// Copyright (C) 2017 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause

#include "audiooutput.h"

#include <QVBoxLayout>

Generator::Generator(const QAudioFormat &format, qint64 durationUs, int sampleRate)
{
    if (format.isValid())
        generateData(format, durationUs, sampleRate);
}

void Generator::start()
{
    open(QIODevice::ReadOnly);
}

void Generator::stop()
{
    m_pos = 0;
    close();
}

using namespace Qt::Literals::StringLiterals;
static QString sampleFormatToString(QAudioFormat::SampleFormat f)
{
    switch (f) {
    case QAudioFormat::UInt8: return u"UInt8"_s;
    case QAudioFormat::Int16: return u"Int16"_s;
    case QAudioFormat::Int32: return u"Int32"_s;
    case QAudioFormat::Float: return u"Float"_s;
    default:                  return u"Unknown"_s;
    }
}

static constexpr std::array allSupportedSampleRates{
    8'000, 11'025, 12'000, 16'000, 22'050, 24'000, 32'000, 44'100,
    48'000, 64'000, 88'200, 96'000, 128'000, 176'400, 192'000,
};

template<typename T>
static void setCurrentValue(QComboBox *box, const T &value) {
    int idx = box->findData(QVariant::fromValue(value));
    if (idx >= 0)
        box->setCurrentIndex(idx);
}

static void syncFormatGui(QComboBox *m_formatBox,
                          QComboBox *m_channelsBox,
                          QComboBox *m_rateBox,
                          const QAudioFormat &format) {
    setCurrentValue(m_formatBox, format.sampleFormat());
    setCurrentValue(m_rateBox, format.sampleRate());
    setCurrentValue(m_channelsBox, format.channelCount());
}

void Generator::generateData(const QAudioFormat &format, qint64 durationUs, int sampleRate)
{
    const int channelBytes = format.bytesPerSample();
    [[maybe_unused]] const int sampleBytes = format.channelCount() * channelBytes;
    Q_ASSERT(sampleBytes != 0);
    qint64 length = format.bytesForDuration(durationUs);
    Q_ASSERT(length % sampleBytes == 0);
    Q_UNUSED(sampleBytes); // suppress warning in release builds

    m_buffer.resize(length);
    unsigned char *ptr = reinterpret_cast<unsigned char *>(m_buffer.data());
    int sampleIndex = 0;

    while (length) {
        // Produces value (-1..1)
        const qreal x = qSin(2 * M_PI * sampleRate * qreal(sampleIndex++ % format.sampleRate())
                             / format.sampleRate());
        for (int i = 0; i < format.channelCount(); ++i) {
            switch (format.sampleFormat()) {
            case QAudioFormat::UInt8:
                *reinterpret_cast<quint8 *>(ptr) = static_cast<quint8>((1.0 + x) / 2 * 255);
                break;
            case QAudioFormat::Int16:
                *reinterpret_cast<qint16 *>(ptr) = static_cast<qint16>(x * 32767);
                break;
            case QAudioFormat::Int32:
                *reinterpret_cast<qint32 *>(ptr) =
                        static_cast<qint32>(x * std::numeric_limits<qint32>::max());
                break;
            case QAudioFormat::Float:
                *reinterpret_cast<float *>(ptr) = x;
                break;
            default:
                break;
            }

            ptr += channelBytes;
            length -= channelBytes;
        }
    }
}

qint64 Generator::readData(char *data, qint64 len)
{
    qint64 total = 0;
    if (!m_buffer.isEmpty()) {
        while (len - total > 0) {
            const qint64 chunk = qMin((m_buffer.size() - m_pos), len - total);
            memcpy(data + total, m_buffer.constData() + m_pos, chunk);
            m_pos = (m_pos + chunk) % m_buffer.size();
            total += chunk;
        }
    }
    return total;
}

qint64 Generator::writeData(const char *data, qint64 len)
{
    Q_UNUSED(data);
    Q_UNUSED(len);

    return 0;
}

qint64 Generator::bytesAvailable() const
{
    return m_buffer.size() + QIODevice::bytesAvailable();
}

AudioTest::AudioTest() : m_devices(new QMediaDevices(this)), m_pushTimer(new QTimer(this))
{
    initializeWindow();
    initializeAudio(m_devices->defaultAudioOutput());
}

AudioTest::~AudioTest()
{
    m_pushTimer->stop();
    cleanupAudioSink();
}

void AudioTest::initializeWindow()
{
    QWidget *window = new QWidget;
    QVBoxLayout *layout = new QVBoxLayout;

    m_deviceBox = new QComboBox(this);
    const QAudioDevice &defaultDeviceInfo = m_devices->defaultAudioOutput();
    m_deviceBox->addItem(defaultDeviceInfo.description(), QVariant::fromValue(defaultDeviceInfo));
    for (auto &deviceInfo : m_devices->audioOutputs()) {
        if (deviceInfo != defaultDeviceInfo)
            m_deviceBox->addItem(deviceInfo.description(), QVariant::fromValue(deviceInfo));
    }
    connect(m_deviceBox, &QComboBox::currentIndexChanged, this, &AudioTest::deviceChanged);
    connect(m_devices, &QMediaDevices::audioOutputsChanged, this, &AudioTest::updateAudioDevices);
    layout->addWidget(m_deviceBox);

    m_modeButton = new QPushButton(this);
    connect(m_modeButton, &QPushButton::clicked, this, &AudioTest::toggleMode);
    layout->addWidget(m_modeButton);

    m_suspendResumeButton = new QPushButton(this);
    connect(m_suspendResumeButton, &QPushButton::clicked, this, &AudioTest::toggleSuspendResume);
    layout->addWidget(m_suspendResumeButton);

    QHBoxLayout *volumeBox = new QHBoxLayout;
    m_volumeLabel = new QLabel;
    m_volumeLabel->setText(tr("Volume:"));
    m_volumeSlider = new QSlider(Qt::Horizontal);
    m_volumeSlider->setMinimum(0);
    m_volumeSlider->setMaximum(100);
    m_volumeSlider->setSingleStep(10);
    connect(m_volumeSlider, &QSlider::valueChanged, this, &AudioTest::volumeChanged);
    volumeBox->addWidget(m_volumeLabel);
    volumeBox->addWidget(m_volumeSlider);
    layout->addLayout(volumeBox);

    // Sample Format selector
    QHBoxLayout *formatBox = new QHBoxLayout;
    QLabel *formatLabel = new QLabel;
    formatLabel->setText(tr("Sample Format:"));
    m_formatBox = new QComboBox(this);

    // populate the sample format combo box
    // supportedSampleFormats returns enum so we cast it to string.
    const auto formats = defaultDeviceInfo.supportedSampleFormats();
    for (const QAudioFormat::SampleFormat fmt : formats)
        m_formatBox->addItem(sampleFormatToString(fmt), QVariant::fromValue(fmt));

    //Sample rate button
    QLabel *rateLabel = new QLabel;
    rateLabel->setText(tr("Sample Rate:"));
    m_rateBox = new QComboBox(this);

    // populate from the hardcoded list in this cpp file
    for (int rate : allSupportedSampleRates)
        m_rateBox->addItem(QString::number(rate), rate);

    // setting channel count
    QLabel *chLabel = new QLabel;
    chLabel->setText(tr("Channels:"));
    m_channelsBox = new QComboBox(this);

    // populate from device min..max
    int minCh = defaultDeviceInfo.minimumChannelCount();
    int maxCh = defaultDeviceInfo.maximumChannelCount();
    for (int ch = minCh; ch <= maxCh; ++ch)
        m_channelsBox->addItem(QString::number(ch), ch);

    // set the value of the boxes to be the initial values of the format.
    const QAudioFormat pref = defaultDeviceInfo.preferredFormat();
    syncFormatGui(m_formatBox, m_channelsBox, m_rateBox, pref);

    for (auto box : {m_channelsBox, m_rateBox, m_formatBox}) {
        connect(box, &QComboBox::activated, this, [this, box]() {
            formatChanged(box);
        });
    }

    // add all to the same row
    formatBox->addWidget(formatLabel);
    formatBox->addWidget(m_formatBox);
    formatBox->addSpacing(12);
    formatBox->addWidget(rateLabel);
    formatBox->addWidget(m_rateBox);
    formatBox->addSpacing(12);
    formatBox->addWidget(chLabel);
    formatBox->addWidget(m_channelsBox);

    layout->addLayout(formatBox);
    window->setLayout(layout);

    setCentralWidget(window);
    window->show();

    connect(this, &AudioTest::pullModeChanged, this, [&] {
        if (m_pullMode)
            m_modeButton->setText(tr("Enable push mode"));
        else
            m_modeButton->setText(tr("Enable pull mode"));
    });
    emit pullModeChanged();
}

void AudioTest::initializeAudio(const QAudioDevice &deviceInfo)
{
    QAudioFormat format = deviceInfo.preferredFormat();
    applyAudioFormat(deviceInfo, format);
}

void AudioTest::applyAudioFormat(const QAudioDevice &deviceInfo, const QAudioFormat &format)
{
    // keep previous format to roll back if changing the audio format fails
    const QAudioFormat prevFmt = m_audioSink ? m_audioSink->format() : deviceInfo.preferredFormat();

    if (m_audioSink)
        m_audioSink->disconnect(this);

    // rebuild generator and sink with the requested format
    const int durationSeconds = 1;
    const int toneSampleRateHz = 600;
    m_generator = std::make_unique<Generator>(format, durationSeconds * 1000000, toneSampleRateHz);
    m_audioSink = std::make_unique<QAudioSink>(deviceInfo, format);
    m_audioSink->setVolume(0.25f); // roughly -12dB

    m_generator->start();

    // handle startup/runtime errors and success negotiation
    connect(m_audioSink.get(), &QAudioSink::stateChanged, this,
            [this, prevFmt](QAudio::State s) {
                const auto err = m_audioSink->error();

                // startup failure (format rejected or device unavailable)
                if (err == QAudio::OpenError && s == QAudio::StoppedState) {
                    QMessageBox::warning(this, tr("Audio start failed"),
                                         tr("Device rejected the format or is unavailable."));
                    auto dev = m_deviceBox->currentData().value<QAudioDevice>();
                    applyAudioFormat(dev, prevFmt);
                    return;
                }

                // runtime I/O or fatal device error (disconnects, etc.)
                if (err == QAudio::IOError || err == QAudio::FatalError) {
                    QMessageBox::warning(this, tr("Audio error"),
                                    tr("Audio device error. Restoring previous format/device."));
                    auto dev = m_deviceBox->currentData().value<QAudioDevice>();
                    applyAudioFormat(dev, prevFmt);
                    return;
                }

                // reflect negotiated format on successful activation
                if (s == QAudio::ActiveState) {
                    syncFormatGui(m_formatBox, m_channelsBox, m_rateBox, m_audioSink->format());
                }

                // reset suspend/resume to new audiosink
                m_suspendResumeButton->setText(tr("Suspend playback"));
                if (s == QAudio::SuspendedState) {
                    m_suspendResumeButton->setText(tr("Resume playback"));
                }
            });

    // set initial volume and kick the stream
    qreal initialVolume = QAudio::convertVolume(m_audioSink->volume(),
                                                QAudio::LinearVolumeScale,
                                                QAudio::LogarithmicVolumeScale);
    m_volumeSlider->setValue(qRound(initialVolume * 100));

    restartAudioStream();
}

void AudioTest::deviceChanged(int index)
{
    cleanupAudioSink();

    QAudioDevice dev = m_deviceBox->itemData(index).value<QAudioDevice>();

    // formats
    m_formatBox->clear();
    const auto formats = dev.supportedSampleFormats();
    for (const QAudioFormat::SampleFormat sf : formats)
        m_formatBox->addItem(sampleFormatToString(sf), QVariant::fromValue(sf));

    // channels
    m_channelsBox->clear();
    for (int ch = dev.minimumChannelCount(); ch <= dev.maximumChannelCount(); ++ch)
        m_channelsBox->addItem(QString::number(ch), ch);

    initializeAudio(m_deviceBox->itemData(index).value<QAudioDevice>());
}

void AudioTest::volumeChanged(int value)
{
    qreal linearVolume = QAudio::convertVolume(value / qreal(100),
                                               QAudio::LogarithmicVolumeScale,
                                               QAudio::LinearVolumeScale);

    m_audioSink->setVolume(linearVolume);
}

void AudioTest::formatChanged(QComboBox *box)
{
    QAudioDevice device = m_deviceBox->currentData().value<QAudioDevice>();
    QAudioFormat newFormat = m_audioSink->format();

    if (box == m_formatBox) {
        newFormat.setSampleFormat(
            static_cast<QAudioFormat::SampleFormat>(box->currentData().toInt()));
    } else if (box == m_rateBox) {
        newFormat.setSampleRate(box->currentData().toInt());
    } else if (box == m_channelsBox) {
        newFormat.setChannelCount(box->currentData().toInt());
    }

    applyAudioFormat(device, newFormat);
}

void AudioTest::updateAudioDevices()
{
    m_deviceBox->clear();
    const QList<QAudioDevice> devices = m_devices->audioOutputs();
    for (const QAudioDevice &deviceInfo : devices)
        m_deviceBox->addItem(deviceInfo.description(), QVariant::fromValue(deviceInfo));
}

void AudioTest::toggleMode()
{
    m_pullMode = !m_pullMode;
    emit pullModeChanged();

    restartAudioStream();
}

void AudioTest::restartAudioStream()
{
    m_pushTimer->stop();
    // Reset audiosink
    m_audioSink->reset();

    qreal initialVolume = QAudio::convertVolume(m_audioSink->volume(),
                                                QAudio::LinearVolumeScale,
                                                QAudio::LogarithmicVolumeScale);
    m_volumeSlider->setValue(qRound(initialVolume * 100));

    if (m_pullMode) {
        // pull mode: QAudioSink pulls from Generator as needed
        m_audioSink->start(m_generator.get());
    } else {
        // push mode: periodically push to QAudioSink using a timer
        auto io = m_audioSink->start();
        m_pushTimer->disconnect();

        connect(m_pushTimer, &QTimer::timeout, this, [this, io]() {
            if (m_audioSink->state() == QAudio::StoppedState)
                return;

            int len = m_audioSink->bytesFree();
            QByteArray buffer(len, 0);
            len = m_generator->read(buffer.data(), len);
            if (len)
                io->write(buffer.data(), len);
        });

        m_pushTimer->start(10);
    }
}

void AudioTest::toggleSuspendResume()
{
    switch (m_audioSink->state()) {
    case QAudio::SuspendedState:
        m_audioSink->resume();
        return;
    case QAudio::ActiveState:
        m_audioSink->suspend();
        return;

    default:
        return;
    }
}

void AudioTest::cleanupAudioSink()
{
    if (m_audioSink) {
        m_audioSink->stop();
        m_audioSink->disconnect(this);
    }
    m_audioSink.reset();
    m_generator.reset();
}

#include "moc_audiooutput.cpp"
