mixboard/Sources/Export/CueSheetExporter.swift

import Foundation

/// Exports a playlist as a standard CUE sheet (.cue).
/// CUE sheets are widely supported by CD burning software, virtual CD drives,
/// and many audio tools including Audacity, foobar2000, and various DAWs.
struct CueSheetExporter: DAWExporter {
    static let formatID = "cue"
    static let formatName = "Cue Sheet"
    static let fileExtension = "cue"

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

        lines.append("REM Generated by MixBoard")
        lines.append("REM Date: \(ISO8601DateFormatter().string(from: Date()))")
        lines.append("TITLE \"\(playlist.name)\"")

        var timelinePosition: TimeInterval = 0

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

            let trackNumber = String(format: "%02d", index + 1)
            let fileName = fileURL.lastPathComponent
            let relativePath = "\(options.audioFilesRelativePath)/\(fileName)"

            lines.append("FILE \"\(relativePath)\" WAVE")
            lines.append("  TRACK \(trackNumber) AUDIO")
            lines.append("    TITLE \"\(track.title)\"")

            if !track.artist.isEmpty {
                lines.append("    PERFORMER \"\(track.artist)\"")
            }

            // INDEX 01 is the start time in MM:SS:FF format (frames = 1/75 second)
            let indexTime = formatCueTime(timelinePosition)
            lines.append("    INDEX 01 \(indexTime)")

            // Add cue points as INDEX entries
            if options.includeCuePoints {
                for (cpIndex, cuePoint) in track.cuePoints.sorted().enumerated() {
                    // INDEX 02+ for additional cue points
                    let cpTime = formatCueTime(timelinePosition + cuePoint.timestamp - entry.startOffset)
                    lines.append("    REM CUE \(cuePoint.name.isEmpty ? cuePoint.type.rawValue : cuePoint.name)")
                    if cpIndex < 98 { // CUE format supports INDEX 00-99
                        lines.append("    INDEX \(String(format: "%02d", cpIndex + 2)) \(cpTime)")
                    }
                }
            }

            // Add BPM as a remark
            if let bpm = track.bpm {
                lines.append("    REM BPM \(String(format: "%.1f", bpm))")
            }
            if let key = track.musicalKey {
                lines.append("    REM KEY \(key)")
            }

            timelinePosition += entry.effectiveDuration
            if index + 1 < entries.count {
                timelinePosition -= entries[index + 1].crossfadeDuration
            }
        }

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

    // MARK: - CUE Time Format

    /// Convert seconds to CUE time format MM:SS:FF where FF = frames (1/75 second).
    private static func formatCueTime(_ seconds: TimeInterval) -> String {
        let totalSeconds = max(0, seconds)
        let minutes = Int(totalSeconds) / 60
        let secs = Int(totalSeconds) % 60
        let frames = Int((totalSeconds - Double(Int(totalSeconds))) * 75)
        return String(format: "%02d:%02d:%02d", minutes, secs, frames)
    }
}