1 files changed, 37 insertions, 0 deletions
diff --git a/app/models/concerns/linkable_item.rb b/app/models/concerns/linkable_item.rb
new file mode 100644
index 00000000000..135252727ab
--- /dev/null
+++ b/app/models/concerns/linkable_item.rb
@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+# == LinkableItem concern
+#
+# Contains common functionality shared between related issue links and related work item links
+#
+# Used by IssueLink, WorkItems::RelatedWorkItemLink
+#
+module LinkableItem
+  extend ActiveSupport::Concern
+  include FromUnion
+  include IssuableLink
+
+  included do
+    validate :check_existing_parent_link
+
+    scope :for_source, ->(item) { where(source_id: item.id) }
+    scope :for_target, ->(item) { where(target_id: item.id) }
+    scope :for_items, ->(source, target) do
+      where(source: source, target: target).or(where(source: target, target: source))
+    end
+
+    private
+
+    def check_existing_parent_link
+      return unless source && target
+
+      existing_relation = WorkItems::ParentLink.for_parents([source, target]).for_children([source, target])
+      return if existing_relation.none?
+
+      errors.add(:source, format(_('is a parent or child of this %{item}'), item: self.class.issuable_name))
+    end
+  end
+end
+
+LinkableItem.include_mod_with('LinkableItem::Callbacks')
+LinkableItem.prepend_mod_with('LinkableItem')