Creating a Google Hangout Bot with Express and Node.js

Time Required: 20 minutes.
Technologies: Express, Node.js, JavaScript.
Prerequisites:

  • Basic knowledge of Express, Node.js, and JavaScript.
  • Node.js and npm are installed.

This tutorial will go over how to build a bot that will respond to pings (i.e. @<bot-name>), and send messages to a chat room. On a high level, the bot will run on an express server, and receive pings via an HTTP endpoint. Responses to pings will be sent synchronously through a payload in the HTTP response, while bot-initiated messages will be sent asynchronously using the Google Hangout Chat API.

Outline
  1. Environment setup.
  2. Get bot to respond to pings.
  3. Send bot-initiated messages.
  4. Deploy.
Environment Setup

Create a new project with the file ‘app.js’.
Open command line/terminal, and navigate to your project directory. Run ‘npm init’, and press enter until package.json is created. Next, install the following dependencies:

  • express: npm install express --save
  • body-parser:  npm install body-parser --save
  • googleapis: npm install googleapis --save
  • unirest:  npm install unirest --save

In ‘app.js’, let’s setup our server:

const express = require('express');
const bodyParser = require('body-parser');
const {google} = require('googleapis');

const app = express();

app.use(bodyParser.urlencoded({
    extended: false
}));

app.use(bodyParser.json());

app.listen(8100, () => {
    console.log('App listening on port 8100.');
});

Running ‘node app.js’ will now create a local server on port 8100.

Responding to Pings

The bot will respond to pings through a HTTP POST endpoint. Create one with express:

app.post('/', (req, res) => {
    console.log('someone pinged @<bot-name>');

    if (req.body.type === 'MESSAGE') {
        return res.json({
	    text: 'sleeping...'
	});
    }
});

The bot will respond with the text: ‘sleeping…’.

Synchronously responding to messages simply requires us to return a response to Google. The downside to this is the 30 second time limit before Google no longer accepts responses to the request. For instance, this would be a problem if you were building some kind of reminder app; the bot wouldn’t be able to synchronously respond after 30 seconds. This is where async responses come in.

Bot-initiated Messages

To show this, we will have our bot post to a chat room every 1 minute.

Sending async messages to Google API requires a Service Account for authentication. Once authenticated, we can make a POST request to a Google API URL that will create a message.

So first, create a Google Service Account following these steps. Take the downloaded JSON file and put it in the root directory of your project. Here, we renamed it to googlekeys.json:

const gkeys = require("./googlekeys.json");

We will be making POST requests using Unirest:

const unirest = require('unirest');

Now generate a JWT that will be used in our POST request:

function getJWT() {
    return new Promise((resolve, reject) => {
        let jwtClient = new google.auth.JWT(
	    gkeys.client_email,
	    null,
	    gkeys.private_key, ['https://www.googleapis.com/auth/chat.bot']);

	jwtClient.authorize((err, tokens) => {
	    if (err) {
	        console.log('Error create JWT hangoutchat');
		reject(err);
	    } else {
	        resolve(tokens.access_token);
	    }
	});
    });
}

Here is our function for posting messages. ROOM-ID can be found in the URL of the hangout chat room page i.e.: https://chat.google.com/u/0/room/<ROOM-ID>.

function postMessage(count) {
    return new Promise((resolve, reject) => {
        getJWT().then((token) => {
	    unirest.post('https://chat.googleapis.com/v1/spaces/' + <ROOM-ID> + '/messages')
	        .headers({
		    "Content-Type": "application/json",
		    "Authorization": "Bearer " + token
		})
		.send(JSON.stringify({
		    'text': 'Hello! This is message number ' + count,
		}))
		.end((res) => {
		    resolve();
		});
        }).catch((err) => {
	    reject(err);
	});
    });
}

Finally, add the code that will repeat our post every minute.

const timer = require('timers');
app.listen(8100, () => {
    console.log('App listening on port 8100.');

    let count = 0;
    timer.setInterval(() => {
        postMessage(count += 1);
    }, 60000);
});
Deploy

Expose your local server to public (we used ngrok).

Login to developer console. Create a new project, and enable Hangout Chat API. Under configuration, set:

  • status: live
  • bot name (this is how you will add and ping the bot)
  • avatar
  • description
  • functionality: rooms
  • connection settings – bot URL: <your ngrok HTTPS url>
  • permission: everyone in your domain

Restart your local server, and that’s it! Make sure you have your bot added to the chat room, and you can ping it by sending @<bot-name>. The bot will also post to the chat room every minute.

There are a lot of different ways to further extend this bot, such as setting reminders/notifications, making to-do lists, displaying server logs, and interacting with API’s.

Andy Yeung

About 

Andy is a software developer at LoginRadius who enjoys all things tech related. His primary interests are in web apps and big data. On his free time, he likes to play and watch basketball, run, and go indoor climbing.