module Rambling
  module TrieCompressor
    def compress!
      if @children.size == 1 and not terminal?
        merge_with!(@children.values.first)
        compress!
      end

      @children.values.each { |node| node.compress! }

      self
    end

    private

    def merge_with!(child)
      new_letter = (@letter.to_s + child.letter.to_s).to_sym

      rehash_on_parent!(@letter, new_letter)
      redefine_self!(new_letter, child)

      @children.values.each { |node| node.parent = self }
    end

    def rehash_on_parent!(old_letter, new_letter)
      return if @parent.nil?

      @parent.delete(old_letter)
      @parent[new_letter] = self
    end

    def redefine_self!(new_letter, merged_node)
      @letter = new_letter
      @children = merged_node.children
      @is_terminal = merged_node.terminal?
    end
  end
end