// /**
// ********
// *
// * ORIGIONAL CODE BASE IS Copyright (C) 2006-2010 by Alphons van der Heijden
// * The code was donated on 4/28/2010 by Alphons van der Heijden
// * To Brandon'Dimentox Travanti' Husbands & Malcolm J. Kudra which in turn Liscense under the GPLv2.
// * In agreement to Alphons van der Heijden wishes.
// *
// * The community would like to thank Alphons for all of his hard work, blood sweat and tears.
// * Without his work the community would be stuck with crappy editors.
// *
// * The source code in this file ("Source Code") is provided by The LSLEditor Group
// * to you under the terms of the GNU General Public License, version 2.0
// * ("GPL"), unless you have obtained a separate licensing agreement
// * ("Other License"), formally executed by you and Linden Lab.  Terms of
// * the GPL can be found in the gplv2.txt document.
// *
// ********
// * GPLv2 Header
// ********
// * LSLEditor, a External editor for the LSL Language.
// * Copyright (C) 2010 The LSLEditor Group.
// 
// * This program is free software; you can redistribute it and/or
// * modify it under the terms of the GNU General Public License
// * as published by the Free Software Foundation; either version 2
// * of the License, or (at your option) any later version.
// *
// * This program is distributed in the hope that it will be useful,
// * but WITHOUT ANY WARRANTY; without even the implied warranty of
// * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// * GNU General Public License for more details.
// *
// * You should have received a copy of the GNU General Public License
// * along with this program; if not, write to the Free Software
// * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
// ********
// *
// * The above copyright notice and this permission notice shall be included in all 
// * copies or substantial portions of the Software.
// *
// ********
// */
using System;
using System.Reflection;
using System.Collections;
using System.Diagnostics;
using System.Threading;

// http://www.codeproject.com/csharp/messageloop.asp

namespace LSLEditor.Helpers
{
	/// <summary>
	/// Represents an object that performs a certain action asynchronously, by using an internal buffer queue
	/// and one internal thread.
	/// </summary>
	public class TaskQueue : IDisposable
	{
		#region Member Variables

		/// <summary>Reference to the thread used to empty the queue</summary>
		private Thread WorkerThread;
		/// <summary>Internal queue that serves as buffer for required actions</summary>
		private Queue Tasks;
		/// <summary>Used to signal the thread when a new object is added to the queue</summary>
		private AutoResetEvent SignalNewTask;
		/// <summary>Flag that notifies that the object should be disposed</summary>
		private bool stop;
		#endregion Member Variables

		#region Constructor

		/// <summary>Creates a new buffered object</summary>
		public TaskQueue()
		{
			WorkerThread = null;

			// Make sure the queue is synchronized. This is required because items are added to the queue
			// from a different thread than the thread that empties the queue
			Tasks = Queue.Synchronized(new Queue());

			SignalNewTask = new AutoResetEvent(false);

			stop = false;
		}
		#endregion Ctor

		#region Public Methods

		public void Start()
		{
			Stop();

			stop = false;
			Tasks.Clear();

			WorkerThread = new Thread(new ThreadStart(Worker));
			WorkerThread.IsBackground = true;
			WorkerThread.Start();
		}

		public void Stop()
		{
			if(WorkerThread!=null)
			{
				WorkerThread.Abort();
				if (!WorkerThread.Join(2000))
				{
					// problems
					System.Windows.Forms.MessageBox.Show("TaskQueue thread not Aborted", "Oops...");
				}
				WorkerThread = null;
			}
		}

		public void Invoke(object ActiveObject,string MethodName, params object[] args)
		{
			if (ActiveObject == null)
				return;
			try
			{
				// Add the object to the internal buffer
				Tasks.Enqueue(new Task(ActiveObject, MethodName, args));

				// Signal the internal thread that there is some new object in the buffer
				SignalNewTask.Set();
			}
			catch (Exception e)
			{
				Trace.WriteLine(string.Format("I An exception occurred in TaskQueue.Invoke: {0}", e.Message));
				// Since the exception was not actually handled and only logged - propagate it
				throw;
			}
		}
		#endregion Public Methods

		#region Private Methods

		/// <summary>Method executed by the internal thread to empty the queue</summary>
		private void Worker()
		{
			Thread.CurrentThread.CurrentCulture = new System.Globalization.CultureInfo("en-US", false);
			Thread.CurrentThread.CurrentUICulture = new System.Globalization.CultureInfo("en-US", false);

			while (!stop)
			{
				try
				{
					// Note: this code is safe (i.e. performing the .Count and .Dequeue not inside a lock)
					// because there is only one thread emptying the queue.
					// Even if .Count returns 0, and before Dequeue is called a new object is added to the Queue
					// then still the system will behave nicely: the next if statement will return false and
					// since this is run in an endless loop, in the next iteration we will have .Count > 0.
					if (Tasks.Count > 0)
					{
						(Tasks.Dequeue() as Task).Execute();
					}

					// Wait until new objects are received or Dispose was called
					if (Tasks.Count == 0)
					{
						SignalNewTask.WaitOne();
					}
				}
				catch (ThreadAbortException)
				{
					Trace.WriteLine("TaskQueue.Worker: ThreadAbortException, no problem");
				}
				catch (Exception e)
				{
					Trace.WriteLine(string.Format("TaskQueue.Worker: {0}", e.Message));
					// Since the exception was not actually handled and only logged - propagate it
					throw;
				}
			}
		}

		#endregion Private Methods

		#region IDisposable Members and Dispose Pattern

		private bool disposed = false;

		~TaskQueue()
		{
			Dispose(false);
		}

		public void Dispose()
		{
			Dispose(true);
			GC.SuppressFinalize(this);
		}

		protected virtual void Dispose(bool disposing)
		{
			if (!this.disposed)
			{
				if (disposing)
				{
					try
					{
						stop = true;
						SignalNewTask.Set();
					}
					catch (Exception e)
					{
						Trace.WriteLine(string.Format("An exception occurred in MessageLoop.AddToBuffer: {0}", e.Message));
						// Since the exception was not actually handled and only logged - propagate it
						throw;
					}
				}
				this.disposed = true;
			}
		}
		#endregion IDisposable Members and Dispose Pattern

		#region Task
		/// <summary>The tasks being saved in the queue</summary>
		private class Task
		{
			private object ActiveObject;
			private object[] args;
			public string MethodName;
			public Task(object ActiveObject, string MethodName, params object[] args)
			{
				this.ActiveObject = ActiveObject;
				this.MethodName = MethodName;
				this.args = args;
			}

			public void Execute()
			{
				try
				{
					MethodInfo mi = ActiveObject.GetType().GetMethod(MethodName,
						BindingFlags.Public | 
						BindingFlags.Instance |
						//BindingFlags.DeclaredOnly |
						BindingFlags.NonPublic
						);
					mi.Invoke(ActiveObject, args);
				}
				catch (ThreadAbortException)
				{
					Trace.WriteLine("TaskQueue.Task.Execute: ThreadAbortException, no problem");
				}
				catch (Exception exception)
				{
					Exception innerException = exception.InnerException;
					if (innerException == null)
						innerException = exception;
					string strMessage = OopsFormatter.ApplyFormatting(innerException.Message);
					string strStackTrace = OopsFormatter.ApplyFormatting(innerException.StackTrace);

					System.Windows.Forms.MessageBox.Show(strMessage + "\r\n" + strStackTrace, "Oops...");
				}
			}
		}
		#endregion Task
	}
}