// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CHROME_BROWSER_BACKGROUND_EXTENSIONS_BACKGROUND_APPLICATION_LIST_MODEL_H_
#define CHROME_BROWSER_BACKGROUND_EXTENSIONS_BACKGROUND_APPLICATION_LIST_MODEL_H_

#include <stddef.h>

#include <map>
#include <memory>
#include <string>

#include "base/memory/raw_ptr.h"
#include "base/memory/weak_ptr.h"
#include "base/observer_list.h"
#include "base/scoped_observation.h"
#include "chrome/browser/background/background_contents_service.h"
#include "chrome/browser/background/background_contents_service_observer.h"
#include "extensions/browser/extension_registry_observer.h"
#include "extensions/browser/permissions_manager.h"
#include "extensions/browser/process_manager.h"
#include "extensions/browser/process_manager_observer.h"
#include "extensions/common/extension.h"

class Profile;

namespace gfx {
class ImageSkia;
}

namespace extensions {
class ExtensionRegistry;
}  // namespace extensions

// Model for list of Background Applications associated with a Profile (i.e.
// extensions with kBackgroundPermission set, or hosted apps with a
// BackgroundContents).
class BackgroundApplicationListModel
    : public extensions::ExtensionRegistryObserver,
      public BackgroundContentsServiceObserver,
      public extensions::ProcessManagerObserver,
      public extensions::PermissionsManager::Observer {
 public:
  // Observer is informed of changes to the model.  Users of the
  // BackgroundApplicationListModel should anticipate that associated data,
  // e. g. the Icon, may exist and yet not be immediately available.  When the
  // data becomes available, OnApplicationDataChanged will be invoked for all
  // Observers of the model.
  class Observer {
   public:
    // Invoked when data that the model associates with an extension, such as
    // the Icon, has changed.
    virtual void OnApplicationDataChanged();

    // Invoked when the model detects a previously unknown extension and/or when
    // it no longer detects a previously known extension.
    virtual void OnApplicationListChanged(const Profile* profile);

   protected:
    virtual ~Observer();
  };

  // Create a new model associated with profile.
  explicit BackgroundApplicationListModel(Profile* profile);

  BackgroundApplicationListModel(const BackgroundApplicationListModel&) =
      delete;
  BackgroundApplicationListModel& operator=(
      const BackgroundApplicationListModel&) = delete;

  ~BackgroundApplicationListModel() override;

  // Associate observer with this model.
  void AddObserver(Observer* observer);

  // Return the icon associated with |extension|.  If the result isNull(),
  // there is no icon associated with the extension, or a pending task to
  // retrieve the icon has not completed.  See the Observer class above.
  //
  // NOTE: All icons are currently sized as
  //       ExtensionIconSet::EXTENSION_ICON_BITTY.
  gfx::ImageSkia GetIcon(const extensions::Extension* extension);

  // Return the position of |extension| within this list model.
  int GetPosition(const extensions::Extension* extension) const;

  // Return the extension at the specified |position| in this list model.
  const extensions::Extension* GetExtension(int position) const;

  // Returns true if the passed extension is a background app.
  static bool IsBackgroundApp(const extensions::Extension& extension,
                              Profile* profile) {
    return IsPersistentBackgroundApp(extension, profile) ||
           IsTransientBackgroundApp(extension, profile);
  }

  // Returns true if the passed extension is a persistent background app.
  static bool IsPersistentBackgroundApp(const extensions::Extension& extension,
                                        Profile* profile);

  // Returns true if the passed extension is a transient background app.
  // Transient background apps should only be treated as background apps while
  // their background page is active.
  static bool IsTransientBackgroundApp(const extensions::Extension& extension,
                                       Profile* profile);

  // Dissociate observer from this model.
  void RemoveObserver(Observer* observer);

  extensions::ExtensionList::const_iterator begin() const {
    return extensions_.begin();
  }

  extensions::ExtensionList::const_iterator end() const {
    return extensions_.end();
  }

  size_t size() const { return extensions_.size(); }

  // Returns true if all startup notifications have already been issued.
  bool startup_done() const { return startup_done_; }

  bool HasPersistentBackgroundApps() const;

 private:
  // Contains data associated with a background application that is not
  // represented by the Extension class.
  class Application;

  // Identifies and caches data related to the extension.
  void AssociateApplicationData(const extensions::Extension* extension);

  // Clears cached data related to |extension|.
  void DissociateApplicationData(const extensions::Extension* extension);

  // Returns the Application associated with |extension| or NULL.
  const Application* FindApplication(
      const extensions::Extension* extension) const;

  // Returns the Application associated with |extension| or NULL.
  Application* FindApplication(const extensions::Extension* extension);

  // extensions::ExtensionRegistryObserver:
  void OnExtensionLoaded(content::BrowserContext* browser_context,
                         const extensions::Extension* extension) override;
  void OnExtensionUnloaded(content::BrowserContext* browser_context,
                           const extensions::Extension* extension,
                           extensions::UnloadedExtensionReason reason) override;
  void OnShutdown(extensions::ExtensionRegistry* registry) override;

  // BackgroundContentsServiceObserver:
  void OnBackgroundContentsServiceChanged() override;
  void OnBackgroundContentsServiceDestroying() override;

  // extensions::PermissionsManager::Observer:
  void OnExtensionPermissionsUpdated(
      const extensions::Extension& extension,
      const extensions::PermissionSet& permissions,
      extensions::PermissionsManager::UpdateReason reason) override;

  // Intended to be called when extension system is ready.
  void OnExtensionSystemReady();

  // Notifies observers that some of the data associated with this background
  // application, e.g. the Icon, has changed.
  void SendApplicationDataChangedNotifications();

  // Refresh the list of background applications and generate notifications.
  void Update();

  // ProcessManagerObserver:
  void OnBackgroundHostCreated(extensions::ExtensionHost* host) override;
  void OnBackgroundHostClose(const std::string& extension_id) override;

  // Associates extension id strings with Application objects.
  std::map<std::string, std::unique_ptr<Application>> applications_;

  extensions::ExtensionList extensions_;
  base::ObserverList<Observer, true>::Unchecked observers_;
  const raw_ptr<Profile> profile_;
  bool startup_done_ = false;

  // Listens to extension load, unload notifications.
  base::ScopedObservation<extensions::ExtensionRegistry,
                          extensions::ExtensionRegistryObserver>
      extension_registry_observation_{this};

  base::ScopedObservation<BackgroundContentsService,
                          BackgroundContentsServiceObserver>
      background_contents_service_observation_{this};

  base::ScopedObservation<extensions::ProcessManager,
                          extensions::ProcessManagerObserver>
      process_manager_observation_{this};

  base::ScopedObservation<extensions::PermissionsManager,
                          extensions::PermissionsManager::Observer>
      permissions_manager_observation_{this};

  base::WeakPtrFactory<BackgroundApplicationListModel> weak_ptr_factory_{this};
};

#endif  // CHROME_BROWSER_BACKGROUND_EXTENSIONS_BACKGROUND_APPLICATION_LIST_MODEL_H_