module Sjekksum::Luhn

Module for calculation and validation of Luhn checksums

@see en.wikipedia.org/wiki/Luhn_algorithm Luhn algorithm

Public Instance Methods

checksum(number)
Alias for: of
convert(number) click to toggle source

Transforms a number by appending the Luhn checksum digit

@example

Sjekksum::Luhn.convert(7992739871) #=> 79927398713

@param number [Integer, String] number without a checksum

@return [Integer, String] final number including the checksum

# File lib/sjekksum/luhn.rb, line 57
def convert number
  raise_on_type_mismatch number
  typed_conversion number
end
Also aliased as: transform
is_valid?(number)
Alias for: valid?
of(number) click to toggle source

Calculates Luhn checksum

@example

Sjekksum::Luhn.of(7992739871) #=> 3

@param number [Integer, String] number for which the checksum should be calculated

@return [Integer] calculated checksum

# File lib/sjekksum/luhn.rb, line 20
def of number
  raise_on_type_mismatch number
  digits = convert_number_to_digits(number)

  sum    = digits.reverse.map.with_index do |digit, idx|
    idx.even? ? (digit * 2).divmod(10).reduce(&:+) : digit
  end.reduce(&:+)

  (10 - sum % 10) % 10
end
Also aliased as: checksum
transform(number)
Alias for: convert
valid?(number) click to toggle source

Luhn validation of provided number

@example

Sjekksum::Luhn.valid?(79927398713) #=> true

@param number [Integer, String] number with included checksum

@return [Boolean]

# File lib/sjekksum/luhn.rb, line 41
def valid? number
  raise_on_type_mismatch number
  num, check = split_number(number)
  self.of(num) == check
end
Also aliased as: is_valid?