/* ============================================================
 *
 * This file is a part of digiKam project
 * https://www.digikam.org
 *
 * Date        : 2023-05-15
 * Description : geolocation engine based on Marble.
 *               (c) 2007-2022 Marble Team
 *               https://invent.kde.org/education/marble/-/raw/master/data/credits_authors.html
 *
 * SPDX-FileCopyrightText: 2023-2024 by Gilles Caulier <caulier dot gilles at gmail dot com>
 *
 * SPDX-License-Identifier: LGPL-2.1-or-later
 *
 * ============================================================ */

#include"EquirectScanlineTextureMapper.h"

// C++ includes

#include <cmath>

// Qt includes

#include <QRunnable>

// Local includes

#include "GeoPainter.h"
#include "ScanlineTextureMapperContext.h"
#include "StackedTileLoader.h"
#include "TextureColorizer.h"
#include "ViewportParams.h"
#include "AbstractProjection.h"
#include "digikam_debug.h"

namespace Marble
{

class Q_DECL_HIDDEN EquirectScanlineTextureMapper::RenderJob : public QRunnable
{
public:

    RenderJob(StackedTileLoader* tileLoader, int tileLevel, QImage* canvasImage, const ViewportParams* viewportParams, MapQuality mapQuality, int yTop, int yBottom);

    void run() override;

private:

    StackedTileLoader* const m_tileLoader;
    const int m_tileLevel;
    QImage* const m_canvasImage;
    const ViewportParams* const m_viewport;
    const MapQuality m_mapQuality;
    const int m_yPaintedTop;
    const int m_yPaintedBottom;
};

EquirectScanlineTextureMapper::RenderJob::RenderJob(StackedTileLoader* tileLoader, int tileLevel, QImage* canvasImage, const ViewportParams* viewport, MapQuality mapQuality, int yTop, int yBottom)
    : m_tileLoader(tileLoader),
      m_tileLevel(tileLevel),
      m_canvasImage(canvasImage),
      m_viewport(viewport),
      m_mapQuality(mapQuality),
      m_yPaintedTop(yTop),
      m_yPaintedBottom(yBottom)
{
}

EquirectScanlineTextureMapper::EquirectScanlineTextureMapper(StackedTileLoader* tileLoader)
    : TextureMapperInterface(),
      m_tileLoader(tileLoader),
      m_radius(0),
      m_oldYPaintedTop(0)
{
}

void EquirectScanlineTextureMapper::mapTexture(GeoPainter* painter,
                                               const ViewportParams* viewport,
                                               int tileZoomLevel,
                                               const QRect& dirtyRect,
                                               TextureColorizer* texColorizer)
{
    if (m_canvasImage.size() != viewport->size() || m_radius != viewport->radius())
    {
        const QImage::Format optimalFormat = ScanlineTextureMapperContext::optimalCanvasImageFormat(viewport);

        if (m_canvasImage.size() != viewport->size() || m_canvasImage.format() != optimalFormat)
        {
            m_canvasImage = QImage(viewport->size(), optimalFormat);
        }

        if (!viewport->mapCoversViewport())
        {
            m_canvasImage.fill(0);
        }

        m_radius = viewport->radius();
        m_repaintNeeded = true;
    }

    if (m_repaintNeeded)
    {
        mapTexture(viewport, tileZoomLevel, painter->mapQuality());

        if (texColorizer)
        {
            texColorizer->colorize(&m_canvasImage, viewport, painter->mapQuality());
        }

        m_repaintNeeded = false;
    }

    painter->drawImage(dirtyRect, m_canvasImage, dirtyRect);
}

void EquirectScanlineTextureMapper::mapTexture(const ViewportParams* viewport, int tileZoomLevel, MapQuality mapQuality)
{
    // Reset backend
    m_tileLoader->resetTilehash();

    // Initialize needed constants:

    const int imageHeight = m_canvasImage.height();

    // Calculate y-range the represented by the center point, yTop and
    // what actually can be painted

    qreal realYTop, realYBottom, dummyX;
    GeoDataCoordinates yNorth(0, viewport->currentProjection()->maxLat(), 0);
    GeoDataCoordinates ySouth(0, viewport->currentProjection()->minLat(), 0);
    viewport->screenCoordinates(yNorth, dummyX, realYTop);
    viewport->screenCoordinates(ySouth, dummyX, realYBottom);

    const int yTop     = qBound(qreal(0.0), realYTop, qreal(imageHeight));
    int yPaintedTop    = yTop;
    int yPaintedBottom = qBound(qreal(0.0), realYBottom, qreal(imageHeight));

    yPaintedTop = qBound(0, yPaintedTop, imageHeight);
    yPaintedBottom = qBound(0, yPaintedBottom, imageHeight);

    const int numThreads = m_threadPool.maxThreadCount();
    const int yStep = (yPaintedBottom - yPaintedTop) / numThreads;

    for (int i = 0; i < numThreads; ++i)
    {
        const int yStart = yPaintedTop +  i      * yStep;
        const int yEnd   = (i == numThreads - 1) ? yPaintedBottom : yPaintedTop + (i + 1) * yStep;
        QRunnable* const job = new RenderJob(m_tileLoader, tileZoomLevel, &m_canvasImage, viewport, mapQuality, yStart, yEnd);
        m_threadPool.start(job);
    }

    // Remove unused lines
    const int clearStart = (yPaintedTop - m_oldYPaintedTop <= 0) ? yPaintedBottom : 0;
    const int clearStop  = (yPaintedTop - m_oldYPaintedTop <= 0) ? imageHeight  : yTop;

    QRgb* const itClearBegin = reinterpret_cast<QRgb*>(m_canvasImage.scanLine(clearStart));
    QRgb* const itClearEnd   = reinterpret_cast<QRgb*>(m_canvasImage.scanLine(clearStop));

    for (QRgb* it = itClearBegin; it < itClearEnd; ++it)
    {
        *(it) = 0;
    }

    m_threadPool.waitForDone();

    m_oldYPaintedTop = yPaintedTop;

    m_tileLoader->cleanupTilehash();
}

void EquirectScanlineTextureMapper::RenderJob::run()
{
    // Scanline based algorithm to do texture mapping

    const int imageHeight = m_canvasImage->height();
    const int imageWidth  = m_canvasImage->width();
    const qint64  radius  = m_viewport->radius();
    // Calculate how many degrees are being represented per pixel.
    const qreal rad2Pixel = (qreal)(2 * radius) / M_PI;
    const float pixel2Rad = 1.0 / rad2Pixel; // FIXME changing to qreal may crash Marble when the equator is visible

    const bool interlaced   = (m_mapQuality == LowQuality);
    const bool highQuality  = (m_mapQuality == HighQuality
                               || m_mapQuality == PrintQuality);
    const bool printQuality = (m_mapQuality == PrintQuality);

    // Evaluate the degree of interpolation
    const int n = ScanlineTextureMapperContext::interpolationStep(m_viewport, m_mapQuality);

    // Calculate translation of center point
    const qreal centerLon = m_viewport->centerLongitude();
    const qreal centerLat = m_viewport->centerLatitude();

    const int yCenterOffset = (int)(centerLat * rad2Pixel);

    const int yTop = imageHeight / 2 - radius + yCenterOffset;

    qreal leftLon = + centerLon - (imageWidth / 2 * pixel2Rad);

    while (leftLon < -M_PI)
    {
        leftLon += 2 * M_PI;
    }

    while (leftLon >  M_PI)
    {
        leftLon -= 2 * M_PI;
    }

    const int maxInterpolationPointX = n * (int)(imageWidth / n - 1) + 1;

    // initialize needed variables that are modified during texture mapping:

    ScanlineTextureMapperContext context(m_tileLoader, m_tileLevel);

    // Scanline based algorithm to do texture mapping

    for (int y = m_yPaintedTop; y < m_yPaintedBottom; ++y)
    {
        QRgb* scanLine = reinterpret_cast<QRgb*>(m_canvasImage->scanLine(y));

        qreal lon = leftLon;
        const qreal lat = M_PI / 2 - (y - yTop) * pixel2Rad;

        for (int x = 0; x < imageWidth; ++x)
        {

            // Prepare for interpolation
            bool interpolate = false;

            if (x > 0 && x <= maxInterpolationPointX)
            {
                x += n - 1;
                lon += (n - 1) * pixel2Rad;
                interpolate = !printQuality;
            }

            else
            {
                interpolate = false;
            }

            if (lon < -M_PI)
            {
                lon += 2 * M_PI;
            }

            if (lon >  M_PI)
            {
                lon -= 2 * M_PI;
            }

            if (interpolate)
            {
                if (highQuality)
                {
                    context.pixelValueApproxF(lon, lat, scanLine, n);
                }

                else
                {
                    context.pixelValueApprox(lon, lat, scanLine, n);
                }

                scanLine += (n - 1);
            }

            if (x < imageWidth)
            {
                if (highQuality)
                {
                    context.pixelValueF(lon, lat, scanLine);
                }

                else
                {
                    context.pixelValue(lon, lat, scanLine);
                }
            }

            ++scanLine;
            lon += pixel2Rad;
        }

        // copy scanline to improve performance
        if (interlaced && y + 1 < m_yPaintedBottom)
        {

            const int pixelByteSize = m_canvasImage->bytesPerLine() / imageWidth;

            memcpy(m_canvasImage->scanLine(y + 1),
                   m_canvasImage->scanLine(y),
                   imageWidth * pixelByteSize);
            ++y;
        }
    }
}

} // namespace Marble
