index.js

'use strict';
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
  {spawn} = require('child_process');
  
const request = require('request');
app.use(express.static('client'));

// Sets server port and logs message on success
app.listen(process.env.PORT || 8080, () => console.log('webhook is listening'));

function handlePostback(sender_psid, received_postback) {
    let response;
    
    // Get the payload for the postback
    let payload = received_postback.payload;
  
    // Set the response based on the postback payload
    if (payload === 'yes') {
      response = { "text": "Thanks!" }
    } else if (payload === 'no') {
      response = { "text": "Oops, try sending another image." }
    }
    // Send the message to acknowledge the postback
    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.FACEBOOK_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);
        }
    }); 
  }

function handleMessage(sender_psid, received_message) {

    let response = {
      "text": "default text"
    };

    // Checks if the message contains text
    if (received_message.text) {
        
        // Creates the payload for a basic text message, which
        // will be added to the body of our request to the Send API
        let childPython = spawn('python', ['VnCoreNLP1/pp.py', received_message.text]);
        childPython.stdout.on('data', (data) => {
          var obj = JSON.parse(`${data}`);
          console.log(obj.nerLabel);

          response = {
            "text": obj.nerLabel
          }
          callSendAPI(sender_psid, response);  
        });

        childPython.stderr.on('data', (data) => {
            console.error(`${data}`);
        });

        childPython.on('close', (code) => {
            console.log(`child process exited with code ${code}`)
        });
    }

    
  }

// Creates the endpoint for our webhook 
app.post('/webhook', (req, res) => {  
 
    let body = req.body;
  
    // Check the webhook event is from a Page subscription
    if (body.object === 'page') {

    // Iterate over each entry - there may be multiple if batched
    body.entry.forEach(function(entry) {

      // 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);
        }
    });

    // Return a '200 OK' response to all events
    res.status(200).send('EVENT_RECEIVED');

  } else {
    // Return 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 = process.env.FACEBOOK_PAGE_ACCESS_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);      
      }
    }
  });