Padrino Autolocale with "smart" redirect to default locale

auto_locale.rb

module Padrino
  module Contrib
    ##
    # This extension give to padrino the ability to change
    # their locale inspecting.
    #
    # ==== Usage
    #
    #   class MyApp < Padrino::Application
    #     register AutoLocale
    #     set :locales, [:en, :ru, :de] # First locale is the default locale
    #   end
    #
    #   # view.haml
    #   =link_to "View this page in RU Version", switch_to_lang(:ru)
    #
    # So when we call an url like: /ru/blog/posts this extension set for you :ru as I18n.locale
    #
    module AutoLocale
      def self.registered(app)
        app.helpers Padrino::Contrib::AutoLocale::Helpers
        app.extend ClassMethods
        app.set :locales, [:en]
        app.before do
          if request.path_info =~ /^\/(#{settings.locales.join('|')})\b/
            I18n.locale = $1.to_sym
          elsif I18n.locale && settings.locales.include?(I18n.locale)
            redirect "/#{I18n.locale}#{request.path_info}"
          else
            lang = I18n.locale = settings.locales[0]
            url = if request.path_info =~ /^\/[a-z]{2}(_[A-Z]{2})?\b/
              request.path_info.sub(/^\/[a-z]{2}(_[A-Z]{2})?\b/, "/#{lang}")
            else
              "/#{lang}#{request.path_info}"
            end
            redirect url
          end
        end

        def self.padrino_route_added(route, verb, path, args, options, block)
          route.instance_variable_set(:@original_path, "/:lang#{route.original_path}") unless route.original_path =~/:lang/
        end
      end

    end # AutoLocale
  end # Contrib
end # Padrino