/*

* 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:  Command handler interface of the engine.

*

*/

#ifndef MVTENGCOMMANDHANDLER_H

#define MVTENGCOMMANDHANDLER_H

//  INCLUDES

#include <e32base.h>

#include "vtengcommands.h"

// CONSTANTS

// MACROS

// DATA TYPES

// FUNCTION PROTOTYPES

// FORWARD DECLARATIONS

class MVtEngCommandObserver;

// CLASS DECLARATION

/**

*  Handler for commands from client.

*

*  @lib videoteleng

*  @since 2.6

*/

class MVtEngCommandHandler

    {

    public:        

        /**

        * EAttribAsync

        *  command is asynchronous. 

        * EAttribEnabled

        *  Command can be executed at the moment.

        * EAttribSupported

        *  Command is supported by the engine.

        */

        enum TCommandCaps 

            { 

            EAttribAsync      = 0x00000001,

            EAttribEnabled    = 0x00000002,

            EAttribSupported  = 0x00000004

            };

        /**

        * Excecutes a command. This function leaves KErrNotReady

        * if engine is in such a state that command cannot be

        * executed.

        * 

        * @param aCommandId command to be executed.

        * @param aParams command parameters, NULL if command

        * does not require any.

        */

        virtual void ExecuteL( 

            const TVtEngCommandId aCommandId,

            TDesC8* aParams ) = 0;

        /**

        * Cancels a command.

        * @param aCommandId command to cancel. 

        * @return KErrNotFound if command is not pending.

        */

        virtual TInt CancelCommand( const TVtEngCommandId aCommandId ) = 0;

        /**

        * Returns capabilities of a command.

        * @return command caps

        */

        virtual TInt GetCommandCaps( 

            const TVtEngCommandId aCommand ) = 0;

        /**

        * Returns pending command.

        * @return pending command

        */

        virtual TVtEngCommandId PendingCommand() = 0;

        /**

        * Returns invalid command.

        * @return invalid command

        */

        virtual TVtEngCommandId InvalidCommand() = 0;

        /**

        * Sets command observer. First call on this is guaranteed

        * to succeed.

        * @param aObserver command observer.

        */

        virtual void AddObserverL( MVtEngCommandObserver& aObserver ) = 0;

        /**

        * Removes a command observer or if non-op if specified observer

        * is not found.

        * @param aObserver command observer to be removed.

        */

        virtual void RemoveObserver( MVtEngCommandObserver& aObserver ) = 0;

    };

#endif //MVTENGCOMMANDHANDLER_H

// End of File