Implement validation logic to ProjectStage

- Introducting StageEvents to define the available events
- Define the event pairing rules, since some events are not compatible
- Express default Cycle Analytics stages with the event structure

1 files changed, 68 insertions, 0 deletions

diff --git a/app/models/concerns/analytics/cycle_analytics/stage.rb b/app/models/concerns/analytics/cycle_analytics/stage.rb
new file mode 100644
index 00000000000..0c603c2d5e6
--- /dev/null
+++ b/app/models/concerns/analytics/cycle_analytics/stage.rb
@@ -0,0 +1,68 @@
+# frozen_string_literal: true
+
+module Analytics
+  module CycleAnalytics
+    module Stage
+      extend ActiveSupport::Concern
+
+      included do
+        validates :name, presence: true
+        validates :start_event_identifier, presence: true
+        validates :end_event_identifier, presence: true
+        validate :validate_stage_event_pairs
+
+        enum start_event_identifier: Gitlab::Analytics::CycleAnalytics::StageEvents.to_enum, _prefix: :start_event_identifier
+        enum end_event_identifier: Gitlab::Analytics::CycleAnalytics::StageEvents.to_enum, _prefix: :end_event_identifier
+
+        alias_attribute :custom_stage?, :custom
+      end
+
+      def parent=(_)
+        raise NotImplementedError
+      end
+
+      def parent
+        raise NotImplementedError
+      end
+
+      def start_event
+        Gitlab::Analytics::CycleAnalytics::StageEvents[start_event_identifier].new(params_for_start_event)
+      end
+
+      def end_event
+        Gitlab::Analytics::CycleAnalytics::StageEvents[end_event_identifier].new(params_for_end_event)
+      end
+
+      def params_for_start_event
+        {}
+      end
+
+      def params_for_end_event
+        {}
+      end
+
+      def default_stage?
+        !custom
+      end
+
+      # The model that is going to be queried, Issue or MergeRequest
+      def subject_model
+        start_event.object_type
+      end
+
+      private
+
+      def validate_stage_event_pairs
+        return if start_event_identifier.nil? || end_event_identifier.nil?
+
+        unless pairing_rules.fetch(start_event.class, []).include?(end_event.class)
+          errors.add(:end_event, :not_allowed_for_the_given_start_event)
+        end
+      end
+
+      def pairing_rules
+        Gitlab::Analytics::CycleAnalytics::StageEvents.pairing_rules
+      end
+    end
+  end
+end