using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.IO;
using System.Reflection;
using System.Diagnostics;

namespace HLWebPluginHost.PluginLib {

  /// <summary>
  /// The purpose of this class is to actually provide the bytes for a given resource. 
  /// We subclass VirtualFile and override Open() to read the requested resource out of our plugin assembly.
  /// </summary>
  public class AssemblyResourceVirtualFile : System.Web.Hosting.VirtualFile {
    private string path;

    /// <summary>
    /// Constructor
    /// </summary>
    /// <param name="virtualPath"></param>
    public AssemblyResourceVirtualFile(string virtualPath)
      : base(virtualPath) {
      path = VirtualPathUtility.ToAppRelative(virtualPath);
    }

    public override Stream Open() {
      string[] parts = path.Split('/');
      string assemblyName = parts[2];
      string resourceName = parts[3];

      // While it is possible to directly load an assembly using Assembly.LoadFile() or Assembly.LoadFrom(), these methods will lock the DLL 
      // file for the duration of the process (e.g. until you restart IIS). A much better way to load an assembly is to create an in-memory copy 
      // of the DLL and load that, which is what we are doing here:
      assemblyName = Path.Combine(HttpRuntime.BinDirectory, assemblyName);
      byte[] assemblyBytes = File.ReadAllBytes(assemblyName);
      Assembly assembly = Assembly.Load(assemblyBytes);

      if (assembly != null)
        return assembly.GetManifestResourceStream(resourceName);

      return null;
    }
  }

}