class PageSweeper < ActionController::Caching::Sweeper
  observe Page, Slug

  def after_save model
    expire_cache model
  end

  def after_destroy model
    expire_cache model
  end

  private
  
    def expire_cache model
      case model.class.name.to_s
      when "Page"
        # only expire latest slug
        # in case title changes, it will trigger the expire_slug function from the observer
        expire_page "/#{model.slug.name}"
        
        # expire all cache if we change root page
        expire_dir nil if (model.parent_id.blank?)
      when "Slug"
        # expire from parent level down
        expire_parent_and_descendants model.name
      end
    end

    private
    
    # expire the parent directory and page
    def expire_parent_and_descendants slug
      expire_page parent_slug(slug)
      expire_dir parent_slug(slug)
    end
    
    # expire a whole cache directory
    def expire_dir dir
      cache_dir = ActionController::Base.page_cache_directory
      FileUtils.rm_rf Dir.glob("#{cache_dir}#{dir}") rescue Errno::ENOENT
      Rails.logger.info("Removed cache dir: #{cache_dir}#{dir}")
    end
    
    # why not split, pop and rejoin?
    def parent_slug slug
      if slug.sluggable_type == "Page"
        if slug.sluggable.root?
          slug
        else
          slug.sluggable.parent.slug.name
        end
      end
    end

end