trappist.py

from django.http import HttpResponse
from django.conf.urls import patterns, include, url
import re


class Trappist(object):

    STATUS_INT = re.compile('^\d+')

    def __init__(self, app):
        self.app = app

    def mounted_at(self, prefix):
        regex, pattern = self.__regex_and_pattern_from(prefix)
        self.app.config.update(APPLICATION_ROOT=prefix)
        return url(regex, include(pattern), dict(mountpoint=prefix))

    def start_response(status, headers):
        pass

    def __call__(self, request, mountpoint):
        self.__patch(request, mountpoint)
        return self.__run_and_generate_response(request.environ)

    def __run_and_generate_response(self, environ):
        status_headers = [None, None]

        def start_response(status, headers):
            match = self.STATUS_INT.search(status)
            status_headers[:] = [int(match.group()), headers]

        body = self.app(environ, start_response)
        status, headers = status_headers

        response = HttpResponse(body, status=status)

        for key, value in headers:
            response[key] = value

        return response

    def __patch(self, request, mountpoint):
        patched = request.environ['PATH_INFO'][len(mountpoint):]
        original_script_name = request.environ.get('SCRIPT_NAME', '')
        request.environ['PATH_INFO'] = patched
        request.environ['SCRIPT_NAME'] = original_script_name + mountpoint

    def __regex_and_pattern_from(self, prefix):
        if not prefix.startswith('/'):
            raise ValueError('"%s" is an invalid prefix format' % prefix)

        regex = r"^%s" % prefix.lstrip('/')
        pattern = patterns('', url(r'^', self))
        return (regex, pattern)