Local content item support

app.json

@@ -2,6 +2,9 @@
   "name": "Frontend",
   "repository": "https://github.com/alphagov/frontend",
   "env": {
+    "ALLOW_LOCAL_CONTENT_ITEM_OVERRIDE": {
+      "value": "true"
+    },
     "GOVUK_APP_DOMAIN": {
       "value": "www.gov.uk"
     },

app/controllers/calendar_controller.rb

@@ -40,6 +40,10 @@ def division
 
   helper_method :calendar
 
+  def content_item_path
+    "/#{params[:slug]}"
+  end
+
   def set_cors_headers
     headers["Access-Control-Allow-Origin"] = "*"
   end

app/controllers/content_items_controller.rb

@@ -22,21 +22,17 @@ def publication_class
   end
 
   def content_item
-    @content_item ||= ContentItemFactory.build(request.env[:content_item] || request_content_item(content_item_slug || "/#{params[:slug]}"))
+    @content_item ||= ContentItemFactory.build(ContentItemLoader.load(content_item_path))
   end
 
-  def content_item_slug
+  def content_item_path
     request.path
   end
 
   def content_item_hash
     @content_item_hash ||= content_item.to_h
   end
 
-  def request_content_item(base_path = "/#{params[:slug]}")
-    GdsApi.content_store.content_item(base_path)
-  end
-
   # NOTE: Frontend honours the max-age directive  provided
   # in Content Store's Cache-Control response header.
   def set_expiry(expiry = nil)

app/controllers/electoral_controller.rb

@@ -26,7 +26,7 @@ def publication_class
     LocalTransactionPresenter
   end
 
-  def content_item_slug
+  def content_item_path
     BASE_PATH_OF_EXISTING_CONTACT_LOCAL_ERO_SERVICE
   end
 

app/controllers/error_controller.rb

@@ -1,6 +1,8 @@
 class ErrorController < ApplicationController
   def handler
-    # defer any errors to be handled in ApplicationController
-    raise request.env[:content_item_error]
+    # We know at this point that the ContentItemLoader has stored
+    # an exception to deal with, so just retrieve it and raise it
+    # to be handled in ApplicationController
+    raise ContentItemLoader.load(request.path)
   end
 end

app/controllers/find_local_council_controller.rb

@@ -52,7 +52,7 @@ def result
 
 private
 
-  def content_item_slug
+  def content_item_path
     BASE_PATH
   end
 

app/controllers/help_controller.rb

@@ -26,10 +26,4 @@ def sign_in
       },
     ]
   end
-
-private
-
-  def content_item_slug
-    request.path
-  end
 end

app/controllers/help_page_controller.rb

@@ -1,9 +1,2 @@
 class HelpPageController < ContentItemsController
-  def show; end
-
-private
-
-  def content_item_slug
-    request.path
-  end
 end

app/controllers/landing_page_controller.rb

@@ -5,9 +5,16 @@ class LandingPageController < ContentItemsController
 
   # SCAFFOLDING: can be removed when basic content items are available
   # from content-store
-  def request_content_item(_base_path)
-    GdsApi.content_store.content_item(request.path).to_h
-  rescue StandardError
+  def content_item
+    @content_item ||= ContentItemFactory.build(old_scaffolding_content_item)
+  end
+
+  # SCAFFOLDING: can be removed when basic content items are available
+  # from content-store
+  def old_scaffolding_content_item
+    result = ContentItemLoader.load(request.path)
+    return result.to_h if result.is_a?(GdsApi::Response)
+
     fake_data
   end
 

app/controllers/licence_transaction_controller.rb

@@ -74,7 +74,7 @@ def redirect_to_continuation_licence
     end
   end
 
-  def content_item_slug
+  def content_item_path
     "/find-licences/#{params[:slug]}"
   end
 

app/controllers/local_transaction_controller.rb

@@ -54,6 +54,10 @@ def translated_slug
     local_authority_slug
   end
 
+  def content_item_path
+    "/#{params[:slug]}"
+  end
+
   def publication_class
     LocalTransactionPresenter
   end

app/controllers/simple_smart_answers_controller.rb

@@ -25,6 +25,10 @@ def flow
     :smart_answer_path_for_responses,
   )
 
+  def content_item_path
+    "/#{params[:slug]}"
+  end
+
   def publication_class
     SimpleSmartAnswerPresenter
   end

app/controllers/transaction_controller.rb

@@ -11,6 +11,10 @@ def show
 
 private
 
+  def content_item_path
+    "/#{params[:slug]}"
+  end
+
   def publication_class
     TransactionPresenter
   end

app/controllers/travel_advice_controller.rb

@@ -23,7 +23,7 @@ def index
   # These objects duplicate roles (see `presenter || @publication`) in views.
   def publication; end
 
-  def content_item_slug
+  def content_item_path
     "/#{FOREIGN_TRAVEL_ADVICE_SLUG}"
   end
 end

docs/local-content-items.md

@@ -0,0 +1,11 @@
+# Local Content Items
+
+For local development and preview apps, it is sometimes desirable to have the ability to load content items that are specified locally rather than pointing to production/integration or having the content store running locally.
+
+To support this, set:
+
+`ALLOW_LOCAL_CONTENT_ITEM_OVERRIDE=true`
+
+...in your environment.
+
+With that environment variable set, the ContentItemLoader will add an additional check when loading a content item from the content store. Before making the GdsApi content store call, it will look in config/local-content-items/ for a JSON or YAML file matching the path of the content item (for instance, if you're looking for /find-licences/my-licence, it will look for config/local-content-items/find-licences/my-licence.json, then config/local-content-items/find-licences/my-licence.yml)

lib/api_error_routing_constraint.rb

@@ -1,5 +1,5 @@
 class ApiErrorRoutingConstraint
   def matches?(request)
-    request.env[:content_item_error].present?
+    ContentItemLoader.load(request.path).is_a?(StandardError)
   end
 end

lib/content_item_loader.rb

@@ -0,0 +1,53 @@
+require "ostruct"
+
+class ContentItemLoader
+  LOCAL_ITEMS_PATH = "lib/data/local-content-items".freeze
+
+  @cache = {}
+
+  class << self
+    attr_reader :cache
+
+    def load(base_path)
+      cache[base_path] ||= if use_local_file? && File.exist?(yaml_filename(base_path))
+                             Rails.logger.debug("Loading content item #{base_path} from #{yaml_filename(base_path)}")
+                             load_yaml_file(base_path)
+                           elsif use_local_file? && File.exist?(json_filename(base_path))
+                             Rails.logger.debug("Loading content item #{base_path} from #{json_filename(base_path)}")
+                             load_json_file(base_path)
+                           else
+                             begin
+                               GdsApi.content_store.content_item(base_path)
+                             rescue GdsApi::HTTPErrorResponse, GdsApi::InvalidUrl => e
+                               e
+                             end
+                           end
+    end
+
+  private
+
+    def use_local_file?
+      ENV["ALLOW_LOCAL_CONTENT_ITEM_OVERRIDE"] == "true"
+    end
+
+    def yaml_filename(base_path)
+      Rails.root.join("#{LOCAL_ITEMS_PATH}#{base_path}.yml")
+    end
+
+    def load_yaml_file(base_path)
+      GdsApi::Response.new(OpenStruct.new(code: 200, body: YAML.load(File.read(yaml_filename(base_path))).to_json, headers:))
+    end
+
+    def json_filename(base_path)
+      Rails.root.join("#{LOCAL_ITEMS_PATH}#{base_path}.json")
+    end
+
+    def load_json_file(base_path)
+      GdsApi::Response.new(OpenStruct.new(code: 200, body: File.read(json_filename(base_path)), headers:))
+    end
+
+    def headers
+      { cache_control: "max-age=0, public", expires: "" }
+    end
+  end
+end

lib/format_routing_constraint.rb

@@ -4,27 +4,12 @@ def initialize(format)
   end
 
   def matches?(request)
-    content_item = set_content_item(request)
-    @format == content_item&.[]("schema_name")
-  end
-
-  def set_content_item(request)
-    return request.env[:content_item] if already_cached?(request)
-
-    begin
-      request.env[:content_item] = GdsApi.content_store.content_item(key(request))
-    rescue GdsApi::HTTPErrorResponse, GdsApi::InvalidUrl => e
-      request.env[:content_item_error] = e
-      nil
-    end
+    content_item = ContentItemLoader.load(key(request))
+    content_item.is_a?(GdsApi::Response) && content_item["schema_name"] == @format
   end
 
 private
 
-  def already_cached?(request)
-    request.env.include?(:content_item) || request.env.include?(:content_item_error)
-  end
-
   def key(request)
     "/#{request.params.fetch(:slug)}"
   end

lib/full_path_format_routing_constraint.rb

@@ -1,10 +1,6 @@
 class FullPathFormatRoutingConstraint < FormatRoutingConstraint
 private
 
-  def already_cached?(_request)
-    false
-  end
-
   def key(request)
     request.path
   end

spec/fixtures/local-content-items/my-json-item.json

@@ -0,0 +1,3 @@
+{
+  "schema_name": "json_page"
+}

spec/fixtures/local-content-items/my-yaml-item.yml

@@ -0,0 +1 @@
+schema_name: yaml_page

spec/spec_helper.rb

@@ -21,6 +21,12 @@
   config.infer_spec_type_from_file_location!
   config.include FactoryBot::Syntax::Methods
 
+  config.include ContentItemLoaderHelpers
+
+  config.before(:each) do
+    clear_content_item_loader_cache
+  end
+
   config.include ContentStoreHelpers, type: :request
   config.include ContentStoreHelpers, type: :system
 

spec/support/content_item_loader_helpers.rb

@@ -0,0 +1,5 @@
+module ContentItemLoaderHelpers
+  def clear_content_item_loader_cache
+    ContentItemLoader.cache.each_key { |key| ContentItemLoader.cache.delete(key) }
+  end
+end

spec/support/meta_tags.rb

@@ -7,6 +7,7 @@
     )
     example_doc["links"]["available_translations"] = []
 
+    clear_content_item_loader_cache
     stub_content_store_has_item(path, example_doc.to_json)
   end
 
@@ -28,6 +29,7 @@
     )
     example_doc["links"]["available_translations"] = []
 
+    clear_content_item_loader_cache
     stub_content_store_has_item(path, example_doc.to_json)
   end
 

spec/unit/api_error_routing_constraint_spec.rb

@@ -1,21 +1,18 @@
-require "api_error_routing_constraint"
-
 RSpec.describe ApiErrorRoutingConstraint do
+  include ContentStoreHelpers
+
+  let(:subject) { described_class.new }
+  let(:request) { double(path: "/slug") }
+
   it "returns true if there's a cached error" do
-    request = double(env: { content_item_error: StandardError.new })
+    stub_content_store_does_not_have_item("/slug")
 
     expect(subject.matches?(request)).to be true
   end
 
   it "returns false if there was no error in API calls" do
-    request = double(env: {})
+    stub_content_store_has_item("/slug")
 
     expect(subject.matches?(request)).to be false
   end
-
-private
-
-  def subject
-    ApiErrorRoutingConstraint.new
-  end
 end