Improved remote thread fetching (#10106)

* Fetch up to 5 replies when discovering a new remote status

This is used for resolving threads downwards. The originating
server must add a “replies” attributes with such replies for it to
be useful.

* Add some tests for ActivityPub::FetchRepliesWorker

* Add specs for ActivityPub::FetchRepliesService

* Serialize up to 5 public self-replies for ActivityPub notes

* Add specs for ActivityPub::NoteSerializer

* Move exponential backoff logic to a worker concern

* Fetch first page of paginated collections when fetching thread replies

* Add specs for paginated collections in replies

* Move Note replies serialization to a first CollectionPage

The collection isn't actually paginable yet as it has no id nor
a `next` field. This may come in another PR.

* Use pluck(:uri) instead of map(&:uri) to improve performances

* Fix fetching replies when they are in a CollectionPage

1 files changed, 10 insertions, 0 deletions

diff --git a/app/lib/activitypub/activity/create.rb b/app/lib/activitypub/activity/create.rb
index 6d58aba70..0980f94ba 100644
--- a/app/lib/activitypub/activity/create.rb
+++ b/app/lib/activitypub/activity/create.rb
@@ -40,6 +40,7 @@ class ActivityPub::Activity::Create < ActivityPub::Activity
     end
 
     resolve_thread(@status)
+    fetch_replies(@status)
     distribute(@status)
     forward_for_reply if @status.public_visibility? || @status.unlisted_visibility?
   end
@@ -213,6 +214,15 @@ class ActivityPub::Activity::Create < ActivityPub::Activity
     ThreadResolveWorker.perform_async(status.id, in_reply_to_uri)
   end
 
+  def fetch_replies(status)
+    collection = @object['replies']
+    return if collection.nil?
+    replies = ActivityPub::FetchRepliesService.new.call(status, collection, false)
+    return if replies.present?
+    uri = value_or_id(collection)
+    ActivityPub::FetchRepliesWorker.perform_async(status.id, uri) unless uri.nil?
+  end
+
   def conversation_from_uri(uri)
     return nil if uri.nil?
     return Conversation.find_by(id: OStatus::TagManager.instance.unique_tag_to_local_id(uri, 'Conversation')) if OStatus::TagManager.instance.local_id?(uri)