ika_conjugations/lib/ika_conjugations/verb.rb

module IkaConjugations
  class Verb
    TE_TA_DE_DA = {
      "て" => "た", "で" => "だ"
    }

    attr_reader :dict_kanji, :dict_kana, :definition, :dict

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

    def last_character(new_form=nil)
      dict.last_character(new_form)
    end

    def all_but_last_character
      dict.all_but_last_character
    end

    def dictionary
      dict
    end

    def long_form_present_positive
      stem + "ます"
    end

    def long_form_present_negative
      stem + "ません"
    end

    def long_form_past_positive
      stem + "ました"
    end

    def long_form_past_negative
      long_form_present_negative + "でした"
    end

    def short_form_present_positive
      dictionary
    end

    def short_form_present_negative
      negative_stem + "ない"
    end

    def short_form_past_positive
      te.all_but_last_character + TE_TA_DE_DA[te.last_character]
    end

    def short_form_past_negative
      short_form_present_negative.all_but_last_character + "かった"
    end

    def desire
      stem + "たい"
    end

    def potential
      Ichidan.new(potential_starter.kanji, potential_starter.kana, "to be able #{definition}")
    end

    def excessive
      Ichidan.new(stem.kanji + "すぎる", stem.kana + "すぎる", "#{definition} too much")
    end

    def volitional
      negative_stem + "よう"
    end

    def passive
      Ichidan.new(passive_starter.kanji, passive_starter.kana, "#{definition} (dissatisfied)")
    end

    class Ichidan < Verb
      def stem
        all_but_last_character
      end

      def negative_stem
        stem
      end

      def te
        all_but_last_character + "て"
      end

      def potential_starter
        stem + "られる"
      end

      def ba
        stem + "れば"
      end

      def passive_starter
        stem + "られる"
      end
    end

    class Godan < Verb
      def iku?
        dict.kanji == "行く"
      end

      def aru?
        dict.kanji == "ある"
      end

      def stem
        all_but_last_character + last_character("i")
      end

      def short_form_present_negative
        return KanaKanji.new("ない") if aru?

        super
      end

      def negative_stem
        all_but_last_character + last_character("a")
      end

      def potential_starter
        all_but_last_character + last_character("e") + "る"
      end

      def te
        all_but_last_character + case last_character
                                 when "う"
                                   "って"
                                 when "る"
                                   "って"
                                 when "つ"
                                   "って"
                                 when "す"
                                   "して"
                                 when "く"
                                   iku? ? "って" : "いて"
                                 when "ぐ"
                                   "いで"
                                 when "ぶ"
                                   "んで"
                                 when "む"
                                   "んで"
                                 when "ぬ"
                                   "んで"
                                 end
      end

      def volitional
        all_but_last_character + last_character("o") + "う"
      end

      def ba
        all_but_last_character + last_character("e") + "ば"
      end

      def passive_starter
        all_but_last_character + last_character("a") + "れる"
      end
    end

    class Suru < Verb
      def prefix
        dict[..-3]
      end

      def stem
        prefix + "し"
      end

      def negative_stem
        prefix + "し"
      end

      def te
        prefix + "して"
      end

      def potential_starter
        prefix + "できる"
      end

      def ba
        prefix + "すれば"
      end

      def passive_starter
        prefix + "される"
      end
    end

    class Kuru < Verb
      def prefix
        dict[..-3]
      end

      def te
        stem + "て"
      end

      def stem
        prefix + KanaKanji.new("き", "来")
      end

      def negative_stem
        prefix + KanaKanji.new("こ", "来")
      end

      def potential_starter
        negative_stem + "られる"
      end

      def ba
        prefix + KanaKanji.new("く", "来") + "れば"
      end

      def passive_starter
        prefix + KanaKanji.new("こ", "来") + "られる"
      end
    end
  end
end