app.js

var express = require('express');
var request = require('request');
var bodyParser = require('body-parser');
var Conversation = require('watson-developer-cloud/conversation/v1'); // watson sdk
var app = express();

require('dotenv').config({silent: true});

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

var contexto_atual = null;

var w_conversation = new Conversation({
  url: 'https://gateway.watsonplatform.net/conversation/api',
  version_date: '2017-04-21',
  username: process.env.CONVERSATION_USERNAME,
  password: process.env.CONVERSATION_PASSWORD,
  version: 'v1'
});

app.get('/webhook/', function (req, res) {
	if (req.query['hub.verify_token'] === process.env.FB_TOKENVERIFIC) res.send(req.query['hub.challenge']);
	res.send('Erro de validação no token.');
});

app.post('/webhook/', function (req, res) {
	var text = null;
	
	messaging_events = req.body.entry[0].messaging;
	for (i = 0; i < messaging_events.length; i++) {	
		event = req.body.entry[0].messaging[i];
        sender = event.sender.id;

        if (event.message && event.message.text) text = event.message.text;
		else if (event.postback && !text) text = event.postback.payload;
		else break;

		 var payload = {
    		workspace_id: process.env.WORKSPACE_ID,
    		context: contexto_atual || {},
    		input: { "text": text },
			alternate_intents: true
  		};

		callWatson(payload, sender);
    }
    res.sendStatus(200);
});

function callWatson(payload, sender) {
	w_conversation.message(payload, function (err, results) {
    	if (err) return responseToRequest.send("Erro > " + JSON.stringify(err));

		if(results.context != null) contexto_atual = results.context;
		
        if(results != null && results.output != null){
			var i = 0;
			while(i < results.output.text.length){
				sendMessage(sender, results.output.text[i++]);
			}
		}
            
    });
}

function sendMessage(sender, text_) {
	text_ = text_.substring(0, 319);
	messageData = {	text: text_ };

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

app.listen(process.env.PORT || 3000);