/*

* Copyright (c) 2006-2009 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:

*

*/

/**

 @file

 @publishedPartner 

 @released

*/

#ifndef MAUDIOSTREAMOBSERVER_H

#define MAUDIOSTREAMOBSERVER_H

#include <e32base.h>

#include <a3f/a3fbase.h>

#include <a3f/maudiostream.h>

/**

 * An interface to a set of AudioStream callback functions.

 *

 * this serves as the method of communication between the client and the

 * AudioStream.

 *

 * The class is a mixin and is intended to be inherited by the client class

 * that is interested in observing the AudioStream operation. The functions

 * encapsulated by this class are called when specific events occur while

 * processing audio.

 */

class MAudioStreamObserver

	{

public:

	/**

	 * Handles audio stream state change event.

	 *

	 * @param aStream A reference to the stream whose state changed.

	 * @param aReason A set of values describing why the state change occurred 

	 * corresponding to the system-wide error codes. The value will be KErrNone on successful calls.

	 * @param aNewState indicating the state in which the audio stream has changed.

	 */

	virtual void StateEvent(MAudioStream& aStream , TInt aReason, TAudioState aNewState)=0;

	/**

	 * Notifies that adding of processing unit to the stream has been completed successfully or otherwise.

	 *

	 * if the processing unit is added succesfully, then it must be removed from the

	 * stream before the processing unit is removed from the context or before the stream is removed.

	 *

	 * @param aStream A reference to the stream to which the processing unit was added.

	 * @param aInstance a pointer to the processing unit instance.

	 * @param aError an error code. KErrNone on success. Otherwise one of the system wide error codes.

	 */

	virtual void AddProcessingUnitComplete(MAudioStream& aStream, MAudioProcessingUnit* aInstance, TInt aError)=0;

	/**

	 * Notifies that removing of processing unit from the stream has been completed

	 * successfully or otherwise.

	 * 

	 * if the processing unit has been added succesfully, then it must be removed

	 * from the stream, before the processing unit is removed from the

	 * context or before the stream is removed.

	 * 

	 * @param aStream A reference to the stream from which the processing unit has been removed.

	 * @param aType the processing unit type.

	 * @param aInstance a pointer to the processing unit instance.

	 * @param aError an error code. KErrNone on success. Otherwise one of the system wide error codes.

	 */

	virtual void RemoveProcessingUnitComplete(MAudioStream& aStream, MAudioProcessingUnit* aInstance, TInt aError)=0;

	/**

	 * Call-back indicating that is the last buffer has been processed by the sink.

	 *

	 * @param aStream A reference to the stream.

	 */

	virtual void ProcessingFinished (MAudioStream& aStream)=0;

	/**

	 * Signals completion of a Flush() operation.

	 *

	 * @param aStream A reference to the stream on which Flush() was called.  

	 * @param aError an error code. KErrAbort if the associated stream has been unloaded, and the buffers cease to exist.

	 */

	virtual void FlushComplete (MAudioStream& aStream, TInt aError) = 0;

	};

#endif // MAUDIOSTREAMOBSERVER_H