Add new API endpoint to expose single environment

This is resolving https://gitlab.com/gitlab-org/gitlab-ce/issues/30157.

Implement new API endpoint `/projects/:id/environments/:environment_id`
to expose single environment. Include information for environment's last
deployment if there is one.

2 files changed, 20 insertions, 4 deletions

diff --git a/lib/api/entities.rb b/lib/api/entities.rb
index 2dd3120d3fc..f9773086f69 100644
--- a/lib/api/entities.rb
+++ b/lib/api/entities.rb
@@ -1294,10 +1294,6 @@ module API
       expose :id, :name, :slug, :external_url
     end
 
-    class Environment < EnvironmentBasic
-      expose :project, using: Entities::BasicProjectDetails
-    end
-
     class Deployment < Grape::Entity
       expose :id, :iid, :ref, :sha, :created_at
       expose :user,        using: Entities::UserBasic
@@ -1305,6 +1301,11 @@ module API
       expose :deployable,  using: Entities::Job
     end
 
+    class Environment < EnvironmentBasic
+      expose :project, using: Entities::BasicProjectDetails
+      expose :last_deployment, using: Entities::Deployment, if: { last_deployment: true }
+    end
+
     class LicenseBasic < Grape::Entity
       expose :key, :name, :nickname
       expose :url, as: :html_url
diff --git a/lib/api/environments.rb b/lib/api/environments.rb
index 5b0f3b914cb..6cd43923559 100644
--- a/lib/api/environments.rb
+++ b/lib/api/environments.rb
@@ -101,6 +101,21 @@ module API
         status 200
         present environment, with: Entities::Environment, current_user: current_user
       end
+
+      desc 'Get a single environment' do
+        success Entities::Environment
+      end
+      params do
+        requires :environment_id, type: Integer, desc: 'The environment ID'
+      end
+      get ':id/environments/:environment_id' do
+        authorize! :read_environment, user_project
+
+        environment = user_project.environments.find(params[:environment_id])
+        present environment, with: Entities::Environment, current_user: current_user,
+                             except: [:project, { last_deployment: [:environment] }],
+                             last_deployment: true
+      end
     end
   end
 end