#include "snaplayout.hpp"

#include <QLoggingCategory>
#include <QQuickWindow>
#include <QScopeGuard>
#include <QtGui/private/qfont_p.h>
#include <algorithm>
#include <cmath>

Q_LOGGING_CATEGORY(lcQuickLayouts, "qt.quick.layouts")

namespace ZShell::components {
namespace {

qint64 originResidual(qreal logical, qreal dpr) {
	const qreal device = logical * dpr;
	return std::llround((device - std::floor(device)) * 1024.0) % 1024;
}

QPointF absoluteOrigin(const QQuickItem* item) {
	qreal x = 0.0;
	qreal y = 0.0;
	for (const QQuickItem* it = item; it; it = it->parentItem()) {
		x += it->x();
		y += it->y();
	}
	return QPointF(x, y);
}

} // namespace

qreal SnapLayoutStyleInfo::spacing(Qt::Orientation /*orientation*/) const {
#if defined(Q_OS_ANDROID) || defined(Q_OS_IOS) || defined(Q_OS_QNX)
	qreal spacing = 8.0;
#else
	qreal spacing = 5.0;
#endif
#if !defined(Q_OS_MACOS) && !defined(Q_OS_HARMONY)
	spacing = qRound(spacing * (qreal(qt_defaultDpiX()) / 96.0));
#endif
	return spacing;
}

qreal SnapLayoutStyleInfo::windowMargin(Qt::Orientation /*orientation*/) const {
	return 0;
}

bool SnapLayoutStyleInfo::hasChangedCore() const {
	return false;
}

SnapGridLayoutItem::SnapGridLayoutItem(
	QQuickItem* item,
	int row,
	int column,
	int rowSpan,
	int columnSpan,
	Qt::Alignment alignment)
	: QQuickGridLayoutItem(item, row, column, rowSpan, columnSpan, alignment) {}

void SnapGridLayoutItem::setGeometry(const QRectF& rect) {
	QQuickLayoutAttached* info = attachedLayoutObject(m_item, false);
	engineRect = info ? rect.marginsRemoved(info->effectiveQMargins()) : rect;
	placed = true;
}

void SnapLayoutPrivate::mirrorChange() {
	Q_Q(SnapLayout);
	q->invalidate();
}

SnapLayout::SnapLayout(QQuickItem* parent)
	: QQuickLayout(*new SnapLayoutPrivate, parent) {
	d_func()->styleInfo = new SnapLayoutStyleInfo;
}

SnapLayout::~SnapLayout() {
	Q_D(SnapLayout);
	clearAncestorListeners();
	deactivateRecur();
	delete d->styleInfo;
}

void SnapLayout::componentComplete() {
	QQuickLayout::componentComplete();

	applySpacing();
	invalidate();
	ensureLayoutItemsUpdated(QQuickLayout::ApplySizeHints);

	if (qobject_cast<QQuickLayout*>(parentItem())) return;
	rearrange(QSizeF(width(), height()));
}

void SnapLayout::itemChange(ItemChange change, const ItemChangeData& value) {
	QQuickLayout::itemChange(change, value);
	if (change == ItemChildRemovedChange && value.item)
		d_func()->childSizes.remove(value.item);
	if (change == ItemDevicePixelRatioHasChanged || change == ItemSceneChange) {
		applySpacing();
		invalidate();
	}
}

QSizeF SnapLayout::sizeHint(Qt::SizeHint whichSizeHint) const {
	Q_D(const SnapLayout);
	return d->engine.sizeHint(whichSizeHint, QSizeF(), d->styleInfo);
}

Qt::Orientation SnapLayout::orientation() const {
	return d_func()->orientation;
}

void SnapLayout::setOrientation(Qt::Orientation orientation) {
	Q_D(SnapLayout);
	if (d->orientation == orientation) return;
	d->orientation = orientation;
	invalidate();
	emit orientationChanged();
}

Qt::LayoutDirection SnapLayout::layoutDirection() const {
	return d_func()->layoutDirection;
}

void SnapLayout::setLayoutDirection(Qt::LayoutDirection direction) {
	Q_D(SnapLayout);
	if (d->layoutDirection == direction) return;
	d->layoutDirection = direction;
	invalidate();
	emit layoutDirectionChanged();
}

Qt::LayoutDirection SnapLayout::effectiveLayoutDirection() const {
	return !isMirrored() == (layoutDirection() == Qt::LeftToRight)
			   ? Qt::LeftToRight
			   : Qt::RightToLeft;
}

qreal SnapLayout::spacing() const {
	Q_D(const SnapLayout);
	if (!std::isnan(d->spacingRequest)) return d->spacingRequest;
	return d->styleInfo->spacing(d->orientation);
}

void SnapLayout::applySpacing() {
	Q_D(SnapLayout);
	if (!isReady()) return;

	const QQuickWindow* win = window();
	const qreal dpr = win ? win->effectiveDevicePixelRatio() : 1.0;

	qreal space = d->spacingRequest;
	if (std::isnan(space)) space = d->styleInfo->spacing(d->orientation);

	if (dpr > 0.0) space = qreal(std::llround(space * dpr)) / dpr;

	d->engine.setSpacing(space, Qt::Horizontal | Qt::Vertical);
}

void SnapLayout::setSpacing(qreal space) {
	Q_D(SnapLayout);
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wfloat-equal"
	if (std::isnan(space) || d->spacingRequest == space) return;
#pragma GCC diagnostic pop
	d->spacingRequest = space;
	applySpacing();
	invalidate();
	emit spacingChanged();
}

bool SnapLayout::uniformCellSizes() const {
	Q_D(const SnapLayout);
	return d->engine.uniformCellWidths();
}

void SnapLayout::setUniformCellSizes(bool uniformCellSizes) {
	Q_D(SnapLayout);
	if (d->engine.uniformCellHeights() == uniformCellSizes) return;
	d->engine.setUniformCellWidths(uniformCellSizes);
	d->engine.setUniformCellHeights(uniformCellSizes);
	invalidate();
	emit uniformCellSizesChanged();
}

void SnapLayout::setAlignment(QQuickItem* item, Qt::Alignment align) {
	Q_D(SnapLayout);
	if (QQuickGridLayoutItem* layoutItem = d->engine.findLayoutItem(item)) {
		layoutItem->setAlignment(align);
		d->engine.invalidate();
	}
	maybeSubscribeToBaseLineOffsetChanges(item);
}

void SnapLayout::setStretchFactor(
	QQuickItem* item, int stretchFactor, Qt::Orientation orient) {
	Q_D(SnapLayout);
	if (QQuickGridLayoutItem* layoutItem = d->engine.findLayoutItem(item)) {
		layoutItem->setStretchFactor(stretchFactor, orient);
		d->engine.invalidate();
	}
}

void SnapLayout::invalidate(QQuickItem* childItem) {
	Q_D(SnapLayout);
	if (!isReady()) return;

	if (childItem) {
		if (d->rearranging) {
			if (!d->invalidateAfterRearrange.contains(childItem))
				d->invalidateAfterRearrange << childItem;
			return;
		}
		if (QQuickGridLayoutItem* layoutItem =
				d->engine.findLayoutItem(childItem)) {
			layoutItem->invalidate();
		}
	}

	d->engine.invalidate();
	QQuickLayout::invalidate();

	if (auto* parentLayout = qobject_cast<QQuickLayout*>(parentItem()))
		parentLayout->invalidate(this);
}

void SnapLayout::updateLayoutItems() {
	Q_D(SnapLayout);
	if (!isReady()) return;

	const auto items = childItems();
	for (auto entry = d->childSizes.begin(); entry != d->childSizes.end();) {
		if (items.contains(entry.key()))
			++entry;
		else
			entry = d->childSizes.erase(entry);
	}

	d->engine.deleteItems();
	insertLayoutItems();
}

QQuickItem* SnapLayout::itemAt(int index) const {
	Q_D(const SnapLayout);
	return static_cast<QQuickGridLayoutItem*>(d->engine.itemAt(index))
		->layoutItem();
}

int SnapLayout::itemCount() const {
	Q_D(const SnapLayout);
	return d->engine.itemCount();
}

void SnapLayout::insertLayoutItems() {
	Q_D(SnapLayout);
	const auto items = childItems();
	for (QQuickItem* child : items) {
		Q_ASSERT(child);
		checkAnchors(child);

		if (shouldIgnoreItem(child)) continue;
		QQuickLayoutAttached* info = attachedLayoutObject(child, false);

		Qt::Alignment alignment;
		int hStretch = -1;
		int vStretch = -1;
		bool fillWidth = false;
		bool fillHeight = false;
		if (info) {
			alignment = info->alignment();
			hStretch = info->horizontalStretchFactor();
			vStretch = info->verticalStretchFactor();
			fillWidth = info->fillWidth();
			fillHeight = info->fillHeight();
		}

		const int index = d->engine.rowCount(d->orientation);
		d->engine.insertRow(index, d->orientation);

		int gridRow = 0;
		int gridColumn = index;
		if (d->orientation == Qt::Vertical) qSwap(gridRow, gridColumn);
		QGridLayoutItem* layoutItem =
			new SnapGridLayoutItem(child, gridRow, gridColumn, 1, 1, alignment);

		if (hStretch >= 0) {
			if (!fillWidth)
				qWarning() << "horizontalStretchFactor requires fillWidth to "
							  "also be set to true";
			layoutItem->setStretchFactor(hStretch, Qt::Horizontal);
		}
		if (vStretch >= 0) {
			if (!fillHeight)
				qWarning() << "verticalStretchFactor requires fillHeight to "
							  "also be set to true";
			layoutItem->setStretchFactor(vStretch, Qt::Vertical);
		}
		d->engine.insertItem(layoutItem, index);
	}
}

void SnapLayout::removeGridItem(QGridLayoutItem* gridItem) {
	Q_D(SnapLayout);
	const int index = gridItem->firstRow(d->orientation);
	d->engine.removeItem(gridItem);
	d->engine.removeRows(index, 1, d->orientation);
}

void SnapLayout::itemDestroyed(QQuickItem* item) {
	if (!isReady()) return;
	Q_D(SnapLayout);
	d->childSizes.remove(item);
	if (QQuickGridLayoutItem* gridItem = d->engine.findLayoutItem(item)) {
		removeGridItem(gridItem);
		delete gridItem;
		invalidate();
	}
}

void SnapLayout::itemVisibilityChanged(QQuickItem* item) {
	if (!isReady()) return;
	invalidate(item);
}

void SnapLayout::itemGeometryChanged(
	QQuickItem* item, QQuickGeometryChange change, const QRectF& oldGeometry) {
	Q_UNUSED(item);
	Q_UNUSED(oldGeometry);
	if (!isReady() || !change.positionChange()) return;

	Q_D(SnapLayout);
	const QQuickWindow* win = window();
	const qreal dpr = win ? win->effectiveDevicePixelRatio() : 0.0;
	if (dpr <= 0.0) return;

	const QPointF origin = absoluteOrigin(this);
	if (originResidual(origin.x(), dpr) == d->originResidualX &&
		originResidual(origin.y(), dpr) == d->originResidualY)
		return;
	polish();
}

void SnapLayout::updateAncestorListeners() {
	Q_D(SnapLayout);
	QVector<QQuickItem*> current;
	for (QQuickItem* it = parentItem(); it; it = it->parentItem()) {
		if (qobject_cast<SnapLayout*>(it)) break;
		current.append(it);
	}

	for (const QPointer<QQuickItem>& ancestor :
		 std::as_const(d->ancestorListeners)) {
		if (ancestor && !current.contains(ancestor.data()))
			QQuickItemPrivate::get(ancestor.data())
				->removeItemChangeListener(this, QQuickItemPrivate::Geometry);
	}
	for (QQuickItem* ancestor : std::as_const(current)) {
		if (!d->ancestorListeners.contains(ancestor))
			QQuickItemPrivate::get(ancestor)->addItemChangeListener(
				this, QQuickItemPrivate::Geometry);
	}
	d->ancestorListeners.clear();
	d->ancestorListeners.reserve(current.size());
	for (QQuickItem* ancestor : std::as_const(current))
		d->ancestorListeners.append(ancestor);
}

void SnapLayout::clearAncestorListeners() {
	Q_D(SnapLayout);
	for (const QPointer<QQuickItem>& ancestor :
		 std::as_const(d->ancestorListeners)) {
		if (ancestor)
			QQuickItemPrivate::get(ancestor.data())
				->removeItemChangeListener(this, QQuickItemPrivate::Geometry);
	}
	d->ancestorListeners.clear();
}

void SnapLayout::arrangeChildren() {
	Q_D(SnapLayout);
	const QQuickWindow* win = window();
	const qreal dpr = win ? win->effectiveDevicePixelRatio() : 1.0;
	if (dpr <= 0.0) return;

	const bool horiz = d->orientation == Qt::Horizontal;
	const QPointF origin = absoluteOrigin(this);
	const qint64 originXDev = std::llround(origin.x() * dpr);
	const qint64 originYDev = std::llround(origin.y() * dpr);

	qreal prevEndExact = 0.0;
	qint64 prevNearDev = 0;
	qint64 prevSizeDev = 0;
	bool started = false;

	for (int i = 0; i < d->engine.itemCount(); ++i) {
		SnapGridLayoutItem* gridItem =
			static_cast<SnapGridLayoutItem*>(d->engine.itemAt(i));
		if (!gridItem->placed) continue;
		QQuickItem* child = gridItem->layoutItem();
		const QRectF& cell = gridItem->engineRect;

		const qreal mainExact = (horiz ? cell.x() : cell.y()) * dpr;
		const qreal mainSizeExact =
			(horiz ? cell.width() : cell.height()) * dpr;
		const qreal crossExact = (horiz ? cell.y() : cell.x()) * dpr;
		const qint64 mainSizeDev = std::llround(mainSizeExact);
		const qint64 crossSizeDev =
			std::llround((horiz ? cell.height() : cell.width()) * dpr);
		const qint64 engineWidth = horiz ? mainSizeDev : crossSizeDev;
		const qint64 engineHeight = horiz ? crossSizeDev : mainSizeDev;

		qint64 mainNear = 0;
		if (!started) {
			mainNear = std::llround(mainExact);
			started = true;
		} else {
			mainNear = prevNearDev + prevSizeDev +
					   std::llround(mainExact - prevEndExact);
		}

		const qint64 mainFarDev = std::llround(mainExact + mainSizeExact);

		const auto stored = d->childSizes.constFind(child);
		qint64 width = engineWidth;
		qint64 height = engineHeight;
		if (horiz)
			width = std::max(mainFarDev - mainNear, qint64(0));
		else
			height = std::max(mainFarDev - mainNear, qint64(0));

		if (stored != d->childSizes.constEnd() &&
			stored.value().engineWidth == engineWidth &&
			stored.value().engineHeight == engineHeight &&
			std::llround(child->width() * dpr) == stored.value().width &&
			std::llround(child->height() * dpr) == stored.value().height) {
			width = stored.value().width;
			height = stored.value().height;
		} else {
			d->childSizes[child] = SnapLayoutPrivate::ChildSize{
				engineWidth, engineHeight, width, height};
		}

		prevEndExact = mainExact + mainSizeExact;
		prevNearDev = mainNear;
		prevSizeDev = horiz ? width : height;

		const qint64 crossNear = std::llround(crossExact);
		const qint64 nearX = originXDev + (horiz ? mainNear : crossNear);
		const qint64 nearY = originYDev + (horiz ? crossNear : mainNear);

		const QRectF snapped(
			qreal(nearX) / dpr - origin.x(),
			qreal(nearY) / dpr - origin.y(),
			qreal(width) / dpr,
			qreal(height) / dpr);

		const QSizeF oldSize(child->width(), child->height());
		const QSizeF newSize = snapped.size();

		child->setPosition(snapped.topLeft());
		if (newSize == oldSize) {
			if (QQuickLayout* lay = qobject_cast<QQuickLayout*>(child)) {
				if (lay->invalidatedArrangement()) lay->rearrange(newSize);
			}
		} else {
			child->setSize(newSize);
		}
	}
}

void SnapLayout::rearrange(const QSizeF& size) {
	Q_D(SnapLayout);
	if (!isReady() || !size.isValid()) return;

	const auto refCounter = qScopeGuard([&d] { --(d->recurRearrangeCounter); });
	if (d->recurRearrangeCounter++ == 2) {
		qWarning() << "Qt Quick Layouts: Detected recursive rearrange. "
					  "Aborting after two iterations.";
		return;
	}

	ensureLayoutItemsUpdated(
		QQuickLayout::ApplySizeHints | QQuickLayout::Recursive);

	d->rearranging = true;
	d->engine.setVisualDirection(effectiveLayoutDirection());
	updateAncestorListeners();

	if (const QQuickWindow* win = window()) {
		if (const qreal dpr = win->effectiveDevicePixelRatio(); dpr > 0.0) {
			const QPointF origin = absoluteOrigin(this);
			d->originResidualX = originResidual(origin.x(), dpr);
			d->originResidualY = originResidual(origin.y(), dpr);
		}
	}

	QQuickLayout::rearrange(size);

	for (int i = 0; i < d->engine.itemCount(); ++i)
		static_cast<SnapGridLayoutItem*>(d->engine.itemAt(i))->placed = false;
	d->engine.setGeometries(QRectF(QPointF(0, 0), size), d->styleInfo);
	arrangeChildren();
	d->rearranging = false;

	for (auto childItem : std::as_const(d->invalidateAfterRearrange))
		invalidate(childItem);
	d->invalidateAfterRearrange.clear();
}

} // namespace ZShell::components