import Foundation
import ZIPFoundation

extension RDEPUBParser {

    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
    }

    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
    }

    private func validatedExtractionDestination(for entryPath: String, extractionRoot: URL) -> URL? {

        if entryPath.hasPrefix("/") {
            return nil
        }

        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

        guard standardizedDest.hasPrefix(standardizedRoot) else {
            return nil
        }
        return destinationURL
    }

    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)
    }

    func reset() {
        extractionRootURL = nil
        opfURL = nil
        resetPublicationState()
    }

    func resetPublicationState() {
        metadata = RDEPUBMetadata()
        manifest = [:]
        spine = []
        tableOfContents = []
    }
}

private final class ContainerXMLParserDelegate: NSObject, XMLParserDelegate {

    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)
    }
}