SocialPub/PrivaPub/Infrastructure/Http/HttpScope.cs

namespace PrivaPub.Infrastructure.Http
{
	public static class HttpScope
	{
		public const string Request = "request";

		sealed record Tags(string Purpose, string Trigger, bool Crawl, string UserAgent = default);

		static readonly AsyncLocal<Tags> current = new();

		public static string Purpose => current.Value?.Purpose;
		public static string Trigger => current.Value?.Trigger ?? Request;
		public static bool Crawling => current.Value?.Crawl == true;
		public static string UserAgent => current.Value?.UserAgent;

		public static IDisposable For(string purpose) => Push(tags => tags with { Purpose = purpose });

		public static IDisposable Default(string purpose) => Push(tags => tags with { Purpose = tags.Purpose ?? purpose });

		public static IDisposable Triggered(string trigger) => Push(tags => tags with { Trigger = trigger });

		public static IDisposable Crawl(string userAgent = default) => Push(tags => tags with { Crawl = true, UserAgent = userAgent ?? tags.UserAgent });

		static IDisposable Push(Func<Tags, Tags> change)
		{
			var previous = current.Value;
			current.Value = change(previous ?? new Tags(default, default, false));
			return new Restore(previous);
		}

		sealed class Restore : IDisposable
		{
			readonly Tags _previous;

			public Restore(Tags previous) => _previous = previous;

			public void Dispose() => current.Value = _previous;
		}
	}
}