Time Required: 20 minutes.
\nTechnologies: Express, Node.js, JavaScript.
\nPrerequisites:
This tutorial will go over how to build a bot that will respond to pings (i.e. @
Create a new project with the file ‘app.js’.
\nOpen 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:
npm install express --savenpm install body-parser --savenpm install googleapis --savenpm install unirest --saveIn ‘app.js’, let’s setup our server:
\nconst express = require('express');\nconst bodyParser = require('body-parser');\nconst { google } = require('googleapis');\n\nconst app = express();\n\napp.use(bodyParser.urlencoded({\n extended: false\n}));\n\napp.use(bodyParser.json());\n\napp.listen(8100, function() {\n console.log('App listening on port 8100.');\n});Running ‘node app.js’ will now create a local server on port 8100.
\nThe bot will respond to pings through a HTTP POST endpoint. Create one with express:
\napp.post('/', function(req, res) {\n console.log('someone pinged @');\n\n if (req.body.type === 'MESSAGE') {\n return res.json({\n text: 'sleeping...'\n });\n }\n});The bot will respond with the text: ‘sleeping…’.
\nSynchronously 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.
\nTo show this, we will have our bot post to a chat room every 1 minute.
\nSending 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.
\nSo 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:
\nconst gkeys = require('./googlekeys.json');We will be making POST requests using Unirest:
\nconst unirest = require('unirest');Now generate a JWT that will be used in our POST request:
\nfunction getJWT() {\n return new Promise(function(resolve, reject) {\n let jwtClient = new google.auth.JWT(\n gkeys.client_email,\n null,\n gkeys.private_key, ['https://www.googleapis.com/auth/chat.bot']\n );\n\n jwtClient.authorize(function(err, tokens) {\n if (err) {\n console.log('Error create JWT hangoutchat');\n reject(err);\n } else {\n resolve(tokens.access_token);\n }\n });\n });\n}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) {\n return new Promise(function(resolve, reject) {\n getJWT().then(function(token) {\n unirest.post('https://chat.googleapis.com/v1/spaces/' + {ROOM-ID} + '/messages')\n .headers({\n "Content-Type": "application/json",\n "Authorization": "Bearer " + token\n })\n .send(JSON.stringify({\n 'text': 'Hello! This is message number ' + count,\n }))\n .end(function(res) {\n resolve();\n });\n }).catch(function(err) {\n reject(err);\n });\n });\n}Finally, add the code that will repeat our post every minute.
\nconst timer = require('timers');\n\napp.listen(8100, function() {\n console.log('App listening on port 8100.');\n\n let count = 0;\n timer.setInterval(function() {\n postMessage(count += 1);\n }, 60000);\n});Expose your local server to public (we used ngrok).
\nLogin to developer console. Create a new project, and enable Hangout Chat API. Under configuration, set:
\nRestart 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 @
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.
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