Before deployment, is there tool to compress HTML class attribute and CSS selectors?

In current project, I was asked for compressing the HTML class attribute and corresponding CSS selectors before deployment. For example, the code on production is:

<div class="foo">
  <div id="bar"></div>
</div>

.foo {/*Style goes here*/}
#bar {/*Style goes here*/}

On deployment, I want the HTML class and corresponding CSS selectors to be substituted:

<div class="a">
  <div id="b"></div>
</div>

.a {/*Style goes here*/}
#b {/*Style goes here*/}

What's the available tools there to archive this compression?