index.js

const express = require('express');
const bodyParser = require('body-parser');
const request = require('request');
const app = express();
const token = "EAAY7ZCAfzkQYBAACN1OZAqBWd76IKHhsfBVisGJJ5WYCJtpmqkwFcpPVVeCztCw5FosfnLl7Nm4wlNmnr4mNTIT6mNZBNItS1Ljq6ZAAZCvzO19lOnVB9EI8GraTyRRcZCFoldklnnH5x0PewLZBcsz30ZAQ7ZBrAPZARZAzlfwUt7T6gZDZD";

app.set('port', (process.env.PORT || 1337));

// Process application/x-www-form-urlencoded
app.use(bodyParser.urlencoded({extended: false}));

// Process application/json
app.use(bodyParser.json());

// Index route
app.get('/', function (req, res) {
    res.send('Hello world, I am a chat bot')
});

// for Facebook verification
app.get('/webhook/', function (req, res) {
    if (req.query['hub.verify_token'] === 'my_voice_is_my_password_verify_me') {
        res.send(req.query['hub.challenge'])
    }
    res.send('Error, wrong token')
});

app.post('/webhook/', function (req, res) {
    let messaging_events = req.body.entry[0].messaging;
    for (let i = 0; i < messaging_events.length; i++) {
        let event = req.body.entry[0].messaging[i];
        let sender = event.sender.id;
        if (event.message && event.message.text) {
            let text = event.message.text;
            if (text === 'Generic') {
                sendGenericMessage(sender);
                continue
            }
            sendTextMessage(sender, "Text received, echo: " + text.substring(0, 200))
        }
        if (event.postback) {
            let text = JSON.stringify(event.postback);
            sendTextMessage(sender, "Postback received: " + text.substring(0, 200), token);
        }
    }
    res.sendStatus(200)
});

function sendTextMessage(sender, text) {
    let messageData = {text: text};
    request({
        url: 'https://graph.facebook.com/v2.6/me/messages',
        qs: {access_token: token},
        method: 'POST',
        json: {
            recipient: {id: sender},
            message: messageData
        }
    }, function (error, response, body) {
        if (error) {
            console.log('Error sending messages: ', error)
        } else if (response.body.error) {
            console.log('Error: ', response.body.error)
        }
    })
}

function sendGenericMessage(sender) {
    let messageData = {
        "attachment": {
            "type": "template",
            "payload": {
                "template_type": "generic",
                "elements": [{
                    "title": "First card",
                    "subtitle": "Element #1 of an hscroll",
                    "image_url": "http://messengerdemo.parseapp.com/img/rift.png",
                    "buttons": [{
                        "type": "web_url",
                        "url": "https://www.messenger.com",
                        "title": "Web Url"
                    }, {
                        "type": "postback",
                        "title": "Postback",
                        "payload": "Payload for first element in a generic bubble"
                    }]
                }, {
                    "title": "Second card",
                    "subtitle": "Element #2 of an hscroll",
                    "image_url": "http://messengerdemo.parseapp.com/img/gearvr.png",
                    "buttons": [{
                        "type": "postback",
                        "title": "Postback",
                        "payload": "Payload for second element in a generic bubble"
                    }]
                }]
            }
        }
    };
    request({
        url: 'https://graph.facebook.com/v2.6/me/messages',
        qs: {access_token: token},
        method: 'POST',
        json: {
            recipient: {id: sender},
            message: messageData
        }
    }, function (error, response, body) {
        if (error) {
            console.log('Error sending messages: ', error)
        } else if (response.body.error) {
            console.log('Error: ', response.body.error)
        }
    })
}

// Spin up the server
app.listen(app.get('port'), function () {
    console.log('running on port', app.get('port'))
});