[Findit] Add a Rietveld client to post a message to codereview of a culprit.

appengine/findit/common/rietveld.py

Index: appengine/findit/common/rietveld.py
diff --git a/appengine/findit/common/rietveld.py b/appengine/findit/common/rietveld.py
new file mode 100644
index 0000000000000000000000000000000000000000..bf7907177f8cd2a3e853d01bd2fd3032fc7e8241
--- /dev/null
+++ b/appengine/findit/common/rietveld.py
@@ -0,0 +1,86 @@
+# Copyright 2016 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.
+
+import logging
+import re
+import urlparse
+
+from common.codereview import CodeReview
+from common.http_client_appengine import HttpClientAppengine
+
+
+_RIETVELD_ISSUE_NUMBER_RE = re.compile('^/(\d+)/?.*')
+
+
+class Rietveld(CodeReview):
+  """The implementation of CodeReview interface for Rietveld."""
+  HTTP_CLIENT = HttpClientAppengine()
+
+  def _GetXsrfToken(self, rietveld_url):
+    """Returns the xsrf token for follow-up requests."""
+    headers = {
+        'X-Requesting-XSRF-Token': '1',
+        'Accept': 'text/plain',
+    }
+    url = '%s/xsrf_token' % rietveld_url
+    status_code, xsrf_token = self.HTTP_CLIENT.Post(
+        url, data=None, headers=headers)
+    if status_code != 200:
+      logging.error('Failed to get xsrf token from %s', rietveld_url)
+      xsrf_token = None
+    return xsrf_token
+
+  def _GetRietveldUrlAndIssueNumber(self, issue_url):
+    """Parses the given Rietveld issue url.
+
+    Args:
+      issue_url(str): The url to an issue on Rietveld.
+    Returns:
+      (rietveld_url, issue_number)
+      rietveld_url(str): The root url of the Rietveld app.
+      issue_number(str): The issue number.
+    """
+    u = urlparse.urlparse(issue_url)
+    rietveld_url = 'https://%s' % u.netloc  # Enforces https.
+    issue_number = _RIETVELD_ISSUE_NUMBER_RE.match(u.path).group(1)
+    return rietveld_url, issue_number
+
+  def _EncodeMultipartFormData(self, fields):
+    """Encodes form fields for multipart/form-data"""
+    BOUNDARY = '-F-I-N-D-I-T-M-E-S-S-A-G-E-'
+    CRLF = '\r\n'
+    lines = []
+    for key, value in fields.iteritems():
+      lines.append('--' + BOUNDARY)
+      lines.append('Content-Disposition: form-data; name="%s"' % key)
+      lines.append('')
+      lines.append(str(value))
+    lines.append('--' + BOUNDARY + '--')
+    lines.append('')
+    body = CRLF.join(lines)
+    content_type = 'multipart/form-data; boundary=%s' % BOUNDARY
+    return content_type, body
+
+  def PostMessage(self, issue_url, message):
+    rietveld_url, issue_number = self._GetRietveldUrlAndIssueNumber(issue_url)
+    url = '%s/%s/publish' % (rietveld_url, issue_number)
+    xsrf_token = self._GetXsrfToken(rietveld_url)
+    if not xsrf_token:
+      return False
+    form_fields = {
+        'xsrf_token': xsrf_token,
+        'message': message,
+        'message_only': 'True',
+        'add_as_reviewer': 'False',
+        'send_mail': 'True',
+        'no_redirect': 'True',
+    }
+    content_type, body = self._EncodeMultipartFormData(form_fields)
+    headers = {
+        'Content-Type': content_type,
+        'Accept': 'text/plain',
+    }
+    status_code, content = self.HTTP_CLIENT.Post(
+        url, data=body, headers=headers)
+    return status_code == 200 and content == 'OK'