/**
 * @param configuration object containing three properties:
 *			- mobile_prefix			: prefix appended to the hostname (such as "m" to redirect to "m.domain.com")
 *			- mobile_url			: mobile url to use for the redirection (such as "mobile.whatever.com" to redirect to "whatever.com" )
 *			- mobile_scheme			: url scheme (http/https) of the mobile site domain
 *			- cookie_hours			: number of hours the cookie needs to exist after redirection to desktop site
 *			- noredirection_param	: parameter to pass in the querystring of the URL to avoid the redirection (the value must be equal to "true").
 *									  It's also the name of the item in the localStorage (or cookie name) to avoid mobile
 *									  redirection. Default value is "noredirection". Eg: http://domain.com?noredirection=true
 *			- tablet_redirection	: boolean value that enables/disables(default) the redirection for tablet such as iPad, Samsung Galaxy Tab, Kindle or Motorola Xoom. - Default:false
 *									  Default Url for redirection will be the same as the one for mobile devices.
 *			- tablet_url			: url to use for the redirection in case user is using a tablet to access the site
 *			- keep_path				: boolean to determine if the destination url needs to keep the path from the original url
 *			- keep_query			: boolean to determine if the destination url needs to keep the querystring from the original url
 *			- beforeredirection_callback : callback launched before the redirection happens
 */
redirection_mobile = function( configuration )
{
	// Helper function for adding time to the current date
	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;
	};

	// Helper function for getting a value from a parameter in the querystring
	var getQueryValue = function( param )
	{
		if ( !param )
		{
			return;
		}

		var querystring = document.location.search,
			queryStringArray = querystring && querystring.substring(1).split("&"),
			i = 0,
			length = queryStringArray.length;

		for (; i < length; i++)
		{
			var token = queryStringArray[i],
				firstPart = token && token.substring(0, token.indexOf("="));
			if ( firstPart === param )
			{
				return token.substring(token.indexOf("=") + 1, token.length);
			}
		}
	};
				
	// Retrieve the User Agent of the browser
	var agent = navigator.userAgent.toLowerCase(),
	
		// Constants
		FALSE = "false",
		TRUE = "true",

		// configuration object
		config = configuration || {},
	
		// parameter to pass in the URL to avoid the redirection
		redirection_param = config.noredirection_param || "noredirection",
		
		// prefix appended to the hostname
		mobile_prefix = config.mobile_prefix || "m",
		
		// new url for the mobile site domain 
		mobile_url = config.mobile_url,
		
		// protocol for the mobile site domain 
		mobile_protocol = config.mobile_scheme ?
			config.mobile_scheme + ":" :
				document.location.protocol,
		
		// URL host of incoming request
		host = document.location.host,

		// value for the parameter passed in the URL to avoid the redirection
		queryValue = getQueryValue( redirection_param ),

		// Compose the mobile hostname considering "mobile_url" or "mobile_prefix" + hostname
		mobile_host = mobile_url ||
			(mobile_prefix + "." + 
				(!!host.match(/^www\./i) ?
					host.substring(4) : 
						host)),

		// Expiry hours for cookie
		cookie_hours = config.cookie_hours || 1,
		
		// Parameters to determine if the pathname and the querystring need to be kept
		keep_path = config.keep_path || false,
		keep_query = config.keep_query || false,

		// new url for the tablet site domain 
		tablet_host = config.tablet_url || mobile_host,
		
		// Check if the UA is a mobile one (iphone, ipod, android, blackberry)
		isUAMobile =!!(agent.match(/(iPhone|iPod|blackberry|android 0.5|htc|lg|midp|mmp|mobile|nokia|opera mini|palm|pocket|psp|sgh|smartphone|symbian|treo mini|Playstation Portable|SonyEricsson|Samsung|MobileExplorer|PalmSource|Benq|Windows Phone|Windows Mobile|IEMobile|Windows CE|Nintendo Wii)/i));


	// Check if the referrer was a mobile page (probably the user clicked "Go to full site") or in the 
	// querystring there is a parameter to avoid the redirection such as "?mobile_redirect=false"
	// (in that case we need to set a variable in the sessionStorage or in the cookie)
	if ( document.referrer.indexOf( mobile_host ) >= 0 || queryValue === TRUE )
	{
		if ( window.sessionStorage )
		{
			window.sessionStorage.setItem( redirection_param, TRUE );
		}
		else
		{
			document.cookie = redirection_param + "=" + TRUE + ";expires="+
				addTimeToDate( 3600 * 1000 * cookie_hours ).toUTCString();
		}
	}
	
	// Check if the sessionStorage contain the parameter
	var isSessionStorage = ( window.sessionStorage ) ? 
			( window.sessionStorage.getItem( redirection_param ) === TRUE) :
				false,

		// Check if the Cookie has been set up
		isCookieSet = document.cookie ? 
			( document.cookie.indexOf( redirection_param ) >= 0 ) :
				false;
	
	// Check if the device is a Tablet such as iPad, Samsung Tab, Motorola Xoom or Amazon Kindle
	if ( !!( agent.match( /(iPad|SCH-I800|xoom|kindle)/i ) ) )
	{
		// Check if the redirection needs to happen for iPad
		var isUATablet = ( config.tablet_redirection === TRUE || !!config.tablet_url ) ? true : false;
		isUAMobile = false;
	}

	// Check that User Agent is mobile, cookie is not set or value in the sessionStorage not present
	if ( ( isUATablet || isUAMobile) && !( isCookieSet || isSessionStorage ) )
	{
		// Callback call
		if ( config.beforeredirection_callback )
		{
			if ( !config.beforeredirection_callback.call( this ) )
			{
				return;
			}
		}
		
		var path_query = "";
		
		if ( keep_path )
		{ 
			path_query += document.location.pathname;
		}
		
		if ( keep_query )
		{
			path_query += document.location.search;
		}
		
		if ( isUATablet )
		{
			document.location.href = mobile_protocol + "//" + tablet_host + path_query;
		}
		else if ( isUAMobile )
		{
			document.location.href = mobile_protocol + "//" + mobile_host + path_query;
		}
	}
};