mixboard/Sources/Export/M3UExporter.swift

import Foundation

/// Exports a playlist as an M3U/M3U8 playlist file.
/// M3U is a simple, widely-supported playlist format.
struct M3UExporter: DAWExporter {
    static let formatID = "m3u"
    static let formatName = "M3U Playlist"
    static let fileExtension = "m3u"

    static func export(playlist: Playlist, to url: URL, options: ExportOptions) throws {
        let entries = playlist.sortedEntries
        var lines: [String] = []

        // Extended M3U header
        lines.append("#EXTM3U")
        lines.append("#PLAYLIST:\(playlist.name)")
        lines.append("")

        for entry in entries {
            guard let track = entry.track,
                  let fileURL = options.effectiveFileURL(for: track) else { continue }

            let duration = Int(track.duration)
            let displayTitle: String
            if track.artist.isEmpty {
                displayTitle = track.title
            } else {
                displayTitle = "\(track.artist) - \(track.title)"
            }

            // EXTINF line: duration, artist - title
            lines.append("#EXTINF:\(duration),\(displayTitle)")

            // Additional metadata as comments
            if let bpm = track.bpm {
                lines.append("#EXTBPM:\(String(format: "%.1f", bpm))")
            }
            if let key = track.musicalKey {
                lines.append("#EXTKEY:\(key)")
            }

            // File path (relative if copying, absolute otherwise)
            if options.copyAudioFiles {
                lines.append("\(options.audioFilesRelativePath)/\(fileURL.lastPathComponent)")
            } else {
                lines.append(fileURL.path)
            }

            lines.append("")
        }

        let content = lines.joined(separator: "\n")
        try content.write(to: url, atomically: true, encoding: .utf8)
    }
}