def publish(client, pubsub_topic, data_lines):
    """Publish to the given pubsub topic."""
    messages = []
    for line in data_lines:
        messages.append({'data': line})
    body = {'messages': messages}
    str_body = json.dumps(body)
    data = base64.urlsafe_b64encode(bytearray(str_body, 'utf8'))

    client.publish(topic=pubsub_topic, data=data)


class TweetStreamListener(StreamListener):
    """
    A listener handles tweets that are received from the stream.
    This listener dumps the tweets into a PubSub topic
    """
    client = pubsub.PublisherClient()
    pubsub_topic = client.topic_path(GCP_PROJECT_NAME, PUBSUB_TOPIC_NAME)
    count = 0
    tweets = []
    batch_size = 1
    # total_tweets = 10000
    total_tweets = TOTAL_TWEETS

    def write_to_pubsub(self, tweets):
        publish(self.client, self.pubsub_topic, tweets)

    def on_status(self, status):

        # Converting the time to isoformat for serialisation
        created_at = status.created_at.isoformat()
        id_str = status.id_str
        text = status.text
        source = status.source
        user_name = status.user.name
        user_screen_name = status.user.screen_name
        loc = status.user.location
        bio = status.user.description

        tw = dict(text=text, bio=bio, created_at=created_at, tweet_id=id_str,
                  location=loc, user_name=user_name,
                  user_screen_name=user_screen_name,
                  source=source)

        self.tweets.append(tw)
        if len(self.tweets) >= self.batch_size:
            self.write_to_pubsub(self.tweets)
            print(self.tweets)
            self.tweets = []

        self.count += 1
        if self.count >= self.total_tweets:
            return False
        if (self.count % 5) == 0:
            print("count is: {} at {}".format(self.count, datetime.datetime.now()))
        return True

    def on_error(self, status_code):
        print(status_code)


if __name__ == '__main__':
    print '....'

    auth = OAuthHandler(TWITTER_CONSUMER_KEY, TWITTER_CONSUMER_SECRET)
    auth.set_access_token(TWITTER_ACCESS_TOKEN, TWITTER_ACCESS_TOKEN_SECRET)

    stream_listener = TweetStreamListener()
    stream = Stream(auth, stream_listener)

    stream.filter(
        track=['Royal Wedding', '#RoyalWedding', 'Prince Harry', 'Meghan Markle']
    )