namespace ytLive.Services;

/// <summary>
/// Pure filename logic for local recordings (TASK 18). The user-requested naming
/// is <c>ty-yyyymmdd-hhmm-fff-hh2mm2.mp4</c>: <c>ty</c> is the brand marker, the first
/// <c>hhmm</c> is the hour+minute the recording STARTED (saved), <c>fff</c> is
/// milliseconds on the same start timestamp, and the last <c>hh2mm2</c> is the
/// hour+minute of the recording's LENGTH. Length is only known when recording ends,
/// so the file is created with a <c>0000</c> length and renamed on stop (see
/// <see cref="FinalizeFileName"/>).
/// <para>The <c>fff</c> exists so two instances started in the same minute cannot
/// compute the same path — the dev multi-instance use case (record one instance
/// with the other) would otherwise have both ffmpeg processes writing one file.
/// Both names derive from the same <c>_recordStartTime</c>, so the segment survives
/// the rename.</para>
/// </summary>
public static class RecordingFile
{
    /// <summary>A start placeholder — the length is filled in on stop.</summary>
    public const string StartLengthSuffix = "0000";

    public static string BuildStartName(DateTime start)
        => $"ty-{start:yyyyMMdd}-{start:HHmm}-{start:fff}-{StartLengthSuffix}";

    /// <summary>Final name with the real recording length (fractional hour+minute),
    /// e.g. 75 minutes → <c>ty-20260829-1405-000-0115.mp4</c>.</summary>
    public static string BuildFinalName(DateTime start, TimeSpan length)
    {
        var hh2 = (int)length.TotalHours;
        var mm2 = length.Minutes;
        return $"ty-{start:yyyyMMdd}-{start:HHmm}-{start:fff}-{hh2:00}{mm2:00}";
    }
}