module Log::Levels
  def self.included(cls)
    cls.extend AddLevels
  end

  def levels
    @levels ||= {}
  end
  alias :logger_levels :levels

  def levels?
    !levels.empty?
  end
  alias :logger_levels? :levels?

  def level_names
    levels.keys.dup
  end

  module AddLevels
    def add_levels(logger)
      Log::Defaults.levels.each do |level|
        logger.add_level(level, &Log::Defaults.level_formatters[level])
      end
    end
  end
end