Docinfo Processor Extension Example

class GoogleAnalyticsDocinfoProcessor < Asciidoctor::Extensions::DocinfoProcessor
  use_dsl
  at_location :footer
  def process document
    return unless (ga_account_id = document.attr 'google-analytics-account')
    %(<script>
(function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
(i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
})(window,document,'script','https://www.google-analytics.com/analytics.js','ga');
ga('create','#{ga_account_id}','auto');
ga('send','pageview');
</script>)
  end
end

Asciidoctor::Extensions.register do
  docinfo_processor GoogleAnalyticsDocinfoProcessor
end

Asciidoctor.convert_file 'sample.adoc', safe: :safe, attributes: 'UA-ABCXYZ123'