Merge pull request #1400 from alphagov/related-links-header-response

Use request header for related links to determine response header

app/controllers/content_items_controller.rb

@@ -115,7 +115,10 @@ def set_access_control_allow_origin_header
 
   def set_use_recommended_related_links_header
     response.headers['Vary'] = [response.headers['Vary'], FeatureFlagNames.recommended_related_links].compact.join(', ')
-    response.headers[FeatureFlagNames.recommended_related_links] = Services.feature_toggler.feature_flags.get_feature_flag(FeatureFlagNames.recommended_related_links)
+
+    related_links_request_header = RequestHelper.get_header(FeatureFlagNames.recommended_related_links, request.headers)
+    required_header_value = Services.feature_toggler.feature_flags.get_feature_flag(FeatureFlagNames.recommended_related_links)
+    response.headers[FeatureFlagNames.recommended_related_links] = (related_links_request_header == required_header_value).to_s
   end
 
   def set_expiry

app/lib/request_helper.rb

@@ -0,0 +1,9 @@
+module RequestHelper
+  def self.get_header(header_name, request_headers)
+    request_headers[headerise(header_name)]
+  end
+
+  def self.headerise(header_name)
+    "HTTP_#{header_name.upcase.tr('-', '_')}"
+  end
+end

app/models/http_feature_flags.rb

@@ -4,24 +4,18 @@ def initialize
   end
 
   def add_http_feature_flag(feature_flag_name, val)
-    @feature_flags[get_header_name(feature_flag_name)] = val
+    @feature_flags[RequestHelper.headerise(feature_flag_name)] = val
   end
 
   def get_feature_flag(feature_flag_name)
-    @feature_flags[get_header_name(feature_flag_name)]
+    @feature_flags[RequestHelper.headerise(feature_flag_name)]
   end
 
   def feature_enabled?(feature_flag_name, request_headers)
-    get_feature_flag(feature_flag_name) == request_headers[get_header_name(feature_flag_name)]
+    get_feature_flag(feature_flag_name) == RequestHelper.get_header(feature_flag_name, request_headers)
   end
 
   def self.instance
     @instance ||= HttpFeatureFlags.new
   end
-
-private
-
-  def get_header_name(feature_flag_name)
-    "HTTP_#{feature_flag_name.upcase.tr('-', '_')}"
-  end
 end

test/controllers/content_items_controller_test.rb

@@ -178,18 +178,19 @@ class ContentItemsControllerTest < ActionController::TestCase
     assert_equal assigns[:content_item].content_item['links']['ordered_related_items'], content_item['links']['suggested_ordered_related_items']
   end
 
-  test "sets the Govuk-Use-Recommended-Links header to true when using recommended links" do
+  test "sets the Govuk-Use-Recommended-Links response header to false when request header is not set" do
     HttpFeatureFlags.instance.add_http_feature_flag(FeatureFlagNames.recommended_related_links, 'true')
     content_item = content_store_has_schema_example('case_study', 'case_study')
 
     get :show, params: { path: path_for(content_item) }
 
     assert_includes response.headers['Vary'], FeatureFlagNames.recommended_related_links
-    assert_equal 'true', response.headers[FeatureFlagNames.recommended_related_links]
+    assert_equal 'false', response.headers[FeatureFlagNames.recommended_related_links]
   end
 
-  test "sets the Govuk-Use-Recommended-Links header to false when not using recommended links" do
-    HttpFeatureFlags.instance.add_http_feature_flag(FeatureFlagNames.recommended_related_links, 'false')
+  test "sets the Govuk-Use-Recommended-Links response header to false when request header is set to false" do
+    HttpFeatureFlags.instance.add_http_feature_flag(FeatureFlagNames.recommended_related_links, 'true')
+    request.headers["HTTP_GOVUK_USE_RECOMMENDED_RELATED_LINKS"] = 'false'
     content_item = content_store_has_schema_example('case_study', 'case_study')
 
     get :show, params: { path: path_for(content_item) }
@@ -198,6 +199,17 @@ class ContentItemsControllerTest < ActionController::TestCase
     assert_equal 'false', response.headers[FeatureFlagNames.recommended_related_links]
   end
 
+  test "sets the Govuk-Use-Recommended-Links response header to true when request header is set to true" do
+    HttpFeatureFlags.instance.add_http_feature_flag(FeatureFlagNames.recommended_related_links, 'true')
+    request.headers["HTTP_GOVUK_USE_RECOMMENDED_RELATED_LINKS"] = 'true'
+    content_item = content_store_has_schema_example('case_study', 'case_study')
+
+    get :show, params: { path: path_for(content_item) }
+
+    assert_includes response.headers['Vary'], FeatureFlagNames.recommended_related_links
+    assert_equal 'true', response.headers[FeatureFlagNames.recommended_related_links]
+  end
+
   test "sets the expiry as sent by content-store" do
     content_item = content_store_has_schema_example('coming_soon', 'coming_soon')
     content_store_has_item(content_item['base_path'], content_item, max_age: 20)

test/services/request_helper_test.rb

@@ -0,0 +1,23 @@
+require 'test_helper'
+
+class RequestHelperTest < ActiveSupport::TestCase
+  test 'get_header returns nil when header does not exist' do
+    header_val = RequestHelper.get_header('Govuk-Example-Header', {})
+
+    assert_equal nil, header_val
+  end
+
+  test 'get_header returns header when header exists' do
+    header_val = RequestHelper.get_header('Govuk-Example-Header', 'HTTP_GOVUK_EXAMPLE_HEADER' => 'this_is_a_test')
+
+    assert_equal 'this_is_a_test', header_val
+  end
+
+  test 'headerise returns header with HTTP prefix, no dashes and all uppercase' do
+    header_name = 'Govuk-Example-Header'
+
+    transformed_header_name = RequestHelper.headerise(header_name)
+
+    assert_equal 'HTTP_GOVUK_EXAMPLE_HEADER', transformed_header_name
+  end
+end