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

using MongoDB.Entities;

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.User;
using PrivaPub.StaticServices;

using System.Text.Json.Nodes;

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

using DmPostEntity = PrivaPub.Models.Post.DmPost;
using PostEntity = PrivaPub.Models.Post.Post;

namespace PrivaPub.Federation.Inbox.Handlers
{
	public class CreateHandler : IActivityHandler
	{
		readonly DbEntities _dbEntities;
		readonly ILocalActorService _localActors;
		readonly IRemoteActorService _remoteActors;
		readonly IDeliveryService _delivery;

		public CreateHandler(DbEntities dbEntities, ILocalActorService localActors, IRemoteActorService remoteActors, IDeliveryService delivery)
		{
			_dbEntities = dbEntities;
			_localActors = localActors;
			_remoteActors = remoteActors;
			_delivery = delivery;
		}

		public string Type => "Create";

		public async Task Handle(JsonNode activity, ForeignAvatar actor, CancellationToken token)
		{
			var create = activity;
			var author = actor;

			var note = create["object"];
			if (note is not JsonObject || !Origin.Same(Id(note), author.ActorURI))
			{
				using var fetched = await _remoteActors.FetchObject(Id(note), token);
				note = fetched == default ? default : JsonNode.Parse(fetched.Root.GetRawText());
			}
			if (note is not JsonObject || Value(note, "type") is not ("Note" or "Article" or "Page" or "Question"))
				return;

			var objectUri = Id(note);
			if (string.IsNullOrEmpty(objectUri) || Id(note["attributedTo"]) != author.ActorURI)
				return;

			var addressed = Addresses(note).Concat(Addresses(create)).Distinct(StringComparer.Ordinal).ToList();
			var isPublic = addressed.Contains(ActivityPubRenderer.Public) || addressed.Contains("as:Public") || addressed.Contains("Public");
			var inReplyTo = Id(note["inReplyTo"]);

			var localTargets = new List<LocalActor>();
			foreach (var uri in addressed.Concat(new[] { Id(note["audience"]) }).Where(u => u != default).Distinct())
			{
				var local = await _localActors.FindByUri(uri, token);
				if (local is { IsFederated: true } && localTargets.All(l => l.Id != local.Id))
					localTargets.Add(local);
			}

			if (isPublic || addressed.Any(a => a == author.ActorURI + "/followers" || a.EndsWith("/followers")))
			{
				var group = localTargets.FirstOrDefault(t => t.Kind == LocalActorKind.Group);
				if (group != default && !await IsAcceptedFollower(group, author.ActorURI, token))
					group = default;
				if (group == default && localTargets.All(t => t.Kind != LocalActorKind.Person))
					return;

				if (await _dbEntities.Posts.Match(p => p.ObjectURI == objectUri).ExecuteAnyAsync(token))
					return;

				var html = ContentSanitizer.Html(Value(note, "content"));
				var post = new PostEntity
				{
					ObjectURI = objectUri,
					ActorURI = author.ActorURI,
					GroupId = group?.Id,
					Title = Value(note, "summary") ?? Value(note, "name"),
					Text = html,
					ContentHtml = html,
					ContentFormat = ContentFormat.Html,
					HasContentWarning = note["sensitive"] is JsonValue sensitive && sensitive.TryGetValue<bool>(out var s) && s,
					AnsweringToPostId = await LocalPostId(inReplyTo, token) ?? inReplyTo,
					IsFederatedCopy = true,
					CreationDate = DateTime.TryParse(Value(note, "published"), out var published) ? published.ToUniversalTime() : DateTime.UtcNow
				};
				await DB.Default.SaveAsync(post, token);

				if (group != default)
				{
					var announce = ActivityPubRenderer.Announce(group, objectUri, $"announce-{post.ID}");
					await _delivery.EnqueueToFollowers(group, announce, token);
				}
				return;
			}

			var recipients = localTargets.Where(t => t.Kind == LocalActorKind.Person).ToList();
			if (recipients.Count == 0)
				return;
			if (await _dbEntities.DmPosts.Match(p => p.ObjectURI == objectUri).ExecuteAnyAsync(token))
				return;

			var participants = recipients.Select(r => r.Uri)
				.Concat(addressed.Where(a => a != ActivityPubRenderer.Public && !a.EndsWith("/followers") && !a.EndsWith("/following")))
				.Append(author.ActorURI)
				.ToList();
			var context = Value(note, "context") ?? Value(note, "conversation");
			var dmGroup = await FindOrCreateDmGroup(participants, Origin.Same(context, author.ActorURI) ? context : default, token);
			var dmHtml = ContentSanitizer.Html(Value(note, "content"));
			var dm = new DmPostEntity
			{
				ObjectURI = objectUri,
				ActorURI = author.ActorURI,
				GroupId = dmGroup.ID,
				Title = Value(note, "summary"),
				Text = dmHtml,
				ContentHtml = dmHtml,
				ContentFormat = ContentFormat.Html,
				HasContentWarning = note["sensitive"] is JsonValue dmSensitive && dmSensitive.TryGetValue<bool>(out var ds) && ds,
				AnsweringToPostId = inReplyTo,
				IsFederatedCopy = true,
				CreationDate = DateTime.TryParse(Value(note, "published"), out var dmPublished) ? dmPublished.ToUniversalTime() : DateTime.UtcNow
			};
			await DB.Default.SaveAsync(dm, token);
			await DB.Default.Update<DmGroup>().MatchID(dmGroup.ID).Modify(g => g.UpdatedAt, DateTime.UtcNow).ExecuteAsync(token);
			return;
				}

async Task<DmGroup> FindOrCreateDmGroup(List<string> participantUris, string context, CancellationToken token)
		{
			var members = new List<GroupMember>();
			foreach (var uri in participantUris.Distinct(StringComparer.Ordinal))
			{
				var local = await _localActors.FindByUri(uri, token);
				var member = local != default && local.Kind == LocalActorKind.Person
					? new GroupMember { AvatarId = local.Id }
					: new GroupMember { AvatarId = uri, IsForeign = true };
				if (members.All(m => m.AvatarId != member.AvatarId || m.IsForeign != member.IsForeign))
					members.Add(member);
			}

			var key = DmGroup.KeyOf(members);
			var match = await _dbEntities.DmGroups.Match(g => g.ParticipantsKey == key && !g.DeletionAt.HasValue).ExecuteFirstAsync(token);
			if (match != default)
				return match;

			var dmGroup = new DmGroup { Members = members, ConversationURI = context, ParticipantsKey = key };
			await DB.Default.SaveAsync(dmGroup, token);
			return dmGroup;
		}

async Task<string> LocalPostId(string uri, CancellationToken token)
		{
			if (string.IsNullOrEmpty(uri) || !uri.StartsWith(_localActors.BaseAddress + "/peasants/", StringComparison.OrdinalIgnoreCase))
				return default;
			var id = uri[(uri.LastIndexOf('/') + 1)..];
			return await _dbEntities.Posts.MatchID(id).ExecuteAnyAsync(token) ? id : default;
		}
	}
}