Implement mail dispatcher app.

reviewbot/mail_dispatcher.py

+# Copyright (c) 2013 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""Main app that handles incoming mail and dispatches it to handlers."""
+
+import logging
+import re
+
+import webapp2
+import webob.exc
+
+from google.appengine.api import app_identity
+from google.appengine.api import mail
+
+import third_party  # pylint: disable=W0611
+
+import handlers.policy_checklist
+from review import Review
+from rietveld import Rietveld
+import util
+
+
+HANDLERS = {
+    'policy_checklist': handlers.policy_checklist.process
+}
+
+
+class MailDispatcher(webapp2.RequestHandler):
+  """Dispatches mail to handlers based on email addresses."""
+
+  def post(self):
+    """Handles POST requests.
+
+    Parses the incoming mail message. Dispatches to interested handlers based on
+    the list of mail recipients.
+    """
+
+    # Singleton Rietveld interface for this request.
+    rietveld = Rietveld()
+
+    # Parse the message and instantiate the review interface.
+    message = mail.InboundEmailMessage(self.request.body)
+    match = re.search(r'\(issue *(?P<id>\d+)\)$', message.subject)

[iannucci, 2013/08/15 03:48:05]

Ick... this is definitely fragile. Is there a way we could encode the issue as
an X header in the email? That would be more portable going forward.

[Mattias Nissler (ping if slow), 2013/08/16 12:49:22]

Yes it is... but it is the exact way that rietveld uses itself to figure out
which review the mail belongs to :)

See here:
https://code.google.com/p/rietveld/source/browse/codereview/views.py#4224

Added a comment to that effect.

+    if match is None:
+      raise webob.exc.HTTPBadRequest('Failed to parse issue id: %s' %
+                                     message.subject)
+    review = Review(match.groupdict()['id'], rietveld)
+
+    # Determine recipients and run the handlers one by one.
+    recipients = set(util.get_emails(getattr(message, 'to', '')) +
+                     util.get_emails(getattr(message, 'cc', '')))
+    addr_re = re.compile('^([^@]+)@%s.appspotmail.com$' %
+                         app_identity.get_application_id())
+    for addr in recipients:
+      match = addr_re.match(addr)
+      if not match:
+        continue
+
+      try:
+        handler = HANDLERS[match.group(1)]
+      except KeyError:
+        continue
+
+      try:
+        handler(addr, message, review, rietveld)
+      except:  # pylint: disable=W0702
+        logging.exception('Handler %s failed!', match.group(1))
+
+  def handle_exception(self, exception, debug):
+    """Handles exceptions to print HTTP error details.
+
+    Args:
+      exception: The exception.
+      debug: Whether we're in debug mode.
+    """
+    if isinstance(exception, webob.exc.HTTPException):
+      logging.warning('Request %s failed: %d - %s',
+                      self.request.url, exception.code, exception.detail)
+
+    webapp2.RequestHandler.handle_exception(self, exception, debug)
+
+
+app = webapp2.WSGIApplication([('/_ah/mail/.*', MailDispatcher)])