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

using MongoDB.Entities;

using PrivaPub.Domain.Statuses;
using PrivaPub.Federation.Actors;
using PrivaPub.Federation.Objects;
using PrivaPub.Federation.Outbox;
using PrivaPub.Federation.Rendering;
using PrivaPub.Models.Federation;
using PrivaPub.Models.Group;
using PrivaPub.Models.Post;
using PrivaPub.Models.Social;
using PrivaPub.Models.User;
using PrivaPub.StaticServices;

using System.Text.Json.Nodes;

using static PrivaPub.Federation.Inbox.ForeignMembers;
using static PrivaPub.Federation.Objects.ActivityJson;

using PostEntity = PrivaPub.Models.Post.Post;

namespace PrivaPub.Federation.Inbox.Handlers
{
	public class DeleteHandler : IActivityHandler
	{
		readonly DbEntities _dbEntities;
		readonly ILocalActorService _localActors;
		readonly IRemoteActorService _remoteActors;
		readonly IDeliveryService _delivery;
		readonly IGroupDistributor _groups;
		readonly IQuoteService _quotes;

		public DeleteHandler(DbEntities dbEntities, ILocalActorService localActors, IRemoteActorService remoteActors, IDeliveryService delivery,
			IGroupDistributor groups, IQuoteService quotes)
		{
			_quotes = quotes;
			_groups = groups;
			_dbEntities = dbEntities;
			_localActors = localActors;
			_remoteActors = remoteActors;
			_delivery = delivery;
		}

		public string Type => "Delete";

		const int MaxObjects = 50;

		public async Task Handle(JsonNode activity, ForeignAvatar actor, CancellationToken token)
		{
			// Funkwhale deletes several uploads at once, naming them in one list as the object's id
			var objectUris = activity["object"] is JsonObject { } inner && inner["id"] is JsonArray ids
				? ids.Select(Id).Where(id => id != default).Distinct(StringComparer.Ordinal).Take(MaxObjects).ToList()
				: new List<string> { Id(activity["object"]) };
			foreach (var objectUri in objectUris)
				await Handle(activity, actor, objectUri, token);
		}

		async Task Handle(JsonNode activity, ForeignAvatar actor, string objectUri, CancellationToken token)
		{
			if (!Origin.Same(objectUri, actor.ActorURI))
			{
				Arrival.Drop("cross-origin");
				return;
			}

			if (objectUri == actor.ActorURI)
			{
				Arrival.Accept("actor-delete");
				Arrival.About(actor.AvatarType.ToString(), created: actor.Published);
				actor.DeletionAt = DateTime.UtcNow;
				actor.AccountState = AvatarAccountState.Deleted;
				await DB.Default.SaveAsync(actor, token);
				var followers = await _dbEntities.Followers.Match(f => f.ActorURI == actor.ActorURI).ExecuteAsync(token);
				foreach (var follower in followers)
				{
					await DB.Default.DeleteAsync<Follower>(follower.ID);
					if (follower.LocalActorKind == LocalActorKind.Group)
						await RemoveForeignMember(follower.LocalActorId, actor.ActorURI, token);
				}
				await DB.Default.DeleteAsync<Following>(f => f.TargetActorURI == actor.ActorURI);
				await DB.Default.DeleteAsync<TimelineEntry>(e => e.AuthorAccountId == actor.ID);
				await DB.Default.Update<PostEntity>().Match(p => p.ActorURI == actor.ActorURI).Modify(p => p.AuthorGone, true).ExecuteAsync(token);
				await GoneActors.Forget(actor, token);
				return;
			}

			await RemoteDeletes.Tombstone(objectUri, token);
			var post = await _dbEntities.Posts.Match(p => p.ObjectURI == objectUri && p.ActorURI == actor.ActorURI).ExecuteFirstAsync(token);
			// deleted by another account of its author's server (Mobilizon's organiser deletes the group's event): once
			// that server says it is gone
			if (post == default && await _dbEntities.Posts.Match(p => p.ObjectURI == objectUri).ExecuteFirstAsync(token) is { } held
				&& held.ActorURI != actor.ActorURI && Origin.Same(held.ActorURI, actor.ActorURI) && await _remoteActors.IsGone(objectUri, token))
				post = held;
			if (post == default)
			{
				Arrival.Accept("tombstone-only");
				await _quotes.Revoke(objectUri, token);
				return;
			}
			Arrival.Accept("removed");
			Arrival.About(post.ObjectType, post.Visibility, post.CreationDate);
			await ReplyRelay.Pass(post, _dbEntities, _localActors, _delivery, token);
			await RemoteDeletes.Remove(post, objectUri, token);
			if (!string.IsNullOrEmpty(post.GroupId) && await _localActors.FindById(LocalActorKind.Group, post.GroupId, token) is { IsCircle: false } community)
				await _groups.Announce(community, activity.AsObject(), post.ObjectURI, isNewPost: false, token);
		}
	}
}