1 files changed, 129 insertions, 0 deletions
diff --git a/lib/banzai/filter/user_reference_filter.rb b/lib/banzai/filter/user_reference_filter.rb
new file mode 100644
index 00000000000..67c24faf991
--- /dev/null
+++ b/lib/banzai/filter/user_reference_filter.rb
@@ -0,0 +1,129 @@
+require 'banzai'
+
+module Banzai
+  module Filter
+    # HTML filter that replaces user or group references with links.
+    #
+    # A special `@all` reference is also supported.
+    class UserReferenceFilter < ReferenceFilter
+      # Public: Find `@user` user references in text
+      #
+      #   UserReferenceFilter.references_in(text) do |match, username|
+      #     "<a href=...>@#{user}</a>"
+      #   end
+      #
+      # text - String text to search.
+      #
+      # Yields the String match, and the String user name.
+      #
+      # Returns a String replaced with the return of the block.
+      def self.references_in(text)
+        text.gsub(User.reference_pattern) do |match|
+          yield match, $~[:user]
+        end
+      end
+
+      def self.referenced_by(node)
+        if node.has_attribute?('data-group')
+          group = Group.find(node.attr('data-group')) rescue nil
+          return unless group
+
+          { user: group.users }
+        elsif node.has_attribute?('data-user')
+          { user: LazyReference.new(User, node.attr('data-user')) }
+        elsif node.has_attribute?('data-project')
+          project = Project.find(node.attr('data-project')) rescue nil
+          return unless project
+
+          { user: project.team.members.flatten }
+        end
+      end
+
+      def self.user_can_reference?(user, node, context)
+        if node.has_attribute?('data-group')
+          group = Group.find(node.attr('data-group')) rescue nil
+          Ability.abilities.allowed?(user, :read_group, group)
+        else
+          super
+        end
+      end
+
+      def call
+        replace_text_nodes_matching(User.reference_pattern) do |content|
+          user_link_filter(content)
+        end
+
+        replace_link_nodes_with_href(User.reference_pattern) do |link, text|
+          user_link_filter(link, link_text: text)
+        end
+      end
+
+      # Replace `@user` user references in text with links to the referenced
+      # user's profile page.
+      #
+      # text - String text to replace references in.
+      #
+      # Returns a String with `@user` references replaced with links. All links
+      # have `gfm` and `gfm-project_member` class names attached for styling.
+      def user_link_filter(text, link_text: nil)
+        self.class.references_in(text) do |match, username|
+          if username == 'all'
+            link_to_all(link_text: link_text)
+          elsif namespace = Namespace.find_by(path: username)
+            link_to_namespace(namespace, link_text: link_text) || match
+          else
+            match
+          end
+        end
+      end
+
+      private
+
+      def urls
+        Gitlab::Application.routes.url_helpers
+      end
+
+      def link_class
+        reference_class(:project_member)
+      end
+
+      def link_to_all(link_text: nil)
+        project = context[:project]
+        url = urls.namespace_project_url(project.namespace, project,
+                                         only_path: context[:only_path])
+        data = data_attribute(project: project.id)
+        text = link_text || User.reference_prefix + 'all'
+
+        link_tag(url, data, text)
+      end
+
+      def link_to_namespace(namespace, link_text: nil)
+        if namespace.is_a?(Group)
+          link_to_group(namespace.path, namespace, link_text: link_text)
+        else
+          link_to_user(namespace.path, namespace, link_text: link_text)
+        end
+      end
+
+      def link_to_group(group, namespace, link_text: nil)
+        url = urls.group_url(group, only_path: context[:only_path])
+        data = data_attribute(group: namespace.id)
+        text = link_text || Group.reference_prefix + group
+
+        link_tag(url, data, text)
+      end
+
+      def link_to_user(user, namespace, link_text: nil)
+        url = urls.user_url(user, only_path: context[:only_path])
+        data = data_attribute(user: namespace.owner_id)
+        text = link_text || User.reference_prefix + user
+
+        link_tag(url, data, text)
+      end
+
+      def link_tag(url, data, text)
+        %(<a href="#{url}" #{data} class="#{link_class}">#{text}</a>)
+      end
+    end
+  end
+end