1 files changed, 99 insertions, 0 deletions
diff --git a/lib/banzai/filter/references/merge_request_reference_filter.rb b/lib/banzai/filter/references/merge_request_reference_filter.rb
new file mode 100644
index 00000000000..872c33f6873
--- /dev/null
+++ b/lib/banzai/filter/references/merge_request_reference_filter.rb
@@ -0,0 +1,99 @@
+# frozen_string_literal: true
+
+module Banzai
+  module Filter
+    module References
+      # HTML filter that replaces merge request references with links. References
+      # to merge requests that do not exist are ignored.
+      #
+      # This filter supports cross-project references.
+      class MergeRequestReferenceFilter < IssuableReferenceFilter
+        self.reference_type = :merge_request
+
+        def self.object_class
+          MergeRequest
+        end
+
+        def url_for_object(mr, project)
+          h = Gitlab::Routing.url_helpers
+          h.project_merge_request_url(project, mr,
+                                              only_path: context[:only_path])
+        end
+
+        def object_link_title(object, matches)
+          # The method will return `nil` if object is not a commit
+          # allowing for properly handling the extended MR Tooltip
+          object_link_commit_title(object, matches)
+        end
+
+        def object_link_text_extras(object, matches)
+          extras = super
+
+          if commit_ref = object_link_commit_ref(object, matches)
+            klass = reference_class(:commit, tooltip: false)
+            commit_ref_tag = %(<span class="#{klass}">#{commit_ref}</span>)
+
+            return extras.unshift(commit_ref_tag)
+          end
+
+          path = matches[:path] if matches.names.include?("path")
+
+          case path
+          when '/diffs'
+            extras.unshift "diffs"
+          when '/commits'
+            extras.unshift "commits"
+          when '/builds'
+            extras.unshift "builds"
+          end
+
+          extras
+        end
+
+        def parent_records(parent, ids)
+          parent.merge_requests
+            .where(iid: ids.to_a)
+            .includes(target_project: :namespace)
+        end
+
+        def reference_class(object_sym, options = {})
+          super(object_sym, tooltip: false)
+        end
+
+        def data_attributes_for(text, parent, object, **data)
+          super.merge(project_path: parent.full_path, iid: object.iid, mr_title: object.title)
+        end
+
+        private
+
+        def object_link_commit_title(object, matches)
+          object_link_commit(object, matches)&.title
+        end
+
+        def object_link_commit_ref(object, matches)
+          object_link_commit(object, matches)&.short_id
+        end
+
+        def object_link_commit(object, matches)
+          return unless matches.names.include?('query') && query = matches[:query]
+
+          # Removes leading "?". CGI.parse expects "arg1&arg2&arg3"
+          params = CGI.parse(query.sub(/^\?/, ''))
+
+          return unless commit_sha = params['commit_id']&.first
+
+          if commit = find_commit_by_sha(object, commit_sha)
+            Commit.from_hash(commit.to_hash, object.project)
+          end
+        end
+
+        def find_commit_by_sha(object, commit_sha)
+          @all_commits ||= {}
+          @all_commits[object.id] ||= object.all_commits
+
+          @all_commits[object.id].find { |commit| commit.sha == commit_sha }
+        end
+      end
+    end
+  end
+end