class Remarkovable

# File lib/remarkovable.rb, line 4
def initialize(string:, prefix_length: 2)
  return if string.nil?
  build_markov_model(string, prefix_length)
end

# File lib/remarkovable.rb, line 9
def speak(custom_key: nil)
  return if @markov_model.nil?
  key = assign_key(custom_key)
  output = Array(key.capitalize.split(' '))

  until (output & %w(. ! ?)).any?
    match = @markov_model[key].sample
    if match.nil?
      key = @markov_model.keys.sample
      next
    end
    output << match
    output.flatten!
    key = [output[-2], output[-1]].join(' ')
  end

  output.join(' ').gsub(/\s+([,.!?])/, '\1')
end

# File lib/remarkovable.rb, line 55
def add_triad(key:, match:)
  @markov_model[key] = {} unless @markov_model[key]
  @markov_model[key] += [match]
end

# File lib/remarkovable.rb, line 47
def assign_key(custom_key)
  if !custom_key.nil? && @markov_model.include?(custom_key)
    custom_key
  else
    @markov_model.keys.sample
  end
end

# File lib/remarkovable.rb, line 30
def build_markov_model(string, prefix_length)
  @markov_model = Hash.new { |hash, key| hash[key] = [] }
  words = string.split(/([.!?])|\s+/)
  words.each_with_index do |word, i|
    key = [word]

    (prefix_length - 1).times do |n|
      next_word = i + n + 1
      key << words[next_word]
    end

    key = key.join(' ')
    match = words[i + prefix_length]
    add_triad(key: key, match: match) if i < words.size - prefix_length
  end
end