text: /*
   *  Copyright 2011 The WebRTC project authors. All Rights Reserved.
   *
   *  Use of this source code is governed by a BSD-style license
   *  that can be found in the LICENSE file in the root of the source
   *  tree. An additional intellectual property rights grant can be found
   *  in the file PATENTS.  All contributing project authors may
   *  be found in the AUTHORS file in the root of the source tree.
   */
  
  #ifndef PC_MEDIA_STREAM_TRACK_H_
  #define PC_MEDIA_STREAM_TRACK_H_
  
  #include <string>
  
  #include "api/media_stream_interface.h"
  #include "api/notifier.h"
  
  namespace webrtc {
  
  // MediaTrack implements the interface common to AudioTrackInterface and
  // VideoTrackInterface.
  template <typename T>
  class MediaStreamTrack : public Notifier<T> {
   public:
    typedef typename T::TrackState TypedTrackState;
  
    std::string id() const override { return id_; }
    MediaStreamTrackInterface::TrackState state() const override {
      return state_;
    }
    bool enabled() const override { return enabled_; }
    bool set_enabled(bool enable) override {
      bool fire_on_change = (enable != enabled_);
      enabled_ = enable;
      if (fire_on_change) {
        Notifier<T>::FireOnChanged();
      }
      return fire_on_change;
    }
  
   protected:
    explicit MediaStreamTrack(const std::string& id)
        : enabled_(true), id_(id), state_(MediaStreamTrackInterface::kLive) {}
  
    bool set_state(MediaStreamTrackInterface::TrackState new_state) {
      bool fire_on_change = (state_ != new_state);
      state_ = new_state;
      if (fire_on_change)
        Notifier<T>::FireOnChanged();
      return true;
    }
  
   private:
    bool enabled_;
    std::string id_;
    MediaStreamTrackInterface::TrackState state_;
  };
  
  }  // namespace webrtc
  
  #endif  // PC_MEDIA_STREAM_TRACK_H_
  