module FFaker::ModuleUtils

def luhn_check(number)
  multiplications = []
  number.split(//).each_with_index do |digit, i|
    multiplications << i.even? ? digit.to_i * 2 : digit.to_i
  end
  sum = 0
  multiplications.each do |num|
    num.to_s.each_byte do |character|
      sum += character.chr.to_i
    end
  end
  control_digit = (sum % 10).zero? ? 0 : (sum / 10 + 1) * 10 - sum
  control_digit.to_s
end