module SemanticLogger
  module JRuby
    class GarbageCollectionLogger
      include Java::JavaxManagement::NotificationListener

      # Only log the garbage collection if the number of microseconds exceeds
      # this value
      def initialize(min_microseconds = 10_000)
        @min_microseconds = min_microseconds
      end

      # Must leave the method name as-is so that it can be found by Java
      def handleNotification(notification, _)
        # Only care about GARBAGE_COLLECTION_NOTIFICATION notifications
        unless notification.get_type == Java::ComSunManagement::GarbageCollectionNotificationInfo::GARBAGE_COLLECTION_NOTIFICATION
          return
        end

        info     = Java::ComSunManagement::GarbageCollectionNotificationInfo.from(notification.user_data)
        gc_info  = info.gc_info
        duration = gc_info.duration

        return unless duration >= @min_microseconds

        SemanticLogger["GarbageCollector"].measure_warn(
          "Garbage Collection completed: #{info.gc_name} ##{gc_info.id}",
          duration: duration.to_f / 1000
        )
      end
    end
  end
end