1 files changed, 35 insertions, 0 deletions
diff --git a/app/services/import_csv/preprocess_milestones_service.rb b/app/services/import_csv/preprocess_milestones_service.rb
new file mode 100644
index 00000000000..97fb381c58e
--- /dev/null
+++ b/app/services/import_csv/preprocess_milestones_service.rb
@@ -0,0 +1,35 @@
+# frozen_string_literal: true
+
+module ImportCsv
+  class PreprocessMilestonesService < BaseService
+    def initialize(user, project, provided_titles)
+      @user = user
+      @project = project
+      @provided_titles = provided_titles
+
+      @results = { success: 0, errors: nil }
+      @milestone_errors = { missing: { header: {}, titles: [] } }
+    end
+
+    attr_reader :user, :project, :provided_titles, :results, :milestone_errors
+
+    def execute
+      available_milestones = find_milestones_by_titles
+      return ServiceResponse.success if provided_titles.sort == available_milestones.sort
+
+      milestone_errors[:missing][:header] = 'Milestone'
+      milestone_errors[:missing][:titles] = provided_titles.difference(available_milestones) || []
+      ServiceResponse.error(message: "", payload: milestone_errors)
+    end
+
+    def find_milestones_by_titles
+      # Find if these milestones exist in the project or its group and group ancestors
+      finder_params = {
+        project_ids: [project.id],
+        title: provided_titles
+      }
+      finder_params[:group_ids] = project.group.self_and_ancestors.select(:id) if project.group
+      MilestonesFinder.new(finder_params).execute.map(&:title).uniq
+    end
+  end
+end