module Middleman::Extensions::CacheBuster::InstanceMethods

def asset_url(path, prefix="")
  http_path = super
  if http_path.include?("://") || !%w(.css .png .jpg .jpeg .svg .svgz .js .gif).include?(File.extname(http_path))
    http_path
  else
    begin
      prefix = images_dir if prefix == http_images_path
    rescue
    end
    real_path_static = File.join(prefix, path)
  
    if build?
      real_path_dynamic = File.join(build_dir, prefix, path)
      real_path_dynamic = File.expand_path(real_path_dynamic, root)
      http_path << "?" + File.mtime(real_path_dynamic).strftime("%s") if File.readable?(real_path_dynamic)
    elsif sitemap.exists?(real_path_static)
      page = sitemap.page(real_path_static)
      if !page.template?
        http_path << "?" + File.mtime(result[0]).strftime("%s")
      else
        # It's a template, possible with partials. We can't really know when
        # it's updated, so generate fresh cache buster every time durin
        # developement
        http_path << "?" + Time.now.strftime("%s")
      end
    end
  
    http_path
  end
end