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

#include "waveform.h"
#include "utils.h"

#include <QDebug>
#include <QPainter>
#include <QResizeEvent>

//#define PAINT_EVENT_TRACE
#ifdef PAINT_EVENT_TRACE
#    define WAVEFORM_PAINT_DEBUG qDebug()
#else
#    define WAVEFORM_PAINT_DEBUG nullDebug()
#endif

Waveform::Waveform(QWidget *parent)
    : QWidget(parent),
      m_bufferPosition(0),
      m_bufferLength(0),
      m_audioPosition(0),
      m_active(false),
      m_tileLength(0),
      m_tileArrayStart(0),
      m_windowPosition(0),
      m_windowLength(0)
{
    setSizePolicy(QSizePolicy::Preferred, QSizePolicy::Fixed);
    setMinimumHeight(50);
}

Waveform::~Waveform()
{
    deletePixmaps();
}

void Waveform::paintEvent(QPaintEvent * /*event*/)
{
    QPainter painter(this);

    painter.fillRect(rect(), Qt::black);

    if (m_active) {
        WAVEFORM_PAINT_DEBUG << "Waveform::paintEvent"
                             << "windowPosition" << m_windowPosition << "windowLength"
                             << m_windowLength;
        qint64 pos = m_windowPosition;
        const qint64 windowEnd = m_windowPosition + m_windowLength;
        int destLeft = 0;
        int destRight = 0;
        while (pos < windowEnd) {
            const TilePoint point = tilePoint(pos);
            WAVEFORM_PAINT_DEBUG << "Waveform::paintEvent"
                                 << "pos" << pos << "tileIndex" << point.index << "positionOffset"
                                 << point.positionOffset << "pixelOffset" << point.pixelOffset;

            if (point.index != NullIndex) {
                const Tile &tile = m_tiles[point.index];
                if (tile.painted) {
                    const qint64 sectionLength =
                            qMin((m_tileLength - point.positionOffset), (windowEnd - pos));
                    Q_ASSERT(sectionLength > 0);

                    const int sourceRight = tilePixelOffset(point.positionOffset + sectionLength);
                    destRight = windowPixelOffset(pos - m_windowPosition + sectionLength);

                    QRect destRect = rect();
                    destRect.setLeft(destLeft);
                    destRect.setRight(destRight);

                    QRect sourceRect(QPoint(), m_pixmapSize);
                    sourceRect.setLeft(point.pixelOffset);
                    sourceRect.setRight(sourceRight);

                    WAVEFORM_PAINT_DEBUG << "Waveform::paintEvent"
                                         << "tileIndex" << point.index << "source"
                                         << point.pixelOffset << sourceRight << "dest" << destLeft
                                         << destRight;

                    painter.drawPixmap(destRect, *tile.pixmap, sourceRect);

                    destLeft = destRight;

                    if (point.index < m_tiles.count()) {
                        pos = tilePosition(point.index + 1);
                        WAVEFORM_PAINT_DEBUG << "Waveform::paintEvent"
                                             << "pos ->" << pos;
                    } else {
                        // Reached end of tile array
                        WAVEFORM_PAINT_DEBUG << "Waveform::paintEvent"
                                             << "reached end of tile array";
                        break;
                    }
                } else {
                    // Passed last tile which is painted
                    WAVEFORM_PAINT_DEBUG << "Waveform::paintEvent"
                                         << "tile" << point.index << "not painted";
                    break;
                }
            } else {
                // pos is past end of tile array
                WAVEFORM_PAINT_DEBUG << "Waveform::paintEvent"
                                     << "pos" << pos << "past end of tile array";
                break;
            }
        }

        WAVEFORM_PAINT_DEBUG << "Waveform::paintEvent"
                             << "final pos" << pos << "final x" << destRight;
    }
}

void Waveform::resizeEvent(QResizeEvent *event)
{
    if (event->size() != event->oldSize())
        createPixmaps(event->size());
}

void Waveform::initialize(const QAudioFormat &format, qint64 audioBufferSize,
                          qint64 windowDurationUs)
{
    WAVEFORM_DEBUG << "Waveform::initialize"
                   << "audioBufferSize" << audioBufferSize << "windowDurationUs"
                   << windowDurationUs;

    reset();

    m_format = format;

    // Calculate tile size
    m_tileLength = audioBufferSize;

    // Calculate window size
    m_windowLength = m_format.bytesForDuration(windowDurationUs);

    // Calculate number of tiles required
    int nTiles;
    if (m_tileLength > m_windowLength) {
        nTiles = 2;
    } else {
        nTiles = m_windowLength / m_tileLength + 1;
        if (m_windowLength % m_tileLength)
            ++nTiles;
    }

    WAVEFORM_DEBUG << "Waveform::initialize"
                   << "tileLength" << m_tileLength << "windowLength" << m_windowLength << "nTiles"
                   << nTiles;

    m_pixmaps.fill(nullptr, nTiles);
    m_tiles.resize(nTiles);

    createPixmaps(rect().size());

    m_active = true;
}

void Waveform::reset()
{
    WAVEFORM_DEBUG << "Waveform::reset";

    m_bufferPosition = 0;
    m_buffer = QByteArray();
    m_audioPosition = 0;
    m_format = QAudioFormat();
    m_active = false;
    deletePixmaps();
    m_tiles.clear();
    m_tileLength = 0;
    m_tileArrayStart = 0;
    m_windowPosition = 0;
    m_windowLength = 0;
}

void Waveform::bufferChanged(qint64 position, qint64 length, const QByteArray &buffer)
{
    WAVEFORM_DEBUG << "Waveform::bufferChanged"
                   << "audioPosition" << m_audioPosition << "bufferPosition" << position
                   << "bufferLength" << length;
    m_bufferPosition = position;
    m_bufferLength = length;
    m_buffer = buffer;
    paintTiles();
}

void Waveform::audioPositionChanged(qint64 position)
{
    WAVEFORM_DEBUG << "Waveform::audioPositionChanged"
                   << "audioPosition" << position << "bufferPosition" << m_bufferPosition
                   << "bufferLength" << m_bufferLength;

    if (position >= m_bufferPosition) {
        if (position + m_windowLength > m_bufferPosition + m_bufferLength)
            position = qMax(qint64(0), m_bufferPosition + m_bufferLength - m_windowLength);
        m_audioPosition = position;
        setWindowPosition(position);
    }
}

void Waveform::deletePixmaps()
{
    qDeleteAll(std::exchange(m_pixmaps, {}));
}

void Waveform::createPixmaps(const QSize &widgetSize)
{
    m_pixmapSize = widgetSize;
    m_pixmapSize.setWidth(qreal(widgetSize.width()) * m_tileLength / m_windowLength);

    WAVEFORM_DEBUG << "Waveform::createPixmaps"
                   << "widgetSize" << widgetSize << "pixmapSize" << m_pixmapSize;

    Q_ASSERT(m_tiles.count() == m_pixmaps.count());

    // (Re)create pixmaps
    for (auto &pixmap : m_pixmaps) {
        delete pixmap;
        pixmap = new QPixmap(m_pixmapSize);
    }

    // Update tile pixmap pointers, and mark for repainting
    for (int i = 0; i < m_tiles.count(); ++i) {
        m_tiles[i].pixmap = m_pixmaps[i];
        m_tiles[i].painted = false;
    }
}

void Waveform::setWindowPosition(qint64 position)
{
    WAVEFORM_DEBUG << "Waveform::setWindowPosition"
                   << "old" << m_windowPosition << "new" << position << "tileArrayStart"
                   << m_tileArrayStart;

    const qint64 oldPosition = m_windowPosition;
    m_windowPosition = position;

    if ((m_windowPosition >= oldPosition)
        && (m_windowPosition - m_tileArrayStart < (m_tiles.count() * m_tileLength))) {
        // Work out how many tiles need to be shuffled
        const qint64 offset = m_windowPosition - m_tileArrayStart;
        const int nTiles = offset / m_tileLength;
        shuffleTiles(nTiles);
    } else {
        resetTiles(m_windowPosition);
    }

    if (!paintTiles() && m_windowPosition != oldPosition)
        update();
}

qint64 Waveform::tilePosition(int index) const
{
    return m_tileArrayStart + index * m_tileLength;
}

Waveform::TilePoint Waveform::tilePoint(qint64 position) const
{
    TilePoint result;
    if (position >= m_tileArrayStart) {
        const qint64 tileArrayEnd = m_tileArrayStart + m_tiles.count() * m_tileLength;
        if (position < tileArrayEnd) {
            const qint64 offsetIntoTileArray = position - m_tileArrayStart;
            result.index = offsetIntoTileArray / m_tileLength;
            Q_ASSERT(result.index >= 0 && result.index <= m_tiles.count());
            result.positionOffset = offsetIntoTileArray % m_tileLength;
            result.pixelOffset = tilePixelOffset(result.positionOffset);
            Q_ASSERT(result.pixelOffset >= 0 && result.pixelOffset <= m_pixmapSize.width());
        }
    }

    return result;
}

int Waveform::tilePixelOffset(qint64 positionOffset) const
{
    Q_ASSERT(positionOffset >= 0 && positionOffset <= m_tileLength);
    const int result = (qreal(positionOffset) / m_tileLength) * m_pixmapSize.width();
    return result;
}

int Waveform::windowPixelOffset(qint64 positionOffset) const
{
    Q_ASSERT(positionOffset >= 0 && positionOffset <= m_windowLength);
    const int result = (qreal(positionOffset) / m_windowLength) * rect().width();
    return result;
}

bool Waveform::paintTiles()
{
    WAVEFORM_DEBUG << "Waveform::paintTiles";
    bool updateRequired = false;

    for (int i = 0; i < m_tiles.count(); ++i) {
        const Tile &tile = m_tiles[i];
        if (!tile.painted) {
            const qint64 tileStart = m_tileArrayStart + i * m_tileLength;
            const qint64 tileEnd = tileStart + m_tileLength;
            if (m_bufferPosition <= tileStart && m_bufferPosition + m_bufferLength >= tileEnd) {
                paintTile(i);
                updateRequired = true;
            }
        }
    }

    if (updateRequired)
        update();

    return updateRequired;
}

void Waveform::paintTile(int index)
{
    const qint64 tileStart = m_tileArrayStart + index * m_tileLength;

    WAVEFORM_DEBUG << "Waveform::paintTile"
                   << "index" << index << "bufferPosition" << m_bufferPosition << "bufferLength"
                   << m_bufferLength << "start" << tileStart << "end" << tileStart + m_tileLength;

    Q_ASSERT(m_bufferPosition <= tileStart);
    Q_ASSERT(m_bufferPosition + m_bufferLength >= tileStart + m_tileLength);

    Tile &tile = m_tiles[index];
    Q_ASSERT(!tile.painted);

    const qint16 *base = reinterpret_cast<const qint16 *>(m_buffer.constData());
    const qint16 *buffer = base + ((tileStart - m_bufferPosition) / 2);
    const int numSamples = m_tileLength / (2 * m_format.channelCount());

    QPainter painter(tile.pixmap);

    painter.fillRect(tile.pixmap->rect(), Qt::black);

    QPen pen(Qt::white);
    painter.setPen(pen);

    // Calculate initial PCM value
    qint16 previousPcmValue = 0;
    if (buffer > base)
        previousPcmValue = *(buffer - m_format.channelCount());

    // Calculate initial point
    const qreal previousRealValue = pcmToReal(previousPcmValue);
    const int originY = ((previousRealValue + 1.0) / 2) * m_pixmapSize.height();
    const QPoint origin(0, originY);

    QLine line(origin, origin);

    for (int i = 0; i < numSamples; ++i) {
        const qint16 *ptr = buffer + i * m_format.channelCount();

        const int offset = reinterpret_cast<const char *>(ptr) - m_buffer.constData();
        Q_ASSERT(offset >= 0);
        Q_ASSERT(offset < m_bufferLength);
        Q_UNUSED(offset);

        const qint16 pcmValue = *ptr;
        const qreal realValue = pcmToReal(pcmValue);

        const int x = tilePixelOffset(i * 2 * m_format.channelCount());
        const int y = ((realValue + 1.0) / 2) * m_pixmapSize.height();

        line.setP2(QPoint(x, y));
        painter.drawLine(line);
        line.setP1(line.p2());
    }

    tile.painted = true;
}

void Waveform::shuffleTiles(int n)
{
    WAVEFORM_DEBUG << "Waveform::shuffleTiles"
                   << "n" << n;

    while (n--) {
        Tile tile = m_tiles.first();
        tile.painted = false;
        m_tiles.erase(m_tiles.begin());
        m_tiles += tile;
        m_tileArrayStart += m_tileLength;
    }

    WAVEFORM_DEBUG << "Waveform::shuffleTiles"
                   << "tileArrayStart" << m_tileArrayStart;
}

void Waveform::resetTiles(qint64 newStartPos)
{
    WAVEFORM_DEBUG << "Waveform::resetTiles"
                   << "newStartPos" << newStartPos;

    QList<Tile>::iterator i = m_tiles.begin();
    for (; i != m_tiles.end(); ++i)
        i->painted = false;

    m_tileArrayStart = newStartPos;
}

#include "moc_waveform.cpp"
