Brevé Template Engine

This is a really ugly example concocted to show the power of macros. Don't try this at home, let alone in a work-related environment.

This is a template that traverses itself using macros and Tag.walk. It finds all tags with id or class attributes set and stores them in a list for later retrieval.

let ( selectors = [ ] ),

macro ( 'get_selectors', lambda tag, is_tag: (
    macro ( 'css_sep', lambda attr:
        '.' if attr == 'class' else '#'
    ),
    selectors.extend ( [
        "%s%s%s { }" % ( tag.name, css_sep ( _k.strip ( '_' ) ), _v )
        for _k, _v in tag.attrs.items ( )
        if _k.strip ( '_' ) in ( 'id', 'class' )
    ] )
) ),
macro ( 'walk_dom', lambda tag:
    tag.walk ( get_selectors, True ) and tag
),
macro ( 'output_results', lambda selectors:
    pre [ '\n'.join ( selectors ) ]
),

html [
    head [ title [ 'macro madness' ] ],
    body [ walk_dom (
        div ( class_='text', id='main-content' ) [
            img ( src='/images/breve-logo.png', alt='breve logo' ),
            br,
            span ( class_='bold' ) [ "Hello from Brevé!" ]
        ]
    ), output_results ( selectors ) ]
]

The above outputs the original template with potential CSS selectors appended to the end:

<?xml version="1.0" encoding="UTF-8"?>

<html>
  <head>
    <title>macro madness</title>
  </head>
  <body>
    <div class="text" id="main-content">
      <img src="/images/breve-logo.png" alt="breve logo"></img>
      <br />
      <span class="bold">Hello from Brevé!</span>
    </div>
    <pre>
      div.text { }
      div#main-content { }
      span.bold { }
    </pre>
  </body>
</html>

I'd like to remind you that this template spits in the face of everything Brevé holds dear and is only provided as an example of the power of macros.