https://blog.toright.com/posts/3471/clean-coder-%e6%9b%b8%e6%91%98-%e5%a6%82%e4%bd%95%e6%9c%89%e6%95%88%e5%9c%b0%e9%a0%90%e4%bc%b0%e8%bb%9f%e9%ab%94%e5%b0%88%e6%a1%88%e6%99%82%e9%96%93%ef%bc%9f