server.js

const express = require('express');
const bodyParser = require('body-parser');
const cors = require('cors');
const Chatkit = require('@pusher/chatkit-server');
require('dotenv').config();

const { INSTANCE_LOCATOR: instanceLocator, CHATKIT_KEY: key } = process.env;
if (!instanceLocator || !key) {
    console.log('INSTANCE_LOCATOR or CHATKIT_KEY not set in environment.');
    process.exit(1);
}

const app = express();

const chatkit = new Chatkit.default({
    instanceLocator,
    key,
});

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

app.post('/users', (req, res) => {
    const { username } = req.body;
    chatkit
        .createUser({ id: username, name: username })
        .then(() => res.sendStatus(201))
        .catch(err => {
            if (err.error === 'services/chatkit/user_already_exists') {
                res.sendStatus(200);
            } else {
                res.status(err.status).json(err);
            }
        });
});

app.post('/authenticate', (req, res) => {
    const authData = chatkit.authenticate({ userId: req.query.user_id });
    res.status(authData.status).send(authData.body);
});

const PORT = 3001;

app.listen(PORT, err => {
    if (err) {
        console.log(err);
    } else {
        console.log(`Running on port ${PORT}`);
    }
});