routes

 Rails.application.routes.draw do
  scope ':locale', locale: /#{I18n.available_locales.join("|")}/ do
    resources :articles do
      collection do
        get 'custom_json', constraints: { format: :json }, defaults: { format: :json }
      end
    end
  
    get "*path", to: redirect("/#{I18n.default_locale}") # handles /en/fake/path/whatever
  end
  
  get '', to: redirect("/#{I18n.default_locale}") # handles /
  get '*path', to: redirect("/#{I18n.default_locale}/%{path}") # handles /not-a-locale/anything
end