/* ============================================================
 *
 * 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 "SphericalScanlineTextureMapper.h"

// C++ includes

#include <cmath>

// Qt includes

#include <qmath.h>
#include <QRunnable>

// Local includes

#include "GeoPainter.h"
#include "GeoDataPolygon.h"
#include "Quaternion.h"
#include "ScanlineTextureMapperContext.h"
#include "StackedTileLoader.h"
#include "StackedTile.h"
#include "TextureColorizer.h"
#include "ViewportParams.h"
#include "MathHelper.h"
#include "digikam_debug.h"

namespace Marble
{

class Q_DECL_HIDDEN SphericalScanlineTextureMapper::RenderJob : public QRunnable
{
public:

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

    void run() override;

private:

    StackedTileLoader* const    m_tileLoader  = nullptr;
    const int                   m_tileLevel;
    QImage* const               m_canvasImage = nullptr;
    const ViewportParams* const m_viewport    = nullptr;
    const MapQuality            m_mapQuality;
    int const                   m_yTop;
    int const                   m_yBottom;
};

SphericalScanlineTextureMapper::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_yTop(yTop),
      m_yBottom(yBottom)
{
}

SphericalScanlineTextureMapper::SphericalScanlineTextureMapper(StackedTileLoader* tileLoader)
    : TextureMapperInterface()
    , m_tileLoader(tileLoader)
    , m_radius(0)
    , m_threadPool()
{
}

void SphericalScanlineTextureMapper::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;
    }

    const int radius = viewport->radius();

    QRect rect(viewport->width() / 2 - radius, viewport->height() / 2 - radius,
               2 * radius, 2 * radius);
    rect = rect.intersected(dirtyRect);
    painter->drawImage(rect, m_canvasImage, rect);
}

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

    // Initialize needed constants:

    const int imageHeight = m_canvasImage.height();
    const qint64  radius      = viewport->radius();

    // Calculate the actual y-range of the map on the screen
    const int skip = (mapQuality == LowQuality) ? 1
                     : 0;
    const int yTop = (imageHeight / 2 - radius >= 0) ? imageHeight / 2 - radius
                     : 0;
    const int yBottom = (yTop == 0) ? imageHeight - skip
                        : yTop + radius + radius - skip;

    const int numThreads = m_threadPool.maxThreadCount();
    const int yStep = qCeil(qreal(yBottom - yTop) / qreal(numThreads));

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

    m_threadPool.waitForDone();

    m_tileLoader->cleanupTilehash();
}

void SphericalScanlineTextureMapper::RenderJob::run()
{
    const int imageHeight = m_canvasImage->height();
    const int imageWidth  = m_canvasImage->width();
    const qint64  radius  = m_viewport->radius();
    const qreal  inverseRadius = 1.0 / (qreal)(radius);

    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 north pole position to decrease pole distortion later on
    Quaternion northPole = Quaternion::fromSpherical(0.0, M_PI * 0.5);
    northPole.rotateAroundAxis(m_viewport->planetAxis().inverse());
    const int northPoleX = imageWidth / 2 + (int)(radius * northPole.v[Q_X]);
    const int northPoleY = imageHeight / 2 - (int)(radius * northPole.v[Q_Y]);

    // Calculate axis matrix to represent the planet's rotation.
    matrix  planetAxisMatrix;
    m_viewport->planetAxis().toMatrix(planetAxisMatrix);

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

    ScanlineTextureMapperContext context(m_tileLoader, m_tileLevel);
    qreal  lon = 0.0;
    qreal  lat = 0.0;

    // Scanline based algorithm to texture map a sphere
    for (int y = m_yTop; y < m_yBottom ; ++y)
    {

        // Evaluate coordinates for the 3D position vector of the current pixel
        const qreal qy = inverseRadius * (qreal)(imageHeight / 2 - y);
        const qreal qr = 1.0 - qy * qy;

        // rx is the radius component in x direction
        const int rx = (int)sqrt((qreal)(radius * radius
                                         - ((y - imageHeight / 2)
                                            * (y - imageHeight / 2))));

        // Calculate the actual x-range of the map within the current scanline.
        //
        // If the circular border of the earth disk is still visible then xLeft
        // equals the scanline position of the most left pixel that gets covered
        // by the earth disk. In terms of math this equals the half image width minus
        // the radius component on the current scanline in x direction ("rx").
        //
        // If the zoom factor is high enough then the whole screen gets covered
        // by the earth and the border of the earth disk isn't visible anymore.
        // In that situation xLeft equals zero.
        // For xRight the situation is similar.

        const int xLeft  = (imageWidth / 2 - rx > 0) ? imageWidth / 2 - rx
                           : 0;
        const int xRight = (imageWidth / 2 - rx > 0) ? xLeft + rx + rx
                           : imageWidth;

        QRgb* scanLine = reinterpret_cast<QRgb*>(m_canvasImage->scanLine(y)) + xLeft;

        const int xIpLeft  = (imageWidth / 2 - rx > 0) ? n * (int)(xLeft / n + 1)
                             : 1;
        const int xIpRight = (imageWidth / 2 - rx > 0) ? n * (int)(xRight / n - 1)
                             : n * (int)(xRight / n - 1) + 1;

        // Decrease pole distortion due to linear approximation ( y-axis )
        bool crossingPoleArea = false;

        if (northPole.v[Q_Z] > 0
            && northPoleY - (n * 0.75) <= y
            && northPoleY + (n * 0.75) >= y)
        {
            crossingPoleArea = true;
        }

        int ncount = 0;

        for (int x = xLeft; x < xRight; ++x)
        {
            // Prepare for interpolation

            const int leftInterval = xIpLeft + ncount * n;

            bool interpolate = false;

            if (x >= xIpLeft && x <= xIpRight)
            {

                // Decrease pole distortion due to linear approximation ( x-axis )
                //                qCDebug(DIGIKAM_MARBLE_LOG) << QString("NorthPole X: %1, LeftInterval: %2").arg( northPoleX ).arg( leftInterval );
                if (crossingPoleArea
                    && northPoleX >= leftInterval + n
                    && northPoleX < leftInterval + 2 * n
                    && x < leftInterval + 3 * n)
                {
                    interpolate = false;
                }

                else
                {
                    x += n - 1;
                    interpolate = !printQuality;
                    ++ncount;
                }
            }

            else
            {
                interpolate = false;
            }

            // Evaluate more coordinates for the 3D position vector of
            // the current pixel.
            const qreal qx = (qreal)(x - imageWidth / 2) * inverseRadius;
            const qreal qr2z = qr - qx * qx;
            const qreal qz = (qr2z > 0.0) ? sqrt(qr2z) : 0.0;

            // Create Quaternion from vector coordinates and rotate it
            // around globe axis
            Quaternion qpos(0.0, qx, qy, qz);
            qpos.rotateAroundAxis(planetAxisMatrix);

            qpos.getSpherical(lon, lat);
            //            qCDebug(DIGIKAM_MARBLE_LOG) << QString("lon: %1 lat: %2").arg(lon).arg(lat);
            // Approx for n-1 out of n pixels within the boundary of
            // xIpLeft to xIpRight

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

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

                scanLine += (n - 1);
            }

            //          Comment out the pixelValue line and run Marble if you want
            //          to understand the interpolation:

            //          Uncomment the crossingPoleArea line to check precise
            //          rendering around north pole:

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

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

            ++scanLine;
        }

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

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

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

} // namespace Marble
