Markov chain implementation for the arlt.rb bot

arlt.rb

class Markov
  PHRASE_SEPARATOR = /[\.;]/
  WORD_SEPARATOR = " "

  attr_reader :knowledge, :order

  def initialize(order: 2)
    @knowledge = {}
    @order = order
  end

  def read(text)
    phrases(text).each do |phrase|
      (Array.new(order, " ") + words(phrase)).each_cons(order + 1) { |*key, value | learn key, value }
    end
    knowledge
  end

  def compose()
    generate(Array.new(order, " ")).drop(order).join(" ") << "."
  end

  def generate(chain)
    key = chain.last(order).join(" ")
    alternatives = knowledge[key]
    following = alternatives ? alternatives.sample : nil

    while following
      chain << following
      key = chain.last(order).join(" ")
      alternatives = knowledge[key]
      following = alternatives ? alternatives.sample : nil
    end

    chain
  end

  def learn(a, b)
    key = a.join(" ")
    knowledge[key] ||= []
    knowledge[key] << b
  end

  def words(text, sep: WORD_SEPARATOR)
    text.split(sep).reject(&:empty?)
  end

  def phrases(text, sep: PHRASE_SEPARATOR)
    text.split(sep).reject(&:empty?).each(&:strip!)
  end

  def store(file = "markov-#{order}.db")
    File.write file, Marshal.dump(knowledge)
    self
  end

  def load(file = "markov-#{order}.db")
    @knowledge = Marshal.load File.read file
    self
  end
end