1 files changed, 51 insertions, 0 deletions
diff --git a/app/serializers/group_child_serializer.rb b/app/serializers/group_child_serializer.rb
new file mode 100644
index 00000000000..2baef0a5703
--- /dev/null
+++ b/app/serializers/group_child_serializer.rb
@@ -0,0 +1,51 @@
+class GroupChildSerializer < BaseSerializer
+  include WithPagination
+
+  attr_reader :hierarchy_root, :should_expand_hierarchy
+
+  entity GroupChildEntity
+
+  def expand_hierarchy(hierarchy_root = nil)
+    @hierarchy_root = hierarchy_root
+    @should_expand_hierarchy = true
+
+    self
+  end
+
+  def represent(resource, opts = {}, entity_class = nil)
+    if should_expand_hierarchy
+      paginator.paginate(resource) if paginated?
+      represent_hierarchies(resource, opts)
+    else
+      super(resource, opts)
+    end
+  end
+
+  protected
+
+  def represent_hierarchies(children, opts)
+    if children.is_a?(GroupDescendant)
+      represent_hierarchy(children.hierarchy(hierarchy_root), opts).first
+    else
+      hierarchies = GroupDescendant.build_hierarchy(children, hierarchy_root)
+      # When an array was passed, we always want to represent an array.
+      # Even if the hierarchy only contains one element
+      represent_hierarchy(Array.wrap(hierarchies), opts)
+    end
+  end
+
+  def represent_hierarchy(hierarchy, opts)
+    serializer = self.class.new(params)
+
+    if hierarchy.is_a?(Hash)
+      hierarchy.map do |parent, children|
+        serializer.represent(parent, opts)
+          .merge(children: Array.wrap(serializer.represent_hierarchy(children, opts)))
+      end
+    elsif hierarchy.is_a?(Array)
+      hierarchy.flat_map { |child| serializer.represent_hierarchy(child, opts) }
+    else
+      serializer.represent(hierarchy, opts)
+    end
+  end
+end