lockstep/app/src/main/cpp/PlaybackEngine.h

//
// Created by david on 01.02.2026.
//

#ifndef LOCKSTEP_PLAYBACKENGINE_H
#define LOCKSTEP_PLAYBACKENGINE_H

#include "StepListener.h"
#include "MixingPlayer.h"
#include "RubberBandStretcher.h"
#include "mp3file.h"
#include "AudioCallback.h"
#include <string>
#include <thread>
#include <memory>
#include <atomic>

/** Provides music through a regular callback to oboe. Called from separate oboe thread. */
class MusicProvider : public AudioCallbackProvider {
public:
    explicit MusicProvider(RubberBand::RubberBandStretcher *stretcher, size_t buf_size_samples, int num_ch_out, std::atomic<int> *back_pressure);
    ~MusicProvider() override;

    /** Called from separate oboe thread. */
    void onAudioReady(float *data, int32_t frames) override;
private:
    RubberBand::RubberBandStretcher *stretcher;
    float *buf;
    float **buf_ptr;
    int idebug;
    size_t buf_size_samples;
    int num_ch_out;
    /** contains the current available() frames from 'stretcher' in the audio callback thread 2 (oboe) */
    std::atomic<int> *back_pressure;
};

class PlaybackEngine : public StepListener {
public:
    PlaybackEngine(std::string filesDir, int resid);
    virtual ~PlaybackEngine();
    /** Play a beat sound. */
    virtual void playBeat();
    void playMusic(int fd);
private:
    RubberBand::RubberBandStretcher stretcher;
    MixingPlayer *mPlayer;
    std::string mFilesDir;
    std::unique_ptr<MP3File> musicFile;
    std::atomic<bool> haveMusicFile;
    std::unique_ptr<std::thread> musicFeed;
    std::atomic<bool> exitMusicFeedThread;
    /** where musicFeedThread() keeps track of the fact that we have music set -- will start the audio cb */
    std::atomic<bool> isSetMusic;
    int android_fd;
    std::atomic<bool> haveTimeRatio;
    std::atomic<double> timeRatio;
    std::atomic<int> playbackRate;
    std::atomic<int> numOutChannels;
    std::atomic<int> numInChannels;
    /** contains the current available() frames from 'stretcher' in the audio callback thread 2 (oboe) */
    std::atomic<int> back_pressure;
    /** this is actually in frames, not samples */
    static size_t constexpr buf_size_samples = 1024;
    void initRubberBand();
    void closeRubberBand();
    void closeMusicFile();
    void musicFeedThread();
    void mapChannels(int *channel_map, int num_ch_in, int num_ch_out);
};

#endif //LOCKSTEP_PLAYBACKENGINE_H