Clementine-audio-player-Mac-Linux-Windows/src/covers/coverproviders.h

/* This file is part of Clementine.
   Copyright 2010, David Sansome <me@davidsansome.com>

   Clementine 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 3 of the License, or
   (at your option) any later version.

   Clementine 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 Clementine.  If not, see <http://www.gnu.org/licenses/>.
*/

#ifndef COVERPROVIDERS_H
#define COVERPROVIDERS_H

#include <QMutex>
#include <QObject>

class AlbumCoverFetcherSearch;
class CoverProvider;
class CoverProviderFactory;

// This is a singleton, a global repository for factories of cover providers. Each one of those has to register 
// with CoverProviders' instance by invoking "CoverProviders::instance().AddCoverProviderFactory(this)".
// Factories are automatically unregistered from the repository when they are deleted. 
// The class is thread safe except for the initialization.
class CoverProviders : public QObject {
  Q_OBJECT

public:
  // This performs lazy initialization of the CoverProviders which is not thread-safe!
  static CoverProviders& instance() {
      static CoverProviders instance_;
      return instance_;
  }

  // Let's a cover provider factory to register itself in the repository.
  void AddProviderFactory(CoverProviderFactory* factory);

  // Creates a list of cover providers, one for every registered factory. Providers that get created will
  // be children of the given AlbumCoverFetcherSearch's instance.
  QList<CoverProvider*> List(AlbumCoverFetcherSearch* parent);
  // Returns true if this repository has at least one registered provider factory.
  bool HasAnyProviderFactories() { return !cover_provider_factories_.isEmpty(); }

  ~CoverProviders() {}

private slots:
  void RemoveProviderFactory();

private:
  CoverProviders();
  CoverProviders(CoverProviders const&);
  void operator=(CoverProviders const&);

  QList<CoverProviderFactory*> cover_provider_factories_;
  QMutex mutex_;
};

#endif // COVERPROVIDERS_H