index.js

'use strict';

if (process.env.NODE_ENV !== 'production') {
  require('dotenv').config();
}

// Imports dependencies and set up http server
const
  express = require('express'),
  bodyParser = require('body-parser'),
  app = express().use(bodyParser.json()); // creates express http server

const request = require('request');
const axios = require("axios");

const PAGE_ACCESS_TOKEN = process.env.PAGE_ACCESS_TOKEN;
const VERIFY_TOKEN = process.env.VERIFY_TOKEN

// Sets server port and logs message on success
app.listen(process.env.PORT || 1337, () => console.log('webhook is listening'));

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

// Creates the endpoint for our webhook 
app.post('/webhook', (req, res) => {  
 
    let body = req.body;
  
    // Checks this is an event from a page subscription
    if (body.object === 'page') {
  
      // Iterates over each entry - there may be multiple if batched
      body.entry.forEach(function(entry) {
  
        // Gets the message. entry.messaging is an array, but 
        // will only ever contain one message, so we get index 0
        // Gets the body of the webhook event
        let webhook_event = entry.messaging[0];
        console.log(webhook_event);

        // Get the sender PSID
        let sender_psid = webhook_event.sender.id;
        console.log('Sender PSID: ' + sender_psid);

        // Check if the event is a message or postback and
        // pass the event to the appropriate handler function
        if (webhook_event.message) {
          handleMessage(sender_psid, webhook_event.message);        
        } else if (webhook_event.postback) {
          handlePostback(sender_psid, webhook_event.postback);
        }
      });
  
      // Returns a '200 OK' response to all requests
      res.status(200).send('EVENT_RECEIVED');
    } else {
      // Returns a '404 Not Found' if event is not from a page subscription
      res.sendStatus(404);
    }
  
  });


// Adds support for GET requests to our webhook
app.get('/webhook', (req, res) => {

    // Your verify token. Should be a random string.
    let VERIFY_TOKEN = "<VERIFY_TOKEN>"
      
    // Parse the query params
    let mode = req.query['hub.mode'];
    let token = req.query['hub.verify_token'];
    let challenge = req.query['hub.challenge'];
      
    // Checks if a token and mode is in the query string of the request
    if (mode && token) {
    
      // Checks the mode and token sent is correct
      if (mode === 'subscribe' && token === VERIFY_TOKEN) {
        
        // Responds with the challenge token from the request
        console.log('WEBHOOK_VERIFIED');
        res.status(200).send(challenge);
      
      } else {
        // Responds with '403 Forbidden' if verify tokens do not match
        res.sendStatus(403);      
      }
    }
  });

async function handleMessage(sender_psid, received_message) {

  let response = {
    "text": "yeah im a bot i dont understand anything other than texts sorry"
  }
  let text = {
    "text": received_message.text
  }

  // Check if the message contains text
  if (received_message.text) {    
    let res = await axios.post("https://jme-bot.herokuapp.com/text", text)
    response.text = await res.data.response
    console.log("REQUEST RESPONSE")
    console.log(res)
  }

  console.log("OFFICIAL RESPONSE")
  console.log(response)

  // Sends the response message
  callSendAPI(sender_psid, response); 
}  
  
function callSendAPI(sender_psid, response) {
  // Construct the message body
  let request_body = {
    "recipient": {
      "id": sender_psid
    },
    "message": response
  }

  // Send the HTTP request to the Messenger Platform
  request({
    "uri": "https://graph.facebook.com/v2.6/me/messages",
    "qs": { "access_token": process.env.PAGE_ACCESS_TOKEN },
    "method": "POST",
    "json": request_body
  }, (err, res, body) => {
    if (!err) {
      console.log('message sent!')
    } else {
      console.error("Unable to send message:" + err);
    }
  }); 
}

// Handles messaging_postbacks events
// function handlePostback(sender_psid, received_postback) {

// }