module ActionView::Helpers::AssetTagHelper
  alias_method :rails_javascript_include_tag, :javascript_include_tag
  
  # Adds a new option to Rails' built-in <tt>javascript_include_tag</tt>
  # helper - <tt>:unobtrusive</tt>. Works in the same way as <tt>:defaults</tt> - specifying 
  # <tt>:unobtrusive</tt> will make sure the necessary javascript
  # libraries and behaviours file +script+ tags are loaded. Will happily
  # work along side <tt>:defaults</tt>.
  #
  #  <%= javascript_include_tag :defaults, :unobtrusive %>
  #
  # This replaces the old +unobtrusive_javascript_files+ helper.
  def javascript_include_tag(*sources)
    main_sources, application_source = [], []
    if sources.include?(:unobtrusive)
      sources.delete(:unobtrusive)
      sources.push('prototype') unless sources.include?(:defaults)
      sources.push('lowpro')
      behaviours_url = content_tag("script", "", { "type" => "text/javascript", "src" => UnobtrusiveJavascript::Settings.behaviours_url })
    end
    unless sources.empty?
      main_sources = rails_javascript_include_tag(*sources).split("\n") 
      application_source = main_sources.pop if main_sources.last.include?('application.js')
    end
    [main_sources.join("\n"), behaviours_url, application_source].join("\n")
  end
end