import UIKit

public final class RDEPUBReaderController: UIViewController {

    public weak var delegate: RDEPUBReaderDelegate?

    public var configuration: RDEPUBReaderConfiguration {
        didSet {
            // M-09: Apply all configuration side effects even before view is loaded,
            // but UI-dependent actions only after view is loaded.
            readerContext.configuration = configuration
            guard isViewLoaded else { return }
            applyWebViewDebugPolicy()
            persistReaderSettingsIfNeeded()
            let oldConfiguration = oldValue
            applyReaderViewConfiguration()

            if isExternalTextBook {
                if requiresRepagination(from: oldConfiguration, to: configuration) {
                    rebuildExternalTextBook()
                } else if requiresVisibleRefresh(from: oldConfiguration, to: configuration) {
                    refreshVisibleContentPreservingLocation()
                }
                return
            }

            guard publication != nil else { return }
            if requiresRepagination(from: oldConfiguration, to: configuration) {
                repaginatePreservingCurrentLocation()
            } else if requiresVisibleRefresh(from: oldConfiguration, to: configuration) {
                refreshVisibleContentPreservingLocation()
            }
        }
    }

    public var currentLocation: RDEPUBLocation? {
        currentVisibleLocation()
    }

    public var currentPageNumber: Int? {
        guard readerView.currentPage >= 0 else { return nil }
        return readerView.currentPage + 1
    }

    public internal(set) var currentSelection: RDEPUBSelection? {
        get { readerContext.currentSelection }
        set { readerContext.currentSelection = newValue }
    }

    public var highlights: [RDEPUBHighlight] {
        activeHighlights
    }

    public var bookmarks: [RDEPUBBookmark] {
        activeBookmarks
    }

    public var annotations: [RDEPUBAnnotation] {
        let merged = activeHighlights.map(\.annotation) + activeBookmarks.map(\.annotation)
        return merged.sorted { $0.createdAt < $1.createdAt }
    }

    public var tableOfContents: [EPUBTableOfContentsItem] {
        publication?.tableOfContents ?? []
    }

    public var flattenedTableOfContents: [RDEPUBReaderTableOfContentsItem] {
        guard let publication else { return [] }
        return flattenedTableOfContentsItems(from: publication.tableOfContents)
    }

    public var currentTableOfContentsItem: RDEPUBReaderTableOfContentsItem? {
        resolvedCurrentTableOfContentsItem()
    }

    let epubURL: URL

    let persistence: RDEPUBReaderPersistence?

    let dependencies: RDEPUBReaderDependencies

    let readerView = RDEpubReaderView()

    let loadingIndicator: UIActivityIndicatorView = {
        UIActivityIndicatorView(style: .large)
    }()

    let errorLabel: UILabel = {
        let label = UILabel()
        label.numberOfLines = 0
        label.textAlignment = .center
        label.textColor = .darkGray
        label.isHidden = true
        return label
    }()

    let paginationHostView = UIView()

    /// Chapter-level shared display content/layouter for text pages
    /// (LONG_CHAPTER_MEMORY_OPTIMIZATION_PLAN.md P1-1/P1-3).
    let textDisplayCache = RDEPUBChapterDisplayContentCache()

    lazy var readerContext = RDEPUBReaderContext(controller: self)

    var parser: RDEPUBParser? {
        get { readerContext.parser }
        set { readerContext.parser = newValue }
    }

    var publication: RDEPUBPublication? {
        get { readerContext.publication }
        set { readerContext.publication = newValue }
    }

    var readingSession: RDEPUBReadingSession? {
        get { readerContext.readingSession }
        set { readerContext.readingSession = newValue }
    }

    var textBook: RDEPUBTextBook? {
        get { readerContext.textBook }
        set { readerContext.textBook = newValue }
    }

    var activePages: [EPUBPage] {
        readerContext.activePages
    }

    var activeChapters: [EPUBChapterInfo] {
        readerContext.activeChapters
    }

    var activeBookmarks: [RDEPUBBookmark] {
        get { readerContext.activeBookmarks }
        set { readerContext.activeBookmarks = newValue }
    }

    var activeHighlights: [RDEPUBHighlight] {
        get { readerContext.activeHighlights }
        set { readerContext.activeHighlights = newValue }
    }

    lazy var topToolView = runtime.makeTopToolView()

    lazy var bottomToolView = runtime.makeBottomToolView()

    lazy var searchBarView = RDEPUBReaderSearchBarView()

    /// 试读墙视图缓存（经 delegate 获取一次后复用；见 RDEPUBReaderController+Trial）
    var cachedTrialWallView: UIView?

    /// 阅读器进入前宿主导航栏的真实状态。详情页使用自定义导航栏时系统栏原本
    /// 就是隐藏的，退出阅读器必须恢复该状态，不能无条件显示系统导航栏。
    private var navigationBarHiddenBeforeReader: Bool?

    private(set) var isSearchBarVisible = false

    var currentBookIdentifier: String? {
        get { readerContext.currentBookIdentifier }
        set { readerContext.currentBookIdentifier = newValue }
    }

    var textBookCache: RDEPUBTextBookCache { readerContext.textBookCache }

    var currentBrightness: CGFloat {
        get { readerContext.currentBrightness }
        set { readerContext.currentBrightness = newValue }
    }

    var didStartInitialLoad: Bool {
        get { readerContext.didStartInitialLoad }
        set { readerContext.didStartInitialLoad = newValue }
    }

    var isRepaginating: Bool {
        get { readerContext.isRepaginating }
        set { readerContext.isRepaginating = newValue }
    }

    var lastTextPaginationPageSize: CGSize? {
        get { readerContext.lastTextPaginationPageSize }
        set { readerContext.lastTextPaginationPageSize = newValue }
    }

    var isReconcilingTextPaginationSize = false

    var paginationToken: UUID {
        get { readerContext.paginationToken }
        set { readerContext.paginationToken = newValue }
    }

    var searchState: RDEPUBSearchState? {
        get { readerContext.searchState }
        set { readerContext.searchState = newValue }
    }

    var isExternalTextBook: Bool {
        get { readerContext.isExternalTextBook }
        set { readerContext.isExternalTextBook = newValue }
    }

    var textFileURL: URL? {
        get { readerContext.textFileURL }
        set { readerContext.textFileURL = newValue }
    }

    lazy var readerAssemblyCoordinator = RDEPUBReaderAssemblyCoordinator(context: readerContext)

    lazy var runtime = RDEPUBReaderRuntime(context: readerContext)

    public init(
        epubURL: URL,
        configuration: RDEPUBReaderConfiguration = .default,
        persistence: RDEPUBReaderPersistence? = RDEPUBUserDefaultsPersistence(),
        dependencies: RDEPUBReaderDependencies = .live
    ) {
        let persistedSettings = persistence?.loadReaderSettings()
        self.epubURL = epubURL
        self.configuration = persistedSettings?.applying(to: configuration) ?? configuration
        self.persistence = persistence
        self.dependencies = dependencies
        let brightness = max(0, min(1, persistedSettings?.brightness ?? dependencies.environment.currentBrightness))
        super.init(nibName: nil, bundle: nil)

        readerContext.dependencies = dependencies
        readerContext.configuration = self.configuration
        readerContext.epubURL = epubURL
        readerContext.persistence = persistence
        self.currentBrightness = brightness
        applyWebViewDebugPolicy()
    }

    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    private func applyWebViewDebugPolicy() {
        RDEPUBWebViewDebug.applyDebugPolicy(
            inspectableEnabled: configuration.allowsInspectableWebViews,
            verboseLoggingEnabled: configuration.enablesVerboseWebViewLogging
        )
    }

    public convenience init(
        textBook: RDEPUBTextBook,
        bookIdentifier: String,
        title: String,
        textFileURL: URL? = nil,
        configuration: RDEPUBReaderConfiguration = .default,
        persistence: RDEPUBReaderPersistence? = RDEPUBUserDefaultsPersistence(),
        dependencies: RDEPUBReaderDependencies = .live
    ) {
        let persistedSettings = persistence?.loadReaderSettings()
        let resolvedConfig = persistedSettings?.applying(to: configuration) ?? configuration

        self.init(
            epubURL: URL(string: "about:blank")!,
            configuration: resolvedConfig,
            persistence: persistence,
            dependencies: dependencies
        )
        self.isExternalTextBook = true
        self.textBook = textBook
        self.textFileURL = textFileURL
        self.currentBookIdentifier = bookIdentifier
        self.title = title
        self.didStartInitialLoad = true
    }

    public override func viewDidLoad() {
        super.viewDidLoad()
        currentBrightness = currentBrightness
        readerAssemblyCoordinator.assembleInterface()
        readerAssemblyCoordinator.finishExternalTextBookLaunchIfNeeded()
        readerView.onToolViewVisibilityChanged = { [weak self] isVisible in
            self?.handleToolViewVisibilityChanged(isVisible: isVisible)
        }
    }

    public override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        if navigationBarHiddenBeforeReader == nil {
            navigationBarHiddenBeforeReader = navigationController?.isNavigationBarHidden
        }
        navigationController?.setNavigationBarHidden(true, animated: animated)
        navigationController?.interactivePopGestureRecognizer?.delegate = self
        navigationController?.interactivePopGestureRecognizer?.isEnabled = true
    }

    public override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        if let navigationBarHiddenBeforeReader {
            navigationController?.setNavigationBarHidden(
                navigationBarHiddenBeforeReader,
                animated: animated
            )
        }
    }

    public override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        startInitialLoadIfNeeded()
        RDEPUBSettingsFlipAutomation.startIfNeeded(controller: self)
    }

    public override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        runtime.viewportMonitor.viewDidLayoutSubviews()
    }

    public override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        runtime.handleMemoryWarning()
        textDisplayCache.removeAll()
    }

    public override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
        super.viewWillTransition(to: size, with: coordinator)
        runtime.viewportMonitor.viewWillTransition(with: coordinator)
        coordinator.animate(alongsideTransition: nil) { _ in
            RDEPUBMemoryProbe.log("orientationTransition size=\(Int(size.width))x\(Int(size.height))")
        }
    }

    func showSearchBar() {
        guard !isSearchBarVisible else { return }
        isSearchBarVisible = true
        searchBarView.apply(theme: configuration.theme)

        searchBarView.onSearchSubmit = { [weak self] keyword in
            self?.searchBarView.showSearching()
            self?.runtime.search(keyword: keyword)
            self?.updateSearchCount()
        }
        searchBarView.onSearchTextChanged = { [weak self] keyword in
            guard let self else { return }
            let normalizedKeyword = keyword.trimmingCharacters(in: .whitespacesAndNewlines)
            if normalizedKeyword.isEmpty {
                self.runtime.clearSearch()
            } else {
                self.searchBarView.showSearching()
                self.runtime.search(keyword: normalizedKeyword)
            }
            self.updateSearchCount()
        }
        searchBarView.onSearchPrevious = { [weak self] in
            _ = self?.runtime.searchPrevious()
            self?.updateSearchCount()
        }
        searchBarView.onSearchNext = { [weak self] in
            _ = self?.runtime.searchNext()
            self?.updateSearchCount()
        }
        searchBarView.onSelectMatch = { [weak self] matchIndex in
            guard let self else { return }
            let didNavigate = self.runtime.selectSearchMatch(at: matchIndex)
            self.updateSearchCount()
            if didNavigate {
                self.hideSearchBar(clearSearch: false)
            }
        }
        searchBarView.onClose = { [weak self] in
            self?.hideSearchBar(clearSearch: true)
        }

        if readerView.isShowToolView {
            installSearchBarView()
        }
    }

    private func installSearchBarView() {
        guard searchBarView.superview == nil else { return }
        searchBarView.apply(theme: configuration.theme)

        readerView.addSubview(searchBarView)
        readerView.searchBarView = searchBarView
        NSLayoutConstraint.activate([
            searchBarView.leadingAnchor.constraint(equalTo: readerView.leadingAnchor),
            searchBarView.trailingAnchor.constraint(equalTo: readerView.trailingAnchor),
            searchBarView.topAnchor.constraint(equalTo: readerView.topAnchor),
            searchBarView.bottomAnchor.constraint(equalTo: readerView.bottomAnchor)
        ])

        searchBarView.alpha = 0
        searchBarView.presentedView.transform = CGAffineTransform(translationX: 0, y: 40)
        UIView.animate(withDuration: 0.28) {
            self.searchBarView.alpha = 1
            self.searchBarView.presentedView.transform = .identity
        }

        if let keyword = searchState?.keyword, !keyword.isEmpty {
            searchBarView.restoreKeyword(keyword)
            updateSearchCount()
        } else {
            searchBarView.showNoResults()
        }

        DispatchQueue.main.async { [weak self] in
            self?.searchBarView.textField.becomeFirstResponder()
        }
    }

    func hideSearchBar(clearSearch: Bool = false) {
        guard isSearchBarVisible else { return }
        isSearchBarVisible = false

        searchBarView.textField.resignFirstResponder()
        UIView.animate(withDuration: 0.25, animations: {
            self.searchBarView.alpha = 0
            self.searchBarView.presentedView.transform = CGAffineTransform(translationX: 0, y: 40)
        }) { _ in
            self.searchBarView.removeFromSuperview()
            self.searchBarView.alpha = 1
            self.searchBarView.presentedView.transform = .identity
            self.readerView.searchBarView = nil
        }

        if clearSearch {
            runtime.clearSearch()
        }
    }

    func updateSearchCount() {
        guard let searchState else {
            searchBarView.showNoResults()
            return
        }
        searchBarView.updateResults(
            sections: searchResultSections(for: searchState),
            keyword: searchState.keyword,
            currentMatchIndex: searchState.currentMatchIndex
        )
    }

    func handleToolViewVisibilityChanged(isVisible: Bool) {
        if isVisible {
            if isSearchBarVisible {
                installSearchBarView()
            } else if searchState != nil {
                showSearchBar()
            }
        } else {
            if isSearchBarVisible {
                hideSearchBar(clearSearch: false)
            }
        }
    }

}

private extension RDEPUBReaderController {

    func searchResultSections(for searchState: RDEPUBSearchState) -> [RDEPUBReaderSearchSection] {
        let groupedMatches = Dictionary(grouping: Array(searchState.matches.enumerated()), by: { entry in
            searchSectionTitle(for: entry.element)
        })

        let orderedTitles = searchState.matches.reduce(into: [String]()) { titles, match in
            let title = searchSectionTitle(for: match)
            if titles.last != title, titles.contains(title) == false {
                titles.append(title)
            }
        }

        return orderedTitles.compactMap { title in
            guard let matches = groupedMatches[title] else { return nil }
            let items = matches.map { offset, match in
                RDEPUBReaderSearchSection.Item(
                    matchIndex: offset,
                    previewText: match.previewText,
                    isCurrent: offset == searchState.currentMatchIndex
                )
            }
            return RDEPUBReaderSearchSection(title: title, items: items)
        }
    }

    func searchSectionTitle(for match: RDEPUBSearchMatch) -> String {
        guard let publication else {
            return match.href
        }

        let normalizedMatchHref = publication.resourceResolver.normalizedHref(match.href) ?? match.href
        let tocItems = flattenedTableOfContentsItems(from: publication.tableOfContents, includePageNumbers: false)
        if let tocItem = tocItems.last(where: {
            let rawHref = $0.href.components(separatedBy: "#").first ?? $0.href
            let normalizedItemHref = publication.resourceResolver.normalizedHref(rawHref) ?? rawHref
            return normalizedItemHref == normalizedMatchHref
        }) {
            return tocItem.title
        }

        if let spineIndex = publication.resourceResolver.spineIndex(forNormalizedHref: normalizedMatchHref),
           publication.spine.indices.contains(spineIndex) {
            return publication.spine[spineIndex].title
        }

        return normalizedMatchHref
    }
}