module Hizuke::MonthCalculator

def calculate_last_month_date
  # Return the first day of the previous month
  prev_month = Date.today << 1
  Date.new(prev_month.year, prev_month.month, 1)
end

def calculate_month_date(date_value)
  case date_value
  when :next_month
    calculate_next_month_date
  when :last_month
    calculate_last_month_date
  end
end

def calculate_next_month_date
  # Return the first day of the next month
  next_month = Date.today >> 1
  Date.new(next_month.year, next_month.month, 1)
end