece]; ++i) {
+			white_imbalance += '<img src="img/chesspieces/wikipedia/w' + piece.toUpperCase() + '.png" alt="" style="width: 15px;height: 15px;">';
+		}
+		for (var i = 0; i < -imbalance[piece]; ++i) {
+			black_imbalance += '<img src="img/chesspieces/wikipedia/b' + piece.toUpperCase() + '.png" alt="" style="width: 15px;height: 15px;">';
+		}
+	}
+	$('#whiteimbalance').html(white_imbalance);
+	$('#blackimbalance').html(black_imbalance);
+}
+
+/** Mark the currently selected move in red.
+ */
+var update_move_highlight = function() {
 	if (highlighted_move !== null) {
 		highlighted_move.removeClass('highlight'); 
 	}
+	if (current_display_line) {
+		// See if the current displayed line is identical to any of the ones
+		// we have on screen. (It might not be if e.g. the analysis reloaded
+		// since we started looking.)
+		for (var i = 0; i < display_lines.length; ++i) {
+			var line = display_lines[i];
+			if (current_display_line.start_fen !== line.start_fen) continue;
+			if (current_display_line.pretty_pv.length !== line.pretty_pv.length) continue;
+			var ok = true;
+			for (var j = 0; j < line.pretty_pv.length; ++j) {
+				if (current_display_line.pretty_pv[j] !== line.pretty_pv[j]) {
+					ok = false;
+					break;
+				}
+			}
+			if (ok) {
+				highlighted_move = $("#automove" + i + "-" + current_display_move);
+				highlighted_move.addClass('highlight');
+				break;
+			}
+		}
+	}
+}
+
+var update_displayed_line = function() {
 	if (current_display_line === null) {
 		$("#linenav").hide();
 		$("#linemsg").show();
 		board.position(fen);
+		update_imbalance(fen);
 		return;
 	}
 
@@ -943,16 +1491,12 @@ var update_displayed_line = function() {
 		$("#nextmove").html("<a href=\"javascript:next_move();\">Next</a></span>");
 	}
 
-	var hiddenboard = new Chess();
-	hiddenboard.load(current_display_line.start_fen);
-	for (var i = 0; i <= current_display_move; ++i) {
-		hiddenboard.move(current_display_line.pretty_pv[i]);
-	}
-
-	highlighted_move = $("#automove" + current_display_line.line_number + "-" + current_display_move);
-	highlighted_move.addClass('highlight'); 
-
+	var hiddenboard = chess_from(current_display_line.start_fen, current_display_line.pretty_pv, current_display_move);
+	board_is_animating = true;
+	var old_fen = board.fen();
 	board.position(hiddenboard.fen());
+	if (board.fen() === old_fen) board_is_animating = false;
+	update_imbalance(hiddenboard.fen());
 }
 
 /**
@@ -963,6 +1507,14 @@ var set_sound = function(param_enable_sound) {
 	if (enable_sound) {
 		$("#soundon").html("<strong>On</strong>");
 		$("#soundoff").html("<a href=\"javascript:set_sound(false)\">Off</a>");
+
+		// Seemingly at least Firefox prefers MP3 over Opus; tell it otherwise,
+		// and also preload the file since the user has selected audio.
+		var ding = document.getElementById('ding');
+		if (ding && ding.canPlayType && ding.canPlayType('audio/ogg; codecs="opus"') === 'probably') {
+			ding.src = 'ding.opus';
+			ding.load();
+		}
 	} else {
 		$("#soundon").html("<a href=\"javascript:set_sound(true)\">On</a>");
 		$("#soundoff").html("<strong>Off</strong>");
@@ -973,6 +1525,38 @@ var set_sound = function(param_enable_sound) {
 }
 window['set_sound'] = set_sound;
 
+/**
+ * @param {string} new_backend_url
+ */
+var switch_backend = function(new_backend_url) {
+	// Stop looking at historic data.
+	current_display_line = null;
+	current_display_move = null;
+	displayed_analysis_data = null;
+	if (current_historic_xhr) {
+		current_historic_xhr.abort();
+	}
+
+	// If we already have a backend response going, abort it.
+	if (current_analysis_xhr) {
+		current_analysis_xhr.abort();
+	}
+
+	// Otherwise, we should have a timer going to start a new one.
+	// Kill that, too.
+	if (current_analysis_request_timer) {
+		clearTimeout(current_analysis_request_timer);
+		current_analysis_request_timer = null;
+	}
+
+	// Request an immediate fetch with the new backend.
+	backend_url = new_backend_url;
+	current_analysis_data = null;
+	ims = 0;
+	request_update();
+}
+window['switch_backend'] = switch_backend;
+
 var init = function() {
 	unique = get_unique();
 
@@ -989,12 +1573,15 @@ var init = function() {
 	}
 
 	// Create board.
-	board = new window.ChessBoard('board', 'start');
+	board = new window.ChessBoard('board', {
+		onMoveEnd: function() { board_is_animating = false; }
+	});
 
 	request_update();
 	$(window).resize(function() {
 		board.resize();
-		update_highlight();
+		update_sparkline(displayed_analysis_data || current_analysis_data);
+		update_board_highlight();
 		redraw_arrows();
 	});
 	$(window).keyup(function(event) {
@@ -1004,6 +1591,7 @@ var init = function() {
 			prev_move();
 		}
 	});
+	window.addEventListener('hashchange', possibly_switch_game_from_hash, false);
 };
 $(document).ready(init);