import Foundation

/// 搜索协调器，负责管理全文搜索的执行、结果导航和搜索状态通知。
final class RDEPUBReaderSearchCoordinator {
    private unowned let context: RDEPUBReaderContext

    init(context: RDEPUBReaderContext) {
        self.context = context
    }

    private var controller: RDEPUBReaderController? {
        context.controller
    }

    /// 按关键词执行全文搜索，匹配结果自动导航到首个命中位置
    /// - Parameter keyword: 搜索关键词
    func search(keyword: String) {
        guard let controller else { return }
        let normalizedKeyword = keyword.trimmingCharacters(in: .whitespacesAndNewlines)
        guard !normalizedKeyword.isEmpty else {
            clearSearch()
            return
        }

        let matches = resolvedSearchMatches(for: normalizedKeyword)
        controller.searchState = RDEPUBSearchState(
            keyword: normalizedKeyword,
            matches: matches,
            currentMatchIndex: matches.isEmpty ? nil : 0
        )
        notifySearchStateChanged()

        if matches.isEmpty {
            controller.refreshVisibleContentPreservingLocation()
        } else {
            _ = navigateToCurrentSearchMatch(animated: false)
        }
    }

    /// 跳转到下一个搜索匹配项
    /// - Returns: 是否成功跳转
    @discardableResult
    func searchNext() -> Bool {
        advanceSearch(by: 1)
    }

    /// 跳转到上一个搜索匹配项
    /// - Returns: 是否成功跳转
    @discardableResult
    func searchPrevious() -> Bool {
        advanceSearch(by: -1)
    }

    /// 跳转到指定索引的搜索匹配项
    @discardableResult
    func selectSearchMatch(at index: Int) -> Bool {
        guard let controller else { return false }
        guard var searchState = controller.searchState,
              searchState.matches.indices.contains(index) else {
            return false
        }

        searchState.currentMatchIndex = index
        controller.searchState = searchState
        notifySearchStateChanged()
        return navigateToCurrentSearchMatch(animated: true)
    }

    /// 清除搜索状态并刷新当前可见内容
    func clearSearch() {
        guard let controller else { return }
        controller.searchState = nil
        notifySearchStateChanged()
        controller.refreshVisibleContentPreservingLocation()
    }

    /// 构建指定页面的搜索结果展示信息，用于高亮渲染
    /// - Parameter page: 目标页面
    /// - Returns: 搜索展示数据，若无搜索状态则返回 nil
    func searchPresentation(for page: EPUBPage) -> RDEPUBSearchPresentation? {
        guard let controller else { return nil }
        guard let searchState = controller.searchState,
              let publication = controller.publication else {
            return nil
        }

        let pageHrefs: [String]
        if let fixedSpread = page.fixedSpread {
            pageHrefs = fixedSpread.resources.map { publication.resourceResolver.normalizedHref($0.href) ?? $0.href }
        } else if publication.spine.indices.contains(page.spineIndex) {
            pageHrefs = [
                publication.resourceResolver.normalizedHref(publication.spine[page.spineIndex].href)
                    ?? publication.spine[page.spineIndex].href
            ]
        } else {
            pageHrefs = []
        }

        guard !pageHrefs.isEmpty else {
            return nil
        }

        let currentMatch = searchState.currentMatch
        let normalizedCurrentHref = currentMatch.map { publication.resourceResolver.normalizedHref($0.href) ?? $0.href }
        let resources = pageHrefs.map { href in
            let matchCount = searchState.matches.filter {
                (publication.resourceResolver.normalizedHref($0.href) ?? $0.href) == href
            }.count
            let activeLocalMatchIndex = normalizedCurrentHref == href ? currentMatch?.localMatchIndex : nil
            return RDEPUBSearchPresentationResource(
                href: href,
                matchCount: matchCount,
                activeLocalMatchIndex: activeLocalMatchIndex
            )
        }
        return RDEPUBSearchPresentation(keyword: searchState.keyword, resources: resources)
    }

    private func resolvedSearchMatches(for keyword: String) -> [RDEPUBSearchMatch] {
        guard let controller else { return [] }
        if let textBook = controller.textBook {
            if let publication = controller.publication {
                return RDEPUBTextSearchEngine(textBook: textBook, publication: publication).search(keyword: keyword)
            }
            return RDEPUBTextSearchEngine.searchWithoutPublication(textBook: textBook, keyword: keyword)
        }
        if controller.readerContext.bookPageMap != nil, controller.publication != nil {
            return resolvedOnDemandSearchMatches(for: keyword)
        }
        if let parser = controller.parser, let publication = controller.publication {
            return RDEPUBHTMLSearchEngine(parser: parser, publication: publication).search(keyword: keyword)
        }
        return []
    }

    private func resolvedOnDemandSearchMatches(for keyword: String) -> [RDEPUBSearchMatch] {
        guard let controller,
              let publication = controller.publication else {
            return []
        }

        let normalizedKeyword = keyword.trimmingCharacters(in: .whitespacesAndNewlines)
        guard !normalizedKeyword.isEmpty else {
            return []
        }

        let buildableSpineIndices = publication.spine.indices.filter { index in
            let item = publication.spine[index]
            return item.linear && (item.mediaType.contains("html") || item.mediaType.contains("xhtml"))
        }

        var matches: [RDEPUBSearchMatch] = []
        for spineIndex in buildableSpineIndices {
            guard let chapter = try? controller.runtime.chapterLoader.loadChapterSynchronouslyForMigration(
                spineIndex: spineIndex,
                store: controller.runtime.chapterRuntimeStore
            ) else {
                continue
            }

            let chapterData = makeChapterData(from: chapter, chapterIndex: chapter.pages.first?.chapterIndex ?? 0)
            let source = chapter.typesetAttributedString.string as NSString
            let fullLength = source.length
            guard fullLength > 0 else { continue }

            let normalizedHref = publication.resourceResolver.normalizedHref(chapter.href) ?? chapter.href
            var localMatchIndex = 0
            var searchRange = NSRange(location: 0, length: fullLength)

            while searchRange.length > 0 {
                let foundRange = source.range(of: normalizedKeyword, 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: foundRange.length,
                        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 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 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 advanceSearch(by delta: Int) -> Bool {
        guard let controller else { return false }
        guard var searchState = controller.searchState, !searchState.matches.isEmpty else {
            return false
        }

        let currentIndex = searchState.currentMatchIndex ?? 0
        let nextIndex = (currentIndex + delta + searchState.matches.count) % searchState.matches.count
        searchState.currentMatchIndex = nextIndex
        controller.searchState = searchState
        notifySearchStateChanged()
        return navigateToCurrentSearchMatch(animated: true)
    }

    private func notifySearchStateChanged() {
        guard let controller else { return }
        controller.delegate?.epubReader(controller, didUpdateSearchResult: controller.searchState?.result)
        controller.delegate?.epubReader(controller, didChangeCurrentSearchMatch: controller.searchState?.currentMatch)
    }

    private func navigateToCurrentSearchMatch(animated: Bool) -> Bool {
        guard let controller else { return false }
        guard let searchMatch = controller.searchState?.currentMatch else {
            controller.refreshVisibleContentPreservingLocation()
            return false
        }

        if let targetPageNumber = pageNumber(for: searchMatch),
           controller.readerView.currentPage == targetPageNumber - 1 {
            controller.refreshVisibleContentPreservingLocation()
            return true
        }

        let location = RDEPUBLocation(
            bookIdentifier: controller.currentBookIdentifier,
            href: searchMatch.href,
            progression: searchMatch.progression,
            lastProgression: searchMatch.progression,
            fragment: nil,
            rangeAnchor: searchMatch.rangeAnchor
        )
        return controller.restoreReadingLocation(location, animated: animated)
    }

    private func pageNumber(for searchMatch: RDEPUBSearchMatch) -> Int? {
        guard let controller else { return nil }
        if let chapterData = controller.textChapterData(forNormalizedHref: searchMatch.href) {
            if let exactPageNumber = exactPageNumber(
                for: searchMatch,
                in: chapterData,
                keyword: controller.searchState?.keyword
            ) {
                return exactPageNumber
            }

            if let pageNumber = chapterData.pageNumber(for: searchMatch) {
                return pageNumber
            }

            if let rangeLocation = searchMatch.rangeLocation,
               let page = chapterData.page(containing: rangeLocation) {
                return page.absolutePageIndex + 1
            }
        }

        let location = RDEPUBLocation(
            bookIdentifier: controller.currentBookIdentifier,
            href: searchMatch.href,
            progression: searchMatch.progression,
            lastProgression: searchMatch.progression,
            fragment: nil,
            rangeAnchor: searchMatch.rangeAnchor
        )

        if let textBook = controller.textBook, let publication = controller.publication {
            return textBook.pageNumber(
                for: location,
                resolver: publication.resourceResolver,
                bookIdentifier: controller.currentBookIdentifier
            )
        }

        return controller.readingSession?.pageIndex(
            for: location,
            bookIdentifier: controller.currentBookIdentifier
        ).map { $0 + 1 }
    }

    private func exactPageNumber(
        for searchMatch: RDEPUBSearchMatch,
        in chapterData: RDEPUBChapterData,
        keyword: String?
    ) -> Int? {
        let normalizedKeyword = keyword?.trimmingCharacters(in: .whitespacesAndNewlines) ?? ""
        guard !normalizedKeyword.isEmpty else { return nil }

        let source = chapterData.attributedContent.string as NSString
        let fullLength = source.length
        guard fullLength > 0 else { return nil }

        var localMatchIndex = 0
        var searchRange = NSRange(location: 0, length: fullLength)

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

            if localMatchIndex == searchMatch.localMatchIndex,
               let page = chapterData.page(containing: foundRange.location) {
                return page.absolutePageIndex + 1
            }

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

        return nil
    }
}