import Foundation

/// Protocol for all DAW export formats.
protocol DAWExporter {
    /// Unique identifier for this export format.
    static var formatID: String { get }

    /// Display name for UI.
    static var formatName: String { get }

    /// File extension(s) for the export.
    static var fileExtension: String { get }

    /// Export a playlist to the specified URL.
    static func export(playlist: Playlist, to url: URL, options: ExportOptions) throws
}

/// Options for DAW export.
struct ExportOptions {
    /// Whether to copy audio files alongside the session file.
    var copyAudioFiles: Bool = true

    /// Target sample rate for the session (nil = use original).
    var targetSampleRate: Double? = nil

    /// Target bit depth for the session.
    var targetBitDepth: Int = 24

    /// Include cue points as markers in the DAW session.
    var includeCuePoints: Bool = true

    /// Include crossfade information.
    var includeCrossfades: Bool = true

    /// Base directory for relative audio file paths.
    var audioFilesRelativePath: String = "Audio Files"

    /// Template for renaming copied files. Nil = keep original filenames.
    var fileNameTemplate: String? = nil

    /// Downloaded cloud track files, mapped by Track.id to local temp URL.
    /// Used by the export pipeline to include cloud tracks that were downloaded before export.
    var downloadedFiles: [UUID: URL] = [:]

    static let `default` = ExportOptions()

    /// Returns the effective file URL for a track, considering downloaded cloud files.
    func effectiveFileURL(for track: Track) -> URL? {
        if let downloaded = downloadedFiles[track.id] {
            return downloaded
        }
        guard track.hasLocalFile else { return nil }
        return track.fileURL
    }
}

/// Central exporter that dispatches to format-specific exporters.
struct MixExporter {

    enum ExportFormat: String, CaseIterable, Identifiable {
        case audition    = "audition"
        case cueSheet    = "cue"
        case dawProject  = "dawproject"
        case edl         = "edl"
        case m3u         = "m3u"

        var id: String { rawValue }

        var name: String {
            switch self {
            case .audition:   return "Adobe Audition Session"
            case .cueSheet:   return "Cue Sheet (.cue)"
            case .dawProject: return "DAWproject (Open Standard)"
            case .edl:        return "Edit Decision List (EDL)"
            case .m3u:        return "M3U Playlist"
            }
        }

        var fileExtension: String {
            switch self {
            case .audition:   return "sesx"
            case .cueSheet:   return "cue"
            case .dawProject: return "dawproject"
            case .edl:        return "edl"
            case .m3u:        return "m3u"
            }
        }

        var description: String {
            switch self {
            case .audition:
                return "Adobe Audition multitrack session with markers and crossfades"
            case .cueSheet:
                return "Standard cue sheet format, compatible with many audio tools"
            case .dawProject:
                return "Open DAW exchange format (Bitwig, PreSonus, REAPER)"
            case .edl:
                return "CMX 3600 Edit Decision List for professional DAWs"
            case .m3u:
                return "Simple playlist format for basic file list export"
            }
        }
    }

    /// Export a playlist in the specified format.
    static func export(
        playlist: Playlist,
        format: ExportFormat,
        to url: URL,
        options: ExportOptions = .default
    ) throws {
        // Wrap output in a parent folder named after the session file
        let baseName = url.deletingPathExtension().lastPathComponent
        let wrapperDir = url.deletingLastPathComponent().appendingPathComponent(baseName, isDirectory: true)
        try FileManager.default.createDirectory(at: wrapperDir, withIntermediateDirectories: true)
        let wrappedURL = wrapperDir.appendingPathComponent(url.lastPathComponent)

        // Copy audio files if requested
        if options.copyAudioFiles {
            let audioDir = wrapperDir
                .appendingPathComponent(options.audioFilesRelativePath)
            let entries = playlist.sortedEntries
            try copyAudioFiles(entries: entries, to: audioDir, options: options)
        }

        switch format {
        case .audition:   try AuditionExporter.export(playlist: playlist, to: wrappedURL, options: options)
        case .cueSheet:   try CueSheetExporter.export(playlist: playlist, to: wrappedURL, options: options)
        case .dawProject: try DAWProjectExporter.export(playlist: playlist, to: wrappedURL, options: options)
        case .edl:        try EDLExporter.export(playlist: playlist, to: wrappedURL, options: options)
        case .m3u:        try M3UExporter.export(playlist: playlist, to: wrappedURL, options: options)
        }
    }

    private static func copyAudioFiles(entries: [PlaylistEntry], to directory: URL, options: ExportOptions) throws {
        let fm = FileManager.default
        try fm.createDirectory(at: directory, withIntermediateDirectories: true)

        let totalTracks = entries.count

        for (index, entry) in entries.enumerated() {
            guard let track = entry.track,
                  let source = options.effectiveFileURL(for: track) else { continue }
            let ext = source.pathExtension

            let destName: String
            if let template = options.fileNameTemplate {
                let baseName = FileNameTemplate.generate(
                    template: template,
                    track: track,
                    playlistIndex: index,
                    totalTracks: totalTracks
                )
                destName = "\(baseName).\(ext)"
            } else {
                destName = source.lastPathComponent
            }

            let dest = directory.appendingPathComponent(destName)
            if !fm.fileExists(atPath: dest.path) {
                try fm.copyItem(at: source, to: dest)
            }
        }
    }
}