This code call Watson assistant and send the response to facebook

app.js

//Sorry for my lousy English
var bodyParser=require('body-parser');
var request=require('request');
var express = require('express');var watson = require('watson-developer-cloud');
var assistant = new watson.AssistantV1({
    username: 'Paste Assistan api username here',
    password: 'paste Assistan api password here',
    version: '2018-07-10'
});


var app = express();
app.use(bodyParser.json());
const APP_TOKEN='Paste your Facebook token here';


app.get('/', function (req, res) {
  res.send('Hello World!');
});
app.get('/webhook',function(req,res){
    if(req.query['hub.verify_token']=='Paste your Facebook Token Here '){
        res.send(req.query['hub.challenge']);
    }else{
        res.send('You cant access here ): ');
    }
});
//valida eventos
app.post('/webhook',function(req,res){
    var data=req.body;
    
    if(data.object=='page'){
        data.entry.forEach(function(pageEntry){
            pageEntry.messaging.forEach(function(messagingEvent){
                if(messagingEvent.message){
                reciveMessage(messagingEvent);
                }
            });
        });
        res.sendStatus(200);
    }//end if
});

////////////////////
//recive mensaje
function reciveMessage(event){//this function recive message an
    var senderID=event.sender.id;
    var messageText=event.message.text;
    //console.log(senderID);
    //console.log(messageText);
    sendTextToWatson(senderID,messageText);
}


function sendTextToWatson(senderId,inputText) { //This function call to Assitan api en get the answer :v
    var finalMessage='';
    assistant.message({
        workspace_id: 'Pase your workspace id here',
        input: { 'text': inputText }
    }, function (err, response) {
        if (err){
            finalMessage=err;
            //console.log('error:', err);
        }
        else{
            finalMessage=response.output.text[0];
            //console.log(JSON.stringify(response, null, 2));
            console.log("sendTextToWatson        "+finalMessage);
        }
        sendMessageText(senderId,finalMessage);

    });
}


function sendMessageText(recipientId,message){ //this function format the message
    var messageData={
        recipient:{
            id:recipientId
        },
        message:{
            text:message
        }
    };
    callSendApi(messageData);
}

function callSendApi(messageData){ //This function send text message to facebook 
    request({
        uri:'https://graph.facebook.com/v2.6/me/messages',
        qs:{access_token:APP_TOKEN},
        method:'POST',
        json:messageData
    },function(error,response,data){
        if(error){
            console.log('Error enviando msg');
        }else{
            console.log('Mensaje exitoso');
        }
    });
}
////////
var host = (process.env.VCAP_APP_HOST || 'localhost');
var port = (process.env.VCAP_APP_PORT || 3000);
app.listen(port, host);