concept run_at

next run at

class ScheduleNextRunAt
  MONTHS = { "30" => [1,3,4,5,6,7,8,9,10,11,12], "31" => [1,3,5,7,8,10,12] }.freeze

  def initialize(date, schedule_option, advance_to_date=nil)
    @date = date
    @schedule_option = schedule_option
    @advance_to_date = advance_to_date
  end

  def next_run_date
    debugger
    return @date unless @date.is_a?(DateTime)

    if @advance_to_date.is_a?(DateTime)
      @date = set_date_to_current_day
    else
      case @schedule_option
      when 'daily'
        calc_next_day
      when 'weekly'
        calc_next_week
      when 'monthly'
        calc_next_month
      else
        @date
      end
    end
  end

  private

  def calc_next_day
    @date.next_day
  end

  def calc_next_week
    @date.next_occurring(@date.strftime("%A").downcase.to_sym)
  end

  def calc_next_month
    month = @date.month

    date = case @date.day
          when 1..28
            @date.next_month
          when 29
            if @date.leap? || @date.month > 1
              @date.next_month
            else
              @date + 2.months
            end
          when 30..31
            if month == 12
              @date.next_month
            else
              @date + (calc_skip_months(month, @date.day)).months
            end
          end
  end

  def calc_skip_months(month, day)
    pos = MONTHS[day.to_s].find_index(month)
    MONTHS[day.to_s][pos+1] - MONTHS[day.to_s][pos]
  end

  def set_date_to_current_day
    get_advanced_date(@date.year == @advance_to_date.year)
  end

  def get_advanced_date(same_year)
    case @schedule_option
    when 'once'
      @date
    when 'daily'
      @advance_to_date
    when 'weekly'
      @advance_to_date.next_occurring(@date.strftime("%A").downcase.to_sym)
    when 'monthly'
      skip_months = @advance_to_date.month - @date.month
      new_date = @date + (skip_months).months

      adavanced_date = if same_year
        if (@date.day < @advance_to_date.day)
          new_date.next_month
        else
          new_date
        end
      else

      end

      adavanced_date
    end
  end
end