How to get user first_name in telegram chatbot build with dialogflow_es - dialogflow-es

Question

I'm new to Dialogflow and want to understand how to extract a user's first_name in a Telegram chatbot I created. I built a chatbot using intents + inline editor (code below) and learned how to get users' data from responses using agent.parameters, but still can't code anything to extract parts of user's payload data to get first_name without asking for it. I used the following code but it didn't work:
let display_name = agent.originalRequest.payload.data.message.from.first_name
Would be super grateful if someone can explain the right code function to extract this data!
My full inline code is below.
'use strict';
const functions = require('firebase-functions');
const {WebhookClient} = require('dialogflow-fulfillment');
const admin = require ('firebase-admin');
admin.initializeApp();
admin.auth();
const db = admin.firestore();
exports.dialogflowFirebaseFulfillment = functions.https.onRequest((request, response) => {
const agent = new WebhookClient({ request, response });
function welcome(agent) {
agent.add(`Hi! Do you want to create an account?`);
}
function createUser(agent) {
agent.add(`Thank you! You have successfully created your account`);
let uid = makeid(28);
let email = agent.parameters.email;
let password = agent.parameters.user_password;
let display_name = agent.parameters.display_name;
admin.auth().createUser({uid: uid, email: email, password: password});
db.collection('users').doc(uid).set(
{uid: uid,
display_name: display_name,
});
}
function fallback(agent) {
agent.add(`I didn't understand`);
agent.add(`I'm sorry, can you try again?`);
}
let intentMap = new Map();
intentMap.set('Welcome Intent', welcome);
intentMap.set('account.creation', createUser);
intentMap.set('Default Fallback Intent', fallback);
agent.handleRequest(intentMap);
});

Answer 1

This is the code that worked for me
let payload = agent.originalRequest;
let firstname = payload.payload.data.from.first_name;