from django.core import exceptions
from django.conf import settings

class FirebugMiddleware(object):

    def __init__(self):
        if not settings.DEBUG:
            raise exceptions.MiddlewareNotUsed

        try:
            self.firebug_url = settings.FIREBUG_URL
        except AttributeError:
            self.firebug_url = 'http://getfirebug.com/releases/lite/' + \
                '1.2/firebug-lite-compressed.js'

    def process_response(self, request, response):
        if (request.META.get('REMOTE_ADDR') in settings.INTERNAL_IPS and
            request.META.get('HTTP_USER_AGENT').lower().find('gecko', 0) < 0):
            index = response.content.lower().find('</head>')
            if index != -1:
                response.content = '\n'.join([response.content[:index],
                    self.firebug_html, response.content[index:]])
        return response

    @property
    def firebug_html(self):
        return '<script type="text/javascript" src="%s"></script>' % (
            self.firebug_url)