Introduced ReviewAppSetup entity

Used new serializer in Environments controller.
Created review app snippet.
Refactored project logic into a new module.

app/controllers/concerns/review_app_setup.rb

+# frozen_string_literal: true
+
+module ReviewAppSetup
+  include Gitlab::Utils::StrongMemoize
+  include ChecksCollaboration
+
+  def can_setup_review_app?
+    strong_memoize(:can_setup_review_app?) do
+      cicd_missing? || (can_cluster_be_created? && cluster_missing?)
+    end
+  end
+
+  def cicd_missing?
+    current_user && can_current_user_push_code? && project.repository.gitlab_ci_yml.blank? && !project.auto_devops_enabled?
+  end
+
+  def can_cluster_be_created?
+    current_user && can?(current_user, :create_cluster, project)
+  end
+
+  def can_current_user_push_code?
+    strong_memoize(:can_current_user_push_code) do
+      if project.empty_repo?
+        can?(current_user, :push_code, project)
+      else
+        can_current_user_push_to_branch?(project.default_branch)
+      end
+    end
+  end
+
+  def cluster_missing?
+    strong_memoize(:cluster_missing?) do
+      project.clusters.blank?
+    end
+  end
+
+  def can_current_user_push_to_branch?(branch)
+    user_access(project).can_push_to_branch?(branch)
+  end
+end

app/controllers/projects/environments_controller.rb

@@ -32,6 +32,7 @@ class Projects::EnvironmentsController < Projects::ApplicationController
 
         render json: {
           environments: serialize_environments(request, response, params[:nested]),
+          review_app: serialize_review_app,
           available_count: project.environments.available.count,
           stopped_count: project.environments.stopped.count
         }
@@ -243,6 +244,10 @@ class Projects::EnvironmentsController < Projects::ApplicationController
       .represent(@environments)
   end
 
+  def serialize_review_app
+    ReviewAppSetupSerializer.new(current_user: @current_user).represent(@project)
+  end
+
   def authorize_stop_environment!
     access_denied! unless can?(current_user, :stop_environment, environment)
   end

app/presenters/project_presenter.rb

@@ -8,7 +8,7 @@ class ProjectPresenter < Gitlab::View::Presenter::Delegated
   include TreeHelper
   include IconsHelper
   include ChecksCollaboration
-  include Gitlab::Utils::StrongMemoize
+  include ReviewAppSetup
 
   presents :project
 
@@ -124,20 +124,6 @@ class ProjectPresenter < Gitlab::View::Presenter::Delegated
     license&.nickname || license&.name || 'LICENSE'
   end
 
-  def can_current_user_push_code?
-    strong_memoize(:can_current_user_push_code) do
-      if empty_repo?
-        can?(current_user, :push_code, project)
-      else
-        can_current_user_push_to_branch?(default_branch)
-      end
-    end
-  end
-
-  def can_current_user_push_to_branch?(branch)
-    user_access(project).can_push_to_branch?(branch)
-  end
-
   def can_current_user_push_to_default_branch?
     can_current_user_push_to_branch?(default_branch)
   end
@@ -293,7 +279,7 @@ class ProjectPresenter < Gitlab::View::Presenter::Delegated
   end
 
   def gitlab_ci_anchor_data
-    if can_cicd_be_set_up?
+    if cicd_missing?
       AnchorData.new(false,
                      statistic_icon + _('Set up CI/CD'),
                      add_ci_yml_path)
@@ -305,18 +291,6 @@ class ProjectPresenter < Gitlab::View::Presenter::Delegated
     end
   end
 
-  def can_setup_review_app?
-    can_cicd_be_set_up? || can_cluster_be_created?
-  end
-
-  def can_cicd_be_set_up?
-    current_user && can_current_user_push_code? && repository.gitlab_ci_yml.blank? && !auto_devops_enabled?
-  end
-
-  def can_cluster_be_created?
-    current_user && can?(current_user, :create_cluster, project)
-  end
-
   def topics_to_show
     project.tag_list.take(MAX_TOPICS_TO_SHOW) # rubocop: disable CodeReuse/ActiveRecord
   end

app/serializers/review_app_setup_entity.rb

+# frozen_string_literal: true
+
+class ReviewAppSetupEntity < Grape::Entity
+  include RequestAwareEntity
+  include ReviewAppSetup
+
+  expose :can_setup_review_app?
+
+  expose :cluster_missing?, if: -> (_, _) { can_setup_review_app? } do |project|
+    cluster_missing?
+  end
+
+  expose :review_snippet, if: -> (_, _) { can_setup_review_app? } do |_|
+    YAML.safe_load(File.read(Rails.root.join('lib', 'gitlab', 'ci', 'snippets', 'review_app_default.yml'))).inspect
+  end
+
+  private
+
+  def current_user
+    request.current_user
+  end
+
+  def project
+    object
+  end
+end

app/serializers/review_app_setup_serializer.rb

+# frozen_string_literal: true
+
+class ReviewAppSetupSerializer < BaseSerializer
+  entity ReviewAppSetupEntity
+end

app/views/projects/environments/index.html.haml

@@ -3,7 +3,6 @@
 #environments-list-view{ data: { environments_data: environments_list_data,
   "can-read-environment" => can?(current_user, :read_environment, @project).to_s,
   "can-create-environment" => can?(current_user, :create_environment, @project).to_s,
-  "can-setup-review-app" => @project.can_setup_review_app?,
   "new-environment-path" => new_project_environment_path(@project),
   "help-page-path" => help_page_path("ci/environments"),
   "deploy-boards-help-path" => help_page_path("user/project/deploy_boards", anchor: "enabling-deploy-boards") } }

lib/gitlab/ci/snippets/review_app_default.yml

+deploy_review:
+  stage: deploy
+  script:
+    - echo "Deploy a review app"
+  environment:
+    name: review/$CI_COMMIT_REF_NAME
+    url: https://$CI_ENVIRONMENT_SLUG.example.com
+  only:
+    - branches