SocialPub/PrivaPub/Federation/Inbox/Handlers/AcceptHandler.cs

using MongoDB.Entities;

using PrivaPub.Domain.Statuses;
using PrivaPub.Federation.Actors;
using PrivaPub.Models.Social;
using PrivaPub.Models.User;
using PrivaPub.StaticServices;

using System.Text.Json.Nodes;

using static PrivaPub.Federation.Objects.ActivityJson;

namespace PrivaPub.Federation.Inbox.Handlers
{
	public class AcceptHandler : IActivityHandler
	{
		readonly DbEntities _dbEntities;
		readonly ILocalActorService _localActors;
		readonly IQuoteService _quotes;
		readonly IInteractionApprovals _approvals;
		readonly IParticipations _participations;
		readonly Relays.IRelays _relays;
		readonly Infrastructure.Jobs.IJobQueue _queue;

		public AcceptHandler(DbEntities dbEntities, ILocalActorService localActors, IQuoteService quotes, IInteractionApprovals approvals = default,
			IParticipations participations = default, Relays.IRelays relays = default, Infrastructure.Jobs.IJobQueue queue = default)
		{
			_queue = queue;
			_relays = relays;
			_participations = participations;
			_dbEntities = dbEntities;
			_localActors = localActors;
			_quotes = quotes;
			_approvals = approvals;
		}

		public virtual string Type => "Accept";

		public async Task Handle(JsonNode activity, ForeignAvatar actor, CancellationToken token)
		{
			if (await _quotes.Answered(activity, actor, accepted: Type == "Accept", token))
			{
				Arrival.Accept("quote-answer");
				return;
			}
			if (_approvals != default && await _approvals.Answered(activity, actor, accepted: Type == "Accept", token))
			{
				Arrival.Accept("interaction-answer");
				return;
			}
			if (_participations != default && await _participations.Answered(activity, actor, accepted: Type == "Accept", token))
			{
				Arrival.Accept("participation-answer");
				return;
			}
			if (_relays != default && await _relays.Answered(activity, actor, accepted: Type == "Accept", token))
			{
				Arrival.Accept("relay-answer");
				return;
			}
			var following = await FindFollowing(activity["object"], actor, _dbEntities, _localActors, token);
			if (following == default)
			{
				Arrival.Drop("unknown-object");
				return;
			}
			Arrival.About("Follow");
			Arrival.Accept("follow-answer");
			await Apply(following, token);
		}

		// the follow holds: the account's latest public posts are read from its outbox (OutboxBackfill), once a day at most
		protected virtual async Task Apply(Following following, CancellationToken token)
		{
			await DB.Default.Update<Following>().MatchID(following.ID).Modify(f => f.State, FollowState.Accepted).ExecuteAsync(token);
			if (_queue != default)
				await _queue.Enqueue(Models.Jobs.JobKind.BackfillOutbox, following.TargetActorURI, new Uri(following.TargetActorURI).Host,
					Actors.OutboxBackfill.DedupeKey(following.TargetActorURI, DateTime.UtcNow), token);
		}

		public static async Task<Following> FindFollowing(JsonNode follow, ForeignAvatar target, DbEntities dbEntities, ILocalActorService localActors,
			CancellationToken token)
		{
			if (follow is JsonObject && Value(follow, "type") is { } type && type != "Follow")
				return default;
			// (a follow sent again names the first one under a new id: FollowService.AgainId)
			var followId = Id(follow) is { } named && named.IndexOf(Domain.Social.FollowService.Again, StringComparison.Ordinal) is var at and > 0
				? named[..at]
				: Id(follow);
			var byId = followId == default
				? default
				: await dbEntities.Followings.Match(f => f.FollowActivityURI == followId && f.TargetActorURI == target.ActorURI).ExecuteFirstAsync(token);
			if (byId != default || follow is not JsonObject)
				return byId;

			var follower = await localActors.FindByUri(Id(follow["actor"]), token);
			return follower == default
				? default
				: await dbEntities.Followings.Match(f => f.AvatarId == follower.Id && f.TargetActorURI == target.ActorURI).ExecuteFirstAsync(token);
		}
	}

	public class RejectHandler : AcceptHandler
	{
		public RejectHandler(DbEntities dbEntities, ILocalActorService localActors, IQuoteService quotes, IInteractionApprovals approvals = default,
			IParticipations participations = default, Relays.IRelays relays = default)
			: base(dbEntities, localActors, quotes, approvals, participations, relays, queue: default)
		{
		}

		public override string Type => "Reject";

		protected override Task Apply(Following following, CancellationToken token) => DB.Default.DeleteAsync<Following>(following.ID);
	}
}