from django import template
from pygments import highlight
from pygments.lexers import get_lexer_by_name
from pygments.formatters import HtmlFormatter
from django.template import Context, loader
from django.template.defaultfilters import stringfilter
import re

register = template.Library()

@register.filter(name='code_highlight')
@stringfilter
def code_highlight(value):
    """ 
        Checks for <source lang='lang'> tags in the article, and runs them
        through pygments for syntax highlighting
    """
    t = loader.get_template('codeblock.html')

    regex = re.compile(r'(<source lang=([\'"])(\w+)\2>(.*?)</source>)',
        re.DOTALL)
    items = regex.findall(value)

    for (all, crap, lang, text) in items:
        lexer = get_lexer_by_name(lang, stripall=True)
        formatter = HtmlFormatter(linenos=True, cssclass="syntax")
        result = highlight(text, lexer, formatter)

        c = Context({
            'code_block': result
        })

        value = value.replace(all, t.render(c))

    return value