/*
 * SPDX-FileCopyrightText: 2014 Hugo Pereira Da Costa <hugo.pereira@free.fr>
 * SPDX-FileCopyrightText: 2018, 2020 Vlad Zahorodnii <vlad.zahorodnii@kde.org>
 *
 * SPDX-License-Identifier: GPL-2.0-or-later
 */

#include "breezeshadowhelper.h"

#include "breezeboxshadowrenderer.h"
#include "breezehelper.h"
#include "breezemetrics.h"
#include "breezepropertynames.h"
#include "breezestyleconfigdata.h"

#include <KWindowSystem>

#include <QApplication>
#include <QDockWidget>
#include <QEvent>
#include <QMenu>
#include <QPainter>
#include <QPixmap>
#include <QPlatformSurfaceEvent>
#include <QTextStream>
#include <QToolBar>

namespace
{
using Breeze::CompositeShadowParams;
using Breeze::ShadowParams;

const CompositeShadowParams s_shadowParams[] = {
    // None
    CompositeShadowParams(),
    // Small
    CompositeShadowParams(QPoint(0, 3), ShadowParams(QPoint(0, 0), 12, 0.26), ShadowParams(QPoint(0, -2), 6, 0.16)),
    // Medium
    CompositeShadowParams(QPoint(0, 4), ShadowParams(QPoint(0, 0), 16, 0.24), ShadowParams(QPoint(0, -2), 8, 0.14)),
    // Large
    CompositeShadowParams(QPoint(0, 5), ShadowParams(QPoint(0, 0), 20, 0.22), ShadowParams(QPoint(0, -3), 10, 0.12)),
    // Very Large
    CompositeShadowParams(QPoint(0, 6), ShadowParams(QPoint(0, 0), 24, 0.2), ShadowParams(QPoint(0, -3), 12, 0.1))};
}

namespace Breeze
{
//_____________________________________________________
CompositeShadowParams ShadowHelper::lookupShadowParams(int shadowSizeEnum)
{
    switch (shadowSizeEnum) {
    case StyleConfigData::ShadowNone:
        return s_shadowParams[0];
    case StyleConfigData::ShadowSmall:
        return s_shadowParams[1];
    case StyleConfigData::ShadowMedium:
        return s_shadowParams[2];
    case StyleConfigData::ShadowLarge:
        return s_shadowParams[3];
    case StyleConfigData::ShadowVeryLarge:
        return s_shadowParams[4];
    default:
        // Fallback to the Large size.
        return s_shadowParams[3];
    }
}

//_____________________________________________________
ShadowHelper::ShadowHelper(const std::shared_ptr<Helper> &helper)
    : QObject()
    , _helper(helper)
{
    Q_ASSERT(helper);
}

//_______________________________________________________
ShadowHelper::~ShadowHelper()
{
    qDeleteAll(_shadows);
}

//______________________________________________
void ShadowHelper::reset()
{
    _tiles.clear();
    _shadowTiles = TileSet();
}

//_______________________________________________________
bool ShadowHelper::registerWidget(QWidget *widget, bool force)
{
    // make sure widget is not already registered
    if (_widgets.contains(widget)) {
        return false;
    }

    // check if widget qualifies
    if (!(force || acceptWidget(widget))) {
        return false;
    }

    // try to create shadow directly
    installShadows(widget);
    _widgets.insert(widget);

    // install event filter
    widget->removeEventFilter(this);
    widget->installEventFilter(this);

    // connect destroy signal
    connect(widget, &QObject::destroyed, this, &ShadowHelper::widgetDeleted);

    return true;
}

//_______________________________________________________
void ShadowHelper::unregisterWidget(QWidget *widget)
{
    if (_widgets.remove(widget)) {
        // uninstall the event filter
        widget->removeEventFilter(this);

        // disconnect all signals
        disconnect(widget, nullptr, this, nullptr);

        // uninstall the shadow
        uninstallShadows(widget);
    }
}

//_______________________________________________________
void ShadowHelper::loadConfig()
{
    // reset
    reset();

    // update property for registered widgets
    for (QWidget *widget : _widgets) {
        installShadows(widget);
    }
}

//_______________________________________________________
bool ShadowHelper::eventFilter(QObject *object, QEvent *event)
{
    if (Helper::isX11()) {
        // check event type
        if (event->type() != QEvent::WinIdChange) {
            return false;
        }

        // cast widget
        QWidget *widget(static_cast<QWidget *>(object));

        // install shadows and update winId
        installShadows(widget);

    } else {
        if (event->type() != QEvent::PlatformSurface) {
            return false;
        }

        QWidget *widget(static_cast<QWidget *>(object));
        QPlatformSurfaceEvent *surfaceEvent(static_cast<QPlatformSurfaceEvent *>(event));

        switch (surfaceEvent->surfaceEventType()) {
        case QPlatformSurfaceEvent::SurfaceCreated:
            installShadows(widget);
            break;
        case QPlatformSurfaceEvent::SurfaceAboutToBeDestroyed:
            // Don't care.
            break;
        }
    }

    return false;
}

//_______________________________________________________
TileSet ShadowHelper::shadowTiles(QWidget *widget)
{
    CompositeShadowParams params = lookupShadowParams(StyleConfigData::shadowSize());

    if (params.isNone()) {
        return TileSet();
    } else if (_shadowTiles.isValid()) {
        return _shadowTiles;
    }

    const qreal dpr = devicePixelRatio(widget);
    params *= dpr;

    auto withOpacity = [](const QColor &color, qreal opacity) -> QColor {
        QColor c(color);
        c.setAlphaF(opacity);
        return c;
    };

    const QColor color = StyleConfigData::shadowColor();
    const qreal strength = static_cast<qreal>(StyleConfigData::shadowStrength()) / 255.0;

    const QSize boxSize =
        BoxShadowRenderer::calculateMinimumBoxSize(params.shadow1.radius).expandedTo(BoxShadowRenderer::calculateMinimumBoxSize(params.shadow2.radius));

    const qreal frameRadius = _helper->frameRadius();

    BoxShadowRenderer shadowRenderer;
    shadowRenderer.setBorderRadius(frameRadius);
    shadowRenderer.setBoxSize(boxSize);

    shadowRenderer.addShadow(params.shadow1.offset, params.shadow1.radius, withOpacity(color, params.shadow1.opacity * strength));
    shadowRenderer.addShadow(params.shadow2.offset, params.shadow2.radius, withOpacity(color, params.shadow2.opacity * strength));

    QImage shadowTexture = shadowRenderer.render();

    const QRect outerRect(QPoint(0, 0), shadowTexture.size());

    QRect boxRect(QPoint(0, 0), boxSize);
    boxRect.moveCenter(outerRect.center());

    // Mask out inner rect.
    QPainter painter(&shadowTexture);
    painter.setRenderHint(QPainter::Antialiasing);

    const QMargins margins = QMargins(boxRect.left() - outerRect.left() - Metrics::Shadow_Overlap - params.offset.x(),
                                      boxRect.top() - outerRect.top() - Metrics::Shadow_Overlap - params.offset.y(),
                                      outerRect.right() - boxRect.right() - Metrics::Shadow_Overlap + params.offset.x(),
                                      outerRect.bottom() - boxRect.bottom() - Metrics::Shadow_Overlap + params.offset.y());

    painter.setPen(Qt::NoPen);
    painter.setBrush(Qt::black);
    painter.setCompositionMode(QPainter::CompositionMode_DestinationOut);
    painter.drawRoundedRect(outerRect - margins, frameRadius, frameRadius);

    // We're done.
    painter.end();

    const QPoint innerRectTopLeft = outerRect.center();
    _shadowTiles = TileSet(QPixmap::fromImage(std::move(shadowTexture)), innerRectTopLeft.x(), innerRectTopLeft.y(), 1, 1);

    return _shadowTiles;
}

//_______________________________________________________
void ShadowHelper::widgetDeleted(QObject *object)
{
    QWidget *widget(static_cast<QWidget *>(object));
    _widgets.remove(widget);
}

//_______________________________________________________
void ShadowHelper::windowDeleted(QObject *object)
{
    QWindow *window(static_cast<QWindow *>(object));
    _shadows.remove(window);
}

//_______________________________________________________
bool ShadowHelper::isMenu(QWidget *widget) const
{
    return qobject_cast<QMenu *>(widget);
}

//_______________________________________________________
bool ShadowHelper::isToolTip(QWidget *widget) const
{
    return widget->inherits("QTipLabel") || (widget->windowFlags() & Qt::WindowType_Mask) == Qt::ToolTip;
}

//_______________________________________________________
bool ShadowHelper::isDockWidget(QWidget *widget) const
{
    return qobject_cast<QDockWidget *>(widget);
}

//_______________________________________________________
bool ShadowHelper::isToolBar(QWidget *widget) const
{
    return qobject_cast<QToolBar *>(widget);
}

//_______________________________________________________
bool ShadowHelper::acceptWidget(QWidget *widget) const
{
    // flags
    if (widget->property(PropertyNames::netWMSkipShadow).toBool()) {
        return false;
    }
    if (widget->property(PropertyNames::netWMForceShadow).toBool()) {
        return true;
    }

    // menus
    if (isMenu(widget)) {
        return true;
    }

    // combobox dropdown lists
    if (widget->inherits("QComboBoxPrivateContainer")) {
        return true;
    }

    // tooltips
    if (isToolTip(widget) && !widget->inherits("Plasma::ToolTip")) {
        return true;
    }

    // detached widgets
    if (isDockWidget(widget) || isToolBar(widget)) {
        return true;
    }

    // reject
    return false;
}

//______________________________________________
const QVector<KWindowShadowTile::Ptr> &ShadowHelper::createShadowTiles()
{
    // make sure size is valid
    if (_tiles.isEmpty()) {
        _tiles = {createTile(_shadowTiles.pixmap(1)),
                  createTile(_shadowTiles.pixmap(2)),
                  createTile(_shadowTiles.pixmap(5)),
                  createTile(_shadowTiles.pixmap(8)),
                  createTile(_shadowTiles.pixmap(7)),
                  createTile(_shadowTiles.pixmap(6)),
                  createTile(_shadowTiles.pixmap(3)),
                  createTile(_shadowTiles.pixmap(0))};
    }

    // return relevant list of shadow tiles
    return _tiles;
}

//______________________________________________
KWindowShadowTile::Ptr ShadowHelper::createTile(const QPixmap &source)
{
    KWindowShadowTile::Ptr tile = KWindowShadowTile::Ptr::create();
    tile->setImage(source.toImage());
    return tile;
}

//_______________________________________________________
void ShadowHelper::installShadows(QWidget *widget)
{
    if (!widget) {
        return;
    }

    // only toplevel widgets can cast drop-shadows
    if (!widget->isWindow()) {
        return;
    }

    // widget must have valid native window
    if (!widget->testAttribute(Qt::WA_WState_Created)) {
        return;
    }

    // create shadow tiles if needed
    shadowTiles(widget);
    if (!_shadowTiles.isValid()) {
        return;
    }

    // create platform shadow tiles if needed
    const QVector<KWindowShadowTile::Ptr> &tiles = createShadowTiles();
    if (tiles.count() != numTiles) {
        return;
    }

    // get the underlying window for the widget
    QWindow *window = widget->windowHandle();

    // find a shadow associated with the widget
    KWindowShadow *&shadow = _shadows[window];

    if (!shadow) {
        // if there is no shadow yet, create one
        shadow = new KWindowShadow(window);

        // connect destroy signal
        connect(window, &QWindow::destroyed, this, &ShadowHelper::windowDeleted);
    }

    if (shadow->isCreated()) {
        shadow->destroy();
    }

    shadow->setTopTile(tiles[0]);
    shadow->setTopRightTile(tiles[1]);
    shadow->setRightTile(tiles[2]);
    shadow->setBottomRightTile(tiles[3]);
    shadow->setBottomTile(tiles[4]);
    shadow->setBottomLeftTile(tiles[5]);
    shadow->setLeftTile(tiles[6]);
    shadow->setTopLeftTile(tiles[7]);
    shadow->setPadding(shadowMargins(widget));
    shadow->setWindow(window);
    shadow->create();
}

//_______________________________________________________
QMargins ShadowHelper::shadowMargins(QWidget *widget) const
{
    CompositeShadowParams params = lookupShadowParams(StyleConfigData::shadowSize());
    if (params.isNone()) {
        return QMargins();
    }
    qreal dpr = devicePixelRatio(widget);
    params *= dpr;

    const QSize boxSize =
        BoxShadowRenderer::calculateMinimumBoxSize(params.shadow1.radius).expandedTo(BoxShadowRenderer::calculateMinimumBoxSize(params.shadow2.radius));

    const QSize shadowSize = BoxShadowRenderer::calculateMinimumShadowTextureSize(boxSize, params.shadow1.radius, params.shadow1.offset)
                                 .expandedTo(BoxShadowRenderer::calculateMinimumShadowTextureSize(boxSize, params.shadow2.radius, params.shadow2.offset));

    const QRect shadowRect(QPoint(0, 0), shadowSize);

    QRect boxRect(QPoint(0, 0), boxSize);
    boxRect.moveCenter(shadowRect.center());

    QMargins margins(boxRect.left() - shadowRect.left() - Metrics::Shadow_Overlap - params.offset.x(),
                     boxRect.top() - shadowRect.top() - Metrics::Shadow_Overlap - params.offset.y(),
                     shadowRect.right() - boxRect.right() - Metrics::Shadow_Overlap + params.offset.x(),
                     shadowRect.bottom() - boxRect.bottom() - Metrics::Shadow_Overlap + params.offset.y());

    if (widget->inherits("QBalloonTip")) {
        // Balloon tip needs special margins to deal with the arrow.
        int top = widget->contentsMargins().top();
        int bottom = widget->contentsMargins().bottom();

        // Need to decrement default size further due to extra hard coded round corner.
        margins -= 1;

        // Arrow can be either to the top or the bottom. Adjust margins accordingly.
        const int diff = qAbs(top - bottom);
        if (top > bottom) {
            margins.setTop(margins.top() - diff);
        } else {
            margins.setBottom(margins.bottom() - diff);
        }
    }

    return margins;
}

//_______________________________________________________
void ShadowHelper::uninstallShadows(QWidget *widget)
{
    delete _shadows.take(widget->windowHandle());
}

//_______________________________________________________
qreal ShadowHelper::devicePixelRatio(QWidget *widget)
{
    // On Wayland, the compositor will upscale the shadow tiles if necessary.
    return Helper::isWayland() ? 1 : widget->devicePixelRatioF();
}

}