/*

* Copyright (c) 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:  Meeting Request calendar info object extension

*

*/

#ifndef CEMAILEXTENSIONBASE_H

#define CEMAILEXTENSIONBASE_H

#include <e32base.h>

/**

* Base class for extensions. Instances of subclasses are requested from

* CExtendableEmail::ExtensionL() with specific extension UID.

* When client has ended using an extension it must be released with

* CExtendableEmail::ReleaseExtension().

* @since s60 v5.0

*/

class CEmailExtension : public CBase

{

public: 

    IMPORT_C ~CEmailExtension();

protected:    

    IMPORT_C CEmailExtension( const TUid& aUid );

public:

    /**         

    * returns extension uid

    * @return   uid of the extension.

    */

    IMPORT_C TUid Uid() const;

public: // for internal use

    /**

    * Decrement reference count.

    * @return new value of ref count

    */                           

    TUint DecRef();

    /**

    * Increment reference count.

    */                           

    void IncRef();

private:

    // extension interface UID defined by specific interface.

    const TUid iUid;    

    // Reference count is needed because more than one client may request

    // same extension (e.g. UI and protocol plugin).

    TUint iRefCount;

};

/**

* helper class for managing extensions. In most cases needed only

* by CExtendableEmail when extensions are created/released. Proto

* @since s60 v5.0

*/

class TEmailExtensions

{

public:

    /**

     * c++ constructor

     */

    IMPORT_C TEmailExtensions();

    /**

     * Destructor

     */

    IMPORT_C ~TEmailExtensions();

    /**

     * Returns extension index in iExtensions

     @ return extension index or KErrNotFound

     */

    IMPORT_C TInt FindExtension( const TUid& aUid ) const;

    /**

     * Returns extension by index or panics if invalid index is given

     * @param aIndex index in iExtensions

     * @panic EEmailExtensionIndexOutOfRange if index is out of range

     * @return extension

     */

    IMPORT_C CEmailExtension* Extension( const TInt aIndex ) const;

    /**

     * Adds extension to iExtensions array and increments its ref count by one.

     *

     * @param aExtenstion   extension to add

     * @leave KErrArgument  if aExtension is NULL

     */

    IMPORT_C void AddL( CEmailExtension* aExtension );

    /**

     * Removes extension from iExtensions

     * @param aExtenstion extension to remove

     */

    IMPORT_C void Remove( const CEmailExtension* aExtension );

private:    

    // array of extensions

    RPointerArray<CEmailExtension> iExtensions;

};

/**                 

* Classes that support email extension mechanism by returning extensions by

* uid should have this as base class.

*

* @since s60 v5.0

*/                 

class CExtendableEmail : public CBase

{

public:

    /**

    * Decrements extension reference count and deletes if count reaches 0.

    * Derived class must call this if it overrides this method.

    * @param aExtension extension to release

    */

    IMPORT_C virtual void ReleaseExtension( CEmailExtension* aExtension );

    /**

    * Requests extension. Default implementation performs lookup only and

    * derived class should implement actual instantiation because it knows

    * extensions it supports. Derived class must always call this to ensure

    * that extension is not created twice.

    *

    * @param aExtension extension to release

    */

    IMPORT_C virtual CEmailExtension* ExtensionL( const TUid& aInterfaceUid );

protected:    

    // extension containment

    TEmailExtensions iExtensions;

};

#endif // CEMAILEXTENSIONBASE_H