/BlogEngine/DotNetSlave.BusinessLogic/Web/HttpModules/WwwSubDomainModule.cs

namespace BlogEngine.Core.Web.HttpModules

{

    using System;

    using System.Text.RegularExpressions;

    using System.Web;



    /// <summary>

    /// Removes or adds the www subdomain from all requests

    ///     and makes a permanent redirection to the new location.

    /// </summary>

    public class WwwSubDomainModule : IHttpModule

    {

        #region Constants and Fields



        /// <summary>

        /// The link regex.

        /// </summary>

        private static readonly Regex LinkRegex = new Regex(

            "(http|https)://www\\.", RegexOptions.IgnoreCase | RegexOptions.Compiled);



        #endregion



        #region Implemented Interfaces



        #region IHttpModule



        /// <summary>

        /// Disposes of the resources (other than memory) used by the module that implements <see cref="T:System.Web.IHttpModule"/>.

        /// </summary>

        public void Dispose()

        {

            // Nothing to dispose

        }



        /// <summary>

        /// Initializes a module and prepares it to handle requests.

        /// </summary>

        /// <param name="context">An <see cref="T:System.Web.HttpApplication"/> that provides access to the methods, properties, and events common to all application objects within an ASP.NET application</param>

        public void Init(HttpApplication context)

        {

            context.BeginRequest += ContextBeginRequest;

        }



        #endregion



        #endregion



        #region Methods



        /// <summary>

        /// Adds the www subdomain to the request and redirects.

        /// </summary>

        /// <param name="context">

        /// The context.

        /// </param>

        private static void AddWww(HttpContext context)

        {

            var url = context.Request.Url.ToString().Replace("://", "://www.");

            PermanentRedirect(url, context);

        }



        /// <summary>

        /// Sends permanent redirection headers (301)

        /// </summary>

        /// <param name="url">

        /// The url to redirect to.

        /// </param>

        /// <param name="context">

        /// The HTTP context.

        /// </param>

        private static void PermanentRedirect(string url, HttpContext context)

        {

            if (url.EndsWith("default.aspx", StringComparison.OrdinalIgnoreCase))

            {

                url = url.ToLowerInvariant().Replace("default.aspx", string.Empty);

            }



            context.Response.Clear();

            context.Response.StatusCode = 301;

            context.Response.AppendHeader("location", url);

            context.Response.End();

        }



        /// <summary>

        /// Removes the www subdomain from the request and redirects.

        /// </summary>

        /// <param name="context">

        /// The context.

        /// </param>

        private static void RemoveWww(HttpContext context)

        {

            var url = context.Request.Url.ToString();

            if (!LinkRegex.IsMatch(url))

            {

                return;

            }



            url = LinkRegex.Replace(url, "$1://");

            PermanentRedirect(url, context);

        }



        /// <summary>

        /// Handles the BeginRequest event of the context control.

        /// </summary>

        /// <param name="sender">The source of the event.</param>

        /// <param name="e">The <see cref="System.EventArgs"/> instance containing the event data.</param>

        private static void ContextBeginRequest(object sender, EventArgs e)

        {

            // Clear the InstanceIdOverride to ensure any values are not

            // carried over from previous times this thread from the thread

            // pool was used.

            //

            // This should be done at the beginning of each HTTP request as

            // early as possible.  It is being done here because in the

            // list of HTTP modules defined in the web.config file, this

            // module (WwwSubdomainModule) is the first defined one so will

            // fire before any other modules.

            Blog.InstanceIdOverride = Guid.Empty;



            if (BlogSettings.Instance.HandleWwwSubdomain == "ignore" ||

                string.IsNullOrEmpty(BlogSettings.Instance.HandleWwwSubdomain))

            {

                return;

            }



            var context = ((HttpApplication)sender).Context;

            if (context.Request.HttpMethod != "GET" || context.Request.RawUrl.Contains("/admin/") ||

                context.Request.IsLocal)

            {

                return;

            }



            if (context.Request.PhysicalPath.EndsWith(".aspx", StringComparison.OrdinalIgnoreCase))

            {

                var url = context.Request.Url.ToString();



                if (url.Contains("://www.") && BlogSettings.Instance.HandleWwwSubdomain == "remove")

                {

                    RemoveWww(context);

                }



                if (!url.Contains("://www.") && BlogSettings.Instance.HandleWwwSubdomain == "add")

                {

                    AddWww(context);

                }

            }

        }



        #endregion

    }

}