1 files changed, 42 insertions, 0 deletions
diff --git a/lib/banzai/filter/kroki_filter.rb b/lib/banzai/filter/kroki_filter.rb
new file mode 100644
index 00000000000..dbd4de32a47
--- /dev/null
+++ b/lib/banzai/filter/kroki_filter.rb
@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+
+require "nokogiri"
+require "asciidoctor/extensions/asciidoctor_kroki/extension"
+
+module Banzai
+  module Filter
+    # HTML that replaces all diagrams supported by Kroki with the corresponding img tags.
+    #
+    class KrokiFilter < HTML::Pipeline::Filter
+      def call
+        return doc unless settings.kroki_enabled
+
+        diagram_selectors = ::Gitlab::Kroki.formats(settings)
+                                .map { |diagram_type| %(pre[lang="#{diagram_type}"] > code) }
+                                .join(', ')
+
+        return doc unless doc.at(diagram_selectors)
+
+        diagram_format = "svg"
+        doc.css(diagram_selectors).each do |node|
+          diagram_type = node.parent['lang']
+          img_tag = Nokogiri::HTML::DocumentFragment.parse(%(<img src="#{create_image_src(diagram_type, diagram_format, node.content)}"/>))
+          node.parent.replace(img_tag)
+        end
+
+        doc
+      end
+
+      private
+
+      def create_image_src(type, format, text)
+        ::AsciidoctorExtensions::KrokiDiagram.new(type, format, text)
+          .get_diagram_uri(settings.kroki_url)
+      end
+
+      def settings
+        Gitlab::CurrentSettings.current_application_settings
+      end
+    end
+  end
+end