#!/usr/bin/ruby

func valid_iban(iban) {
  static len = Hash.new(
    AL => 28, AD => 24, AT => 20, AZ => 28, BE => 16, BH => 22, BA => 20, BR => 29,
    BG => 22, CR => 21, HR => 21, CY => 28, CZ => 24, DK => 18, DO => 28, EE => 20,
    FO => 18, FI => 18, FR => 27, GE => 22, DE => 22, GI => 23, GR => 27, GL => 18,
    GT => 28, HU => 28, IS => 26, IE => 22, IL => 23, IT => 27, KZ => 20, KW => 30,
    LV => 21, LB => 28, LI => 21, LT => 20, LU => 20, MK => 19, MT => 31, MR => 27,
    MU => 30, MC => 27, MD => 24, ME => 22, NL => 18, NO => 15, PK => 24, PS => 29,
    PL => 28, PT => 25, RO => 24, SM => 27, SA => 24, RS => 22, SK => 24, SI => 19,
    ES => 24, SE => 24, CH => 21, TN => 24, TR => 26, AE => 23, GB => 22, VG => 24,
  );

  # Ensure upper alphanumeric input.
  iban -= /\s+/g;
  iban ~~ /^[0-9A-Z]+\z/ || return false;

  # Validate country code against expected length.
  var cc = iban.substr(0, 2).uc;
  iban.len == len{cc} || return false;

  # Shift and convert.
  iban.sub!(/(.{4})(.+)/, {|a,b| b+a});
  iban.gsub!(/([A-Z])/,   {|a| a.ord - 55});

  iban.to_i % 97 == 1;
}

assert_eq(valid_iban("GB82 WEST 1234 5698 7654 32"), true);
assert_eq(valid_iban("GB82 TEST 1234 5698 7654 32"), false);

say "** Test passed!";