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module GS1
# GS1 check digit calculation
#
# Implementation of: http://www.gs1.org/how-calculate-check-digit-manually
# Notice! This class does not validate the format of the given sequence,
# only the length.
#
class CheckDigitCalculator
MULTIPLIER_ARRAY = [3, 1] * 9
VALID_LENGTHS = [7, 11, 12, 13, 17].freeze
def initialize(sequence)
@sequence = sequence
@reverse_sequence = sequence.chars.reverse
raise ArgumentError, 'Invalid length' unless VALID_LENGTHS.include?(sequence.size)
end
def self.from_sequence(sequence)
new(sequence).check_digit
end
def self.with_sequence(sequence)
new(sequence).calculate_sequence_with_digit
end
def check_digit
sub_from_nearest_higher_ten.to_s
end
def calculate_sequence_with_digit
sequence + check_digit
end
private
attr_reader :sequence, :reverse_sequence
def multiplied_sequence
@multiplied_sequence ||= reverse_sequence.each_with_index.map do |digit, idx|
digit.to_i * MULTIPLIER_ARRAY[idx]
end
end
def sub_from_nearest_higher_ten
(10 - (multiplied_sequence.inject(:+) % 10)) % 10
end
end
end
Version data entries
9 entries across 9 versions & 1 rubygems