Merge pull request #18 from alphagov/modulize

Make publishing event pipeline more modular

lib/publishing_event_pipeline.rb

@@ -0,0 +1,17 @@
+require "publishing_event_pipeline/configuration"
+require "publishing_event_pipeline/document"
+require "publishing_event_pipeline/document_lifecycle_event"
+
+require "publishing_event_pipeline/message_processor"
+
+require "publishing_event_pipeline/repositories/null_repository"
+
+module PublishingEventPipeline
+  def self.configuration
+    @configuration ||= Configuration.new
+  end
+
+  def self.configure
+    yield(configuration)
+  end
+end

lib/publishing_event_pipeline/configuration.rb

@@ -0,0 +1,9 @@
+module PublishingEventPipeline
+  class Configuration
+    attr_accessor :logger, :repository
+
+    def initialize
+      @logger = Logger.new($stdout)
+    end
+  end
+end

lib/publishing_event_pipeline/document_lifecycle_event.rb

@@ -1,5 +1,3 @@
-require_relative "document"
-
 module PublishingEventPipeline
   # Domain model for a content change event coming through from a publishing system
   class DocumentLifecycleEvent

lib/publishing_event_pipeline/message_processor.rb

@@ -1,14 +1,11 @@
-require_relative "document_lifecycle_event"
-require_relative "repositories/null_repository"
-
 module PublishingEventPipeline
   # Processes incoming content changes from the publishing message queue.
   class MessageProcessor
     attr_reader :event_class, :repository
 
     def initialize(
       event_class: DocumentLifecycleEvent,
-      repository: Repositories::NullRepository.new
+      repository: PublishingEventPipeline.configuration.repository
     )
       @event_class = event_class
       @repository = repository

lib/publishing_event_pipeline/repositories/null_repository.rb

@@ -1,5 +1,3 @@
-require_relative "../document"
-
 module PublishingEventPipeline
   module Repositories
     # A repository that does nothing, for use until we can integrate with the real product.

lib/tasks/publishing_event_pipeline.rake

@@ -1,12 +1,20 @@
 require "govuk_message_queue_consumer"
+require "publishing_event_pipeline"
 
-require "publishing_event_pipeline/message_processor"
-
+# TODO: For now, this lives within the application repository, but we may want to extract it to a
+#   completely separate unit if we can keep dependencies between the read and write sides of this
+#   project to a minimum. This isn't something that is 100% clear at this stage.
+#
+# Until then, these tasks intentionally run outside the Rails environment to avoid us adding any
+# implicit dependencies on the Rails application.
+#
+# rubocop:disable Rails/RakeEnvironment
 namespace :publishing_event_pipeline do
   desc "Create RabbitMQ queue for development environment"
-  task create_queue: :environment do
+  task :create_queue do
     # The exchange, queue, and binding are created via Terraform outside of local development:
     # https://github.com/alphagov/govuk-aws/blob/main/terraform/projects/app-publishing-amazonmq/
+    # TODO: Remove dependency on Rails if extracted to a separate unit
     raise "This task should only be run in development" unless Rails.env.development?
 
     bunny = Bunny.new
@@ -16,10 +24,18 @@ namespace :publishing_event_pipeline do
   end
 
   desc "Listens to and processes messages from the published documents queue"
-  task process_messages: :environment do
+  task :process_messages do
+    PublishingEventPipeline.configure do |config|
+      # TODO: Once we have access to the search product and written a repository for it, this should
+      #  be set to the real repository. Until then, this allows us to verify that the pipeline is
+      #  working as expected through the logs.
+      config.repository = PublishingEventPipeline::Repositories::NullRepository.new
+    end
+
     GovukMessageQueueConsumer::Consumer.new(
       queue_name: ENV.fetch("PUBLISHING_EVENT_MESSAGE_QUEUE_NAME"),
       processor: PublishingEventPipeline::MessageProcessor.new,
     ).run
   end
 end
+# rubocop:enable Rails/RakeEnvironment

spec/lib/publishing_event_pipeline/document_lifecycle_event_spec.rb

@@ -1,5 +1,3 @@
-require "publishing_event_pipeline/document_lifecycle_event"
-
 RSpec.describe PublishingEventPipeline::DocumentLifecycleEvent do
   subject(:event) { described_class.new(message_hash) }
 

spec/lib/publishing_event_pipeline/message_processor_spec.rb

@@ -1,5 +1,3 @@
-require "publishing_event_pipeline/message_processor"
-
 require "govuk_message_queue_consumer"
 require "govuk_message_queue_consumer/test_helpers"
 

spec/lib/publishing_event_pipeline/repositories/null_repository_spec.rb

@@ -1,5 +1,3 @@
-require "publishing_event_pipeline/repositories/null_repository"
-
 RSpec.describe PublishingEventPipeline::Repositories::NullRepository do
   let(:repository) { described_class.new }
   let(:content_id) { "some_content_id" }

spec/spec_helper.rb

@@ -9,6 +9,13 @@
 Dir[Rails.root.join("spec/support/**/*.rb")].each { |f| require f }
 GovukTest.configure
 
+# TODO: If the write side of this application is extracted to a separate unit, we will need to
+#   remove this, otherwise it can be made permanent.
+require "publishing_event_pipeline"
+PublishingEventPipeline.configure do |config|
+  config.repository = PublishingEventPipeline::Repositories::NullRepository.new
+end
+
 # See https://rubydoc.info/gems/rspec-core/RSpec/Core/Configuration
 RSpec.configure do |config|
   config.default_formatter = "doc" if config.files_to_run.one?