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 /****************************************************************************************
  * Copyright (c) 2009 Téo Mrnjavac <teo@kde.org>                                        *
  *                                                                                      *
  * This program is free software; you can redistribute it and/or modify it under        *
  * the terms of the GNU General Public License as published by the Free Software        *
  * Foundation; either version 2 of the License, or (at your option) any later           *
  * version.                                                                             *
  *                                                                                      *
  * This program is distributed in the hope that it will be useful, but WITHOUT ANY      *
  * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A      *
  * PARTICULAR PURPOSE. See the GNU General Public License for more details.             *
  *                                                                                      *
  * You should have received a copy of the GNU General Public License along with         *
  * this program.  If not, see <http://www.gnu.org/licenses/>.                           *
  ****************************************************************************************/
 
 #ifndef AMAROK_PLAYLISTMODELSTACK_H
 #define AMAROK_PLAYLISTMODELSTACK_H
 
 #include "proxymodels/AbstractModel.h"
 #include "PlaylistModel.h"
 #include "proxymodels/SortFilterProxy.h"
 #include "proxymodels/SearchProxy.h"
 #include "proxymodels/GroupingProxy.h"
 
 // THE PLAYLIST MODELS ARCHITECTURE
 // Amarok's playlist uses Qt's Model-View design pattern, so we have
 // * 1 source model which feeds the tracks data: Playlist::Model
 // * 3 proxies which modify the rows: SortFilterProxy==>SearchProxy==>GroupingProxy
 // * 1 or more views, such as Playlist::PrettyListView.
 // At any time a view should ONLY talk to the topmost proxy model, exposed by Playlist::
 // ModelStack::instance()->groupingProxy() or The::playlist() for short.
 // External classes that talk to the playlist should only talk to The::playlist(),
 // exceptionally to Playlist::ModelStack::instance()->bottom() if they really really need
 // the source model.
 //
 // Each playlist model implements the interface defined in Playlist::AbstractModel.
 // Each playlist proxy is a subclass od QSortFilterProxyModel through Playlist::ProxyBase,
 // and uses the default implementations of AbstractModel methods defined in ProxyBase.
 // To add a new proxy the recommended procedure is to subclass ProxyBase (which drags in
 // QSortFilterProxyModel, this is no problem because QSortFilterProxyModel is transparent
 // and fast by default), reimplement the relevant methods from ProxyBase and insert it in
 // the right place in the ModelStack constructor.
 //      --Téo 13/8/2009
 
 namespace Playlist
 {
 
 /**
  * Singleton class that handles and wraps around the Playlist models architecture.
  * To talk to the playlist, use The::playlist(). Playlist::ModelStack::instance()->bottom()
  * should only be used internally or in very specific situations.
  * @author Téo Mrnjavac <teo@kde.org>
  */
 class AMAROK_EXPORT ModelStack : public QObject
 {
     Q_OBJECT
 public:
     /**
      * Accessor for the singleton pattern.
      * @return a pointer to the only instance of Playlist::ModelStack.
      */
     static ModelStack *instance();
 
     /**
      * Singleton destructor.
      */
     static void destroy();
 
     /**
      * Use the 'The::playlist()' model unless you have a specific need for a lower model.
      */
     GroupingProxy           *groupingProxy();
     SortFilterProxy         *sortProxy();
     SortFilterProxy         *filterProxy();
     Playlist::Model         *bottom();
 
 private:
     /**
      * Constructor.
      */
     ModelStack();
 
     /**
      * Destructor.
      */
     ~ModelStack() override;
 
     static ModelStack *s_instance;       //!< Instance member.
 
     GroupingProxy   *m_grouping;
     SearchProxy     *m_search;
     SortFilterProxy *m_sortfilter;
     Model           *m_model;
 };
 
 }   //namespace Playlist
 
 namespace The
 {
     AMAROK_EXPORT Playlist::AbstractModel* playlist();
 }
 
 #endif  //AMAROK_PLAYLISTMODELSTACK_H