from django import template
 
register = template.Library()
 
 
@register.tag
def linkif(parser, token):
    """
    Wraps everything between ``{% linkif %}`` and ``{% endlinkif %}`` inside
    a ``link`` if ``link`` is not False.
 
    Sample usage::
 
        {% linkif "http://example.com" %}link{% endlinkif %}
        {% linkif object.url %}link only if object has an url{% endlinkif %}
 
    """
    bits = token.split_contents()
    if len(bits) != 2:
        raise template.TemplateSyntaxError("'%s' takes one argument"
                                  " (link)" % bits[0])
    link = parser.compile_filter(bits[1])
    nodelist = parser.parse(('endlinkif',))
    parser.delete_first_token()
    return LinkIfNode(nodelist, link)
 
 
class LinkIfNode(template.Node):
 
    def __init__(self, nodelist, link):
        self.link = link
        self.nodelist = nodelist
 
    def render(self, context):
        output = self.nodelist.render(context)
        link = self.link.resolve(context)
        if link:
            output = '<a href="%s">%s</a>' % (link, output)
        return output