using System;
using System.Globalization;

namespace URLNotesGrabberCORE
{
    /// <summary>
    /// The single format for Posts.PostDate: "yyyy-MM-dd HH:mm:ss GMT", which is what the
    /// Tumblr API sends and what nearly every row holds. Text-file exports can carry the
    /// RFC 1123 form ("Fri, 14 Feb 2025 15:20:09 GMT") instead, which as text sorts on its
    /// weekday name and falls outside every --fromDate/--toDate range comparison.
    ///
    /// Every path that writes PostDate routes through <see cref="Normalize"/>. Only the RFC 1123
    /// form is rewritten; anything else, including the "." no-change sentinel, passes through.
    /// </summary>
    public static class PostDates
    {
        public static string? Normalize(string? value)
        {
            if (string.IsNullOrWhiteSpace(value)) return value;
            string trimmed = value.Trim();
            if (DateTime.TryParseExact(trimmed, "r", CultureInfo.InvariantCulture,
                    DateTimeStyles.AdjustToUniversal | DateTimeStyles.AssumeUniversal, out DateTime parsed))
                return parsed.ToString("yyyy-MM-dd HH:mm:ss", CultureInfo.InvariantCulture) + " GMT";
            return value;
        }
    }
}