[autotest] Use gmail API to send emails.

Add a library that can be used by other code to send emails via
gmail api.

It can also run as a standalone script.

TEST=Ran
./site_utils/gmail_lib.py -s 2012-dut-board-inventory
fdeng@google.com fdeng@chromium.org <
/usr/local/autotest/logs/boards-2015-02-17.16.txt
BUG=chromium:465632,chromium:468622

Change-Id: Ie59986f4f8ef68fd1c2e7f62f4ec6b50e07f49bb
Reviewed-on: https://chromium-review.googlesource.com/261074
Reviewed-by: Dan Shi <dshi@chromium.org>
Reviewed-by: Richard Barnette <jrbarnette@chromium.org>
Commit-Queue: Fang Deng <fdeng@chromium.org>
Tested-by: Fang Deng <fdeng@chromium.org>

site_utils/gmail_lib.py

diff --git a/site_utils/gmail_lib.py b/site_utils/gmail_lib.py
new file mode 100755
index 0000000..57013f4
--- /dev/null
+++ b/site_utils/gmail_lib.py
@@ -0,0 +1,151 @@
+#!/usr/bin/python
+# Copyright 2015 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""
+Mail the content of standard input.
+
+Example usage:
+  Use pipe:
+     $ echo "Some content" |./gmail_lib.py -s "subject" abc@bb.com xyz@gmail.com
+
+  Manually input:
+     $ ./gmail_lib.py -s "subject" abc@bb.com xyz@gmail.com
+     > Line 1
+     > Line 2
+     Ctrl-D to end standard input.
+"""
+import argparse
+import base64
+import httplib2
+import logging
+import sys
+import os
+from email.mime.text import MIMEText
+
+import common
+from autotest_lib.client.common_lib import global_config
+
+try:
+  from apiclient.discovery import build as apiclient_build
+  from apiclient import errors as apiclient_errors
+  from oauth2client import file as oauth_client_fileio
+except ImportError as e:
+  apiclient_build = None
+  logging.debug("API client for gmail disabled. %s", e)
+
+
+DEFAULT_GMAIL_CREDS_PATH = global_config.global_config.get_config_value(
+        'NOTIFICATIONS', 'gmail_api_credentials', default='')
+
+class GmailApiException(Exception):
+    """Exception raised in accessing Gmail API."""
+
+
+class Message():
+    """An email message."""
+
+    def __init__(self, to, subject, message_text):
+        """Initialize a message.
+
+        @param to: The recievers saperated by comma.
+                   e.g. 'abc@gmail.com,xyz@gmail.com'
+        @param subject: String, subject of the message
+        @param message_text: String, content of the message.
+        """
+        self.to = to
+        self.subject = subject
+        self.message_text = message_text
+
+
+    def get_payload(self):
+        """Get the payload that can be sent to the Gmail API.
+
+        @return: A dictionary representing the message.
+        """
+        message = MIMEText(self.message_text)
+        message['to'] = self.to
+        message['subject'] = self.subject
+        return {'raw': base64.urlsafe_b64encode(message.as_string())}
+
+
+class GmailApiClient():
+    """Client that talks to Gmail API."""
+
+    def __init__(self, oauth_credentials):
+        """Init Gmail API client
+
+        @param oauth_credentials: Path to the oauth credential token.
+        """
+        if not apiclient_build:
+            raise GmailApiException('Cannot get apiclient library.')
+
+        storage = oauth_client_fileio.Storage(oauth_credentials)
+        credentials = storage.get()
+        if not credentials or credentials.invalid:
+            raise GmailApiException('Invalid credentials for Gmail API, '
+                                    'could not send email.')
+        http = credentials.authorize(httplib2.Http())
+        self._service = apiclient_build('gmail', 'v1', http=http)
+
+
+    def send_message(self, message):
+      """Send an email message.
+
+      @param message: Message to be sent.
+      """
+      try:
+        # 'me' represents the default authorized user.
+        message = self._service.users().messages().send(
+                userId='me', body=message.get_payload()).execute()
+        logging.debug('Email sent: %s' , message['id'])
+      except apiclient_errors.HttpError as error:
+        logging.error('Failed to send email: %s', error)
+
+
+def get_default_creds_abspath():
+    """Returns the abspath of the gmail api credentials file.
+
+    @return: A path to the oauth2 credentials file.
+    """
+    auth_creds = DEFAULT_GMAIL_CREDS_PATH
+    return (auth_creds if os.path.isabs(auth_creds) else
+            os.path.join(common.autotest_dir, auth_creds))
+
+
+def send_email(to, subject, message_text):
+    """Send email.
+
+    @param to: The recipients, separated by comma.
+    @param subject: Subject of the email.
+    @param message_text: Text to send.
+    """
+    auth_creds = get_default_creds_abspath()
+    if not os.path.isfile(auth_creds):
+        logging.error('Failed to send email to %s: Credential file does not'
+                      'exist: %s. If this is a prod server, puppet should'
+                      'install it. If you need to be able to send email, '
+                      'find the credential file from chromeos-admin repo and '
+                      'copy it to %s', to, auth_creds, auth_creds)
+        return
+    client = GmailApiClient(oauth_credentials=auth_creds)
+    m = Message(to, subject, message_text)
+    client.send_message(message=m)
+
+
+if __name__ == '__main__':
+    logging.basicConfig(level=logging.DEBUG)
+    parser = argparse.ArgumentParser(
+            description=__doc__, formatter_class=argparse.RawTextHelpFormatter)
+    parser.add_argument('-s', '--subject', type=str, dest='subject',
+                        required=True, help='Subject of the mail')
+    parser.add_argument('recipients', nargs='*',
+                        help='Email addresses separated by space.')
+    args = parser.parse_args()
+    if not args.recipients or not args.subject:
+        print 'Requires both recipients and subject.'
+        sys.exit(1)
+
+    message_text = sys.stdin.read()
+    send_email(','.join(args.recipients), args.subject , message_text)