//
//  RDURLReaderController.swift
//  RDReaderDemo
//
//  文件职责：URL 阅读器入口控制器，根据文件类型自动选择阅读器。
//  该文件是 ReadViewSDK 的最简使用入口：
//  - .epub 文件：直接创建 RDEPUBReaderController
//  - 其他文本文件：通过 RDPlainTextBookBuilder 分页后创建 RDEPUBReaderController
//  - 分页失败时回退到纯文本 UITextView 展示
//
//  架构位置：RDReaderView 四层架构中第四层（读者 UI）的入口控制器。
//

import UIKit

/// URL 阅读器入口控制器
/// 接收一个书籍文件 URL，根据文件类型自动创建对应的阅读器控制器：
/// - EPUB 文件：直接使用 RDEPUBReaderController
/// - 纯文本文件：先通过 RDPlainTextBookBuilder 分页，再使用 RDEPUBReaderController
/// - 分页失败：回退到纯文本 UITextView 展示
///
/// 使用方式：
/// ```swift
/// let controller = RDURLReaderController(bookURL: fileURL)
/// navigationController?.pushViewController(controller, animated: true)
/// ```
public final class RDURLReaderController: UIViewController {
    private struct PendingDemoPageRequest {
        let pageNumber: Int
        let animated: Bool
        var attemptCount: Int
    }

    /// 书籍文件 URL
    private let bookURL: URL
    /// EPUB 阅读器配置（字体、行距、主题等）
    private let epubConfiguration: RDEPUBReaderConfiguration
    /// 内嵌的阅读器控制器
    private var embeddedController: UIViewController?
    private let demoStateLabel: UILabel = {
        let label = UILabel()
        label.accessibilityIdentifier = "demo.reader.state"
        label.font = .systemFont(ofSize: 1)
        label.textColor = .clear
        label.alpha = 0.01
        label.isAccessibilityElement = true
        label.text = "reader=opening"
        return label
    }()
    private var pendingDemoPageRequest: PendingDemoPageRequest?
    private var isRetryingPendingDemoPage = false
    private let maxPendingDemoPageAttempts = 24
    private let pendingDemoPageRetryDelay: TimeInterval = 0.25

    /// 初始化方法
    /// - Parameters:
    ///   - bookURL: 书籍文件的本地 URL
    ///   - epubConfiguration: EPUB 阅读器配置，默认使用标准配置
    public init(
        bookURL: URL,
        epubConfiguration: RDEPUBReaderConfiguration = RDEPUBReaderConfiguration()
    ) {
        self.bookURL = bookURL
        self.epubConfiguration = epubConfiguration
        super.init(nibName: nil, bundle: nil)
    }

    @available(*, unavailable)
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    /// 视图加载完成后，设置背景色、标题并嵌入阅读器控制器
    public override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .systemBackground
        title = bookURL.deletingPathExtension().lastPathComponent
        embedReaderController()
        installDemoStateLabel()
    }

    public override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        emitDemoState()
    }

    /// 切换阅读器的翻页模式（Demo 用）
    /// - Parameter displayType: 目标翻页模式
    public func applyDemoDisplayType(_ displayType: RDReaderView.DisplayType) {
        readerController?.configuration.displayType = displayType
        emitDemoState(prefix: "display=\(displayType.demoArgumentValue)")
    }

    /// 跳转到指定页码（Demo 用）
    /// - Parameters:
    ///   - pageNumber: 目标页码
    ///   - animated: 是否动画过渡
    /// - Returns: 是否成功跳转
    @discardableResult
    public func goToDemoPage(_ pageNumber: Int, animated: Bool = false) -> Bool {
        let moved = performDemoPageNavigation(pageNumber, animated: animated)
        if moved {
            pendingDemoPageRequest = nil
            isRetryingPendingDemoPage = false
        } else {
            queuePendingDemoPageNavigation(pageNumber, animated: animated)
        }
        return moved
    }

    /// 执行翻页模式切换序列（Demo 用）
    /// 按照指定顺序和延迟依次切换翻页模式
    /// - Parameters:
    ///   - displayTypes: 翻页模式数组
    ///   - initialPageNumber: 可选的初始跳转页码
    ///   - stepDelay: 每步之间的延迟时间（秒）
    public func runDemoDisplaySequence(
        _ displayTypes: [RDReaderView.DisplayType],
        initialPageNumber: Int? = nil,
        stepDelay: TimeInterval = 1.0
    ) {
        let normalizedDelay = max(stepDelay, 0.1)
        if let initialPageNumber {
            DispatchQueue.main.asyncAfter(deadline: .now() + normalizedDelay) { [weak self] in
                _ = self?.goToDemoPage(initialPageNumber)
            }
        }

        for (index, displayType) in displayTypes.enumerated() {
            let delay = normalizedDelay * Double(index + 1 + (initialPageNumber == nil ? 0 : 1))
            DispatchQueue.main.asyncAfter(deadline: .now() + delay) { [weak self] in
                self?.applyDemoDisplayType(displayType)
            }
        }
    }

    /// 嵌入阅读器控制器到当前视图层级
    /// 根据文件类型选择合适的阅读器控制器，并通过 Child View Controller 方式嵌入
    private func embedReaderController() {
        let controller: UIViewController
        if bookURL.pathExtension.lowercased() == "epub" {
            controller = RDEPUBReaderController(
                epubURL: bookURL,
                configuration: epubConfiguration
            )
        } else {
            let bookIdentifier = bookURL.lastPathComponent
            let bookTitle = bookURL.deletingPathExtension().lastPathComponent
            let pageSize = currentTextPageSize()
            let renderStyle = currentTextRenderStyle()
            let builder = RDPlainTextBookBuilder(
                layoutConfig: RDEPUBTextLayoutConfig(
                    frameWidth: pageSize.width,
                    frameHeight: pageSize.height,
                    edgeInsets: epubConfiguration.reflowableContentInsets,
                    numberOfColumns: 1,
                    columnGap: 20,
                    avoidOrphans: true,
                    avoidWidows: true,
                    avoidPageBreakInsideEnabled: true,
                    hyphenation: true,
                    imageMaxHeightRatio: 0.85
                )
            )
            if let textBook = try? builder.build(textFileURL: bookURL, pageSize: pageSize, style: renderStyle) {
                controller = RDEPUBReaderController(
                    textBook: textBook,
                    bookIdentifier: bookIdentifier,
                    title: bookTitle,
                    textFileURL: bookURL,
                    configuration: epubConfiguration
                )
            } else {
                // 分页失败时回退到纯文本展示
                let fallback = UIViewController()
                let textView = UITextView()
                textView.isEditable = false
                textView.text = rd_decodeTextFile(url: bookURL)
                fallback.view = textView
                controller = fallback
            }
        }
        embeddedController = controller
        addChild(controller)
        controller.view.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(controller.view)
        NSLayoutConstraint.activate([
            controller.view.topAnchor.constraint(equalTo: view.topAnchor),
            controller.view.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            controller.view.trailingAnchor.constraint(equalTo: view.trailingAnchor),
            controller.view.bottomAnchor.constraint(equalTo: view.bottomAnchor),
        ])
        controller.didMove(toParent: self)
        readerController?.delegate = self
        emitDemoState()
    }

    /// 获取内嵌的 EPUB 阅读器控制器（如果存在）
    private var readerController: RDEPUBReaderController? {
        embeddedController as? RDEPUBReaderController
    }

    @discardableResult
    private func performDemoPageNavigation(_ pageNumber: Int, animated: Bool) -> Bool {
        guard let readerController else { return false }
        guard pageNumber > 0 else { return false }

        let totalPages = readerController.textBook?.pages.count ?? readerController.activePages.count
        let numPages = readerController.readerView.numberOfPages()
        print("[ReadViewDemo] performDemoPageNavigation(\(pageNumber)): textBook.pages=\(totalPages), readerView.numberOfPages=\(numPages), currentPage=\(readerController.readerView.currentPage)")
        guard pageNumber <= totalPages else { return false }

        readerController.readerView.transitionToPage(pageNum: pageNumber - 1, animated: animated)
        print("[ReadViewDemo] performDemoPageNavigation(\(pageNumber)): after transition, currentPage=\(readerController.readerView.currentPage)")
        emitDemoState(prefix: "page=\(pageNumber)")
        return true
    }

    private func queuePendingDemoPageNavigation(_ pageNumber: Int, animated: Bool) {
        if let pendingDemoPageRequest,
           pendingDemoPageRequest.pageNumber == pageNumber,
           pendingDemoPageRequest.animated == animated {
            return
        }

        pendingDemoPageRequest = PendingDemoPageRequest(
            pageNumber: pageNumber,
            animated: animated,
            attemptCount: 0
        )
        retryPendingDemoPageIfNeeded()
    }

    private func retryPendingDemoPageIfNeeded() {
        guard !isRetryingPendingDemoPage else { return }
        guard pendingDemoPageRequest != nil else { return }

        isRetryingPendingDemoPage = true
        DispatchQueue.main.asyncAfter(deadline: .now() + pendingDemoPageRetryDelay) { [weak self] in
            self?.attemptPendingDemoPageNavigation()
        }
    }

    private func attemptPendingDemoPageNavigation() {
        guard var pendingDemoPageRequest else {
            isRetryingPendingDemoPage = false
            return
        }

        if performDemoPageNavigation(pendingDemoPageRequest.pageNumber, animated: pendingDemoPageRequest.animated) {
            self.pendingDemoPageRequest = nil
            isRetryingPendingDemoPage = false
            return
        }

        pendingDemoPageRequest.attemptCount += 1
        if pendingDemoPageRequest.attemptCount >= maxPendingDemoPageAttempts {
            self.pendingDemoPageRequest = nil
            isRetryingPendingDemoPage = false
            print("[ReadViewDemo] automation page=\(pendingDemoPageRequest.pageNumber) failed after \(pendingDemoPageRequest.attemptCount) attempts")
            return
        }

        self.pendingDemoPageRequest = pendingDemoPageRequest
        DispatchQueue.main.asyncAfter(deadline: .now() + pendingDemoPageRetryDelay) { [weak self] in
            self?.attemptPendingDemoPageNavigation()
        }
    }

    /// 输出当前阅读器状态日志（Demo 调试用）
    private func logDemoState(prefix: String) {
        guard let readerController else { return }
        let location = readerController.currentLocation
        let href = location?.href ?? "nil"
        let progression = location.map { String(format: "%.4f", $0.navigationProgression) } ?? "nil"
        let page = readerController.currentPageNumber.map(String.init) ?? "nil"
        print("[ReadViewDemo] automation \(prefix) -> page \(page) href \(href) progression \(progression)")
    }

    private func installDemoStateLabel() {
        view.addSubview(demoStateLabel)
        demoStateLabel.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate([
            demoStateLabel.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            demoStateLabel.topAnchor.constraint(equalTo: view.topAnchor),
            demoStateLabel.widthAnchor.constraint(equalToConstant: 1),
            demoStateLabel.heightAnchor.constraint(equalToConstant: 1)
        ])
    }

    private func emitDemoState(prefix: String? = nil) {
        let page = readerController?.currentPageNumber.map(String.init) ?? "nil"
        let display = readerController?.configuration.displayType.demoArgumentValue ?? epubConfiguration.displayType.demoArgumentValue
        let toolbar = readerController?.readerView.isShowToolView == true ? "visible" : "hidden"
        let highlights = readerController?.highlights.count ?? 0
        let selection = readerController?.currentSelection == nil ? 0 : 1
        let state = "reader=opened page=\(page) display=\(display) toolbar=\(toolbar) highlights=\(highlights) selection=\(selection)"
        demoStateLabel.text = state
        if let prefix {
            logDemoState(prefix: prefix)
        } else {
            print("[ReadViewDemo] automation \(state)")
        }
    }

    /// 计算文本分页的页面尺寸。
    /// 分页器使用完整 viewport，真实可绘制区域由 layoutConfig.edgeInsets 控制，
    /// 以保持与页面展示时的内容几何一致。
    private func currentTextPageSize() -> CGSize {
        UIScreen.main.bounds.size
    }

    /// 根据当前配置生成文本渲染样式
    private func currentTextRenderStyle() -> RDEPUBTextRenderStyle {
        let font = epubConfiguration.fontChoice.font(ofSize: epubConfiguration.fontSize)
        let lineSpacing = max(font.lineHeight * (epubConfiguration.lineHeightMultiple - 1), 4)
        return RDEPUBTextRenderStyle(
            font: font,
            lineSpacing: lineSpacing,
            textColor: epubConfiguration.theme.contentTextColor,
            backgroundColor: epubConfiguration.theme.contentBackgroundColor
        )
    }

    /// 解码文本文件内容
    /// 尝试 UTF-8 编码，失败则尝试 GBK 和 GB2312 编码
    private func rd_decodeTextFile(url: URL) -> String {
        if let content = try? NSString(contentsOf: url, encoding: String.Encoding.utf8.rawValue) as String {
            return content
        }
        if let content = try? NSString(contentsOf: url, encoding: 0x80000632) as String {
            return content
        }
        if let content = try? NSString(contentsOf: url, encoding: 0x80000631) as String {
            return content
        }
        return ""
    }
}

extension RDURLReaderController: RDEPUBReaderDelegate {
    public func epubReader(_ reader: UIViewController, didOpen publication: RDEPUBPublication) {
        retryPendingDemoPageIfNeeded()
        emitDemoState()
    }

    public func epubReader(_ reader: UIViewController, didUpdateLocation location: RDEPUBLocation) {
        retryPendingDemoPageIfNeeded()
        emitDemoState()
    }

    public func epubReader(_ reader: UIViewController, didChangeSelection selection: RDEPUBSelection?) {
        emitDemoState(prefix: "selection=\(selection == nil ? 0 : 1)")
    }

    public func epubReader(_ reader: UIViewController, didUpdateHighlights highlights: [RDEPUBHighlight]) {
        emitDemoState(prefix: "highlights=\(highlights.count)")
    }
}

/// 翻页模式扩展：提供 Demo 命令行参数值
private extension RDReaderView.DisplayType {
    /// 返回翻页模式对应的 Demo 命令行参数字符串
    var demoArgumentValue: String {
        switch self {
        case .pageCurl:
            return "pageCurl"
        case .horizontalScroll:
            return "horizontalScroll"
        case .verticalScroll:
            return "verticalScroll"
        }
    }
}