import Foundation

/// Der komplette Weg einer einzelnen Datei: Dateiname parsen, bei Erfolg den
/// Projekt-Unterordner anlegen, das unveränderte 9:16-Original ablegen und
/// die 4:5-Fassung rendern. UI-frei und von `droptwo-cli` wie von der App
/// gemeinsam genutzt, damit beide garantiert dasselbe tun.
public enum ConversionPipeline {
    public struct Options {
        public var cropOptions: CropEngine.Options
        /// true = das unveränderte 9:16-Original wird zusätzlich in den
        /// Projektordner kopiert (README: "Dort landen beide Fassungen").
        public var copyOriginal: Bool

        public init(cropOptions: CropEngine.Options = CropEngine.Options(), copyOriginal: Bool = true) {
            self.cropOptions = cropOptions
            self.copyOriginal = copyOriginal
        }
    }

    public enum Outcome {
        case skipped(fileName: String, reason: SkipReason)
        case rejected(fileName: String, reason: RejectionReason)
        case succeeded(Success)
        case failed(fileName: String, error: Error)
    }

    public struct Success {
        public let originalDestination: URL
        public let croppedDestination: URL
        public let sourceInfo: VideoInfo
        public let croppedInfo: VideoInfo
    }

    public static func process(
        sourceURL: URL,
        outputRootDirectory: URL,
        options: Options = Options(),
        progress: ((Double) -> Void)? = nil
    ) async -> Outcome {
        let fileName = sourceURL.lastPathComponent
        let result = FileNameParser.parse(fileName)

        switch result.outcome {
        case .skipped(let reason):
            return .skipped(fileName: fileName, reason: reason)
        case .rejected(let reason):
            return .rejected(fileName: fileName, reason: reason)
        case .parsed(let parsed):
            do {
                let success = try await convert(sourceURL: sourceURL, parsed: parsed, outputRootDirectory: outputRootDirectory, options: options, progress: progress)
                return .succeeded(success)
            } catch {
                return .failed(fileName: fileName, error: error)
            }
        }
    }

    private static func convert(
        sourceURL: URL,
        parsed: ParsedFileName,
        outputRootDirectory: URL,
        options: Options,
        progress: ((Double) -> Void)?
    ) async throws -> Success {
        let projectDirectory = outputRootDirectory.appendingPathComponent(parsed.projectName, isDirectory: true)
        try FileManager.default.createDirectory(at: projectDirectory, withIntermediateDirectories: true)

        var originalDestination = sourceURL
        if options.copyOriginal {
            let destination = projectDirectory.appendingPathComponent(parsed.originalFileName)
            if !FileManager.default.fileExists(atPath: destination.path) {
                try FileManager.default.copyItem(at: sourceURL, to: destination)
            }
            originalDestination = destination
        }

        let sourceInfo = try await VideoInspector.inspect(sourceURL)

        let croppedFileName = mp4FileName(from: parsed.targetFileName)
        let croppedDestination = projectDirectory.appendingPathComponent(croppedFileName)
        try await CropEngine.crop(
            sourceURL: sourceURL,
            destinationURL: croppedDestination,
            options: options.cropOptions,
            progress: progress
        )
        let croppedInfo = try await VideoInspector.inspect(croppedDestination)

        return Success(
            originalDestination: originalDestination,
            croppedDestination: croppedDestination,
            sourceInfo: sourceInfo,
            croppedInfo: croppedInfo
        )
    }

    /// Zielformat ist fest MP4 (siehe CropEngine) — die Endung aus dem
    /// geparsten Dateinamen wird dafür überschrieben, nicht übernommen.
    private static func mp4FileName(from fileName: String) -> String {
        URL(fileURLWithPath: fileName).deletingPathExtension().appendingPathExtension("mp4").lastPathComponent
    }
}