using System;
using System.Web;
using System.IO;

namespace AbstractUrl
{
	/// <summary>
	/// Implements a simple Abstract URL resolver.
	/// By aegrumet@alum.mit.edu on 2003-06-27.
	/// 
	/// To install this code, you must compile it to the bin directory in your
	/// web site root or virtual directory.
	/// 
	/// You must also add an entry to the httpModules section of the web.config file
	/// in your web site root or virtual directory.  If the file does not exist,
	/// you can create one containing the following:
	/// 
	/// <configuration>
	///   <system.web>
	///     <httpModules>
	///        <add name="AbstractUrlModule" type="AbstractUrl.AbstractUrlModule, AbstractUrl" />
	///     </httpModules>
	///   </system.web>
	/// </configuration>
	/// 
	/// Here we assume that your compiled code resides in bin\AbstractUrl.dll.
	/// 
	/// Finally, you must modify the IIS configuration for your web site or virtual
	/// directory, so that the ASP.NET engine will be invoked for extensionless
	/// requests.  In the Internet Information Services manager, right-click on
	/// the site or virtual directory and select Properties.  Navigate to the
	/// Home Directory tab (for a web site) or the Virtual Directory tab (for a
	/// virtual directory) and click Configuration...
	/// 
	/// IIS6: insert a wildcard application map that points to
	/// C:\WINDOWS\Microsoft.NET\Framework\vX.Y.Z\aspnet_isapi.dll. 
	/// Make sure that "verify that file exists" is unchecked.
	/// 
	/// IIS5: add an application mapping.  In the add/edit application extension
	/// mapping window, enter
	/// C:\WINDOWS\Microsoft.NET\Framework\vX.Y.Z\aspnet_isapi.dll
	/// for the Executable.  Hint: if you're using the Browse... window you want
	/// "Files of type" to be set to "Dynamic Link libraries (*.dll)".
	/// Enter .* ("dot star") for the Extension.
	/// VERY IMPORTANT: Due to a bug in IIS, the OK button will probably be greyed out.
	/// Click your mouse in the white text area for the Executable field.  This should
	/// cause the OK button to become clickable.  Make sure that "Check that file exists"
	/// is unchecked.  Click OK.
	/// 
	/// </summary>
	public class AbstractUrlModule : IHttpModule
	{
		/// <summary>
		/// This is our hook into the HttpApplication event model.
		/// Here we register our OnBeginRequest event handler.
		/// </summary>
		/// <param name="httpApp">The containing web application object.</param>
		public void Init(HttpApplication httpApp) 
		{
			httpApp.BeginRequest += new EventHandler(this.OnBeginRequest);   
		}

		/// <summary>
		/// Disposes of the resources used by instances of this type.
		/// </summary>
		public void Dispose() {}

		/// <summary>
		/// Implements a simple version of abstract URLs.  We won't use
		/// either of the arguments, which are generic to all event handlers.
		/// </summary>
		/// <param name="sender">The object that raised this event.</param>
		/// <param name="e">Generic bag of arguments.</param>
		public void OnBeginRequest(object sender, EventArgs e)
		{
			if (HttpContext.Current.Request.Path.IndexOf(".") >= 0)
			{
				//The request has an extension, so just return.
				return;
			}

			//Add ".aspx" to the computed physical file location.
			string strTestPhysicalPath = String.Concat(
				HttpContext.Current.Request.PhysicalPath,
				".aspx"
				);

			if (File.Exists(strTestPhysicalPath))
			{
				string strNewPath = String.Concat(
					HttpContext.Current.Request.Path,
					".aspx"
					);

				//A matching file exists.  Rewrite the request path.
				HttpContext.Current.RewritePath(strNewPath);
			}

			//No special action if we didn't find a match.  IIS will return
		    //a 404 Not Found for us.

			return;

		}

	}
}