#include "playback.h"
#include "SDL_mixer.h"
#include <SDL_audio.h>
#include <SDL.h>
#include <exception>
#include <thread>
#include <cmath>
#ifdef __linux__
#include <pthread.h>
#endif
#include "log.hpp"
#include <filesystem>
using namespace std::chrono;
size_t CalculateBufSize(SDL_AudioSpec *obtained, double seconds, double max_seconds, size_t samples_override = 0) {
    return ((((samples_override == 0) ? obtained->samples : samples_override) * std::min(seconds, max_seconds)) + 1) * sizeof(SAMPLETYPE) * obtained->channels;
}
void PlaybackInstance::SDLCallbackInner(Uint8 *stream, int len) {
    SDL_memset((void*)stream, 0, len);
    if (!playback_ready.load()) {
        return;
    }
    if (st == nullptr) {
        return;
    }
	size_t i = 0;
	size_t max = 0;
	size_t unit = sizeof(SAMPLETYPE) * spec.channels;
	size_t bytes_per_iter = std::min(((bufsize / unit)) * unit, (size_t)fakespec.size);
	while (st->numSamples() < (size_t)len) {
		if (general_mixer == nullptr) {
			return;
		}
		general_mixer(nullptr, buf + i, (int)bytes_per_iter);
		i += bytes_per_iter;
		max = i + bytes_per_iter;
        if (max >= bufsize) {
            st->putSamples((SAMPLETYPE*)buf, i/unit);
            i = 0;
            max = i + bytes_per_iter;
        }
	}
    st->receiveSamples((SAMPLETYPE*)stream, len / unit);
}
void PlaybackInstance::SDLCallback(void *userdata, Uint8 *stream, int len) {
    ((PlaybackInstance*)userdata)->SDLCallbackInner(stream, len);
}
Mix_Music *PlaybackInstance::Load(const char *file) {
    {
        std::filesystem::path fpath = std::string(file);
        fpath = fpath.parent_path() / fpath.stem();

        std::string fpath_str = fpath.string();
        std::vector<std::string> soundfonts = {fpath_str + ".sf2", fpath_str + ".dls"};
        std::string sf_path_str = "";
        bool any_path_exists = false;
        for (auto sf_path : soundfonts) {
            if (std::filesystem::exists(sf_path)) {
                any_path_exists = true;
                sf_path_str += ";" + sf_path;
            }
        }
        if (any_path_exists) {
            sf_path_str = sf_path_str.substr(1);
            Mix_SetSoundFonts(sf_path_str.c_str());
        } else {
            Mix_SetSoundFonts(NULL);
        }
    }
    Mix_Music *output = Mix_LoadMUS(file);
    if (output == nullptr) {
        ERROR.writefln("Error loading music '%s': %s", file, Mix_GetError());
        error_mutex.lock();
        errors.emplace("Error loading music!");
        error_mutex.unlock();
        return nullptr;
    }
    Mix_PlayMusicStream(output, -1);
    length = Mix_MusicDuration(output);
    update.store(true);
    current_file_mutex.lock();
    current_file = std::string(file);
    const char *title_tag = Mix_GetMusicTitleTag(output);
    // Check for an empty string, which indicates there's no title tag.
    if (title_tag[0] == '\0') { 
        std::filesystem::path path(current_file.value());
        current_title = path.stem().string();
    } else {
        current_title = std::string(title_tag);
    }
    current_file_mutex.unlock();
    set_signal(PlaybackSignalFileChanged);
    return output;
}
void PlaybackInstance::Unload(Mix_Music *music) {
    Mix_HaltMusicStream(music);
    Mix_FreeMusic(music);
    current_file_mutex.lock();
    current_file = {};
    current_title = {};
    current_file_mutex.unlock();
}
void PlaybackInstance::UpdateST() {
    if (speed > 0.0f && speed_changed.exchange(false)) {
        st->setRate(speed);
        set_signal(PlaybackSignalSpeedChanged);
    }
    if (tempo > 0.0f && tempo_changed.exchange(false)) {
        st->setTempo(tempo);
        set_signal(PlaybackSignalTempoChanged);
    }
    if (pitch > 0.0f && pitch_changed.exchange(false)) {
        st->setPitch(pitch);
        set_signal(PlaybackSignalPitchChanged);
    }
}
double PlaybackInstance::GetMaxSeconds() {
    return std::max((double)(MaxSpeed * MaxTempo), st->getInputOutputSampleRatio());
}
void PlaybackInstance::ThreadFunc() {
    #ifdef __linux__
    pthread_setname_np(pthread_self(), "Playback control thread");
    #endif
    bool reload = false;
    speed_changed.store(true);
    tempo_changed.store(true);
    pitch_changed.store(true);
    while (running) {
        playback_ready.store(false);
        if (!SDL_WasInit(SDL_INIT_AUDIO)) {
            if (SDL_InitSubSystem(SDL_INIT_AUDIO) < 0) {
                ERROR.writefln("Error initializing SDL: '%s'", SDL_GetError());
                error_mutex.lock();
                errors.emplace("Failed to initialize SDL!");
                error_mutex.unlock();
                return;
            }
        }
        SDL_AudioSpec obtained;
        SDL_AudioSpec desired;
        desired.format = 
        #ifdef SOUNDTOUCH_INTEGER_SAMPLES
            AUDIO_S16SYS;
        #else
            AUDIO_F32SYS;
        #endif
        desired.freq = 48000;
        desired.samples = 1024;
        desired.channels = 2;
        desired.callback = PlaybackInstance::SDLCallback;
        desired.userdata = this;
        st = new SoundTouch();
        Mix_Init(MIX_INIT_FLAC|MIX_INIT_MID|MIX_INIT_MOD|MIX_INIT_MP3|MIX_INIT_OGG|MIX_INIT_OPUS|MIX_INIT_WAVPACK);
        if ((device = SDL_OpenAudioDevice(nullptr, 0, &desired, &obtained, SDL_AUDIO_ALLOW_CHANNELS_CHANGE|SDL_AUDIO_ALLOW_FREQUENCY_CHANGE|SDL_AUDIO_ALLOW_SAMPLES_CHANGE)) == 0) {
            ERROR.writefln("Error opening audio device: '%s'", SDL_GetError());
            error_mutex.lock();
            errors.emplace("Failed to open audio device!");
            error_mutex.unlock();
            running = false;
            break;
        }
        spec = obtained;
        st->setSampleRate(spec.freq);
        st->setChannels(spec.channels);
        UpdateST();
        bufsize = 0;
        fakespec = spec;
        double maxSeconds = GetMaxSeconds();
        fakespec.size *= maxSeconds;
        fakespec.samples *= maxSeconds;
        size_t new_bufsize = CalculateBufSize(&spec, GetMaxSeconds(), MaxSeconds);
        buf = (Uint8*)malloc(new_bufsize);
        if (buf == nullptr) {
            ERROR.writeln("Failed to allocate memory for playback!");
            error_mutex.lock();
            errors.emplace("Failed to allocate memory for playback!");
            error_mutex.unlock();
            set_signal(PlaybackSignalErrorOccurred);
            running = false;
            break;
        }
        bufsize = new_bufsize;
        general_mixer = Mix_GetGeneralMixer();
        Mix_InitMixer(&fakespec, SDL_FALSE);
        SDL_PauseAudioDevice(device, 0);
        Mix_Music *music = Load(filePath.c_str());
        reload = false;
        if (music) {
            playback_ready.store(true);
        } else {
            playback_ready.store(false);
        }
        set_signal(PlaybackSignalStarted);
        while (running) {
            if (file_changed.exchange(false)) {
                Unload(music);
                music = Load(filePath.c_str());
                if (music) {
                    playback_ready.store(true);
                } else {
                    playback_ready.store(false);
                }
            }
            if (flag_mutex.try_lock()) {
                if (seeking.exchange(false)) {
                    Mix_SetMusicPositionStream(music, position);
                    set_signal(PlaybackSignalSeeked);
                }
                if (pause_changed.exchange(false)) {
                    if (paused) {
                        Mix_PauseMusicStream(music);
                        set_signal(PlaybackSignalPaused);
                    } else {
                        Mix_ResumeMusicStream(music);
                        set_signal(PlaybackSignalResumed);
                    }
                }
                if (update.exchange(false)) {
                    Mix_VolumeMusicStream(music, (int)(volume / 100.0 * MIX_MAX_VOLUME));
                    SDL_LockAudioDevice(device);
                    UpdateST();
                    size_t correct_buf_size = CalculateBufSize(&spec, GetMaxSeconds(), MaxSeconds);
                    size_t max_buf_size = correct_buf_size * 10;
                    bool too_large = max_buf_size < bufsize;
                    bool too_small = correct_buf_size > bufsize;
                    if (too_large) {
                        ERROR.writes("Bufsize is too large - ");
                    } else if (too_small) {
                        ERROR.writes("Bufsize is too small - ");
                    }
                    if (too_large || too_small) {
                        ERROR.writeln("Resizing buffer...");
                        general_mixer = nullptr;
                        bufsize = 0;
                        buf = (Uint8*)realloc((void*)buf, correct_buf_size);
                        if (buf == nullptr) {
                            ERROR.writes("Failed to allocate memory for playback!");
                            error_mutex.lock();
                            errors.emplace("Failed to allocate memory for playback!");
                            error_mutex.unlock();
                            set_signal(PlaybackSignalErrorOccurred);
                            running = false;
                            break;
                        }
                        bufsize = correct_buf_size;
                    }
                    SDL_UnlockAudioDevice(device);
                }
                flag_mutex.unlock();
            }
            position = Mix_GetMusicPosition(music);
            std::this_thread::sleep_for(20ms);
        }
        playback_ready.store(false);
        // ====
        Unload(music);
        SDL_CloseAudioDevice(device);
        Mix_CloseAudio();
        Mix_Quit();
        SDL_QuitSubSystem(SDL_INIT_AUDIO);
        delete st;
        free(buf);
    }
    current_file_mutex.lock();
    current_file = {};
    current_file_mutex.unlock();
    set_signal(PlaybackSignalStopped);
}

PlaybackInstance::PlaybackInstance() {
    running = false;
    paused = true;
    position = 0;
    length = 0;
    volume = 100.0;
    speed = 1.0;
    pitch = 1.0;
    tempo = 1.0;
    tempo_changed.store(true);
    speed_changed.store(true);
    pitch_changed.store(true);
    current_file = {};
    playback_ready = false;
    bufsize = 0;
}
std::optional<std::string> PlaybackInstance::get_current_file() {
    current_file_mutex.lock();
    std::optional<std::string> output = current_file;
    current_file_mutex.unlock();
    return output;
}
std::optional<std::string> PlaybackInstance::get_current_title() {
    current_file_mutex.lock();
    std::optional<std::string> output = current_title;
    current_file_mutex.unlock();
    return output;
}
PlaybackInstance::~PlaybackInstance() {
    Stop();
}

void PlaybackInstance::Start(std::string filePath) {
    this->filePath = filePath;
    INFO.writefln("Playing %s...", filePath.c_str());
    flag_mutex.lock();
    this->position = 0.0;
    seeking.store(true);
    paused = false;
    Update();
    if (running.exchange(true)) {
        file_changed.store(true);
    } else {
        thread = std::thread(&PlaybackInstance::ThreadFunc, this);
    }
    flag_mutex.unlock();
}
double PlaybackInstance::GetPosition() {
    return position;
}
double PlaybackInstance::GetLength() {
    return length;
}

void PlaybackInstance::Seek(double position) {
    flag_mutex.lock();
    this->position = position;
    seeking.store(true);
    flag_mutex.unlock();
}

void PlaybackInstance::Pause() {
    flag_mutex.lock();
    paused = !paused;
    pause_changed.store(true);
    flag_mutex.unlock();
}

bool PlaybackInstance::IsPaused() {
    return paused;
}

void PlaybackInstance::Stop() {
    if (running.exchange(false)) {
        thread.join();
    }
}
void PlaybackInstance::Update() {
    if (prev_pitch != pitch) {
        pitch_changed.store(true);
    }
    if (prev_speed != speed) {
        speed_changed.store(true);
    }
    if (prev_tempo != tempo) {
        tempo_changed.store(true);
    }
    update.store(true);
}

bool PlaybackInstance::IsStopped() {
    return !running;
}
optional<std::string> PlaybackInstance::GetError() {
    if (ErrorExists()) {
        error_mutex.lock();
        std::string error = errors.back();
        errors.pop();
        error_mutex.unlock();
        return error;
    } else {
        return {};
    }
}
bool PlaybackInstance::ErrorExists() {
    error_mutex.lock();
    bool output = !errors.empty();
    error_mutex.unlock();
    return output;
}
void PlaybackInstance::set_signal(uint16_t signal) {
    signal_mutex.lock();
    signals_occurred |= signal;
    signal_mutex.unlock();
}
uint16_t PlaybackInstance::handle_signals(uint16_t signals) {
    if (signal_mutex.try_lock()) {
        uint16_t output = signals_occurred & signals;
        signals_occurred &= ~output;
        signal_mutex.unlock();
        return output;
    } else {
        return PlaybackSignalNone;
    }
}
void PlaybackInstance::SetTempo(float tempo) {
    this->tempo = tempo;
    Update();
}
void PlaybackInstance::SetPitch(float pitch) {
    this->pitch = pitch;
    Update();
}
void PlaybackInstance::SetSpeed(float speed) {
    this->speed = speed;
    Update();
}
void PlaybackInstance::SetVolume(float volume) {
    this->volume = volume;
    Update();
}
float PlaybackInstance::GetTempo() {
    return tempo;
}
float PlaybackInstance::GetPitch() {
    return pitch;
}
float PlaybackInstance::GetSpeed() {
    return speed;
}
float PlaybackInstance::GetVolume() {
    return volume;
}