1 files changed, 62 insertions, 0 deletions
diff --git a/lib/banzai/filter/custom_emoji_filter.rb b/lib/banzai/filter/custom_emoji_filter.rb
new file mode 100644
index 00000000000..1ee8f4e31e8
--- /dev/null
+++ b/lib/banzai/filter/custom_emoji_filter.rb
@@ -0,0 +1,62 @@
+# frozen_string_literal: true
+
+module Banzai
+  module Filter
+    class CustomEmojiFilter < HTML::Pipeline::Filter
+      IGNORED_ANCESTOR_TAGS = %w(pre code tt).to_set
+
+      def call
+        return doc unless context[:project]
+        return doc unless Feature.enabled?(:custom_emoji, context[:project])
+
+        doc.search(".//text()").each do |node|
+          content = node.to_html
+
+          next if has_ancestor?(node, IGNORED_ANCESTOR_TAGS)
+          next unless content.include?(':')
+          next unless namespace && namespace.custom_emoji.any?
+
+          html = custom_emoji_name_element_filter(content)
+
+          node.replace(html) unless html == content
+        end
+
+        doc
+      end
+
+      def custom_emoji_pattern
+        @emoji_pattern ||=
+          /(?<=[^[:alnum:]:]|\n|^)
+          :(#{CustomEmoji::NAME_REGEXP}):
+          (?=[^[:alnum:]:]|$)/x
+      end
+
+      def custom_emoji_name_element_filter(text)
+        text.gsub(custom_emoji_pattern) do |match|
+          name = Regexp.last_match[1]
+          custom_emoji = all_custom_emoji[name]
+
+          if custom_emoji
+            Gitlab::Emoji.custom_emoji_tag(custom_emoji.name, custom_emoji.url)
+          else
+            match
+          end
+        end
+      end
+
+      private
+
+      def namespace
+        context[:project].namespace.root_ancestor
+      end
+
+      def custom_emoji_candidates
+        doc.to_html.scan(/:(#{CustomEmoji::NAME_REGEXP}):/).flatten
+      end
+
+      def all_custom_emoji
+        @all_custom_emoji ||= namespace.custom_emoji.by_name(custom_emoji_candidates).index_by(&:name)
+      end
+    end
+  end
+end