index.js

/**
 * Get the current URL.
 *
 * @param {function(string)} callback - called when the URL of the current tab
 * is found.
 */
function getCurrentTabUrl(callback) {
	var queryInfo = {
		active: true,
		currentWindow: true
	};

	chrome.tabs.query(queryInfo, function(tabs) {
		var tab = tabs[0];
		var url = tab.url;
		console.assert(typeof url == 'string', 'tab.url should be a string');

		callback(url);
	});
}

// Redirect to mirror url
function takeMeTo(url) {
	let updateProperties = {
			url: "https://" + url
	}
	chrome.tabs.update(updateProperties=updateProperties)
}

// Wait for the DOM to load before doing anything
jQuery(document).ready(function() {
	// Check if there's a mirror for the current URL. If so, display the message
	// about it and the button to redirect to a random mirror (if there's more than
	// one).
	getCurrentTabUrl(function(url) {
		chrome.storage.local.get("sites_list", function(stored_sites){
			sites = stored_sites.sites_list.sites
			// Grab the domain part of the URL
			let domain = url.match(/:\/\/(www\.)?([^\/]+)\//).slice(-1)[0]
			console.log(domain);
			console.log(sites);
			let match = sites.find(function(item) {
				return (domain === item.main_domain && item.available_mirrors.length > 0);
			});
			if(typeof match !== 'undefined') {
				let proxies = match.available_mirrors;
				// Offer the user to redirect them to a mirror
				$("#mirror").css("display", "block")
				$("#nomirror").css("display", "none")
				$("#mirror button").on("click", function() {
					takeMeTo(proxies[Math.floor(Math.random()*proxies.length)])
				})
			}
			else {
				// Tell the user there's no mirror available
				$("#mirror").css("display", "none")
				$("#nomirror").css("display", "block")
			}
		})
	})
})