class Kuroko2::JobDefinitionStatsController

def set_period
  @end_at   = Time.current
  @start_at =
    case params[:period]
    when /\A(\d+)d\z/
      $1.to_i.days.ago(@end_at)
    when /\A(\d+)w\z/
      $1.to_i.weeks.ago(@end_at)
    when /\A(\d+)m\z/
      $1.to_i.month.ago(@end_at)
    else
      nil
    end
end