/*

* 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:   Contains MNcdNodeContainer interface

*

*/

#ifndef M_NCD_NODE_CONTAINER_H

#define M_NCD_NODE_CONTAINER_H

#include <e32cmn.h>

#include "catalogsbase.h"

#include "ncdinterfaceids.h"

#include "ncdchildloadmode.h"

#include "ncdcontainertype.h"

class MNcdNode;

class MNcdLoadNodeOperation;

class MNcdLoadNodeOperationObserver;

/**

 *  Container may contain other nodes.

 *  This interface provides functions that can be used to

 *  get the nodes of the container. Also, a convenience function

 *  to load the content for the child nodes is provided.

 *

 *  This interface can be queried from node objects that are containers,

 *  after the node has been initialized.

 *

 *  

 */

class MNcdNodeContainer : public virtual MCatalogsBase

    {

public:

    /**

     * Unique identifier for the interface, required for all MCatalogsBase interfaces.

     *

     * 

     */

    enum { KInterfaceUid = ENcdNodeContainerUid };

    /**

     * Returns the child node count for this container. The count may be

     * used to get the upper limit for indexing the contained child nodes

     * with the ChildL() method.

     *

     * @return The number of the children in this container.

     */

    virtual TInt ChildCount() const = 0;

    /**

     * Returns a child (contained node) of this container.

     *

     * @note The reference count of the node is increased by one. So,

     * Release function of the node should be called when the node

     * is not needed anymore.

     *

     * @param aIndex is the index to the child of this container.

     * @return Pointer to the child node, may be an item or another container.

     *  Counted, Release() must be called after use.

     * @exception Leave System wide error code.

     * @exception Panic ENcdPanicIndexOutOfRange Index out of range.

     */

    virtual MNcdNode* ChildL( TInt aIndex ) = 0;

    /**

     * Loads node information from the content provider for the

     * children of this container.

     *

     * The loading of children is started from the given index.

     * Size informs the maximum number of children that are loaded.

     *

     * @param aIndex The index of the child that will be the first one

     *  to be loaded.

     * @param aSize The maximum number of children to load.

     *  For special cases: if KMaxTInt is given, then it will be

     *  interpreted so that all the children after aIndex should be loaded. 

     *  By using KMaxTInt, a parent container refresh may be skipped and 

     *  all the children may be requested from server even if parent's 

     *  child count information may not be valid. In normal cases, usage of 

     *  KMaxTInt should be avoided. Instead, refresh the parent first and 

     *  use the correct child count value. KMaxTInt may not be supported 

     *  for all type of containers. If not supported, then a leave will occur.  

     * @param aMode Load mode, determines whether structure, metadata or both

     *  will be loaded.

     * @param aObserver Observer for the operation.

     * @return Pointer to an operation that can 

     *  be used to check the progressing of the loading. Counted,

     *  Release() must be called after use.

     * @exception Leave System wide error code.

     *  KErrNotFound if trying to load metadata and no structure is present.

     *  KNcdErrorParallelOperationNotAllowed if a parallel client is running

     *  an operation for the same metadata, see MNcdOperation for full explanation.

     */

    virtual MNcdLoadNodeOperation* LoadChildrenL( 

        TInt aIndex, TInt aSize, TNcdChildLoadMode aMode,

        MNcdLoadNodeOperationObserver& aObserver ) = 0;

    /**

     * Tells the type of the folder. It may be a normal folder or a catalog.

     *

     * @return The type.

     */

    virtual TNcdContainerType ContainerType() const = 0;

protected:

    /**

    * Destructor.

    *

    * @see MCatalogsBase::~MCatalogsBase

    */

    virtual ~MNcdNodeContainer() {}

    };

#endif // M_NCD_NODE_CONTAINER_H