import UIKit

/// EPUB 阅读器界面组装协调器：负责阅读器初次启动时的 UI 搭建。
///
/// 职责：
/// - 组装阅读器视图层次结构（readerView、loadingIndicator、errorLabel）
/// - 注册内容视图类型
/// - 处理外部纯文本图书的启动收尾逻辑
final class RDEPUBReaderAssemblyCoordinator {
    private unowned let context: RDEPUBReaderContext

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

    /// 组装阅读器界面：添加 readerView、loadingIndicator、errorLabel 到控制器视图，并配置顶部工具栏。
    func assembleInterface() {
        guard let controller = context.controller,
              let readerView = context.readerView else { return }

        controller.view.backgroundColor = context.configuration.theme.contentBackgroundColor
        setupReaderView(readerView, in: controller.view)
        setupLoadingIndicator(controller.loadingIndicator, in: controller.view)
        setupErrorLabel(controller.errorLabel, in: controller.view)
        controller.delegate?.epubReader(controller, configureTopToolView: controller.topToolView)
        #if DEBUG
        print("[ReadViewDemo] assembleInterface: dataSource=\(readerView.dataSource != nil ? "set" : "nil"), numberOfPages=\(readerView.numberOfPages())")
        #endif
    }

    /// 外部纯文本图书启动时，加载已保存的书签、高亮和阅读位置，完成分页收尾。
    func finishExternalTextBookLaunchIfNeeded() {
        guard let runtime = context.runtime,
              let controller = context.controller,
              context.isExternalTextBook else {
            return
        }

        let restoreLocation = context.currentBookIdentifier.flatMap { context.persistence?.loadLocation(for: $0) }
        if let id = context.currentBookIdentifier {
            context.activeBookmarks = context.persistence?.loadBookmarks(for: id) ?? []
            context.activeHighlights = context.persistence?.loadHighlights(for: id) ?? []
        }

        if let textBook = controller.textBook {
            #if DEBUG
            print("[ReadViewDemo] finishExternalTextBook: applying textBook with \(textBook.pages.count) pages")
            #endif
            runtime.applyTextBook(textBook, restoreLocation: restoreLocation)
            #if DEBUG
            print("[ReadViewDemo] finishExternalTextBook: after applyTextBook, numberOfPages=\(context.readerView?.numberOfPages() ?? -1)")
            #endif
        } else {
            runtime.finishPagination(restoreLocation: restoreLocation)
        }
    }

    private func setupReaderView(_ readerView: RDReaderView, in containerView: UIView) {
        readerView.dataSource = context.controller
        readerView.delegate = context.controller
        readerView.translatesAutoresizingMaskIntoConstraints = false
        containerView.addSubview(readerView)
        NSLayoutConstraint.activate([
            readerView.leadingAnchor.constraint(equalTo: containerView.leadingAnchor),
            readerView.trailingAnchor.constraint(equalTo: containerView.trailingAnchor),
            readerView.topAnchor.constraint(equalTo: containerView.topAnchor),
            readerView.bottomAnchor.constraint(equalTo: containerView.bottomAnchor)
        ])

        readerView.register(contentView: RDEPUBTextContentView.self, contentViewWithReuseIdentifier: NSStringFromClass(RDEPUBTextContentView.self))
        readerView.register(contentView: RDEPUBWebContentView.self, contentViewWithReuseIdentifier: NSStringFromClass(RDEPUBWebContentView.self))
        context.controller?.applyReaderViewConfiguration()
    }

    private func setupLoadingIndicator(_ loadingIndicator: UIActivityIndicatorView, in containerView: UIView) {
        loadingIndicator.hidesWhenStopped = true
        loadingIndicator.translatesAutoresizingMaskIntoConstraints = false
        containerView.addSubview(loadingIndicator)
        NSLayoutConstraint.activate([
            loadingIndicator.centerXAnchor.constraint(equalTo: containerView.centerXAnchor),
            loadingIndicator.centerYAnchor.constraint(equalTo: containerView.centerYAnchor)
        ])
    }

    private func setupErrorLabel(_ errorLabel: UILabel, in containerView: UIView) {
        errorLabel.translatesAutoresizingMaskIntoConstraints = false
        containerView.addSubview(errorLabel)
        NSLayoutConstraint.activate([
            errorLabel.leadingAnchor.constraint(equalTo: containerView.leadingAnchor, constant: 24),
            errorLabel.trailingAnchor.constraint(equalTo: containerView.trailingAnchor, constant: -24),
            errorLabel.centerYAnchor.constraint(equalTo: containerView.centerYAnchor)
        ])
    }
}