module Lookbook::WithPreviewControllerConcern

def preview_controller
  @_preview_controller ||= begin
    # In order to get URL helpers working correctly in the preview,
    # the request needs to look like it's coming from the host app,
    # not the Lookbook engine. So we try to get the controller and action
    # for the root path and use that as the 'fake' request context instead.
    path_parameters = begin
      request_path = main_app.respond_to?(:root_path) ? main_app.root_path : "/"
      Rails.application.routes.recognize_path(request_path)
    rescue
      # Fix for authenticated devise paths
      if main_app.respond_to?(:new_user_session_path)
        Rails.application.routes.recognize_path(main_app.new_user_session_path)
      end
    end
    preview_request = request.clone
    preview_request.path_parameters = path_parameters if path_parameters.present?
    controller = Engine.preview_controller.new
    controller.request = preview_request
    controller.response = response
    controller
  end
end