using System.Collections.Concurrent;
using System.Text.Json;
using System.Text.Json.Serialization;
using System.Text.Json.Serialization.Metadata;

using decePubClient.Models.Mastodon;

using PrivaPub.ClientModels;

namespace decePubClient.Helpers
{
	public sealed class UnregisteredJson : IJsonTypeInfoResolver
	{
		public static readonly UnregisteredJson Instance = new();
		static readonly DefaultJsonTypeInfoResolver Reflection = new();
		static readonly ConcurrentDictionary<Type, byte> Reported = new();

		public static bool Strict { get; set; }

		public JsonTypeInfo GetTypeInfo(Type type, JsonSerializerOptions options)
		{
			if (Strict)
				throw new NotSupportedException($"{type.FullName} is not registered in a JsonSerializerContext (HR0306).");
			if (Reported.TryAdd(type, 0))
				Console.Error.WriteLine($"{type.FullName} is serialized without a JsonSerializerContext registration (HR0306)");
			return Reflection.GetTypeInfo(type, options);
		}

		public static void Check(bool strict)
		{
			Strict = strict;
			if (!strict)
				return;
			var missing = Missing(ClientModelsJsonContext.Default, typeof(WebResult), "PrivaPub.ClientModels")
				.Concat(Missing(MastodonJsonContext.Default, typeof(Status), "decePubClient.Models.Mastodon"))
				.ToList();
			if (missing.Count > 0)
				throw new InvalidOperationException("Not registered in a JsonSerializerContext (HR0306): " + string.Join(", ", missing));
		}

		static IEnumerable<string> Missing(IJsonTypeInfoResolver context, Type anchor, string space) =>
			anchor.Assembly.GetTypes()
				.Where(t => t.IsClass && t.IsPublic && !t.IsAbstract && !t.IsGenericTypeDefinition && t.Namespace is { } ns && ns.StartsWith(space, StringComparison.Ordinal)
					&& !ns.EndsWith(".Resources", StringComparison.Ordinal) && !typeof(Attribute).IsAssignableFrom(t) && !typeof(JsonSerializerContext).IsAssignableFrom(t))
				.Where(t => context.GetTypeInfo(t, new JsonSerializerOptions()) == null)
				.Select(t => t.FullName);
	}
}