class ClassDescendantsBuilder
  LEVEL_REGEX = /\d+/

  def self.build(base_class, level)
    base_class.descendants.each do |descendant|
      new(descendant, level).build
    end
  end

  def initialize(descendant, level)
    @descendant, @level = descendant, level
  end

  def build
    initial_level.upto(@level - 1) do |level|
      build_descendant(level) unless descendant_defined?(level)
    end
  end

  private

  def descendant_defined?(level)
    !!swap_level(level.next).safe_constantize
  end

  def build_descendant(level)
    namespace(level.next).constantize.const_set(
      swap_level(level.next).demodulize,
      Class.new(swap_level(level).constantize)
    )
  end

  def namespace(level)
    swap_level(level).deconstantize.presence || 'Object'
  end

  def swap_level(level)
    @descendant.name.sub LEVEL_REGEX, level.to_s
  end

  def initial_level
    @descendant.name[LEVEL_REGEX].to_i
  end
end