[backend/federation] Deliver activities to mentioned users

Iceshrimp.Backend/Core/Federation/ActivityPub/ActivityDeliverService.cs

@@ -14,7 +14,7 @@ public class ActivityDeliverService(
 	DatabaseContext db,
 	QueueService queueService
 ) {
-	public async Task DeliverToFollowersAsync(ASActivity activity, User actor) {
+	public async Task DeliverToFollowersAsync(ASActivity activity, User actor, IEnumerable<User> recipients) {
 		logger.LogDebug("Delivering activity {id} to followers", activity.Id);
 		if (activity.Actor == null) throw new Exception("Actor must not be null");
 
@@ -25,6 +25,11 @@ public class ActivityDeliverService(
 		                        .Distinct()
 		                        .ToListAsync();
 
+		inboxUrls = inboxUrls
+		            .Concat(recipients.Select(p => p.SharedInbox ?? p.Inbox).Where(p => p != null).Select(p => p!))
+		            .Distinct()
+		            .ToList();
+
 		if (inboxUrls.Count == 0) return;
 
 		var keypair = await db.UserKeypairs.FirstAsync(p => p.User == actor);

Iceshrimp.Backend/Core/Services/NoteService.cs

@@ -76,12 +76,20 @@ public class NoteService(
 		var obj      = await noteRenderer.RenderAsync(note, mentions);
 		var activity = ActivityRenderer.RenderCreate(obj, actor);
 
+		var recipients = await db.Users
+		                         .Where(p => note.VisibleUserIds.Contains(p.Id))
+		                         .Select(p => new User {
+			                         Host        = p.Host,
+			                         Inbox       = p.Inbox,
+			                         SharedInbox = p.SharedInbox
+		                         })
+		                         .ToListAsync();
+
 		if (note.Visibility == Note.NoteVisibility.Specified) {
-			var recipients = await db.Users.Where(p => note.VisibleUserIds.Contains(p.Id)).ToListAsync();
 			await deliverSvc.DeliverToAsync(activity, user, recipients);
 		}
 		else {
-			await deliverSvc.DeliverToFollowersAsync(activity, user);
+			await deliverSvc.DeliverToFollowersAsync(activity, user, recipients);
 		}
 
 		return note;