text: /*****************************************************************************************
   *                                                                                       *
   * OpenSpace                                                                             *
   *                                                                                       *
   * Copyright (c) 2014-2018                                                               *
   *                                                                                       *
   * Permission is hereby granted, free of charge, to any person obtaining a copy of this  *
   * software and associated documentation files (the "Software"), to deal in the Software *
   * without restriction, including without limitation the rights to use, copy, modify,    *
   * merge, publish, distribute, sublicense, and/or sell copies of the Software, and to    *
   * permit persons to whom the Software is furnished to do so, subject to the following   *
   * conditions:                                                                           *
   *                                                                                       *
   * The above copyright notice and this permission notice shall be included in all copies *
   * or substantial portions of the Software.                                              *
   *                                                                                       *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,   *
   * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A         *
   * PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT    *
   * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF  *
   * CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE  *
   * OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                                         *
   ****************************************************************************************/
  
  #ifndef __OPENSPACE_CORE___SYNCHRONIZATIONWATCHER___H__
  #define __OPENSPACE_CORE___SYNCHRONIZATIONWATCHER___H__
  
  #include <openspace/util/resourcesynchronization.h>
  #include <memory>
  #include <mutex>
  #include <vector>
  #include <unordered_map>
  
  namespace openspace {
  
  /**
   * Delays callbacks of synchronization state changes to
   * when notify is called.
   */
  class SynchronizationWatcher {
  public:
      using WatchHandle = size_t;
  
      struct WatchData {
          std::weak_ptr<ResourceSynchronization> synchronization;
          ResourceSynchronization::CallbackHandle callbackHandle;
      };
  
      struct NotificationData {
          std::weak_ptr<ResourceSynchronization> synchronization;
          ResourceSynchronization::State state;
          WatchHandle handle;
          ResourceSynchronization::StateChangeCallback callback;
      };
  
      /*using SyncStateChangeCallback =
          std::function<void(
              std::shared_ptr<ResourceSynchronization>,
              ResourceSynchronization::State
          )>;*/
  
      WatchHandle watchSynchronization(
          std::shared_ptr<ResourceSynchronization> synchronization,
          ResourceSynchronization::StateChangeCallback callback
      );
  
      void unwatchSynchronization(WatchHandle watchHandle);
  
      void notify();
  
  private:
      WatchHandle generateWatchHandle();
      std::mutex _mutex;
      std::unordered_map<WatchHandle, WatchData> _watchedSyncs;
      std::vector<NotificationData> _pendingNotifications;
  
      WatchHandle nextWatchHandle = 0;
  };
  
  } // namespace openspace
  
  #endif // __OPENSPACE_CORE___SYNCHRONIZATIONWATCHER___H__
  