namespace Fitness_core_BE.Helpers
{
    // Every gym this runs for is Sri Lanka-based -- shared by SubscriptionRenewalJob (daily
    // trigger wake-up) and the Classes feature (converting a class's local StartTimeOfDay to
    // UTC per generated occurrence). Lifted out of SubscriptionRenewalJob rather than each
    // caller re-deriving it.
    public static class TimeZoneHelper
    {
        public static readonly TimeZoneInfo SriLanka = ResolveSriLankaTimeZone();

        private static TimeZoneInfo ResolveSriLankaTimeZone()
        {
            try
            {
                return TimeZoneInfo.FindSystemTimeZoneById("Sri Lanka Standard Time"); // Windows ID
            }
            catch (TimeZoneNotFoundException)
            {
                try
                {
                    return TimeZoneInfo.FindSystemTimeZoneById("Asia/Colombo"); // IANA ID (Linux/macOS)
                }
                catch (TimeZoneNotFoundException)
                {
                    // Neither ID resolved (e.g. no tzdata on the host) -- Sri Lanka has kept a
                    // fixed UTC+5:30 offset with no DST since 2006, so a custom fixed-offset
                    // zone is a safe fallback rather than failing the whole caller.
                    return TimeZoneInfo.CreateCustomTimeZone(
                        "Sri Lanka (fixed +05:30)", TimeSpan.FromMinutes(330), "Sri Lanka Time", "Sri Lanka Time");
                }
            }
        }
    }
}