z-bar-qt/Plugins/ZShell/Components/carouselview.cpp

#include "carouselview.hpp"

#include <QQmlContext>
#include <QQmlProperty>
#include <QMouseEvent>
#include <QWheelEvent>
#include <QGuiApplication>
#include <QStyleHints>
#include <cmath>

namespace ZShell::components {

namespace {
constexpr qreal kDragThreshold = 4.0;
constexpr qreal kFlickFriction = 0.0022;
constexpr qreal kMinFlickVelocity = 60.0;
constexpr qreal kMaxFlickVelocity = 6000.0;
} // namespace

CarouselView::CarouselView(QQuickItem* parent) : QQuickItem(parent) {
	setAcceptedMouseButtons(Qt::LeftButton);
	setFlag(QQuickItem::ItemHasContents, false);
	setClip(false);

	m_glideAnim = new QVariantAnimation(this);
	m_glideAnim->setEasingCurve(m_glideEasingType);
	connect(
		m_glideAnim,
		&QVariantAnimation::valueChanged,
		this,
		[this](const QVariant& v) {
			m_contentX = v.toReal();
			wrapContentIfNeeded();
			updateCurrentIndexFromContentX(true);
			relayout();
		});
	connect(m_glideAnim, &QVariantAnimation::finished, this, [this]() {
		updateCurrentIndexFromContentX(true);
	});

	m_flickAnim = new QVariantAnimation(this);
	m_flickAnim->setEasingCurve(QEasingCurve::Linear);
	connect(
		m_flickAnim,
		&QVariantAnimation::valueChanged,
		this,
		[this](const QVariant& v) {
			m_contentX = v.toReal();
			wrapContentIfNeeded();
			updateCurrentIndexFromContentX(true);
			relayout();
		});
	connect(m_flickAnim, &QVariantAnimation::finished, this, [this]() {
		snapToNearest();
	});
}

CarouselView::~CarouselView() {
	releaseAllItems();
}

void CarouselView::setDelegate(QQmlComponent* c) {
	if (m_delegate == c) return;
	m_delegate = c;
	releaseAllItems();
	emit delegateChanged();
	relayout();
}

void CarouselView::setModel(const QVariantList& m) {
	m_model = m;
	emit modelChanged();

	int newCount = m_model.size();
	if (newCount == 0) {
		m_currentRealIndex = -1;
		releaseAllItems();
		rebuildArrangement();
		return;
	}
	if (!m_initializedLayout) {
		m_centerBlockStart = (kLoopMultiplier / 2) * newCount;
		m_currentVirtualIndex = m_centerBlockStart;
		m_contentX = contentXForIndex(m_currentVirtualIndex);
		m_currentRealIndex = realIndexOf(m_currentVirtualIndex);
		m_previewRealIndex = m_currentRealIndex;
		m_initializedLayout = true;
		rebuildArrangement();
		relayout();
		return;
	}

	rebuildArrangement();
	centerInstantlyOnReal(qBound(0, m_currentRealIndex, newCount - 1));
}

void CarouselView::setFocalWidth(qreal v) {
	if (qFuzzyCompare(m_focalWidth, v)) return;
	m_focalWidth = v;
	emit focalWidthChanged();
	rebuildArrangement();
	relayout();
}

void CarouselView::setMinEdgeWidth(qreal v) {
	if (qFuzzyCompare(m_minEdgeWidth, v)) return;
	m_minEdgeWidth = v;
	emit minEdgeWidthChanged();
	rebuildArrangement();
	relayout();
}

void CarouselView::setItemSpacing(qreal v) {
	if (qFuzzyCompare(m_itemSpacing, v)) return;
	m_itemSpacing = v;
	emit itemSpacingChanged();
	rebuildArrangement();
	relayout();
}

void CarouselView::setTileHeight(qreal v) {
	if (qFuzzyCompare(m_tileHeight, v)) return;
	m_tileHeight = v;
	emit tileHeightChanged();
	for (const Slot& s : std::as_const(m_slots)) {
		if (s.active && s.item)
			QQmlProperty::write(
				s.item, QStringLiteral("tileHeight"), m_tileHeight);
	}
}

void CarouselView::setMaxWidth(qreal v) {
	if (qFuzzyCompare(m_maxWidth, v)) return;
	m_maxWidth = v;
	emit maxWidthChanged();
	rebuildArrangement();
	relayout();
}

void CarouselView::setGlideDuration(int v) {
	if (m_glideDuration == v) return;
	m_glideDuration = v;
	emit glideDurationChanged();
}

void CarouselView::setGlideEasingType(QEasingCurve::Type t) {
	if (m_glideEasingType == t) return;
	m_glideEasingType = t;
	m_glideAnim->setEasingCurve(t);
	emit glideEasingTypeChanged();
}

void CarouselView::setDelegateProperties(const QVariantMap& v) {
	m_delegateProperties = v;
	emit delegatePropertiesChanged();
	for (const Slot& s : std::as_const(m_slots)) {
		if (s.active && s.item) {
			for (auto it = m_delegateProperties.constBegin();
				 it != m_delegateProperties.constEnd();
				 ++it)
				QQmlProperty::write(s.item, it.key(), it.value());
		}
	}
}

void CarouselView::setCurrentIndex(int idx) {
	goToIndex(idx);
}

void CarouselView::geometryChange(const QRectF& newGeo, const QRectF& oldGeo) {
	QQuickItem::geometryChange(newGeo, oldGeo);
	if (!qFuzzyCompare(newGeo.width(), oldGeo.width()) ||
		!qFuzzyCompare(newGeo.height(), oldGeo.height())) {
		rebuildArrangement();
		if (m_initializedLayout)
			m_contentX = contentXForIndex(m_currentVirtualIndex);
		relayout();
	}
}

void CarouselView::rebuildArrangement() {
	Arrangement& a = m_arrangement;
	a = Arrangement{};

	const qreal W = m_maxWidth;
	const qreal F = m_focalWidth;
	const qreal M = m_minEdgeWidth;
	const qreal sp = m_itemSpacing;

	if (W <= 0 || F <= 0) {
		a.sizes = {F};
		a.centers = {0};
		return;
	}

	int bestN = 0;
	QVector<qreal> bestSizes = {F};
	qreal bestWidth = F;

	for (int n = 1;; ++n) {
		const qreal ratio = std::pow(M / F, 1.0 / n);
		QVector<qreal> sizes = {F};
		qreal sideWidth = 0;

		for (int i = 1; i <= n; ++i) {
			const qreal size = (i == n) ? M : F * std::pow(ratio, i);
			sizes.push_back(size);
			sideWidth += size;
		}

		const qreal requiredWidth = F + 2 * n * sp + 2 * sideWidth;
		if (requiredWidth > W) break;

		bestN = n;
		bestSizes = sizes;
		bestWidth = requiredWidth;

		if (n > 64) break;
	}

	a.n = bestN;
	a.sizes = bestSizes;
	a.width = bestWidth;

	QVector<qreal> centers = {0};
	qreal center = 0;
	for (int i = 1; i <= bestN; ++i) {
		center += bestSizes[i - 1] / 2.0 + sp + bestSizes[i] / 2.0;
		centers.push_back(center);
	}
	a.centers = centers;

	qreal extra = 0;
	for (int i = 1; i <= bestN; ++i)
		extra += pitch() - bestSizes[i];
	a.effectiveExtraWidth = extra;

	setImplicitWidth(m_maxWidth);
	setWidth(a.width);
}

qreal CarouselView::keylineCenter(int io) const {
	const int n = m_arrangement.n;
	const int i = std::abs(io);
	if (i == 0) return 0;
	const int sign = io < 0 ? -1 : 1;

	if (i <= n) return sign * m_arrangement.centers[i];

	if (i == n + 1) {
		const qreal lastCenter = m_arrangement.centers[n];
		const qreal lastSize = m_arrangement.sizes[n];
		return sign * (lastCenter + lastSize / 2.0 + m_itemSpacing +
					   m_minEdgeWidth / 2.0);
	}

	const qreal outgoingCenter = std::abs(keylineCenter(sign * (n + 1)));
	return sign * (outgoingCenter + m_minEdgeWidth / 2.0 + m_itemSpacing);
}

qreal CarouselView::keylineSize(int io) const {
	const int n = m_arrangement.n;
	const int i = std::abs(io);
	if (i == 0) return m_focalWidth;
	if (i <= n) return m_arrangement.sizes[i];
	if (i == n + 1) return m_minEdgeWidth;
	return 0;
}

qreal CarouselView::sampleCenter(qreal childLoc) const {
	const int n = m_arrangement.n;
	if (n <= 0) return 0;

	const int minIo = -(n + 2);
	const int maxIo = n + 2;
	const qreal p = pitch();

	const int a = static_cast<int>(std::floor(childLoc / p));
	if (a < minIo) return keylineCenter(minIo);
	if (a >= maxIo) return keylineCenter(maxIo);

	const int b = a + 1;
	const qreal t = (childLoc - a * p) / p;
	return keylineCenter(a) + (keylineCenter(b) - keylineCenter(a)) * t;
}

qreal CarouselView::sampleSize(qreal childLoc) const {
	const int n = m_arrangement.n;
	if (n <= 0) return 0;

	const int minIo = -(n + 2);
	const int maxIo = n + 2;
	const qreal p = pitch();

	const int a = static_cast<int>(std::floor(childLoc / p));
	if (a < minIo) return keylineSize(minIo);
	if (a >= maxIo) return keylineSize(maxIo);

	const int b = a + 1;
	const qreal t = (childLoc - a * p) / p;
	return keylineSize(a) + (keylineSize(b) - keylineSize(a)) * t;
}

int CarouselView::realIndexOf(int virtualIndex) const {
	const int count = m_model.size();
	if (count == 0) return -1;
	return ((virtualIndex % count) + count) % count;
}

qreal CarouselView::contentXForIndex(qreal index) const {
	return index * pitch() + pitch() / 2.0 - width() / 2.0;
}

int CarouselView::indexForContentX(qreal x) const {
	return static_cast<int>(
		std::round((x + width() / 2.0 - pitch() / 2.0) / pitch()));
}

qreal CarouselView::snapTargetX(qreal x) const {
	return contentXForIndex(indexForContentX(x));
}

void CarouselView::wrapContentIfNeeded() {
	const int count = m_model.size();
	if (count == 0) return;

	const qreal blockWidth = count * pitch();
	const qreal centerX = contentXForIndex(m_centerBlockStart);
	const int blocksFromCenter =
		static_cast<int>(std::round((m_contentX - centerX) / blockWidth));

	if (std::abs(blocksFromCenter) >= 2) {
		const qreal shift = blocksFromCenter * blockWidth;
		m_contentX -= shift;

		if (m_glideAnim->state() == QAbstractAnimation::Running) {
			const qreal newEnd = m_glideAnim->endValue().toReal() - shift;
			m_glideAnim->setEndValue(newEnd);
		}
		if (m_flickAnim->state() == QAbstractAnimation::Running) {
			const qreal newEnd = m_flickAnim->endValue().toReal() - shift;
			m_flickAnim->setEndValue(newEnd);
		}
		const int indexShift = static_cast<int>(std::round(shift / pitch()));
		for (Slot& s : m_slots) {
			if (s.active) s.virtualIndex -= indexShift;
		}
	}
}

void CarouselView::updateCurrentIndexFromContentX(bool emitPreview) {
	const int count = m_model.size();
	if (count == 0) return;

	const int newVirtual = static_cast<int>(
		std::round((m_contentX + width() / 2.0 - pitch() / 2.0) / pitch()));
	if (newVirtual == m_currentVirtualIndex) return;

	m_currentVirtualIndex = newVirtual;
	const int newReal = realIndexOf(newVirtual);

	if (newReal != m_currentRealIndex) {
		m_currentRealIndex = newReal;
		emit currentIndexChanged();
	}
	if (emitPreview && newReal != m_previewRealIndex) {
		m_previewRealIndex = newReal;
		if (newReal >= 0)
			emit previewIndexChanged(newReal, m_model.at(newReal));
	}
}

QQuickItem* CarouselView::acquireItem() {
	if (!m_delegate) return nullptr;

	QQmlContext* ctx = QQmlEngine::contextForObject(this);
	QVariantMap initial;
	initial.insert(QStringLiteral("isCurrent"), false);
	initial.insert(QStringLiteral("modelData"), QVariant());
	initial.insert(QStringLiteral("tileHeight"), m_tileHeight);
	initial.insert(QStringLiteral("tileWidth"), m_focalWidth);
	for (auto it = m_delegateProperties.constBegin();
		 it != m_delegateProperties.constEnd();
		 ++it)
		initial.insert(it.key(), it.value());

	QObject* obj = m_delegate->createWithInitialProperties(initial, ctx);
	if (!obj) {
		qWarning(
			"CarouselView: failed to create delegate instance: %s",
			qPrintable(m_delegate->errorString()));
		return nullptr;
	}
	QQuickItem* item = qobject_cast<QQuickItem*>(obj);
	if (!item) {
		qWarning("CarouselView: delegate root is not an Item");
		delete obj;
		return nullptr;
	}

	item->setParentItem(this);
	QQmlEngine::setObjectOwnership(item, QQmlEngine::CppOwnership);

	const QMetaMethod activateSignal = item->metaObject()->method(
		item->metaObject()->indexOfSignal("requestActivate()"));
	if (activateSignal.isValid()) {
		static const QMetaMethod slot = metaObject()->method(
			metaObject()->indexOfSlot("handleDelegateActivate()"));
		connect(item, activateSignal, this, slot);
	}

	return item;
}

void CarouselView::applyPropertiesToItem(QQuickItem* item, int realIndex) const {
	if (!item) return;
	const bool isCurrent = (realIndex == m_currentRealIndex);
	QQmlProperty::write(item, QStringLiteral("isCurrent"), isCurrent);
	QQmlProperty::write(
		item,
		QStringLiteral("modelData"),
		realIndex >= 0 && realIndex < m_model.size() ? m_model.at(realIndex)
													 : QVariant());
	QQmlProperty::write(item, QStringLiteral("tileHeight"), m_tileHeight);
}

void CarouselView::updateSlotContent(Slot& slot, int virtualIndex) {
	if (!slot.item) slot.item = acquireItem();
	if (!slot.item) return;

	slot.virtualIndex = virtualIndex;
	slot.realIndex = realIndexOf(virtualIndex);
	slot.active = slot.realIndex >= 0;
	slot.item->setVisible(slot.active);
	if (slot.active) applyPropertiesToItem(slot.item, slot.realIndex);
}

void CarouselView::positionSlot(const Slot& slot) const {
	if (!slot.item || !slot.active) return;

	const qreal childLoc = slot.virtualIndex * pitch() + pitch() / 2.0 -
						   m_contentX - width() / 2.0;
	const qreal center = sampleCenter(childLoc);
	const qreal size = sampleSize(childLoc);

	const qreal slotX = childLoc + width() / 2.0 - pitch() / 2.0;
	const qreal itemX = (center - childLoc) + (pitch() - size) / 2.0 + slotX;

	QQmlProperty::write(slot.item, QStringLiteral("tileWidth"), size);
	slot.item->setX(itemX);
	slot.item->setY(0);
	slot.item->setVisible(size > 0.5);
}

void CarouselView::releaseAllItems() {
	for (Slot& s : m_slots) {
		if (s.item) s.item->deleteLater();
	}
	m_slots.clear();
}

void CarouselView::relayout() {
	const int count = m_model.size();
	if (count == 0 || width() <= 0 || m_focalWidth <= 0) {
		for (Slot& s : m_slots)
			if (s.item) s.item->setVisible(false);
		return;
	}

	const int n = m_arrangement.n;
	const int half = n + 3;
	const int lo = m_currentVirtualIndex - half;
	const int hi = m_currentVirtualIndex + half;
	const int needed = hi - lo + 1;

	while (m_slots.size() < needed)
		m_slots.append(Slot{});

	QHash<int, int> virtualToSlot;
	virtualToSlot.reserve(m_slots.size());
	for (int i = 0; i < m_slots.size(); ++i) {
		if (m_slots[i].active) virtualToSlot.insert(m_slots[i].virtualIndex, i);
	}

	QVector<bool> slotUsedThisPass(m_slots.size(), false);

	for (int v = lo; v <= hi; ++v) {
		auto it = virtualToSlot.find(v);
		if (it != virtualToSlot.end()) {
			slotUsedThisPass[it.value()] = true;
			applyPropertiesToItem(
				m_slots[it.value()].item, m_slots[it.value()].realIndex);
			continue;
		}

		int freeSlot = -1;
		for (int i = 0; i < m_slots.size(); ++i) {
			if (slotUsedThisPass[i]) continue;
			if (m_slots[i].active && m_slots[i].virtualIndex >= lo &&
				m_slots[i].virtualIndex <= hi)
				continue;
			freeSlot = i;
			break;
		}
		if (freeSlot < 0) {
			m_slots.append(Slot{});
			slotUsedThisPass.append(false);
			freeSlot = m_slots.size() - 1;
		}

		updateSlotContent(m_slots[freeSlot], v);
		slotUsedThisPass[freeSlot] = true;
	}

	for (int i = 0; i < m_slots.size(); ++i) {
		if (!slotUsedThisPass[i] && m_slots[i].item) {
			m_slots[i].active = false;
			m_slots[i].item->setVisible(false);
		}
	}

	for (const Slot& s : std::as_const(m_slots))
		positionSlot(s);
}

void CarouselView::cancelAnimations() {
	if (m_glideAnim->state() == QAbstractAnimation::Running)
		m_glideAnim->stop();
	if (m_flickAnim->state() == QAbstractAnimation::Running)
		m_flickAnim->stop();
}

void CarouselView::glideTo(qreal dest) {
	if (std::abs(dest - m_contentX) < 0.5) return;

	cancelAnimations();
	m_glideAnim->setDuration(m_glideDuration);
	m_glideAnim->setStartValue(m_contentX);
	m_glideAnim->setEndValue(dest);
	m_glideAnim->start();
}

void CarouselView::snapToNearest() {
	glideTo(snapTargetX(m_contentX));
}

void CarouselView::goToIndex(int realIndex) {
	const int count = m_model.size();
	if (count == 0) return;
	realIndex = qBound(0, realIndex, count - 1);

	const int curBlock =
		static_cast<int>(std::floor(qreal(m_currentVirtualIndex) / count));
	const int current = m_currentVirtualIndex;
	int target = curBlock * count + realIndex;

	if (target - current > count / 2)
		target -= count;
	else if (current - target > count / 2)
		target += count;

	glideTo(contentXForIndex(target));
}

void CarouselView::incrementCurrentIndex() {
	if (m_model.isEmpty()) return;
	glideTo(contentXForIndex(m_currentVirtualIndex + 1));
}

void CarouselView::decrementCurrentIndex() {
	if (m_model.isEmpty()) return;
	glideTo(contentXForIndex(m_currentVirtualIndex - 1));
}

void CarouselView::jumpToIndex(int realIndex) {
	centerInstantlyOnReal(realIndex);
}

void CarouselView::centerInstantlyOnReal(int realIndex) {
	const int count = m_model.size();
	if (count == 0) return;
	realIndex = qBound(0, realIndex, count - 1);

	cancelAnimations();

	const int curBlock =
		static_cast<int>(std::floor(qreal(m_currentVirtualIndex) / count));
	const int current = m_currentVirtualIndex;
	int target = curBlock * count + realIndex;

	if (target - current > count / 2)
		target -= count;
	else if (current - target > count / 2)
		target += count;

	m_currentVirtualIndex = target;
	m_contentX = contentXForIndex(target);

	const bool changed = (realIndex != m_currentRealIndex);
	m_currentRealIndex = realIndex;
	m_previewRealIndex = realIndex;
	if (changed) emit currentIndexChanged();
	emit previewIndexChanged(realIndex, m_model.at(realIndex));

	relayout();
}

void CarouselView::mousePressEvent(QMouseEvent* event) {
	m_dragging = true;
	m_dragActive = false;
	m_pressPos = event->position();
	m_pressContentX = m_contentX;
	m_dragTimer.start();
	m_lastMoveX = event->position().x();
	m_lastMoveT = 0;
	m_velocity = 0;
	event->accept();
}

void CarouselView::mouseMoveEvent(QMouseEvent* event) {
	if (!m_dragging) return;

	const qreal dx = event->position().x() - m_pressPos.x();
	if (!m_dragActive && std::abs(dx) > kDragThreshold) {
		m_dragActive = true;
		m_pressContentX = m_contentX;
		cancelAnimations();
		grabMouse();
	}
	if (!m_dragActive) return;

	m_contentX = m_pressContentX - dx;
	wrapContentIfNeeded();
	updateCurrentIndexFromContentX(true);
	relayout();

	const qint64 t = m_dragTimer.elapsed();
	const qint64 dt = t - m_lastMoveT;
	if (dt > 0) {
		const qreal instVel =
			(m_lastMoveX - event->position().x()) / (dt / 1000.0);
		m_velocity = m_velocity * 0.7 + instVel * 0.3;
	}
	m_lastMoveX = event->position().x();
	m_lastMoveT = t;

	event->accept();
}

void CarouselView::mouseReleaseEvent(QMouseEvent* event) {
	if (!m_dragging) return;
	m_dragging = false;
	ungrabMouse();

	if (!m_dragActive) {
		event->accept();
		return;
	}
	m_dragActive = false;

	qreal v = qBound(-kMaxFlickVelocity, m_velocity, kMaxFlickVelocity);
	if (std::abs(v) < kMinFlickVelocity) {
		snapToNearest();
		event->accept();
		return;
	}

	const qreal duration = std::abs(v) / (kFlickFriction * 1000.0); // ms
	const qreal distance = (v * (duration / 1000.0)) / 2.0;
	const qreal rawDest = m_contentX + distance;
	const qreal dest = snapTargetX(rawDest);

	cancelAnimations();
	m_flickAnim->setDuration(
		static_cast<int>(qBound<qreal>(120, duration, 900)));
	m_flickAnim->setEasingCurve(QEasingCurve::OutCubic);
	m_flickAnim->setStartValue(m_contentX);
	m_flickAnim->setEndValue(dest);
	m_flickAnim->start();

	event->accept();
}

void CarouselView::mouseUngrabEvent() {
	m_dragging = false;
	m_dragActive = false;
}

void CarouselView::wheelEvent(QWheelEvent* event) {
	const int steps = event->angleDelta().y() / 120;
	if (steps > 0)
		decrementCurrentIndex();
	else if (steps < 0)
		incrementCurrentIndex();
	event->accept();
}

void CarouselView::handleDelegateActivate() {
	QQuickItem* item = qobject_cast<QQuickItem*>(sender());
	if (!item) return;

	for (const Slot& s : std::as_const(m_slots)) {
		if (s.item == item && s.active) {
			if (s.realIndex == m_currentRealIndex) {
				emit activated(s.realIndex, m_model.at(s.realIndex));
			} else {
				goToIndex(s.realIndex);
			}
			return;
		}
	}
}

} // namespace ZShell::components