class Statistic
  # save message to a log file
  # usage:
  # Statistic.log "message"
  # Statistic.log { var }
  def self.log(message = nil, &block)
    @logger ||= Logger.new(Rails.root.join('log', "statistic.#{Rails.env}.log"))
    begin
      message = yield if block_given?
      @logger.info("#{Time.current} #{message}")
    rescue Exception => e
      # make sure the log method will not be stop the main progress
      @logger.info("#{Time.current} error:#{e} for #{block}")
    end
  end
end