import UIKit

// MARK: - 文本渲染引擎

/// EPUB 文本渲染引擎枚举
/// 定义了当前支持的文本渲染方式，未来可扩展为多引擎选择
public enum RDEPUBTextRenderingEngine: Equatable {
    /// 基于 DTCoreText 的渲染引擎，将 HTML/CSS 转换为 NSAttributedString
    case dtCoreText
}

// MARK: - 阅读器配置

/// EPUB 阅读器的完整配置结构体
/// 作为 EPUBUI 层的入口配置，控制阅读器的外观、行为和功能开关
/// 调用方在创建 RDEPUBReaderController 前可自定义此配置
public struct RDEPUBReaderConfiguration: Equatable {
    // MARK: 阅读排版参数

    /// 正文字号（单位：pt），默认 15
    public var fontSize: CGFloat
    /// 行距倍数，默认 1.6（即行距为字号的 1.6 倍）
    public var lineHeightMultiple: CGFloat
    /// 栏数，默认单栏
    public var numberOfColumns: Int
    /// 栏间距，默认 20pt
    public var columnGap: CGFloat
    /// 翻页显示模式：.pageCurl（仿真翻页）或 .scroll（滚动阅读）
    public var displayType: RDReaderView.DisplayType
    /// 横屏时是否启用双页显示，默认开启
    public var landscapeDualPageEnabled: Bool

    // MARK: UI 功能开关

    /// 是否显示目录入口，默认开启
    public var showsTableOfContents: Bool
    /// 是否允许文本高亮功能，默认开启
    public var allowsHighlights: Bool
    /// 是否显示设置面板入口，默认开启
    public var showsSettingsPanel: Bool

    // MARK: 内容内边距

    /// 流式排版（reflowable）内容的内边距，上下 40pt、左右 16pt
    public var reflowableContentInsets: UIEdgeInsets
    /// 固定布局（fixed layout）内容的内边距，默认为零
    public var fixedContentInset: UIEdgeInsets

    // MARK: 主题与布局

    /// 当前阅读主题（浅色/深色/护眼等），默认 .light
    public var theme: RDEPUBReaderTheme
    /// 固定布局的适配模式：按页适配或按宽度适配
    public var fixedLayoutFit: RDEPUBFixedLayoutFit
    /// 固定布局的跨页模式：自动/单页/双页
    public var fixedLayoutSpreadMode: RDEPUBFixedLayoutSpreadMode
    /// 文本渲染引擎，默认使用 DTCoreText
    public var textRenderingEngine: RDEPUBTextRenderingEngine

    // MARK: 初始化

    /// 创建阅读器配置，所有参数均提供合理的默认值
    /// - Parameters:
    ///   - fontSize: 正文字号，默认 15pt
    ///   - lineHeightMultiple: 行距倍数，默认 1.6
    ///   - displayType: 翻页模式，默认 .pageCurl
    ///   - landscapeDualPageEnabled: 横屏双页，默认 true
    ///   - showsTableOfContents: 显示目录入口，默认 true
    ///   - allowsHighlights: 允许高亮，默认 true
    ///   - showsSettingsPanel: 显示设置面板，默认 true
    ///   - reflowableContentInsets: 流式排版内边距
    ///   - fixedContentInset: 固定布局内边距
    ///   - theme: 阅读主题，默认 .light
    ///   - fixedLayoutFit: 固定布局适配模式
    ///   - fixedLayoutSpreadMode: 固定布局跨页模式
    ///   - textRenderingEngine: 文本渲染引擎
    public init(
        fontSize: CGFloat = 15,
        lineHeightMultiple: CGFloat = 1.6,
        numberOfColumns: Int = 1,
        columnGap: CGFloat = 20,
        displayType: RDReaderView.DisplayType = .pageCurl,
        landscapeDualPageEnabled: Bool = true,
        showsTableOfContents: Bool = true,
        allowsHighlights: Bool = true,
        showsSettingsPanel: Bool = true,
        reflowableContentInsets: UIEdgeInsets = UIEdgeInsets(top: 40, left: 16, bottom: 40, right: 16),
        fixedContentInset: UIEdgeInsets = .zero,
        theme: RDEPUBReaderTheme = .light,
        fixedLayoutFit: RDEPUBFixedLayoutFit = .page,
        fixedLayoutSpreadMode: RDEPUBFixedLayoutSpreadMode = .automatic,
        textRenderingEngine: RDEPUBTextRenderingEngine = .dtCoreText
    ) {
        self.fontSize = fontSize
        self.lineHeightMultiple = lineHeightMultiple
        self.numberOfColumns = max(1, numberOfColumns)
        self.columnGap = max(0, columnGap)
        self.displayType = displayType
        self.landscapeDualPageEnabled = landscapeDualPageEnabled
        self.showsTableOfContents = showsTableOfContents
        self.allowsHighlights = allowsHighlights
        self.showsSettingsPanel = showsSettingsPanel
        self.reflowableContentInsets = reflowableContentInsets
        self.fixedContentInset = fixedContentInset
        self.theme = theme
        self.fixedLayoutFit = fixedLayoutFit
        self.fixedLayoutSpreadMode = fixedLayoutSpreadMode
        self.textRenderingEngine = textRenderingEngine
    }

    /// 默认配置实例，使用所有参数的默认值
    public static let `default` = RDEPUBReaderConfiguration()
}

// MARK: - 配置转换

extension RDEPUBReaderConfiguration {
    /// 将用户可见的配置转换为底层排版引擎所需的 RDEPUBPreferences
    /// - Returns: 排版偏好设置实例，供 Core 层的渲染管道使用
    func makePreferences() -> RDEPUBPreferences {
        RDEPUBPreferences(
            fontSize: fontSize,
            lineHeightMultiple: lineHeightMultiple,
            reflowableContentInsets: reflowableContentInsets,
            fixedContentInset: fixedContentInset,
            numberOfColumns: numberOfColumns,
            columnGap: columnGap,
            themeBackgroundColor: theme.themeBackgroundColorCSS,
            themeTextColor: theme.themeTextColorCSS,
            fixedBackgroundColor: theme.themeBackgroundColorCSS,
            fixedLayoutFit: fixedLayoutFit,
            fixedLayoutSpreadMode: fixedLayoutSpreadMode
        )
    }
}