Add system note when timeline event created

When there is a new timeline event created, add a system note to the
incident

ee/app/helpers/ee/system_note_helper.rb

@@ -23,7 +23,8 @@ module EE
       'vulnerability_dismissed' => 'cancel',
       'vulnerability_resolved' => 'status_closed',
       'published' => 'bullhorn',
-      'paging_started' => 'mobile'
+      'paging_started' => 'mobile',
+      'timeline_event' => 'clock'
     }.freeze
 
     override :system_note_icon_name

ee/app/models/ee/system_note_metadata.rb

@@ -9,7 +9,7 @@ module EE
       epic_issue_added issue_added_to_epic epic_issue_removed issue_removed_from_epic
       epic_issue_moved issue_changed_epic epic_date_changed relate_epic unrelate_epic
       vulnerability_confirmed vulnerability_dismissed vulnerability_resolved vulnerability_detected
-      iteration paging_started
+      iteration paging_started timeline_event
     ].freeze
 
     EE_TYPES_WITH_CROSS_REFERENCES = %w[

ee/app/services/ee/system_note_service.rb

@@ -120,6 +120,10 @@ module EE
       escalations_service(noteable, noteable.project).start_escalation(escalation_policy, author)
     end
 
+    def add_timeline_event(timeline_event)
+      incidents_service(timeline_event.incident).add_timeline_event(timeline_event)
+    end
+
     private
 
     def issuables_service(noteable, project, author)
@@ -141,5 +145,9 @@ module EE
     def escalations_service(noteable, project)
       ::SystemNotes::EscalationsService.new(noteable: noteable, project: project)
     end
+
+    def incidents_service(incident)
+      ::SystemNotes::IncidentsService.new(noteable: incident)
+    end
   end
 end

ee/app/services/incident_management/timeline_events/create_service.rb

@@ -29,6 +29,8 @@ module IncidentManagement
         timeline_event = IncidentManagement::TimelineEvent.new(timeline_event_params)
 
         if timeline_event.save
+          add_system_note(timeline_event)
+
           success(timeline_event)
         else
           error_in_save(timeline_event)
@@ -38,6 +40,12 @@ module IncidentManagement
       private
 
       attr_reader :project, :user, :incident, :params
+
+      def add_system_note(timeline_event)
+        return unless Feature.enabled?(:incident_timeline, project, default_enabled: :yaml)
+
+        SystemNoteService.add_timeline_event(timeline_event)
+      end
     end
   end
 end

ee/app/services/system_notes/incidents_service.rb

+# frozen_string_literal: true
+
+module SystemNotes
+  class IncidentsService < ::SystemNotes::BaseService
+    def initialize(noteable:)
+      @noteable = noteable
+      @project = noteable.project
+    end
+
+    def add_timeline_event(timeline_event)
+      author = timeline_event.author
+      anchor = "timeline_event_#{timeline_event.id}"
+      path = url_helpers.project_issues_incident_path(project, noteable, anchor: anchor)
+      body = "added an [incident timeline event](#{path})"
+
+      create_note(NoteSummary.new(noteable, project, author, body, action: 'timeline_event'))
+    end
+  end
+end

ee/spec/models/ee/system_note_metadata_spec.rb

@@ -5,6 +5,7 @@ require 'spec_helper'
 RSpec.describe EE::SystemNoteMetadata do
   %i[
     vulnerability_confirmed vulnerability_dismissed vulnerability_resolved vulnerability_detected
+    timeline_event
   ].each do |action|
     context 'when action type is valid' do
       subject do

ee/spec/services/incident_management/timeline_events/create_service_spec.rb

@@ -105,5 +105,25 @@ RSpec.describe IncidentManagement::TimelineEvents::CreateService do
     it 'successfully creates a database record', :aggregate_failures do
       expect { execute }.to change { ::IncidentManagement::TimelineEvent.count }.by(1)
     end
+
+    context 'when incident_timeline feature flag is enabled' do
+      before do
+        stub_feature_flags(incident_timeline: project)
+      end
+
+      it 'creates a system note' do
+        expect { execute }.to change { incident.notes.reload.count }.by(1)
+      end
+    end
+
+    context 'when incident_timeline feature flag is disabled' do
+      before do
+        stub_feature_flags(incident_timeline: false)
+      end
+
+      it 'does not create a system note' do
+        expect { execute }.not_to change { incident.notes.reload.count }
+      end
+    end
   end
 end

ee/spec/services/system_note_service_spec.rb

@@ -173,4 +173,16 @@ RSpec.describe SystemNoteService do
       described_class.start_escalation(noteable, policy, author)
     end
   end
+
+  describe '.add_timeline_event' do
+    let(:timeline_event) { instance_double('IncidentManagement::TimelineEvent', incident: noteable, project: project) }
+
+    it 'calls IncidentsService' do
+      expect_next_instance_of(::SystemNotes::IncidentsService) do |service|
+        expect(service).to receive(:add_timeline_event).with(timeline_event)
+      end
+
+      described_class.add_timeline_event(timeline_event)
+    end
+  end
 end

ee/spec/services/system_notes/incidents_service_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe SystemNotes::IncidentsService do
+  include Gitlab::Routing
+
+  let_it_be(:project) { create(:project) }
+  let_it_be(:user) { create(:user) }
+  let_it_be(:author) { create(:user) }
+  let_it_be(:incident) { create(:incident, project: project, author: user) }
+  let_it_be(:timeline_event) { create(:incident_management_timeline_event, project: project, incident: incident, author: author) }
+
+  describe "#add_timeline_event" do
+    subject { described_class.new(noteable: incident).add_timeline_event(timeline_event) }
+
+    it_behaves_like 'a system note' do
+      let(:noteable) { incident }
+      let(:action) { 'timeline_event' }
+    end
+
+    it 'poses the correct text to the system note' do
+      path = project_issues_incident_path(project, incident, anchor: "timeline_event_#{timeline_event.id}")
+      expect(subject.note).to match("added an [incident timeline event](#{path})")
+    end
+  end
+end