/*********************************************************************/
/*                                                                   */
/*                     AgentService Framework                        */
/*                       www.agentservice.it                         */
/*                                                                   */
/* Copyright (C) 2007 l.i.d.o. - DIST, University of Genoa, Italy    */
/* GNU Lesser General Public License                                 */
/*                                                                   */
/* This library is free software; you can redistribute it and/or     */
/* modify it under the terms of the GNU Lesser General Public        */
/* License as published by the Free Software Foundation,             */
/* version 2.1 of the License.                                       */
/*                                                                   */
/* This library 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 */
/* Lesser General Public License for more details.                   */
/*                                                                   */
/* You should have received a copy of the GNU Lesser General Public  */
/* License along with this library; if not, write to the             */
/* Free Software Foundation, Inc., 59 Temple Place - Suite 330,      */
/* Boston, MA  02111-1307, USA.                                      */
/*                                                                   */
/*********************************************************************/
using System;
using System.Threading;

namespace AgentService.Agent.Behaviour
{
	/// <summary>
	/// Class WaitingBehaviour. Defines a behaviour that is waiting for
	/// an event to continue. It merely represents an integer semaphore
	/// that when reaches the "go" resumes the thread associated with the
	/// behaviour
	/// </summary>
	public class WaitingBehaviour
	{
		/// <summary>
		/// waiting behaviour hash code
		/// </summary>
		private int hashCode;
		/// <summary>
		/// Gets the waiting behaviour's hash code
		/// </summary>
		public int BehaviourHashCode 
		{
			get 
			{
				return this.hashCode;
			}
		}

		/// <summary>
		/// integer semaphore, do you rememeber Djkstra?
		/// </summary>
		private int semaphore; 

		/// <summary>
		/// Gets the waiting handle for the behaviour
		/// </summary>
		public bool IsBusy 
		{
			get 
			{
				return (this.semaphore > 0);
			}
		}

		/// <summary>
		/// Constructs a WaitingBehaviour object associated to the given thread with the
		/// given initial value of the semaphore
		/// </summary>
		/// <param name="hashCode">hashcode of the behaviour that is waiting</param>
		/// <param name="semaphore">integer value representing the initial value of the semaphore</param>
		public WaitingBehaviour(int hashCode, int semaphore)
		{
			// TODO: check consistent values of parameters?
			//		 thread null?
			//		 sempahore > 0?

			this.hashCode = hashCode;
			this.semaphore = semaphore;
		}

		/// <summary>
		/// Signal primitive, decrements the value of the semaphore if not zero
		/// </summary>
		public void Signal() 
		{
			// the integer semaphore is idempotent, if
			// the value has reached zero nothing happens
			// anymore

			try
			{
				Monitor.Enter(this);
				if (this.semaphore > 0)
				{
					this.semaphore--;
					// ok if zero... go!
					if (this.semaphore == 0)
					{
						// this.waitingThread.Resume();
						Monitor.PulseAll(this);
						
					}
				}
			}
			finally 
			{
				Monitor.Exit(this);
			}
		}

		/// <summary>
		/// Wait primitive, increments the value of the semaphore if not zero
		/// </summary>
		public void Wait() 
		{
			try
			{
				Monitor.Enter(this);
				if (this.semaphore > 0)
				{
					this.semaphore++;

				}
			}
			finally
			{
				Monitor.Exit(this);
			}

		}

		/// <summary>
		/// Executes a multiple wait, if the semaphore is equal to 0 
		/// it does nothing
		/// </summary>
		/// <param name="timesToWait">numer of wait ot execute</param>
		public void MultipleWait(int timesToWait) 
		{
			try
			{
				Monitor.Enter(this);
				if ((this.semaphore > 0) && (timesToWait > 0))
				{
					this.semaphore += timesToWait;
				}
			}
			finally
			{
				Monitor.Exit(this);
			}
		}

	}
}