namespace IM_API.Tools
{
    public static class ObjectNameGenerator
    {
        public static string Generate(ObjectNameContext ctx)
        {
            var ext = GetExtension(ctx.FileName, ctx.ContentType);
            var shortId = Guid.NewGuid().ToString("N")[..12];

            var parts = new List<string>
        {
            ctx.Biz,
            ctx.Now.Year.ToString(),
            ctx.Now.Month.ToString("D2")
        };

            if (ctx.UserId.HasValue)
            {
                parts.Add(ctx.UserId.Value.ToString());
            }

            parts.Add($"{shortId}{ext}");

            return string.Join("/", parts);
        }

        private static string GetExtension(string fileName, string contentType)
        {
            var ext = Path.GetExtension(fileName);
            if (!string.IsNullOrWhiteSpace(ext))
                return ext.ToLowerInvariant();

            return contentType switch
            {
                "image/jpeg" => ".jpg",
                "image/png" => ".png",
                "video/mp4" => ".mp4",
                _ => ".bin"
            };
        }
    }
    public class ObjectNameContext
    {
        public string Biz { get; init; } = "IM";
        public long? UserId { get; init; }
        public string FileName { get; init; } = default!;
        public string ContentType { get; init; } = default!;
        public DateTimeOffset Now { get; init; } = DateTimeOffset.UtcNow;
    }

}