// RDEPUBReaderController+DataSource.swift
// EPUB 阅读器数据源与代理实现
// 实现 RDReaderDataSource 和 RDReaderDelegate 协议，为阅读器视图提供页面数量、
// 页面内容视图、页码变化通知、屏幕方向变化处理等核心数据与事件支持。

import UIKit

/// RDEPUBReaderController 数据源与代理扩展
///
/// 本文件实现 RDReaderDataSource 和 RDReaderDelegate 协议，为阅读器视图提供页面数量、
/// 页面内容视图、页码变化通知、屏幕方向变化处理等核心数据与事件支持。

// MARK: - RDReaderView 数据源与代理

extension RDEPUBReaderController: RDReaderDataSource, RDReaderDelegate {
    /// 返回阅读器总页数
    public func pageCountOfReaderView(readerView: RDReaderView) -> Int {
        readerContext.bookPageMap?.totalPages ?? textBook?.pages.count ?? activePages.count
    }

    /// 为指定页码创建或复用内容视图（优先文本渲染，回退 Web 渲染）
    public func pageContentView(readerView: RDReaderView, pageNum: Int, containerView: UIView?) -> UIView {
        if readerContext.bookPageMap != nil {
            _ = runtime.prepareOnDemandChapter(forAbsolutePageNumber: pageNum + 1)
            if let resolvedPage = runtime.pageResolver.resolvePage(absolutePageIndex: pageNum) {
                let contentView = (containerView as? RDEPUBTextContentView) ?? RDEPUBTextContentView()
                contentView.delegate = self
                contentView.configure(
                    page: resolvedPage.page,
                    pageNumber: pageNum + 1,
                    totalPages: pageCountOfReaderView(readerView: readerView),
                    configuration: configuration,
                    highlights: textHighlights(for: resolvedPage.page),
                    searchState: searchState(for: resolvedPage.page)
                )
                return contentView
            }
        }

        if let textBook, let page = textBook.page(at: pageNum + 1) {
            let contentView = (containerView as? RDEPUBTextContentView) ?? RDEPUBTextContentView()
            contentView.delegate = self
            contentView.configure(
                page: page,
                pageNumber: pageNum + 1,
                totalPages: textBook.pages.count,
                configuration: configuration,
                highlights: textHighlights(for: page),
                searchState: searchState(for: page)
            )
            return contentView
        }

        guard let publication,
              let request = request(for: pageNum) else {
            return containerView ?? UIView()
        }

        let contentView = (containerView as? RDEPUBWebContentView) ?? RDEPUBWebContentView()
        contentView.delegate = self
        contentView.configure(
            publication: publication,
            request: request,
            pageNumber: pageNum + 1,
            totalPages: activePages.count,
            theme: configuration.theme
        )
        return contentView
    }

    /// 返回页面内容视图的重用标识符（区分文本与 Web 渲染）
    public func pageIdentifier(readerView: RDReaderView, pageNum: Int) -> String? {
        (textBook == nil && readerContext.bookPageMap == nil)
            ? NSStringFromClass(RDEPUBWebContentView.self)
            : NSStringFromClass(RDEPUBTextContentView.self)
    }

    /// 获取指定文本页面上的高亮标注列表
    private func textHighlights(for page: RDEPUBTextPage) -> [RDEPUBHighlight] {
        if let textBook,
           let chapterData = textBook.chapterData(for: page.href) {
            return chapterData.highlights(on: page, from: activeHighlights)
        }

        guard let publication else {
            return activeHighlights.filter { $0.location.href == page.href }
        }
        let pageHref = publication.resourceResolver.normalizedHref(page.href) ?? page.href
        return activeHighlights.filter {
            (publication.resourceResolver.normalizedHref($0.location.href) ?? $0.location.href) == pageHref
        }
    }

    /// 返回当前文本页需要展示的搜索状态。
    /// 这里会先按页过滤命中结果，并把 currentMatchIndex 重映射到当前页内的局部索引，
    /// 这样渲染层不需要再关心 href 规范化差异。
    private func searchState(for page: RDEPUBTextPage) -> RDEPUBSearchState? {
        guard let globalSearchState = searchState else { return nil }

        let matches: [RDEPUBSearchMatch]
        let currentMatchIndex: Int?

        if let chapterData = chapterData(for: page),
           let resolvedState = resolvedSearchState(
                for: page,
                chapterData: chapterData,
                globalSearchState: globalSearchState
           ) {
            matches = resolvedState.matches
            currentMatchIndex = resolvedState.currentMatchIndex
        } else {
            matches = globalSearchState.matches.filter { searchMatch in
                searchMatchBelongsToPage(searchMatch, page: page)
            }
            currentMatchIndex = globalSearchState.currentMatch.flatMap { currentMatch in
                matches.firstIndex(of: currentMatch)
            }
        }
        guard !matches.isEmpty || globalSearchState.currentMatch != nil else {
            return globalSearchState.matches.isEmpty ? globalSearchState : nil
        }
        return RDEPUBSearchState(
            keyword: globalSearchState.keyword,
            matches: matches,
            currentMatchIndex: currentMatchIndex
        )
    }

    private func resolvedSearchState(
        for page: RDEPUBTextPage,
        chapterData: RDEPUBChapterData,
        globalSearchState: RDEPUBSearchState
    ) -> RDEPUBSearchState? {
        let normalizedKeyword = globalSearchState.keyword.trimmingCharacters(in: .whitespacesAndNewlines)
        guard !normalizedKeyword.isEmpty else {
            return globalSearchState.matches.isEmpty ? globalSearchState : nil
        }

        let normalizedHref = normalizedPageHref(for: page)
        let exactMatches = exactChapterSearchMatches(
            in: chapterData,
            keyword: normalizedKeyword,
            normalizedHref: normalizedHref
        )
        let pageMatches = exactMatches.filter { match in
            guard let rangeLocation = match.rangeLocation else { return false }
            let range = NSRange(location: rangeLocation, length: max(match.rangeLength, 1))
            return NSIntersectionRange(range, page.contentRange).length > 0
        }

        let currentLocalMatchIndex = globalSearchState.currentMatch?.localMatchIndex
        let currentMatchIndex = currentLocalMatchIndex.flatMap { localMatchIndex in
            pageMatches.firstIndex(where: { $0.localMatchIndex == localMatchIndex })
        }

        guard !pageMatches.isEmpty || currentMatchIndex != nil else {
            return globalSearchState.matches.isEmpty ? globalSearchState : nil
        }

        return RDEPUBSearchState(
            keyword: globalSearchState.keyword,
            matches: pageMatches,
            currentMatchIndex: currentMatchIndex
        )
    }

    private func exactChapterSearchMatches(
        in chapterData: RDEPUBChapterData,
        keyword: String,
        normalizedHref: String
    ) -> [RDEPUBSearchMatch] {
        let source = chapterData.attributedContent.string as NSString
        let fullLength = source.length
        guard fullLength > 0 else { return [] }

        var matches: [RDEPUBSearchMatch] = []
        var localMatchIndex = 0
        var searchRange = NSRange(location: 0, length: fullLength)

        while searchRange.length > 0 {
            let foundRange = source.range(of: keyword, options: [.caseInsensitive], range: searchRange)
            guard foundRange.location != NSNotFound else { break }

            let progressionDenominator = max(fullLength - 1, 1)
            let progression = Double(foundRange.location) / Double(progressionDenominator)
            matches.append(
                RDEPUBSearchMatch(
                    href: normalizedHref,
                    progression: progression,
                    previewText: previewText(in: source, matchRange: foundRange),
                    localMatchIndex: localMatchIndex,
                    rangeLocation: foundRange.location,
                    rangeLength: max(foundRange.length, 1),
                    rangeAnchor: chapterData.rangeAnchor(for: foundRange)
                )
            )

            localMatchIndex += 1
            let nextLocation = foundRange.location + max(foundRange.length, 1)
            if nextLocation >= fullLength {
                break
            }
            searchRange = NSRange(location: nextLocation, length: fullLength - nextLocation)
        }

        return matches
    }

    private func previewText(in text: NSString, matchRange: NSRange) -> String {
        let previewRadius = 12
        let start = max(matchRange.location - previewRadius, 0)
        let end = min(matchRange.location + matchRange.length + previewRadius, text.length)
        let range = NSRange(location: start, length: max(end - start, 0))
        return text.substring(with: range).trimmingCharacters(in: .whitespacesAndNewlines)
    }

    private func chapterData(for page: RDEPUBTextPage) -> RDEPUBChapterData? {
        if let textBook,
           let chapterData = textBook.chapterData(for: page.href) {
            return chapterData
        }

        guard let runtimeChapter = runtime.chapterRuntimeStore.chapterData(for: page.spineIndex) else {
            return nil
        }
        return makeChapterData(from: runtimeChapter, chapterIndex: page.chapterIndex)
    }

    private func makeChapterData(
        from runtimeChapter: RDEPUBRuntimeChapter,
        chapterIndex: Int
    ) -> RDEPUBChapterData {
        let textChapter = RDEPUBTextChapter(
            chapterIndex: chapterIndex,
            spineIndex: runtimeChapter.spineIndex,
            href: runtimeChapter.href,
            title: runtimeChapter.title,
            attributedContent: runtimeChapter.typesetAttributedString,
            fragmentOffsets: runtimeChapter.chapterOffsetMap.fragmentOffsets,
            pageBreakReasons: runtimeChapter.pages.map(\.metadata.breakReason),
            pages: runtimeChapter.pages
        )
        return RDEPUBChapterData(
            chapter: textChapter,
            indexTable: RDEPUBTextIndexTable(chapters: [textChapter])
        )
    }

    private func searchMatchBelongsToPage(_ searchMatch: RDEPUBSearchMatch, page: RDEPUBTextPage) -> Bool {
        if let textBook,
           let chapterData = textBook.chapterData(for: page.href),
           let range = chapterData.absoluteRange(for: searchMatch) {
            return NSIntersectionRange(range, page.contentRange).length > 0
        }

        let pageHref = normalizedPageHref(for: page)
        let matchHref = normalizedSearchHref(searchMatch.href)
        guard pageHref == matchHref else { return false }

        guard let rangeLocation = searchMatch.rangeLocation else {
            return false
        }
        let range = NSRange(location: rangeLocation, length: searchMatch.rangeLength)
        return NSIntersectionRange(range, page.contentRange).length > 0
    }

    private func normalizedPageHref(for page: RDEPUBTextPage) -> String {
        guard let publication else { return page.href }
        return publication.resourceResolver.normalizedHref(page.href) ?? page.href
    }

    private func normalizedSearchHref(_ href: String) -> String {
        guard let publication else { return href }
        return publication.resourceResolver.normalizedHref(href) ?? href
    }

    /// 根据规范化 href 获取文本章节数据
    func textChapterData(forNormalizedHref href: String) -> RDEPUBChapterData? {
        readerContext.textChapterData(forNormalizedHref: href)
    }

    /// 返回阅读器顶部工具视图
    public func topToolView(readerView: RDReaderView) -> UIView? {
        topToolView
    }

    /// 返回阅读器底部工具视图
    public func bottomToolView(readerView: RDReaderView) -> UIView? {
        bottomToolView
    }

    /// 页码变化回调：清除选区、同步阅读状态、检测到达末尾
    public func pageNum(readerView: RDReaderView, pageNum: Int) {
        readerContext.markUserNavigationActivity()
        updateCurrentSelection(nil)
        reconcileTextPaginationSizeIfNeeded(for: pageNum)

        // 用户开始导航时，应用后台解析完成的完整 map
        runtime.applyPendingFullPageMapIfNeeded()

        if readerContext.bookPageMap != nil {
            _ = runtime.prepareOnDemandChapter(forAbsolutePageNumber: pageNum + 1)
            runtime.extendPartialBookPageMapIfNeeded(currentPageNumber: pageNum + 1)
        }

        let totalPages = pageCountOfReaderView(readerView: readerView)
        if totalPages > 0, pageNum == totalPages - 1 {
            delegate?.epubReaderDidReachEnd(self)
        }

        if (textBook != nil || readerContext.bookPageMap != nil),
           let location = resolvedTextLocation(forPageNumber: pageNum + 1) {
            persist(location: location)
            synchronizeTextReadingState(pageNumber: pageNum + 1, location: location)
            return
        }

        if let location = fallbackLocation(for: pageNum) {
            persist(location: location)
        }
        if readingSession?.navigatorState == .jumping || readingSession?.navigatorState == .moving {
            readingSession?.transition(to: .idle)
        }
    }

    /// 屏幕方向即将变化回调，捕获待恢复的展示位置
    public func readerViewOrientationWillChange(readerView: RDReaderView, isLandscape: Bool) {
        _ = isLandscape
        runtime.viewportMonitor.capturePendingPresentationRestoreLocation()
    }

    /// 检测页面尺寸变化并触发重新分页（避免布局错乱）
    private func reconcileTextPaginationSizeIfNeeded(for pageNum: Int) {
        guard textBook != nil || readerContext.bookPageMap != nil,
              !isRepaginating,
              !isReconcilingTextPaginationSize,
              pageNum >= 0,
              let lastTextPaginationPageSize else {
            return
        }

        let resolvedSize = readerView.resolvedSinglePageSize(pageNum: pageNum)
        guard resolvedSize.width > 0,
              resolvedSize.height > 0 else {
            return
        }

        let sizeChanged = abs(resolvedSize.width - lastTextPaginationPageSize.width) > 0.5
            || abs(resolvedSize.height - lastTextPaginationPageSize.height) > 0.5
        guard sizeChanged else {
            return
        }

        isReconcilingTextPaginationSize = true
        DispatchQueue.main.async { [weak self] in
            guard let self else { return }
            self.isReconcilingTextPaginationSize = false
            guard (self.textBook != nil || self.readerContext.bookPageMap != nil), !self.isRepaginating else { return }
            self.repaginatePreservingCurrentLocation()
        }
    }
}