Extract 13-digit ISBNs from some input text

isbns.rb

# isbns('978-0-80-506909-9 9780671879198 0-415-82102-9 3319217283')
# => ["9780805069099", "9780671879198", "9789780805067", "9789780671877", "9780415821025", "9783319217284"]

def isbns(text)
  thirteen_digit_isbns(text) + ten_digit_isbns(text)
end

def thirteen_digit_isbns(text)
  text.tr('-', '').scan(/\b97[89]\d{10}\b/)
end

def ten_digit_isbns(text)
  text.tr('-', '').scan(/\b\d{10}\b/).map { |isbn|
    isbn.chop!
    isbn.prepend('978')
    check_digit = 10 - isbn.each_char.zip([1, 3].cycle).inject(0) { |acc, (digit, weight)| acc + (Integer(digit) * weight) } % 10
    isbn << check_digit.to_s

    isbn
  }
end