/*
This file is part of Telegram Desktop,
the official desktop application for the Telegram messaging service.

For license and copyright information please follow this link:
https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
*/
#include "iv/markdown/iv_markdown_article.h"

#include "base/algorithm.h"
#include "iv/markdown/iv_markdown_article_layout_structure.h"
#include "iv/markdown/iv_markdown_article_paint.h"
#include "iv/markdown/iv_markdown_article_selection.h"
#include "iv/markdown/iv_markdown_article_text.h"
#include "iv/markdown/iv_markdown_media_reuse.h"
#include "iv/markdown/iv_markdown_prepare_links.h"
#include "ui/style/style_core_color.h"
#include "ui/style/style_core_scale.h"
#include "ui/widgets/checkbox.h"
#include "ui/basic_click_handlers.h"
#include "ui/dynamic_image.h"

#include "styles/style_iv.h"
#include "styles/style_widgets.h"

#include <algorithm>
#include <limits>
#include <map>
#include <set>
#include <unordered_map>
#include <unordered_set>
#include <utility>

namespace Iv::Markdown {
namespace {

struct PendingHighlightKey {
	QString text;
	QString language;
};

[[nodiscard]] bool operator==(
		const PendingHighlightKey &a,
		const PendingHighlightKey &b) {
	return (a.text == b.text) && (a.language == b.language);
}

struct PendingHighlightKeyHasher {
	[[nodiscard]] size_t operator()(
			const PendingHighlightKey &key) const noexcept;
};

size_t PendingHighlightKeyHasher::operator()(
		const PendingHighlightKey &key) const noexcept {
	auto result = size_t(qHash(key.text));
	result = (result * 1315423911U) ^ size_t(qHash(key.language));
	return result;
}

struct PendingHighlightEntry {
	PendingHighlightKey key;
	std::vector<LaidOutBlock*> blocks;
};

struct RelatedArticleImageState {
	std::shared_ptr<Ui::DynamicImage> thumbnailImage;
	std::shared_ptr<Ui::DynamicImage> previousThumbnailImage;
	std::shared_ptr<Ui::DynamicImage> fullImage;
	std::shared_ptr<Ui::DynamicImage> previousFullImage;
};

[[nodiscard]] size_t CombineHash(size_t accumulator, size_t value) {
	return (accumulator * 1315423911U) ^ value;
}

struct MarkdownArticleScrollOwnerIdentity {
	std::optional<PreparedEditBlockPath> blockPath;
	std::vector<int> preparedPath;

	friend inline bool operator==(
			const MarkdownArticleScrollOwnerIdentity &a,
			const MarkdownArticleScrollOwnerIdentity &b) {
		return (a.blockPath == b.blockPath)
			&& (a.preparedPath == b.preparedPath);
	}
};

struct MarkdownArticleScrollOwnerIdentityHasher {
	[[nodiscard]] size_t operator()(
			const MarkdownArticleScrollOwnerIdentity &value) const noexcept {
		auto result = CombineHash(0, value.blockPath ? 1 : 0);
		if (value.blockPath) {
			for (const auto &step : value.blockPath->container.steps) {
				result = CombineHash(
					result,
					static_cast<size_t>(step.kind));
				result = CombineHash(
					result,
					size_t(step.blockIndex + 1));
				result = CombineHash(
					result,
					size_t(step.listItemIndex + 1));
			}
			result = CombineHash(
				result,
				size_t(value.blockPath->index + 1));
		}
		result = CombineHash(result, size_t(value.preparedPath.size() + 1));
		for (const auto step : value.preparedPath) {
			result = CombineHash(result, size_t(step + 1));
		}
		return result;
	}
};

struct MarkdownArticleHorizontalScrollLookup {
	MarkdownArticleHorizontalScrollHit hit;
	MarkdownArticleScrollOwnerIdentity identity;
	const LaidOutBlock *block = nullptr;
};

void StoreRelatedArticleImageState(
		const LaidOutBlock &block,
		std::unordered_map<uint64, RelatedArticleImageState> *states) {
	if (block.thumbnailPhotoId) {
		(*states)[block.thumbnailPhotoId] = {
			.thumbnailImage = block.thumbnailImage,
			.previousThumbnailImage = block.previousThumbnailImage,
			.fullImage = block.fullImage,
			.previousFullImage = block.previousFullImage,
		};
	}
	for (const auto &child : block.children) {
		StoreRelatedArticleImageState(child, states);
	}
}

void StoreRelatedArticleImageStates(
		const std::vector<LaidOutBlock> &blocks,
		std::unordered_map<uint64, RelatedArticleImageState> *states) {
	for (const auto &block : blocks) {
		StoreRelatedArticleImageState(block, states);
	}
}

void RestoreRelatedArticleImageState(
		LaidOutBlock *block,
		const std::unordered_map<uint64, RelatedArticleImageState> &states) {
	if (block->thumbnailPhotoId) {
		if (const auto i = states.find(block->thumbnailPhotoId);
			i != end(states)) {
			block->thumbnailImage = i->second.thumbnailImage;
			block->previousThumbnailImage = i->second.previousThumbnailImage;
			block->fullImage = i->second.fullImage;
			block->previousFullImage = i->second.previousFullImage;
			block->subscribedThumbnailImage.reset();
			block->thumbnailRequestSize = QSize();
			block->subscribedFullImage.reset();
			block->fullRequestSize = QSize();
		}
	}
	for (auto &child : block->children) {
		RestoreRelatedArticleImageState(&child, states);
	}
}

void RestoreRelatedArticleImageStates(
		std::vector<LaidOutBlock> *blocks,
		const std::unordered_map<uint64, RelatedArticleImageState> &states) {
	for (auto &block : *blocks) {
		RestoreRelatedArticleImageState(&block, states);
	}
}

[[nodiscard]] bool IsDisplayMathSegment(const SelectableSegment &segment) {
	return (segment.kind == SelectableSegmentKind::DisplayMath);
}

[[nodiscard]] bool IsEditableSegment(const SelectableSegment &segment) {
	return segment.isTextLeaf() || IsDisplayMathSegment(segment);
}

template <typename T>
[[nodiscard]] int CompareValues(const T &a, const T &b) {
	return (a < b) ? -1 : (b < a) ? 1 : 0;
}

[[nodiscard]] int ComparePreparedEditBlockContainerStep(
		const PreparedEditBlockContainerStep &a,
		const PreparedEditBlockContainerStep &b) {
	if (const auto result = CompareValues(int(a.kind), int(b.kind));
		result != 0) {
		return result;
	}
	if (const auto result = CompareValues(a.blockIndex, b.blockIndex);
		result != 0) {
		return result;
	}
	return CompareValues(a.listItemIndex, b.listItemIndex);
}

[[nodiscard]] int ComparePreparedEditBlockContainerPath(
		const PreparedEditBlockContainerPath &a,
		const PreparedEditBlockContainerPath &b) {
	const auto count = std::min(a.steps.size(), b.steps.size());
	for (auto i = size_t(0); i != count; ++i) {
		if (const auto result = ComparePreparedEditBlockContainerStep(
				a.steps[i],
				b.steps[i]);
			result != 0) {
			return result;
		}
	}
	return CompareValues(a.steps.size(), b.steps.size());
}

[[nodiscard]] int ComparePreparedEditBlockPath(
		const PreparedEditBlockPath &a,
		const PreparedEditBlockPath &b) {
	if (const auto result = ComparePreparedEditBlockContainerPath(
			a.container,
			b.container);
		result != 0) {
		return result;
	}
	return CompareValues(a.index, b.index);
}

[[nodiscard]] int ComparePreparedEditListItemSource(
		const PreparedEditListItemSource &a,
		const PreparedEditListItemSource &b) {
	if (const auto result = ComparePreparedEditBlockPath(a.block, b.block);
		result != 0) {
		return result;
	}
	return CompareValues(a.listItemIndex, b.listItemIndex);
}

struct PreparedEditListItemSourceLess {
	[[nodiscard]] bool operator()(
			const PreparedEditListItemSource &a,
			const PreparedEditListItemSource &b) const {
		return ComparePreparedEditListItemSource(a, b) < 0;
	}
};

using TaskMarkerRippleRuntimeMap = std::map<
	PreparedEditListItemSource,
	std::shared_ptr<TaskMarkerRippleRuntime>,
	PreparedEditListItemSourceLess>;
using TaskMarkerSourceSet = std::set<
	PreparedEditListItemSource,
	PreparedEditListItemSourceLess>;

void CollectPlaceholderIds(
		const std::vector<LaidOutBlock> &blocks,
		std::unordered_set<uint64> *result) {
	if (!result) {
		return;
	}
	for (const auto &block : blocks) {
		if (block.placeholderId) {
			result->emplace(block.placeholderId.value);
		}
		CollectPlaceholderIds(block.children, result);
	}
}

[[nodiscard]] LaidOutBlock *FindPlaceholderBlock(
		std::vector<LaidOutBlock> *blocks,
		PreparedPlaceholderBlockId id) {
	if (!blocks || !id) {
		return nullptr;
	}
	for (auto &block : *blocks) {
		if (block.placeholderId.value == id.value) {
			return &block;
		}
		if (const auto child = FindPlaceholderBlock(&block.children, id)) {
			return child;
		}
	}
	return nullptr;
}

void CollectTaskMarkerSources(
		const std::vector<LaidOutBlock> &blocks,
		TaskMarkerSourceSet *result) {
	if (!result) {
		return;
	}
	for (const auto &block : blocks) {
		if (block.taskState != TaskState::None && block.editListItem) {
			result->emplace(*block.editListItem);
		}
		CollectTaskMarkerSources(block.children, result);
	}
}

[[nodiscard]] LaidOutBlock *FindListItemBlock(
		std::vector<LaidOutBlock> *blocks,
		const PreparedEditListItemSource &source) {
	if (!blocks) {
		return nullptr;
	}
	for (auto &block : *blocks) {
		if (block.kind == PreparedBlockKind::ListItem
			&& block.editListItem
			&& (*block.editListItem == source)) {
			return &block;
		}
		if (const auto child = FindListItemBlock(&block.children, source)) {
			return child;
		}
	}
	return nullptr;
}

[[nodiscard]] const LaidOutBlock *FindListItemBlock(
		const std::vector<LaidOutBlock> &blocks,
		const PreparedEditListItemSource &source) {
	for (const auto &block : blocks) {
		if (block.kind == PreparedBlockKind::ListItem
			&& block.editListItem
			&& (*block.editListItem == source)) {
			return &block;
		}
		if (const auto child = FindListItemBlock(block.children, source)) {
			return child;
		}
	}
	return nullptr;
}

[[nodiscard]] QRect TaskMarkerRippleRect(
		const LaidOutBlock &block,
		const style::Markdown &st) {
	if (block.markerRect.isEmpty()) {
		return {};
	}
	const auto size = (block.taskMarkerRippleRuntime
			&& !block.taskMarkerRippleRuntime->rippleSize.isEmpty())
		? block.taskMarkerRippleRuntime->rippleSize
		: (block.markerRect.size() + QSize(
			st.list.taskCheck.rippleAreaPadding * 2,
			st.list.taskCheck.rippleAreaPadding * 2));
	return QRect(
		block.markerRect.topLeft() + st::defaultCheckbox.rippleAreaPosition,
		size);
}

[[nodiscard]] const LaidOutBlock *FindPlaceholderBlock(
		const std::vector<LaidOutBlock> &blocks,
		PreparedPlaceholderBlockId id) {
	if (!id) {
		return nullptr;
	}
	for (const auto &block : blocks) {
		if (block.placeholderId.value == id.value) {
			return &block;
		}
		if (const auto child = FindPlaceholderBlock(block.children, id)) {
			return child;
		}
	}
	return nullptr;
}

void AppendRevealLine(
		std::vector<MarkdownArticleRevealLine> *lines,
		int left,
		int width,
		int bottom,
		int baseline,
		bool rtl) {
	if (width <= 0) {
		return;
	}
	const auto previousBottom = lines->empty()
		? std::numeric_limits<int>::lowest()
		: lines->back().bottom;
	if (bottom <= previousBottom) {
		return;
	}
	lines->push_back({
		.left = left,
		.width = width,
		.bottom = bottom,
		.rtl = rtl,
		.baseline = baseline,
	});
}

void AppendGenericRevealBand(
		std::vector<MarkdownArticleRevealLine> *lines,
		QRect rect) {
	if (rect.isEmpty()) {
		return;
	}
	const auto bottom = rect.y() + rect.height();
	AppendRevealLine(
		lines,
		rect.x(),
		rect.width(),
		bottom,
		bottom,
		false);
}

[[nodiscard]] QRect ClipRectToViewport(QRect rect, QRect viewport);

void AppendTextRevealLines(
		std::vector<MarkdownArticleRevealLine> *lines,
		const Ui::Text::String &leaf,
		QRect textRect,
		QRect visibleRect,
		int textWidth) {
	if (textRect.isEmpty() || visibleRect.isEmpty() || (textWidth <= 0)) {
		return;
	}
	const auto geometry = leaf.countLinesGeometry(textWidth, true);
	for (const auto &line : geometry) {
		const auto left = textRect.x() + line.left;
		const auto right = left + line.width;
		const auto visibleLeft = std::max(left, visibleRect.x());
		const auto visibleRight = std::min(
			right,
			visibleRect.x() + visibleRect.width());
		if (visibleRight <= visibleLeft) {
			continue;
		}
		AppendRevealLine(
			lines,
			visibleLeft,
			visibleRight - visibleLeft,
			textRect.y() + line.bottom,
			textRect.y() + line.baseline,
			line.rtl);
	}
}

void AppendBlocksRevealLines(
		const std::vector<LaidOutBlock> &blocks,
		const style::Markdown &st,
		std::vector<MarkdownArticleRevealLine> *lines);

void AppendTableRowRevealLines(
		std::vector<MarkdownArticleRevealLine> *lines,
		const LaidOutBlock &block,
		const style::Markdown &st) {
	if (block.visibleTableRect.isEmpty()) {
		return;
	}
	const auto border = std::max(block.tableBordered ? st.table.border : 0, 0);
	const auto tableBottom = block.visibleTableRect.y()
		+ block.visibleTableRect.height();
	for (const auto &row : block.tableRows) {
		if (row.outer.height() <= 0) {
			continue;
		}
		const auto bottom = std::min(
			row.outer.y() + row.outer.height() + border,
			tableBottom);
		AppendRevealLine(
			lines,
			block.visibleTableRect.x(),
			block.visibleTableRect.width(),
			bottom,
			bottom,
			false);
	}
}

void AppendTableRevealLines(
		std::vector<MarkdownArticleRevealLine> *lines,
		const LaidOutBlock &block,
		const style::Markdown &st) {
	AppendTextRevealLines(
		lines,
		block.leaf,
		block.textRect,
		ClipRectToViewport(block.textRect, block.outer),
		block.textWidth);
	AppendTableRowRevealLines(lines, block, st);
}

void AppendMediaRevealLines(
		std::vector<MarkdownArticleRevealLine> *lines,
		const LaidOutBlock &block) {
	AppendGenericRevealBand(lines, block.visibleMediaRect);
	AppendTextRevealLines(
		lines,
		block.leaf,
		block.textRect,
		ClipRectToViewport(block.textRect, block.outer),
		block.textWidth);
}

void AppendEmbedPostRevealLines(
		std::vector<MarkdownArticleRevealLine> *lines,
		const LaidOutBlock &block,
		const style::Markdown &st) {
	if (!block.headerRect.isEmpty()) {
		const auto bottom = block.headerRect.y() + block.headerRect.height();
		AppendRevealLine(
			lines,
			block.mediaRect.x(),
			block.mediaRect.width(),
			bottom,
			bottom,
			false);
	} else if (block.children.empty()) {
		AppendGenericRevealBand(lines, block.mediaRect);
	}
	AppendBlocksRevealLines(block.children, st, lines);
	AppendTextRevealLines(
		lines,
		block.leaf,
		block.textRect,
		ClipRectToViewport(block.textRect, block.outer),
		block.textWidth);
}

void AppendDetailsRevealLines(
		std::vector<MarkdownArticleRevealLine> *lines,
		const LaidOutBlock &block,
		const style::Markdown &st) {
	AppendTextRevealLines(
		lines,
		block.leaf,
		block.textRect,
		ClipRectToViewport(block.textRect, block.headerRect),
		block.textWidth);
	AppendBlocksRevealLines(block.children, st, lines);
}

void AppendBlockRevealLines(
		std::vector<MarkdownArticleRevealLine> *lines,
		const LaidOutBlock &block,
		const style::Markdown &st) {
	switch (block.kind) {
	case PreparedBlockKind::Paragraph:
	case PreparedBlockKind::Thinking:
	case PreparedBlockKind::Heading:
	case PreparedBlockKind::CodeBlock:
		AppendTextRevealLines(
			lines,
			block.leaf,
			block.textRect,
			(block.kind == PreparedBlockKind::CodeBlock)
				? ClipRectToViewport(block.textRect, block.contentRect)
				: ClipRectToViewport(block.textRect, block.outer),
			block.textWidth);
		break;
	case PreparedBlockKind::Rule:
		AppendGenericRevealBand(lines, block.outer);
		break;
	case PreparedBlockKind::List:
	case PreparedBlockKind::ListItem:
	case PreparedBlockKind::Quote:
		AppendBlocksRevealLines(block.children, st, lines);
		break;
	case PreparedBlockKind::DisplayMath:
		AppendGenericRevealBand(lines, block.visibleFormulaRect);
		break;
	case PreparedBlockKind::Table:
		AppendTableRevealLines(lines, block, st);
		break;
	case PreparedBlockKind::Details:
		AppendDetailsRevealLines(lines, block, st);
		break;
	case PreparedBlockKind::Photo:
	case PreparedBlockKind::Video:
	case PreparedBlockKind::Audio:
	case PreparedBlockKind::Map:
	case PreparedBlockKind::Channel:
	case PreparedBlockKind::GroupedMedia:
	case PreparedBlockKind::Placeholder:
		AppendMediaRevealLines(lines, block);
		break;
	case PreparedBlockKind::RelatedArticle:
		AppendGenericRevealBand(lines, block.visibleMediaRect);
		break;
	case PreparedBlockKind::EmbedPost:
		AppendEmbedPostRevealLines(lines, block, st);
		break;
	}
}

void AppendBlocksRevealLines(
		const std::vector<LaidOutBlock> &blocks,
		const style::Markdown &st,
		std::vector<MarkdownArticleRevealLine> *lines) {
	for (const auto &block : blocks) {
		AppendBlockRevealLines(lines, block, st);
	}
}

[[nodiscard]] std::vector<MarkdownArticleRevealLine> CollectRevealLines(
		const std::vector<LaidOutBlock> &blocks,
		const style::Markdown &st) {
	auto result = std::vector<MarkdownArticleRevealLine>();
	AppendBlocksRevealLines(blocks, st, &result);
	return result;
}

[[nodiscard]] PendingHighlightKey PendingHighlightKeyForBlock(
		const LaidOutBlock &block) {
	return {
		.text = CodeBlockDisplayText(block.copyText),
		.language = block.codeLanguage,
	};
}

[[nodiscard]] Ui::Text::StateResult TextStateAtLeaf(
		const Ui::Text::String &leaf,
		QRect rect,
		int width,
		QPoint point,
		Ui::Text::StateRequest::Flags flags,
		style::align align = style::al_left,
		bool clampToRect = false) {
	if (rect.isEmpty()) {
		return {};
	}
	if (!rect.contains(point)) {
		if (!clampToRect) {
			return {};
		}
		point.setX(std::clamp(point.x(), rect.left(), rect.right()));
		point.setY(std::clamp(point.y(), rect.top(), rect.bottom()));
	}
	auto request = Ui::Text::StateRequest();
	request.align = align;
	request.flags = flags | Ui::Text::StateRequest::Flag::BreakEverywhere;
	const auto availableWidth = std::max(width, 1);
	return leaf.getState(
		point - rect.topLeft(),
		TextGeometry(availableWidth),
		request);
}

[[nodiscard]] SegmentSpan FullSegmentSpan(
		const std::vector<SelectableSegment> &segments) {
	return { 0, int(segments.size()) };
}

void RebuildVisibleSegmentLookup(
		const std::vector<SelectableSegment> &segments,
		std::vector<int> *tops,
		std::vector<int> *bottoms) {
	if (!tops || !bottoms) {
		return;
	}
	tops->clear();
	bottoms->clear();
	tops->reserve(segments.size());
	bottoms->reserve(segments.size());
	auto runningBottom = std::numeric_limits<int>::lowest();
	for (const auto &segment : segments) {
		tops->push_back(segment.outerRect.top());
		runningBottom = std::max(runningBottom, segment.outerRect.bottom());
		bottoms->push_back(runningBottom);
	}
}

[[nodiscard]] SegmentSpan LookupVisibleSegmentSpan(
		const std::vector<int> &tops,
		const std::vector<int> &bottoms,
		LogicalVisibleRange range) {
	if (tops.empty() || bottoms.empty() || (range.bottom <= range.top)) {
		return {};
	}
	const auto from = int(std::lower_bound(
		bottoms.begin(),
		bottoms.end(),
		range.top) - bottoms.begin());
	if (from >= int(tops.size())) {
		return {};
	}
	const auto till = int(std::upper_bound(
		tops.begin() + from,
		tops.end(),
		range.bottom - 1) - tops.begin());
	return (from < till) ? SegmentSpan{ from, till } : SegmentSpan();
}

[[nodiscard]] std::optional<PreparedLink> PreparedLinkForMediaActivation(
		const MediaActivation &activation) {
	if (activation.kind != MediaActivationKind::ExternalUrl
		|| activation.url.isEmpty()) {
		return std::nullopt;
	}
	if (const auto prepared = ClassifiedLink(0, activation.url, nullptr);
		prepared.kind == PreparedLinkKind::External) {
		return prepared;
	}
	return PreparedLink{
		.kind = PreparedLinkKind::External,
		.target = activation.url,
		.copyText = UrlClickHandler::EncodeForOpening(activation.url),
		.entityType = EntityType::Url,
		.shown = EntityLinkShown::Full,
	};
}

[[nodiscard]] std::optional<PreparedLink> PreparedLinkForDetailsBlock(
		const SelectableSegment &segment) {
	if (!segment.block
		|| segment.block->kind != PreparedBlockKind::Details
		|| segment.block->anchorId.isEmpty()) {
		return std::nullopt;
	}
	return PreparedLink{
		.kind = PreparedLinkKind::ToggleDetails,
		.target = segment.block->anchorId,
	};
}

[[nodiscard]] QRect LogicalTextRectForSegment(const SelectableSegment &segment) {
	if (segment.cell) {
		return segment.cell->textRect;
	} else if (!segment.block) {
		return segment.textRect;
	} else if (segment.leaf == &segment.block->leaf) {
		return segment.block->textRect;
	} else if (segment.leaf == &segment.block->labelLeaf) {
		return segment.block->labelRect;
	} else if (segment.leaf == &segment.block->subtitleLeaf) {
		return segment.block->subtitleRect;
	} else if (segment.leaf == &segment.block->actionLeaf) {
		return segment.block->actionRect;
	}
	return segment.textRect;
}

[[nodiscard]] MarkdownArticleHitTestResult HitSegmentBoundary(
		const SelectableSegment &segment,
		int offset) {
	auto result = MarkdownArticleHitTestResult();
	result.segmentIndex = segment.index;
	result.forcedOffset = std::clamp(offset, 0, SegmentLength(segment));
	result.state.uponSymbol = true;
	result.state.afterSymbol = (result.forcedOffset > 0);
	return result;
}

[[nodiscard]] MarkdownArticleHitTestResult HitTextSegment(
		const SelectableSegment &segment,
		QPoint point,
		Ui::Text::StateRequest::Flags flags) {
	if (!segment.isTextLeaf() || !segment.outerRect.contains(point)) {
		return {};
	}
	const auto insideText = segment.textRect.contains(point);
	if (!insideText
		&& !(flags & Ui::Text::StateRequest::Flag::LookupSymbol)) {
		return {};
	}
	auto result = MarkdownArticleHitTestResult();
	result.segmentIndex = segment.index;
	const auto logicalRect = LogicalTextRectForSegment(segment);
	result.state = TextStateAtLeaf(
		*segment.leaf,
		logicalRect,
		segment.textWidth,
		point,
		flags,
		segment.align,
		!insideText);
	if (!insideText) {
		result.state.link = nullptr;
	}
	result.preparedLink = ExtractPreparedLink(result.state.link);
	if (!result.preparedLink
		&& (flags & Ui::Text::StateRequest::Flag::LookupLink)) {
		if (const auto prepared = PreparedLinkForDetailsBlock(segment)) {
			result.preparedLink = prepared;
			if (!insideText) {
				result.state.link = CreatePreparedLinkHandler(*prepared);
			}
		}
	}
	result.direct = true;
	return result;
}

[[nodiscard]] MarkdownArticleHitTestResult HitCodeBlockHeader(
		const SelectableSegment &segment,
		QPoint point,
		Ui::Text::StateRequest::Flags flags) {
	if (segment.kind != SelectableSegmentKind::CodeBlock
		|| !segment.block
		|| !(flags & Ui::Text::StateRequest::Flag::LookupSymbol)
		|| !segment.block->headerRect.contains(point)) {
		return {};
	}
	auto result = MarkdownArticleHitTestResult();
	result.segmentIndex = segment.index;
	result.forcedOffset = 0;
	result.state.uponSymbol = true;
	result.direct = true;
	result.codeHeaderCopy = true;
	return result;
}

[[nodiscard]] MarkdownArticleHitTestResult HitBlockSegment(
		const SelectableSegment &segment,
		QPoint point,
		Ui::Text::StateRequest::Flags flags) {
	if (segment.isTextLeaf()
		|| !(flags & Ui::Text::StateRequest::Flag::LookupSymbol)
		|| !segment.outerRect.contains(point)) {
		return {};
	}
	const auto after = (point.y() > segment.outerRect.center().y())
		|| ((point.y() == segment.outerRect.center().y())
			&& (point.x() >= segment.outerRect.center().x()));
	auto result = HitSegmentBoundary(
		segment,
		after ? SegmentLength(segment) : 0);
	const auto applyActivation = [&](const MediaActivation &activation) {
		result.mediaActivation = activation;
		if (const auto prepared = PreparedLinkForMediaActivation(activation)) {
			result.preparedLink = prepared;
			result.state.link = CreatePreparedLinkHandler(*prepared);
		}
	};
	if (segment.block) {
		if (segment.block->kind == PreparedBlockKind::RelatedArticle
			&& segment.block->preparedLink) {
			result.preparedLink = segment.block->preparedLink;
			result.state.link = segment.block->preparedLinkHandler;
			result.mediaActivation = {};
		} else if (segment.block->mediaBlock) {
			if (const auto link = segment.block->mediaBlock->linkAt(point)) {
				result.state.link = link;
				result.preparedLink = std::nullopt;
				result.mediaActivation = {};
			} else {
				applyActivation(segment.block->mediaBlock->activationAt(point));
			}
		} else {
			applyActivation(segment.block->activation);
			if (result.mediaActivation.kind == MediaActivationKind::Embed
				&& segment.block->placeholderRuntime) {
				result.state.link = segment.block->placeholderRuntime->clickHandler;
				result.placeholderLocalPoint = point
					- segment.block->mediaRect.topLeft();
			}
		}
	}
	result.direct = true;
	return result;
}

[[nodiscard]] MarkdownArticleHitTestResult HitSegmentFallback(
		const std::vector<SelectableSegment> &segments,
		SegmentSpan span,
		QPoint point) {
	if (segments.empty() || span.empty()) {
		return {};
	}
	for (auto i = span.from; i != span.till; ++i) {
		const auto &segment = segments[i];
		const auto &rect = segment.outerRect;
		if (point.y() < rect.top()) {
			return HitSegmentBoundary(segment, 0);
		}
		if (point.y() <= rect.bottom()) {
			if (point.x() < rect.left()) {
				return HitSegmentBoundary(segment, 0);
			} else if (point.x() > rect.right()) {
				return HitSegmentBoundary(
					segment,
					SegmentLength(segment));
			}
		}
	}
	return HitSegmentBoundary(
		segments[span.till - 1],
		SegmentLength(segments[span.till - 1]));
}

[[nodiscard]] bool ContainsPoint(QRect rect, QPoint point) {
	return !rect.isEmpty() && rect.contains(point);
}

struct ActiveHorizontalScrollOwnerState {
	QRect viewport;
	int shift = 0;
};

[[nodiscard]] QRect TranslateRect(QRect rect, int shift) {
	return rect.isEmpty() ? rect : rect.translated(shift, 0);
}

[[nodiscard]] QRect ClipRectToViewport(QRect rect, QRect viewport) {
	if (rect.isEmpty() || viewport.isEmpty()) {
		return QRect();
	}
	const auto left = std::max(rect.x(), viewport.x());
	const auto right = std::min(
		rect.x() + rect.width(),
		viewport.x() + viewport.width());
	return QRect(
		left,
		rect.y(),
		std::max(right - left, 0),
		rect.height());
}

[[nodiscard]] QPoint TranslatePoint(QPoint point, int shift) {
	return point + QPoint(shift, 0);
}

[[nodiscard]] QPoint ClampPointToViewport(QPoint point, QRect viewport) {
	if (viewport.isEmpty()) {
		return point;
	}
	const auto right = viewport.x() + std::max(viewport.width() - 1, 0);
	point.setX(std::clamp(point.x(), viewport.x(), right));
	return point;
}

[[nodiscard]] QRect BaseVisibleTableRect(const LaidOutBlock &block) {
	if (!block.scrollViewportRect.isEmpty()) {
		return block.scrollViewportRect;
	} else if (block.logicalGeometry.tableRect.isEmpty()) {
		return QRect();
	}
	return QRect(
		block.logicalGeometry.tableRect.x(),
		block.logicalGeometry.tableRect.y(),
		std::min(
			block.logicalGeometry.tableRect.width(),
			std::max(block.logicalGeometry.outer.width(), 1)),
		block.logicalGeometry.tableRect.height());
}

void RestoreLogicalBlockGeometry(LaidOutBlock *block) {
	block->outer = block->logicalGeometry.outer;
	block->headerRect = block->logicalGeometry.headerRect;
	block->bodyRect = block->logicalGeometry.bodyRect;
	block->iconRect = block->logicalGeometry.iconRect;
	block->textRect = block->logicalGeometry.textRect;
	block->labelRect = block->logicalGeometry.labelRect;
	block->subtitleRect = block->logicalGeometry.subtitleRect;
	block->actionRect = block->logicalGeometry.actionRect;
	block->markerRect = block->logicalGeometry.markerRect;
	block->contentRect = block->logicalGeometry.contentRect;
	block->formulaRect = block->logicalGeometry.formulaRect;
	block->tableRect = block->logicalGeometry.tableRect;
	block->mediaRect = block->logicalGeometry.mediaRect;
	block->thumbnailRect = block->logicalGeometry.thumbnailRect;
	block->markerCenter = block->logicalGeometry.markerCenter;
	block->visibleFormulaRect = block->formulaRect.intersected(
		block->contentRect);
	block->visibleTableRect = BaseVisibleTableRect(*block);
	block->tableScrollbarTrackRect = block->scrollScrollbarTrackRect;
	block->tableScrollbarThumbRect = QRect();
	block->scrollScrollbarThumbRect = QRect();
	block->visibleMediaRect = block->mediaRect;
	for (auto &row : block->tableRows) {
		row.outer = row.logicalOuter;
		for (auto &cell : row.cells) {
			cell.outer = cell.logicalOuter;
			cell.textRect = cell.logicalTextRect;
		}
	}
}

[[nodiscard]] bool ScrollOwnerMovesOwnContent(PreparedBlockKind kind) {
	switch (kind) {
	case PreparedBlockKind::Paragraph:
	case PreparedBlockKind::Thinking:
	case PreparedBlockKind::Heading:
	case PreparedBlockKind::CodeBlock:
	case PreparedBlockKind::DisplayMath:
	case PreparedBlockKind::Table:
		return true;
	case PreparedBlockKind::Rule:
	case PreparedBlockKind::List:
	case PreparedBlockKind::ListItem:
	case PreparedBlockKind::Quote:
	case PreparedBlockKind::Photo:
	case PreparedBlockKind::Video:
	case PreparedBlockKind::Audio:
	case PreparedBlockKind::Map:
	case PreparedBlockKind::Channel:
	case PreparedBlockKind::GroupedMedia:
	case PreparedBlockKind::RelatedArticle:
	case PreparedBlockKind::EmbedPost:
	case PreparedBlockKind::Placeholder:
	case PreparedBlockKind::Details:
		return false;
	}
	return false;
}

[[nodiscard]] bool ScrollOwnerMovesChildren(PreparedBlockKind kind) {
	switch (kind) {
	case PreparedBlockKind::List:
	case PreparedBlockKind::ListItem:
	case PreparedBlockKind::Quote:
	case PreparedBlockKind::EmbedPost:
	case PreparedBlockKind::Details:
		return true;
	case PreparedBlockKind::Paragraph:
	case PreparedBlockKind::Thinking:
	case PreparedBlockKind::Heading:
	case PreparedBlockKind::CodeBlock:
	case PreparedBlockKind::Rule:
	case PreparedBlockKind::DisplayMath:
	case PreparedBlockKind::Table:
	case PreparedBlockKind::Photo:
	case PreparedBlockKind::Video:
	case PreparedBlockKind::Audio:
	case PreparedBlockKind::Map:
	case PreparedBlockKind::Channel:
	case PreparedBlockKind::GroupedMedia:
	case PreparedBlockKind::RelatedArticle:
	case PreparedBlockKind::Placeholder:
		return false;
	}
	return false;
}

void ApplyTranslatedDescendantGeometry(
		LaidOutBlock *block,
		const ActiveHorizontalScrollOwnerState &state) {
	block->outer = ClipRectToViewport(
		TranslateRect(block->outer, state.shift),
		state.viewport);
	block->headerRect = ClipRectToViewport(
		TranslateRect(block->headerRect, state.shift),
		state.viewport);
	block->bodyRect = ClipRectToViewport(
		TranslateRect(block->bodyRect, state.shift),
		state.viewport);
	block->iconRect = ClipRectToViewport(
		TranslateRect(block->iconRect, state.shift),
		state.viewport);
	block->contentRect = ClipRectToViewport(
		TranslateRect(block->contentRect, state.shift),
		state.viewport);
	block->textRect = TranslateRect(block->textRect, state.shift);
	block->labelRect = TranslateRect(block->labelRect, state.shift);
	block->subtitleRect = TranslateRect(block->subtitleRect, state.shift);
	block->actionRect = TranslateRect(block->actionRect, state.shift);
	block->markerRect = ClipRectToViewport(
		TranslateRect(block->markerRect, state.shift),
		state.viewport);
	block->formulaRect = TranslateRect(block->formulaRect, state.shift);
	block->tableRect = TranslateRect(block->tableRect, state.shift);
	block->mediaRect = TranslateRect(block->mediaRect, state.shift);
	block->thumbnailRect = TranslateRect(block->thumbnailRect, state.shift);
	block->markerCenter = ClampPointToViewport(
		TranslatePoint(block->markerCenter, state.shift),
		state.viewport);
	block->visibleFormulaRect = ClipRectToViewport(
		block->formulaRect,
		state.viewport);
	block->visibleTableRect = ClipRectToViewport(
		TranslateRect(BaseVisibleTableRect(*block), state.shift),
		state.viewport);
	block->visibleMediaRect = ClipRectToViewport(
		block->mediaRect,
		state.viewport);
	for (auto &row : block->tableRows) {
		row.outer = ClipRectToViewport(
			TranslateRect(row.logicalOuter, state.shift),
			state.viewport);
		for (auto &cell : row.cells) {
			cell.outer = ClipRectToViewport(
				TranslateRect(cell.logicalOuter, state.shift),
				state.viewport);
			cell.textRect = TranslateRect(cell.logicalTextRect, state.shift);
		}
	}
}

void ApplyOwnerContentGeometry(
		LaidOutBlock *block,
		const ActiveHorizontalScrollOwnerState &state) {
	switch (block->kind) {
	case PreparedBlockKind::Paragraph:
	case PreparedBlockKind::Thinking:
	case PreparedBlockKind::Heading:
	case PreparedBlockKind::CodeBlock:
		block->textRect = TranslateRect(block->logicalGeometry.textRect, state.shift);
		break;
	case PreparedBlockKind::DisplayMath:
		block->formulaRect = TranslateRect(
			block->logicalGeometry.formulaRect,
			state.shift);
		block->textRect = TranslateRect(block->logicalGeometry.textRect, state.shift);
		block->visibleFormulaRect = ClipRectToViewport(
			block->formulaRect,
			state.viewport);
		break;
	case PreparedBlockKind::Table:
		block->visibleTableRect = block->scrollViewportRect;
		block->tableScrollbarTrackRect = block->scrollScrollbarTrackRect;
		for (auto &row : block->tableRows) {
			row.outer = ClipRectToViewport(
				TranslateRect(row.logicalOuter, state.shift),
				block->visibleTableRect);
			for (auto &cell : row.cells) {
				cell.outer = ClipRectToViewport(
					TranslateRect(cell.logicalOuter, state.shift),
					block->visibleTableRect);
				cell.textRect = TranslateRect(
					cell.logicalTextRect,
					state.shift);
			}
		}
		break;
	case PreparedBlockKind::Rule:
	case PreparedBlockKind::List:
	case PreparedBlockKind::ListItem:
	case PreparedBlockKind::Quote:
	case PreparedBlockKind::Photo:
	case PreparedBlockKind::Video:
	case PreparedBlockKind::Audio:
	case PreparedBlockKind::Map:
	case PreparedBlockKind::Channel:
	case PreparedBlockKind::GroupedMedia:
	case PreparedBlockKind::RelatedArticle:
	case PreparedBlockKind::EmbedPost:
	case PreparedBlockKind::Placeholder:
	case PreparedBlockKind::Details:
		break;
	}
}

[[nodiscard]] bool ValidBlockPath(const PreparedEditBlockPath &path) {
	return (path.index >= 0);
}

[[nodiscard]] PreparedEditBlockSource EditBlockSourceFromPath(
		PreparedEditBlockPath path) {
	return { .path = std::move(path) };
}

[[nodiscard]] PreparedEditTableRowSource EditTableRowSourceFromCell(
		const PreparedEditTableCellSource &source) {
	return {
		.block = source.block,
		.tableRowIndex = source.tableRowIndex,
	};
}

[[nodiscard]] PreparedEditHit WithLeaf(
		PreparedEditHit hit,
		const std::optional<PreparedEditLeafSource> &leaf) {
	if (leaf) {
		hit.leaf = *leaf;
	}
	return hit;
}

[[nodiscard]] PreparedEditHit EditHitFromBlockSource(
		const PreparedEditBlockSource &source,
		const std::optional<PreparedEditLeafSource> &leaf = std::nullopt) {
	if (!ValidBlockPath(source.path)) {
		return {};
	}
	auto result = PreparedEditHit();
	result.kind = PreparedEditHitKind::Block;
	result.block = source;
	return WithLeaf(std::move(result), leaf);
}

[[nodiscard]] PreparedEditHit EditHitFromListItemSource(
		const PreparedEditListItemSource &source,
		const std::optional<PreparedEditLeafSource> &leaf = std::nullopt) {
	if (!ValidBlockPath(source.block) || source.listItemIndex < 0) {
		return {};
	}
	auto result = PreparedEditHit();
	result.kind = PreparedEditHitKind::ListItem;
	result.block = EditBlockSourceFromPath(source.block);
	result.listItem = source;
	return WithLeaf(std::move(result), leaf);
}

[[nodiscard]] PreparedEditHit EditHitFromTableRowSource(
		const PreparedEditTableRowSource &source,
		const std::optional<PreparedEditLeafSource> &leaf = std::nullopt) {
	if (!ValidBlockPath(source.block) || source.tableRowIndex < 0) {
		return {};
	}
	auto result = PreparedEditHit();
	result.kind = PreparedEditHitKind::TableRow;
	result.block = EditBlockSourceFromPath(source.block);
	result.tableRow = source;
	return WithLeaf(std::move(result), leaf);
}

[[nodiscard]] PreparedEditHit EditHitFromTableCellSource(
		const PreparedEditTableCellSource &source,
		const std::optional<PreparedEditLeafSource> &leaf = std::nullopt) {
	if (!ValidBlockPath(source.block)
		|| source.tableRowIndex < 0
		|| source.tableCellIndex < 0) {
		return {};
	}
	auto result = PreparedEditHit();
	result.kind = PreparedEditHitKind::TableCell;
	result.block = EditBlockSourceFromPath(source.block);
	result.tableRow = EditTableRowSourceFromCell(source);
	result.tableCell = source;
	return WithLeaf(std::move(result), leaf);
}

[[nodiscard]] PreparedEditHit EditHitFromLeafSource(
		const PreparedEditLeafSource &source,
		bool preferLeaf) {
	if (!ValidBlockPath(source.block)) {
		return {};
	}
	switch (source.kind) {
	case PreparedEditLeafKind::ListItemText:
		return EditHitFromListItemSource(
			PreparedEditListItemSource{
				.block = source.block,
				.listItemIndex = source.listItemIndex,
			},
			source);
	case PreparedEditLeafKind::TableCellText:
		return EditHitFromTableCellSource(
			PreparedEditTableCellSource{
				.block = source.block,
				.tableRowIndex = source.tableRowIndex,
				.tableCellIndex = source.tableCellIndex,
			},
			source);
	case PreparedEditLeafKind::BlockText:
	case PreparedEditLeafKind::BlockCaption:
	case PreparedEditLeafKind::MathFormula: {
		auto result = PreparedEditHit();
		result.kind = preferLeaf
			? PreparedEditHitKind::Leaf
			: PreparedEditHitKind::Block;
		result.block = EditBlockSourceFromPath(source.block);
		result.leaf = source;
		return result;
	} break;
	}
	return {};
}

[[nodiscard]] PreparedEditHit EditFallbackHitForBlock(
		const LaidOutBlock &block);

[[nodiscard]] PreparedEditHit EditHitForBlock(
		const LaidOutBlock &block,
		QPoint point);

[[nodiscard]] PreparedEditBlockContainerPath ListItemChildContainer(
		const PreparedEditListItemSource &source) {
	auto result = source.block.container;
	result.steps.push_back({
		.kind = PreparedEditBlockContainerKind::ListItemChildren,
		.blockIndex = source.block.index,
		.listItemIndex = source.listItemIndex,
	});
	return result;
}

[[nodiscard]] bool HitHasRealBlockInContainer(
		const PreparedEditHit &hit,
		const PreparedEditBlockContainerPath &container) {
	return hit.block
		&& (hit.block->path.container.steps.size() >= container.steps.size())
		&& std::equal(
			container.steps.begin(),
			container.steps.end(),
			hit.block->path.container.steps.begin());
}

[[nodiscard]] PreparedEditHit EditHitForBlocks(
		const std::vector<LaidOutBlock> &blocks,
		QPoint point) {
	auto fallback = PreparedEditHit();
	auto fallbackDistance = std::numeric_limits<int>::max();
	for (const auto &block : blocks) {
		if (ContainsPoint(block.outer, point)) {
			return EditHitForBlock(block, point);
		}
		const auto candidate = EditFallbackHitForBlock(block);
		if (!candidate.valid()) {
			continue;
		}
		const auto distance = (point.y() < block.outer.top())
			? (block.outer.top() - point.y())
			: (point.y() > block.outer.bottom())
			? (point.y() - block.outer.bottom())
			: 0;
		if (distance < fallbackDistance) {
			fallback = candidate;
			fallbackDistance = distance;
		}
	}
	return fallback;
}

[[nodiscard]] PreparedEditHit EditFallbackHitForBlock(
		const LaidOutBlock &block) {
	if (block.editListItem) {
		return EditHitFromListItemSource(*block.editListItem);
	} else if (block.editBlock) {
		return EditHitFromBlockSource(*block.editBlock);
	} else if (block.editLeaf) {
		return EditHitFromLeafSource(*block.editLeaf, false);
	}
	return {};
}

[[nodiscard]] MarkdownArticleEditControlHit EditControlHitForBlocks(
		const std::vector<LaidOutBlock> &blocks,
		QPoint point);

[[nodiscard]] QRect VisibleTextRectForBlock(const LaidOutBlock &block) {
	switch (block.kind) {
	case PreparedBlockKind::CodeBlock:
		return ClipRectToViewport(block.textRect, block.contentRect);
	case PreparedBlockKind::Details:
		return ClipRectToViewport(block.textRect, block.headerRect);
	case PreparedBlockKind::Paragraph:
	case PreparedBlockKind::Thinking:
	case PreparedBlockKind::Heading:
	case PreparedBlockKind::Rule:
	case PreparedBlockKind::DisplayMath:
	case PreparedBlockKind::Table:
	case PreparedBlockKind::Photo:
	case PreparedBlockKind::Video:
	case PreparedBlockKind::Audio:
	case PreparedBlockKind::Map:
	case PreparedBlockKind::Channel:
	case PreparedBlockKind::GroupedMedia:
	case PreparedBlockKind::RelatedArticle:
	case PreparedBlockKind::EmbedPost:
	case PreparedBlockKind::Placeholder:
	case PreparedBlockKind::List:
	case PreparedBlockKind::ListItem:
	case PreparedBlockKind::Quote:
		return ClipRectToViewport(block.textRect, block.outer);
	}
	return ClipRectToViewport(block.textRect, block.outer);
}

[[nodiscard]] PreparedEditHit EditHitForTableCell(
		const LaidOutTableCell &cell,
		QPoint point) {
	auto leaf = ContainsPoint(ClipRectToViewport(cell.textRect, cell.outer), point)
		? cell.editLeaf
		: std::optional<PreparedEditLeafSource>();
	if (cell.editCell) {
		return EditHitFromTableCellSource(*cell.editCell, leaf);
	} else if (leaf) {
		return EditHitFromLeafSource(*leaf, false);
	}
	return {};
}

[[nodiscard]] PreparedEditHit EditHitForTableBlock(
		const LaidOutBlock &block,
		QPoint point) {
	if (ContainsPoint(VisibleTextRectForBlock(block), point) && block.editLeaf) {
		if (block.editBlock) {
			return EditHitFromBlockSource(*block.editBlock, block.editLeaf);
		}
		return EditHitFromLeafSource(*block.editLeaf, false);
	}
	for (const auto &row : block.tableRows) {
		for (const auto &cell : row.cells) {
			if (ContainsPoint(cell.outer, point)) {
				if (const auto result = EditHitForTableCell(cell, point);
					result.valid()) {
					return result;
				}
			}
		}
	}
	for (const auto &row : block.tableRows) {
		if (ContainsPoint(row.outer, point)) {
			if (row.editRow) {
				return EditHitFromTableRowSource(*row.editRow);
			}
		}
	}
	return EditFallbackHitForBlock(block);
}

[[nodiscard]] PreparedEditHit EditHitForListBlock(
		const LaidOutBlock &block,
		QPoint point) {
	if (!block.children.empty()) {
		if (const auto result = EditHitForBlocks(block.children, point);
			result.valid()) {
			return result;
		}
	}
	return EditFallbackHitForBlock(block);
}

[[nodiscard]] PreparedEditHit EditHitForListItemBlock(
		const LaidOutBlock &block,
		QPoint point) {
	const auto listItemHit = EditFallbackHitForBlock(block);
	if (ContainsPoint(block.contentRect, point) && !block.children.empty()) {
		if (const auto childHit = EditHitForBlocks(block.children, point);
			childHit.valid()) {
			if (block.editListItem
				&& HitHasRealBlockInContainer(
					childHit,
					ListItemChildContainer(*block.editListItem))) {
				return childHit;
			}
			return childHit.leaf
				? WithLeaf(listItemHit, childHit.leaf)
				: listItemHit;
		}
	}
	return listItemHit;
}

[[nodiscard]] PreparedEditHit EditHitForQuoteBlock(
		const LaidOutBlock &block,
		QPoint point) {
	if (ContainsPoint(block.contentRect, point) && !block.children.empty()) {
		if (const auto childHit = EditHitForBlocks(block.children, point);
			childHit.valid()) {
			return childHit;
		}
	}
	return EditFallbackHitForBlock(block);
}

[[nodiscard]] PreparedEditHit EditHitForDetailsBlock(
		const LaidOutBlock &block,
		QPoint point) {
	if (ContainsPoint(block.headerRect, point)) {
		if (ContainsPoint(VisibleTextRectForBlock(block), point) && block.editLeaf) {
			if (block.editBlock) {
				return EditHitFromBlockSource(*block.editBlock, block.editLeaf);
			}
			return EditHitFromLeafSource(*block.editLeaf, false);
		}
		return EditFallbackHitForBlock(block);
	}
	if (ContainsPoint(block.contentRect, point) && !block.children.empty()) {
		if (const auto childHit = EditHitForBlocks(block.children, point);
			childHit.valid()) {
			return childHit;
		}
	}
	return EditFallbackHitForBlock(block);
}

[[nodiscard]] MarkdownArticleEditControlHit EditControlHitForListItemBlock(
		const LaidOutBlock &block,
		QPoint point) {
	if (block.taskState != TaskState::None
		&& block.editListItem
		&& ContainsPoint(block.markerRect, point)) {
		return {
			.kind = MarkdownArticleEditControlHitKind::TaskMarker,
			.listItem = *block.editListItem,
		};
	}
	if (!block.children.empty()) {
		return EditControlHitForBlocks(block.children, point);
	}
	return {};
}

[[nodiscard]] MarkdownArticleEditControlHit EditControlHitForDetailsBlock(
		const LaidOutBlock &block,
		QPoint point) {
	if (ContainsPoint(block.headerRect, point) && block.editBlock) {
		const auto leftWidth = std::max(
			block.textRect.left() - block.headerRect.left(),
			0);
		const auto leftToggleRect = QRect(
			block.headerRect.left(),
			block.headerRect.top(),
			leftWidth,
			block.headerRect.height());
		if (ContainsPoint(leftToggleRect, point)
			|| (!block.actionRect.isEmpty()
				&& ContainsPoint(block.actionRect, point))) {
			return {
				.kind = MarkdownArticleEditControlHitKind::DetailsToggle,
				.block = *block.editBlock,
			};
		}
		return {};
	}
	if (!block.children.empty()) {
		return EditControlHitForBlocks(block.children, point);
	}
	return {};
}

[[nodiscard]] MarkdownArticleEditControlHit EditControlHitForBlock(
		const LaidOutBlock &block,
		QPoint point) {
	switch (block.kind) {
	case PreparedBlockKind::ListItem:
		return EditControlHitForListItemBlock(block, point);
	case PreparedBlockKind::Details:
		return EditControlHitForDetailsBlock(block, point);
	default:
		if (!block.children.empty()) {
			return EditControlHitForBlocks(block.children, point);
		}
		return {};
	}
}

[[nodiscard]] MarkdownArticleEditControlHit EditControlHitForBlocks(
		const std::vector<LaidOutBlock> &blocks,
		QPoint point) {
	for (const auto &block : blocks) {
		if (ContainsPoint(block.outer, point)) {
			return EditControlHitForBlock(block, point);
		}
	}
	return {};
}

[[nodiscard]] PreparedEditHit EditHitForBlock(
		const LaidOutBlock &block,
		QPoint point) {
	switch (block.kind) {
	case PreparedBlockKind::List:
		return EditHitForListBlock(block, point);
	case PreparedBlockKind::ListItem:
		return EditHitForListItemBlock(block, point);
	case PreparedBlockKind::Quote:
		return EditHitForQuoteBlock(block, point);
	case PreparedBlockKind::Table:
		return EditHitForTableBlock(block, point);
	case PreparedBlockKind::Details:
		return EditHitForDetailsBlock(block, point);
	case PreparedBlockKind::DisplayMath:
		if (block.editLeaf) {
			return EditHitFromLeafSource(*block.editLeaf, true);
		}
		break;
	case PreparedBlockKind::Paragraph:
	case PreparedBlockKind::Thinking:
	case PreparedBlockKind::Heading:
	case PreparedBlockKind::CodeBlock:
	case PreparedBlockKind::Rule:
	case PreparedBlockKind::Photo:
	case PreparedBlockKind::Video:
	case PreparedBlockKind::Audio:
	case PreparedBlockKind::Map:
	case PreparedBlockKind::Channel:
	case PreparedBlockKind::GroupedMedia:
	case PreparedBlockKind::RelatedArticle:
	case PreparedBlockKind::EmbedPost:
	case PreparedBlockKind::Placeholder:
		if (ContainsPoint(VisibleTextRectForBlock(block), point)
			&& block.editLeaf) {
			return EditHitFromLeafSource(*block.editLeaf, true);
		}
		break;
	}
	return EditFallbackHitForBlock(block);
}

[[nodiscard]] bool ToggleDetailsBlock(
		std::vector<PreparedBlock> *blocks,
		const QString &anchorId) {
	if (!blocks) {
		return false;
	}
	for (auto &block : *blocks) {
		if (block.kind == PreparedBlockKind::Details
			&& block.anchorId == anchorId) {
			block.collapsed = !block.collapsed;
			return true;
		}
		if (ToggleDetailsBlock(&block.children, anchorId)) {
			return true;
		}
	}
	return false;
}

[[nodiscard]] bool PreparedBlockHasAnchor(
		const PreparedBlock &block,
		const QString &anchorId) {
	return block.anchorId == anchorId
		|| ranges::contains(block.anchorIds, anchorId);
}

[[nodiscard]] MarkdownArticleAnchorExpansion ExpandDetailsToAnchor(
		std::vector<PreparedBlock> *blocks,
		const QString &anchorId) {
	if (!blocks || anchorId.isEmpty()) {
		return {};
	}
	for (auto &block : *blocks) {
		if (PreparedBlockHasAnchor(block, anchorId)) {
			return { true, false };
		}
		auto result = ExpandDetailsToAnchor(&block.children, anchorId);
		if (result.found) {
			if (block.kind == PreparedBlockKind::Details
				&& block.collapsed) {
				block.collapsed = false;
				result.changed = true;
			}
			return result;
		}
	}
	return {};
}

void ClearColorizedFormulaImages(std::vector<LaidOutBlock> *blocks) {
	if (!blocks) {
		return;
	}
	for (auto &block : *blocks) {
		block.colorizedFormulaImage = QImage();
		block.colorizedFormulaColor = QColor();
		block.colorizedFormulaSize = QSize();
		ClearColorizedFormulaImages(&block.children);
	}
}

void CollectCodeBlockHighlightKeys(
		const std::vector<PreparedBlock> &blocks,
		std::unordered_set<
			PendingHighlightKey,
			PendingHighlightKeyHasher> *keys) {
	for (const auto &block : blocks) {
		if (block.kind == PreparedBlockKind::CodeBlock
			&& !block.codeLanguage.isEmpty()) {
			keys->insert({
				.text = CodeBlockDisplayText(block.text.text),
				.language = block.codeLanguage,
			});
		}
		CollectCodeBlockHighlightKeys(block.children, keys);
	}
}

} // namespace

PlaceholderBlockRuntime::PlaceholderBlockRuntime(Fn<void()> repaint)
: clickHandler(std::make_shared<LambdaClickHandler>([] {
}))
, loadingAnimation(
	[repaint = std::move(repaint)] {
		if (repaint) {
			repaint();
		}
	},
	st::defaultInfiniteRadialAnimation) {
}

TaskMarkerRippleRuntime::TaskMarkerRippleRuntime(Fn<void()> repaint)
: repaint(std::move(repaint)) {
}

class MarkdownArticle::Impl final : public CodeBlockSyntaxHighlightTracker {
public:
	Impl(
		const style::Markdown &st,
		std::shared_ptr<MathRenderer> renderer);

	void setRenderer(std::shared_ptr<MathRenderer> renderer);

	void setMediaBlockHost(MediaBlockHost *host);

	void setTextRepaintCallbacks(
		Fn<void()> repaint,
		Fn<void(QRect)> repaintRect);

	void setContent(MarkdownArticleContent content);

	void setTextLeafHeightOverride(int textLeafIndex, int height);

	void clearTextLeafHeightOverride();

	[[nodiscard]] int maxWidth();
	[[nodiscard]] int lastLayoutWidth() const;

	[[nodiscard]] int resizeGetHeight(int width);

	[[nodiscard]] auto countRevealLinesGeometry(int width)
	-> std::vector<MarkdownArticleRevealLine>;

	void setVisibleTopBottom(int visibleTop, int visibleBottom);

	void paint(Painter &p, const MarkdownArticlePaintContext &context);

	[[nodiscard]] MarkdownArticleHitTestResult hitTest(
		QPoint point,
		Ui::Text::StateRequest::Flags flags) const;

	[[nodiscard]] PreparedEditHit editHitTest(QPoint point) const;
	[[nodiscard]] MarkdownArticleEditControlHit editControlHitTest(
		QPoint point) const;

	[[nodiscard]] MarkdownArticleHorizontalScrollHit horizontalScrollHit(
		QPoint point) const;
	[[nodiscard]] bool canConsumeHorizontalScroll(
		QPoint point,
		int delta) const;
	[[nodiscard]] bool consumeHorizontalScroll(QPoint point, int delta);
	[[nodiscard]] bool beginHorizontalScroll(QPoint point, bool fromTouch);
	[[nodiscard]] bool updateHorizontalScroll(QPoint point);
	void endHorizontalScroll();

	[[nodiscard]] int anchorTop(const QString &anchorId) const;

	[[nodiscard]] MarkdownArticleAnchorExpansion expandDetailsToAnchor(
		const QString &anchorId);

	[[nodiscard]] bool toggleDetails(const QString &anchorId);

	[[nodiscard]] bool segmentIsText(int index) const;

	[[nodiscard]] bool segmentIsDisplayMath(int index) const;

	[[nodiscard]] bool segmentIsEditable(int index) const;

	[[nodiscard]] int segmentLength(int index) const;

	[[nodiscard]] int firstTextSegmentIndex() const;

	[[nodiscard]] int firstEditableSegmentIndex() const;

	[[nodiscard]] int textLeafIndexForSegment(int segmentIndex) const;

	[[nodiscard]] int segmentIndexForTextLeafIndex(int textLeafIndex) const;

	[[nodiscard]] int editableIndexForSegment(int segmentIndex) const;

	[[nodiscard]] int segmentIndexForEditableIndex(int editableIndex) const;

	[[nodiscard]] QRect textSegmentRect(int segmentIndex) const;

	[[nodiscard]] QRect segmentRect(int segmentIndex) const;

	[[nodiscard]] MarkdownArticleTextLeafStyle textLeafStyleForSegment(
		int segmentIndex) const;

	[[nodiscard]] MarkdownArticleTextLeafStyle editableStyleForSegment(
		int segmentIndex) const;

	[[nodiscard]] int selectionOffsetFromHit(
		const MarkdownArticleHitTestResult &result,
		TextSelectType selectionType) const;

	[[nodiscard]] TextSelection adjustSelection(
		int segmentIndex,
		TextSelection selection,
		TextSelectType selectionType) const;

	[[nodiscard]] bool selectionContains(
		MarkdownArticleSelection selection,
		const MarkdownArticleSelectionEndpoints *endpoints,
		const MarkdownArticleHitTestResult &result) const;

	[[nodiscard]] TextForMimeData textForContext(
		const MarkdownArticleHitTestResult &result) const;

	[[nodiscard]] TextForMimeData textForSelection(
		MarkdownArticleSelection selection,
		const MarkdownArticleSelectionEndpoints *endpoints) const;

	[[nodiscard]] bool highlightProcessDone(
		Spellchecker::HighlightProcessId processId);

	void invalidatePaletteCache();

	void invalidateRasterCache();

	[[nodiscard]] bool hasHeavyPart() const;

	void unloadHeavyPart();

	[[nodiscard]] MediaBlockHost *mediaBlockHost() const;

	void setPlaceholderLoading(PreparedPlaceholderBlockId id);
	void clearPlaceholderLoading(PreparedPlaceholderBlockId id);
	void clearAllPlaceholderLoading();
	void addTaskMarkerRipple(
		const PreparedEditListItemSource &source,
		QPoint point);
	void addPlaceholderRipple(PreparedPlaceholderBlockId id, QPoint point);
	void stopPlaceholderRipple(PreparedPlaceholderBlockId id);

	void invalidateLayout();

private:
	struct ActiveHorizontalScrollDrag {
		MarkdownArticleScrollOwnerIdentity owner;
		QPoint pressPoint;
		int startScrollLeft = 0;
		int thumbGrabOffset = 0;
		bool fromTouch = false;
	};

	[[nodiscard]] int currentDevicePixelRatio() const;

	void rebuildVisibleSegmentLookup();

	void refreshVisibleSegmentSpan();

	void clearMediaBlocks();

	void refreshMediaBlockHosts();

	void clearPlaceholderRuntimes();

	[[nodiscard]] std::shared_ptr<PlaceholderBlockRuntime>
	getOrCreatePlaceholderRuntime(PreparedPlaceholderBlockId id);

	void prunePlaceholderRuntimes();

	void requestPlaceholderRepaint(PreparedPlaceholderBlockId id);

	[[nodiscard]] auto getOrCreateTaskMarkerRippleRuntime(
		const PreparedEditListItemSource &source)
	-> std::shared_ptr<TaskMarkerRippleRuntime>;

	void requestTaskMarkerRepaint(
		const PreparedEditListItemSource &source);

	void pruneTaskMarkerRuntimes();

	[[nodiscard]] std::shared_ptr<MediaBlock> getOrCreateMediaBlock(
		const PreparedBlock &prepared);

	template <typename Factory>
	[[nodiscard]] std::shared_ptr<MediaBlock> getOrCreateMediaBlock(
		PreparedMediaBlockId id,
		Factory &&factory);

	[[nodiscard]] Spellchecker::HighlightProcessId tryHighlightSyntax(
		const QString &displayText,
		const QString &language,
		TextWithEntities &marked) override;

	[[nodiscard]] SegmentSpan candidateSegmentSpan(QPoint point) const;

	void clearPendingHighlightBlockPointers();

	void prunePendingHighlightProcessesForContent();

	void registerPendingHighlightProcess(
		const PendingHighlightKey &key,
		Spellchecker::HighlightProcessId processId);

	void registerPendingHighlightBlock(LaidOutBlock &block);

	void registerPendingHighlightBlocks(std::vector<LaidOutBlock> &blocks);

	void resetFormulaRasterCache();

	void setPlaceholderLoadingValue(
		PreparedPlaceholderBlockId id,
		bool loading);

	[[nodiscard]] const style::Markdown &layoutStyle() const;
	[[nodiscard]] MarkdownArticleScrollOwnerIdentity scrollOwnerIdentity(
		const LaidOutBlock &block,
		const std::vector<int> &preparedPath) const;
	[[nodiscard]] MarkdownArticleHorizontalScrollLookup
	findHorizontalScrollOwner(QPoint point) const;
	[[nodiscard]] MarkdownArticleHorizontalScrollLookup
	findHorizontalScrollOwner(
		const std::vector<LaidOutBlock> &blocks,
		const std::vector<PreparedBlock> *prepared,
		QPoint point,
		std::vector<int> *preparedPath) const;
	[[nodiscard]] LaidOutBlock *findScrollOwnerByIdentity(
		const MarkdownArticleScrollOwnerIdentity &identity);
	[[nodiscard]] LaidOutBlock *findScrollOwnerByIdentity(
		std::vector<LaidOutBlock> &blocks,
		const std::vector<PreparedBlock> *prepared,
		const MarkdownArticleScrollOwnerIdentity &identity,
		std::vector<int> *preparedPath);
	void captureScrollState();
	void captureScrollState(
		const std::vector<LaidOutBlock> &blocks,
		const std::vector<PreparedBlock> *prepared,
		std::vector<int> *preparedPath);
	void restoreScrollState();
	void restoreScrollState(
		std::vector<LaidOutBlock> &blocks,
		const std::vector<PreparedBlock> *prepared,
		std::vector<int> *preparedPath);
	void refreshScrolledGeometry(LaidOutBlock &block);
	void refreshScrolledGeometry(
		LaidOutBlock &block,
		const ActiveHorizontalScrollOwnerState *activeOwner);
	void refreshScrolledGeometry(std::vector<LaidOutBlock> &blocks);
	void refreshScrolledGeometry(
		std::vector<LaidOutBlock> &blocks,
		const ActiveHorizontalScrollOwnerState *activeOwner);
	void updateScrollbarThumb(LaidOutBlock &block);
	[[nodiscard]] bool setScrollLeft(
		LaidOutBlock &block,
		const MarkdownArticleScrollOwnerIdentity &identity,
		int left);

	void relayout(int width);
	void retainBlocks();

	mutable MarkdownArticleContent _content;
	style::Markdown _style;
	std::vector<RenderedFormula> _formulaRenders;
	std::shared_ptr<MathRenderer> _renderer;
	std::shared_ptr<InlineFormulaObjectCache> _inlineFormulaObjects;
	MediaBlockHost *_mediaBlockHost = nullptr;
	Fn<void()> _textRepaint;
	Fn<void(QRect)> _textRepaintRect;
	int _width = -1;
	int _laidOutWidth = 0;
	int _height = 0;
	std::vector<LaidOutBlock> _blocks;
	std::vector<LaidOutBlock> _retainedBlocks;
	MediaBlockStorage _mediaBlocks;
	std::unordered_map<uint64, std::shared_ptr<PlaceholderBlockRuntime>>
		_placeholderRuntimes;
	TaskMarkerRippleRuntimeMap _taskMarkerRippleRuntimes;
	std::unordered_map<
		uint64,
		RelatedArticleImageState> _relatedArticleImages;
	std::unordered_map<
		PendingHighlightKey,
		Spellchecker::HighlightProcessId,
		PendingHighlightKeyHasher> _pendingHighlightProcesses;
	std::unordered_map<
		Spellchecker::HighlightProcessId,
		PendingHighlightEntry> _pendingHighlightEntries;
	std::vector<std::pair<QString, int>> _anchors;
	std::vector<SelectableSegment> _segments;
	std::optional<LogicalVisibleRange> _visibleRange;
	SegmentSpan _visibleSegmentSpan;
	std::vector<int> _segmentTops;
	std::vector<int> _segmentBottoms;
	std::unordered_map<
		MarkdownArticleScrollOwnerIdentity,
		int,
		MarkdownArticleScrollOwnerIdentityHasher> _capturedScrollLefts;
	std::optional<ActiveHorizontalScrollDrag> _activeHorizontalScrollDrag;
	int _textLeafHeightOverrideIndex = -1;
	int _textLeafHeightOverride = 0;
	bool _blocksPainted = false;

};

MarkdownArticle::Impl::Impl(
	const style::Markdown &st,
	std::shared_ptr<MathRenderer> renderer)
: _style(st)
, _renderer(std::move(renderer))
, _inlineFormulaObjects(CreateInlineFormulaObjectCache(_renderer)) {
	_style.code.font = _style.code.font->monospace();
}

void MarkdownArticle::Impl::setRenderer(std::shared_ptr<MathRenderer> renderer) {
	_renderer = std::move(renderer);
	SetInlineFormulaObjectCacheRenderer(_inlineFormulaObjects, _renderer);
	invalidateRasterCache();
	invalidateLayout();
}

void MarkdownArticle::Impl::setMediaBlockHost(MediaBlockHost *host) {
	if (_mediaBlockHost == host) {
		return;
	}
	_mediaBlockHost = host;
	refreshMediaBlockHosts();
}

void MarkdownArticle::Impl::setTextRepaintCallbacks(
		Fn<void()> repaint,
		Fn<void(QRect)> repaintRect) {
	_textRepaint = std::move(repaint);
	_textRepaintRect = std::move(repaintRect);
}

void MarkdownArticle::Impl::setContent(MarkdownArticleContent content) {
	if (hasHeavyPart()) {
		unloadHeavyPart();
	}
	auto reusedMediaBlocks = MediaBlockStorage();
	const auto reuseMediaBlocks = (_content.mediaRuntime == content.mediaRuntime);
	if (reuseMediaBlocks) {
		auto oldMediaBlocks = MediaBlockStorage();
		oldMediaBlocks.swap(_mediaBlocks);
		reusedMediaBlocks = ReuseMediaBlocks(
			_content.blocks.blocks,
			&oldMediaBlocks,
			content.blocks.blocks);
	} else {
		clearMediaBlocks();
	}
	clearPlaceholderRuntimes();
	_relatedArticleImages.clear();
	_content = std::move(content);
	if (reuseMediaBlocks) {
		_mediaBlocks = std::move(reusedMediaBlocks);
	}
	prunePendingHighlightProcessesForContent();
	ClearInlineFormulaObjectCache(_inlineFormulaObjects);
	resetFormulaRasterCache();
	invalidateLayout();
}

void MarkdownArticle::Impl::setTextLeafHeightOverride(
		int textLeafIndex,
		int height) {
	textLeafIndex = std::max(textLeafIndex, -1);
	height = std::max(height, 0);
	if (_textLeafHeightOverrideIndex == textLeafIndex
		&& _textLeafHeightOverride == height) {
		return;
	}
	_textLeafHeightOverrideIndex = textLeafIndex;
	_textLeafHeightOverride = height;
	invalidateLayout();
}

void MarkdownArticle::Impl::clearTextLeafHeightOverride() {
	setTextLeafHeightOverride(-1, 0);
}

int MarkdownArticle::Impl::maxWidth() {
	const auto &st = layoutStyle();
	return std::max(
		st.pageMaxWidth,
		st.pagePadding.left()
			+ st.pagePadding.right()
			+ 1);
}

int MarkdownArticle::Impl::lastLayoutWidth() const {
	return _laidOutWidth;
}

int MarkdownArticle::Impl::resizeGetHeight(int width) {
	relayout(width);
	return std::max(_height, 1);
}

auto MarkdownArticle::Impl::countRevealLinesGeometry(int width)
-> std::vector<MarkdownArticleRevealLine> {
	relayout(width);
	return CollectRevealLines(_blocks, layoutStyle());
}

void MarkdownArticle::Impl::setVisibleTopBottom(int visibleTop, int visibleBottom) {
	if (visibleBottom <= visibleTop) {
		_visibleRange = std::nullopt;
		_visibleSegmentSpan = {};
		return;
	}
	_visibleRange = LogicalVisibleRange{
		.top = visibleTop,
		.bottom = visibleBottom,
	};
	refreshVisibleSegmentSpan();
}

void MarkdownArticle::Impl::paint(
		Painter &p,
		const MarkdownArticlePaintContext &context) {
	const auto &st = layoutStyle();
	auto local = context;
	local.selectionState.segments = &_segments;
	const auto &paintSt = local.paintMarkdownStyle(st);
	auto textPalette = paintSt.textPalette;
	auto markBg = textPalette.markBg->c;
	markBg.setAlphaF(markBg.alphaF() * std::clamp(
		paintSt.markBgOpacity,
		0.,
		1.));
	const auto ownedMarkBg = style::internal::OwnedColor(markBg);
	textPalette.markBg = ownedMarkBg.color();
	const auto &previousTextPalette = p.textPalette();
	p.setTextPalette(textPalette);
	PaintBlocks(
		p,
		_blocks,
		&_content.formulas,
		&_formulaRenders,
		_renderer.get(),
		currentDevicePixelRatio(),
		std::max(_width, 1),
		st,
		local);
	p.setTextPalette(previousTextPalette);
	_retainedBlocks.clear();
	_blocksPainted = true;
}

MarkdownArticleHitTestResult MarkdownArticle::Impl::hitTest(
		QPoint point,
		Ui::Text::StateRequest::Flags flags) const {
	const auto span = candidateSegmentSpan(point);
	for (auto i = span.from; i != span.till; ++i) {
		const auto &segment = _segments[i];
		if (const auto result = HitCodeBlockHeader(segment, point, flags);
			result.valid()) {
			return result;
		}
	}
	for (auto i = span.from; i != span.till; ++i) {
		const auto &segment = _segments[i];
		if (const auto result = HitTextSegment(segment, point, flags);
			result.valid()) {
			return result;
		}
	}
	for (auto i = span.from; i != span.till; ++i) {
		const auto &segment = _segments[i];
		if (const auto result = HitBlockSegment(segment, point, flags);
			result.valid()) {
			return result;
		}
	}
	if (flags & Ui::Text::StateRequest::Flag::LookupSymbol) {
		return HitSegmentFallback(_segments, span, point);
	}
	return {};
}

PreparedEditHit MarkdownArticle::Impl::editHitTest(QPoint point) const {
	return EditHitForBlocks(_blocks, point);
}

MarkdownArticleEditControlHit MarkdownArticle::Impl::editControlHitTest(
		QPoint point) const {
	return EditControlHitForBlocks(_blocks, point);
}

int MarkdownArticle::Impl::anchorTop(const QString &anchorId) const {
	for (const auto &entry : _anchors) {
		if (entry.first == anchorId) {
			return entry.second;
		}
	}
	return -1;
}

MarkdownArticleAnchorExpansion MarkdownArticle::Impl::expandDetailsToAnchor(
		const QString &anchorId) {
	const auto result = ExpandDetailsToAnchor(
		&_content.blocks.blocks,
		anchorId);
	if (result.changed) {
		invalidateLayout();
	}
	return result;
}

bool MarkdownArticle::Impl::toggleDetails(const QString &anchorId) {
	if (!ToggleDetailsBlock(&_content.blocks.blocks, anchorId)) {
		return false;
	}
	invalidateLayout();
	return true;
}

bool MarkdownArticle::Impl::segmentIsText(int index) const {
	const auto segment = FindSegment(&_segments, index);
	return segment && segment->isTextLeaf();
}

bool MarkdownArticle::Impl::segmentIsDisplayMath(int index) const {
	const auto segment = FindSegment(&_segments, index);
	return segment && IsDisplayMathSegment(*segment);
}

bool MarkdownArticle::Impl::segmentIsEditable(int index) const {
	const auto segment = FindSegment(&_segments, index);
	return segment && IsEditableSegment(*segment);
}

int MarkdownArticle::Impl::segmentLength(int index) const {
	const auto segment = FindSegment(&_segments, index);
	return segment ? SegmentLength(*segment) : 0;
}

int MarkdownArticle::Impl::firstTextSegmentIndex() const {
	for (const auto &segment : _segments) {
		if (segment.isTextLeaf()) {
			return segment.index;
		}
	}
	return -1;
}

int MarkdownArticle::Impl::firstEditableSegmentIndex() const {
	for (const auto &segment : _segments) {
		if (IsEditableSegment(segment)) {
			return segment.index;
		}
	}
	return -1;
}

int MarkdownArticle::Impl::textLeafIndexForSegment(int segmentIndex) const {
	auto textLeafIndex = 0;
	for (const auto &segment : _segments) {
		if (!segment.isTextLeaf()) {
			continue;
		} else if (segment.index == segmentIndex) {
			return textLeafIndex;
		}
		++textLeafIndex;
	}
	return -1;
}

int MarkdownArticle::Impl::segmentIndexForTextLeafIndex(
		int textLeafIndex) const {
	if (textLeafIndex < 0) {
		return -1;
	}
	auto current = 0;
	for (const auto &segment : _segments) {
		if (!segment.isTextLeaf()) {
			continue;
		} else if (current == textLeafIndex) {
			return segment.index;
		}
		++current;
	}
	return -1;
}

int MarkdownArticle::Impl::editableIndexForSegment(int segmentIndex) const {
	auto editableIndex = 0;
	for (const auto &segment : _segments) {
		if (!IsEditableSegment(segment)) {
			continue;
		} else if (segment.index == segmentIndex) {
			return editableIndex;
		}
		++editableIndex;
	}
	return -1;
}

int MarkdownArticle::Impl::segmentIndexForEditableIndex(
		int editableIndex) const {
	if (editableIndex < 0) {
		return -1;
	}
	auto current = 0;
	for (const auto &segment : _segments) {
		if (!IsEditableSegment(segment)) {
			continue;
		} else if (current == editableIndex) {
			return segment.index;
		}
		++current;
	}
	return -1;
}

QRect MarkdownArticle::Impl::textSegmentRect(int segmentIndex) const {
	const auto segment = FindSegment(&_segments, segmentIndex);
	return (segment && segment->isTextLeaf()) ? segment->textRect : QRect();
}

QRect MarkdownArticle::Impl::segmentRect(int segmentIndex) const {
	const auto segment = FindSegment(&_segments, segmentIndex);
	if (!segment) {
		return QRect();
	} else if (segment->isTextLeaf()) {
		return segment->textRect;
	} else if (IsDisplayMathSegment(*segment)) {
		if (!segment->outerRect.isEmpty()) {
			return segment->outerRect;
		}
		return segment->block ? segment->block->formulaRect : QRect();
	}
	return QRect();
}

MarkdownArticleTextLeafStyle MarkdownArticle::Impl::textLeafStyleForSegment(
		int segmentIndex) const {
	const auto segment = FindSegment(&_segments, segmentIndex);
	if (!segment || !segment->isTextLeaf()) {
		return {};
	}
	const auto &st = layoutStyle();
	const auto &textStyle = TextStyleForSegment(*segment, st);
	return {
		.textStyle = &textStyle,
		.textColor = TextColorForSegment(*segment, st),
		.lineHeight = TextLineHeight(textStyle),
		.align = segment->align,
		.italic = segment->block && segment->block->pullquote,
	};
}

MarkdownArticleTextLeafStyle MarkdownArticle::Impl::editableStyleForSegment(
		int segmentIndex) const {
	const auto segment = FindSegment(&_segments, segmentIndex);
	if (!segment) {
		return {};
	} else if (segment->isTextLeaf()) {
		return textLeafStyleForSegment(segmentIndex);
	} else if (!IsDisplayMathSegment(*segment)) {
		return {};
	}
	const auto &st = layoutStyle();
	return {
		.textStyle = &st.displayMath.fallbackStyle,
		.textColor = st.displayMath.fg,
		.lineHeight = TextLineHeight(st.displayMath.fallbackStyle),
		.align = segment->align,
	};
}

int MarkdownArticle::Impl::selectionOffsetFromHit(
		const MarkdownArticleHitTestResult &result,
		TextSelectType selectionType) const {
	const auto segment = FindSegment(&_segments, result.segmentIndex);
	if (!segment) {
		return 0;
	}
	if (result.forcedOffset >= 0) {
		return std::clamp(result.forcedOffset, 0, SegmentLength(*segment));
	}
	auto offset = int(result.state.symbol);
	if (selectionType == TextSelectType::Letters
		&& result.state.afterSymbol) {
		++offset;
	}
	return std::clamp(offset, 0, SegmentLength(*segment));
}

TextSelection MarkdownArticle::Impl::adjustSelection(
		int segmentIndex,
		TextSelection selection,
		TextSelectType selectionType) const {
	const auto segment = FindSegment(&_segments, segmentIndex);
	if (!segment || !segment->isTextLeaf()) {
		return selection;
	}
	return segment->leaf->adjustSelection(selection, selectionType);
}

bool MarkdownArticle::Impl::selectionContains(
		MarkdownArticleSelection selection,
		const MarkdownArticleSelectionEndpoints *endpoints,
		const MarkdownArticleHitTestResult &result) const {
	if (result.codeHeaderCopy) {
		return false;
	}
	const auto segment = FindSegment(&_segments, result.segmentIndex);
	if (!segment || selection.empty() || !result.valid()) {
		return false;
	}
	const auto selectionState = PaintSelectionState{
		.segments = &_segments,
		.selection = selection,
		.endpoints = endpoints,
	};
	if (segment->tableSegmentIndex >= 0
		&& TableSegmentSelected(selectionState, segment->tableSegmentIndex)) {
		return true;
	}
	if (!segment->isTextLeaf()) {
		return WholeSegmentSelected(*segment, selectionState);
	}
	const auto textSelection = TextSelectionForSegment(*segment, selectionState);
	if (!textSelection || textSelection->empty()) {
		return false;
	}
	const auto offset = selectionOffsetFromHit(result, TextSelectType::Letters);
	return (offset >= textSelection->from) && (offset < textSelection->to);
}

TextForMimeData MarkdownArticle::Impl::textForContext(
		const MarkdownArticleHitTestResult &result) const {
	if (!result.valid() || !result.direct) {
		return TextForMimeData();
	}
	const auto segment = FindSegment(&_segments, result.segmentIndex);
	return segment ? TextForSegment(*segment) : TextForMimeData();
}

TextForMimeData MarkdownArticle::Impl::textForSelection(
		MarkdownArticleSelection selection,
		const MarkdownArticleSelectionEndpoints *endpoints) const {
	return TextForSelectedSegments(_segments, selection, endpoints);
}

bool MarkdownArticle::Impl::highlightProcessDone(
		Spellchecker::HighlightProcessId processId) {
	const auto i = _pendingHighlightEntries.find(processId);
	if (i == end(_pendingHighlightEntries)) {
		return false;
	}
	auto entry = std::move(i->second);
	_pendingHighlightEntries.erase(i);
	_pendingHighlightProcesses.erase(entry.key);

	auto rebuilt = false;
	for (const auto block : entry.blocks) {
		RepopulateCodeBlockLeaf(
			*block,
			&_content.formulas,
			_inlineFormulaObjects.get(),
			_content.mediaRuntime,
			layoutStyle(),
			true,
			this);
		registerPendingHighlightBlock(*block);
		rebuilt = true;
	}
	return rebuilt;
}

void MarkdownArticle::Impl::invalidatePaletteCache() {
	InvalidateInlineFormulaPaletteCache(_inlineFormulaObjects);
	ClearColorizedFormulaImages(&_blocks);
}

void MarkdownArticle::Impl::invalidateRasterCache() {
	resetFormulaRasterCache();
	InvalidateInlineFormulaRasterCache(_inlineFormulaObjects);
	ClearColorizedFormulaImages(&_blocks);
}

bool MarkdownArticle::Impl::hasHeavyPart() const {
	for (const auto &entry : _mediaBlocks) {
		const auto &block = entry.second;
		if (block && block->hasHeavyPart()) {
			return true;
		}
	}
	return false;
}

void MarkdownArticle::Impl::unloadHeavyPart() {
	for (const auto &entry : _mediaBlocks) {
		if (const auto &block = entry.second) {
			block->unloadHeavyPart();
		}
	}
}

MediaBlockHost *MarkdownArticle::Impl::mediaBlockHost() const {
	return _mediaBlockHost;
}

void MarkdownArticle::Impl::setPlaceholderLoading(
		PreparedPlaceholderBlockId id) {
	setPlaceholderLoadingValue(id, true);
}

void MarkdownArticle::Impl::clearPlaceholderLoading(
		PreparedPlaceholderBlockId id) {
	setPlaceholderLoadingValue(id, false);
}

void MarkdownArticle::Impl::clearAllPlaceholderLoading() {
	auto repaintIds = std::vector<PreparedPlaceholderBlockId>();
	repaintIds.reserve(_placeholderRuntimes.size());
	for (const auto &[value, runtime] : _placeholderRuntimes) {
		if (!runtime || !runtime->loading) {
			continue;
		}
		runtime->loading = false;
		runtime->loadingAnimation.stop(anim::type::instant);
		repaintIds.push_back({ .value = value });
	}
	for (const auto id : repaintIds) {
		requestPlaceholderRepaint(id);
	}
}

void MarkdownArticle::Impl::addTaskMarkerRipple(
		const PreparedEditListItemSource &source,
		QPoint point) {
	auto block = FindListItemBlock(&_blocks, source);
	if (!block
		|| block->taskState == TaskState::None
		|| block->markerRect.isEmpty()) {
		return;
	}
	auto runtime = block->taskMarkerRippleRuntime
		? block->taskMarkerRippleRuntime
		: getOrCreateTaskMarkerRippleRuntime(source);
	if (!runtime) {
		return;
	}
	block->taskMarkerRippleRuntime = runtime;
	auto view = Ui::CheckView(
		layoutStyle().list.taskCheck,
		block->taskState == TaskState::Checked);
	const auto mask = view.prepareRippleMask();
	const auto size = mask.size();
	if (!runtime->ripple || runtime->rippleSize != size) {
		runtime->ripple = std::make_unique<Ui::RippleAnimation>(
			st::defaultCheckbox.ripple,
			mask,
			[repaint = runtime->repaint] {
				if (repaint) {
					repaint();
				}
			});
		runtime->rippleSize = size;
	}
	point -= (block->markerRect.topLeft()
		+ st::defaultCheckbox.rippleAreaPosition);
	point.setX(std::clamp(point.x(), 0, std::max(size.width() - 1, 0)));
	point.setY(std::clamp(point.y(), 0, std::max(size.height() - 1, 0)));
	runtime->ripple->add(point);
	runtime->ripple->lastStop();
	if (runtime->repaint) {
		runtime->repaint();
	}
}

void MarkdownArticle::Impl::addPlaceholderRipple(
		PreparedPlaceholderBlockId id,
		QPoint point) {
	const auto block = FindPlaceholderBlock(&_blocks, id);
	if (!block) {
		return;
	}
	auto runtime = block->placeholderRuntime
		? block->placeholderRuntime
		: getOrCreatePlaceholderRuntime(id);
	if (!runtime) {
		return;
	}
	block->placeholderRuntime = runtime;
	const auto size = block->mediaRect.size();
	if (!runtime->ripple || runtime->rippleSize != size) {
		runtime->ripple = std::make_unique<Ui::RippleAnimation>(
			st::defaultRippleAnimation,
			Ui::RippleAnimation::RoundRectMask(
				size,
				layoutStyle().placeholder.radius),
			[=] {
				requestPlaceholderRepaint(id);
			});
		runtime->rippleSize = size;
	}
	point.setX(std::clamp(point.x(), 0, std::max(size.width() - 1, 0)));
	point.setY(std::clamp(point.y(), 0, std::max(size.height() - 1, 0)));
	runtime->ripple->add(point);
	requestPlaceholderRepaint(id);
}

void MarkdownArticle::Impl::stopPlaceholderRipple(
		PreparedPlaceholderBlockId id) {
	if (!id) {
		return;
	}
	const auto i = _placeholderRuntimes.find(id.value);
	if (i == end(_placeholderRuntimes)
		|| !i->second
		|| !i->second->ripple) {
		return;
	}
	i->second->ripple->lastStop();
	requestPlaceholderRepaint(id);
}

void MarkdownArticle::Impl::invalidateLayout() {
	_width = -1;
	_laidOutWidth = 0;
	_height = 0;
	captureScrollState();
	clearPendingHighlightBlockPointers();
	retainBlocks();
	_anchors.clear();
	_segments.clear();
	_visibleSegmentSpan = {};
	_segmentTops.clear();
	_segmentBottoms.clear();
}

void MarkdownArticle::Impl::retainBlocks() {
	if (_blocks.empty()) {
		_blocksPainted = false;
		return;
	}
	if (_blocksPainted) {
		_retainedBlocks = std::move(_blocks);
	}
	_blocks.clear();
	_blocksPainted = false;
}

int MarkdownArticle::Impl::currentDevicePixelRatio() const {
	return std::max(style::DevicePixelRatio(), 1);
}

void MarkdownArticle::Impl::rebuildVisibleSegmentLookup() {
	RebuildVisibleSegmentLookup(
		_segments,
		&_segmentTops,
		&_segmentBottoms);
	refreshVisibleSegmentSpan();
}

void MarkdownArticle::Impl::refreshVisibleSegmentSpan() {
	_visibleSegmentSpan = _visibleRange
		? LookupVisibleSegmentSpan(
			_segmentTops,
			_segmentBottoms,
			*_visibleRange)
		: SegmentSpan();
}

void MarkdownArticle::Impl::clearMediaBlocks() {
	ClearMediaBlockStorage(&_mediaBlocks);
}

void MarkdownArticle::Impl::clearPlaceholderRuntimes() {
	_placeholderRuntimes.clear();
}

void MarkdownArticle::Impl::refreshMediaBlockHosts() {
	for (const auto &[id, block] : _mediaBlocks) {
		if (block) {
			block->setLayoutStyle(layoutStyle());
			block->setHost(_mediaBlockHost);
		}
	}
}

auto MarkdownArticle::Impl::getOrCreateTaskMarkerRippleRuntime(
		const PreparedEditListItemSource &source)
-> std::shared_ptr<TaskMarkerRippleRuntime> {
	if (const auto i = _taskMarkerRippleRuntimes.find(source);
		i != end(_taskMarkerRippleRuntimes)) {
		return i->second;
	}
	auto runtime = std::make_shared<TaskMarkerRippleRuntime>([=] {
		requestTaskMarkerRepaint(source);
	});
	_taskMarkerRippleRuntimes.emplace(source, runtime);
	return runtime;
}

std::shared_ptr<PlaceholderBlockRuntime>
MarkdownArticle::Impl::getOrCreatePlaceholderRuntime(
		PreparedPlaceholderBlockId id) {
	if (!id) {
		return nullptr;
	}
	if (const auto i = _placeholderRuntimes.find(id.value);
		i != end(_placeholderRuntimes)) {
		return i->second;
	}
	auto runtime = std::make_shared<PlaceholderBlockRuntime>([=] {
		requestPlaceholderRepaint(id);
	});
	_placeholderRuntimes.emplace(id.value, runtime);
	return runtime;
}

void MarkdownArticle::Impl::pruneTaskMarkerRuntimes() {
	auto live = TaskMarkerSourceSet();
	CollectTaskMarkerSources(_blocks, &live);
	for (auto i = _taskMarkerRippleRuntimes.begin();
		i != _taskMarkerRippleRuntimes.end();) {
		if (live.find(i->first) != end(live)) {
			++i;
		} else {
			i = _taskMarkerRippleRuntimes.erase(i);
		}
	}
}

void MarkdownArticle::Impl::prunePlaceholderRuntimes() {
	auto live = std::unordered_set<uint64>();
	CollectPlaceholderIds(_blocks, &live);
	for (auto i = _placeholderRuntimes.begin(); i != _placeholderRuntimes.end();) {
		if (live.find(i->first) != end(live)) {
			++i;
		} else {
			i = _placeholderRuntimes.erase(i);
		}
	}
}

void MarkdownArticle::Impl::requestTaskMarkerRepaint(
		const PreparedEditListItemSource &source) {
	if (const auto block = FindListItemBlock(_blocks, source)) {
		const auto rect = TaskMarkerRippleRect(*block, layoutStyle());
		if (_textRepaintRect && !rect.isEmpty()) {
			_textRepaintRect(rect);
		} else if (_textRepaint) {
			_textRepaint();
		}
	} else if (_textRepaint) {
		_textRepaint();
	}
}

void MarkdownArticle::Impl::requestPlaceholderRepaint(
		PreparedPlaceholderBlockId id) {
	if (const auto block = FindPlaceholderBlock(_blocks, id)) {
		if (_textRepaintRect) {
			_textRepaintRect(block->mediaRect);
		} else if (_textRepaint) {
			_textRepaint();
		}
	} else if (_textRepaint) {
		_textRepaint();
	}
}

std::shared_ptr<MediaBlock> MarkdownArticle::Impl::getOrCreateMediaBlock(
		const PreparedBlock &prepared) {
	switch (prepared.kind) {
	case PreparedBlockKind::Photo:
		return getOrCreateMediaBlock(
			prepared.photo.id,
			[=] {
				return CreatePhotoMediaBlock(
					prepared.photo,
					_content.mediaRuntime,
					layoutStyle());
			});
	case PreparedBlockKind::Video:
		return getOrCreateMediaBlock(
			prepared.video.id,
			[=] {
				return CreateVideoMediaBlock(
					prepared.video,
					_content.mediaRuntime,
					layoutStyle());
			});
	case PreparedBlockKind::Map:
		return getOrCreateMediaBlock(
			prepared.map.id,
			[=] {
				return CreateMapMediaBlock(
					prepared.map,
					_content.mediaRuntime,
					layoutStyle());
			});
	case PreparedBlockKind::Audio:
		return getOrCreateMediaBlock(
			prepared.audio.id,
			[=] {
				return CreateAudioMediaBlock(
					prepared.audio,
					_content.mediaRuntime,
					layoutStyle());
			});
	case PreparedBlockKind::Channel:
		return getOrCreateMediaBlock(
			prepared.channel.id,
			[=] {
				return CreateChannelMediaBlock(
					prepared.channel,
					_content.mediaRuntime,
					layoutStyle());
			});
	case PreparedBlockKind::GroupedMedia:
		return getOrCreateMediaBlock(
			prepared.groupedMedia.id,
			[=] {
				return CreateGroupedMediaBlock(
					prepared.groupedMedia,
					_content.mediaRuntime,
					layoutStyle());
			});
	default:
		return nullptr;
	}
}

template <typename Factory>
std::shared_ptr<MediaBlock> MarkdownArticle::Impl::getOrCreateMediaBlock(
		PreparedMediaBlockId id,
		Factory &&factory) {
	if (!id) {
		return nullptr;
	}
	if (const auto i = _mediaBlocks.find(id.value);
		i != end(_mediaBlocks)) {
		if (i->second) {
			i->second->setLayoutStyle(layoutStyle());
			i->second->setHost(_mediaBlockHost);
		}
		return i->second;
	}
	auto block = factory();
	if (block) {
		block->setLayoutStyle(layoutStyle());
		block->setHost(_mediaBlockHost);
	}
	_mediaBlocks.emplace(id.value, block);
	return block;
}

Spellchecker::HighlightProcessId MarkdownArticle::Impl::tryHighlightSyntax(
		const QString &displayText,
		const QString &language,
		TextWithEntities &marked) {
	const auto key = PendingHighlightKey{
		.text = displayText,
		.language = language,
	};
	if (const auto i = _pendingHighlightProcesses.find(key);
		i != end(_pendingHighlightProcesses)) {
		return i->second;
	}
	const auto processId = Spellchecker::TryHighlightSyntax(marked);
	if (processId) {
		registerPendingHighlightProcess(key, processId);
	}
	return processId;
}

SegmentSpan MarkdownArticle::Impl::candidateSegmentSpan(QPoint point) const {
	if (_visibleRange
		&& (_visibleRange->top <= point.y())
		&& (point.y() < _visibleRange->bottom)) {
		return _visibleSegmentSpan.empty()
			? FullSegmentSpan(_segments)
			: _visibleSegmentSpan;
	}
	return FullSegmentSpan(_segments);
}

void MarkdownArticle::Impl::clearPendingHighlightBlockPointers() {
	for (auto &entry : _pendingHighlightEntries) {
		entry.second.blocks.clear();
	}
}

void MarkdownArticle::Impl::prunePendingHighlightProcessesForContent() {
	if (_pendingHighlightProcesses.empty()) {
		return;
	}
	auto live = std::unordered_set<
		PendingHighlightKey,
		PendingHighlightKeyHasher>();
	CollectCodeBlockHighlightKeys(_content.blocks.blocks, &live);
	for (auto i = _pendingHighlightProcesses.begin();
			i != end(_pendingHighlightProcesses);) {
		if (live.contains(i->first)) {
			++i;
			continue;
		}
		_pendingHighlightEntries.erase(i->second);
		i = _pendingHighlightProcesses.erase(i);
	}
}

void MarkdownArticle::Impl::registerPendingHighlightProcess(
		const PendingHighlightKey &key,
		Spellchecker::HighlightProcessId processId) {
	_pendingHighlightProcesses[key] = processId;
	auto &entry = _pendingHighlightEntries[processId];
	entry.key = key;
}

void MarkdownArticle::Impl::registerPendingHighlightBlock(LaidOutBlock &block) {
	if (!block.syntaxHighlightProcessId) {
		return;
	}
	if (!_pendingHighlightEntries.contains(block.syntaxHighlightProcessId)) {
		registerPendingHighlightProcess(
			PendingHighlightKeyForBlock(block),
			block.syntaxHighlightProcessId);
	}
	_pendingHighlightEntries[block.syntaxHighlightProcessId].blocks.push_back(
		&block);
}

void MarkdownArticle::Impl::registerPendingHighlightBlocks(std::vector<LaidOutBlock> &blocks) {
	for (auto &block : blocks) {
		registerPendingHighlightBlock(block);
		registerPendingHighlightBlocks(block.children);
	}
}

void MarkdownArticle::Impl::resetFormulaRasterCache() {
	_formulaRenders.clear();
	_formulaRenders.resize(_content.formulas.size());
}

void MarkdownArticle::Impl::setPlaceholderLoadingValue(
		PreparedPlaceholderBlockId id,
		bool loading) {
	if (!id) {
		return;
	}
	const auto runtime = loading
		? getOrCreatePlaceholderRuntime(id)
		: [&]() -> std::shared_ptr<PlaceholderBlockRuntime> {
			if (const auto i = _placeholderRuntimes.find(id.value);
				i != end(_placeholderRuntimes)) {
				return i->second;
			}
			return nullptr;
		}();
	if (!runtime || runtime->loading == loading) {
		return;
	}
	runtime->loading = loading;
	if (loading) {
		runtime->loadingAnimation.start();
	} else {
		runtime->loadingAnimation.stop(anim::type::instant);
	}
	requestPlaceholderRepaint(id);
}

const style::Markdown &MarkdownArticle::Impl::layoutStyle() const {
	return _style;
}

MarkdownArticleScrollOwnerIdentity MarkdownArticle::Impl::scrollOwnerIdentity(
		const LaidOutBlock &block,
		const std::vector<int> &preparedPath) const {
	if (block.editBlock && ValidBlockPath(block.editBlock->path)) {
		return { .blockPath = block.editBlock->path };
	}
	return { .preparedPath = preparedPath };
}

MarkdownArticleHorizontalScrollLookup
MarkdownArticle::Impl::findHorizontalScrollOwner(QPoint point) const {
	auto preparedPath = std::vector<int>();
	return findHorizontalScrollOwner(
		_blocks,
		&_content.blocks.blocks,
		point,
		&preparedPath);
}

MarkdownArticleHorizontalScrollLookup
MarkdownArticle::Impl::findHorizontalScrollOwner(
		const std::vector<LaidOutBlock> &blocks,
		const std::vector<PreparedBlock> *prepared,
		QPoint point,
		std::vector<int> *preparedPath) const {
	for (auto i = 0, count = int(blocks.size()); i != count; ++i) {
		const auto &block = blocks[i];
		preparedPath->push_back(i);
		const auto preparedBlock = (prepared && (i < prepared->size()))
			? &(*prepared)[i]
			: nullptr;
		if (const auto result = findHorizontalScrollOwner(
				block.children,
				preparedBlock ? &preparedBlock->children : nullptr,
				point,
				preparedPath);
			result.block) {
			return result;
		}
		if (block.horizontalScrollMax > 0
			&& !block.scrollViewportRect.isEmpty()) {
			const auto identity = scrollOwnerIdentity(block, *preparedPath);
			auto hit = MarkdownArticleHorizontalScrollHit{
				.scrollable = true,
				.overViewport = ContainsPoint(block.scrollViewportRect, point),
				.overScrollbar = ContainsPoint(
					block.scrollScrollbarTrackRect,
					point),
				.overScrollbarThumb = ContainsPoint(
					block.scrollScrollbarThumbRect,
					point),
			};
			if (hit.overViewport || hit.overScrollbar) {
				return {
					.hit = hit,
					.identity = identity,
					.block = &block,
				};
			}
		}
		preparedPath->pop_back();
	}
	return {};
}

LaidOutBlock *MarkdownArticle::Impl::findScrollOwnerByIdentity(
		const MarkdownArticleScrollOwnerIdentity &identity) {
	auto preparedPath = std::vector<int>();
	return findScrollOwnerByIdentity(
		_blocks,
		&_content.blocks.blocks,
		identity,
		&preparedPath);
}

LaidOutBlock *MarkdownArticle::Impl::findScrollOwnerByIdentity(
		std::vector<LaidOutBlock> &blocks,
		const std::vector<PreparedBlock> *prepared,
		const MarkdownArticleScrollOwnerIdentity &identity,
		std::vector<int> *preparedPath) {
	for (auto i = 0, count = int(blocks.size()); i != count; ++i) {
		auto &block = blocks[i];
		preparedPath->push_back(i);
		const auto preparedBlock = (prepared && (i < prepared->size()))
			? &(*prepared)[i]
			: nullptr;
		if (!block.scrollViewportRect.isEmpty()) {
			const auto current = scrollOwnerIdentity(block, *preparedPath);
			if (current == identity) {
				return &block;
			}
		}
		if (const auto child = findScrollOwnerByIdentity(
				block.children,
				preparedBlock ? &preparedBlock->children : nullptr,
				identity,
				preparedPath)) {
			return child;
		}
		preparedPath->pop_back();
	}
	return nullptr;
}

void MarkdownArticle::Impl::captureScrollState() {
	auto preparedPath = std::vector<int>();
	captureScrollState(
		_blocks,
		&_content.blocks.blocks,
		&preparedPath);
}

void MarkdownArticle::Impl::captureScrollState(
		const std::vector<LaidOutBlock> &blocks,
		const std::vector<PreparedBlock> *prepared,
		std::vector<int> *preparedPath) {
	for (auto i = 0, count = int(blocks.size()); i != count; ++i) {
		const auto &block = blocks[i];
		preparedPath->push_back(i);
		const auto preparedBlock = (prepared && (i < prepared->size()))
			? &(*prepared)[i]
			: nullptr;
		if (!block.scrollViewportRect.isEmpty()) {
			const auto identity = scrollOwnerIdentity(block, *preparedPath);
			if (block.horizontalScrollLeft > 0) {
				_capturedScrollLefts[identity] = block.horizontalScrollLeft;
			} else {
				_capturedScrollLefts.erase(identity);
			}
		}
		captureScrollState(
			block.children,
			preparedBlock ? &preparedBlock->children : nullptr,
			preparedPath);
		preparedPath->pop_back();
	}
}

void MarkdownArticle::Impl::restoreScrollState() {
	auto preparedPath = std::vector<int>();
	restoreScrollState(
		_blocks,
		&_content.blocks.blocks,
		&preparedPath);
}

void MarkdownArticle::Impl::restoreScrollState(
		std::vector<LaidOutBlock> &blocks,
		const std::vector<PreparedBlock> *prepared,
		std::vector<int> *preparedPath) {
	for (auto i = 0, count = int(blocks.size()); i != count; ++i) {
		auto &block = blocks[i];
		preparedPath->push_back(i);
		const auto preparedBlock = (prepared && (i < prepared->size()))
			? &(*prepared)[i]
			: nullptr;
		if (!block.scrollViewportRect.isEmpty()) {
			const auto identity = scrollOwnerIdentity(block, *preparedPath);
			const auto j = _capturedScrollLefts.find(identity);
			block.horizontalScrollLeft = (j != end(_capturedScrollLefts))
				? std::clamp(j->second, 0, block.horizontalScrollMax)
				: 0;
		}
		restoreScrollState(
			block.children,
			preparedBlock ? &preparedBlock->children : nullptr,
			preparedPath);
		preparedPath->pop_back();
	}
}

void MarkdownArticle::Impl::refreshScrolledGeometry(
		LaidOutBlock &block,
		const ActiveHorizontalScrollOwnerState *activeOwner) {
	RestoreLogicalBlockGeometry(&block);
	if (activeOwner) {
		ApplyTranslatedDescendantGeometry(&block, *activeOwner);
	}

	std::optional<ActiveHorizontalScrollOwnerState> nextOwner;
	if (!activeOwner && !block.scrollViewportRect.isEmpty()) {
		block.horizontalScrollLeft = std::clamp(
			block.horizontalScrollLeft,
			0,
			block.horizontalScrollMax);
		if (block.horizontalScrollMax > 0) {
			const auto owner = ActiveHorizontalScrollOwnerState{
				.viewport = block.scrollViewportRect,
				.shift = -block.horizontalScrollLeft,
			};
			if (ScrollOwnerMovesOwnContent(block.kind)) {
				ApplyOwnerContentGeometry(&block, owner);
			}
			if (ScrollOwnerMovesChildren(block.kind)) {
				nextOwner = owner;
			}
		}
		updateScrollbarThumb(block);
	}
	refreshScrolledGeometry(
		block.children,
		nextOwner ? &*nextOwner : activeOwner);
}

void MarkdownArticle::Impl::refreshScrolledGeometry(LaidOutBlock &block) {
	refreshScrolledGeometry(block, nullptr);
}

void MarkdownArticle::Impl::refreshScrolledGeometry(
		std::vector<LaidOutBlock> &blocks) {
	refreshScrolledGeometry(blocks, nullptr);
}

void MarkdownArticle::Impl::refreshScrolledGeometry(
		std::vector<LaidOutBlock> &blocks,
		const ActiveHorizontalScrollOwnerState *activeOwner) {
	for (auto &block : blocks) {
		refreshScrolledGeometry(block, activeOwner);
	}
}

void MarkdownArticle::Impl::updateScrollbarThumb(LaidOutBlock &block) {
	if (block.horizontalScrollMax <= 0
		|| block.scrollScrollbarTrackRect.isEmpty()) {
		block.scrollScrollbarThumbRect = QRect();
		block.tableScrollbarThumbRect = QRect();
		return;
	}
	const auto trackWidth = block.scrollScrollbarTrackRect.width();
	if (trackWidth <= 0) {
		block.scrollScrollbarThumbRect = QRect();
		block.tableScrollbarThumbRect = QRect();
		return;
	}
	const auto viewportWidth = std::max(block.scrollViewportRect.width(), 1);
	const auto contentWidth = std::max(block.scrollLogicalContentRect.width(), 1);
	auto thumbWidth = (trackWidth * viewportWidth + (contentWidth / 2))
		/ contentWidth;
	thumbWidth = std::clamp(
		thumbWidth,
		std::min(layoutStyle().table.scrollbarMinThumbWidth, trackWidth),
		trackWidth);
	const auto available = std::max(trackWidth - thumbWidth, 0);
	const auto thumbOffset = (available > 0)
		? ((block.horizontalScrollLeft * available)
			+ (block.horizontalScrollMax / 2))
			/ block.horizontalScrollMax
		: 0;
	block.scrollScrollbarThumbRect = QRect(
		block.scrollScrollbarTrackRect.x() + thumbOffset,
		block.scrollScrollbarTrackRect.y(),
		thumbWidth,
		block.scrollScrollbarTrackRect.height());
	if (block.kind == PreparedBlockKind::Table) {
		block.tableScrollbarThumbRect = block.scrollScrollbarThumbRect;
	}
}

bool MarkdownArticle::Impl::setScrollLeft(
		LaidOutBlock &block,
		const MarkdownArticleScrollOwnerIdentity &identity,
		int left) {
	left = std::clamp(left, 0, block.horizontalScrollMax);
	if (block.horizontalScrollLeft == left) {
		return false;
	}
	block.horizontalScrollLeft = left;
	if (left > 0) {
		_capturedScrollLefts[identity] = left;
	} else {
		_capturedScrollLefts.erase(identity);
	}
	refreshScrolledGeometry(block);
	RefreshScrollableSegmentRects(_blocks, &_segments);
	if (_textRepaintRect) {
		_textRepaintRect(block.outer);
	} else if (_textRepaint) {
		_textRepaint();
	}
	return true;
}

MarkdownArticleHorizontalScrollHit MarkdownArticle::Impl::horizontalScrollHit(
		QPoint point) const {
	return findHorizontalScrollOwner(point).hit;
}

bool MarkdownArticle::Impl::canConsumeHorizontalScroll(
		QPoint point,
		int delta) const {
	if (const auto lookup = findHorizontalScrollOwner(point);
		lookup.block) {
		const auto left = std::clamp(
			lookup.block->horizontalScrollLeft - delta,
			0,
			lookup.block->horizontalScrollMax);
		return (left != lookup.block->horizontalScrollLeft);
	}
	return false;
}

bool MarkdownArticle::Impl::consumeHorizontalScroll(QPoint point, int delta) {
	if (const auto lookup = findHorizontalScrollOwner(point);
		lookup.block) {
		if (const auto block = findScrollOwnerByIdentity(lookup.identity)) {
			return setScrollLeft(
				*block,
				lookup.identity,
				block->horizontalScrollLeft - delta);
		}
	}
	return false;
}

bool MarkdownArticle::Impl::beginHorizontalScroll(
		QPoint point,
		bool fromTouch) {
	const auto lookup = findHorizontalScrollOwner(point);
	if (!lookup.block) {
		return false;
	}
	if (fromTouch) {
		if (!lookup.hit.overViewport) {
			return false;
		}
		_activeHorizontalScrollDrag = ActiveHorizontalScrollDrag{
			.owner = lookup.identity,
			.pressPoint = point,
			.startScrollLeft = lookup.block->horizontalScrollLeft,
			.fromTouch = true,
		};
		return true;
	}
	if (!lookup.hit.overScrollbar) {
		return false;
	}
	const auto &thumb = lookup.block->scrollScrollbarThumbRect;
	_activeHorizontalScrollDrag = ActiveHorizontalScrollDrag{
		.owner = lookup.identity,
		.pressPoint = point,
		.startScrollLeft = lookup.block->horizontalScrollLeft,
		.thumbGrabOffset = lookup.hit.overScrollbarThumb
			? (point.x() - thumb.x())
			: (thumb.width() / 2),
	};
	if (!lookup.hit.overScrollbarThumb) {
		(void)updateHorizontalScroll(point);
	}
	return true;
}

bool MarkdownArticle::Impl::updateHorizontalScroll(QPoint point) {
	if (!_activeHorizontalScrollDrag) {
		return false;
	}
	const auto drag = *_activeHorizontalScrollDrag;
	const auto block = findScrollOwnerByIdentity(drag.owner);
	if (!block) {
		return false;
	}
	if (drag.fromTouch) {
		return setScrollLeft(
			*block,
			drag.owner,
			drag.startScrollLeft - (point.x() - drag.pressPoint.x()));
	}
	if (block->scrollScrollbarTrackRect.isEmpty()) {
		return false;
	}
	const auto available = std::max(
		block->scrollScrollbarTrackRect.width()
			- block->scrollScrollbarThumbRect.width(),
		0);
	auto thumbLeft = point.x() - drag.thumbGrabOffset;
	thumbLeft = std::clamp(
		thumbLeft,
		block->scrollScrollbarTrackRect.x(),
		block->scrollScrollbarTrackRect.x() + available);
	const auto left = (available > 0)
		? (((thumbLeft - block->scrollScrollbarTrackRect.x())
			* block->horizontalScrollMax)
			+ (available / 2))
		/ available
		: 0;
	return setScrollLeft(*block, drag.owner, left);
}

void MarkdownArticle::Impl::endHorizontalScroll() {
	_activeHorizontalScrollDrag.reset();
}

void MarkdownArticle::Impl::relayout(int width) {
	width = std::max(width, 1);
	if (_width == width) {
		return;
	}
	_width = width;
	StoreRelatedArticleImageStates(
		_blocks,
		&_relatedArticleImages);
	clearPendingHighlightBlockPointers();
	retainBlocks();
	_anchors.clear();
	_segments.clear();
	_visibleSegmentSpan = {};
	_segmentTops.clear();
	_segmentBottoms.clear();

	const auto &st = layoutStyle();
	const auto &page = st.pagePadding;
	const auto innerWidth = std::max(width - page.left() - page.right(), 1);
	auto repaintScope = InlineIvImageRepaintScope(
		_textRepaint,
		_textRepaintRect);
	auto context = LayoutContext{
		.articleLeft = page.left(),
		.articleWidth = innerWidth,
		.useArticleBands = true,
		.editMode = _content.editMode,
		.syntaxHighlightTracker = this,
	};
	if (_textLeafHeightOverrideIndex >= 0 && _textLeafHeightOverride > 0) {
		context.textLeafHeightOverride
			= std::make_shared<TextLeafHeightOverride>(
				TextLeafHeightOverride{
					.textLeafIndex = _textLeafHeightOverrideIndex,
					.height = _textLeafHeightOverride,
				});
	}
	context.mediaBlockFactory = [=](const PreparedBlock &prepared) {
		return getOrCreateMediaBlock(prepared);
	};
	context.placeholderRuntimeFactory = [=](PreparedPlaceholderBlockId id) {
		return getOrCreatePlaceholderRuntime(id);
	};
	context.taskMarkerRippleRuntimeFactory
		= [=](const PreparedEditListItemSource &source) {
			return getOrCreateTaskMarkerRippleRuntime(source);
		};
	const auto y = LayoutBlocks(
		_content.blocks.blocks,
		&_content.formulas,
		&_formulaRenders,
		_renderer.get(),
		_inlineFormulaObjects.get(),
		_content.mediaRuntime,
		&_blocks,
		st,
		page.left(),
		page.top(),
		innerWidth,
		context);
	restoreScrollState();
	refreshScrolledGeometry(_blocks);
	_laidOutWidth = std::min(
		width,
		std::max(
			BlockMaxRight(_blocks) + page.right(),
			page.left() + page.right() + 1));
	pruneTaskMarkerRuntimes();
	prunePlaceholderRuntimes();
	RestoreRelatedArticleImageStates(
		&_blocks,
		_relatedArticleImages);
	_height = y + page.bottom();
	registerPendingHighlightBlocks(_blocks);
	CollectAnchors(_blocks, &_anchors);
	CollectSelectableSegments(&_blocks, &_segments);
	RefreshScrollableSegmentRects(_blocks, &_segments);
	rebuildVisibleSegmentLookup();
}

MarkdownArticle::MarkdownArticle(
	const style::Markdown &st,
	std::shared_ptr<MathRenderer> renderer)
: _impl(std::make_unique<Impl>(st, std::move(renderer))) {
}

MarkdownArticle::~MarkdownArticle() = default;
MarkdownArticle::MarkdownArticle(MarkdownArticle &&) noexcept = default;
MarkdownArticle &MarkdownArticle::operator=(MarkdownArticle &&) noexcept = default;

void MarkdownArticle::setRenderer(std::shared_ptr<MathRenderer> renderer) {
	_impl->setRenderer(std::move(renderer));
}

void MarkdownArticle::setMediaBlockHost(MediaBlockHost *host) {
	_impl->setMediaBlockHost(host);
}

void MarkdownArticle::setTextRepaintCallbacks(
		Fn<void()> repaint,
		Fn<void(QRect)> repaintRect) {
	_impl->setTextRepaintCallbacks(
		std::move(repaint),
		std::move(repaintRect));
}

void MarkdownArticle::setContent(MarkdownArticleContent content) {
	_impl->setContent(std::move(content));
}

void MarkdownArticle::setTextLeafHeightOverride(
		int textLeafIndex,
		int height) {
	_impl->setTextLeafHeightOverride(textLeafIndex, height);
}

void MarkdownArticle::clearTextLeafHeightOverride() {
	_impl->clearTextLeafHeightOverride();
}

void MarkdownArticle::invalidateLayout() {
	_impl->invalidateLayout();
}

int MarkdownArticle::maxWidth() const {
	return const_cast<Impl*>(_impl.get())->maxWidth();
}

int MarkdownArticle::lastLayoutWidth() const {
	return _impl->lastLayoutWidth();
}

int MarkdownArticle::resizeGetHeight(int width) {
	return _impl->resizeGetHeight(width);
}

auto MarkdownArticle::countRevealLinesGeometry(int width)
-> std::vector<MarkdownArticleRevealLine> {
	return _impl->countRevealLinesGeometry(width);
}

void MarkdownArticle::setVisibleTopBottom(int visibleTop, int visibleBottom) {
	_impl->setVisibleTopBottom(visibleTop, visibleBottom);
}

void MarkdownArticle::paint(
		Painter &p,
		const MarkdownArticlePaintContext &context) const {
	_impl->paint(p, context);
}

MarkdownArticleHitTestResult MarkdownArticle::hitTest(
		QPoint point,
		Ui::Text::StateRequest::Flags flags) const {
	return _impl->hitTest(point, flags);
}

PreparedEditHit MarkdownArticle::editHitTest(QPoint point) const {
	return _impl->editHitTest(point);
}

MarkdownArticleEditControlHit MarkdownArticle::editControlHitTest(
		QPoint point) const {
	return _impl->editControlHitTest(point);
}

void MarkdownArticle::addTaskMarkerRipple(
		const PreparedEditListItemSource &source,
		QPoint point) {
	_impl->addTaskMarkerRipple(source, point);
}

MarkdownArticleHorizontalScrollHit MarkdownArticle::horizontalScrollHit(
		QPoint point) const {
	return _impl->horizontalScrollHit(point);
}

bool MarkdownArticle::canConsumeHorizontalScroll(
		QPoint point,
		int delta) const {
	return _impl->canConsumeHorizontalScroll(point, delta);
}

bool MarkdownArticle::consumeHorizontalScroll(QPoint point, int delta) {
	return _impl->consumeHorizontalScroll(point, delta);
}

bool MarkdownArticle::beginHorizontalScroll(QPoint point, bool fromTouch) {
	return _impl->beginHorizontalScroll(point, fromTouch);
}

bool MarkdownArticle::updateHorizontalScroll(QPoint point) {
	return _impl->updateHorizontalScroll(point);
}

void MarkdownArticle::endHorizontalScroll() {
	_impl->endHorizontalScroll();
}

int MarkdownArticle::anchorTop(const QString &anchorId) const {
	return _impl->anchorTop(anchorId);
}

MarkdownArticleAnchorExpansion MarkdownArticle::expandDetailsToAnchor(
		const QString &anchorId) {
	return _impl->expandDetailsToAnchor(anchorId);
}

bool MarkdownArticle::toggleDetails(const QString &anchorId) {
	return _impl->toggleDetails(anchorId);
}

bool MarkdownArticle::segmentIsText(int index) const {
	return _impl->segmentIsText(index);
}

bool MarkdownArticle::segmentIsDisplayMath(int index) const {
	return _impl->segmentIsDisplayMath(index);
}

bool MarkdownArticle::segmentIsEditable(int index) const {
	return _impl->segmentIsEditable(index);
}

int MarkdownArticle::segmentLength(int index) const {
	return _impl->segmentLength(index);
}

int MarkdownArticle::firstTextSegmentIndex() const {
	return _impl->firstTextSegmentIndex();
}

int MarkdownArticle::firstEditableSegmentIndex() const {
	return _impl->firstEditableSegmentIndex();
}

int MarkdownArticle::textLeafIndexForSegment(int segmentIndex) const {
	return _impl->textLeafIndexForSegment(segmentIndex);
}

int MarkdownArticle::segmentIndexForTextLeafIndex(int textLeafIndex) const {
	return _impl->segmentIndexForTextLeafIndex(textLeafIndex);
}

int MarkdownArticle::editableIndexForSegment(int segmentIndex) const {
	return _impl->editableIndexForSegment(segmentIndex);
}

int MarkdownArticle::segmentIndexForEditableIndex(int editableIndex) const {
	return _impl->segmentIndexForEditableIndex(editableIndex);
}

QRect MarkdownArticle::textSegmentRect(int segmentIndex) const {
	return _impl->textSegmentRect(segmentIndex);
}

QRect MarkdownArticle::segmentRect(int segmentIndex) const {
	return _impl->segmentRect(segmentIndex);
}

MarkdownArticleTextLeafStyle MarkdownArticle::textLeafStyleForSegment(
		int segmentIndex) const {
	return _impl->textLeafStyleForSegment(segmentIndex);
}

MarkdownArticleTextLeafStyle MarkdownArticle::editableStyleForSegment(
		int segmentIndex) const {
	return _impl->editableStyleForSegment(segmentIndex);
}

int MarkdownArticle::selectionOffsetFromHit(
		const MarkdownArticleHitTestResult &result,
		TextSelectType selectionType) const {
	return _impl->selectionOffsetFromHit(result, selectionType);
}

TextSelection MarkdownArticle::adjustSelection(
		int segmentIndex,
		TextSelection selection,
		TextSelectType selectionType) const {
	return _impl->adjustSelection(segmentIndex, selection, selectionType);
}

bool MarkdownArticle::selectionContains(
		MarkdownArticleSelection selection,
		const MarkdownArticleSelectionEndpoints *endpoints,
		const MarkdownArticleHitTestResult &result) const {
	return _impl->selectionContains(selection, endpoints, result);
}

TextForMimeData MarkdownArticle::textForContext(
		const MarkdownArticleHitTestResult &result) const {
	return _impl->textForContext(result);
}

TextForMimeData MarkdownArticle::textForSelection(
		MarkdownArticleSelection selection,
		const MarkdownArticleSelectionEndpoints *endpoints) const {
	return _impl->textForSelection(selection, endpoints);
}

bool MarkdownArticle::highlightProcessDone(
		Spellchecker::HighlightProcessId processId) {
	return _impl->highlightProcessDone(processId);
}

void MarkdownArticle::invalidatePaletteCache() {
	_impl->invalidatePaletteCache();
}

void MarkdownArticle::invalidateRasterCache() {
	_impl->invalidateRasterCache();
}

bool MarkdownArticle::hasHeavyPart() const {
	return _impl->hasHeavyPart();
}

void MarkdownArticle::unloadHeavyPart() {
	_impl->unloadHeavyPart();
}

MediaBlockHost *MarkdownArticle::mediaBlockHost() const {
	return _impl->mediaBlockHost();
}

void MarkdownArticle::setPlaceholderLoading(PreparedPlaceholderBlockId id) {
	_impl->setPlaceholderLoading(id);
}

void MarkdownArticle::clearPlaceholderLoading(PreparedPlaceholderBlockId id) {
	_impl->clearPlaceholderLoading(id);
}

void MarkdownArticle::clearAllPlaceholderLoading() {
	_impl->clearAllPlaceholderLoading();
}

void MarkdownArticle::addPlaceholderRipple(
		PreparedPlaceholderBlockId id,
		QPoint point) {
	_impl->addPlaceholderRipple(id, point);
}

void MarkdownArticle::stopPlaceholderRipple(PreparedPlaceholderBlockId id) {
	_impl->stopPlaceholderRipple(id);
}

} // namespace Iv::Markdown