CSS parser + XHTML generator, tip needed

Question

CSS parser + XHTML generator, tip needed

Guys, I need to develop a tool that will meet the following requirements:

Input: XHTML document with CSS rules in the section head.
Exit: XHTML document with CSS rules computed in tag attributes

The best way to illustrate the behavior I want is as follows.

Input Example:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html>
<head>
  <style type="text/css" media="screen">
    .a { color: red; }
        p { font-size: 12px; }
  </style>
</head>
<body>
    <p class="a">Lorem Ipsum</p>
    <div class="a">
         <p>Oh hai</p>
    </div>
</body>
</html>

Output Example:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html>
<body>
    <p style="color: red; font-size: 12px;">Lorem Ipsum</p>
    <div style="color: red;">
         <p style="font-size: 12px;">Oh hai</p>
    </div>
</body>
</html>