NancyFx Forms Auth Sliding Window

Sliding.cs

/*
* In my project I added the GUID to my implementation of IUserIdentity
* so I had access to it later by a simple cast.  In Nancy you'd just want
* to fetch it the same way it's already done in the Before hook.
*
* Also note, I'm using my company's style guide, not Nancy's.
*/


// This is a Drop in replacement for the after hook used by FormsAuth right now.
private static Action<NancyContext> GetRedirectOrExtendWindowHook(FormsAuthenticationConfiguration configuration) {
    if (configuration == null) {
        throw new ArgumentNullException("configuration");
    }
    return context => {
        if (context.Response.StatusCode == HttpStatusCode.Unauthorized) {
            // I felt like it was common enough to want 401s to be passed unharmed to Ajax calls that I
            // didn't even add configuratoin for this, it'd be simple enough to change this like so:
            // if (!configuration.RedirectAjax && context.IsAjaxRequest()) {
            if (context.IsAjaxRequest()) {
                return;
            }
            context.Response = context.GetRedirect(RedirectUrl(configuration, context));
        }
        // Note this could be added to the configuration:
        // else if (configuration.SlidingExpiry && LoggedIn(context)) {
        else if (LoggedIn(context)) {
            var cookie = context.Response.Cookies.FirstOrDefault(IsAuthCookie);
            if (cookie == null) {
                // Note this should be replaced by the more correct way of extracting the
                // User Identifier from the cookie.  I used this because directly copying
                // the code from Forms Auth for extracting the GUID was failing for me.
                var guid = ((UserWithId) context.CurrentUser).Id;
                // Note: the next two lines should be replaced directly by 'BuildLoginCookie'
                // which is private
                var resp = FormsAuthentication.UserLoggedInResponse(guid);
                cookie = resp.Cookies.Single(IsAuthCookie);
                context.Response.Cookies.Add(cookie);
            }
            // Note: number of minutes should be configured, not hard coded
            cookie.Expires = DateTime.UtcNow.AddMinutes(30);
        }
    };
}

private static bool IsAuthCookie(INancyCookie c) {
    return c.Name == FormsAuthentication.FormsAuthenticationCookieName;
}

private static bool LoggedIn(NancyContext ctx) {
    return ctx.CurrentUser != null // Already Logged In
        || ctx.Response.Cookies.Any(IsAuthCookie); // Logged In as a result of a fresh Login.
}

// This is a duplicate of code that's already in FormsAuth
private static string RedirectUrl(FormsAuthenticationConfiguration configuration, NancyContext context) {
    var key = string.IsNullOrWhiteSpace(configuration.RedirectQuerystringKey) ? "returnUrl" : configuration.RedirectQuerystringKey;
    var val = context.ToFullPath("~" + context.Request.Path + HttpUtility.UrlEncode(context.Request.Url.Query));
    return string.Format("{0}?{1}={2}", configuration.RedirectUrl, key, val);
}