i18n_js.rb

# Hi! I'am rack middleware!
# I was born for return to you valid js on json i18n objects

# My author's name was Aleksandr Koss. Mail him at kossnocorp@gmail.com
# Nice to MIT you!

class I18nJs
  def initialize app, options = {}
    @app = app
    @options = options
  end  
    
  def call env
    # Valid url is /i18n-<i18n key>-<locale>.<format> where
    # i18n key - yaml branch named "locale.key"
    # locale - locale as is
    # format - js or json

    if data_array = env['PATH_INFO'].scan( \
                    /^\/i18n-(\w+)-(\w{1,3})[.](js[on]*)$/)[0]

      key, locale, type = data_array

      # Return if :accepted_keys not :all and 
      # not included in :accepted_keys array

      return @app.call env if \
        @options[:accepted_keys] and
        @options[:accepted_keys] != :all and
        not @options[:accepted_keys].include? key.to_sym # Key don't accepted

      # Get yaml branch by key

      json = YAML::load(
                File.open(File.dirname(__FILE__) + 
                "/../config/locales/#{locale}.yml"
              ))[locale][key].to_json

      return @app.call env if json == 'null' # Branch not found

      content_type, response = type == 'js' ?
        ['application/javascript', "var i18n_#{key} = [#{json}];"] :
        ['application/json', json]
        
      [200, {'Content-Type' => content_type}, [response]]
    else
      @app.call env
    end
  end  
end