GUYS = {
  "む" => { "a" => "ま", "i" => "み", "u" => "む", "e" => "め", "o" => "も" },
}

class KanaKanji
  attr_reader :kana, :kanji
  def initialize(kana, kanji=nil)
    @kana = kana
    @kanji = kanji || kana
  end

  def [] (index)
    self.class.new kana[index], kanji[index]
  end

  def + (other)
    self.class.new kana + other, kanji + other
  end

  def last_character
    GUYS[kana[-1]]
  end

  def all_but_last_character
    self.class.new kana[0...-1], kanji[0...-1]
  end
end

class Verb
  attr_reader :dict_kanji, :dict_kana, :definition_english, :dict

  def initialize(dict_kanji, dict_kana, definition_english)
    @dict_kanji = dict_kanji || dict_kana
    @dict_kana = dict_kana
    @dict = KanaKanji.new dict_kana, dict_kanji
    @definition_english = definition_english
  end

  def last_character
    dict.last_character
  end

  def all_but_last_character
    dict.all_but_last_character
  end

  def ve
    VerbExpression
  end

  def dictionary
    dict
  end
end

class IchidanVerb < Verb
  def long_form_present_positive
    all_but_last_character + "ます"
  end
end

class GodanVerb < Verb
  def long_form_present_positive
    all_but_last_character + last_character["i"] + "ます"
  end
end

class SuruVerb < Verb
  def long_form_present_positive
    dict[..-3] + "します"
  end
end

見る = IchidanVerb.new("見る", "みる", "to look")
p 見る.dictionary.kanji
p 見る.dictionary.kana
p 見る.long_form_present_positive.kanji
p 見る.long_form_present_positive.kana

飲む = GodanVerb.new("飲む", "のむ", "to drink")
p 飲む.dictionary.kanji
p 飲む.dictionary.kana
p 飲む.long_form_present_positive.kanji
p 飲む.long_form_present_positive.kana

する = SuruVerb.new("する", "する", "to do")
p する.dictionary.kanji
p する.dictionary.kana
p する.long_form_present_positive.kanji
p する.long_form_present_positive.kana

勉強する = SuruVerb.new("勉強する", "べんきょうする", "to study")
p 勉強する.dictionary.kanji
p 勉強する.dictionary.kana
p 勉強する.long_form_present_positive.kanji
p 勉強する.long_form_present_positive.kana