gaebackloglib.py

"""Provides patch for backloglib to work on Google App Engine

Usage:
>>> import backloglib
>>> import gaebackloglib
>>> gaebackloglib.patch(backloglib)
"""

import sys
import xmlrpclib
import logging
import re
from base64 import b64encode

from google.appengine.api import urlfetch


def patch(backloglib):
    """Patches backloglib for Gooble App Engine"""
    backloglib.ServerProxy = ServerProxyWrapper


class GAEXMLRPCTransport(object):
    """Handles an HTTP transaction to an XML-RPC server."""

    def __init__(self):
        pass

    def request(self, host, handler, request_body, verbose=0):
        result = None
        m = re.match('(.*)@(.*)', host)
        host = m.group(2)
        credential = b64encode(m.group(1))
        url = 'https://%s%s' % (host, handler)
        try:
            response = urlfetch.fetch(url,
                                      payload=request_body,
                                      method=urlfetch.POST,
                                      headers={
                                        'Content-Type': 'text/xml',
                                        'Authorization': 'Basic ' + credential
                                      }
                                     )
        except:
            msg = 'Failed to fetch %s' % url
            logging.error(msg)
            raise xmlrpclib.ProtocolError(host + handler, 500, msg, {})

        if response.status_code != 200:
            logging.error('%s returned status code %s' %
                          (url, response.status_code))
            raise xmlrpclib.ProtocolError(host + handler,
                                          response.status_code,
                                          "",
                                          response.headers)
        else:
            result = self.__parse_response(response.content)

        return result

    def __parse_response(self, response_body):
        p, u = xmlrpclib.getparser(use_datetime=False)
        p.feed(response_body)
        return u.close()


def ServerProxyWrapper(url):
    return xmlrpclib.ServerProxy(url, GAEXMLRPCTransport())