1 files changed, 115 insertions, 0 deletions
diff --git a/lib/banzai/filter/project_reference_filter.rb b/lib/banzai/filter/project_reference_filter.rb
new file mode 100644
index 00000000000..fd2a86a6d45
--- /dev/null
+++ b/lib/banzai/filter/project_reference_filter.rb
@@ -0,0 +1,115 @@
+module Banzai
+  module Filter
+    # HTML filter that replaces project references with links.
+    class ProjectReferenceFilter < ReferenceFilter
+      self.reference_type = :project
+
+      # Public: Find `namespace/project>` project references in text
+      #
+      #   ProjectReferenceFilter.references_in(text) do |match, project|
+      #     "<a href=...>#{project}></a>"
+      #   end
+      #
+      # text - String text to search.
+      #
+      # Yields the String match, and the String project name.
+      #
+      # Returns a String replaced with the return of the block.
+      def self.references_in(text)
+        text.gsub(Project.markdown_reference_pattern) do |match|
+          yield match, "#{$~[:namespace]}/#{$~[:project]}"
+        end
+      end
+
+      def call
+        ref_pattern = Project.markdown_reference_pattern
+        ref_pattern_start = /\A#{ref_pattern}\z/
+
+        nodes.each do |node|
+          if text_node?(node)
+            replace_text_when_pattern_matches(node, ref_pattern) do |content|
+              project_link_filter(content)
+            end
+          elsif element_node?(node)
+            yield_valid_link(node) do |link, inner_html|
+              if link =~ ref_pattern_start
+                replace_link_node_with_href(node, link) do
+                  project_link_filter(link, link_content: inner_html)
+                end
+              end
+            end
+          end
+        end
+
+        doc
+      end
+
+      # Replace `namespace/project>` project references in text with links to the referenced
+      # project page.
+      #
+      # text - String text to replace references in.
+      # link_content - Original content of the link being replaced.
+      #
+      # Returns a String with `namespace/project>` references replaced with links. All links
+      # have `gfm` and `gfm-project` class names attached for styling.
+      def project_link_filter(text, link_content: nil)
+        self.class.references_in(text) do |match, project_path|
+          cached_call(:banzai_url_for_object, match, path: [Project, project_path.downcase]) do
+            if project = projects_hash[project_path.downcase]
+              link_to_project(project, link_content: link_content) || match
+            else
+              match
+            end
+          end
+        end
+      end
+
+      # Returns a Hash containing all Project objects for the project
+      # references in the current document.
+      #
+      # The keys of this Hash are the project paths, the values the
+      # corresponding Project objects.
+      def projects_hash
+        @projects ||= Project.eager_load(:route, namespace: [:route])
+                             .where_full_path_in(projects)
+                             .index_by(&:full_path)
+                             .transform_keys(&:downcase)
+      end
+
+      # Returns all projects referenced in the current document.
+      def projects
+        refs = Set.new
+
+        nodes.each do |node|
+          node.to_html.scan(Project.markdown_reference_pattern) do
+            refs << "#{$~[:namespace]}/#{$~[:project]}"
+          end
+        end
+
+        refs.to_a
+      end
+
+      private
+
+      def urls
+        Gitlab::Routing.url_helpers
+      end
+
+      def link_class
+        reference_class(:project)
+      end
+
+      def link_to_project(project, link_content: nil)
+        url = urls.project_url(project, only_path: context[:only_path])
+        data = data_attribute(project: project.id)
+        content = link_content || project.to_reference_with_postfix
+
+        link_tag(url, data, content, project.name)
+      end
+
+      def link_tag(url, data, link_content, title)
+        %(<a href="#{url}" #{data} class="#{link_class}" title="#{escape_once(title)}">#{link_content}</a>)
+      end
+    end
+  end
+end