Module: Luhn

Defined in:
lib/luhn.rb,
lib/luhn/version.rb

Constant Summary collapse

MIN_LENGTH = 
2
VERSION = 
"0.3.0"

Class Method Summary collapse

Class Method Details

.check_digit(partial_num) ⇒ Object 



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# File 'lib/luhn.rb', line 14

def check_digit(partial_num)
  (10 - (non_checksum_sum(partial_num) % 10)) % 10
end

.generate(length: 16, prefix: nil) ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/luhn.rb', line 18

def generate(length: 16, prefix: nil)
  raise ArgumentError, 'length must be more than minimum' unless length.to_i > MIN_LENGTH

  raise ArgumentError, 'prefix length invalid' if prefix && (prefix.to_s.length + MIN_LENGTH >= length)

  raise ArgumentError, 'prefix must be numeric' if prefix && !numeric_string?(prefix)

  partial_num = (prefix&.empty? ? '' : prefix).to_s
  (length - 1 - partial_num.length).times do
    partial_num += rand(10).to_s
  end
  mod = 10 - (non_checksum_sum(partial_num) % 10)
  checksum = (mod == 10 ? 0 : mod).to_s
  partial_num + checksum
end

.valid?(digits) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/luhn.rb', line 6

def valid?(digits)
  return false unless numeric_string?(digits)

  checksum = digits[-1].to_i
  non_checksum = non_checksum_sum(digits.chop)
  sum = checksum + non_checksum
  sum % 10 == 0
end