/// <summary>
/// Redirects to the mobile view if on a supported device
/// </summary>
[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, Inherited = true, AllowMultiple = false)]
public class MobileRedirectAttribute : AuthorizeAttribute
{
    private string _clientFragment;

    /// <summary>
    /// Default Constructor
    /// </summary>
    public MobileRedirectAttribute()
    {
        _clientFragment = string.Empty;
    }

    /// <summary>
    /// Constructor that takes an argument
    /// </summary>
    /// <param name="clientUrl">The url fragment we should append to the url</param>
    public MobileRedirectAttribute(string clientFragment)
    {
        _clientFragment = clientFragment;
    }

    /// <summary>
    /// Tests if this request originates from a supported mobile device
    /// and redirects as appropriate
    /// </summary>
    /// <param name="ctx">The action execution context</param>
    public override void OnAuthorization(AuthorizationContext ctx)
    {
        if (ctx.HttpContext.Request.Browser.IsMobileDevice)
        {
            // parse the fragment with request parameters
            string fragment = ParseClientFragment(ctx);

            // construct the redirect url
            UrlHelper urlHelper = new UrlHelper(ctx.RequestContext);
            string url = string.Format("{0}#{1}", urlHelper.Action("Index", "Mobile"), fragment);

            // return redirect result to prevent action execution
            ctx.Result = new RedirectResult(url);
        }
    }

    /// <summary>
    /// Parses the client fragment and replaces :[token] with the request parameter
    /// </summary>
    /// <param name="ctx">The controller context</param>
    /// <returns>The parsed fragment</returns>
    private string ParseClientFragment(ControllerContext ctx)
    {
        string parsedFragment = _clientFragment ?? string.Empty;

        if (!string.IsNullOrEmpty(parsedFragment))
        {
            NameValueCollection @params = ctx.HttpContext.Request.Params;
            MatchCollection matches = Regex.Matches(_clientFragment, ":[a-zA-Z]+");
            RouteData routeData = RouteTable.Routes.GetRouteData(ctx.HttpContext);

            // check each token and replace with param or route values
            foreach (Match match in matches)
            {
                string token = match.Value.TrimStart(':');
                string value = @params[token];

                // if we haven;t got a parameter here we must check the route values
                if (string.IsNullOrEmpty(value) && routeData.Values.ContainsKey(token))
                {
                    value = routeData.Values[token] as string;
                }

                // perform the replace
                parsedFragment = parsedFragment.Replace(match.Value, value);
            }
        }

        return parsedFragment;
    }
}