Mostly-Harmless/background.html

<script>
	var db = openDatabase('mhdb', '1.0', 'Mostly Harmless Database', 5 * 1024 * 1024);
	var cacheTime;
	var over18;
	var commentsMatchPattern = /https?:\/\/www\.reddit\.com(\/r\/(.+?))?\/comments\/(.+?)\/.*/;
	init();
	
	function init() {
		setBadgeDefaults();
		chrome.tabs.onUpdated.addListener(listenToTabs);
		if(window.localStorage.getItem('installed') !== 'true') {
			installDefaults();
		}
		db.transaction(function(tx){
			// Load preferences
			tx.executeSql('SELECT * FROM prefs WHERE pref=?', ['cacheTime'], function(tx, results) {
				cacheTime = results.rows.item(0).choice;
			});
			tx.executeSql('SELECT * FROM prefs WHERE pref=?', ['over18'], function(tx, results) {
				over18 = results.rows.item(0).choice;
			});
			
			// Clear cache and post data
			tx.executeSql('DELETE FROM cache');
			tx.executeSql('DELETE FROM posts');
		});
	}
	
	function installDefaults(tx) {
		window.localStorage.setItem('installed','true');
		db.transaction(function(tx) {
			tx.executeSql('CREATE TABLE IF NOT EXISTS cache (pageUrl unique, cacheTime, howManyPosts)');
			tx.executeSql('CREATE TABLE IF NOT EXISTS posts (id unique, name, likes, domain, subreddit, author, score, over_18, hidden, thumbnail, downs, permalink, created_utc, url, title, num_comments, ups, modhash)')
			tx.executeSql('CREATE TABLE IF NOT EXISTS prefs (pref unique, choice)');
			tx.executeSql('INSERT INTO prefs (pref, choice) VALUES (?, ?)', ['cacheTime','1']);
			tx.executeSql('INSERT INTO prefs (pref, choice) VALUES (?, ?)', ['over18','false']);
		});
	}
	
	function setBadgeDefaults(tabId) {
		chrome.browserAction.setBadgeBackgroundColor({
			color: [192,192,192,255] //r,g,b,a
		});
		chrome.browserAction.onClicked.removeListener(submitToReddit);
		if(tabId) {
			chrome.browserAction.setBadgeText({
				text: '?',
				tabId: tabId
			});
			chrome.browserAction.setTitle({
				title: 'Refresh the page to load data.',
				tabId: tabId
			});
		} else {
			chrome.browserAction.setBadgeText({
				text: '?',
			});
			chrome.browserAction.setTitle({
				title: 'Refresh the page to load data.'
			});
		}
	}
	
	function listenToTabs(tabId,changeInfo,tab){
		if(changeInfo.status === 'loading') {
			//If the user is at /comments instead of /r/subreddit/comments, redirect them.
			if(commentsMatchPattern.test(tab.url) && !(/https?:\/\/www\.reddit\.com\/r\/(.+?)\/comments\/(.+?)\/.*/.test(tab.url))) {
				chrome.tabs.update(tabId,{url:'http://redd.it/' + tab.url.match(commentsMatchPattern)[3]});	
			} else {
				grabData(tab.url,tabId);
			}
		}
	}
	
	function grabData(url,tabId) {
		// If the URL hasn't been cached recently, fetch it from the API.
		db.transaction(function(tx) {
			tx.executeSql('SELECT * FROM cache WHERE pageUrl=?', [url], function(tx, results) {
				var cache = results.rows;
				var isCommentsPage = commentsMatchPattern.test(url);
				if(cache.length === 0 || -(cache.item(0).cacheTime - epoch()) > 60  * cacheTime ) { // cacheTime in minutes
					console.log('Loading from reddit api...');
					var reqUrl = new String();
					if(isCommentsPage) {
						var matches = url.match(commentsMatchPattern);
						reqUrl = 'http://www.reddit.com/by_id/t3_' + matches[3] + '.json';
					} else {
						reqUrl = 'http://www.reddit.com/api/info.json?url=' + encodeURI(url);
					}
					var api = new XMLHttpRequest();
					api.open('GET',reqUrl,false);
					api.send(null);
					if(api.status !== 200) {
						console.error('Error loading API.\nURL: ' + reqUrl + '\nStatus: ' + api.status);
						console.log(api);
						setBadgeDefaults(tabId);
					}
					api.onload = cacheData(JSON.parse(api.responseText),url,tabId,isCommentsPage);
				} else {
					console.log('Loading from cache...');
					preparePopup(url,tabId);
				}
			});
		});
	}
	
	function epoch() {
		return Math.floor(new Date().getTime()/1000);
	}
	
	function cacheData(response,pageUrl,tabId,isCommentsPage) {
		// add response to cache to reduce API calls
		if(response.data.children.length === 0) {
			db.transaction(function(tx) {
				tx.executeSql('INSERT OR REPLACE INTO cache (pageUrl, cacheTime, howManyPosts) VALUES (?, ?, ?)',[pageUrl, epoch(), '0',]);
			});
		} else {
			db.transaction(function(tx) {
				for(var i = 0; i < response.data.children.length; i++) {
					var data = response.data.children[i].data;
					var insertUrl = isCommentsPage ? 'http://www.reddit.com' + data.permalink : data.url;
					var insertNum = isCommentsPage ? '...' : response.data.children.length;
					tx.executeSql(
						'INSERT OR REPLACE INTO posts' +
						'(id, name, likes, domain, subreddit, author, score, over_18, hidden, thumbnail, downs, permalink, created_utc, url, title, num_comments, ups, modhash)' +
						'VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)',
						[data.id, data.name, data.likes, data.domain, data.subreddit, data.author, data.score, data.over_18, data.hidden, data.thumbnail, data.downs, data.permalink, data.created_utc, insertUrl, data.title, data.num_comments, data.ups, response.data.modhash],
						function(tx) {
							tx.executeSql('INSERT OR REPLACE INTO cache (pageUrl, cacheTime, howManyPosts) VALUES (?, ?, ?)',[pageUrl, epoch(), insertNum]);
						});
				}
			});
		}
		preparePopup(pageUrl,tabId);
	}
	
	function preparePopup(url,tabId) {
		// counts submissions and prepare the browserAction button appropriately
		var numberOfSubmissions;
		db.transaction(function(tx){
			tx.executeSql('SELECT * FROM cache WHERE pageUrl=?', [url], function(tx, results) {
				numberOfSubmissions = results.rows.item(0).howManyPosts;
				if(numberOfSubmissions > 0) {
					chrome.browserAction.setTitle({
						title: 'This page has been submitted to reddit ' + numberOfSubmissions + ' times.',
						tabId: tabId
					});
					chrome.browserAction.setBadgeText({
						text: numberOfSubmissions.toString(),
						tabId: tabId
					});
					chrome.browserAction.setPopup({
						popup: 'popup.html',
						tabId: tabId
					});
					chrome.browserAction.setBadgeBackgroundColor({
						color: [255,69,0,255], //r,g,b,a,
						tabId: tabId
					});
					chrome.browserAction.onClicked.removeListener(submitToReddit);
				} else if(numberOfSubmissions === '...') {
					chrome.browserAction.setTitle({
						title: 'You are currently viewing the comments for this page.',
						tabId: tabId
					});
					chrome.browserAction.setBadgeText({
						text: numberOfSubmissions,
						tabId: tabId
					});
					chrome.browserAction.setPopup({
						popup: 'popup.html',
						tabId: tabId
					});
					chrome.browserAction.setBadgeBackgroundColor({
						color: [255,69,0,255], //r,g,b,a,
						tabId: tabId
					});
					chrome.browserAction.onClicked.removeListener(submitToReddit);
				} else {
					chrome.browserAction.setTitle({
						title: 'Submit this page to reddit',
						tabId: tabId
					});
					chrome.browserAction.setBadgeText({
						text: '',
						tabId: tabId
					});
					chrome.browserAction.setPopup({
						popup: '',
						tabId: tabId
					});
					chrome.browserAction.onClicked.removeListener(submitToReddit);
					chrome.browserAction.onClicked.addListener(submitToReddit);
				}
			});
		});
	}
	
	function submitToReddit(tab){
		chrome.tabs.create({
			url: 'http://www.reddit.com/submit?url=' + encodeURI(tab.url)
		});
	}
</script>