main.js

(function($) {
	window.location.host.match(/futurelearn\.com/) && (function() {
		function file_get_contents(url, callback) {
			var xhr = new XMLHttpRequest();
			xhr.onreadystatechange = function() {
				if(xhr.readyState == 4 && xhr.status == 200) {
					var h = document.createElement("html");
					h.innerHTML = xhr.responseText;
					callback(h);
				}
			}
			xhr.open("GET", url, true);
			xhr.send(null);
		}
		file_get_contents(location.href, function(d) {
			document.querySelector(".related-files").innerHTML += [].map.call(d.querySelectorAll("video div[data-kind='subtitles']"), function(sub) {
				return '<li class="media media-small media-sectioned">'+
		          '<div class="media_centered_container">'+
		            '<div aria-hidden="true" class="media_icon icon" data-icon="x"></div>'+
		            '<div class="media_body">'+
		              '<div class="header header-double">'+
		                '<h5 class="headline headline-primary">'+
		                  '<a class="futerlearnDown" href="'+sub.getAttribute('data-src')+'">'+sub.getAttribute('data-label')+' Subtitle Download</a>'+
		                  '<span class="headline headline-secondary" style="margin-left:5px;">srt</span>'+
		                '</h5></div></div></div></li>';
			}).join('');
		})
	}());
	window.location.host == "class.coursera.org" && $('.course-item-list-section-list li').map(function(){return $('a:last', $(this)).get(0)}).each(function(i,item){
		var chinese = this.href.replace('download.mp4?lecture_id', 'subtitles?q');
		chinese += '_zh&format=srt';
		$.ajax({type:"HEAD", url:chinese, complete:function(xhr,data) {
			if(xhr.status != 200) {
				chinese = chinese.replace('_zh&', '_zh-cn&');
				$.ajax({type:"HEAD", url:chinese, complete:function(xhr,data) {
					if(xhr.status != 200) return false;
					$(item).before('<a target="_new" href="'+chinese+'" title="中文字幕下载">中</a>');
				}})
			} else $(item).before('<a target="_new" href="'+chinese+'" title="中文字幕下载">中</a>');
		}})
	})

	/** edX **/
	if(!$('li[data-index]')) return false;
	
	function fake_click(obj) {
	    var ev = document.createEvent("MouseEvents");
	    ev.initMouseEvent(
	        "click", true, false, window, 0, 0, 0, 0, 0
	        , false, false, false, false, 0, null
	        );
	    obj.dispatchEvent(ev);
	}

	function export_raw(name, data) {
	    var urlObject = window.URL || window.webkitURL || window;

	    var export_blob = new Blob([data]);

	    var save_link = document.createElementNS("http://www.w3.org/1999/xhtml", "a")
	    save_link.href = urlObject.createObjectURL(export_blob);
	    save_link.download = name;
	    fake_click(save_link);
	}

	function parseTime(time) {
		var min = Math.floor(time / 60000);
		var hour = Math.floor(time / 3600000);
		var second = time / 1000 - hour * 3600 - min * 60;
		min = String(min).length < 2 ? '0'+min : String(min);
		hour = String(hour).length < 2 ? '0'+hour : String(hour);
		second = second.toFixed(3);
		second = String(second).length<6 ? '0'+second : String(second);
		second = second.split('.').join(',');
		return hour+':'+min+':'+second; 
	}

	var l = '<a href="#" id="Subtitle_download" style="font-size:0.7em;">Subtitle download</a>';
	$('section h2') && $('section h2').last().append(l);
	$(document).on('click', '#Subtitle_download', function() {
		if($('li[data-index]').length == 0) {
			alert('Apologies, but no subtitles were found.');
			return false;
		}
		
		subtitles = [];		
		$('li[data-index]').each(function() {
			var start = parseTime($(this).attr('data-start'));
			var end = parseTime( $(this).next().attr('data-start') ? $(this).next().attr('data-start') : +$(this).attr('data-start')+1000 );
			subtitles.push($(this).attr('data-index'));
			subtitles.push(start+' --> '+end);
			subtitles.push($(this).text());
			subtitles.push('');
		})
		export_raw($.trim($('ul li.active p').text().split(', current section')[0])+'.srt', subtitles.join('\r\n'));
	}) 
})(jQuery);