class RuboCop::Cop::InternalAffairs::UndefinedConfig

def always_allowed?(node)
  ALLOWED_CONFIGURATIONS.include?(node.value)
end

def configuration_key_defined?(node)
  config_for_cop.key?(node.value)
end

def extract_cop_name(class_node)
  return unless class_node
  segments = [class_node].concat(
    class_node.each_ancestor(:class, :module).take_while do |n|
      n.identifier.short_name != :Cop
    end
  )
  segments.reverse_each.map { |s| s.identifier.short_name }.join('/')
end

def on_new_investigation
  super
  return unless processed_source.ast
  cop_class = cop_class_def(processed_source.ast).first
  return unless (@cop_class_name = extract_cop_name(cop_class))
  @config_for_cop = RuboCop::ConfigLoader.default_configuration.for_cop(@cop_class_name)
end

def on_send(node)
  return unless cop_class_name
  return unless (config_name_node = cop_config_accessor?(node))
  return if always_allowed?(config_name_node)
  return if configuration_key_defined?(config_name_node)
  message = format(MSG, name: config_name_node.value, cop: cop_class_name)
  add_offense(config_name_node, message: message)
end