using MongoDB.Entities;

using PrivaPub.Federation.Objects;
using PrivaPub.Infrastructure.Http;
using PrivaPub.Infrastructure.Jobs;
using PrivaPub.Models.Jobs;
using PrivaPub.Models.User;
using PrivaPub.StaticServices;

namespace PrivaPub.Federation.Actors
{
	// A remote account's follower, following and post counts, as its own server publishes them (the totalItems of its
	// followers, following and outbox collections). Read when the account is fetched, at most once a day, never when
	// someone looks at it; a hidden or missing collection leaves its count unknown. Mastodon and GoToSocial do the same.
	public class AccountCountsJob : IJobHandler
	{
		readonly IRemoteActorService _remoteActors;
		readonly DbEntities _dbEntities;

		public AccountCountsJob(IRemoteActorService remoteActors, DbEntities dbEntities)
		{
			_remoteActors = remoteActors;
			_dbEntities = dbEntities;
		}

		public JobKind Kind => JobKind.CountAccount;
		public int Concurrency => 2;
		public int MaxAttempts => 2;
		public int PerHostLimit => 1;

		public static string DedupeKey(string actorUri, DateTime day) => $"count|{actorUri}|{day:yyyyMMdd}";

		public async Task<JobOutcome> Handle(Job job, CancellationToken token)
		{
			var actor = await _dbEntities.ForeignAvatars.Match(a => a.ActorURI == job.Payload && !a.DeletionAt.HasValue).ExecuteFirstAsync(token);
			if (actor == default)
				return JobOutcome.Done;
			await DB.Default.Update<ForeignAvatar>().MatchID(actor.ID)
				.Modify(a => a.FollowersCount, await Total(actor, actor.FollowersURL, token))
				.Modify(a => a.FollowingCount, await Total(actor, actor.FollowingURL, token))
				.Modify(a => a.StatusesCount, await Total(actor, actor.OutboxURL, token))
				.Modify(a => a.CountedAt, DateTime.UtcNow)
				.ExecuteAsync(token);
			return JobOutcome.Done;
		}

		// only from the actor's own server, as everything we believe about it
		async Task<int?> Total(ForeignAvatar actor, string collection, CancellationToken token)
		{
			if (string.IsNullOrEmpty(collection) || !Origin.Same(collection, actor.ActorURI))
				return default;
			using var scope = HttpScope.For("collection");
			using var fetched = await _remoteActors.FetchObject(collection, token);
			return fetched != default && fetched.Root.ValueKind == System.Text.Json.JsonValueKind.Object
				&& fetched.Root.TryGetProperty("totalItems", out var total) && total.TryGetInt32(out var count) && count >= 0
				? count
				: default;
		}
	}
}