Cache the wall of fame body with a daily key

app/controllers/dashboard_controller.rb

@@ -31,17 +31,41 @@ def faq; end
   def about; end
 
   def wall_of_fame
-    @coaches_count = WorkshopInvitation.to_coaches.attended.distinct.count(:member_id)
-    coaches = Member.where(id: top_coach_query
-                               .year(year_param))
-                    .includes(:skills)
-    @pagy, @coaches = pagy(coaches)
+    options = past_year? ? {} : { expires_in: 24.hours }
+    body = Rails.cache.fetch(wall_of_fame_cache_key, **options) { render_wall_of_fame_body }
+    # rubocop:disable Rails/OutputSafety
+    render html: body.html_safe, layout: 'application'
+    # rubocop:enable Rails/OutputSafety
   end
 
   def participant_guide; end
 
   private
 
+  def past_year?
+    (2013...Time.zone.today.year).cover?(year_param)
+  end
+
+  def wall_of_fame_cache_key
+    # Match pagy's page coercion so the cache key and the rendered page always
+    # agree, and arbitrary strings cannot expand the key space.
+    page = [params[:page].to_s.to_i, 1].max
+    date_segment = past_year? ? nil : "#{Time.zone.today}/"
+    "coaches/wall_of_fame/v2/#{date_segment}#{year_param}/#{page}/#{I18n.locale}"
+  end
+
+  def render_wall_of_fame_body
+    @coaches_count = WorkshopInvitation.to_coaches.attended.distinct.count(:member_id)
+    coaches = Member.where(id: top_coach_query
+                               .year(year_param))
+                    .includes(:skills)
+    # pagy copies every request param into pagination links; keep only the
+    # year the links must preserve so the filling request's junk params are
+    # not frozen into the cached body.
+    @pagy, @coaches = pagy(coaches, querify: ->(params) { params.keep_if { |k, _| %w[year page].include?(k) } })
+    render_to_string(layout: false)
+  end
+
   def year_param
     params.permit(:year)[:year]&.to_i || Time.zone.today.year
   end

spec/controllers/dashboard_controller_spec.rb

@@ -28,4 +28,112 @@ def assigns(symbol)
       expect(assigns(:coaches).first.name).to start_with('Coach')
     end
   end
+
+  describe 'GET #wall_of_fame caching' do
+    render_views
+
+    around do |example|
+      original_cache = Rails.cache
+      Rails.cache = ActiveSupport::Cache::MemoryStore.new
+      example.run
+      Rails.cache = original_cache
+    end
+
+    let!(:workshop) { Fabricate(:workshop, date_and_time: Time.zone.now) }
+
+    before do
+      Fabricate(:attended_coach,
+                member: Fabricate(:member, name: 'Cached', surname: 'Coach'),
+                workshop:)
+    end
+
+    it 'stores the current-year body for 24 hours under a date, year, page, and locale key' do
+      expected_key = "coaches/wall_of_fame/v2/#{Time.zone.today}/#{Time.zone.now.year}/1/en"
+
+      allow(Rails.cache).to receive(:fetch)
+        .with(expected_key, expires_in: 24.hours)
+        .and_call_original
+
+      get :wall_of_fame
+
+      expect(response.body).to include('Cached Coach')
+      expect(response.body).to include('<!DOCTYPE html')
+      expect(Rails.cache).to have_received(:fetch)
+        .with(expected_key, expires_in: 24.hours)
+      expect(Rails.cache.read(expected_key)).to be_present
+    end
+
+    it 'stores the past-year body without a date segment or explicit expiry' do
+      past_workshop = Fabricate(:workshop, date_and_time: Time.zone.local(2013, 6, 1))
+      Fabricate(:attended_coach,
+                member: Fabricate(:member, name: 'Cached', surname: 'Coach'),
+                workshop: past_workshop)
+      expected_key = 'coaches/wall_of_fame/v2/2013/1/en'
+
+      allow(Rails.cache).to receive(:fetch)
+        .with(expected_key)
+        .and_call_original
+
+      get :wall_of_fame, params: { year: 2013 }
+
+      expect(response.body).to include('Cached Coach')
+      expect(Rails.cache).to have_received(:fetch)
+        .with(expected_key)
+      expect(Rails.cache.read(expected_key)).to be_present
+    end
+
+    it 'serves junk years from a dated, expiring key' do
+      get :wall_of_fame, params: { year: 1999 }
+
+      base_key = "coaches/wall_of_fame/v2/#{Time.zone.today}"
+      expect(Rails.cache.read("#{base_key}/1999/1/en")).to be_present
+      expect(Rails.cache.read('coaches/wall_of_fame/v2/1999/1/en')).to be_nil
+    end
+
+    it 'serves the cached body without re-rendering from the database' do
+      get :wall_of_fame
+      expect(response.body).to include('Cached Coach')
+
+      WorkshopInvitation.where(member: Member.find_by(name: 'Cached')).destroy_all
+
+      get :wall_of_fame
+      expect(response.body).to include('Cached Coach')
+    end
+
+    it 'rotates the cache key with the year and page parameters' do
+      get :wall_of_fame
+      get :wall_of_fame, params: { year: 2013 }
+      get :wall_of_fame, params: { page: 2 }
+
+      expect(Rails.cache.read("coaches/wall_of_fame/v2/#{Time.zone.today}/#{Time.zone.now.year}/1/en")).to be_present
+      expect(Rails.cache.read('coaches/wall_of_fame/v2/2013/1/en')).to be_present
+      expect(Rails.cache.read("coaches/wall_of_fame/v2/#{Time.zone.today}/#{Time.zone.now.year}/2/en")).to be_present
+    end
+
+    it 'coerces non-numeric page values into the integer page for the cache key' do
+      get :wall_of_fame, params: { page: '3/de' }
+
+      base_key = "coaches/wall_of_fame/v2/#{Time.zone.today}"
+      expect(Rails.cache.read("#{base_key}/#{Time.zone.now.year}/3/en")).to be_present
+      # A page string cannot place one locale's body under another locale's key.
+      expect(Rails.cache.read("#{base_key}/#{Time.zone.now.year}/3/de")).to be_nil
+    end
+
+    it 'keeps unrelated query params out of the cached pagination links' do
+      21.times do |i|
+        Fabricate(:attended_coach,
+                  member: Fabricate(:member, name: "Wall#{i}", surname: 'Coach'),
+                  workshop:)
+      end
+
+      get :wall_of_fame, params: { fbclid: 'spam' }
+
+      # The layout's og:url mirrors the request URL and is never cached, so
+      # assert against the cached body itself.
+      base_key = "coaches/wall_of_fame/v2/#{Time.zone.today}"
+      cached = Rails.cache.read("#{base_key}/#{Time.zone.now.year}/1/en")
+      expect(cached).to include('page=2')
+      expect(cached).not_to include('fbclid')
+    end
+  end
 end