Document presenters

Signed-off-by: Rémy Coutable <remy@rymai.me>

2 files changed, 71 insertions, 0 deletions

diff --git a/lib/gitlab/view/presenter.rb b/lib/gitlab/view/presenter.rb
new file mode 100644
index 00000000000..8b63b271b99
--- /dev/null
+++ b/lib/gitlab/view/presenter.rb
@@ -0,0 +1,32 @@
+module Gitlab
+  module View
+    module Presenter
+      extend ActiveSupport::Concern
+
+      included do
+        include Gitlab::Routing
+        include Gitlab::Allowable
+      end
+
+      def with_subject(subject)
+        tap { @subject = subject }
+      end
+
+      def with_user(user)
+        tap { @user = user }
+      end
+
+      private
+
+      attr_reader :subject, :user
+
+      class_methods do
+        def presents(name)
+          define_method(name) do
+            subject
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/view/presenter_factory.rb b/lib/gitlab/view/presenter_factory.rb
new file mode 100644
index 00000000000..c8cab1249da
--- /dev/null
+++ b/lib/gitlab/view/presenter_factory.rb
@@ -0,0 +1,39 @@
+module Gitlab
+  module View
+    class PresenterFactory
+      def initialize(subject, user: nil)
+        @subject = subject
+        @user = user
+      end
+
+      def fabricate!
+        presenter =
+          if presenter_class.ancestors.include?(SimpleDelegator)
+            delegator_presenter
+          else
+            simple_presenter
+          end
+
+        presenter
+          .with_subject(subject)
+          .with_user(user)
+      end
+
+      private
+
+      attr_reader :subject, :user
+
+      def presenter_class
+        "#{subject.class.name.demodulize}Presenter".constantize
+      end
+
+      def delegator_presenter
+        presenter_class.new(subject)
+      end
+
+      def simple_presenter
+        presenter_class.new
+      end
+    end
+  end
+end