module RefinerycmsVarnish
  module PageExtension

    def self.included(base)
      base.after_save :purge_page
      base.after_destroy :purge_page
      
      base.class_eval do
        
        private
        def purge_page
          
          if  ((self.respond_to?(:title_changed?) and self.title_changed?) or self.link_url_changed?) and self.show_in_menu

            # it seems that attributes possibly relevant to other pages have changed
            # -> we expire all urls
            ActionController::Base.purge "/", true

          elsif self.link_url and self.link_url.starts_with?("/")

            # by now we assume that no attributes relevant to other pages have
            # changed -> we expire this page only
            ActionController::Base.purge self.link_url

          else

            # by now we know that there is no link_url -> we expire this page only
            ActionController::Base.purge "/#{self.slug.name}"

          end
        end
        
      end
    end
    
  end
end