/*

* Copyright (c) 2006 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:   Notifies observers of external changes to the calendar database

*

*/

#ifndef __CALENDBCHANGENOTIFIER_H

#define __CALENDBCHANGENOTIFIER_H

//  INCLUDES

#include <e32base.h>

#include <calchangecallback.h>      //MCalChangeCallBack

// FORWARD DECLARATIONS

class CCalSession;                  //Calendar session

class CCalenGlobalData;             //Calendar global data

// CLASS DECLARATION

/**

* Observer class for database changes.  Forwards callback from 

* MCalChangeCallBack2

*/

class MCalenDBChangeObserver

    {

    public:

        virtual void HandleDBChangeL() = 0;

    };

/**

*  CCalenDbChangeNotifier buffers notifications from MCalChangeCallBack2 and 

*  only notifies its observers after a set period has elapsed.  This prevents

*  Calendar views refreshing more often than necessary during a sync operation

*/

NONSHARABLE_CLASS(CCalenDbChangeNotifier) : public CActive,

                                                                  public MCalChangeCallBack2

    {

    public:  // Constructors and destructor

        /**

        * Constructor.

        * @param aGlobalData global data reference

        * @return a pointer to the new CCalenDbChangeNotifier instance

        */

        static CCalenDbChangeNotifier* NewL( CCalSession& aSession );

       /**

        * Destructor.

        */

        ~CCalenDbChangeNotifier();

    public:

        /**

        * Allow CCalenViews to register for database change notifications

        * @param aDBObserver Observer to register

        */

        void RegisterObserverL( MCalenDBChangeObserver& aDBObserver );

        /**

        * Allow CCalenViews to deregister for database change notifications

        * @param aDBObserver Observer to deregister

        */

        void DeRegisterObserverL( MCalenDBChangeObserver& aDBObserver );

        /**

        * Returns the time of the last call to MCalChangeCallBack2::CalChangeNotification

        * This is not necessarily the same time as the last notification issued by 

        * this class

        * @return Time of the last database modification as TTime

        */

        TTime LastDBModificationTime() const;

    public: 

        /**

        * From MCalChangeCallBack2

        * Called when the calendar database is changed through another

        * CCalSession

        * @param aChangeItems array of database items changed 

        */

        void CalChangeNotification( RArray<TCalChangeEntry>& aChangeItems );

    private:

        /**

        * C++ default constructor.

        * @param aGlobalData global data reference

        */

        CCalenDbChangeNotifier( CCalSession& aSession );

        /**

        * By default Symbian 2nd phase constructor is private.

        * Performs any construction which may leave

        */

        void ConstructL();

        /**

        * From CActive

        * Called when outstanding asynchronous request completes

        * This will be called when iNotificationTimer either completes

        * or is cancelled

        */

        void RunL();

        /**

        * From CActive

        * Called by the active scheduler if RunL leaves

        * Ensures we are ready to receive the next database event

        * @param aError System wide error code

        */

        TInt RunError( TInt aError );

        /**

        * From CActive

        * Implements cancellation of outstanding asynchronous requests

        * Cancels iNotificationTimer if started

        */

        void DoCancel();

    private:    // Data

        //Database change observer filter

        CCalChangeNotificationFilter* iCalChangeFilter;      

        //Observer array

        RPointerArray<MCalenDBChangeObserver> iDBObservers;

        //Timer to limit the amount of notifications issued by this class

        RTimer iNotificationTimer;

        //The time of the last received notification

        TTime iLastDbChangeNotification;

        //Flag to restart the timer after cancelling last tiemr request

        TBool iRestartTimer;

        CCalSession& iSession;

    };

#endif      // __CALENDBCHANGENOTIFIER_H

// End of File