pig latin

pig_latin.rb

class String
  def to_pig_latin
    PigLatin.new(self).to_s
  end

  def self.to_pig_latin(phrase)
    phrase.to_pig_latin
  end
end

class PigLatin
  ALL_LETTERS = [*'a'..'z']
  VOWELS = ['a','e','i','o','u']
  CONSONANTS = ALL_LETTERS.reject { |letter| VOWELS.include?(letter) }

  attr_reader :phrase, :translation
  alias :to_s :translation

  def initialize(phrase)
    @phrase = phrase.downcase
    @translation = translate
  end

  def translate
    phrase.split.map do |word|
      translate_word word
    end.join(' ').chomp
  end

  private

    def translate_word(word)
      index = first_vowel_index(word)
      case index
      when 0
        translate_vowel_word word
      else
        translate_consonant_word word, index
      end
    end

    def first_vowel_index(word)
      voewls = word.each_char.map { |char| VOWELS.include?(char) }
      voewls.find_index(true) || (word.length)
    end

    def translate_consonant_word(word, vowel_index)
      consonant_cluster = word[0..(vowel_index - 1)]
      rest_of_word = word[vowel_index..-1]
      rest_of_word << consonant_cluster  << 'ay'
    end

    def translate_vowel_word(word)
      word << 'way'
    end
end

test_pig_latin.rb

require 'minitest/autorun'
require_relative 'pig_latin'

class TestPigLatin < Minitest::Spec
  describe 'words beginning with a consonant' do
    def test_banana
      assert_pig_latin_translation 'banana', 'ananabay'
    end
  end

  describe 'words beginning with a consonant cluster' do
    def test_glove
      assert_pig_latin_translation 'glove', 'oveglay'
    end

    def test_glove
      assert_pig_latin_translation 'drown', 'owndray'
    end
  end

  describe 'words beginning with a vowel' do
    def test_egg
      assert_pig_latin_translation 'egg', 'eggway'
    end

    def test_yacht
      assert_pig_latin_translation 'yacht', 'achtyay'
    end
  end

  describe 'phrases' do
    def test_the_egg_sat_on_the_wall
      assert_pig_latin_translation 'humpty dumpty sat on the wall',
        'umptyhay umptyday atsay onway ethay allway'
    end
  end

  describe 'string extension' do
    def test_translate_word
      assert_string_extension 'broken', 'okenbray'
    end

    def test_translate_phrase
      assert_string_extension 'standing on the shoulders of giants',
       'andingstay onway ethay ouldersshay ofway iantsgay'
    end

    def test_class_method
      assert_equal 'eetray', String.to_pig_latin('tree')
    end
  end

  private

    def assert_pig_latin_translation(phrase, expected)
      assert_equal expected, PigLatin.new(phrase).to_s
    end

    def assert_string_extension(phrase, expected)
      assert_equal expected, phrase.to_pig_latin
    end
end