/*

* Copyright (c) 2005-2008 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:   Active object that tracks changes on a PS property.

*

*/

#ifndef C_VCCENGPSPROPERTYLISTENER_H

#define C_VCCENGPSPROPERTYLISTENER_H

#include <e32base.h>

#include <e32property.h>

#include "mvccengpspropertylistenerobserver.h"

/*

 *  CVccEngPsPropertyListener subsribes to the given property. It is used to 

 *  notify its observers about the changed the value of the property.

 *  

 *   

 *  @code

 *  void CExampleClass::ConstructL()

 * 	{

 *   CVccEngPsPropertyListener* iPropListener = 

 *				CVccEngPsPropertyListener::NewL( KPSVccPropertyCategory, 

                                                 KVccPropKeyHoRequest );

 * 	 iPropListener.AddObserver( this );

 * 	 iPropListener.Start();

 * 	}	

 * 

 * 	void CExampleClass::PropertyChangedL( 

            const TUid aCategoryId,

            const TUint aKeyId,

            const TInt aValue )

 * 	{

 *  	if( aKeyId )

 * 			{

 * 			switch( aValue )

 * 				{				

 * 				case EVccManualStartCsToPsHoRequest:

 * 					// start CS->PS handover 

 * 					break;

 * 				default:

 * 					break;

 * 				}			

 * 			}

 *  }

 *   

 *  @endcode

 * 

 *  @lib hoengine.lib

 *  @since S60 v3.2

 */

class CVccEngPsPropertyListener : public CActive

    {

public:

	/**

	 * Symbian two-phased constructor.

     *

     * @param aCategoryId	category uid 

     * @param aKeyId Id of a key of the property.

     */

    static CVccEngPsPropertyListener* NewL( const TUid aCategoryId, 

    										const TUint aKeyId );

    /**

     * Destructor.

     */

    virtual ~CVccEngPsPropertyListener();

    /**

     * Adds an observer

     * @param aObserver Reference to observer to be added

     */

    void AddObserverL( MVccEngPsPropertyListenerObserver& aObserver );

    /**

     * Removes an observer

     * @param aObserver  Reference to observer to be removed

     */

    void RemoveObserver( MVccEngPsPropertyListenerObserver& aObserver );

    /**

     * Get the current value of the property.

     * @return Current key value

     */

    TInt CurrentValue();

    /**

     * Starts the listener.

     */

    void Start();

private: 

	/**

	 * Constructor.

	 * 

	 * @param aPropertyUid	category uid 

	 * @param aKeyId Id of a key of the property.

	 */

	CVccEngPsPropertyListener( const TUid aCategoryId, const TUint aKeyId );

	/**

	 * 2nd phase constructor

	 */

 	void ConstructL();

    /**

     * Notifies the observers about the property value change.

     * @leave Symbian error code in error case

     */

    void NotifyObserversL();

// from base class CActive.

    /**

     * @see CActive::RunL()

     */

    void RunL();

    /**

     * See CActive::DoCancel()

     */

    void DoCancel();

private: //data

	/**

	 * Uid of the property category to be watched.

	 */

 	TUid iCategoryId;

 	/**

 	 * The property key uid to be watched.

 	 */

 	TUint iKeyId;

 	/**

 	 * the property category.

 	 * Own

 	 */

 	RProperty iProperty;

 	/**

 	 * Obsevers for callback from this.

 	 * Own

 	 */

 	RPointerArray<MVccEngPsPropertyListenerObserver> iObservers;

    };

#endif // C_VCCENGPSPROPERTYLISTENER_H