import operator
import re

from django import template


register = template.Library()
a_re = re.compile(r'<a.+?>\s*(.*)\s*')
space_re = re.compile(r'\s+')


@register.tag
def anchorsort(parser, token):
    """ Sorts a list of links, <a href="..."...>Anchor Text</a>. """
    nodelist = parser.parse(('endanchorsort',))
    parser.delete_first_token()
    return AnchorSortNode(nodelist)


class AnchorSortNode(template.Node):
    def __init__(self, nodelist):
        self.nodelist = nodelist

    def render(self, context):
        content = self.nodelist.render(context)

        try:
            anchorlist = [space_re.sub(" ", a).strip() for a in content.split("</a>") if len(a.strip())]

            # Compose the list of tuples, (text, <a href...>text</a>) and sort it based on the first item.
            anchorlist = [(a_re.search(x).groups(1)[0].lower(), x) for x in anchorlist]
            anchorlist.sort(key=operator.itemgetter(0))

            return "</a>".join([item[1] for item in anchorlist]) + "</a>" if anchorlist else ""
        except:
            return content