1 files changed, 55 insertions, 0 deletions
diff --git a/app/graphql/mutations/boards/lists/base_create.rb b/app/graphql/mutations/boards/lists/base_create.rb
new file mode 100644
index 00000000000..a21c7feece3
--- /dev/null
+++ b/app/graphql/mutations/boards/lists/base_create.rb
@@ -0,0 +1,55 @@
+# frozen_string_literal: true
+
+module Mutations
+  module Boards
+    module Lists
+      class BaseCreate < BaseMutation
+        argument :backlog, GraphQL::BOOLEAN_TYPE,
+                 required: false,
+                 description: 'Create the backlog list.'
+
+        argument :label_id, ::Types::GlobalIDType[::Label],
+                 required: false,
+                 description: 'Global ID of an existing label.'
+
+        def ready?(**args)
+          if args.slice(*mutually_exclusive_args).size != 1
+            arg_str = mutually_exclusive_args.map { |x| x.to_s.camelize(:lower) }.join(' or ')
+            raise Gitlab::Graphql::Errors::ArgumentError, "one and only one of #{arg_str} is required"
+          end
+
+          super
+        end
+
+        def resolve(**args)
+          board  = authorized_find!(id: args[:board_id])
+          params = create_list_params(args)
+
+          response = create_list(board, params)
+
+          {
+            list: response.success? ? response.payload[:list] : nil,
+            errors: response.errors
+          }
+        end
+
+        private
+
+        def create_list(board, params)
+          raise NotImplementedError
+        end
+
+        def create_list_params(args)
+          params = args.slice(*mutually_exclusive_args).with_indifferent_access
+          params[:label_id] &&= ::GitlabSchema.parse_gid(params[:label_id], expected_type: ::Label).model_id
+
+          params
+        end
+
+        def mutually_exclusive_args
+          [:backlog, :label_id]
+        end
+      end
+    end
+  end
+end