3 files changed, 70 insertions, 0 deletions
diff --git a/lib/banzai/reference_parser/mentioned_user_parser.rb b/lib/banzai/reference_parser/mentioned_user_parser.rb
new file mode 100644
index 00000000000..4b1bcb3ca09
--- /dev/null
+++ b/lib/banzai/reference_parser/mentioned_user_parser.rb
@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+module Banzai
+  module ReferenceParser
+    class MentionedUserParser < BaseParser
+      self.reference_type = :user
+
+      def references_relation
+        User
+      end
+
+      # any user can be mentioned by username
+      def can_read_reference?(user, ref_attr, node)
+        true
+      end
+    end
+  end
+end
diff --git a/lib/banzai/reference_parser/mentioned_users_by_group_parser.rb b/lib/banzai/reference_parser/mentioned_users_by_group_parser.rb
new file mode 100644
index 00000000000..d4ff6a12cd0
--- /dev/null
+++ b/lib/banzai/reference_parser/mentioned_users_by_group_parser.rb
@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+module Banzai
+  module ReferenceParser
+    class MentionedUsersByGroupParser < BaseParser
+      GROUP_ATTR = 'data-group'
+
+      self.reference_type = :user
+
+      def self.data_attribute
+        @data_attribute ||= GROUP_ATTR
+      end
+
+      def references_relation
+        Group
+      end
+
+      def nodes_visible_to_user(user, nodes)
+        groups = lazy { grouped_objects_for_nodes(nodes, Group, GROUP_ATTR) }
+
+        nodes.select do |node|
+          node.has_attribute?(GROUP_ATTR) && can_read_group_reference?(node, user, groups)
+        end
+      end
+
+      def can_read_group_reference?(node, user, groups)
+        node_group = groups[node]
+
+        node_group && can?(user, :read_group, node_group)
+      end
+    end
+  end
+end
diff --git a/lib/banzai/reference_parser/mentioned_users_by_project_parser.rb b/lib/banzai/reference_parser/mentioned_users_by_project_parser.rb
new file mode 100644
index 00000000000..79258d81cc3
--- /dev/null
+++ b/lib/banzai/reference_parser/mentioned_users_by_project_parser.rb
@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+module Banzai
+  module ReferenceParser
+    class MentionedUsersByProjectParser < ProjectParser
+      PROJECT_ATTR = 'data-project'
+
+      self.reference_type = :user
+
+      def self.data_attribute
+        @data_attribute ||= PROJECT_ATTR
+      end
+
+      def references_relation
+        Project
+      end
+    end
+  end
+end