SocialPub/PrivaPub/Services/PersonaRemoval.cs

using MongoDB.Entities;

using OpenIddict.Abstractions;

using PrivaPub.Domain.Media;
using PrivaPub.Domain.Timelines;
using PrivaPub.Federation.Actors;
using PrivaPub.Federation.Outbox;
using PrivaPub.Federation.Rendering;
using PrivaPub.Models.Federation;
using PrivaPub.Models.Social;
using PrivaPub.Models.User;
using PrivaPub.StaticServices;

using System.Text.Json.Nodes;

using GroupEntity = PrivaPub.Models.Group.Group;
using PostEntity = PrivaPub.Models.Post.Post;

namespace PrivaPub.Services
{
	public interface IPersonaRemoval
	{
		/// <summary>Deletes one persona, and every group it owns: false when there is no such persona, or it is gone.</summary>
		Task<bool> Remove(string avatarId, CancellationToken token);
	}

	public interface IGroupRemoval
	{
		/// <summary>Deletes one group: false when there is no such group, or it is gone.</summary>
		Task<bool> Remove(string groupId, CancellationToken token);
	}

	// What deleting an actor tells: Delete{Actor} to its followers' (shared) inboxes, and to the inboxes of the other accounts
	// named (those a persona follows, a group's members elsewhere). A suspended persona sends it too: it is the one thing a
	// suspension lets through (DeliveryService.HeldBack).
	public static class ActorDeletion
	{
		public static async Task Announce(LocalActor actor, IEnumerable<string> others, DbEntities dbEntities, IDeliveryService delivery, CancellationToken token)
		{
			var inboxes = (await delivery.FollowerInboxes(actor, token)).ToList();
			var named = others.Where(uri => !string.IsNullOrEmpty(uri)).Distinct().ToList();
			if (named.Count > 0)
				inboxes.AddRange((await dbEntities.ForeignAvatars.Match(a => named.Contains(a.ActorURI)).ExecuteAsync(token))
					.Select(a => string.IsNullOrEmpty(a.SharedInboxURL) ? a.InboxURL : a.SharedInboxURL));
			await delivery.Enqueue(actor, inboxes.Where(i => !string.IsNullOrEmpty(i)).Distinct(), new JsonObject
			{
				["@context"] = ActivityPubRenderer.Context(),
				["id"] = actor.ActivityUri("delete-actor"),
				["type"] = "Delete",
				["actor"] = actor.Uri,
				["object"] = actor.Uri,
				["to"] = new JsonArray(ActivityPubRenderer.Public),
				["cc"] = new JsonArray(actor.Followers)
			}, token);
		}
	}

	// Deleting a persona (completion program R6: by its own login with its password, by an administrator with theirs, and
	// for each persona of a deleted login through RootRemoval) deletes everything public it had, as a deleted login's
	// personas always were: its Mastodon tokens end first, each group it owns goes (GroupRemoval), a Delete of the actor goes
	// to its followers and to the accounts it follows, its posts are emptied, and its name stays reserved while its documents
	// answer 410. What it kept for itself (lists, filters, followed hashtags, scheduled posts, what it did with the
	// announcements, the feeds it read, its featured hashtags, endorsements, notes and dismissed suggestions, its media)
	// goes with it. Its link to its login stays, so the login keeps no other
	// trace than that.
	public class PersonaRemoval : IPersonaRemoval
	{
		readonly DbEntities _dbEntities;
		readonly ILocalActorService _localActors;
		readonly IDeliveryService _delivery;
		readonly IMediaService _media;
		readonly IGroupRemoval _groups;
		readonly IOpenIddictTokenManager _tokens;
		readonly IOpenIddictAuthorizationManager _authorizations;

		public PersonaRemoval(DbEntities dbEntities, ILocalActorService localActors, IDeliveryService delivery, IMediaService media, IGroupRemoval groups,
			IOpenIddictTokenManager tokens, IOpenIddictAuthorizationManager authorizations)
		{
			_dbEntities = dbEntities;
			_localActors = localActors;
			_delivery = delivery;
			_media = media;
			_groups = groups;
			_tokens = tokens;
			_authorizations = authorizations;
		}

		public async Task<bool> Remove(string avatarId, CancellationToken token)
		{
			var avatar = string.IsNullOrEmpty(avatarId) ? default : await _dbEntities.Avatars.MatchID(avatarId).Match(a => !a.DeletionAt.HasValue).ExecuteFirstAsync(token);
			if (avatar == default)
				return false;
			var now = DateTime.UtcNow;
			// nothing acts as it while it goes
			await _tokens.RevokeBySubjectAsync(avatar.ID, token);
			await _authorizations.RevokeBySubjectAsync(avatar.ID, token);
			Streams.CloseFor(avatar.ID);

			foreach (var group in await _dbEntities.Groups.Match(g => g.OwnerAvatarId == avatar.ID && !g.DeletionAt.HasValue).ExecuteAsync(token))
				await _groups.Remove(group.ID, token);
			var persona = _localActors.FromAvatar(avatar);
			var followed = (await _dbEntities.Followings.Match(f => f.AvatarId == avatar.ID && !f.TargetIsLocal).ExecuteAsync(token))
				.Select(f => f.TargetActorURI);
			await ActorDeletion.Announce(persona, followed, _dbEntities, _delivery, token);
			await DB.Default.Update<Avatar>().MatchID(avatar.ID).Modify(a => a.DeletionAt, now).ExecuteAsync(token);
			await Empty(avatar.ID, now, token);
			await DB.Default.DeleteAsync<PersonaListMember>(m => m.AvatarId == avatar.ID);
			await DB.Default.DeleteAsync<PersonaList>(l => l.AvatarId == avatar.ID);
			await DB.Default.DeleteAsync<PersonaFilter>(f => f.AvatarId == avatar.ID);
			await DB.Default.DeleteAsync<FollowedTag>(t => t.AvatarId == avatar.ID);
			// what it did with the server's announcements, kept for it alone
			await DB.Default.DeleteAsync<AnnouncementRead>(r => r.AvatarId == avatar.ID);
			await DB.Default.DeleteAsync<AnnouncementReaction>(r => r.AvatarId == avatar.ID);
			// (the reader of feeds stops following what nobody reads any more at its next round)
			await DB.Default.DeleteAsync<FeedSubscription>(s => s.AvatarId == avatar.ID);
			// what the Mastodon API kept for it (R8): its featured hashtags (the Delete of the actor takes them from other
			// servers), its endorsements, its private notes and its dismissed suggestions, and what other personas here kept
			// about it: their endorsements of it and their notes on it
			await DB.Default.DeleteAsync<FeaturedTag>(t => t.AvatarId == avatar.ID);
			await DB.Default.DeleteAsync<Endorsement>(e => e.AvatarId == avatar.ID || e.TargetAccountId == avatar.ID);
			await DB.Default.DeleteAsync<PersonaNote>(n => n.AvatarId == avatar.ID || n.TargetAccountId == avatar.ID);
			await DB.Default.DeleteAsync<SuggestionDismissal>(d => d.AvatarId == avatar.ID || d.AccountId == avatar.ID);
			// nothing of it publishes later, and none of its files stays served: its posts' media, its pictures and what its
			// scheduled posts held
			await DB.Default.DeleteAsync<ScheduledStatus>(s => s.AvatarId == avatar.ID);
			await _media.Trash(m => m.OwnerAvatarId == avatar.ID, "persona removed", token);
			return true;
		}

		// a persona's posts keep their ids and lose their content, like a single deleted post; a group writes none of its own
		static async Task Empty(string avatarId, DateTime now, CancellationToken token)
		{
			var postIds = (await DB.Default.Find<PostEntity>().Match(p => p.GroupUserId == avatarId && !p.IsFederatedCopy && !p.DeletedAt.HasValue)
				.Project(p => p.Include(x => x.ID)).ExecuteAsync(token)).Select(p => p.ID).ToList();
			if (postIds.Count == 0)
				return;
			await DB.Default.Update<PostEntity>().Match(p => postIds.Contains(p.ID))
				.Modify(p => p.DeletedAt, now)
				.Modify(p => p.Text, null)
				.Modify(p => p.ContentHtml, null)
				.Modify(p => p.Title, null)
				.Modify(p => p.SpoilerText, null)
				.Modify(p => p.Media, new List<Models.Post.PostMedia>())
				.Modify(p => p.Revisions, new List<Models.Post.PostRevision>())
				.ExecuteAsync(token);
			await DB.Default.DeleteAsync<TimelineEntry>(e => postIds.Contains(e.PostId) || postIds.Contains(e.ReblogOfPostId));
		}
	}

	// Deleting a group (completion program R6: by its owner with the login's password, by an administrator with theirs, and
	// with the persona that owns it): a Delete of the group's actor to its followers and its members elsewhere, its name kept
	// reserved while its documents answer 410, and the personas here that followed or joined it no longer do. The posts made
	// in it stay their authors'.
	public class GroupRemoval : IGroupRemoval
	{
		readonly DbEntities _dbEntities;
		readonly ILocalActorService _localActors;
		readonly IDeliveryService _delivery;

		public GroupRemoval(DbEntities dbEntities, ILocalActorService localActors, IDeliveryService delivery)
		{
			_dbEntities = dbEntities;
			_localActors = localActors;
			_delivery = delivery;
		}

		public async Task<bool> Remove(string groupId, CancellationToken token)
		{
			var group = string.IsNullOrEmpty(groupId) ? default : await _dbEntities.Groups.MatchID(groupId).Match(g => !g.DeletionAt.HasValue).ExecuteFirstAsync(token);
			if (group == default)
				return false;
			var actor = _localActors.FromGroup(group);
			await ActorDeletion.Announce(actor, group.Members.Where(m => m.IsForeign).Select(m => m.AvatarId), _dbEntities, _delivery, token);
			await DB.Default.Update<GroupEntity>().MatchID(group.ID).Modify(g => g.DeletionAt, DateTime.UtcNow).ExecuteAsync(token);
			await DB.Default.DeleteAsync<Following>(f => f.TargetActorURI == actor.Uri);
			await DB.Default.DeleteAsync<Follower>(f => f.LocalActorId == group.ID && f.LocalActorKind == LocalActorKind.Group);
			return true;
		}
	}
}