class Meetup
  require 'pry'
  WEEKDAY = [:sunday,:monday,:tuesday,:wednesday,:thursday, :friday, :saturday]
  WEEKS = [:first,:second,:third,:fourth,:last]
  LENGTH_OF_WEEK = 7
  def initialize(month, year)
    @month = month
    @year = year
    @input_date = Date.new(year,month)
  end

  def day(weekday,week)
    if week == :teenth
      (@input_date + 12).step(@input_date + 18) do |date|
        if WEEKDAY[date.wday] == weekday
          return date
        end
      end
    else
      first_day_of_month = @input_date.wday
      shifted_week = WEEKDAY.rotate(first_day_of_month)
      days_shifted = shifted_week.index(weekday)
      nth_week = (Date.new(year, month + 1).prev_day.cweek - @input_date.cweek if week == :last
      return @input_date + (LENGTH_OF_WEEK * WEEKS.index(week)) + days_shifted
    end
  end
end