class Rufus::Scheduler::IntervalJob

def initialize(scheduler, interval, opts, block)
  super(scheduler, interval, opts, block)
  @interval = Rufus::Scheduler.parse_in(@original)
  raise ArgumentError.new(
    "cannot schedule #{self.class} with an interval " +
    "of #{@interval.inspect} (#{@original.inspect})"
  ) if @interval <= 0
  set_next_time(nil)
end

def next_time_from(time)
  time + @mean_work_time + @interval
end

def set_next_time(trigger_time, is_post=false)
  @next_time =
    if is_post
      Time.now + @interval
    elsif trigger_time.nil?
      if @first_at == nil || @first_at < Time.now
        Time.now + @interval
      else
        @first_at
      end
    else
      false
    end
end