1 files changed, 74 insertions, 0 deletions
diff --git a/lib/gitlab/background_migration/user_mentions/models/concerns/namespace/recursive_traversal.rb b/lib/gitlab/background_migration/user_mentions/models/concerns/namespace/recursive_traversal.rb
new file mode 100644
index 00000000000..5cadfa45b5b
--- /dev/null
+++ b/lib/gitlab/background_migration/user_mentions/models/concerns/namespace/recursive_traversal.rb
@@ -0,0 +1,74 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module BackgroundMigration
+    module UserMentions
+      module Models
+        module Concerns
+          module Namespace
+            # extracted methods for recursive traversing of namespace hierarchy
+            module RecursiveTraversal
+              extend ActiveSupport::Concern
+
+              def root_ancestor
+                return self if persisted? && parent_id.nil?
+
+                strong_memoize(:root_ancestor) do
+                  Gitlab::ObjectHierarchy
+                    .new(self.class.where(id: id))
+                    .base_and_ancestors
+                    .reorder(nil)
+                    .find_by(parent_id: nil)
+                end
+              end
+
+              # Returns all ancestors, self, and descendants of the current namespace.
+              def self_and_hierarchy
+                Gitlab::ObjectHierarchy
+                  .new(self.class.where(id: id))
+                  .all_objects
+              end
+
+              # Returns all the ancestors of the current namespaces.
+              def ancestors
+                return self.class.none unless parent_id
+
+                Gitlab::ObjectHierarchy
+                  .new(self.class.where(id: parent_id))
+                  .base_and_ancestors
+              end
+
+              # returns all ancestors upto but excluding the given namespace
+              # when no namespace is given, all ancestors upto the top are returned
+              def ancestors_upto(top = nil, hierarchy_order: nil)
+                Gitlab::ObjectHierarchy.new(self.class.where(id: id))
+                  .ancestors(upto: top, hierarchy_order: hierarchy_order)
+              end
+
+              def self_and_ancestors(hierarchy_order: nil)
+                return self.class.where(id: id) unless parent_id
+
+                Gitlab::ObjectHierarchy
+                  .new(self.class.where(id: id))
+                  .base_and_ancestors(hierarchy_order: hierarchy_order)
+              end
+
+              # Returns all the descendants of the current namespace.
+              def descendants
+                Gitlab::ObjectHierarchy
+                  .new(self.class.where(parent_id: id))
+                  .base_and_descendants
+              end
+
+              def self_and_descendants
+                Gitlab::ObjectHierarchy
+                  .new(self.class.where(id: id))
+                  .base_and_descendants
+              end
+            end
+          end
+        end
+      end
+    end
+  end
+end