text: // Copyright 2016 The Chromium Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  #ifndef ASH_PUBLIC_CPP_EXTERNAL_ARC_MESSAGE_CENTER_ARC_NOTIFICATION_SURFACE_MANAGER_H_
  #define ASH_PUBLIC_CPP_EXTERNAL_ARC_MESSAGE_CENTER_ARC_NOTIFICATION_SURFACE_MANAGER_H_
  
  #include <string>
  
  #include "base/macros.h"
  
  namespace ash {
  
  class ArcNotificationSurface;
  
  // Keeps track of NotificationSurface.
  class ArcNotificationSurfaceManager {
   public:
    class Observer {
     public:
      // Invoked when a notification surface is added to the registry.
      virtual void OnNotificationSurfaceAdded(
          ArcNotificationSurface* surface) = 0;
  
      // Invoked when a notification surface is removed from the registry.
      virtual void OnNotificationSurfaceRemoved(
          ArcNotificationSurface* surface) = 0;
  
     protected:
      virtual ~Observer() = default;
    };
    static ArcNotificationSurfaceManager* Get();
  
    ArcNotificationSurfaceManager(const ArcNotificationSurfaceManager&) = delete;
    ArcNotificationSurfaceManager& operator=(
        const ArcNotificationSurfaceManager&) = delete;
  
    virtual ~ArcNotificationSurfaceManager();
  
    virtual ArcNotificationSurface* GetArcSurface(
        const std::string& notification_id) const = 0;
    virtual void AddObserver(Observer* observer) = 0;
    virtual void RemoveObserver(Observer* observer) = 0;
  
   protected:
    ArcNotificationSurfaceManager();
  
   private:
    static ArcNotificationSurfaceManager* instance_;
  };
  
  }  // namespace ash
  
  #endif  // ASH_PUBLIC_CPP_EXTERNAL_ARC_MESSAGE_CENTER_ARC_NOTIFICATION_SURFACE_MANAGER_H_
  