//
//  RDEPUBReadingModels.swift
//  RDReaderView
//
//  EPUBCore 层阅读会话相关数据模型定义文件。
//  包含阅读位置（Location）、视口（Viewport）、阅读上下文（ReadingContext）、
//  文本选择（Selection）、高亮（Highlight）、书签（Bookmark）、
//  章节信息（ChapterInfo）、页面模型（Page）、固定版式 Spread 模型等。
//  这些模型由 RDEPUBReadingSession 管理，贯穿整个阅读生命周期。
//

import Foundation

/// 阅读位置模型，EPUB 是可重排内容，使用 href + progression 而非页号来定位
/// progression 取值 [0, 1]，表示当前视口在章节中的相对位置
public struct RDEPUBLocation: Codable, Equatable {
    /// 书籍唯一标识符，用于隔离不同书的阅读进度
    public var bookIdentifier: String?
    /// OPF 相对路径，对应 spine 中的资源文件
    public var href: String
    /// 视口起始位置在章节中的相对进度 [0, 1]
    public var progression: Double
    /// 视口末尾位置在章节中的相对进度 [0, 1]（可选）
    public var lastProgression: Double?
    /// 锚点标识符（如 #section1），用于精确跳转
    public var fragment: String?
    /// 文本范围锚点（用于文本 EPUB 的高亮定位）
    public var rangeAnchor: RDEPUBTextRangeAnchor?

    public init(
        bookIdentifier: String? = nil,
        href: String,
        progression: Double,
        lastProgression: Double? = nil,
        fragment: String? = nil,
        rangeAnchor: RDEPUBTextRangeAnchor? = nil
    ) {
        self.bookIdentifier = bookIdentifier
        self.href = href
        self.progression = Self.clamp(progression)
        self.lastProgression = lastProgression.map(Self.clamp)
        self.fragment = fragment?.nilIfEmpty
        self.rangeAnchor = rangeAnchor
    }

    /// 导航用的中间进度值，取 progression 和 lastProgression 的中点
    /// 用于在字号/横竖屏变化后估算最接近的页号
    public var navigationProgression: Double {
        let end = lastProgression ?? progression
        if end.isNaN || end.isInfinite {
            return progression
        }
        return Self.clamp((progression + end) / 2.0)
    }

    /// 将进度值限制在 [0, 1] 范围内，防止越界
    private static func clamp(_ value: Double) -> Double {
        guard value.isFinite else { return 0 }
        return min(1, max(0, value))
    }
}

/// 视口中的单个资源信息，表示当前屏幕可见区域覆盖的某个 spine 资源
public struct RDEPUBViewportResource: Codable, Equatable {
    /// 资源路径（相对于 OPF 目录）
    public var href: String
    /// 对应的 spine 索引
    public var spineIndex: Int
    /// 该资源在视口中的起始进度 [0, 1]
    public var progression: Double
    /// 该资源在视口中的结束进度 [0, 1]
    public var lastProgression: Double?
    /// 锚点标识符
    public var fragment: String?

    public init(
        href: String,
        spineIndex: Int,
        progression: Double,
        lastProgression: Double? = nil,
        fragment: String? = nil
    ) {
        self.href = href
        self.spineIndex = spineIndex
        self.progression = progression
        self.lastProgression = lastProgression
        self.fragment = fragment
    }
}

/// 视口模型，描述当前屏幕可见区域的完整状态
/// 可能跨越多个 spine 资源（如分栏布局时）
public struct RDEPUBViewport: Codable, Equatable {
    /// 当前视口覆盖的资源列表（可能有多个，如分栏或跨页场景）
    public var resources: [RDEPUBViewportResource]
    /// 当前可见的页码
    public var visiblePageNumber: Int
    /// 当前章节索引
    public var chapterIndex: Int?
    /// 是否为固定版式内容
    public var isFixedLayout: Bool

    public init(
        resources: [RDEPUBViewportResource],
        visiblePageNumber: Int,
        chapterIndex: Int? = nil,
        isFixedLayout: Bool
    ) {
        self.resources = resources
        self.visiblePageNumber = visiblePageNumber
        self.chapterIndex = chapterIndex
        self.isFixedLayout = isFixedLayout
    }
}

/// 阅读上下文，聚合了位置、视口和页码等完整阅读状态
/// 由 RDEPUBReadingSession 维护，是翻页容器层获取当前阅读状态的主要数据源
public struct RDEPUBReadingContext: Codable, Equatable {
    /// 当前阅读位置（href + progression）
    public var location: RDEPUBLocation
    /// 当前视口状态
    public var viewport: RDEPUBViewport
    /// 当前扁平页码（跨章节累计）
    public var pageNumber: Int
    /// 当前章节索引
    public var chapterIndex: Int?

    public init(
        location: RDEPUBLocation,
        viewport: RDEPUBViewport,
        pageNumber: Int,
        chapterIndex: Int? = nil
    ) {
        self.location = location
        self.viewport = viewport
        self.pageNumber = pageNumber
        self.chapterIndex = chapterIndex
    }
}

/// 文本选择模型，由 JS 桥接 ssReaderSelectionChanged 消息触发创建
public struct RDEPUBSelection: Codable, Equatable {
    /// 书籍标识符
    public var bookIdentifier: String?
    /// 选择发生的位置
    public var location: RDEPUBLocation
    /// 选中的文本内容
    public var text: String
    /// DOM Range 信息（JSON 序列化字符串，用于精确重建选区）
    public var rangeInfo: String?
    /// 选择创建时间
    public var createdAt: Date

    public init(
        bookIdentifier: String? = nil,
        location: RDEPUBLocation,
        text: String,
        rangeInfo: String? = nil,
        createdAt: Date = Date()
    ) {
        self.bookIdentifier = bookIdentifier
        self.location = location
        self.text = text
        self.rangeInfo = rangeInfo?.nilIfEmpty
        self.createdAt = createdAt
    }

    /// 判断是否为空选择（无文本或无范围信息）
    public var isEmpty: Bool {
        text.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty || rangeInfo?.isEmpty != false
    }
}

/// 高亮样式类型
/// - highlight: 背景色高亮
/// - underline: 下划线标记
public enum RDEPUBHighlightStyle: String, Codable {
    case highlight
    case underline
}

/// 标注菜单操作类型，用于用户长按选中文本后的操作选项
public enum RDEPUBAnnotationMenuAction: Equatable {
    case copy
    case highlight
    case annotate
}

/// 文本偏移范围信息，用于文本 EPUB 的高亮精确定位
/// 使用字符偏移量而非 DOM Range，适用于 DTCoreText 渲染的纯文本内容
public struct RDEPUBTextOffsetRangeInfo: Codable, Equatable {
    /// 类型标识符，固定为 "text-offset"
    public var kind: String
    /// 资源路径
    public var href: String
    /// 起始字符偏移量
    public var start: Int
    /// 结束字符偏移量
    public var end: Int

    /// 初始化文本偏移范围
    /// - Parameters:
    ///   - href: 资源路径
    ///   - start: 起始字符偏移量
    ///   - end: 结束字符偏移量
    public init(href: String, start: Int, end: Int) {
        self.kind = "text-offset"
        self.href = href
        self.start = start
        self.end = end
    }

    /// 转换为 NSRange（用于 NSAttributedString 操作）
    public var nsRange: NSRange? {
        guard end > start else { return nil }
        return NSRange(location: start, length: end - start)
    }

    /// 序列化为 JSON 字符串
    public func jsonString() -> String? {
        guard let data = try? JSONEncoder().encode(self) else { return nil }
        return String(data: data, encoding: .utf8)
    }

    /// 从 JSON 字符串反序列化，校验 kind 和范围有效性
    public static func decode(from string: String?) -> RDEPUBTextOffsetRangeInfo? {
        guard let string,
              let data = string.data(using: .utf8),
              let rangeInfo = try? JSONDecoder().decode(RDEPUBTextOffsetRangeInfo.self, from: data),
              rangeInfo.kind == "text-offset",
              rangeInfo.end > rangeInfo.start else {
            return nil
        }
        return rangeInfo
    }
}

/// 文本分页截断原因，描述为什么在当前位置分页
public enum RDEPUBTextPageBreakReason: String, Codable, Equatable {
    /// 章节自然结束
    case chapterEnd
    /// 达到帧容量限制
    case frameLimit
    /// 块级元素边界（如段落、标题）
    case blockBoundary
    /// 附件（图片等）边界
    case attachmentBoundary
    /// 语义边界（如列表、引用块）
    case semanticBoundary
}

/// 文本附件类型
public enum RDEPUBTextAttachmentKind: String, Codable, Equatable {
    /// 图片附件
    case image
    /// 通用附件
    case generic
}

/// 文本页元数据，记录分页时的上下文信息
/// 用于调试分页问题和优化分页质量
public struct RDEPUBTextPageMetadata: Codable, Equatable {
    /// 分页截断原因
    public var breakReason: RDEPUBTextPageBreakReason
    /// 本页覆盖的块级元素范围
    public var blockRange: NSRange?
    /// 本页包含的附件范围列表
    public var attachmentRanges: [NSRange]
    /// 附件类型列表
    public var attachmentKinds: [RDEPUBTextAttachmentKind]
    /// 块级元素类型列表
    public var blockKinds: [RDEPUBTextBlockKind]
    /// 语义提示信息
    public var semanticHints: [RDEPUBTextSemanticHint]
    /// 附件布局位置信息
    public var attachmentPlacements: [RDEPUBTextAttachmentPlacement]
    /// 本页末尾的 fragment ID（用于恢复位置）
    public var trailingFragmentID: String?
    /// 诊断信息列表（调试用）
    public var diagnostics: [String]

    public init(
        breakReason: RDEPUBTextPageBreakReason,
        blockRange: NSRange? = nil,
        attachmentRanges: [NSRange] = [],
        attachmentKinds: [RDEPUBTextAttachmentKind] = [],
        blockKinds: [RDEPUBTextBlockKind] = [],
        semanticHints: [RDEPUBTextSemanticHint] = [],
        attachmentPlacements: [RDEPUBTextAttachmentPlacement] = [],
        trailingFragmentID: String? = nil,
        diagnostics: [String] = []
    ) {
        self.breakReason = breakReason
        self.blockRange = blockRange
        self.attachmentRanges = attachmentRanges
        self.attachmentKinds = attachmentKinds
        self.blockKinds = blockKinds
        self.semanticHints = semanticHints
        self.attachmentPlacements = attachmentPlacements
        self.trailingFragmentID = trailingFragmentID
        self.diagnostics = diagnostics
    }
}

/// 高亮模型，表示用户在阅读中标记的文本片段
/// 支持 Web EPUB（DOM Range 定位）和文本 EPUB（字符偏移定位）两种模式
public struct RDEPUBHighlight: Codable, Equatable {
    /// 高亮唯一标识符
    public var id: String
    /// 书籍标识符
    public var bookIdentifier: String?
    /// 高亮发生的位置
    public var location: RDEPUBLocation
    /// 高亮的文本内容
    public var text: String
    /// 范围信息（Web EPUB 为 DOM Range JSON，文本 EPUB 为字符偏移 JSON）
    public var rangeInfo: String?
    /// 高亮样式（背景色高亮或下划线）
    public var style: RDEPUBHighlightStyle
    /// 高亮颜色（CSS 颜色值，如 "#F8E16C"）
    public var color: String
    /// 用户备注
    public var note: String?
    /// 创建时间
    public var createdAt: Date

    public init(
        id: String = UUID().uuidString,
        bookIdentifier: String? = nil,
        location: RDEPUBLocation,
        text: String,
        rangeInfo: String? = nil,
        style: RDEPUBHighlightStyle = .highlight,
        color: String = "#F8E16C",
        note: String? = nil,
        createdAt: Date = Date()
    ) {
        self.id = id
        self.bookIdentifier = bookIdentifier
        self.location = location
        self.text = text
        self.rangeInfo = rangeInfo?.nilIfEmpty
        self.style = style
        self.color = color
        self.note = note?.nilIfEmpty
        self.createdAt = createdAt
    }

    /// 是否包含用户备注
    public var hasNote: Bool {
        note?.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty == false
    }

    /// 编码键，用于 Codable 序列化/反序列化
    private enum CodingKeys: String, CodingKey {
        case id
        case bookIdentifier
        case location
        case text
        case rangeInfo
        case style
        case color
        case note
        case createdAt
    }

    /// 自定义解码器，兼容旧版本数据格式（缺失字段使用默认值）
    public init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        id = try container.decode(String.self, forKey: .id)
        bookIdentifier = try container.decodeIfPresent(String.self, forKey: .bookIdentifier)
        location = try container.decode(RDEPUBLocation.self, forKey: .location)
        text = try container.decode(String.self, forKey: .text)
        rangeInfo = try container.decodeIfPresent(String.self, forKey: .rangeInfo)?.nilIfEmpty
        if let rawStyle = try container.decodeIfPresent(String.self, forKey: .style),
           let decodedStyle = RDEPUBHighlightStyle(rawValue: rawStyle) {
            style = decodedStyle
        } else {
            style = .highlight
        }
        color = try container.decodeIfPresent(String.self, forKey: .color) ?? "#F8E16C"
        note = try container.decodeIfPresent(String.self, forKey: .note)?.nilIfEmpty
        createdAt = try container.decodeIfPresent(Date.self, forKey: .createdAt) ?? Date()
    }

    /// 自定义编码器
    public func encode(to encoder: Encoder) throws {
        var container = encoder.container(keyedBy: CodingKeys.self)
        try container.encode(id, forKey: .id)
        try container.encodeIfPresent(bookIdentifier, forKey: .bookIdentifier)
        try container.encode(location, forKey: .location)
        try container.encode(text, forKey: .text)
        try container.encodeIfPresent(rangeInfo, forKey: .rangeInfo)
        try container.encode(style, forKey: .style)
        try container.encode(color, forKey: .color)
        try container.encodeIfPresent(note, forKey: .note)
        try container.encode(createdAt, forKey: .createdAt)
    }
}

/// 书签模型，记录用户标记的阅读位置
public struct RDEPUBBookmark: Codable, Equatable {
    /// 书签唯一标识符
    public var id: String
    /// 书籍标识符
    public var bookIdentifier: String?
    /// 书签位置
    public var location: RDEPUBLocation
    /// 章节标题（用于书签列表展示）
    public var chapterTitle: String?
    /// 用户备注
    public var note: String?
    /// 创建时间
    public var createdAt: Date

    public init(
        id: String = UUID().uuidString,
        bookIdentifier: String? = nil,
        location: RDEPUBLocation,
        chapterTitle: String? = nil,
        note: String? = nil,
        createdAt: Date = Date()
    ) {
        self.id = id
        self.bookIdentifier = bookIdentifier
        self.location = location
        self.chapterTitle = chapterTitle?.nilIfEmpty
        self.note = note?.nilIfEmpty
        self.createdAt = createdAt
    }

    /// 是否包含用户备注
    public var hasNote: Bool {
        note?.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty == false
    }
}

/// 章节信息模型，描述单个章节的元数据
public struct EPUBChapterInfo: Codable, Equatable {
    /// 对应的 spine 索引
    public var spineIndex: Int
    /// 章节标题
    public var title: String
    /// 该章节的总页数
    public var pageCount: Int

    public init(spineIndex: Int, title: String, pageCount: Int) {
        self.spineIndex = spineIndex
        self.title = title
        self.pageCount = pageCount
    }
}

/// 页面模型，描述单页的完整信息
/// 由 RDEPUBReadingSession 根据分页结果构建，是翻页容器层的数据单元
public struct EPUBPage: Codable, Equatable {
    /// 对应的 spine 索引
    public var spineIndex: Int
    /// 章节索引（从 0 开始的章节序号）
    public var chapterIndex: Int
    /// 页在章节中的索引（从 0 开始）
    public var pageIndexInChapter: Int
    /// 该章节的总页数
    public var totalPagesInChapter: Int
    /// 章节标题
    public var chapterTitle: String
    /// 固定版式 Spread 数据（仅 fixed layout 书籍有值）
    public var fixedSpread: EPUBFixedSpread?

    public init(
        spineIndex: Int,
        chapterIndex: Int,
        pageIndexInChapter: Int,
        totalPagesInChapter: Int,
        chapterTitle: String,
        fixedSpread: EPUBFixedSpread?
    ) {
        self.spineIndex = spineIndex
        self.chapterIndex = chapterIndex
        self.pageIndexInChapter = pageIndexInChapter
        self.totalPagesInChapter = totalPagesInChapter
        self.chapterTitle = chapterTitle
        self.fixedSpread = fixedSpread
    }
}

/// 固定版式 Spread 中的单个资源
public struct EPUBFixedSpreadResource: Codable, Equatable {
    /// 对应的 spine 索引
    public var spineIndex: Int
    /// 资源路径
    public var href: String
    /// 资源标题
    public var title: String
    /// 在 spread 中的位置偏好
    public var pageSpread: RDEPUBPageSpread?

    public init(spineIndex: Int, href: String, title: String, pageSpread: RDEPUBPageSpread? = nil) {
        self.spineIndex = spineIndex
        self.href = href
        self.title = title
        self.pageSpread = pageSpread
    }
}

/// 固定版式 Spread（双页展开）模型
/// 将 1-2 个 spine 资源组合为一个显示单元
public struct EPUBFixedSpread: Codable, Equatable {
    /// 该 spread 包含的资源列表（通常 1-2 个）
    public var resources: [EPUBFixedSpreadResource]

    public init(resources: [EPUBFixedSpreadResource]) {
        self.resources = resources
    }

    /// 主资源（列表中的第一个），用于标识和定位
    public var primaryResource: EPUBFixedSpreadResource {
        resources.first ?? EPUBFixedSpreadResource(spineIndex: 0, href: "", title: "")
    }

    /// 判断指定 href 的资源是否属于此 spread
    /// - Parameters:
    ///   - normalizedHref: 标准化后的 href
    ///   - normalizer: href 标准化函数
    /// - Returns: 是否包含该资源
    public func contains(normalizedHref: String, normalizer: (String) -> String?) -> Bool {
        resources.contains { resource in
            normalizer(resource.href) == normalizedHref
        }
    }

    /// 根据 spine 列表和 spread 设置生成 Spread 数组
    /// 根据 pageSpread 属性（left/right/center）决定资源配对
    /// - Parameters:
    ///   - spine: spine 项列表
    ///   - spreadEnabled: 是否启用 spread 模式
    /// - Returns: spread 数组
    public static func makeSpreads(spine: [RDEPUBSpineItem], spreadEnabled: Bool) -> [EPUBFixedSpread] {
        let resources = spine.enumerated().map { index, item in
            EPUBFixedSpreadResource(
                spineIndex: index,
                href: item.href,
                title: item.title,
                pageSpread: item.pageSpread
            )
        }

        guard spreadEnabled, resources.count > 1 else {
            return resources.map { EPUBFixedSpread(resources: [$0]) }
        }

        var spreads: [EPUBFixedSpread] = []
        var cursor = 0

        while cursor < resources.count {
            let current = resources[cursor]

            guard cursor + 1 < resources.count else {
                spreads.append(EPUBFixedSpread(resources: [current]))
                break
            }

            let next = resources[cursor + 1]
            if shouldPair(current: current, next: next) {
                spreads.append(EPUBFixedSpread(resources: [current, next]))
                cursor += 2
            } else {
                spreads.append(EPUBFixedSpread(resources: [current]))
                cursor += 1
            }
        }

        return spreads
    }

    /// 便捷方法：从 parser 构建 spread
    public static func makeSpreads(parser: RDEPUBParser, spreadEnabled: Bool) -> [EPUBFixedSpread] {
        makeSpreads(spine: parser.spine, spreadEnabled: spreadEnabled)
    }

    /// 判断两个资源是否应该配对为一个 spread
    /// center 类型不参与配对，left+right 或 right+left 配对
    private static func shouldPair(current: EPUBFixedSpreadResource, next: EPUBFixedSpreadResource) -> Bool {
        if current.pageSpread == .center || next.pageSpread == .center {
            return false
        }

        switch (current.pageSpread, next.pageSpread) {
        case (.left, .right), (.right, .left):
            return true
        case (.left, .left), (.right, .right):
            return false
        default:
            return true
        }
    }
}

/// String 扩展：空字符串转为 nil，用于 Codable 容错处理
private extension String {
    /// 空白字符修剪后如果是空字符串则返回 nil
    var nilIfEmpty: String? {
        let trimmed = trimmingCharacters(in: .whitespacesAndNewlines)
        return trimmed.isEmpty ? nil : trimmed
    }
}