DialogFlow webhook talking to remote API

CallAVa.js

var express = require("express");
var bodyParser = require("body-parser");
const querystring = require('querystring');
var path = require("path");
const https = require('http');
var session = require('express-session');
var FileStore = require('session-file-store')(session);
var parseurl = require('parseurl');
var fs = require("fs");
var app = express();
let sess='';

//inizializzo la sessione
app.use(session({
  store: new FileStore(),
  secret: 'keyboard cat',
  resave: false,
  saveUninitialized: true,
  cookie: {secure: false, maxAge: 180000,name:'JSESSIONID'}
}));

app.use(bodyParser.urlencoded({ extended: false }));
app.use(bodyParser.json());
app.use(express.static(__dirname));

app.use(function (req, res, next) {
  if (!req.session.views) {
    req.session.views = {}
  }
 
  // get the url pathname
  var pathname = parseurl(req).pathname;
 
  // count the views
  req.session.views[pathname] = (req.session.views[pathname] || 0) + 1;
  req.session.pippo='pippo';
  req.session.mysession='';
  sess=req.session.id;
  req.session.myid=sess;
  
  
  next();
})

/*  IP address  remote web service */

 const options = {
  hostname: '86.XXX.XX.XX',
  port: 8080, 
  path: '/AVA/rest/searchService/search_2?searchText=', 
  method: 'POST', 
  headers: {
    'Content-Type': 'application/json', 
 
    'Cookie':'' // -> I HAVE TO GET THIS VALUE THE FIRST TIME I QUERY THE WEB SERVICE, STORE IT TO SEND IT BACK TO WEB SERVICE UNTIL THE CONVERSATION GOES ON
  }
};


 
//THIS IS THE WEBHOOK END-POINT 
app.post("/callAVA", function (req,res){

  
  let strRicerca='';
  let out='';
  var str= req.body.queryResult.parameters.searchText; 
  if (str) {
    strRicerca=querystring.escape(str);
    options.path+=strRicerca+'&user=&pwd=&ava=FarmaInfoBot';
  
  // I INVOKE THE CALLAVA FUNCTION SENDING THE PARAMETERS FROM DG AGENT + ACTUAL SESSION ID GOTTEN FROM EXPRESS
  // IT DOESN'T WORK!!
  
    callAVA( strRicerca, req.session.id).then((strOutput)=> {

      return res.json({ 'fulfillmentText': strOutput}); 

    }).catch((error) => {

     return res.json({ 'fulfillmentText': 'errore: ' + error.message});

    });
 }
 

});

/**** UTILITY FUNCTIONS TO STORE SESSION  */

function writeSession(path, strSessione, strValore) {
  
  fs.appendFile(path + strSessione,strValore, function (err) {
    if (err) {
      
      throw err;
    
    } else {
    console.log('SAVED FILE '+ path + strSessione);
    
    }
     
  });
 
} 

function readSession(path, strSessione){
  var contents='';
  try {
    fs.accessSync(__dirname+ '/sessions/'+ strSessione);
    contents = fs.readFileSync(__dirname+'/sessions/'+ strSessione, 'utf8');
    console.log('READ SESSION ' +contents);
  

  }catch (err) {
    if (err.code==='ENOENT')
    console.log('INSIDE READ SESSION :file not exists...');
   
  }
  return contents;

} 
  
    
function callAVA(stringaRicerca, sess) {
  return new Promise((resolve, reject) => {
  
    let data = '';
    let strOutput='';
    var ss=readSession(__dirname +'/sessions/', sess); //GET THE ACTUAL SESSIONID FROM FILE + COOKIE GOTTEN FROM API
    if (ss===''){
      options.headers.Cookie='JSESSIONID=';
      console.log('INSIDE CALL AVA: SESSION EMPTY');
    }else {                                               //THIS IS THE FIRST TIME I QUERY THE WEB SERVICE SO IT'S OK IT'S EMPTY
      options.headers.Cookie='JSESSIONID='+ss;
      console.log('INSIDE CALL AVA:  SESSION '+ JSESSIONID);
    }
   
  //DO THE REQUEST TO WEB SERVICE
    const req = https.request(options, (res) => {
   //logs
    console.log('options.cookie AT START ' + options.headers.Cookie);
    console.log(`STATUS from response: ${res.statusCode}`);
    console.log(`HEADERS from response: ${JSON.stringify(res.headers)}`);
    console.log('..............RES HEADER ' + res.headers["set-cookie"] );
   
    if (res.headers["set-cookie"]){

      var x = res.headers["set-cookie"].toString();
      var arr=x.split(';')
      var y=arr[0].split('=');
      
      writeSession(__dirname+'/sessions/',sess, y[1]); // OK I GOT THE COOKIE FROM WEB SERVICE AND STORE IT
     
    } 
    //GETTING THE DATA FROM WEB SERVICE
    res.setEncoding('utf8');
    res.on('data', (chunk) => {
     console.log(`BODY: ${chunk}`);
     data += chunk;
    
     let c=JSON.parse(data);
            strOutput=c.output[0].output; 
            //CLEAN HTML TAG       
            strOutput=strOutput.replace(/(<\/p>|<p>|<b>|<\/b>|<br>|<\/br>|<strong>|<\/strong>|<div>|<\/div>|<ul>|<li>|<\/ul>|<\/li>|&nbsp;|)/gi, '');
            resolve(strOutput); // THIS IS THE TEXT OUTPUT I NEED TO GET BACK TO THE DG AGENT
           
          
    });
    res.on('end', () => {
      console.log('No more data in response.');
      
           
            options.path='/AVA/rest/searchService/search_2?searchText=';
            
           

    });
  });
  
  req.on('error', (e) => {
    console.error(`problem with request: ${e.message}`);
    strOutput=" error " + e.message;
  
  });
  
  // write data to request body
  
  req.write(postData);
  req.end();
  
});
} 


app.listen(process.env.PORT || 3000, function() {
    console.log("App started on port 3000");
  });