1 files changed, 52 insertions, 0 deletions
diff --git a/lib/gitlab/metrics/dashboard/validator/post_schema_validator.rb b/lib/gitlab/metrics/dashboard/validator/post_schema_validator.rb
new file mode 100644
index 00000000000..73bfc5a6294
--- /dev/null
+++ b/lib/gitlab/metrics/dashboard/validator/post_schema_validator.rb
@@ -0,0 +1,52 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Metrics
+    module Dashboard
+      module Validator
+        class PostSchemaValidator
+          def initialize(metric_ids:, project: nil, dashboard_path: nil)
+            @metric_ids = metric_ids
+            @project = project
+            @dashboard_path = dashboard_path
+          end
+
+          def validate
+            errors = []
+            errors << uniq_metric_ids
+            errors.compact
+          end
+
+          private
+
+          attr_reader :project, :metric_ids, :dashboard_path
+
+          def uniq_metric_ids
+            return Validator::Errors::DuplicateMetricIds.new if metric_ids.uniq!
+
+            uniq_metric_ids_across_project if project.present? || dashboard_path.present?
+          end
+
+          # rubocop: disable CodeReuse/ActiveRecord
+          def uniq_metric_ids_across_project
+            return ArgumentError.new(_('Both project and dashboard_path are required')) unless
+              dashboard_path.present? && project.present?
+
+            # If PrometheusMetric identifier is not unique across project and dashboard_path,
+            # we need to error because we don't know if the user is trying to create a new metric
+            # or update an existing one.
+            identifier_on_other_dashboard = PrometheusMetric.where(
+              project: project,
+              identifier: metric_ids
+            ).where.not(
+              dashboard_path: dashboard_path
+            ).exists?
+
+            Validator::Errors::DuplicateMetricIds.new if identifier_on_other_dashboard
+          end
+          # rubocop: enable CodeReuse/ActiveRecord
+        end
+      end
+    end
+  end
+end