1 files changed, 117 insertions, 0 deletions
diff --git a/lib/gitlab/markdown/user_reference_filter.rb b/lib/gitlab/markdown/user_reference_filter.rb
new file mode 100644
index 00000000000..eaf4094338b
--- /dev/null
+++ b/lib/gitlab/markdown/user_reference_filter.rb
@@ -0,0 +1,117 @@
+require 'html/pipeline'
+
+module Gitlab
+  module Markdown
+    # HTML filter that replaces user or group references with links. References
+    # within <pre>, <code>, <a>, and <style> elements are ignored.
+    #
+    # A special `@all` reference is also supported.
+    #
+    # Context options:
+    #   :project (required) - Current project.
+    #   :reference_class    - Custom CSS class added to reference links.
+    #   :only_path          - Generate path-only links.
+    #
+    class UserReferenceFilter < HTML::Pipeline::Filter
+      # 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_PATTERN) do |match|
+          yield match, $~[:user]
+        end
+      end
+
+      # Pattern used to extract `@user` user references from text
+      USER_PATTERN = /@(?<user>#{Gitlab::Regex::NAMESPACE_REGEX_STR})/
+
+      # Don't look for references in text nodes that are children of these
+      # elements.
+      IGNORE_PARENTS = %w(pre code a style).to_set
+
+      def call
+        doc.search('text()').each do |node|
+          content = node.to_html
+
+          next if project.nil?
+          next unless content.match(USER_PATTERN)
+          next if has_ancestor?(node, IGNORE_PARENTS)
+
+          html = user_link_filter(content)
+
+          next if html == content
+
+          node.replace(html)
+        end
+
+        doc
+      end
+
+      def validate
+        needs :project
+      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)
+        project = context[:project]
+
+        self.class.references_in(text) do |match, user|
+          klass = "gfm gfm-project_member #{context[:reference_class]}".strip
+
+          if user == 'all'
+            url = link_to_all(project)
+
+            %(<a href="#{url}" class="#{klass}">@#{user}</a>)
+          elsif namespace = Namespace.find_by(path: user)
+            if namespace.is_a?(Group)
+              url = group_url(user, only_path: context[:only_path])
+            else
+              url = user_url(user, only_path: context[:only_path])
+            end
+
+            %(<a href="#{url}" class="#{klass}">@#{user}</a>)
+          else
+            match
+          end
+        end
+      end
+
+      def project
+        context[:project]
+      end
+
+      # TODO (rspeicher): Cleanup
+      def group_url(*args)
+        h = Rails.application.routes.url_helpers
+        h.group_url(*args)
+      end
+
+      # TODO (rspeicher): Cleanup
+      def user_url(*args)
+        h = Rails.application.routes.url_helpers
+        h.user_url(*args)
+      end
+
+      # TODO (rspeicher): Cleanup
+      def link_to_all(project)
+        h = Rails.application.routes.url_helpers
+        h.namespace_project_url(project.namespace, project,
+                                only_path: context[:only_path])
+      end
+    end
+  end
+end