Funkwhale's answers, deletions and NodeInfo are understood

Three shapes Funkwhale 2.0 sends, each of which lost something:
- its Accept is named after the Follow it answers, on our origin (`…#follows/<uuid>/accept`), and was refused as off its
  actor's origin, so no follow of a channel completed: an Accept or Reject whose id extends the id of the activity it
  answers, on our origin, is now taken;
- a channel deletes its uploads in one Delete without an id, their ids in a list as the object's id: each is deleted;
- its NodeInfo discovery names the document under its swagger schema's URL: a link whose path names NodeInfo is taken
  when no rel is known.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LsXgEaXee4GCU1hwYgPJXw

PrivaPub/Federation/Inbox/Handlers/DeleteHandler.cs

@@ -43,11 +43,20 @@ namespace PrivaPub.Federation.Inbox.Handlers
 
 		public string Type => "Delete";
 
+		const int MaxObjects = 50;
+
 		public async Task Handle(JsonNode activity, ForeignAvatar actor, CancellationToken token)
 		{
-			var delete = activity;
+			// 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);
+		}
 
-			var objectUri = Id(delete["object"]);
+		async Task Handle(JsonNode activity, ForeignAvatar actor, string objectUri, CancellationToken token)
+		{
 			if (!Origin.Same(objectUri, actor.ActorURI))
 			{
 				Arrival.Drop("cross-origin");

PrivaPub/Federation/Inbox/InboxReceiver.cs

@@ -222,7 +222,10 @@ namespace PrivaPub.Federation.Inbox
 		async Task<InboxResult> ShapeProblem(string type, JsonNode activity, string actorUri, CancellationToken token)
 		{
 			var activityId = Id(activity);
-			if (activityId != default && !Origin.Same(activityId, actorUri))
+			// (Funkwhale names its answer after the activity it answers: `<our Follow's id>/accept`)
+			if (activityId != default && !Origin.Same(activityId, actorUri)
+				&& !(type is "Accept" or "Reject" && Id(activity["object"]) is { } answered && Origin.Same(answered, _localActors.BaseAddress)
+					&& activityId.StartsWith(answered + "/", StringComparison.Ordinal)))
 				return new(StatusCodes.Status400BadRequest, "the activity's id is not on its actor's origin", Reason: "id-cross-origin");
 
 			var inner = activity["object"];

PrivaPub/Federation/Objects/InstanceDocuments.cs

@@ -38,6 +38,12 @@ namespace PrivaPub.Federation.Objects
 					if (link.ValueKind == JsonValueKind.Object && Text(link, "rel") == schema && Text(link, "href") is { } href
 						&& href.StartsWith("https://", StringComparison.OrdinalIgnoreCase))
 						return (href, schema[(schema.LastIndexOf('/') + 1)..]);
+			// a link to a NodeInfo document under another rel (Funkwhale 2.0 names it after its swagger schema): its path
+			// says what it is, and its last segment the version
+			foreach (var link in list.EnumerateArray())
+				if (link.ValueKind == JsonValueKind.Object && Text(link, "href") is { } href && href.StartsWith("https://", StringComparison.OrdinalIgnoreCase)
+					&& Uri.TryCreate(href, UriKind.Absolute, out var target) && target.AbsolutePath.Contains("/nodeinfo", StringComparison.OrdinalIgnoreCase))
+					return (href, target.Segments[^1].Trim('/') is var last && Schemas.Any(s => s.EndsWith("/" + last, StringComparison.Ordinal)) ? last : "2.0");
 			return default;
 		}