Check CreditCard IIN to get issuing network

iin_check.rb

def check(number)
  number = number.gsub(/\D+/, '')
  first = Hash.new{|h,k| h[k] = number[0, k].to_i }
  size = number.size

  # American Express 	34, 37 	Yes 	15 	Luhn algorithm 	AmEx
  if [13, 16].include?(size) && number =~ /^(34|37)/
    :AmEx
  # China UnionPay 	622126-622925, 624-626, 6282-6288 	Yes 	16-19 	unknown 	CUP
  elsif (16..19) === size && ((622126..622925) === first[6] ||
                            (624..626) === first[3] ||
                            (6282..6288) === first[4])
    :CUP
  # Diners Club Carte Blanche 	300-305 	Yes 	14 	Luhn algorithm 	DC-CB
  elsif 14 == size && (300..305) === first[3]
    :DC_CB
  # Diners Club International 	36 	Yes 	14 	Luhn algorithm 	DC-Int
  elsif 14 == size && 36 == first[2]
    :DC_Int
  # Diners Club United States & Canada 	54, 55 	Yes 	16 	Luhn algorithm 	DC-UC
  elsif 16 == size && (54..55) === first[2]
    :DC_UC
  # Discover Card 	6011, 622126-622925, 644-649, 65 	Yes 	16 	Luhn algorithm 	Disc
  elsif 16 == size && (6011 == first[4] ||
                       (622126..622925) === first[6] ||
                       (644..649) === first[3] ||
                       65 == first[1])
    :Disc
  # InstaPayment 	639-637 	Yes 	16 	Luhn algorithm 	IPI
  elsif 16 == size && (637..639) === first[3]
    :IPI
  # JCB 	3528-3589 	Yes 	16 	Luhn algorithm 	JCB
  elsif 16 == size && (3528..3589) === first[4]
    :JCB
  # Laser 	6304, 6706, 6771, 6709 	Yes 	16-19 	unknown 	Lasr
  elsif (16..19) === size && [6304, 6706, 6771, 6709].include?(first[4])
    :Lasr
  # Maestro 	5018, 5020, 5038, 6304, 6759, 6761, 6763 	Yes 	12-19 	Luhn algorithm 	Maes
  elsif (12..19) === size && [5018, 5020, 5038, 6304, 6759, 6761, 6763].include?(first[4])
    :Maes
  # MasterCard 	51-55 	Yes 	16 	Luhn algorithm 	MC
  elsif 16 == size && (51..55) === first[2]
    :MC
  # Solo 	6334, 6767 	Yes 	16, 18, 19 	Luhn algorithm 	Solo
  elsif [16, 18, 19].include?(size) && [6334, 6767].include?(first[4])
    :Solo
  # Switch 	4903, 4905, 4911, 4936, 564182, 633110, 6333, 6759 	Yes 	16, 18, 19 	Luhn algorithm 	Swch
  elsif [16, 18, 19].include?(size) && (
        [4903, 4905, 4911, 4936, 6333, 6759].include?(first[4]) ||
        [564182, 633110].include?(first[6]))
    :Swch
  # Visa 	4 	Yes 	16 	Luhn algorithm 	Visa
  elsif size == 16 && 4 == first[1]
    :Visa
  # Visa Electron 	4026, 417500, 4508, 4844, 4913, 4917 	Yes 	16 	Luhn algorithm 	Visa
  elsif size == 16 && ([4026, 4508, 4844, 4913, 4917].include?(first[4]) || 417500 == first[6])
    :Visa
  end
end

['4111 1111 1111 1111',
 '5500 0000 0000 0004',
 '3400 0000 0000 009',
 '3000 0000 0000 04',
 '3000 0000 0000 04',
 '6011 0000 0000 0004',
 '3588 0000 0000 0009',
].each do |number|
  p number => check(number)
end