lib/banzai/filter/plantuml_filter.rb


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# frozen_string_literal: true

require "nokogiri"
require "asciidoctor_plantuml/plantuml"

module Banzai
  module Filter
    # HTML that replaces all `lang plantuml` tags with PlantUML img tags.
    #
    class PlantumlFilter < HTML::Pipeline::Filter
      def call
        return doc unless settings.plantuml_enabled? && doc.at_xpath(lang_tag)

        plantuml_setup

        doc.xpath(lang_tag).each do |node|
          img_tag = Nokogiri::HTML::DocumentFragment.parse(
            Asciidoctor::PlantUml::Processor.plantuml_content(node.content, {})).css('img').first

          unless img_tag.nil?
            img_tag.set_attribute('data-diagram', 'plantuml')
            img_tag.set_attribute('data-diagram-src', "data:text/plain;base64,#{Base64.strict_encode64(node.content)}")

            node.parent.replace(img_tag)
          end
        end

        doc
      end

      private

      def lang_tag
        @lang_tag ||= Gitlab::Utils::Nokogiri
          .css_to_xpath('pre[lang="plantuml"] > code, pre > code[lang="plantuml"]').freeze
      end

      def settings
        Gitlab::CurrentSettings.current_application_settings
      end

      def plantuml_setup
        Asciidoctor::PlantUml.configure do |conf|
          conf.url = settings.plantuml_url
          conf.png_enable = settings.plantuml_enabled
          conf.svg_enable = false
          conf.txt_enable = false
        end
      end
    end
  end
end