class Dictionary
  class WordPath
    def initialize
      @is_leaf = false
      @word_paths = {}
    end

    def leaf?
      @is_leaf
    end

    def leaf=(is_leaf)
      @is_leaf = !!is_leaf
    end

    def <<(word)
      raise ArgumentError, "must be a string" unless word.kind_of?(String)
      _append(word.strip.downcase)
    end

    def find(word)
      raise ArgumentError, "must be a string" unless word.kind_of?(String)
      _find(word.strip.downcase)
    end

    def suffixes
      [].tap do |suffixes|
        @word_paths.each do |letter, path|
          suffixes << letter if path.leaf?
          suffixes.concat(path.suffixes.collect { |suffix| "#{letter}#{suffix}" })
        end
      end
    end

    def hash
      self.class.hash ^ @is_leaf.hash ^ @word_paths.hash
    end

    def ==(obj)
      obj.class == self.class && obj.hash == self.hash
    end

    def inspect
      "#<WordPath @is_leaf=#@is_leaf @word_paths={#{@word_paths.keys.join(',')}}>"
    end

    def to_s
      inspect
    end

    protected

    def _find(word)
      word_path = @word_paths[word[0]]
      return nil unless word_path

      if word.size == 1
        word_path
      else
        word_path._find(word[1, word.size])
      end
    end

    def _append(word)
      return if word.empty?

      char = word[0]
      word_path = @word_paths[char] ||= self.class.new

      if word.size == 1
        word_path.leaf = true
      else
        word_path._append(word[1, word.size])
      end
    end
  end
end