audio_track.h

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#pragma once
 
#include <string>
#include <unordered_map>
#include <memory>
#include <chrono>
 
namespace audio {
 
// Forward declarations
class Sound;
class AudioSystem;
class AudioGroup;
 
class AudioTrack {
  friend class AudioManager;
 
 public:
  static std::unique_ptr<AudioTrack> Create(AudioSystem* system) {
    return std::unique_ptr<AudioTrack>(new AudioTrack(system));
  }
 
 private:
  explicit AudioTrack(AudioSystem* system);
 
 public:
  ~AudioTrack();
  
 private:
 
  void AddLayer(const std::string& name, const std::string& filepath, 
                AudioGroup* group = nullptr, bool looping = true);
 
  void RemoveLayer(const std::string& name);
 
  void FadeLayer(const std::string& name, float target_volume, 
                 std::chrono::milliseconds duration);
  
  void SetLayerVolume(const std::string& name, float volume);
  
  float GetLayerVolume(const std::string& name) const;
 
  void Play();
  
  void Stop();
  
  void Update();
 
 private:
  struct Layer {
    std::unique_ptr<Sound> sound;                        
    float current_volume;                                
    float target_volume;                                 
    float start_volume;                                  
    std::chrono::steady_clock::time_point fade_start_time; 
    std::chrono::steady_clock::time_point fade_end_time;   
    std::chrono::milliseconds fade_duration;             
    bool is_fading;                                      
 
    Layer() : current_volume(1.0f), target_volume(1.0f),
              start_volume(1.0f), is_fading(false),
              fade_duration(std::chrono::milliseconds(0)) {}
  };
 
  AudioSystem* system_;                           
  std::unordered_map<std::string, Layer> layers_; 
  bool is_playing_;                               
};
 
}  // namespace audio