perf: preload organiser roles to eliminate N+1 queries in event_organiser?

app/presenters/member_presenter.rb

@@ -4,7 +4,10 @@ def organiser?
   end
 
   def event_organiser?(event)
-    has_role?(:organiser, event) || has_role?(:organiser, event.chapter) || has_role?(:admin)
+    event_types = %w[Workshop Meeting Event]
+    organising_events.slice(*event_types).values.any? { |ids| ids.include?(event.id) } ||
+      (event.chapter && organising_events['Chapter']&.include?(event.chapter.id)) ||
+      admin?
   end
 
   def newbie?
@@ -33,6 +36,17 @@ def displayed_dietary_restrictions
 
   private
 
+  def organising_events
+    @organised_events ||= roles.where(name: 'organiser')
+                               .pluck(:resource_type, :resource_id)
+                               .group_by(&:first)
+                               .transform_values { |pairs| pairs.map(&:last) }
+  end
+
+  def admin?
+    @is_admin ||= has_role?(:admin)
+  end
+
   def coach_pairing_details(note)
     [newbie?, full_name, 'Coach', 'N/A', note, skill_list.to_s]
   end

spec/presenters/member_presenter_spec.rb

@@ -38,4 +38,68 @@
       expect(member_presenter.attending?(event)).to be false
     end
   end
+
+  describe '#event_organiser?' do
+    let(:chapter) { Fabricate(:chapter) }
+    let(:workshop) { Fabricate(:workshop_no_sponsor, chapter: chapter) }
+
+    it 'returns true when user is admin' do
+      admin = Fabricate(:member)
+      admin.add_role(:admin)
+      presenter = MemberPresenter.new(admin)
+
+      expect(presenter.event_organiser?(workshop)).to be true
+    end
+
+    it 'returns true when user is direct organiser of the event' do
+      member.add_role(:organiser, workshop)
+
+      expect(member_presenter.event_organiser?(workshop)).to be true
+    end
+
+    it 'returns true when user is organiser of the event chapter' do
+      organiser = Fabricate(:member)
+      organiser.add_role(:organiser, chapter)
+      presenter = MemberPresenter.new(organiser)
+
+      expect(presenter.event_organiser?(workshop)).to be true
+    end
+
+    it 'returns false for a regular member' do
+      regular = Fabricate(:member)
+      presenter = MemberPresenter.new(regular)
+
+      expect(presenter.event_organiser?(workshop)).to be false
+    end
+
+    it 'returns false for organiser of a different chapter' do
+      other_chapter = Fabricate(:chapter)
+      other_workshop = Fabricate(:workshop_no_sponsor, chapter: other_chapter)
+      organiser = Fabricate(:member)
+      organiser.add_role(:organiser, other_chapter)
+      presenter = MemberPresenter.new(organiser)
+
+      expect(presenter.event_organiser?(workshop)).to be false
+    end
+
+    it 'handles events without a singular chapter association (e.g. Meeting) without crashing' do
+      meeting = Fabricate(:meeting)
+      meeting_presenter = MeetingPresenter.new(meeting)
+      admin = Fabricate(:member)
+      admin.add_role(:admin)
+      presenter = MemberPresenter.new(admin)
+
+      expect(presenter.event_organiser?(meeting_presenter)).to be true
+    end
+
+    it 'memoizes private methods across calls' do
+      member.add_role(:admin)
+
+      expect(member).to receive(:has_role?).with(:admin).once.and_call_original
+      # First call loads and caches
+      member_presenter.event_organiser?(workshop)
+      # Second call uses cache
+      member_presenter.event_organiser?(workshop)
+    end
+  end
 end