module SinceWhen

# File lib/since_when.rb, line 5
def self.time_since date, scope = :month
  days_in_month = [31, date.year%4 == 0 ? 29 : 28 , 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
  scope_arr = %w(year month day hour minute second)

  time_string = ""

  if date.class != Date
    unless date.class == DateTime
      date = date.to_datetime
    end
    hour_dif = DateTime.now.hour - date.hour
    minute_dif = DateTime.now.minute - date.minute
    second_dif = DateTime.now.second - date.second
    
    if (DateTime.now - date) < 0
      throw "Future dates are not allowed."
    end
  end

  day_dif = Date.today.day - date.day
  month_dif = Date.today.month - date.month
  year_dif = Date.today.year - date.year

  if second_dif && second_dif < 0
    minute_dif -= 1
    second_dif += 60
  end
  if minute_dif && minute_dif < 0
    hour_dif -= 1
    minute_dif += 60
  end
  if hour_dif && hour_dif < 0
    day_dif -= 1
    hour_dif += 24
  end
  if day_dif < 0
    month_dif -= 1
    day_dif += days_in_month[date.month + 1]
  end
  if month_dif < 0
    year_dif -= 1
    month_dif += 12
  end


  if scope_arr.include?(scope.to_s)
    if year_dif > 0
      time_string << "#{year_dif} #{year_dif > 1 ? 'years' : 'year' }"
    end

    if month_dif > 0
      time_string << " #{month_dif} #{month_dif > 1 ? 'months' : 'month'}"
    end

    unless scope == :month
      if day_dif > 0
        time_string << " #{day_dif} #{day_dif > 1 ? 'days' : 'day'}"
      end
      unless scope == :day
        if hour_dif > 0
          time_string << " #{hour_dif} #{hour_dif > 1 ? 'hours' : 'hour'}"
        end
        unless scope == :hour
          if minute_dif > 0
            time_string << " #{minute_dif} #{minute_dif > 1 ? 'minutes' : 'minute'}"
          end
          unless scope == :minute
            if second_dif > 0
              time_string << " #{second_dif} #{second_dif > 1 ? 'seconds' : 'second'}"
            end
          end
        end
      end
    end
  end


  time_string

end