1 files changed, 48 insertions, 0 deletions
diff --git a/app/services/activitypub/fetch_remote_status_service.rb b/app/services/activitypub/fetch_remote_status_service.rb
new file mode 100644
index 000000000..68ca58d62
--- /dev/null
+++ b/app/services/activitypub/fetch_remote_status_service.rb
@@ -0,0 +1,48 @@
+# frozen_string_literal: true
+
+class ActivityPub::FetchRemoteStatusService < BaseService
+  include JsonLdHelper
+
+  # Should be called when uri has already been checked for locality
+  def call(uri, prefetched_json = nil)
+    @json = body_to_json(prefetched_json) || fetch_resource(uri)
+
+    return unless supported_context?
+
+    activity = activity_json
+    actor_id = value_or_id(activity['actor'])
+
+    return unless expected_type?(activity) && trustworthy_attribution?(uri, actor_id)
+
+    actor = ActivityPub::TagManager.instance.uri_to_resource(actor_id, Account)
+    actor = ActivityPub::FetchRemoteAccountService.new.call(actor_id) if actor.nil?
+
+    ActivityPub::Activity.factory(activity, actor).perform
+  end
+
+  private
+
+  def activity_json
+    if %w(Note Article).include? @json['type']
+      {
+        'type'   => 'Create',
+        'actor'  => first_of_value(@json['attributedTo']),
+        'object' => @json,
+      }
+    else
+      @json
+    end
+  end
+
+  def trustworthy_attribution?(uri, attributed_to)
+    Addressable::URI.parse(uri).normalized_host.casecmp(Addressable::URI.parse(attributed_to).normalized_host).zero?
+  end
+
+  def supported_context?
+    super(@json)
+  end
+
+  def expected_type?(json)
+    %w(Create Announce).include? json['type']
+  end
+end