class NullObject
  def method_missing (*args, &block)
    self
  end
  def nil?; true; end
  def to_str; end
  def to_ary; []; end
end

NULL_OBJECT = NullObject.new

class SentenceGenerator

  def initialize(dictionary)
    @dictionary = dictionary
    @depth = @dictionary.depth
  end

  def random_word(last_word)
    @dictionary.dictionary.fetch(last_word, NULL_OBJECT).sample
  end

  def is_terminator?(symbol)
    (symbol =~ /[!?]/ || symbol == '.')
  end


  # Ugly way of making sure the key starts with a capital letter
  def random_capitalized_word
    random_choice = ["temp"]
    until random_choice[0] =~ /[A-Z]/
      words = @dictionary.dictionary.keys
      random_choice = words[rand(words.length)]
    end
    random_choice
  end

  def generate_sentence()
    sentence = []
    maximum_length = 30
    wordcount = 0
    sentence.concat(random_capitalized_word)
    until (is_terminator?(sentence.last[-1])) || wordcount > maximum_length
      wordcount += 1
      word = random_word(sentence.last(@depth))
      sentence << word
    end
    sentence.join(' ')
  end
end