Penny-Arcade Cipher Decryptor

pa-cipher.rb

class WordIndexCipher
  attr_accessor :source_text, :character_table

  def initialize(text)
    @source_text = text.upcase.split(' ')
    make_character_table
  end

 def encode(text)
    @cipher = ""
    text.upcase.split('').reject{|char| char == " "}.each do |character|
      if @character_table[character].empty?
        abort "Cannot encode - the character '#{character}' does not appear in your source text."
      else
        @cipher << @character_table[character].shuffle.first << " "
      end
    end
    @cipher
  end

  def decode(text)
    @plaintext = ""
    text.split(' ').each do |chunk|
      word_index, character_index = chunk.split('-')
      @plaintext << @source_text[word_index.to_i-1][character_index.to_i-1] << " "
    end
    @plaintext
  end

  private
  
  def make_character_table
    @character_table = Hash.new{|hash, key| hash[key] = []}
    @source_text.each_with_index do |word, word_index|
      word.split('').each_with_index do |character, character_index|
        @character_table[character] << "#{word_index + 1}-#{character_index + 1}"
      end
    end
  end
  
end


pa_cipher = WordIndexCipher.new('sir i need you to turn off your my what you want me to turn off my book oh youd like that i bet youd love to turn off all books wouldntcha yeah just like hitler uh oh too far youre gonna shock my genitals huh the genital region i think we might start there yeah')

puts pa_cipher.decode('28-1 10-2 10-3 6-4 18-4 43-1 36-3 9-2 43-4 32-9 41-2 1-1 2-1 45-1 42-3 33-2 3-4 42-4 14-2 26-1 32-10 35-3 54-3 56-1 3-3')

What an amazing gist.