#region  --------------- Copyright Dresser Wayne Pignone -------------
/*
 * $Log: /Wrk/WayneLibraries/Wrk/StateEngine/Generic/AsyncWorkState.cs $
 * 
 * 5     08-03-25 10:32 Mattias.larsson
 * Ensure debugLogger is not null.
 * 
 * 4     07-11-28 15:40 roger.månsson
 * 
 * 3     07-10-23 13:47 roger.månsson
 * Must protect the access to the field currentWork, or there may be race
 * conditions, the field is maybe not be assigned until after the work is
 * done for example.
 * 
 * 2     07-10-17 13:20 roger.månsson
 * Made publicly available. Added overridable method WorkDone.
 * 
 * 1     07-03-27 9:33 roger.månsson
 * Created.
 */
#endregion
using System;
using System.Collections.Generic;
using Wayne.Lib;
using Wayne.Lib.StateEngine;
using System.Threading;

namespace Wayne.Lib.StateEngine.Generic
{
    /// <summary>
    /// Generic state that enables descendant classes to execute code on a worker thread 
    /// when the state is active. When the processing is completed, i.e. the PerformWork returns,
    /// the state will post a transition of the type specified in the constructor.
    /// 
    /// When exitting the state, we for the worker thread to complete before continuing.
    /// 
    /// Descendant classes can also use the AbortWork() method to signal to the worker thread that it should exit as fast as possible.
    /// 
    /// The PerformWork method should periodically check the Aborted property and if that is true, exit as fast as possible.
    /// </summary>
    /// <typeparam name="TMain"></typeparam>
    public abstract class AsyncWorkState<TMain> : State<TMain>
    {
        #region Fields

        bool aborted;
        object doneTransitionType;
        object runningLock = new object();

        #endregion

        #region Construction

        /// <summary>
        /// Initializes a new instance of the AsyncWorkState class.
        /// </summary>
        protected AsyncWorkState(object doneTransitionType)
        {
            this.doneTransitionType = doneTransitionType;
        }

        #endregion

        #region Methods

        /// <summary>
        /// Called when entering the state.
        /// </summary>
        /// <param name="stateEntry"></param>
        /// <param name="transition"></param>
        protected override void Enter(Wayne.Lib.StateEngine.StateEntry stateEntry, ref Wayne.Lib.StateEngine.Transition transition)
        {
            base.Enter(stateEntry, ref transition);

            if (transition == null)
            {
                aborted = false;
                ThreadPool.QueueUserWorkItem(new WaitCallback(DoWork), null);
            }
        }


        private void DoWork(object o)
        {
            try
            {
                try
                {
                    if (aborted)
                        return;

                    lock (runningLock)
                    {
                        PerformWork();
                    }
                }
                catch (Exception e)
                {
                    if ((ParentStateMachine.debugLogger != null) && ParentStateMachine.debugLogger.IsActive())
                        ParentStateMachine.debugLogger.Add(e);
                }
            }
            finally
            {
                this.ParentStateMachine.IncomingEvent(new StateEngineEvent(GenericEventType.AsyncDone));
            }
        }

        /// <summary>
        /// Called when exitting the state.
        /// </summary>
        protected override void Exit()
        {
            base.Exit();

            aborted = true;

            lock (runningLock)
            {
            }
            
        }

        /// <summary>
        /// Handles events.
        /// </summary>
        /// <param name="stateEngineEvent"></param>
        /// <param name="transition"></param>
        protected override void HandleEvent(StateEngineEvent stateEngineEvent, ref Transition transition)
        {
            base.HandleEvent(stateEngineEvent, ref transition);

            if (stateEngineEvent.Type.Equals(GenericEventType.AsyncDone))
            {
                stateEngineEvent.Handled = true;

                WorkDone(ref transition);
            }
        }

        /// <summary>
        /// Method that is called when the work is done. Override to specify another transition type than the one 
        /// specified in the constructor.
        /// </summary>
        /// <param name="transition"></param>
        protected virtual void WorkDone(ref Transition transition)
        {
            transition = new Transition(this, doneTransitionType);
        }

        /// <summary>
        /// Signals to the thread that it should exit as quick as possible. Can be overridden by descendant
        /// classes to create user code to abort.
        /// </summary>
        protected virtual void AbortWork()
        {
            aborted = true;
        }

        /// <summary>
        /// Signals that the PerformWork method should return as fast as possible.
        /// </summary>
        protected bool Aborted { get { return aborted; } }

        #endregion

        #region Abstract methods

        /// <summary>
        /// Method that is called in a worker thread.
        /// </summary>
        protected abstract void PerformWork();

        #endregion

    }
}