Update Google Calendar Integration.

Update integration to use the latest Google API client.
Move Google Account authorization code to a separate file.
Move relevant files from 'bots/' to 'api/integrations/google/'.
Add documentation for integration.

integrations/google/get-google-credentials

@@ -0,0 +1,56 @@
+#!/usr/bin/env python
+from __future__ import print_function
+import datetime
+import httplib2
+import os
+
+from oauth2client import client
+from oauth2client import tools
+from oauth2client.file import Storage
+
+try:
+    import argparse
+    flags = argparse.ArgumentParser(parents=[tools.argparser]).parse_args()
+except ImportError:
+    flags = None
+
+# If modifying these scopes, delete your previously saved credentials
+# at zulip/bots/gcal/
+# NOTE: When adding more scopes, add them after the previous one in the same field, with a space
+# seperating them.
+SCOPES = 'https://www.googleapis.com/auth/calendar.readonly'
+# This file contains the information that google uses to figure out which application is requesting
+# this client's data.
+CLIENT_SECRET_FILE = 'client_secret.json'
+APPLICATION_NAME = 'Zulip Calendar Bot'
+HOME_DIR = os.path.expanduser('~')
+
+def get_credentials():
+    # type: () -> client.Credentials
+    """Gets valid user credentials from storage.
+
+    If nothing has been stored, or if the stored credentials are invalid,
+    the OAuth2 flow is completed to obtain the new credentials.
+
+    Returns:
+        Credentials, the obtained credential.
+    """
+
+    credential_path = os.path.join(HOME_DIR,
+                                   'google-credentials.json')
+
+    store = Storage(credential_path)
+    credentials = store.get()
+    if not credentials or credentials.invalid:
+        flow = client.flow_from_clientsecrets(os.path.join(HOME_DIR, CLIENT_SECRET_FILE), SCOPES)
+        flow.user_agent = APPLICATION_NAME
+        if flags:
+            # This attempts to open an authorization page in the default web browser, and asks the user
+            # to grant the bot access to their data. If the user grants permission, the run_flow()
+            # function returns new credentials.
+            credentials = tools.run_flow(flow, store, flags)
+        else:  # Needed only for compatibility with Python 2.6
+            credentials = tools.run(flow, store)
+        print('Storing credentials to ' + credential_path)
+
+get_credentials()

integrations/google/google-calendar

@@ -1,86 +1,31 @@
 #!/usr/bin/env python
 from __future__ import print_function
+import datetime
+import httplib2
+import itertools
+import logging
+import optparse
+import os
+from six.moves import urllib
 import sys
 import time
-import datetime
-import optparse
-from six.moves import urllib
-import itertools
 import traceback
-import os
-
-sys.path.append(os.path.join(os.path.dirname(__file__), '../api'))
-import zulip
 from typing import List, Set, Tuple, Iterable, Optional
 
-parser = optparse.OptionParser(r"""
+from oauth2client import client, tools
-
+from oauth2client.file import Storage
-%prog \
-    --user foo@zulip.com \
-    --calendar http://www.google.com/calendar/feeds/foo%40zulip.com/private-fedcba9876543210fedcba9876543210/basic
-
-    Send yourself reminders on Zulip of Google Calendar events.
-
-    To get the calendar URL:
-      - Load Google Calendar in a web browser
-      - Find your calendar in the "My calendars" list on the left
-      - Click the down-wedge icon that appears on mouseover, and select "Calendar settings"
-      - Copy the link address for the "XML" button under "Private Address"
-
-    Run this on your personal machine.  Your API key and calendar URL are revealed to local
-    users through the command line.
-
-    Depends on: python-gdata
-""")
-
-parser.add_option('--calendar',
-                  dest='calendar',
-                  action='store',
-                  help='Google Calendar XML "Private Address"',
-                  metavar='URL')
-parser.add_option('--interval',
-                  dest='interval',
-                  default=10,
-                  type=int,
-                  action='store',
-                  help='Minutes before event for reminder [default: 10]',
-                  metavar='MINUTES')
-parser.add_option_group(zulip.generate_option_group(parser))
-
-(options, args) = parser.parse_args()
-
-if not (options.zulip_email and options.calendar):
-    parser.error('You must specify --user and --calendar')
-
 try:
-    from gdata.calendar.client import CalendarClient
+    from googleapiclient import discovery
 except ImportError:
-    parser.error('Install python-gdata')
+    logging.exception('Install google-api-python-client')
 
-def get_calendar_url():
+sys.path.append(os.path.join(os.path.dirname(__file__), '../../'))
-    # type: () -> str
+import zulip
-    parts = urllib.parse.urlparse(options.calendar)
-    pat = os.path.split(parts.path)
-    if pat[1] != 'basic':
-        parser.error('The --calendar URL should be the XML "Private Address" ' +
-                     'from your calendar settings')
-    return urllib.parse.urlunparse((parts.scheme, parts.netloc, pat[0] + '/full',
-                                    '', 'futureevents=true&orderby=startdate', ''))
 
-calendar_url = get_calendar_url()
+SCOPES = 'https://www.googleapis.com/auth/calendar.readonly'
-
+CLIENT_SECRET_FILE = 'client_secret.json'
-client = zulip.init_from_options(options)
+APPLICATION_NAME = 'Zulip'
-
+HOME_DIR = os.path.expanduser('~')
-def get_events():
-    # type: () -> Iterable[Tuple[int, datetime.datetime, str]]
-    feed = CalendarClient().GetCalendarEventFeed(uri=calendar_url)
-
-    for event in feed.entry:
-        start = event.when[0].start.split('.')[0]
-        # All-day events can have only a date
-        fmt = '%Y-%m-%dT%H:%M:%S' if 'T' in start else '%Y-%m-%d'
-        start = datetime.datetime.strptime(start, fmt)
-        yield (event.uid.value, start, event.title.text)
 
 # Our cached view of the calendar, updated periodically.
 events = []  # type: List[Tuple[int, datetime.datetime, str]]
@@ -88,6 +33,100 @@ events = [] # type: List[Tuple[int, datetime.datetime, str]]
 # Unique keys for events we've already sent, so we don't remind twice.
 sent = set()  # type: Set[Tuple[int, datetime.datetime]]
 
+sys.path.append(os.path.dirname(__file__))
+
+parser = optparse.OptionParser(r"""
+
+%prog \
+    --user foo@zulip.com \
+    --calendar calendarID@example.calendar.google.com
+
+    This integration can be used to send yourself reminders, on Zulip, of Google Calendar Events.
+
+    Before running this integration make sure you run the get-google-credentials file to give Zulip
+    access to certain aspects of your Google Account.
+
+    This integration should be run on your local machine. Your API key and other information are
+    revealed to local users through the command line.
+
+    Depends on: google-api-python-client
+""")
+
+
+parser.add_option('--interval',
+                  dest='interval',
+                  default=30,
+                  type=int,
+                  action='store',
+                  help='Minutes before event for reminder [default: 30]',
+                  metavar='MINUTES')
+
+parser.add_option('--calendar',
+                  dest = 'calendarID',
+                  default = 'primary',
+                  type = str,
+                  action = 'store',
+                  help = 'Calendar ID for the calendar you want to receive reminders from.')
+
+parser.add_option_group(zulip.generate_option_group(parser))
+
+(options, args) = parser.parse_args()
+
+if not (options.zulip_email):
+    parser.error('You must specify --user')
+
+zulip_client = zulip.init_from_options(options)
+
+def get_credentials():
+    # type: () -> client.Credentials
+    """Gets valid user credentials from storage.
+
+    If nothing has been stored, or if the stored credentials are invalid,
+    an exception is thrown and the user is informed to run the script in this directory to get
+    credentials.
+
+    Returns:
+        Credentials, the obtained credential.
+    """
+    try:
+        credential_path = os.path.join(HOME_DIR,
+                                       'google-credentials.json')
+
+        store = Storage(credential_path)
+        credentials = store.get()
+
+        return credentials
+    except client.Error:
+        logging.exception('Error while trying to open the `google-credentials.json` file.')
+    except IOError:
+        logging.error("Run the get-google-credentials script from this directory first.")
+
+
+def get_events():
+    # type: () -> Iterable[Tuple[int, datetime.datetime, str]]
+    credentials = get_credentials()
+    creds = credentials.authorize(httplib2.Http())
+    service = discovery.build('calendar', 'v3', http=creds)
+
+    now = datetime.datetime.utcnow().isoformat() + 'Z' # 'Z' indicates UTC time
+    feed = service.events().list(calendarId=options.calendarID, timeMin=now, maxResults=5,
+                                 singleEvents=True, orderBy='startTime').execute()
+
+    for event in feed["items"]:
+        try:
+            start = event["start"]["dateTime"]
+        except KeyError:
+            start = event["start"]["date"]
+        start = start[:19]
+        # All-day events can have only a date
+        fmt = '%Y-%m-%dT%H:%M:%S' if 'T' in start else '%Y-%m-%d'
+        start = datetime.datetime.strptime(start, fmt)
+        try:
+            yield (event["id"], start, event["summary"])
+        except KeyError:
+            yield (event["id"], start, "(No Title)")
+
+
 def send_reminders():
     # type: () -> Optional[None]
     global sent
@@ -96,14 +135,17 @@ def send_reminders():
     keys = set()
     now = datetime.datetime.now()
 
-    for uid, start, title in events:
+    for id, start, summary in events:
         dt = start - now
         if dt.days == 0 and dt.seconds < 60 * options.interval:
             # The unique key includes the start time, because of
             # repeating events.
-            key = (uid, start)
+            key = (id, start)
             if key not in sent:
-                line = '%s starts at %s' % (title, start.strftime('%H:%M'))
+                if start.hour == 0 and start.minute == 0:
+                    line = '%s is today.' % (summary)
+                else:
+                    line = '%s starts at %s' % (summary, start.strftime('%H:%M'))
                 print('Sending reminder:', line)
                 messages.append(line)
                 keys.add(key)
@@ -116,12 +158,13 @@ def send_reminders():
     else:
         message = 'Reminder:\n\n' + '\n'.join('* ' + m for m in messages)
 
-    client.send_message(dict(
+    zulip_client.send_message(dict(
         type    = 'private',
-        to      = options.user,
+        to      = options.zulip_email,
+        sender  = options.zulip_email,
         content = message))
 
-    sent |= keys
+    sent.update(keys)
 
 # Loop forever
 for i in itertools.count():
@@ -132,5 +175,5 @@ for i in itertools.count():
             events = list(get_events())
         send_reminders()
     except:
-        traceback.print_exc()
+        logging.exception("Couldn't download Google calendar and/or couldn't post to Zulip.")
     time.sleep(60)