1 files changed, 80 insertions, 0 deletions
diff --git a/lib/banzai/filter/emoji_filter.rb b/lib/banzai/filter/emoji_filter.rb
new file mode 100644
index 00000000000..86838e1483c
--- /dev/null
+++ b/lib/banzai/filter/emoji_filter.rb
@@ -0,0 +1,80 @@
+require 'action_controller'
+require 'banzai'
+require 'gitlab_emoji'
+require 'html/pipeline/filter'
+
+module Banzai
+  module Filter
+    # HTML filter that replaces :emoji: with images.
+    #
+    # Based on HTML::Pipeline::EmojiFilter
+    #
+    # Context options:
+    #   :asset_root
+    #   :asset_host
+    class EmojiFilter < HTML::Pipeline::Filter
+      IGNORED_ANCESTOR_TAGS = %w(pre code tt).to_set
+
+      def call
+        search_text_nodes(doc).each do |node|
+          content = node.to_html
+          next unless content.include?(':')
+          next if has_ancestor?(node, IGNORED_ANCESTOR_TAGS)
+
+          html = emoji_image_filter(content)
+
+          next if html == content
+
+          node.replace(html)
+        end
+
+        doc
+      end
+
+      # Replace :emoji: with corresponding images.
+      #
+      # text - String text to replace :emoji: in.
+      #
+      # Returns a String with :emoji: replaced with images.
+      def emoji_image_filter(text)
+        text.gsub(emoji_pattern) do |match|
+          name = $1
+          "<img class='emoji' title=':#{name}:' alt=':#{name}:' src='#{emoji_url(name)}' height='20' width='20' align='absmiddle' />"
+        end
+      end
+
+      private
+
+      def emoji_url(name)
+        emoji_path = "emoji/#{emoji_filename(name)}"
+        if context[:asset_host]
+          # Asset host is specified.
+          url_to_image(emoji_path)
+        elsif context[:asset_root]
+          # Gitlab url is specified
+          File.join(context[:asset_root], url_to_image(emoji_path))
+        else
+          # All other cases
+          url_to_image(emoji_path)
+        end
+      end
+
+      def url_to_image(image)
+        ActionController::Base.helpers.url_to_image(image)
+      end
+
+      # Build a regexp that matches all valid :emoji: names.
+      def self.emoji_pattern
+        @emoji_pattern ||= /:(#{Emoji.emojis_names.map { |name| Regexp.escape(name) }.join('|')}):/
+      end
+
+      def emoji_pattern
+        self.class.emoji_pattern
+      end
+
+      def emoji_filename(name)
+        "#{Emoji.emoji_filename(name)}.png"
+      end
+    end
+  end
+end