ES 6 Style import express app with websocket and data validation

index.js

import express from 'express';
import http from 'http';
import { WebSocketServer } from 'ws';
import fetch from 'node-fetch';
import Joi from 'joi';

const app = express();
const server = http.createServer(app);
const wss = new WebSocketServer({ server });

const PORT = process.env.PORT || 3000;

app.get('/', (req, res) => {
  res.sendFile(__dirname + '/index.html');
});

app.get('/ws', (req, res) => {
  res.send('WebSocket connection address: ws://localhost:3000/ws');
});

app.get('/api/titanic', async (req, res) => {
  try {
    const schema = Joi.object({
      page: Joi.number().integer().min(1).default(1),
      pageSize: Joi.number().integer().min(1).default(10)
    });

    const { error, value } = schema.validate(req.query);
    if (error) {
      return res.status(400).json({ error: error.details[0].message });
    }

    const { page, pageSize } = value;

    const response = await fetch('https://raw.githubusercontent.com/datasciencedojo/datasets/refs/heads/master/titanic.csv');
    const csv = await response.text();
    
    const rows = csv.split('\n');
    const headers = rows[0].split(',');
    const allData = rows.slice(1)
      .filter(row => row.trim())
      .map(row => {
        const values = row.split(',');
        const obj = {};
        headers.forEach((header, index) => {
          obj[header.trim()] = values[index] ? values[index].trim() : null;
        });
        return obj;
      });
    
    const startIndex = (page - 1) * pageSize;
    const endIndex = startIndex + pageSize;
    const paginatedData = allData.slice(startIndex, endIndex);
    
    res.json({
      totalRows: allData.length,
      page,
      pageSize,
      data: paginatedData,
      remainingRows: Math.max(0, allData.length - endIndex)
    });
  } catch (error) {
    console.error('Error fetching Titanic data:', error);
    res.status(500).json({ error: 'Failed to fetch Titanic data' });
  }
});

wss.on('connection', (ws) => {
  console.log('A user connected');

  ws.on('message', (msg) => {
    const message = msg.toString();
    console.log('Message received:', message);
    ws.send('Server received: ' + message);
  });

  ws.on('close', () => {
    console.log('User disconnected');
  });
});

server.listen(PORT, () => {
  console.log(`Server running on port ${PORT}`);
  console.log(`WebSocket connection address: ws://localhost:${PORT}`);
});