xmas.rb

require "date"

def days_before_xmas(year = nil, month = nil, day = nil)
  # set today and store it in a variable
  if year.nil?
    today = Date.today
    year = today.year
  else
    today = Date.new(year, month, day)
  end
  # set xmas date and store it in a variable
  if month == 12 && day > 25
    xmas_date = Date.new(year + 1, 12, 25)
  else
    xmas_date = Date.new(year, 12, 25)
  end

  # xmas - today and store it in a variable
  days_before_xmas = (xmas_date - today).to_i
  # return difference
  return days_before_xmas
end

puts "It is #{days_before_xmas} days before christmas, hurry up!"
# tests
puts days_before_xmas(2019, 10, 8).class == Integer
puts days_before_xmas(2019, 10, 8) == 78
puts days_before_xmas(2019, 10, 9) == 77
puts days_before_xmas(2020, 10, 9) == 77
puts days_before_xmas(2019, 12, 27) == 364
puts days_before_xmas == 78