// SPDX-License-Identifier: LGPL-2.1-or-later
//
// SPDX-FileCopyrightText: 2007 Carlos Licea <carlos _licea@hotmail.com>
// SPDX-FileCopyrightText: 2011 Bernhard Beschow <bbeschow@cs.tu-berlin.de>
//

// local
#include "EquirectScanlineTextureMapper.h"

// posix
#include <cmath>

// Qt
#include <QRunnable>

// Marble
#include "AbstractProjection.h"
#include "GeoPainter.h"
#include "MarbleDebug.h"
#include "ScanlineTextureMapperContext.h"
#include "StackedTileLoader.h"
#include "TextureColorizer.h"
#include "ViewportParams.h"

using namespace Marble;

class 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 = (QRgb *)(m_canvasImage.scanLine(clearStart));
    QRgb *const itClearEnd = (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 = (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;
        }
    }
}
