/*

* Copyright (c) 2007 Nokia Corporation and/or its subsidiary(-ies).

* All rights reserved.

* This component and the accompanying materials are made available

* under the terms of the License "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:    Helper functions and macros for handling multiple observers.*

*/

#ifndef _MTV_OBSERVER_UTILS

#define _MTV_OBSERVER_UTILS

namespace MtvObserverUtils

{

/**

 *  Struct for holding a bunch of observers and a semaphore for controlling observer removal.

 *

 *  @since Live TV UI v1.0

 */

template <class ObserverType, template<class> class ContainerType = RPointerArray, class PointerType = ObserverType>

struct RObserverData

    {

    // constructor for initializing the semaphore

    RObserverData() : iSemaphore(0), iShutdown(EFalse)

        {

        }

    /**

     * Initializes the container.

     * This function is currently just a placeholder, later

     * it can be used to add support for CBase-derived containers,

     * assuming that all clients call OpenL and Close when using

     * this class.

     */

    void OpenL()

        {

        }

    /**

     * Closes the container.

     */

    void Close()

        {

        iContainer.Close();

        iShutdown = ETrue;

        }

    // Container can be RPointerArray, RArray.. 

    // At the moment CBase-derived containers are not supported.

    ContainerType<ObserverType> iContainer;

    // the semaphore is used so that when it has a value greater than zero, observers

    // are not removed, but nulled in the container

    TInt iSemaphore;

    // pointer type member helps code using this object, the using code does not

    // need to know the actual observer type

    PointerType* iObserver;

    // Set to ETrue when the provider of notifications is shut down.

    TBool iShutdown;

    };

/**

 * Removes NULL observers from a container.

 * @param aExistsNull Tells whether there are any NULL observers.

 * Checking this parameter inside this function makes invoking code simpler.

 * @param aObserverData Observer data object (usually a RObserverData).

 * This data object must contain a container of observers and a semaphore.

 */

template <class ObserverDataType>

static void RemoveNullObservers(TBool aExistsNull, ObserverDataType& aObserverData)

    {

    // semaphore must always be decremented 

    --aObserverData.iSemaphore;    

    if ( !aObserverData.iSemaphore && aExistsNull )

        {

        for (TInt i = aObserverData.iContainer.Count() - 1; i >= 0; --i)

            {

            if (aObserverData.iContainer[i] == NULL)

                {

                aObserverData.iContainer.Remove(i);

                }

            }

        }

    }

/**

 * Macro that invokes an observer function for all registered observers.

 * @param aNotification Observer function to call.

 * @param aObserverData Observer data object (usually a RObserverData).

 * This data object must contain a container of observers and a semaphore.

 */

#define RUN_NOTIFY_LOOP(aNotification, aObserverData) \

do \

    { \

    if ( !aObserverData.iShutdown )\

        {\

        ++aObserverData.iSemaphore; \

        TBool existsNull = EFalse; \

        const TInt count = aObserverData.iContainer.Count(); \

        for ( TInt i = 0; i < count; ++i ) \

            { \

            aObserverData.iObserver = aObserverData.iContainer[ i ]; \

            if ( aObserverData.iObserver ) \

                { \

                TRAP_IGNORE( aObserverData.iObserver->aNotification ); \

                } \

            else \

                { \

                existsNull = ETrue; \

                } \

            } \

        RemoveNullObservers(existsNull, \

            aObserverData); \

        }\

    } while (EFalse) \

/**

 * Macro that invokes an observer function for all registered observers.

 * @param aNotification Observer function to call.

 * @param aObserverData Observer data object (usually a RObserverData).

 * @param aError On return, contains the possible first error code that happened.

 * This data object must contain a container of observers and a semaphore.

 */

#define RUN_NOTIFY_LOOP_L(aNotification, aObserverData, aError) \

do \

    { \

    aError = KErrNone; \

    TInt ___mtvObserverUtilsNotifyLoopError = KErrNone; \

    if ( !aObserverData.iShutdown )\

        {\

        ++aObserverData.iSemaphore; \

        TBool existsNull = EFalse; \

        const TInt count = aObserverData.iContainer.Count(); \

        for ( TInt i = 0; i < count; ++i ) \

            { \

            aObserverData.iObserver = aObserverData.iContainer[ i ]; \

            if ( aObserverData.iObserver ) \

                { \

                TRAP( ___mtvObserverUtilsNotifyLoopError, aObserverData.iObserver->aNotification ); \

                if ( aError == KErrNone ) \

                    { \

                    aError = ___mtvObserverUtilsNotifyLoopError; \

                    } \

                } \

            else \

                { \

                existsNull = ETrue; \

                } \

            } \

        RemoveNullObservers(existsNull, \

            aObserverData); \

        }\

    } while (EFalse) \

/**

 * Adds an observer to an observer data object.

 * @param aObserverData Data object to which an observer is added.

 * @param aObserver Observer to add.

 * @param aError Error code to use for Leave if adding fails.

 */

template <class ObserverType, class ContainerType>

static void AddObserverL(ContainerType& aObserverData, ObserverType& aObserver, TInt aError)

    {

    if (aObserverData.iShutdown)

        {

        return;

        }

    TInt pos = aObserverData.iContainer.Find( &aObserver );

    if (KErrNotFound != pos)

        {

        return;

        }

    TInt error = aObserverData.iContainer.Append( &aObserver );

    if (KErrNone != error)

        {

        User::Leave(aError); 

        }

    }

/**

 * Removes an observer from an observer data object.

 * @param aObserverData Data object from which an observer is removed.

 * @param aObserver Observer to remove.

 */

template <class ObserverType, class ContainerType>

static void RemoveObserver( ContainerType& aObserverData, ObserverType& aObserver )

    {

    TInt pos = aObserverData.iContainer.Find( &aObserver );

    if ( KErrNotFound == pos  )

        {

        return;

        }

    if ( !aObserverData.iSemaphore )

        {

        // NotifyEventL is not part of call stack. Just remove.

        aObserverData.iContainer.Remove( pos );

        }

    else

        {

        // Simply set to NULL. NotifyEventL will remove observers.

        aObserverData.iContainer[ pos ] = NULL;

        }

    }

} // end namespace MtvObserverUtils

#endif //_MTV_OBSERVER_UTILS