namespace Volcanic.AgenticCore.Extensions.Scheduler;

/// <summary>
/// Zone ids for display and <c>TZ</c>. Mirrors the core's <c>Volcanic.AgenticCore.Hosting.TimeZoneIds</c> (the extension
/// references only the Abstractions); keep the two in step.
/// </summary>
internal static class ZoneNames
{
    /// <summary>
    /// The IANA id (converting a Windows id), or null when there is none that resolves back to a system zone (an unnamed
    /// <c>Local</c> zone: <c>TZ=Local</c> would run the script in UTC). Same rule as <c>TimeZoneIds.ToIana</c>.
    /// </summary>
    public static string? Iana(TimeZoneInfo zone)
    {
        if (string.Equals(zone.Id, "Local", StringComparison.OrdinalIgnoreCase)) return null;
        var id = zone.HasIanaId ? zone.Id : TimeZoneInfo.TryConvertWindowsIdToIanaId(zone.Id, out var iana) ? iana : null;
        return id is not null && TimeZoneInfo.TryFindSystemTimeZoneById(id, out _) ? id : null;
    }

    /// <summary>The IANA id when there is one, else the zone's own id (<c>TimeZoneIds.Name</c>).</summary>
    public static string Name(TimeZoneInfo zone) => Iana(zone) ?? zone.Id;
}