#include "AudioBackend.h"

#include <iostream>

AudioBackend audioBackend;

AudioBackend::AudioBackend() {
}

AudioBackend::~AudioBackend() {
    terminate();
}

void AudioBackend::init() {
    SDL_AudioSpec desired;
    desired.freq = 44100;
    desired.format = AUDIO_S16LSB;
    desired.channels = 2;
    desired.samples = 1024;
    desired.padding = 0;
    desired.userdata = this;
    desired.callback = [] (void *userdata, Uint8 *stream, int len) {
        static_cast<AudioBackend*>(userdata)->generate(stream, len);
    };

    _audioDevice = SDL_OpenAudioDevice(nullptr, 0, &desired, &_audioSpec, 0);
    if (!_audioDevice) {
        std::cerr << "Failed to open audio device: " << SDL_GetError() << std::endl;
        abort();
    }

    SDL_PauseAudioDevice(_audioDevice, 0);
}

void AudioBackend::terminate() {
    if (_audioDevice) {
        SDL_PauseAudioDevice(_audioDevice, 1);
        SDL_CloseAudioDevice(_audioDevice);
    }
}

void AudioBackend::generate(Uint8 *stream, int len) {
    len = len / 4;
    auto s = reinterpret_cast<int16_t *>(stream);

    for (int i = 0; i < len; i++) {
        int16_t l, r;
        Opl::generateSample(&l, &r);
        *s++ = l;
        *s++ = r;
    }
}