chrome/common/extensions/docs/server2/appengine_url_fetcher.py

   1 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 # Use of this source code is governed by a BSD-style license that can be
   3 # found in the LICENSE file.
   4
   5 import base64
   6 import posixpath
   7
   8 from appengine_wrappers import GetAppVersion, urlfetch
   9 from future import Future
  10
  11
  12 class _AsyncFetchDelegate(object):
  13   def __init__(self, rpc):
  14     self._rpc = rpc
  15
  16   def Get(self):
  17     return self._rpc.get_result()
  18
  19
  20 def _MakeHeaders(username, password):
  21   headers = {
  22     'User-Agent': 'Chromium docserver %s' % GetAppVersion(),
  23     'Cache-Control': 'max-age=0',
  24   }
  25   if username is not None and password is not None:
  26     headers['Authorization'] = 'Basic %s' % base64.b64encode(
  27         '%s:%s' % (username, password))
  28   return headers
  29
  30
  31 class AppEngineUrlFetcher(object):
  32   """A wrapper around the App Engine urlfetch module that allows for easy
  33   async fetches.
  34   """
  35   def __init__(self, base_path=None):
  36     assert base_path is None or not base_path.endswith('/')
  37     self._base_path = base_path
  38
  39   def Fetch(self, url, username=None, password=None):
  40     """Fetches a file synchronously.
  41     """
  42     return urlfetch.fetch(self._FromBasePath(url),
  43                           headers=_MakeHeaders(username, password))
  44
  45   def FetchAsync(self, url, username=None, password=None):
  46     """Fetches a file asynchronously, and returns a Future with the result.
  47     """
  48     rpc = urlfetch.create_rpc()
  49     urlfetch.make_fetch_call(rpc,
  50                              self._FromBasePath(url),
  51                              headers=_MakeHeaders(username, password))
  52     return Future(delegate=_AsyncFetchDelegate(rpc))
  53
  54   def _FromBasePath(self, url):
  55     assert not url.startswith('/')
  56     if self._base_path is not None:
  57       url = posixpath.join(self._base_path, url) if url else self._base_path
  58     return url