Add status references support

app/services/activitypub/fetch_references_service.rb

@@ -0,0 +1,49 @@
+# frozen_string_literal: true
+
+class ActivityPub::FetchReferencesService < BaseService
+  include JsonLdHelper
+
+  def call(status, collection_or_uri)
+    @account = status.account
+
+    collection_items(collection_or_uri)&.map { |item| value_or_id(item) }
+  end
+
+  private
+
+  def collection_items(collection_or_uri)
+    collection = fetch_collection(collection_or_uri)
+    return unless collection.is_a?(Hash) && collection['first'].present?
+
+    all_items = []
+    collection = fetch_collection(collection['first'])
+
+    while collection.is_a?(Hash)
+      items = begin
+        case collection['type']
+        when 'Collection', 'CollectionPage'
+          collection['items']
+        when 'OrderedCollection', 'OrderedCollectionPage'
+          collection['orderedItems']
+        end
+      end
+
+      break if items.blank?
+
+      all_items.concat(items)
+
+      break if all_items.size >= StatusReferenceValidator::LIMIT
+
+      collection = collection['next'].present? ? fetch_collection(collection['next']) : nil
+    end
+
+    all_items
+  end
+
+  def fetch_collection(collection_or_uri)
+    return collection_or_uri if collection_or_uri.is_a?(Hash)
+    return if invalid_origin?(collection_or_uri)
+
+    fetch_resource_without_id_validation(collection_or_uri, nil, true)
+  end
+end