// RDEPUBParser+Archive.swift
// EPUB 归档解压与 container.xml 解析
// 负责将 EPUB ZIP 文件解压到缓存目录（~/Library/Caches/ssreaderview-epub/），
// 并解析 META-INF/container.xml 获取 OPF 文件路径。

import Foundation
import ZIPFoundation

extension RDEPUBParser {
    /// 解析 container.xml，提取 OPF（Package Document）的相对路径
    /// - Parameter containerURL: container.xml 的文件路径
    /// - Returns: OPF 文件的相对路径（如 "OEBPS/content.opf"）
    func parseContainerRootFile(at containerURL: URL) throws -> String {
        guard let parser = XMLParser(contentsOf: containerURL) else {
            throw RDEPUBParserError.invalidXML(containerURL)
        }

        let delegate = ContainerXMLParserDelegate()
        parser.shouldProcessNamespaces = false
        parser.delegate = delegate

        guard parser.parse() else {
            throw parser.parserError ?? RDEPUBParserError.invalidXML(containerURL)
        }

        guard let rootFilePath = delegate.rootFilePath, !rootFilePath.isEmpty else {
            throw RDEPUBParserError.missingRootFile
        }

        return rootFilePath
    }

    /// 解压 EPUB ZIP 文件到缓存目录（幂等：已存在则跳过）
    /// 目录名由 slug + 文件大小 + 修改时间戳组成，避免冲突
    /// - Parameter epubURL: EPUB 文件路径
    /// - Returns: 解压目标目录 URL
    func extractArchiveIfNeeded(epubURL: URL) throws -> URL {
        let fileManager = FileManager.default
        let extractionURL = temporaryExtractionDirectory(for: epubURL)

        if fileManager.fileExists(atPath: extractionURL.path) {
            return extractionURL
        }

        guard let archive = Archive(url: epubURL, accessMode: .read) else {
            throw RDEPUBParserError.archiveOpenFailed(epubURL)
        }

        try fileManager.createDirectory(at: extractionURL, withIntermediateDirectories: true)

        for entry in archive {
            guard let destinationURL = validatedExtractionDestination(for: entry.path, extractionRoot: extractionURL) else {
                throw RDEPUBParserError.invalidArchiveEntryPath(entry.path)
            }
            switch entry.type {
            case .directory:
                try fileManager.createDirectory(at: destinationURL, withIntermediateDirectories: true)
            case .file:
                try fileManager.createDirectory(at: destinationURL.deletingLastPathComponent(), withIntermediateDirectories: true)
                _ = try archive.extract(entry, to: destinationURL)
            case .symlink:
                continue
            }
        }

        return extractionURL
    }

    /// 校验归档条目路径，防止路径穿越攻击
    /// - Parameters:
    ///   - entryPath: 归档中的原始条目路径
    ///   - extractionRoot: 解压根目录
    /// - Returns: 校验通过的目标 URL，非法路径返回 nil
    private func validatedExtractionDestination(for entryPath: String, extractionRoot: URL) -> URL? {
        // 拒绝绝对路径
        if entryPath.hasPrefix("/") {
            return nil
        }
        // 拒绝包含 .. 的路径段
        let components = entryPath.split(separator: "/", omittingEmptySubsequences: true)
        if components.contains(where: { $0 == ".." }) {
            return nil
        }
        let destinationURL = extractionRoot.appendingPathComponent(entryPath)
        let standardizedDest = destinationURL.standardizedFileURL.path
        let standardizedRoot = extractionRoot.standardizedFileURL.path
        // 确保最终路径位于解压根目录下
        guard standardizedDest.hasPrefix(standardizedRoot) else {
            return nil
        }
        return destinationURL
    }

    /// 计算 EPUB 的临时解压目录路径
    /// 路径格式：~/Library/Caches/ssreaderview-epub/{slug}-{fileSize}-{modifiedTimestamp}/
    func temporaryExtractionDirectory(for epubURL: URL) -> URL {
        let baseURL = FileManager.default.urls(for: .cachesDirectory, in: .userDomainMask).first?
            .appendingPathComponent("ssreaderview-epub", isDirectory: true)
            ?? FileManager.default.temporaryDirectory.appendingPathComponent("ssreaderview-epub", isDirectory: true)
        let fileAttributes = try? FileManager.default.attributesOfItem(atPath: epubURL.path)
        let fileSize = (fileAttributes?[.size] as? NSNumber)?.stringValue ?? "0"
        let modifiedAt = (fileAttributes?[.modificationDate] as? Date)?.timeIntervalSince1970 ?? 0
        let slug = epubURL.deletingPathExtension().lastPathComponent
            .replacingOccurrences(of: " ", with: "-")
        let signature = String(format: "%.0f", modifiedAt)
        return baseURL.appendingPathComponent("\(slug)-\(fileSize)-\(signature)", isDirectory: true)
    }

    /// 重置解析器状态（清除解压路径和出版物数据）
    func reset() {
        extractionRootURL = nil
        opfURL = nil
        resetPublicationState()
    }

    /// 重置出版物相关状态（metadata、manifest、spine、目录）
    func resetPublicationState() {
        metadata = RDEPUBMetadata()
        manifest = [:]
        spine = []
        tableOfContents = []
    }
}

/// container.xml 的 SAX 解析代理，提取 <rootfile> 元素的 full-path 属性
private final class ContainerXMLParserDelegate: NSObject, XMLParserDelegate {
    /// 解析得到的 OPF 文件相对路径
    private(set) var rootFilePath: String?

    func parser(
        _ parser: XMLParser,
        didStartElement elementName: String,
        namespaceURI: String?,
        qualifiedName qName: String?,
        attributes attributeDict: [String: String] = [:]
    ) {
        let name = XMLName.localName(from: qName ?? elementName)
        guard name == "rootfile", rootFilePath == nil else {
            return
        }
        rootFilePath = attributeDict["full-path"]?.trimmingCharacters(in: .whitespacesAndNewlines)
    }
}