Refactor WPT Export to ensure only one PR in flight at a time

third_party/WebKit/Tools/Scripts/webkitpy/w3c/wpt_github.py

 # 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 base64
 import json
 import httplib2
 import logging
 
 _log = logging.getLogger(__name__)
+API_BASE = 'https://api.github.com'
+EXPORT_LABEL = 'chromium-export'
 
 
-class GitHub(object):
+class WPTGitHub(object):
 
     def __init__(self, host):
         self.host = host
         self.user = self.host.environ.get('GH_USER')
         self.token = self.host.environ.get('GH_TOKEN')
 
         assert self.user and self.token, 'must have GH_USER and GH_TOKEN env vars'
 
     def auth_token(self):
         return base64.encodestring('{}:{}'.format(self.user, self.token))
 
     def create_pr(self, local_branch_name, desc_title, body):
         """Creates a PR on GitHub.
 
         API doc: https://developer.github.com/v3/pulls/#create-a-pull-request
 
         Returns:
             A raw response object if successful, None if not.
         """
         assert local_branch_name
         assert desc_title
         assert body
 
         pr_branch_name = '{}:{}'.format(self.user, local_branch_name)
 
+        # TODO(jeffcarp): CC foolip and qyearsley on all PRs for now
         # TODO(jeffcarp): add HTTP to Host and use that here
         conn = httplib2.Http()
         headers = {
             "Accept": "application/vnd.github.v3+json",
             "Authorization": "Basic " + self.auth_token()
         }
         body = {
             "title": desc_title,
             "body": body,
             "head": pr_branch_name,
-            "base": "master"
+            "base": 'master',
+            "labels": [EXPORT_LABEL]
         }
         resp, content = conn.request("https://api.github.com/repos/w3c/web-platform-tests/pulls",
                                      "POST", body=json.JSONEncoder().encode(body), headers=headers)
         _log.info("GitHub response: %s", content)
         if resp["status"] != "201":
             return None
         return json.loads(content)
+
+    def in_flight_pull_requests(self):
+        url_encoded_label = EXPORT_LABEL.replace(' ', '%20')
+        path = '/search/issues?q=repo:w3c/web-platform-tests%20is:open%20type:pr%20labels:{}'.format(url_encoded_label)
+        response, content = self.request(path)
+        if response['status'] == '200':
+            data = json.loads(content)
+            return data['items']
+        else:
+            raise Exception('Non-200 status code (%s): %s' % (response['status'], content))
+
+    def request(self, path, body=None):
+        assert path.startswith('/')
+
+        # Not used yet since only hitting public API
+        # headers = {
+        #     "Accept": "application/vnd.github.v3+json",
+        #     "Authorization": "Basic " + self.auth_token()
+        # }
+
+        if body:
+            json_body = json.dumps(body)
+        else:
+            json_body = None
+
+        conn = httplib2.Http()
+        return conn.request(API_BASE + path, body=json_body)
+
+    def merge_pull_request(self, pull_request_number):
+        path = '/repos/w3c/web-platform-tests/pulls/%d/merge' % pull_request_number
+        body = {}
+        response, content = self.request(path, body)
+
+        if response['status'] == '200':
+            return json.loads(content)
+        else:
+            raise Exception('PR could not be merged: %d' % pull_request_number)