index.js

'use strict'

const express = require('express')
const bodyParser = require('body-parser')
const request = require('request')

const app = express()

const tokenF = process.env.FB_VERIFY_TOKEN
const access = process.env.FB_ACCESS_TOKEN

app.set('port', (process.env.PORT || 5000))

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

app.get('/', function(req, res) {
  res.send("Hola amigos :v  soy un chatbot")
})

//let token = "EAALZAWNaM1jIBAHpmhydvUNMGE3ZAsv9jZBhlXGZBDqOPEPdZACWZANxW6tniJd4MOiGROOUwnVzIGXDJ4elnf5ndeZAM0gPEzUlr3zWhlWg9T8JbZBa71kV3pe3MKBQ4ncF61cOXa4dAjyri5gdvmDDLXdMfHKwpXjB8zZA4OY18AgZDZD"
//Facebook
app.get('/webhook/', function (req, res) {
  if (req.query['hub.verify_token'] === tokenF) {
    res.send(req.query['hub.challenge'])
    res.send("Rigth token")

  }
    res.send("Wrong token")
})

app.post('/webhook', (req, res) => {

  // Parse the request body from the POST
  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);
  }

});


function handleMessage(sender_psid, received_message) {
  let response;

   // Checks if the message contains text
   if (received_message.text) {
     // Create the payload for a basic text message, which
     // will be added to the body of our request to the Send API
     response = {
       "text": `Tu enviaste este mensaje: "${received_message.text}". ahora envia una imagen!`
     }
   } else if (received_message.attachments) {
     // Get the URL of the message attachment
     let attachment_url = received_message.attachments[0].payload.url;
     response = {
       "attachment": {
         "type": "template",
         "payload": {
           "template_type": "generic",
           "elements": [{
             "title": "Esta es la imagen que mandaste?",
             "subtitle": "Toca el boton para responder.",
             "image_url": attachment_url,
             "buttons": [
               {
                 "type": "postback",
                 "title": "Si!",
                 "payload": "yes",
               },
               {
                 "type": "postback",
                 "title": "No!",
                 "payload": "no",
               },
               {
                 "type": "postback",
                 "title": "Puede ser!",
                 "payload": "ojala",
               }
             ],
           }]
         }
       }
     }
   }

   // Send 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
  }
}


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": access },
    "method": "POST",
    "json": request_body
  }, (err, res, body) => {
    if (!err) {
      console.log('message sent!')
    } else {
      console.error("Unable to send message:" + err);
    }
  });
}

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": "Gracias todo correcto!" }
  } else if (payload === 'no') {
    response = { "text": "Oops, intente con otra imagen ;)." }
  }
  // Send the message to acknowledge the postback
  callSendAPI(sender_psid, response);
}

app.listen(app.get('port'), function() {
  console.log(app.get('port'));
})