/* ============================================================
 *
 * 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: 2023-2026 by Gilles Caulier <caulier dot gilles at gmail dot com>
 *
 * SPDX-License-Identifier: LGPL-2.1-or-later
 *
 * ============================================================ */

#include "CylindricalProjection.h"
#include "CylindricalProjection_p.h"

// Qt includes

#include <QPainterPath>

// Local includes

#include "GeoDataLinearRing.h"
#include "GeoDataLineString.h"
#include "GeoDataCoordinates.h"
#include "GeoDataLatLonAltBox.h"
#include "ViewportParams.h"

// Maximum amount of nodes that are created automatically between actual nodes.
static const int maxTessellationNodes = 200;

namespace Marble
{

CylindricalProjection::CylindricalProjection()
    : AbstractProjection(new CylindricalProjectionPrivate(this))
{
}

CylindricalProjection::CylindricalProjection(CylindricalProjectionPrivate* dd)
    : AbstractProjection(dd)
{
}

CylindricalProjection::~CylindricalProjection()
{
}

CylindricalProjectionPrivate::CylindricalProjectionPrivate(CylindricalProjection* parent)
    : AbstractProjectionPrivate(parent),
      q_ptr(parent)
{
}

QPainterPath CylindricalProjection::mapShape(const ViewportParams* viewport) const
{
    // Convenience variables
    int  width  = viewport->width();
    int  height = viewport->height();

    qreal  yTop;
    qreal  yBottom;
    qreal  xDummy;

    // Get the top and bottom coordinates of the projected map.
    screenCoordinates(0.0, maxLat(), viewport, xDummy, yTop);
    screenCoordinates(0.0, minLat(), viewport, xDummy, yBottom);

    // Don't let the map area be outside the image
    if (yTop < 0)
    {
        yTop = 0;
    }

    if (yBottom > height)
    {
        yBottom =  height;
    }

    QPainterPath mapShape;
    mapShape.addRect(
        0,
        yTop,
        width,
        yBottom - yTop);

    return mapShape;
}

bool CylindricalProjection::screenCoordinates(const GeoDataLineString& lineString,
                                              const ViewportParams* viewport,
                                              QVector<QPolygonF*>& polygons) const
{

    Q_D(const CylindricalProjection);

    // Compare bounding box size of the line string with the angularResolution
    // Immediately return if the latLonAltBox is smaller.
    if (!viewport->resolves(lineString.latLonAltBox()))
    {
        //    qCDebug(DIGIKAM_GEOENGINE_LOG) << "Object too small to be resolved";
        return false;
    }

    QVector<QPolygonF*> subPolygons;
    d->lineStringToPolygon(lineString, viewport, subPolygons);

    polygons << subPolygons;
    return polygons.isEmpty();
}

int CylindricalProjectionPrivate::tessellateLineSegment(const GeoDataCoordinates& aCoords,
                                                        qreal ax, qreal ay,
                                                        const GeoDataCoordinates& bCoords,
                                                        qreal bx, qreal by,
                                                        QVector<QPolygonF*>& polygons,
                                                        const ViewportParams* viewport,
                                                        TessellationFlags f,
                                                        int mirrorCount,
                                                        qreal repeatDistance) const
{
    // We take the manhattan length as a distance approximation
    // that can be too big by a factor of sqrt(2)
    qreal distance = fabs((bx - ax)) + fabs((by - ay));

#ifdef SAFE_DISTANCE

    // Interpolate additional nodes if the line segment that connects the
    // current or previous nodes might cross the viewport.
    // The latter can pretty safely be excluded for most projections if both points
    // are located on the same side relative to the viewport boundaries and if they are
    // located more than half the line segment distance away from the viewport.
    const qreal safeDistance = - 0.5 * distance;

    if (!(bx < safeDistance && ax < safeDistance)
        || !(by < safeDistance && ay < safeDistance)
        || !(bx + safeDistance > viewport->width()
             && ax + safeDistance > viewport->width())
        || !(by + safeDistance > viewport->height()
             && ay + safeDistance > viewport->height())
       )
    {

#endif

        int maxTessellationFactor = viewport->radius() < 20000 ? 10 : 20;
        int const finalTessellationPrecision = qBound(2, viewport->radius() / 200, maxTessellationFactor) * tessellationPrecision;

        // Let the line segment follow the spherical surface
        // if the distance between the previous point and the current point
        // on screen is too big
        if (distance > finalTessellationPrecision)
        {
            const int tessellatedNodes = qMin<int>(distance / finalTessellationPrecision, maxTessellationNodes);

            mirrorCount = processTessellation(aCoords, bCoords,
                                              tessellatedNodes,
                                              polygons,
                                              viewport,
                                              f,
                                              mirrorCount,
                                              repeatDistance);
        }

        else
        {
            mirrorCount = crossDateLine(aCoords, bCoords, bx, by, polygons, mirrorCount, repeatDistance);
        }

#ifdef SAFE_DISTANCE

    }

#endif

    return mirrorCount;
}

int CylindricalProjectionPrivate::processTessellation(const GeoDataCoordinates& previousCoords,
                                                      const GeoDataCoordinates& currentCoords,
                                                      int tessellatedNodes,
                                                      QVector<QPolygonF*>& polygons,
                                                      const ViewportParams* viewport,
                                                      TessellationFlags f,
                                                      int mirrorCount,
                                                      qreal repeatDistance) const
{
    const bool clampToGround = f.testFlag(FollowGround);
    const bool followLatitudeCircle = f.testFlag(RespectLatitudeCircle)
                                      && previousCoords.latitude() == currentCoords.latitude();

    // Calculate steps for tessellation: lonDiff and altDiff
    qreal lonDiff = 0.0;

    if (followLatitudeCircle)
    {
        const int previousSign = previousCoords.longitude() > 0 ? 1 : -1;
        const int currentSign = currentCoords.longitude() > 0 ? 1 : -1;

        lonDiff = currentCoords.longitude() - previousCoords.longitude();

        if (previousSign != currentSign
            && fabs(previousCoords.longitude()) + fabs(currentCoords.longitude()) > M_PI)
        {
            if (previousSign > currentSign)
            {
                // going eastwards ->
                lonDiff += 2 * M_PI ;
            }

            else
            {
                // going westwards ->
                lonDiff -= 2 * M_PI;
            }
        }

        if (fabs(lonDiff) == 2 * M_PI)
        {
            return mirrorCount;
        }
    }

    // Create the tessellation nodes.
    GeoDataCoordinates previousTessellatedCoords = previousCoords;

    for (int i = 1; i <= tessellatedNodes; ++i)
    {
        const qreal t = (qreal)(i) / (qreal)(tessellatedNodes + 1);

        GeoDataCoordinates currentTessellatedCoords;

        if (followLatitudeCircle)
        {
            // To tessellate along latitude circles use the
            // linear interpolation of the longitude.
            // interpolate the altitude, too
            const qreal altDiff = currentCoords.altitude() - previousCoords.altitude();
            const qreal altitude = altDiff * t + previousCoords.altitude();
            const qreal lon = lonDiff * t + previousCoords.longitude();
            const qreal lat = previousTessellatedCoords.latitude();

            currentTessellatedCoords = GeoDataCoordinates(lon, lat, altitude);
        }

        else
        {
            // To tessellate along great circles use the
            // normalized linear interpolation ("NLERP") for latitude and longitude.
            currentTessellatedCoords = previousCoords.nlerp(currentCoords, t);
        }

        if (clampToGround)
        {
            currentTessellatedCoords.setAltitude(0);
        }

        Q_Q(const CylindricalProjection);
        qreal bx, by;
        q->screenCoordinates(currentTessellatedCoords, viewport, bx, by);
        mirrorCount = crossDateLine(previousTessellatedCoords, currentTessellatedCoords, bx, by, polygons,
                                    mirrorCount, repeatDistance);
        previousTessellatedCoords = currentTessellatedCoords;
    }

    // For the clampToGround case add the "current" coordinate after adding all other nodes.
    GeoDataCoordinates currentModifiedCoords(currentCoords);

    if (clampToGround)
    {
        currentModifiedCoords.setAltitude(0.0);
    }

    Q_Q(const CylindricalProjection);
    qreal bx, by;
    q->screenCoordinates(currentModifiedCoords, viewport, bx, by);
    mirrorCount = crossDateLine(previousTessellatedCoords, currentModifiedCoords, bx, by, polygons,
                                mirrorCount, repeatDistance);
    return mirrorCount;
}

int CylindricalProjectionPrivate::crossDateLine(const GeoDataCoordinates& aCoord,
                                                const GeoDataCoordinates& bCoord,
                                                qreal bx,
                                                qreal by,
                                                QVector<QPolygonF*>& polygons,
                                                int mirrorCount,
                                                qreal repeatDistance)
{
    qreal aLon = aCoord.longitude();
    qreal aSign = aLon > 0 ? 1 : -1;

    qreal bLon = bCoord.longitude();
    qreal bSign = bLon > 0 ? 1 : -1;

    qreal delta = 0;

    if (aSign != bSign && fabs(aLon) + fabs(bLon) > M_PI)
    {
        int sign = aSign > bSign ? 1 : -1;
        mirrorCount += sign;
    }

    delta = repeatDistance * mirrorCount;
    *polygons.last() << QPointF(bx + delta, by);

    return mirrorCount;
}

bool CylindricalProjectionPrivate::lineStringToPolygon(const GeoDataLineString& lineString,
                                                       const ViewportParams* viewport,
                                                       QVector<QPolygonF*>& polygons) const
{
    const TessellationFlags f = lineString.tessellationFlags();
    bool const tessellate = lineString.tessellate();
    const bool noFilter = f.testFlag(PreventNodeFiltering);

    qreal x = 0;
    qreal y = 0;

    qreal previousX = -1.0;
    qreal previousY = -1.0;

    int mirrorCount = 0;
    qreal distance = repeatDistance(viewport);

    QPolygonF* polygon = new QPolygonF;

    if (!tessellate)
    {
        polygon->reserve(lineString.size());
    }

    polygons.append(polygon);

    GeoDataLineString::ConstIterator itCoords = lineString.constBegin();
    GeoDataLineString::ConstIterator itPreviousCoords = lineString.constBegin();

    GeoDataLineString::ConstIterator itBegin = lineString.constBegin();
    GeoDataLineString::ConstIterator itEnd = lineString.constEnd();

    bool processingLastNode = false;

    // We use a while loop to be able to cover linestrings as well as linear rings:
    // Linear rings require to tessellate the path from the last node to the first node
    // which isn't really convenient to achieve with a for loop ...

    const bool isLong = lineString.size() > 10;
    const int maximumDetail = levelForResolution(viewport->angularResolution());
    // The first node of optimized linestrings has a non-zero detail value.
    const bool hasDetail = itBegin->detail() != 0;

    bool isStraight = lineString.latLonAltBox().height() == 0 || lineString.latLonAltBox().width() == 0;

    Q_Q(const CylindricalProjection);
    bool const isClosed = lineString.isClosed();

    while (itCoords != itEnd)
    {
        // Optimization for line strings with a big amount of nodes
        bool skipNode = (hasDetail ? itCoords->detail() > maximumDetail
                         : isLong && !processingLastNode && itCoords != itBegin &&
                         !viewport->resolves(*itPreviousCoords, *itCoords));

        if (!skipNode || noFilter)
        {
            q->screenCoordinates(*itCoords, viewport, x, y);

            // Initializing variables that store the values of the previous iteration
            if (!processingLastNode && itCoords == itBegin)
            {
                itPreviousCoords = itCoords;
                previousX = x;
                previousY = y;
            }

            // This if-clause contains the section that tessellates the line
            // segments of a linestring. If you are about to learn how the code of
            // this class works you can safely ignore this section for a start.
            if (tessellate && !isStraight)
            {
                mirrorCount = tessellateLineSegment(*itPreviousCoords, previousX, previousY,
                                                    *itCoords, x, y,
                                                    polygons, viewport,
                                                    f, mirrorCount, distance);
            }

            else
            {
                // special case for polys which cross dateline but have no Tessellation Flag
                // the expected rendering is a screen coordinates straight line between
                // points, but in projections with repeatX things are not smooth
                mirrorCount = crossDateLine(*itPreviousCoords, *itCoords, x, y, polygons, mirrorCount, distance);
            }

            itPreviousCoords = itCoords;
            previousX = x;
            previousY = y;
        }

        // Here we modify the condition to be able to process the
        // first node after the last node in a LinearRing.

        if (processingLastNode)
        {
            break;
        }

        ++itCoords;

        if (isClosed && itCoords == itEnd)
        {
            itCoords = itBegin;
            processingLastNode = true;
        }
    }

    // Closing e.g. in the Antarctica case.
    // This code makes the assumption that
    // - the first node is located at 180 E
    // - and the last node is located at 180 W
    // TODO: add a similar pattern in the crossDateLine() code.
    /*
    GeoDataLatLonAltBox box = lineString.latLonAltBox();
    if( lineString.isClosed() && box.width() == 2*M_PI ) {
        QPolygonF *poly = polygons.last();
        if( box.containsPole( NorthPole ) ) {
            qreal topMargin = 0.0;
            qreal dummy = 0.0;
            q_ptr->screenCoordinates(0.0, q_ptr->maxLat(), viewport, topMargin, dummy );
            poly->push_back( QPointF( poly->last().x(), topMargin ) );
            poly->push_back( QPointF( poly->first().x(), topMargin ) );
        } else {
            qreal bottomMargin = 0.0;
            qreal dummy = 0.0;
            q_ptr->screenCoordinates(0.0, q_ptr->minLat(), viewport, bottomMargin, dummy );
            poly->push_back( QPointF( poly->last().x(), bottomMargin ) );
            poly->push_back( QPointF( poly->first().x(), bottomMargin ) );
        }
    } */

    repeatPolygons(viewport, polygons);

    return polygons.isEmpty();
}

void CylindricalProjectionPrivate::translatePolygons(const QVector<QPolygonF*>& polygons,
                                                     QVector<QPolygonF*>& translatedPolygons,
                                                     qreal xOffset)
{
    // qCDebug(DIGIKAM_GEOENGINE_LOG) << "Translation: " << xOffset;
    translatedPolygons.reserve(polygons.size());

    QVector<QPolygonF*>::const_iterator itPolygon = polygons.constBegin();
    QVector<QPolygonF*>::const_iterator itEnd = polygons.constEnd();

    for (; itPolygon != itEnd; ++itPolygon)
    {
        QPolygonF* polygon = new QPolygonF;
        *polygon = **itPolygon;
        polygon->translate(xOffset, 0);
        translatedPolygons.append(polygon);
    }
}

void CylindricalProjectionPrivate::repeatPolygons(const ViewportParams* viewport,
                                                  QVector<QPolygonF*>& polygons) const
{
    Q_Q(const CylindricalProjection);

    qreal xEast = 0;
    qreal xWest = 0;
    qreal y = 0;

    // Choose a latitude that is inside the viewport.
    const qreal centerLatitude = viewport->viewLatLonAltBox().center().latitude();

    const GeoDataCoordinates westCoords(-M_PI, centerLatitude);
    const GeoDataCoordinates eastCoords(+M_PI, centerLatitude);

    q->screenCoordinates(westCoords, viewport, xWest, y);
    q->screenCoordinates(eastCoords, viewport, xEast, y);

    if (xWest <= 0 && xEast >= viewport->width() - 1)
    {
        // qCDebug(DIGIKAM_GEOENGINE_LOG) << "No repeats";
        return;
    }

    const qreal repeatXInterval = xEast - xWest;

    const int repeatsLeft  = (xWest > 0) ? (int)(xWest                       / repeatXInterval) + 1 : 0;
    const int repeatsRight = (xEast < viewport->width()) ? (int)((viewport->width() - xEast) / repeatXInterval) + 1 : 0;

    QVector<QPolygonF*> repeatedPolygons;

    for (int it = repeatsLeft; it > 0; --it)
    {
        const qreal xOffset = -it * repeatXInterval;
        QVector<QPolygonF*> translatedPolygons;
        translatePolygons(polygons, translatedPolygons, xOffset);
        repeatedPolygons << translatedPolygons;
    }

    repeatedPolygons << polygons;

    for (int it = 1; it <= repeatsRight; ++it)
    {
        const qreal xOffset = +it * repeatXInterval;
        QVector<QPolygonF*> translatedPolygons;
        translatePolygons(polygons, translatedPolygons, xOffset);
        repeatedPolygons << translatedPolygons;
    }

    polygons = repeatedPolygons;

    // qCDebug(DIGIKAM_GEOENGINE_LOG) << Q_FUNC_INFO << "Coordinates: " << xWest << xEast
    //          << "Repeats: " << repeatsLeft << repeatsRight;
}

qreal CylindricalProjectionPrivate::repeatDistance(const ViewportParams* viewport) const
{
    // Choose a latitude that is inside the viewport.
    qreal centerLatitude = viewport->viewLatLonAltBox().center().latitude();

    GeoDataCoordinates westCoords(-M_PI, centerLatitude);
    GeoDataCoordinates eastCoords(+M_PI, centerLatitude);
    qreal xWest, xEast, dummyY;

    Q_Q(const AbstractProjection);

    q->screenCoordinates(westCoords, viewport, xWest, dummyY);
    q->screenCoordinates(eastCoords, viewport, xEast, dummyY);

    return   xEast - xWest;
}

} // namespace Marble
