doukaku.rb

class String
  def is_ipv4?
    self =~ /^(\d+)\.(\d+)\.(\d+)\.(\d+)$/ && Regexp.last_match[1..4].map(&:to_i).all? {|i| i >= 0 && i <= 255} && Regexp.last_match[1..4].all? {|octet| octet == "0" || octet[0] != "0"}
  end

  def is_ipv6?
    self =~ /([0-9a-fA-F]+):([0-9a-fA-F]+):([0-9a-fA-F]+):([0-9a-fA-F]+):([0-9a-fA-F]+):([0-9a-fA-F]+):([0-9a-fA-F]+):([0-9a-fA-F]+)/ && Regexp.last_match[1..8].all? {|hex_str| hex_str == "0" || hex_str[0] != "0"}
  end

  def is_mac?
    mac_re1 = /([0-9a-fA-F]+):([0-9a-fA-F]+):([0-9a-fA-F]+):([0-9a-fA-F]+):([0-9a-fA-F]+):([0-9a-fA-F]+)/
    mac_re2 = /([0-9a-fA-F]+)-([0-9a-fA-F]+)-([0-9a-fA-F]+)-([0-9a-fA-F]+)-([0-9a-fA-F]+)-([0-9a-fA-F]+)/
    if self =~ mac_re1
      Regexp.last_match[1..6].all? {|hex_str| hex_str.length == 2}
    elsif self =~ mac_re2
      Regexp.last_match[1..6].all? {|hex_str| hex_str.length == 2}
    else
      false
    end
  end

  def to_bin
    if self.is_ipv4?
      "01"
    elsif self.is_ipv6?
      "10"
    elsif self.is_mac?
      "00"
    else
      "11"
    end
  end
end

class Decryptor
  def bin2str(bin)
    bin.to_i(2).chr
  end
end

if defined?(RSpec) # RSpec読み込む時はテストコードの実行
  describe "is_ipv4?" do
    it do
      "0.0.0.0".is_ipv4?.should be_true
    end

    it do
      "256.0.0.0".is_ipv4?.should be_false
    end

    it do
      "255.0.0.256".is_ipv4?.should be_false
    end
  end

  describe "is_ipv6?" do
    it do
      "2001:db8:bd05:1d2:288a:1fc0:1:10ee".is_ipv6?.should be_true
    end

    it do
      "2001:db8:bd05:1d2:288a:1fc0:0:10ee".is_ipv6?.should be_true
    end

    it do
      "2001:db8:bd05:1d2:288a:1fc0:g:10ee".is_ipv6?.should be_false
    end

    it do
      "2001:db8:bd05:1d2:288a:1fc0:A:10ee".is_ipv6?.should be_true
    end

    it do
      "2001:db8:bd05:1d2:288a:1fc0:0001:10ee".is_ipv6?.should be_false
    end
  end

  describe "is_mac?" do
    it do
      "00:11:22:33:44:55".is_mac?.should be_true
    end

    it do
      "1A-B2-c3-d4-e5-f6".is_mac?.should be_true
    end

    it do
      "2a:2b-40-54:10-01".is_mac?.should be_false
    end
  end

  describe Decryptor do
    describe "bin2str" do
      it do
        subject.bin2str("1000001").should == "A"
      end
    end
  end
else # RSpec読み込まない時は標準入力を読んで暗号を解読する
  puts STDIN.each_line.each_slice(4).inject("") {|output, lines_4|
    decryptor = Decryptor.new
    crypt_bin = lines_4.inject("") {|bin, line|
      bin + line.chomp.to_bin
    }
    output + decryptor.bin2str(crypt_bin)
  }
end