using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;

namespace DoLittle.Framework
{
	public class CrossAppDomainSingleton<T> : MarshalByRefObject where T:new()
	{
		private static readonly string AppDomainName = "Singleton AppDomain";
		private static T _instance;

		private static AppDomain GetAppDomain(string friendlyName)
		{
			IntPtr enumHandle = IntPtr.Zero;
			mscoree.CorRuntimeHostClass host = new mscoree.CorRuntimeHostClass();
			try
			{
				host.EnumDomains(out enumHandle);

				object domain = null;
				while (true)
				{
					host.NextDomain(enumHandle, out domain);
					if (domain == null) 
					{
						break;
					}
					AppDomain appDomain = (AppDomain)domain;
					if( appDomain.FriendlyName.Equals(friendlyName) ) 
					{
						return appDomain;
					}
				}
			}
			finally
			{
				host.CloseEnum(enumHandle);
				Marshal.ReleaseComObject(host);
				host = null;
			}
			return null;
		}


		public static T Instance
		{
			get
			{
				if (null == _instance)
				{
					AppDomain appDomain = GetAppDomain(AppDomainName);
					if (null == appDomain)
					{
						appDomain = AppDomain.CreateDomain(AppDomainName);
					}
					Type type = typeof(T);
					T instance = (T)appDomain.GetData(type.FullName);
					if (null == instance)
					{
						instance = (T)appDomain.CreateInstanceAndUnwrap(type.Assembly.FullName, type.FullName);
						appDomain.SetData(type.FullName, instance);
					}
					_instance = instance;				}

				return _instance;
			}
		}
	}


	public class MySingleton : CrossAppDomainSingleton<MySingleton>
	{

		public void HelloWorld()
		{
			Console.WriteLine("Hello world from '" + AppDomain.CurrentDomain.FriendlyName + " (" + AppDomain.CurrentDomain.Id + ")'");
		}
	}

	public class TestClass : MarshalByRefObject
	{
		public void TestMethod()
		{
			Console.WriteLine("**** Test method running in '" + AppDomain.CurrentDomain.FriendlyName + " (" + AppDomain.CurrentDomain.Id + ")' ****");
			MySingleton.Instance.HelloWorld();
			Console.WriteLine("\n\n");
		}
	}

	class Program
	{
		static void Main(string[] args)
		{
			Console.WriteLine("**** Call HelloWorld in root appdomain '" + AppDomain.CurrentDomain.FriendlyName + " (" + AppDomain.CurrentDomain.Id + ")' ****");
			MySingleton.Instance.HelloWorld();

			Console.WriteLine("\n\n");

			AppDomain dataDomain = AppDomain.CreateDomain("Data Domain");
			AppDomain logicDomain = AppDomain.CreateDomain("Business Logic Domain");


			Type testClassType = typeof(TestClass);
			TestClass dataDomainTestClass = (TestClass)dataDomain.CreateInstanceAndUnwrap(testClassType.Assembly.FullName,testClassType.FullName);
			TestClass logicDomainTestClass = (TestClass)logicDomain.CreateInstanceAndUnwrap(testClassType.Assembly.FullName, testClassType.FullName);


			dataDomainTestClass.TestMethod();
			logicDomainTestClass.TestMethod();
		}
	}
}