#include "GlobeWidget.h"

#include <QLinearGradient>
#include <QHash>
#include <QFile>
#include <QJsonArray>
#include <QJsonDocument>
#include <QJsonObject>
#include <QMouseEvent>
#include <QPainter>
#include <QPainterPath>
#include <QPolygonF>
#include <QRadialGradient>
#include <QWheelEvent>

#include <algorithm>
#include <cmath>
#include <utility>

namespace {
constexpr double Pi = 3.14159265358979323846;
constexpr double InitialLongitudeOffset = 0.50;
constexpr double InitialLatitudeOffset = 0.28;

struct Vec3 { double x; double y; double z; };

Vec3 globeVector(double latitude, double longitude)
{
    const double lat = latitude * Pi / 180.0;
    const double lon = longitude * Pi / 180.0;
    return {std::cos(lat) * std::cos(lon), std::cos(lat) * std::sin(lon), std::sin(lat)};
}

const QVector<QPolygonF> &fallbackLandPolygons()
{
    // Deliberately simplified Natural-Earth-like coastlines. QPointF is lon/lat.
    static const QVector<QPolygonF> polygons = {
        // North America
        {{-168, 66}, {-155, 72}, {-138, 70}, {-128, 61}, {-123, 50}, {-124, 42},
         {-117, 32}, {-106, 24}, {-97, 19}, {-90, 19}, {-83, 24}, {-81, 31},
         {-75, 39}, {-66, 45}, {-60, 52}, {-64, 60}, {-78, 63}, {-89, 69},
         {-105, 73}, {-125, 72}, {-145, 75}},
        // Central America
        {{-106, 24}, {-97, 18}, {-91, 16}, {-87, 12}, {-83, 9}, {-79, 8},
         {-77, 10}, {-84, 16}, {-91, 20}},
        // South America
        {{-81, 12}, {-72, 12}, {-61, 8}, {-50, 3}, {-43, -5}, {-35, -8},
         {-39, -19}, {-48, -29}, {-53, -36}, {-60, -47}, {-67, -55},
         {-74, -50}, {-75, -38}, {-71, -28}, {-70, -18}, {-76, -7}},
        // Greenland
        {{-73, 60}, {-52, 59}, {-39, 65}, {-20, 76}, {-28, 83}, {-49, 84},
         {-65, 78}},
        // Europe and Asia
        {{-11, 36}, {-10, 44}, {-5, 50}, {4, 54}, {12, 58}, {20, 69},
         {34, 71}, {48, 77}, {72, 76}, {96, 78}, {119, 73}, {142, 71},
         {165, 66}, {178, 58}, {169, 50}, {151, 46}, {141, 38}, {128, 34},
         {121, 24}, {110, 20}, {105, 10}, {98, 7}, {91, 21}, {80, 8},
         {72, 18}, {62, 25}, {53, 27}, {45, 38}, {36, 42}, {28, 40},
         {20, 35}, {12, 36}, {4, 43}},
        // Arabian peninsula
        {{35, 31}, {48, 30}, {56, 24}, {51, 15}, {43, 12}, {36, 20}},
        // India and southeast Asia
        {{67, 25}, {76, 31}, {88, 25}, {92, 22}, {87, 8}, {80, 6},
         {74, 15}},
        {{95, 22}, {106, 21}, {110, 12}, {105, 1}, {100, 7}},
        // Africa
        {{-17, 37}, {-5, 37}, {10, 35}, {25, 31}, {34, 22}, {43, 12},
         {51, 11}, {48, 2}, {42, -12}, {33, -26}, {25, -35}, {17, -34},
         {10, -25}, {2, -9}, {-8, 5}, {-16, 15}},
        // Australia
        {{112, -11}, {125, -10}, {138, -14}, {153, -27}, {151, -39},
         {139, -44}, {126, -34}, {114, -35}, {111, -23}},
        // Madagascar
        {{47, -13}, {51, -17}, {49, -27}, {44, -25}, {43, -18}},
        // Japan
        {{130, 31}, {136, 34}, {142, 43}, {145, 44}, {141, 35}},
        // Great Britain
        {{-8, 50}, {-3, 58}, {1, 57}, {2, 51}},
        // New Zealand
        {{166, -34}, {174, -41}, {178, -47}, {171, -45}},
    };
    return polygons;
}

const QVector<QPolygonF> &landPolygons()
{
    static const QVector<QPolygonF> polygons = [] {
        QFile file(QStringLiteral(":/resources/land-110m.json"));
        if (!file.open(QIODevice::ReadOnly)) return fallbackLandPolygons();
        const QJsonDocument document = QJsonDocument::fromJson(file.readAll());
        const QJsonObject root = document.object();
        const QJsonObject transform = root.value(QStringLiteral("transform")).toObject();
        const QJsonArray scale = transform.value(QStringLiteral("scale")).toArray();
        const QJsonArray translate = transform.value(QStringLiteral("translate")).toArray();
        if (scale.size() != 2 || translate.size() != 2) return fallbackLandPolygons();

        const double scaleX = scale[0].toDouble();
        const double scaleY = scale[1].toDouble();
        const double translateX = translate[0].toDouble();
        const double translateY = translate[1].toDouble();
        QVector<QPolygonF> decodedArcs;
        const QJsonArray arcs = root.value(QStringLiteral("arcs")).toArray();
        decodedArcs.reserve(arcs.size());
        for (const QJsonValue &arcValue : arcs) {
            int x = 0;
            int y = 0;
            QPolygonF arc;
            for (const QJsonValue &pointValue : arcValue.toArray()) {
                const QJsonArray point = pointValue.toArray();
                if (point.size() != 2) continue;
                x += point[0].toInt();
                y += point[1].toInt();
                arc.push_back(QPointF(x * scaleX + translateX,
                                      y * scaleY + translateY));
            }
            decodedArcs.push_back(arc);
        }

        QVector<QPolygonF> result;
        const QJsonObject land = root.value(QStringLiteral("objects")).toObject()
                                     .value(QStringLiteral("land")).toObject();
        const QJsonArray geometries = land.value(QStringLiteral("geometries")).toArray();
        for (const QJsonValue &geometryValue : geometries) {
            const QJsonObject geometry = geometryValue.toObject();
            const QJsonArray multiPolygon = geometry.value(QStringLiteral("arcs")).toArray();
            for (const QJsonValue &polygonValue : multiPolygon) {
                const QJsonArray rings = polygonValue.toArray();
                if (rings.isEmpty()) continue;
                const QJsonArray ringArcs = rings[0].toArray(); // outer coastline
                QPolygonF polygon;
                for (const QJsonValue &arcIndexValue : ringArcs) {
                    const int reference = arcIndexValue.toInt();
                    const int index = reference >= 0 ? reference : ~reference;
                    if (index < 0 || index >= decodedArcs.size()) continue;
                    QPolygonF arc = decodedArcs[index];
                    if (reference < 0) std::reverse(arc.begin(), arc.end());
                    for (int i = polygon.isEmpty() ? 0 : 1; i < arc.size(); ++i) {
                        polygon.push_back(arc[i]);
                    }
                }
                if (polygon.size() >= 3) result.push_back(polygon);
            }
        }
        return result.isEmpty() ? fallbackLandPolygons() : result;
    }();
    return polygons;
}

const QImage &landMask()
{
    // A geographic mask decouples coastline quality from the size of the widget.
    // It is generated once and remains fixed in Earth coordinates while rotating.
    static const QImage mask = [] {
        constexpr int Width = 1440;
        constexpr int Height = 720;
        QImage image(Width, Height, QImage::Format_Grayscale8);
        image.fill(0);
        QPainter painter(&image);
        painter.setRenderHint(QPainter::Antialiasing, true);
        painter.setPen(Qt::NoPen);
        painter.setBrush(Qt::white);
        for (const QPolygonF &geographic : landPolygons()) {
            QPolygonF projected;
            projected.reserve(geographic.size());
            double previousLongitude = geographic.first().x();
            double unwrappedLongitude = previousLongitude;
            for (const QPointF &point : geographic) {
                double longitude = point.x();
                while (longitude - previousLongitude > 180.0) longitude -= 360.0;
                while (longitude - previousLongitude < -180.0) longitude += 360.0;
                unwrappedLongitude += longitude - previousLongitude;
                previousLongitude = longitude;
                projected.push_back(QPointF((unwrappedLongitude + 180.0) / 360.0 * Width,
                                             (90.0 - point.y()) / 180.0 * Height));
            }
            for (int copy = -1; copy <= 1; ++copy) {
                QPolygonF shifted = projected;
                shifted.translate(copy * Width, 0.0);
                painter.drawPolygon(shifted);
            }
        }
        painter.end();
        return image;
    }();
    return mask;
}

bool maskIsLand(double longitude, double latitude)
{
    const QImage &mask = landMask();
    longitude = std::fmod(longitude + 180.0, 360.0);
    if (longitude < 0.0) longitude += 360.0;
    const int x = std::clamp(static_cast<int>(longitude / 360.0 * mask.width()),
                             0, mask.width() - 1);
    const int y = std::clamp(static_cast<int>((90.0 - latitude) / 180.0 * mask.height()),
                             0, mask.height() - 1);
    return mask.constScanLine(y)[x] != 0;
}

double smoothStep(double edge0, double edge1, double value)
{
    const double t = std::clamp((value - edge0) / (edge1 - edge0), 0.0, 1.0);
    return t * t * (3.0 - 2.0 * t);
}
}

GlobeWidget::GlobeWidget(QWidget *parent)
    : QWidget(parent)
{
    setObjectName(QStringLiteral("globeWidget"));
    setMinimumSize(420, 360);
    setMouseTracking(true);
    setCursor(Qt::OpenHandCursor);
    setToolTip(QStringLiteral("Dunyayi dondurmek icin surukleyin, yakinlastirmak icin tekerlegi kullanin"));
    // GNSS satellites move only a few screen pixels per minute. Ten frames per
    // second is visually smooth here and avoids repainting a static globe at 30 FPS.
    m_satelliteAnimationTimer.setInterval(100);
    m_satelliteAnimationTimer.setTimerType(Qt::CoarseTimer);
    connect(&m_satelliteAnimationTimer, &QTimer::timeout,
            this, &GlobeWidget::updateSatelliteAnimation);
}

void GlobeWidget::setSatellites(const QVector<SatellitePosition> &satellites)
{
    m_satellites = satellites;
    update();
}

void GlobeWidget::setSatelliteMotion(const QVector<SatellitePosition> &current,
                                     const QVector<SatellitePosition> &next,
                                     int durationMs)
{
    if (current.isEmpty() || next.isEmpty() || durationMs <= 0) {
        setSatellites(current);
        m_satelliteAnimationTimer.stop();
        return;
    }

    // Continue from the currently rendered points when a fresh ephemeris arrives,
    // avoiding even a small visual jump at the update boundary.
    const QVector<SatellitePosition> &candidateStart =
        m_satellites.isEmpty() ? current : m_satellites;
    QHash<QString, SatellitePosition> starts;
    starts.reserve(candidateStart.size());
    for (const SatellitePosition &satellite : candidateStart) {
        starts.insert(satellite.prn, satellite);
    }

    m_satelliteMotionStart.clear();
    m_satelliteMotionTarget.clear();
    m_satelliteMotionStart.reserve(next.size());
    m_satelliteMotionTarget.reserve(next.size());
    for (const SatellitePosition &target : next) {
        const auto start = starts.constFind(target.prn);
        if (start == starts.cend()) continue;
        m_satelliteMotionStart.push_back(start.value());
        m_satelliteMotionTarget.push_back(target);
    }
    if (m_satelliteMotionStart.isEmpty()) {
        setSatellites(current);
        m_satelliteAnimationTimer.stop();
        return;
    }
    m_satelliteMotionDurationMs = durationMs;
    m_satelliteMotionClock.restart();
    m_satelliteAnimationTimer.start();
    updateSatelliteAnimation();
}

void GlobeWidget::updateSatelliteAnimation()
{
    if (!m_satelliteMotionClock.isValid() || m_satelliteMotionDurationMs <= 0) return;

    const double progress = std::clamp(
        static_cast<double>(m_satelliteMotionClock.elapsed()) / m_satelliteMotionDurationMs,
        0.0, 1.0);
    QVector<SatellitePosition> interpolated;
    interpolated.reserve(m_satelliteMotionStart.size());
    for (qsizetype i = 0; i < m_satelliteMotionStart.size(); ++i) {
        const SatellitePosition &start = m_satelliteMotionStart[i];
        const SatellitePosition &target = m_satelliteMotionTarget[i];
        SatellitePosition point = start;
        point.x += (target.x - start.x) * progress;
        point.y += (target.y - start.y) * progress;
        point.z += (target.z - start.z) * progress;
        point.healthy = target.healthy;
        interpolated.push_back(point);
    }
    if (!interpolated.isEmpty()) m_satellites = interpolated;
    update();

    if (progress >= 1.0) m_satelliteAnimationTimer.stop();
}

void GlobeWidget::setObservedPrns(const QSet<QString> &prns)
{
    m_observedPrns = prns;
    update();
}

void GlobeWidget::setReceiverLocation(double latitude, double longitude)
{
    const bool firstLocation = !m_hasReceiver;
    m_hasReceiver = true;
    m_receiverLatitude = latitude;
    m_receiverLongitude = longitude;
    if (firstLocation) {
        // Keep the receiver off-centre so its local zenith is visibly directed
        // away from Earth. Looking straight down the zenith made the outward
        // visibility cone appear to be embedded in the globe.
        m_yaw = Pi / 2.0 - longitude * Pi / 180.0 + InitialLongitudeOffset;
        m_pitch = std::clamp(-latitude * Pi / 180.0 + InitialLatitudeOffset,
                             -1.15, 1.15);
    }
    update();
}

void GlobeWidget::clearReceiverLocation()
{
    m_hasReceiver = false;
    update();
}

void GlobeWidget::setRinexStatus(const QString &status, bool error)
{
    m_status = status;
    m_statusError = error;
    update();
}

void GlobeWidget::setElevationMask(double degrees)
{
    m_elevationMaskDegrees = std::clamp(degrees, 0.0, 90.0);
    update();
}

GlobeWidget::ProjectedPoint GlobeWidget::project(double x, double y, double z, double radius) const
{
    const double cy = std::cos(m_yaw);
    const double sy = std::sin(m_yaw);
    const double x1 = cy * x - sy * y;
    const double y1 = sy * x + cy * y;
    const double cp = std::cos(m_pitch);
    const double sp = std::sin(m_pitch);
    const double y2 = cp * y1 - sp * z;
    const double z2 = sp * y1 + cp * z;
    const QPointF center(width() * 0.5, height() * 0.52);
    return {{center.x() + x1 * radius, center.y() - z2 * radius}, y2};
}

void GlobeWidget::paintEvent(QPaintEvent *)
{
    QPainter painter(this);
    painter.setRenderHint(QPainter::Antialiasing, true);

    const qreal devicePixelRatio = devicePixelRatioF();
    if (m_staticLayer.isNull() || m_staticLayerSize != size()
        || !qFuzzyCompare(m_staticLayerDevicePixelRatio, devicePixelRatio)
        || m_staticLayerYaw != m_yaw || m_staticLayerPitch != m_pitch
        || m_staticLayerZoom != m_zoom) {
        rebuildStaticLayer();
    }
    painter.drawPixmap(0, 0, m_staticLayer);

    if (m_hasReceiver) drawVisibilityCone(painter);
    if (m_hasReceiver) drawReceiver(painter);
    const int visibleCount = drawSatellites(painter);

    painter.setPen(QColor(229, 240, 249));
    QFont titleFont = painter.font();
    titleFont.setPixelSize(18);
    titleFont.setBold(true);
    painter.setFont(titleFont);
    painter.drawText(QRect(20, 16, width() - 40, 28), Qt::AlignLeft | Qt::AlignVCenter,
                     QStringLiteral("GNSS YORUNGE GORUNUMU"));
    QFont smallFont = painter.font();
    smallFont.setPixelSize(11);
    smallFont.setBold(false);
    painter.setFont(smallFont);
    painter.setPen(m_statusError ? QColor(255, 177, 77) : QColor(132, 177, 204));
    painter.drawText(QRect(20, 43, width() - 40, 22), Qt::AlignLeft | Qt::AlignVCenter, m_status);

    const int legendY = height() - 25;
    const int legendX = width() / 2 - 125;
    painter.setPen(Qt::NoPen);
    painter.setBrush(QColor(42, 224, 137));
    painter.drawEllipse(QPointF(legendX, legendY - 3), 4, 4);
    painter.setPen(QColor(101, 239, 176));
    painter.drawText(legendX + 9, legendY + 1, QStringLiteral("BULUNDU"));
    painter.setPen(Qt::NoPen);
    painter.setBrush(QColor(255, 79, 95));
    painter.drawEllipse(QPointF(legendX + 78, legendY - 3), 4, 4);
    painter.setPen(QColor(255, 132, 143));
    painter.drawText(legendX + 87, legendY + 1, QStringLiteral("BULUNAMADI"));
    painter.setPen(QColor(138, 183, 207));
    painter.drawText(legendX + 181, legendY + 1,
                     QStringLiteral("%1/%2 PRN · ELEV≥%3°: %4")
                         .arg(m_observedPrns.size()).arg(m_satellites.size())
                         .arg(m_elevationMaskDegrees, 0, 'f', 1).arg(visibleCount));

    if (!m_hasReceiver) {
        painter.setPen(QColor(219, 232, 241));
        QFont waitingFont = painter.font();
        waitingFont.setPixelSize(16);
        waitingFont.setBold(true);
        painter.setFont(waitingFont);
        painter.drawText(rect().adjusted(30, 70, -30, -50), Qt::AlignCenter,
                         QStringLiteral("Ilk gecerli konum bekleniyor"));
    }
}

void GlobeWidget::rebuildStaticLayer()
{
    const qreal devicePixelRatio = devicePixelRatioF();
    const QSize pixelSize(
        std::max(1, qRound(width() * devicePixelRatio)),
        std::max(1, qRound(height() * devicePixelRatio)));
    QPixmap layer(pixelSize);
    layer.setDevicePixelRatio(devicePixelRatio);
    layer.fill(Qt::transparent);
    QPainter painter(&layer);
    painter.setRenderHint(QPainter::Antialiasing, true);

    QLinearGradient background(0, 0, width(), height());
    background.setColorAt(0.0, QColor(3, 10, 21));
    background.setColorAt(0.55, QColor(8, 24, 43));
    background.setColorAt(1.0, QColor(2, 8, 17));
    painter.fillRect(rect(), background);
    drawStars(painter);

    const double radius = std::min(width(), height()) * 0.255 * m_zoom;
    const QPointF center(width() * 0.5, height() * 0.52);

    QRadialGradient atmosphere(center - QPointF(radius * .25, radius * .32), radius * 1.24);
    atmosphere.setColorAt(0.66, QColor(19, 113, 177, 0));
    atmosphere.setColorAt(0.82, QColor(47, 169, 235, 48));
    atmosphere.setColorAt(0.92, QColor(51, 178, 239, 20));
    atmosphere.setColorAt(1.0, QColor(35, 126, 205, 0));
    painter.setPen(Qt::NoPen);
    painter.setBrush(atmosphere);
    painter.drawEllipse(center, radius * 1.25, radius * 1.25);

    QRadialGradient earth(center - QPointF(radius * .36, radius * .42), radius * 1.42);
    earth.setColorAt(0.0, QColor(48, 154, 200));
    earth.setColorAt(0.37, QColor(18, 91, 144));
    earth.setColorAt(0.72, QColor(8, 47, 86));
    earth.setColorAt(1.0, QColor(1, 10, 24));
    painter.setBrush(earth);
    painter.setPen(QPen(QColor(89, 196, 240, 150), 1.2));
    painter.drawEllipse(center, radius, radius);

    painter.save();
    painter.setClipPath(QPainterPath());
    QPainterPath sphereClip;
    sphereClip.addEllipse(center, radius, radius);
    painter.setClipPath(sphereClip);
    drawContinents(painter);
    drawGraticule(painter);
    painter.restore();

    for (int i = 0; i < 3; ++i) drawOrbit(painter, 55.0 + i * 1.8, i * 61.0 + 12.0);
    painter.end();

    m_staticLayer = std::move(layer);
    m_staticLayerSize = size();
    m_staticLayerDevicePixelRatio = devicePixelRatio;
    m_staticLayerYaw = m_yaw;
    m_staticLayerPitch = m_pitch;
    m_staticLayerZoom = m_zoom;
}

void GlobeWidget::drawContinents(QPainter &painter) const
{
    const double radius = std::min(width(), height()) * 0.255 * m_zoom;
    const double pixelRatio = m_dragging ? 0.75 : std::min(devicePixelRatioF(), 1.5);
    const int textureSize = std::clamp(
        static_cast<int>(std::ceil(radius * 2.0 * pixelRatio)),
        m_dragging ? 240 : 320, m_dragging ? 480 : 900);
    const QPointF center(width() * 0.5, height() * 0.52);
    const QRectF target(center.x() - radius, center.y() - radius,
                        radius * 2.0, radius * 2.0);
    if (!m_landTexture.isNull() && m_landTexture.width() == textureSize
        && m_landTextureYaw == m_yaw && m_landTexturePitch == m_pitch) {
        painter.setRenderHint(QPainter::SmoothPixmapTransform, true);
        painter.drawImage(target, m_landTexture);
        return;
    }
    QImage land(textureSize, textureSize, QImage::Format_ARGB32);
    land.fill(Qt::transparent);

    const double cy = std::cos(m_yaw);
    const double sy = std::sin(m_yaw);
    const double cp = std::cos(m_pitch);
    const double sp = std::sin(m_pitch);
    for (int py = 0; py < textureSize; ++py) {
        QRgb *scanLine = reinterpret_cast<QRgb *>(land.scanLine(py));
        const double screenZ = -((py + 0.5) / textureSize * 2.0 - 1.0);
        for (int px = 0; px < textureSize; ++px) {
            const double screenX = (px + 0.5) / textureSize * 2.0 - 1.0;
            const double radiusSquared = screenX * screenX + screenZ * screenZ;
            if (radiusSquared > 1.0) continue;

            const double depth = std::sqrt(1.0 - radiusSquared);
            const double yawY = cp * depth + sp * screenZ;
            const double worldZ = -sp * depth + cp * screenZ;
            const double worldX = cy * screenX + sy * yawY;
            const double worldY = -sy * screenX + cy * yawY;
            const double latitude = std::asin(std::clamp(worldZ, -1.0, 1.0)) * 180.0 / Pi;
            const double longitude = std::atan2(worldY, worldX) * 180.0 / Pi;
            const bool onLand = maskIsLand(longitude, latitude);
            const bool nearLand = maskIsLand(longitude + 0.55, latitude)
                || maskIsLand(longitude - 0.55, latitude)
                || maskIsLand(longitude, latitude + 0.55)
                || maskIsLand(longitude, latitude - 0.55);
            if (!onLand) {
                if (nearLand) {
                    const int alpha = static_cast<int>(65.0 * std::clamp(depth * 1.5, 0.0, 1.0));
                    scanLine[px] = qRgba(33, 151, 174, alpha);
                }
                continue;
            }

            const double light = std::clamp(0.30 + 0.70
                * (0.35 - screenX * 0.38 + screenZ * 0.48 + depth * 0.38), 0.18, 1.0);
            const double lon = longitude * Pi / 180.0;
            const double lat = latitude * Pi / 180.0;
            const double broadRelief = 0.50 + 0.24 * std::sin(lon * 5.0 + lat * 2.2)
                + 0.16 * std::sin(lon * 13.0 - lat * 7.0)
                + 0.10 * std::cos(lon * 29.0 + lat * 17.0);
            const double relief = std::clamp(broadRelief, 0.0, 1.0);
            const double aridBelt = std::exp(-std::pow((std::abs(latitude) - 25.0) / 13.0, 2.0));
            const double moisture = std::clamp(0.62 - aridBelt * 0.48
                + 0.18 * std::sin(lon * 3.0 - lat * 4.0), 0.0, 1.0);
            const double highland = smoothStep(0.67, 0.92, relief);
            const double snow = smoothStep(63.0, 78.0, std::abs(latitude))
                * (0.65 + highland * 0.35);

            const double lushRed = 30.0 + relief * 25.0;
            const double lushGreen = 104.0 + relief * 34.0;
            const double lushBlue = 63.0 + relief * 20.0;
            const double dryRed = 151.0 + relief * 24.0;
            const double dryGreen = 126.0 + relief * 18.0;
            const double dryBlue = 72.0 + relief * 16.0;
            double red = dryRed + (lushRed - dryRed) * moisture;
            double green = dryGreen + (lushGreen - dryGreen) * moisture;
            double blue = dryBlue + (lushBlue - dryBlue) * moisture;
            red = red * (1.0 - highland * 0.30) + 104.0 * highland * 0.30;
            green = green * (1.0 - highland * 0.30) + 91.0 * highland * 0.30;
            blue = blue * (1.0 - highland * 0.30) + 76.0 * highland * 0.30;
            red = red * (1.0 - snow) + 224.0 * snow;
            green = green * (1.0 - snow) + 231.0 * snow;
            blue = blue * (1.0 - snow) + 224.0 * snow;

            const bool coast = !maskIsLand(longitude + 0.55, latitude)
                || !maskIsLand(longitude - 0.55, latitude)
                || !maskIsLand(longitude, latitude + 0.55)
                || !maskIsLand(longitude, latitude - 0.55);
            const double shade = light * (0.86 + relief * 0.14);
            if (coast) {
                red += 28.0;
                green += 31.0;
                blue += 18.0;
            }
            scanLine[px] = qRgba(
                std::clamp(static_cast<int>(red * shade), 0, 255),
                std::clamp(static_cast<int>(green * shade), 0, 255),
                std::clamp(static_cast<int>(blue * shade), 0, 255), 238);
        }
    }

    m_landTexture = land;
    m_landTextureYaw = m_yaw;
    m_landTexturePitch = m_pitch;
    painter.setRenderHint(QPainter::SmoothPixmapTransform, true);
    painter.drawImage(target, m_landTexture);
}

void GlobeWidget::drawStars(QPainter &painter) const
{
    painter.setPen(Qt::NoPen);
    for (int i = 0; i < 95; ++i) {
        const int x = (i * 7919 + 37) % std::max(1, width());
        const int y = (i * 3571 + 71) % std::max(1, height());
        const int alpha = 45 + (i * 29) % 120;
        const double size = 0.7 + (i % 4) * 0.35;
        painter.setBrush(QColor(183, 218, 240, alpha));
        painter.drawEllipse(QPointF(x, y), size, size);
    }
}

void GlobeWidget::drawGraticule(QPainter &painter) const
{
    const double radius = std::min(width(), height()) * 0.255 * m_zoom;
    painter.setPen(QPen(QColor(100, 193, 221, 48), 0.8));
    for (int latitude = -60; latitude <= 60; latitude += 30) {
        QPainterPath path;
        bool started = false;
        for (int longitude = -180; longitude <= 180; longitude += 3) {
            const Vec3 v = globeVector(latitude, longitude);
            const auto p = project(v.x, v.y, v.z, radius);
            if (p.depth >= 0.0) {
                if (!started) path.moveTo(p.point); else path.lineTo(p.point);
                started = true;
            } else started = false;
        }
        painter.drawPath(path);
    }
    for (int longitude = -150; longitude < 180; longitude += 30) {
        QPainterPath path;
        bool started = false;
        for (int latitude = -90; latitude <= 90; latitude += 2) {
            const Vec3 v = globeVector(latitude, longitude);
            const auto p = project(v.x, v.y, v.z, radius);
            if (p.depth >= 0.0) {
                if (!started) path.moveTo(p.point); else path.lineTo(p.point);
                started = true;
            } else started = false;
        }
        painter.drawPath(path);
    }
}

void GlobeWidget::drawOrbit(QPainter &painter, double inclination, double node) const
{
    const double radius = std::min(width(), height()) * 0.255 * m_zoom * 1.47;
    const double inc = inclination * Pi / 180.0;
    const double asc = node * Pi / 180.0;
    QPainterPath back, front;
    bool backStarted = false, frontStarted = false;
    for (int degree = 0; degree <= 360; degree += 2) {
        const double t = degree * Pi / 180.0;
        const double ox = std::cos(t);
        const double oy = std::sin(t) * std::cos(inc);
        const double oz = std::sin(t) * std::sin(inc);
        const double x = ox * std::cos(asc) - oy * std::sin(asc);
        const double y = ox * std::sin(asc) + oy * std::cos(asc);
        const auto p = project(x, y, oz, radius);
        QPainterPath &path = p.depth < 0.0 ? back : front;
        bool &started = p.depth < 0.0 ? backStarted : frontStarted;
        if (!started) path.moveTo(p.point); else path.lineTo(p.point);
        started = true;
        if (p.depth < 0.0) frontStarted = false; else backStarted = false;
    }
    painter.setBrush(Qt::NoBrush);
    painter.setPen(QPen(QColor(86, 130, 160, 44), 0.8, Qt::DashLine));
    painter.drawPath(back);
    painter.setPen(QPen(QColor(89, 173, 214, 90), 1.0));
    painter.drawPath(front);
}

void GlobeWidget::drawVisibilityCone(QPainter &painter) const
{
    if (!m_hasReceiver) return;

    const double earthRadiusPixels = std::min(width(), height()) * 0.255 * m_zoom;
    constexpr double physicalOrbitRatio = 4.17;
    constexpr double displayOrbitRatio = 1.47;
    const Vec3 normal = globeVector(m_receiverLatitude, m_receiverLongitude);

    Vec3 reference = std::abs(normal.z) < 0.85 ? Vec3{0.0, 0.0, 1.0} : Vec3{1.0, 0.0, 0.0};
    Vec3 tangentA {
        reference.y * normal.z - reference.z * normal.y,
        reference.z * normal.x - reference.x * normal.z,
        reference.x * normal.y - reference.y * normal.x
    };
    const double tangentLength = std::sqrt(tangentA.x * tangentA.x
                                           + tangentA.y * tangentA.y
                                           + tangentA.z * tangentA.z);
    tangentA = {tangentA.x / tangentLength, tangentA.y / tangentLength,
                tangentA.z / tangentLength};
    const Vec3 tangentB {
        normal.y * tangentA.z - normal.z * tangentA.y,
        normal.z * tangentA.x - normal.x * tangentA.z,
        normal.x * tangentA.y - normal.y * tangentA.x
    };

    const double elevation = m_elevationMaskDegrees * Pi / 180.0;
    const double zenith = Pi / 2.0 - elevation;
    const double lineDistance = -std::cos(zenith)
        + std::sqrt(physicalOrbitRatio * physicalOrbitRatio
                    - std::sin(zenith) * std::sin(zenith));
    const auto apex = project(normal.x, normal.y, normal.z, earthRadiusPixels * 1.015);
    const auto zenithPoint = project(normal.x, normal.y, normal.z,
                                     earthRadiusPixels * displayOrbitRatio);

    QVector<ProjectedPoint> ring;
    constexpr int Segments = 48;
    ring.reserve(Segments + 1);
    for (int segment = 0; segment <= Segments; ++segment) {
        const double angle = 2.0 * Pi * segment / Segments;
        const Vec3 tangent {
            tangentA.x * std::cos(angle) + tangentB.x * std::sin(angle),
            tangentA.y * std::cos(angle) + tangentB.y * std::sin(angle),
            tangentA.z * std::cos(angle) + tangentB.z * std::sin(angle)
        };
        const Vec3 direction {
            normal.x * std::cos(zenith) + tangent.x * std::sin(zenith),
            normal.y * std::cos(zenith) + tangent.y * std::sin(zenith),
            normal.z * std::cos(zenith) + tangent.z * std::sin(zenith)
        };
        const Vec3 orbitPoint {
            (normal.x + lineDistance * direction.x) / physicalOrbitRatio,
            (normal.y + lineDistance * direction.y) / physicalOrbitRatio,
            (normal.z + lineDistance * direction.z) / physicalOrbitRatio
        };
        ring.push_back(project(orbitPoint.x, orbitPoint.y, orbitPoint.z,
                               earthRadiusPixels * displayOrbitRatio));
    }

    painter.setPen(Qt::NoPen);
    for (int i = 0; i < Segments; ++i) {
        const double averageDepth = (apex.depth + ring[i].depth + ring[i + 1].depth) / 3.0;
        const int alpha = averageDepth >= 0.0 ? 18 : 7;
        painter.setBrush(QColor(48, 207, 218, alpha));
        painter.drawPolygon(QPolygonF{apex.point, ring[i].point, ring[i + 1].point});
    }

    QPainterPath boundary;
    boundary.moveTo(ring.first().point);
    for (int i = 1; i < ring.size(); ++i) boundary.lineTo(ring[i].point);
    painter.setBrush(Qt::NoBrush);
    painter.setPen(QPen(QColor(76, 222, 228, 105), 1.0, Qt::DashLine));
    painter.drawPath(boundary);
    for (int i = 0; i < Segments; i += 8) {
        painter.drawLine(apex.point, ring[i].point);
    }
    painter.setPen(QPen(QColor(119, 239, 241, 165), 1.4));
    painter.drawLine(apex.point, zenithPoint.point);

    const QPointF axis = zenithPoint.point - apex.point;
    const double axisLength = std::hypot(axis.x(), axis.y());
    if (axisLength > 1.0) {
        const QPointF unit = axis / axisLength;
        const QPointF side(-unit.y(), unit.x());
        const QPointF arrowTip = zenithPoint.point;
        painter.drawLine(arrowTip, arrowTip - unit * 8.0 + side * 4.0);
        painter.drawLine(arrowTip, arrowTip - unit * 8.0 - side * 4.0);
    }
    if (apex.depth >= -0.05) {
        painter.setPen(QColor(119, 239, 241, 190));
        painter.drawText(apex.point + QPointF(12, 18),
                         QStringLiteral("GORUS KONISI %1°")
                             .arg(m_elevationMaskDegrees, 0, 'f', 1));
    }
}

void GlobeWidget::drawReceiver(QPainter &painter) const
{
    const double radius = std::min(width(), height()) * 0.255 * m_zoom;
    const Vec3 v = globeVector(m_receiverLatitude, m_receiverLongitude);
    const auto p = project(v.x, v.y, v.z, radius * 1.015);
    if (p.depth < -0.05) return;
    painter.setPen(QPen(QColor(255, 255, 255, 210), 1.5));
    painter.setBrush(QColor(255, 196, 61));
    painter.drawEllipse(p.point, 5.5, 5.5);
    painter.setPen(QPen(QColor(255, 196, 61, 110), 1.2));
    painter.setBrush(Qt::NoBrush);
    painter.drawEllipse(p.point, 11, 11);
    painter.setPen(QColor(255, 224, 147));
    painter.drawText(p.point + QPointF(10, -8), QStringLiteral("ALICI"));
}

int GlobeWidget::drawSatellites(QPainter &painter) const
{
    if (!m_hasReceiver) return 0;
    const double orbitRadius = std::min(width(), height()) * 0.255 * m_zoom * 1.47;
    struct Item {
        SatellitePosition satellite;
        ProjectedPoint projected;
        double elevation = -90.0;
    };
    QVector<Item> items;
    items.reserve(m_satellites.size());
    for (const auto &satellite : m_satellites) {
        const double length = std::sqrt(satellite.x * satellite.x + satellite.y * satellite.y
                                        + satellite.z * satellite.z);
        if (length <= 0.0) continue;
        items.push_back({satellite, project(satellite.x / length, satellite.y / length,
                                            satellite.z / length, orbitRadius),
                         satelliteElevation(satellite)});
    }
    std::sort(items.begin(), items.end(), [](const Item &a, const Item &b) {
        return a.projected.depth < b.projected.depth;
    });
    const double earthRadius = std::min(width(), height()) * 0.255 * m_zoom;
    const Vec3 receiver = globeVector(m_receiverLatitude, m_receiverLongitude);
    const auto receiverPoint = project(receiver.x, receiver.y, receiver.z,
                                       earthRadius * 1.02);
    int visibleCount = 0;
    for (const Item &item : items) {
        const bool found = m_observedPrns.contains(item.satellite.prn);
        const bool inElevationMask = item.elevation >= m_elevationMaskDegrees;
        if (inElevationMask) ++visibleCount;
        QColor color = found ? QColor(42, 224, 137) : QColor(255, 79, 95);
        if (item.projected.depth < 0.0) color.setAlpha(75);
        const double markerRadius = found ? 6.5 : 5.0;
        if (inElevationMask) {
            QColor sightLine(70, 224, 231, item.projected.depth < 0.0 ? 25 : 80);
            painter.setPen(QPen(sightLine, 0.8, Qt::DashLine));
            painter.drawLine(receiverPoint.point, item.projected.point);
            painter.setPen(QPen(QColor(90, 236, 239, sightLine.alpha()), 1.2));
            painter.setBrush(Qt::NoBrush);
            painter.drawEllipse(item.projected.point, markerRadius + 3.0, markerRadius + 3.0);
        }
        painter.setPen(QPen(QColor(235, 248, 255, color.alpha()), 1.0));
        painter.setBrush(color);
        painter.drawEllipse(item.projected.point, markerRadius, markerRadius);
        if (item.projected.depth >= -0.05) {
            painter.setPen(color.lighter(135));
            painter.drawText(item.projected.point + QPointF(7, -6), item.satellite.prn);
        }
    }
    return visibleCount;
}

double GlobeWidget::satelliteElevation(const SatellitePosition &satellite) const
{
    if (!m_hasReceiver) return -90.0;
    constexpr double EarthRadiusMeters = 6378137.0;
    const Vec3 receiverUnit = globeVector(m_receiverLatitude, m_receiverLongitude);
    const Vec3 lineOfSight {
        satellite.x - receiverUnit.x * EarthRadiusMeters,
        satellite.y - receiverUnit.y * EarthRadiusMeters,
        satellite.z - receiverUnit.z * EarthRadiusMeters
    };
    const double length = std::sqrt(lineOfSight.x * lineOfSight.x
                                    + lineOfSight.y * lineOfSight.y
                                    + lineOfSight.z * lineOfSight.z);
    if (length <= 0.0) return -90.0;
    const double sineElevation = (lineOfSight.x * receiverUnit.x
                                  + lineOfSight.y * receiverUnit.y
                                  + lineOfSight.z * receiverUnit.z) / length;
    return std::asin(std::clamp(sineElevation, -1.0, 1.0)) * 180.0 / Pi;
}

void GlobeWidget::mousePressEvent(QMouseEvent *event)
{
    if (event->button() == Qt::LeftButton) {
        m_dragging = true;
        m_lastMousePosition = event->pos();
        setCursor(Qt::ClosedHandCursor);
    }
}

void GlobeWidget::mouseMoveEvent(QMouseEvent *event)
{
    if (!m_dragging) return;
    const QPoint delta = event->pos() - m_lastMousePosition;
    m_lastMousePosition = event->pos();
    m_yaw += delta.x() * 0.008;
    m_pitch = std::clamp(m_pitch - delta.y() * 0.008, -1.45, 1.45);
    update();
}

void GlobeWidget::mouseReleaseEvent(QMouseEvent *event)
{
    if (event->button() == Qt::LeftButton) {
        m_dragging = false;
        m_staticLayer = QPixmap();
        setCursor(Qt::OpenHandCursor);
        update();
    }
}

void GlobeWidget::wheelEvent(QWheelEvent *event)
{
    m_zoom = std::clamp(m_zoom + event->angleDelta().y() / 1200.0, 0.72, 1.28);
    update();
    event->accept();
}