The inbox answers once it has verified, and processes from the job queue

InboxService is split the way the roadmap lays out Federation/Inbox:
- InboxReceiver reads and verifies the request exactly as before, runs
  the checks that need no fetch (the activity id's origin, a Follow of a
  missing or local-only actor, an Undo of someone else's activity, an
  embedded object attributed to someone else), queues a ProcessInbox job
  and answers 202. The job's dedupe key is the activity id, so a peer that
  delivers the same activity twice is processed once.
- InboxProcessor (two at a time, eight attempts) loads the verified actor
  and hands the activity to the handler for its type.
- Handlers/{Follow,Undo,Create,Delete,Update}Handler are the old methods,
  unchanged except that they no longer produce status codes; the JSON
  helpers live in Objects/ActivityJson and the group membership helpers in
  Inbox/ForeignMembers.

A slow fetch of an object or a remote actor now delays the job, not the
sender's HTTP request.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012CzABvBkbcFqoHdmi8b9WB

PrivaPub/Federation/Controllers/PeasantsController.cs

@@ -23,11 +23,11 @@ namespace PrivaPub.Federation.Controllers
 		const int OutboxSize = 20;
 
 		readonly ILocalActorService _localActors;
-		readonly IInboxService _inbox;
+		readonly IInboxReceiver _inbox;
 		readonly DbEntities _dbEntities;
 		readonly ILogger<PeasantsController> _logger;
 
-		public PeasantsController(ILocalActorService localActors, IInboxService inbox, DbEntities dbEntities,
+		public PeasantsController(ILocalActorService localActors, IInboxReceiver inbox, DbEntities dbEntities,
 			ILogger<PeasantsController> logger)
 		{
 			_localActors = localActors;

PrivaPub/Federation/Inbox/ForeignMembers.cs

@@ -0,0 +1,37 @@
+using MongoDB.Entities;
+
+using PrivaPub.Federation.Actors;
+using PrivaPub.Models.Federation;
+using PrivaPub.Models.Group;
+
+using GroupEntity = PrivaPub.Models.Group.Group;
+
+namespace PrivaPub.Federation.Inbox
+{
+	public static class ForeignMembers
+	{
+		public static async Task<bool> IsAcceptedFollower(LocalActor group, string actorUri, CancellationToken token) =>
+			await DB.Default.Find<Follower>()
+				.Match(f => f.LocalActorId == group.Id && f.LocalActorKind == LocalActorKind.Group && f.ActorURI == actorUri && f.IsAccepted)
+				.ExecuteAnyAsync(token);
+
+		public static async Task AddForeignMember(string groupId, string actorUri, CancellationToken token)
+		{
+			var group = await DB.Default.Find<GroupEntity>().MatchID(groupId).ExecuteFirstAsync(token);
+			if (group == default || group.Members.Any(m => m.IsForeign && m.AvatarId == actorUri))
+				return;
+			group.Members.Add(new GroupMember { AvatarId = actorUri, IsForeign = true });
+			group.UpdatedAt = DateTime.UtcNow;
+			await DB.Default.SaveAsync(group, token);
+		}
+
+		public static async Task RemoveForeignMember(string groupId, string actorUri, CancellationToken token)
+		{
+			var group = await DB.Default.Find<GroupEntity>().MatchID(groupId).ExecuteFirstAsync(token);
+			if (group == default || group.Members.RemoveAll(m => m.IsForeign && m.AvatarId == actorUri) == 0)
+				return;
+			group.UpdatedAt = DateTime.UtcNow;
+			await DB.Default.SaveAsync<GroupEntity>(group, token);
+		}
+	}
+}

PrivaPub/Federation/Inbox/Handlers/CreateHandler.cs

@@ -0,0 +1,169 @@
+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;
+		}
+	}
+}

PrivaPub/Federation/Inbox/Handlers/DeleteHandler.cs

@@ -0,0 +1,68 @@
+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 DeleteHandler : IActivityHandler
+	{
+		readonly DbEntities _dbEntities;
+		readonly ILocalActorService _localActors;
+		readonly IRemoteActorService _remoteActors;
+		readonly IDeliveryService _delivery;
+
+		public DeleteHandler(DbEntities dbEntities, ILocalActorService localActors, IRemoteActorService remoteActors, IDeliveryService delivery)
+		{
+			_dbEntities = dbEntities;
+			_localActors = localActors;
+			_remoteActors = remoteActors;
+			_delivery = delivery;
+		}
+
+		public string Type => "Delete";
+
+		public async Task Handle(JsonNode activity, ForeignAvatar actor, CancellationToken token)
+		{
+			var delete = activity;
+
+			var objectUri = Id(delete["object"]);
+			if (!Origin.Same(objectUri, actor.ActorURI))
+				return;
+
+			if (objectUri == actor.ActorURI)
+			{
+				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);
+				}
+				return;
+			}
+
+			await DB.Default.DeleteAsync<PostEntity>(p => p.ObjectURI == objectUri && p.ActorURI == actor.ActorURI);
+			await DB.Default.DeleteAsync<DmPostEntity>(p => p.ObjectURI == objectUri && p.ActorURI == actor.ActorURI);
+			return;
+				}
+	}
+}

PrivaPub/Federation/Inbox/Handlers/FollowHandler.cs

@@ -0,0 +1,75 @@
+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 FollowHandler : IActivityHandler
+	{
+		readonly DbEntities _dbEntities;
+		readonly ILocalActorService _localActors;
+		readonly IRemoteActorService _remoteActors;
+		readonly IDeliveryService _delivery;
+
+		public FollowHandler(DbEntities dbEntities, ILocalActorService localActors, IRemoteActorService remoteActors, IDeliveryService delivery)
+		{
+			_dbEntities = dbEntities;
+			_localActors = localActors;
+			_remoteActors = remoteActors;
+			_delivery = delivery;
+		}
+
+		public string Type => "Follow";
+
+		public async Task Handle(JsonNode activity, ForeignAvatar actor, CancellationToken token)
+		{
+			var follow = activity;
+			var follower = actor;
+
+			var target = await _localActors.FindByUri(Id(follow["object"]), token);
+			if (target is not { IsFederated: true } || target.Kind == LocalActorKind.Application)
+				return;
+
+			var existing = await _dbEntities.Followers
+				.Match(f => f.LocalActorId == target.Id && f.LocalActorKind == target.Kind && f.ActorURI == follower.ActorURI)
+				.ExecuteFirstAsync(token);
+			var record = existing ?? new Follower
+			{
+				LocalActorId = target.Id,
+				LocalActorKind = target.Kind,
+				ActorURI = follower.ActorURI
+			};
+			record.InboxURL = follower.InboxURL;
+			record.SharedInboxURL = follower.SharedInboxURL;
+			record.FollowActivityURI = Id(follow);
+			record.IsAccepted = existing?.IsAccepted == true || !target.ManuallyApprovesFollowers;
+			await DB.Default.SaveAsync(record, token);
+
+			if (!record.IsAccepted)
+				return;
+
+			if (target.Kind == LocalActorKind.Group)
+				await AddForeignMember(target.Id, follower.ActorURI, token);
+
+			var accept = ActivityPubRenderer.Accept(target, follow, $"accept-{record.ID}-{DateTime.UtcNow.Ticks}");
+			await _delivery.Enqueue(target, new[] { follower.InboxURL }, accept, token);
+			return;
+				}
+	}
+}

PrivaPub/Federation/Inbox/Handlers/UndoHandler.cs

@@ -0,0 +1,70 @@
+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 UndoHandler : IActivityHandler
+	{
+		readonly DbEntities _dbEntities;
+		readonly ILocalActorService _localActors;
+		readonly IRemoteActorService _remoteActors;
+		readonly IDeliveryService _delivery;
+
+		public UndoHandler(DbEntities dbEntities, ILocalActorService localActors, IRemoteActorService remoteActors, IDeliveryService delivery)
+		{
+			_dbEntities = dbEntities;
+			_localActors = localActors;
+			_remoteActors = remoteActors;
+			_delivery = delivery;
+		}
+
+		public string Type => "Undo";
+
+		public async Task Handle(JsonNode activity, ForeignAvatar actor, CancellationToken token)
+		{
+			var undo = activity;
+
+			var inner = undo["object"];
+			var innerType = inner is JsonObject ? Value(inner, "type") : default;
+			var innerId = Id(inner);
+
+			if (inner is JsonObject && Id(inner["actor"]) != actor.ActorURI)
+				return;
+			if (innerType is not (null or "Follow"))
+				return;
+
+			var followers = await _dbEntities.Followers.Match(f => f.ActorURI == actor.ActorURI).ExecuteAsync(token);
+			var targetUri = inner is JsonObject ? Id(inner["object"]) : default;
+			foreach (var follower in followers)
+			{
+				var matchesActivity = innerId != default && follower.FollowActivityURI == innerId;
+				var target = targetUri == default ? default : await _localActors.FindByUri(targetUri, token);
+				var matchesTarget = target != default && target.Id == follower.LocalActorId && target.Kind == follower.LocalActorKind;
+				if (!matchesActivity && !matchesTarget)
+					continue;
+
+				await DB.Default.DeleteAsync<Follower>(follower.ID);
+				if (follower.LocalActorKind == LocalActorKind.Group)
+					await RemoveForeignMember(follower.LocalActorId, actor.ActorURI, token);
+			}
+			return;
+				}
+	}
+}

PrivaPub/Federation/Inbox/Handlers/UpdateHandler.cs

@@ -0,0 +1,70 @@
+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 UpdateHandler : IActivityHandler
+	{
+		readonly DbEntities _dbEntities;
+		readonly ILocalActorService _localActors;
+		readonly IRemoteActorService _remoteActors;
+		readonly IDeliveryService _delivery;
+
+		public UpdateHandler(DbEntities dbEntities, ILocalActorService localActors, IRemoteActorService remoteActors, IDeliveryService delivery)
+		{
+			_dbEntities = dbEntities;
+			_localActors = localActors;
+			_remoteActors = remoteActors;
+			_delivery = delivery;
+		}
+
+		public string Type => "Update";
+
+		public async Task Handle(JsonNode activity, ForeignAvatar actor, CancellationToken token)
+		{
+			var update = activity;
+
+			var inner = update["object"];
+			if (Id(inner) == actor.ActorURI)
+			{
+				await _remoteActors.GetActor(actor.ActorURI, refresh: true, token);
+				return;
+			}
+			if (inner is not JsonObject || Id(inner["attributedTo"]) != actor.ActorURI || !Origin.Same(Id(inner), actor.ActorURI))
+				return;
+
+			var objectUri = Id(inner);
+			var text = ContentSanitizer.Html(Value(inner, "content"));
+			await DB.Default.Update<PostEntity>()
+				.Match(p => p.ObjectURI == objectUri && p.ActorURI == actor.ActorURI)
+				.Modify(p => p.Text, text)
+				.Modify(p => p.ContentHtml, text)
+				.Modify(p => p.UpdateDate, DateTime.UtcNow)
+				.ExecuteAsync(token);
+			await DB.Default.Update<DmPostEntity>()
+				.Match(p => p.ObjectURI == objectUri && p.ActorURI == actor.ActorURI)
+				.Modify(p => p.Text, text)
+				.Modify(p => p.ContentHtml, text)
+				.Modify(p => p.UpdateDate, DateTime.UtcNow)
+				.ExecuteAsync(token);
+			return;
+				}
+	}
+}

PrivaPub/Federation/Inbox/InboxProcessor.cs

@@ -0,0 +1,54 @@
+using PrivaPub.Federation.Actors;
+using PrivaPub.Infrastructure.Jobs;
+using PrivaPub.Models.Jobs;
+using PrivaPub.Models.User;
+
+using System.Text.Json;
+using System.Text.Json.Nodes;
+
+using static PrivaPub.Federation.Objects.ActivityJson;
+
+namespace PrivaPub.Federation.Inbox
+{
+	public interface IActivityHandler
+	{
+		string Type { get; }
+		Task Handle(JsonNode activity, ForeignAvatar actor, CancellationToken token);
+	}
+
+	public class InboxProcessor : IJobHandler
+	{
+		readonly IRemoteActorService _remoteActors;
+		readonly IReadOnlyDictionary<string, IActivityHandler> _handlers;
+		readonly ILogger<InboxProcessor> _logger;
+
+		public InboxProcessor(IRemoteActorService remoteActors, IEnumerable<IActivityHandler> handlers, ILogger<InboxProcessor> logger)
+		{
+			_remoteActors = remoteActors;
+			_handlers = handlers.ToDictionary(h => h.Type, StringComparer.Ordinal);
+			_logger = logger;
+		}
+
+		public JobKind Kind => JobKind.ProcessInbox;
+		public int Concurrency => 2;
+		public int MaxAttempts => 8;
+		public int PerHostLimit => 2;
+
+		public async Task<JobOutcome> Handle(Job job, CancellationToken token)
+		{
+			var payload = JsonSerializer.Deserialize<InboxPayload>(job.Payload);
+			var activity = payload == default ? default : JsonNode.Parse(payload.Activity);
+			var type = Value(activity, "type");
+			if (type == default || !_handlers.TryGetValue(type, out var handler))
+				return JobOutcome.Done;
+
+			var actor = await _remoteActors.GetActor(payload.ActorURI, refresh: false, token);
+			if (actor == default)
+				return JobOutcome.Retry("the actor could not be loaded");
+
+			await handler.Handle(activity, actor, token);
+			_logger.LogInformation("Processed {Type} {Id} from {Actor}", type, Id(activity), actor.ActorURI);
+			return JobOutcome.Done;
+		}
+	}
+}

PrivaPub/Federation/Inbox/InboxReceiver.cs

@@ -0,0 +1,126 @@
+using PrivaPub.Federation.Actors;
+using PrivaPub.Federation.Objects;
+using PrivaPub.Federation.Signing;
+using PrivaPub.Infrastructure.Jobs;
+using PrivaPub.Models.Federation;
+using PrivaPub.Models.Jobs;
+
+using System.Text.Json;
+using System.Text.Json.Nodes;
+
+using static PrivaPub.Federation.Objects.ActivityJson;
+
+namespace PrivaPub.Federation.Inbox
+{
+	public sealed record InboxResult(int StatusCode, string Error = default);
+
+	public sealed record InboxPayload(string ActorURI, string Activity);
+
+	public interface IInboxReceiver
+	{
+		Task<InboxResult> Receive(HttpRequest request, LocalActor recipient, CancellationToken token);
+	}
+
+	public class InboxReceiver : IInboxReceiver
+	{
+		const int MaxBodyBytes = 1024 * 1024;
+
+		readonly ILocalActorService _localActors;
+		readonly IRemoteActorService _remoteActors;
+		readonly IJobQueue _queue;
+		readonly ILogger<InboxReceiver> _logger;
+
+		public InboxReceiver(ILocalActorService localActors, IRemoteActorService remoteActors, IJobQueue queue, ILogger<InboxReceiver> logger)
+		{
+			_localActors = localActors;
+			_remoteActors = remoteActors;
+			_queue = queue;
+			_logger = logger;
+		}
+
+		public async Task<InboxResult> Receive(HttpRequest request, LocalActor recipient, CancellationToken token)
+		{
+			if (request.ContentLength > MaxBodyBytes)
+				return new(StatusCodes.Status413PayloadTooLarge);
+
+			using var buffer = new MemoryStream();
+			await request.Body.CopyToAsync(buffer, token);
+			if (buffer.Length > MaxBodyBytes)
+				return new(StatusCodes.Status413PayloadTooLarge);
+			var body = buffer.ToArray();
+
+			JsonNode activity;
+			try
+			{
+				activity = JsonNode.Parse(body);
+			}
+			catch (JsonException)
+			{
+				return new(StatusCodes.Status400BadRequest, "the body is not JSON");
+			}
+			if (activity is not JsonObject)
+				return new(StatusCodes.Status400BadRequest, "the body is not an activity");
+
+			var type = Value(activity, "type");
+			var actorUri = Id(activity["actor"]);
+			if (string.IsNullOrEmpty(type) || string.IsNullOrEmpty(actorUri))
+				return new(StatusCodes.Status400BadRequest, "type and actor are required");
+
+			var parameters = HttpSignatures.Parse(request.Headers["Signature"].ToString());
+			if (parameters == default)
+				return new(StatusCodes.Status401Unauthorized, "missing or unreadable Signature header");
+
+			var requestProblem = HttpSignatures.CheckRequest(request, parameters, body);
+			if (requestProblem != default)
+				return new(StatusCodes.Status401Unauthorized, requestProblem);
+
+			var signingString = HttpSignatures.SigningString(request, parameters);
+			var keyOwner = await _remoteActors.GetActorByKeyId(parameters.KeyId, refresh: false, token);
+			if (keyOwner == default && type == "Delete" && Id(activity["object"]) == actorUri)
+				return new(StatusCodes.Status202Accepted);
+			if (keyOwner == default || !HttpSignatures.Verify(keyOwner.PublicKey, signingString, parameters.Signature))
+			{
+				keyOwner = await _remoteActors.GetActorByKeyId(parameters.KeyId, refresh: true, token);
+				if (keyOwner == default || !HttpSignatures.Verify(keyOwner.PublicKey, signingString, parameters.Signature))
+					return new(StatusCodes.Status401Unauthorized, "the signature does not verify");
+			}
+
+			if (!string.Equals(keyOwner.ActorURI, actorUri, StringComparison.Ordinal))
+				return new(StatusCodes.Status401Unauthorized, "the activity's actor is not the key's owner");
+
+			var shapeProblem = await ShapeProblem(type, activity, actorUri, token);
+			if (shapeProblem != default)
+				return shapeProblem;
+
+			var activityId = Id(activity);
+			await _queue.Enqueue(JobKind.ProcessInbox, JsonSerializer.Serialize(new InboxPayload(actorUri, activity.ToJsonString())),
+				new Uri(actorUri).Host.ToLowerInvariant(), activityId == default ? default : "inbox|" + activityId, token);
+			_logger.LogInformation("Inbox {Recipient}: {Type} from {Actor} queued", recipient?.Handle ?? "shared", type, actorUri);
+			return new(StatusCodes.Status202Accepted);
+		}
+
+		async Task<InboxResult> ShapeProblem(string type, JsonNode activity, string actorUri, CancellationToken token)
+		{
+			var activityId = Id(activity);
+			if (activityId != default && !Origin.Same(activityId, actorUri))
+				return new(StatusCodes.Status400BadRequest, "the activity's id is not on its actor's origin");
+
+			var inner = activity["object"];
+			switch (type)
+			{
+				case "Follow":
+					var target = await _localActors.FindByUri(Id(inner), token);
+					if (target is not { IsFederated: true } || target.Kind == LocalActorKind.Application)
+						return new(StatusCodes.Status404NotFound, "no such local actor");
+					break;
+				case "Undo" when inner is JsonObject && Id(inner["actor"]) != actorUri:
+					return new(StatusCodes.Status400BadRequest, "an actor can only undo its own activities");
+				case "Create" or "Update" when inner is JsonObject && Origin.Same(Id(inner), actorUri)
+					&& inner["attributedTo"] != default && Id(inner["attributedTo"]) != actorUri
+					&& Value(inner, "type") is not ("Person" or "Service" or "Application" or "Group" or "Organization"):
+					return new(StatusCodes.Status400BadRequest, "the object is not attributed to the actor");
+			}
+			return default;
+		}
+	}
+}

PrivaPub/Federation/Inbox/InboxService.cs

@@ -1,413 +0,0 @@
-using MongoDB.Entities;
-
-using PrivaPub.Models.Federation;
-using PrivaPub.Models.Group;
-using PrivaPub.Models.Post;
-using PrivaPub.Models.User;
-using PrivaPub.StaticServices;
-
-using System.Text.Json;
-using System.Text.Json.Nodes;
-
-using DmPostEntity = PrivaPub.Models.Post.DmPost;
-using GroupEntity = PrivaPub.Models.Group.Group;
-using PostEntity = PrivaPub.Models.Post.Post;
-using PrivaPub.Federation.Actors;
-using PrivaPub.Federation.Signing;
-using PrivaPub.Federation.Rendering;
-using PrivaPub.Federation.Objects;
-using PrivaPub.Federation.Outbox;
-
-namespace PrivaPub.Federation.Inbox
-{
-	public sealed record InboxResult(int StatusCode, string Error = default);
-
-	public interface IInboxService
-	{
-		Task<InboxResult> Receive(HttpRequest request, LocalActor recipient, CancellationToken token);
-	}
-
-	public class InboxService : IInboxService
-	{
-		const int MaxBodyBytes = 1024 * 1024;
-
-		readonly DbEntities _dbEntities;
-		readonly ILocalActorService _localActors;
-		readonly IRemoteActorService _remoteActors;
-		readonly IDeliveryService _delivery;
-		readonly ILogger<InboxService> _logger;
-
-		public InboxService(DbEntities dbEntities, ILocalActorService localActors, IRemoteActorService remoteActors,
-			IDeliveryService delivery, ILogger<InboxService> logger)
-		{
-			_dbEntities = dbEntities;
-			_localActors = localActors;
-			_remoteActors = remoteActors;
-			_delivery = delivery;
-			_logger = logger;
-		}
-
-		public async Task<InboxResult> Receive(HttpRequest request, LocalActor recipient, CancellationToken token)
-		{
-			if (request.ContentLength > MaxBodyBytes)
-				return new(StatusCodes.Status413PayloadTooLarge);
-
-			using var buffer = new MemoryStream();
-			await request.Body.CopyToAsync(buffer, token);
-			if (buffer.Length > MaxBodyBytes)
-				return new(StatusCodes.Status413PayloadTooLarge);
-			var body = buffer.ToArray();
-
-			JsonNode activity;
-			try
-			{
-				activity = JsonNode.Parse(body);
-			}
-			catch (JsonException)
-			{
-				return new(StatusCodes.Status400BadRequest, "the body is not JSON");
-			}
-			if (activity is not JsonObject)
-				return new(StatusCodes.Status400BadRequest, "the body is not an activity");
-
-			var type = Value(activity, "type");
-			var actorUri = Id(activity["actor"]);
-			if (string.IsNullOrEmpty(type) || string.IsNullOrEmpty(actorUri))
-				return new(StatusCodes.Status400BadRequest, "type and actor are required");
-
-			var parameters = HttpSignatures.Parse(request.Headers["Signature"].ToString());
-			if (parameters == default)
-				return new(StatusCodes.Status401Unauthorized, "missing or unreadable Signature header");
-
-			var requestProblem = HttpSignatures.CheckRequest(request, parameters, body);
-			if (requestProblem != default)
-				return new(StatusCodes.Status401Unauthorized, requestProblem);
-
-			var signingString = HttpSignatures.SigningString(request, parameters);
-			var keyOwner = await _remoteActors.GetActorByKeyId(parameters.KeyId, refresh: false, token);
-			if (keyOwner == default && type == "Delete" && Id(activity["object"]) == actorUri)
-				return new(StatusCodes.Status202Accepted);
-			if (keyOwner == default || !HttpSignatures.Verify(keyOwner.PublicKey, signingString, parameters.Signature))
-			{
-				keyOwner = await _remoteActors.GetActorByKeyId(parameters.KeyId, refresh: true, token);
-				if (keyOwner == default || !HttpSignatures.Verify(keyOwner.PublicKey, signingString, parameters.Signature))
-					return new(StatusCodes.Status401Unauthorized, "the signature does not verify");
-			}
-
-			if (!string.Equals(keyOwner.ActorURI, actorUri, StringComparison.Ordinal))
-				return new(StatusCodes.Status401Unauthorized, "the activity's actor is not the key's owner");
-
-			var activityId = Id(activity);
-			if (activityId != default && !Origin.Same(activityId, actorUri))
-				return new(StatusCodes.Status400BadRequest, "the activity's id is not on its actor's origin");
-
-			_logger.LogInformation("Inbox {Recipient}: {Type} from {Actor}", recipient?.Handle ?? "shared", type, actorUri);
-
-			return type switch
-			{
-				"Follow" => await Follow(activity, keyOwner, token),
-				"Undo" => await Undo(activity, keyOwner, token),
-				"Create" => await Create(activity, keyOwner, token),
-				"Delete" => await Delete(activity, keyOwner, token),
-				"Update" => await Update(activity, keyOwner, token),
-				_ => new(StatusCodes.Status202Accepted)
-			};
-		}
-
-		async Task<InboxResult> Follow(JsonNode follow, ForeignAvatar follower, CancellationToken token)
-		{
-			var target = await _localActors.FindByUri(Id(follow["object"]), token);
-			if (target is not { IsFederated: true } || target.Kind == LocalActorKind.Application)
-				return new(StatusCodes.Status404NotFound, "no such local actor");
-
-			var existing = await _dbEntities.Followers
-				.Match(f => f.LocalActorId == target.Id && f.LocalActorKind == target.Kind && f.ActorURI == follower.ActorURI)
-				.ExecuteFirstAsync(token);
-			var record = existing ?? new Follower
-			{
-				LocalActorId = target.Id,
-				LocalActorKind = target.Kind,
-				ActorURI = follower.ActorURI
-			};
-			record.InboxURL = follower.InboxURL;
-			record.SharedInboxURL = follower.SharedInboxURL;
-			record.FollowActivityURI = Id(follow);
-			record.IsAccepted = existing?.IsAccepted == true || !target.ManuallyApprovesFollowers;
-			await DB.Default.SaveAsync(record, token);
-
-			if (!record.IsAccepted)
-				return new(StatusCodes.Status202Accepted);
-
-			if (target.Kind == LocalActorKind.Group)
-				await AddForeignMember(target.Id, follower.ActorURI, token);
-
-			var accept = ActivityPubRenderer.Accept(target, follow, $"accept-{record.ID}-{DateTime.UtcNow.Ticks}");
-			await _delivery.Enqueue(target, new[] { follower.InboxURL }, accept, token);
-			return new(StatusCodes.Status202Accepted);
-		}
-
-		async Task<InboxResult> Undo(JsonNode undo, ForeignAvatar actor, CancellationToken token)
-		{
-			var inner = undo["object"];
-			var innerType = inner is JsonObject ? Value(inner, "type") : default;
-			var innerId = Id(inner);
-
-			if (inner is JsonObject && Id(inner["actor"]) != actor.ActorURI)
-				return new(StatusCodes.Status400BadRequest, "an actor can only undo its own activities");
-			if (innerType is not (null or "Follow"))
-				return new(StatusCodes.Status202Accepted);
-
-			var followers = await _dbEntities.Followers.Match(f => f.ActorURI == actor.ActorURI).ExecuteAsync(token);
-			var targetUri = inner is JsonObject ? Id(inner["object"]) : default;
-			foreach (var follower in followers)
-			{
-				var matchesActivity = innerId != default && follower.FollowActivityURI == innerId;
-				var target = targetUri == default ? default : await _localActors.FindByUri(targetUri, token);
-				var matchesTarget = target != default && target.Id == follower.LocalActorId && target.Kind == follower.LocalActorKind;
-				if (!matchesActivity && !matchesTarget)
-					continue;
-
-				await DB.Default.DeleteAsync<Follower>(follower.ID);
-				if (follower.LocalActorKind == LocalActorKind.Group)
-					await RemoveForeignMember(follower.LocalActorId, actor.ActorURI, token);
-			}
-			return new(StatusCodes.Status202Accepted);
-		}
-
-		async Task<InboxResult> Create(JsonNode create, ForeignAvatar author, CancellationToken token)
-		{
-			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 new(StatusCodes.Status202Accepted);
-
-			var objectUri = Id(note);
-			if (string.IsNullOrEmpty(objectUri) || Id(note["attributedTo"]) != author.ActorURI)
-				return new(StatusCodes.Status400BadRequest, "the object is not attributed to the actor");
-
-			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 new(StatusCodes.Status202Accepted);
-
-				if (await _dbEntities.Posts.Match(p => p.ObjectURI == objectUri).ExecuteAnyAsync(token))
-					return new(StatusCodes.Status202Accepted);
-
-				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 new(StatusCodes.Status202Accepted);
-			}
-
-			var recipients = localTargets.Where(t => t.Kind == LocalActorKind.Person).ToList();
-			if (recipients.Count == 0)
-				return new(StatusCodes.Status202Accepted);
-			if (await _dbEntities.DmPosts.Match(p => p.ObjectURI == objectUri).ExecuteAnyAsync(token))
-				return new(StatusCodes.Status202Accepted);
-
-			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 new(StatusCodes.Status202Accepted);
-		}
-
-		async Task<InboxResult> Delete(JsonNode delete, ForeignAvatar actor, CancellationToken token)
-		{
-			var objectUri = Id(delete["object"]);
-			if (!Origin.Same(objectUri, actor.ActorURI))
-				return new(StatusCodes.Status202Accepted);
-
-			if (objectUri == actor.ActorURI)
-			{
-				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);
-				}
-				return new(StatusCodes.Status202Accepted);
-			}
-
-			await DB.Default.DeleteAsync<PostEntity>(p => p.ObjectURI == objectUri && p.ActorURI == actor.ActorURI);
-			await DB.Default.DeleteAsync<DmPostEntity>(p => p.ObjectURI == objectUri && p.ActorURI == actor.ActorURI);
-			return new(StatusCodes.Status202Accepted);
-		}
-
-		async Task<InboxResult> Update(JsonNode update, ForeignAvatar actor, CancellationToken token)
-		{
-			var inner = update["object"];
-			if (Id(inner) == actor.ActorURI)
-			{
-				await _remoteActors.GetActor(actor.ActorURI, refresh: true, token);
-				return new(StatusCodes.Status202Accepted);
-			}
-			if (inner is not JsonObject || Id(inner["attributedTo"]) != actor.ActorURI || !Origin.Same(Id(inner), actor.ActorURI))
-				return new(StatusCodes.Status202Accepted);
-
-			var objectUri = Id(inner);
-			var text = ContentSanitizer.Html(Value(inner, "content"));
-			await DB.Default.Update<PostEntity>()
-				.Match(p => p.ObjectURI == objectUri && p.ActorURI == actor.ActorURI)
-				.Modify(p => p.Text, text)
-				.Modify(p => p.ContentHtml, text)
-				.Modify(p => p.UpdateDate, DateTime.UtcNow)
-				.ExecuteAsync(token);
-			await DB.Default.Update<DmPostEntity>()
-				.Match(p => p.ObjectURI == objectUri && p.ActorURI == actor.ActorURI)
-				.Modify(p => p.Text, text)
-				.Modify(p => p.ContentHtml, text)
-				.Modify(p => p.UpdateDate, DateTime.UtcNow)
-				.ExecuteAsync(token);
-			return new(StatusCodes.Status202Accepted);
-		}
-
-		async Task<bool> IsAcceptedFollower(LocalActor group, string actorUri, CancellationToken token) =>
-			await _dbEntities.Followers
-				.Match(f => f.LocalActorId == group.Id && f.LocalActorKind == LocalActorKind.Group && f.ActorURI == actorUri && f.IsAccepted)
-				.ExecuteAnyAsync(token);
-
-		async Task AddForeignMember(string groupId, string actorUri, CancellationToken token)
-		{
-			var group = await _dbEntities.Groups.MatchID(groupId).ExecuteFirstAsync(token);
-			if (group == default || group.Members.Any(m => m.IsForeign && m.AvatarId == actorUri))
-				return;
-			group.Members.Add(new GroupMember { AvatarId = actorUri, IsForeign = true });
-			group.UpdatedAt = DateTime.UtcNow;
-			await DB.Default.SaveAsync(group, token);
-		}
-
-		async Task RemoveForeignMember(string groupId, string actorUri, CancellationToken token)
-		{
-			var group = await _dbEntities.Groups.MatchID(groupId).ExecuteFirstAsync(token);
-			if (group == default || group.Members.RemoveAll(m => m.IsForeign && m.AvatarId == actorUri) == 0)
-				return;
-			group.UpdatedAt = DateTime.UtcNow;
-			await DB.Default.SaveAsync<GroupEntity>(group, token);
-		}
-
-		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;
-		}
-
-		static IEnumerable<string> Addresses(JsonNode node)
-		{
-			foreach (var field in new[] { "to", "cc", "bto", "bcc", "audience" })
-			{
-				switch (node[field])
-				{
-					case JsonArray array:
-						foreach (var item in array)
-						{
-							var id = Id(item);
-							if (id != default)
-								yield return id;
-						}
-						break;
-					case JsonNode single when Id(single) is { } id:
-						yield return id;
-						break;
-				}
-			}
-		}
-
-		public static string Id(JsonNode node) => node switch
-		{
-			JsonValue value when value.TryGetValue<string>(out var text) => text,
-			JsonObject obj => Value(obj, "id") ?? Value(obj, "href"),
-			JsonArray array => array.Select(Id).FirstOrDefault(i => i != default),
-			_ => default
-		};
-
-		public static string Value(JsonNode node, string property) =>
-			node is JsonObject obj && obj[property] is JsonValue value && value.TryGetValue<string>(out var text) ? text : default;
-	}
-}

PrivaPub/Federation/Objects/ActivityJson.cs

@@ -0,0 +1,39 @@
+using System.Text.Json.Nodes;
+
+namespace PrivaPub.Federation.Objects
+{
+	public static class ActivityJson
+	{
+		public static string Id(JsonNode node) => node switch
+		{
+			JsonValue value when value.TryGetValue<string>(out var text) => text,
+			JsonObject obj => Value(obj, "id") ?? Value(obj, "href"),
+			JsonArray array => array.Select(Id).FirstOrDefault(i => i != default),
+			_ => default
+		};
+
+		public static string Value(JsonNode node, string property) =>
+			node is JsonObject obj && obj[property] is JsonValue value && value.TryGetValue<string>(out var text) ? text : default;
+
+		public static IEnumerable<string> Addresses(JsonNode node)
+		{
+			foreach (var field in new[] { "to", "cc", "bto", "bcc", "audience" })
+			{
+				switch (node[field])
+				{
+					case JsonArray array:
+						foreach (var item in array)
+						{
+							var id = Id(item);
+							if (id != default)
+								yield return id;
+						}
+						break;
+					case JsonNode single when Id(single) is { } id:
+						yield return id;
+						break;
+				}
+			}
+		}
+	}
+}