/*

* Copyright (c) 2004-2008 Nokia Corporation and/or its subsidiary(-ies).

* All rights reserved.

* This component and the accompanying materials are made available

* under the terms of "Eclipse Public License v1.0"

* which accompanies this distribution, and is available

* at the URL "http://www.eclipse.org/legal/epl-v10.html".

*

* Initial Contributors:

* Nokia Corporation - initial contribution.

*

* Contributors:

*

* Description: 

*

*/

using System;

using System.Collections.Generic;

using System.Text;

using System.Threading;

using System.ComponentModel;

namespace CrashDebuggerLib.Threading

{

    // <summary>

    // Serialises asynchronous requests - mainly because the symbol engine doesn't much

    // like having dynamically loaded codesegments unloaded underneath it - i.e. it doesn't

    // work multithreaded!

    // </summary>

    internal class AsyncOperationManager

    {

        #region Constructors

        public AsyncOperationManager()

        {

        }

        #endregion

        #region API

        public void Clear()

        {

            lock ( this )

            {

                iStarted = false;

                iQueue.Clear();

            }

        }

        public void Start()

        {

            lock ( this )

            {

                iStarted = true;

                StartNextOperation();

            }

        }

        public void Queue( AsyncOperation aOperation )

        {

            Queue( aOperation, false );

        }

        public void Queue( AsyncOperation aOperation, bool aHighPriority )

        {

            lock ( this )

            {

                if ( aHighPriority )

                {

                    iQueue.Insert( 0, aOperation );

                }

                else

                {

                    iQueue.Add( aOperation );

                }

            }

            //System.Diagnostics.Debug.WriteLine( "[AOP] - Add - Queue now contains " + iQueue.Count + " entries..." );

            StartNextOperation();

        }

        #endregion

        #region Event handlers

        void Operation_RunWorkerCompleted( object aSender, RunWorkerCompletedEventArgs aArgs )

        {

            lock ( this )

            {

                AsyncOperation op = (AsyncOperation) aSender;

                op.RunWorkerCompleted -= new RunWorkerCompletedEventHandler( Operation_RunWorkerCompleted );

                iPendingOperation = false;

            }

            //

            StartNextOperation();

            //System.Diagnostics.Debug.WriteLine( "[AOP] - Fin -Queue now contains " + iQueue.Count + " entries..." );

        }

        #endregion

        #region Properties

        #endregion

        #region Internal methods

        private void StartNextOperation()

        {

            lock ( this )

            {

                if ( iStarted )

                {

                    if ( iQueue.Count > 0 && !iPendingOperation )

                    {

                        AsyncOperation op = iQueue[ 0 ];

                        iQueue.RemoveAt( 0 );

                        //

                        op.RunWorkerCompleted += new RunWorkerCompletedEventHandler( Operation_RunWorkerCompleted );

                        iPendingOperation = true;

                        op.RunWorkerAsync( op );

                        //

                        //System.Diagnostics.Debug.WriteLine( "[AOP] - Start - Starting op with " + iQueue.Count + " remaining..." );

                    }

                    else

                    {

                        System.Diagnostics.Debug.WriteLine( "[AOP] - Start - Is empty!" );

                    }

                }

                else

                {

                    System.Diagnostics.Debug.WriteLine( "[AOP] - Start - Queue is disabled!" );

                }

            }

        }

        #endregion

        #region Data members

        private List<AsyncOperation> iQueue = new List<AsyncOperation>();

        private bool iPendingOperation = false;

        private bool iStarted = false;

        #endregion

    }

}