/*!
	 * JS Redirection Mobile
	 *
	 * Developed by
	 * Sebastiano Armeli-Battana (@sebarmeli) - http://sebarmeli.com
	 */	

	/*
	 * This script will cover a basic scenario of full JS mobile redirection.
	 * The user will be redirected to the mobile version of the site (home page)
	 * if it's trying to access the site from a mobile device. This check is
	 * mainly done checking the User-Agent string. 
	 * The mobile URL will be obtained appending a prefix (default is "m") to 
	 * the hostname of the current URL. It's used a naked domain to avoid conflict with
	 * www.
	 * 
	 * In some cases the user needs to be redirected to the Desktop version of the site 
	 * from a mobile device. To achieve that, a possible solution is checking the "referrer".
	 * In that case a new key/value in sessionStorage (for modern browsers) 
	 * will be set and until the user doesn't close browser window or tab it will access
	 * to the desktop version from a mobile device. There is a fallback for old browsers that
	 * don’t support sessionStorage, and it will use a cookie. The cookie that makes the access 
	 * to the desktop version from a mobile device possible will expiry in one hour (default value)
	 * or you configure the expiry time.
	 * 
	 * To use this function, you need to call it as SA.redirection_mobile(config);
	 * E.g. SA.redirection_mobile ({param:"isDefault", mobile_prefix : "mobile", cookie_hours : "2" })
	 *
	 * @author Sebastiano Armeli-Battana
	 * @version 0.3 
	 * 
	 */
	
	/*globals window,document, navigator, SA */
	if (!window.SA) {window.SA = {};}

    /*
	 * @param config containing two fields: param (parameter to be passed to avoid
	 *             mobile redirection), mobile_prefix (prefix appended to the 
	 *             hostname), cookie_hours (number of hours cookie needs to exist after
	 *			redirection to desktop site)
	*/
	SA.redirection_mobile = function(config) {
		
		// Helper function
		var addTimeToDate = function(msec) {

			// Get the current date
			var exdate = new Date();

			// Add time to the date
			exdate.setTime(exdate.getTime() + msec);

			//Return the new Date
			return exdate;

		};
					
		// Retrieve the User Agent of the browser
		var agent = navigator.userAgent.toLowerCase(),
		
			// param value or default value
			param = config.param || "isStandardSite",
			
			// Constant
			TRUE = "true",
		
			// "m" is the default mobile hostname prefix 
			mobile_prefix = config.mobile_prefix || "m",
			
			// URL host of incoming request
		    host = document.location.host,
		
			// Compose the mobile hostname
			mobile_host = mobile_prefix + "." + 
							(!!host.match(/^www\./i) ?
								host.substring(4) : 
									host),
			
			// Expiry hours for cookie
			cookie_hours = config.cookie_hours || 1,
		
			// Check if the UA is a mobile one (iphone, ipod, ipad, android, blackberry)
			isUAMobile = !!(agent.match(/iPhone/i) || agent.match(/iPod/i) || 
			              agent.match(/blackberry/i) ||  agent.match(/symbian/i) ||
			              agent.match(/android/i));
		
		// Check if the referrer was a mobile page of the site
		// (in that case we need to set a variable in the sessionStorage or in the cookie)
		if (document.referrer.indexOf(mobile_host) >= 0) {
			if (window.sessionStorage) {
				window.sessionStorage.setItem(param, TRUE);
			} else {
				document.cookie = param + "=" + TRUE + ";expires="+
													addTimeToDate(3600*1000*cookie_hours).toUTCString();
			}
		}
		
		// Check if the sessionStorage contain the parameter
		var isSessionStorage = (window.sessionStorage) ? 
								(window.sessionStorage.getItem(param) === TRUE) :
								 false,
			
			// Check if the Cookie has been set up
			isCookieSet = document.cookie ? 
							(document.cookie.indexOf(param) >= 0) :
								false;
								
		// Check that User Agent is mobile, cookie is not set or value in the sessionStorage not present
		if (isUAMobile && !(isCookieSet || isSessionStorage)) {
		   document.location.href = document.location.protocol + "//" + mobile_host;
		} 
	};