//  SPDX-License-Identifier: MIT
//
//  EmulationStation Desktop Edition
//  AudioManager.cpp
//
//  Low-level audio functions (using SDL2).
//

#include "AudioManager.h"

#include "Log.h"
#include "Settings.h"
#include "Sound.h"

#include <SDL2/SDL.h>

std::shared_ptr<AudioManager> AudioManager::sInstance;
std::vector<std::shared_ptr<Sound>> AudioManager::sSoundVector;
SDL_AudioDeviceID AudioManager::sAudioDevice = 0;
SDL_AudioSpec AudioManager::sAudioFormat;
SDL_AudioStream* AudioManager::sConversionStream;
bool AudioManager::sMuteStream = false;
bool AudioManager::sHasAudioDevice = true;
bool AudioManager::mIsClearingStream = false;

AudioManager::AudioManager()
{
    init();
}

AudioManager::~AudioManager()
{
    deinit();
}

std::shared_ptr<AudioManager>& AudioManager::getInstance()
{
    // Check if an AudioManager instance is already created, and if not then create it.
    if (sInstance == nullptr)
        sInstance = std::shared_ptr<AudioManager>(new AudioManager);

    return sInstance;
}

void AudioManager::init()
{
    LOG(LogInfo) << "Setting up AudioManager...";

    if (SDL_InitSubSystem(SDL_INIT_AUDIO) != 0) {
        LOG(LogError) << "Error initializing SDL audio!\n" << SDL_GetError();
        return;
    }

    LOG(LogInfo) << "Audio driver: " << SDL_GetCurrentAudioDriver();

    SDL_AudioSpec sRequestedAudioFormat;

    SDL_memset(&sRequestedAudioFormat, 0, sizeof(sRequestedAudioFormat));
    SDL_memset(&sAudioFormat, 0, sizeof(sAudioFormat));

    // Set up format and callback. SDL will negotiate these settings with the audio driver, so
    // if for instance the driver/hardware does not support 32-bit floating point output, 16-bit
    // integer may be selected instead. ES-DE will handle this automatically as there are no
    // hardcoded audio settings elsewhere in the code.
    sRequestedAudioFormat.freq = 44100;
    sRequestedAudioFormat.format = AUDIO_F32;
    sRequestedAudioFormat.channels = 2;
    sRequestedAudioFormat.samples = 1024;
    sRequestedAudioFormat.callback = mixAudio;
    sRequestedAudioFormat.userdata = nullptr;

    for (int i = 0; i < SDL_GetNumAudioDevices(0); i++) {
        LOG(LogInfo) << "Detected playback device: " << SDL_GetAudioDeviceName(i, 0);
    }

    sAudioDevice = SDL_OpenAudioDevice(0, 0, &sRequestedAudioFormat, &sAudioFormat,
            SDL_AUDIO_ALLOW_ANY_CHANGE);

    if (sAudioDevice == 0) {
        LOG(LogError) << "Unable to open audio device: " << SDL_GetError();
        sHasAudioDevice = false;
    }

    if (sAudioFormat.freq != sRequestedAudioFormat.freq) {
        LOG(LogDebug) << "AudioManager::init(): Requested sample rate " <<
                std::to_string(sRequestedAudioFormat.freq) << " could not be "
                "set, obtained " << std::to_string(sAudioFormat.freq);
    }
    if (sAudioFormat.format != sRequestedAudioFormat.format) {
        LOG(LogDebug) << "AudioManager::init(): Requested format " <<
                std::to_string(sRequestedAudioFormat.format) << " could not be "
                "set, obtained " << std::to_string(sAudioFormat.format);
    }
    if (sAudioFormat.channels != sRequestedAudioFormat.channels) {
        LOG(LogDebug) << "AudioManager::init(): Requested channel count " <<
                std::to_string(sRequestedAudioFormat.channels) << " could not be "
                "set, obtained " << std::to_string(sAudioFormat.channels);
    }
    #if defined(_WIN64) || defined(__APPLE__)
    // Beats me why the buffer size is not divided by the channel count on some operating systems.
    if (sAudioFormat.samples != sRequestedAudioFormat.samples) {
    #else
    if (sAudioFormat.samples != sRequestedAudioFormat.samples / sRequestedAudioFormat.channels) {
    #endif
        LOG(LogDebug) << "AudioManager::init(): Requested sample buffer size " <<
                std::to_string(sRequestedAudioFormat.samples / sRequestedAudioFormat.channels) <<
                " could not be set, obtained " << std::to_string(sAudioFormat.samples);
    }

    // Just in case someone changed the es_settings.xml file manually to invalid values.
    if (Settings::getInstance()->getInt("SoundVolumeNavigation") > 100)
        Settings::getInstance()->setInt("SoundVolumeNavigation", 100);
    if (Settings::getInstance()->getInt("SoundVolumeNavigation") < 0)
        Settings::getInstance()->setInt("SoundVolumeNavigation", 0);
    if (Settings::getInstance()->getInt("SoundVolumeVideos") > 100)
        Settings::getInstance()->setInt("SoundVolumeVideos", 100);
    if (Settings::getInstance()->getInt("SoundVolumeVideos") < 0)
        Settings::getInstance()->setInt("SoundVolumeVideos", 0);

    setupAudioStream(sRequestedAudioFormat.freq);
}

void AudioManager::deinit()
{
    // Due to bugs in SDL, freeing the stream causes random crashes. This is reported to the
    // user on some operating systems such as macOS, and it's annoying to have a crash at the
    // end of debugging session. So we'll simply disable the function until it has been properly
    // fixed in the SDL library.
//    SDL_FreeAudioStream(sConversionStream);

    SDL_CloseAudio();
    SDL_QuitSubSystem(SDL_INIT_AUDIO);
    sInstance = nullptr;
}

void AudioManager::mixAudio(void* /*unused*/, Uint8* stream, int len)
{
    // Process navigation sounds.
    bool stillPlaying = false;

    // Initialize the buffer to "silence".
    SDL_memset(stream, 0, len);

    // Iterate through all our samples.
    std::vector<std::shared_ptr<Sound>>::const_iterator soundIt = sSoundVector.cbegin();
    while (soundIt != sSoundVector.cend()) {
        std::shared_ptr<Sound> sound = *soundIt;
        if (sound->isPlaying()) {
            // Calculate rest length of current sample.
            Uint32 restLength = (sound->getLength() - sound->getPosition());
            if (restLength > static_cast<Uint32>(len)) {
                // If stream length is smaller than sample length, clip it.
                restLength = len;
            }
            // Mix sample into stream.
            SDL_MixAudioFormat(stream, &(sound->getData()[sound->getPosition()]),
                    sAudioFormat.format, restLength, static_cast<int>(Settings::getInstance()->
                    getInt("SoundVolumeNavigation") * 1.28f));
            if (sound->getPosition() + restLength < sound->getLength()) {
                // Sample hasn't ended yet.
                stillPlaying = true;
            }
            // Set new sound position. if this is at or beyond the end of the sample,
            // it will stop automatically.
            sound->setPosition(sound->getPosition() + restLength);
        }
        // Advance to next sound.
        soundIt++;
    }

    int streamLength = 0;

    // Process video stream audio generated by VideoFFmpegComponent.
    if (!mIsClearingStream)
        streamLength = SDL_AudioStreamAvailable(sConversionStream);

    if (streamLength <= 0 || mIsClearingStream) {
        // If nothing is playing, pause the device until there is more audio to output.
        if (!stillPlaying)
            SDL_PauseAudioDevice(sAudioDevice, 1);
        return;
    }

    int chunkLength = 0;

    // Cap the chunk length to the buffer size.
    if (streamLength > len)
        chunkLength = len;
    else
        chunkLength = streamLength;

    std::vector<Uint8> converted(chunkLength);

    int processedLength = SDL_AudioStreamGet(sConversionStream,
            static_cast<void*>(&converted.at(0)), chunkLength);

    if (processedLength < 0) {
        LOG(LogError) << "AudioManager::mixAudio(): Couldn't convert sound chunk:";
        LOG(LogError) << SDL_GetError();
        return;
    }

    // Enable only when needed, as this generates a lot of debug output.
//    LOG(LogDebug) << "AudioManager::mixAudio(): chunkLength "
//            "/ processedLength / streamLength: " << chunkLength << " / " <<
//            " / " << processedLength << " / " << streamLength;

    // This mute flag is used to make sure that the audio buffer already sent to the
    // stream is not played when the video player has been stopped. Otherwise there would
    // be a short time period when the audio would keep playing after the video was stopped
    // and before the stream was cleared in clearStream().
    if (sMuteStream) {
        SDL_MixAudioFormat(stream, &converted.at(0), sAudioFormat.format, processedLength, 0);
    }
    else {
        SDL_MixAudioFormat(stream, &converted.at(0), sAudioFormat.format, processedLength,
                static_cast<int>(Settings::getInstance()->getInt("SoundVolumeVideos") * 1.28f));
    }

    // If nothing is playing, pause the device until there is more audio to output.
    if (!stillPlaying && SDL_AudioStreamAvailable(sConversionStream) == 0)
        SDL_PauseAudioDevice(sAudioDevice, 1);
}

void AudioManager::registerSound(std::shared_ptr<Sound>& sound)
{
    sSoundVector.push_back(sound);
}

void AudioManager::unregisterSound(std::shared_ptr<Sound>& sound)
{
    for (unsigned int i = 0; i < sSoundVector.size(); i++) {
        if (sSoundVector.at(i) == sound) {
            sSoundVector[i]->stop();
            sSoundVector.erase(sSoundVector.cbegin() + i);
            return;
        }
    }
    LOG(LogError) << "AudioManager - tried to unregister a sound that wasn't registered";
}

void AudioManager::play()
{
    // Unpause audio, the mixer will figure out if samples need to be played...
    SDL_PauseAudioDevice(sAudioDevice, 0);
}

void AudioManager::stop()
{
    // Stop playing all Sounds.
    for (unsigned int i = 0; i < sSoundVector.size(); i++) {
        if (sSoundVector.at(i)->isPlaying())
            sSoundVector[i]->stop();
    }
    // Pause audio.
    SDL_PauseAudioDevice(sAudioDevice, 1);
}

void AudioManager::setupAudioStream(int sampleRate)
{
    SDL_AudioStatus audioStatus = SDL_GetAudioDeviceStatus(sAudioDevice);

    // It's very important to pause the audio device before setting up the stream,
    // or we may get random crashes if attempting to play samples at the same time.
    SDL_PauseAudioDevice(sAudioDevice, 1);
    SDL_FreeAudioStream(sConversionStream);

    // Used for streaming audio from videos.
    sConversionStream = SDL_NewAudioStream(AUDIO_F32, 2, sampleRate, sAudioFormat.format,
            sAudioFormat.channels, sAudioFormat.freq);
    if (sConversionStream == nullptr) {
        LOG(LogError) << "Failed to create audio conversion stream:";
        LOG(LogError) << SDL_GetError();
    }

    // If the device was previously in a playing state, then restore it.
    if (audioStatus == SDL_AUDIO_PLAYING)
        SDL_PauseAudioDevice(sAudioDevice, 0);
}

void AudioManager::processStream(const void* samples, unsigned count)
{
    if (mIsClearingStream)
        return;

    if (SDL_AudioStreamPut(sConversionStream, samples, count * sizeof(Uint8)) == -1) {
        LOG(LogError) << "Failed to put samples in the conversion stream:";
        LOG(LogError) << SDL_GetError();
        return;
    }

    if (count > 0)
        SDL_PauseAudioDevice(sAudioDevice, 0);
}

void AudioManager::clearStream()
{
    // The SDL_AudioStreamClear() function is unstable and causes random crashes, so
    // we have to implement a workaround instead where SDL_AudioStreamGet() is used
    // to empty the stream.
//    SDL_AudioStreamClear(sConversionStream);

    mIsClearingStream = true;

    int streamSize;
    int length = sAudioFormat.samples * 4;

    while ((streamSize = SDL_AudioStreamAvailable(sConversionStream)) > 0) {
        std::vector<Uint8> readBuffer(length);
        int processedLength = SDL_AudioStreamGet(sConversionStream,
                static_cast<void*>(&readBuffer.at(0)), length);
        if (processedLength <= 0) {
            break;
        }
    }

    mIsClearingStream = false;
}