NODE.JS
CORE_

// ============================================
// NODE.JS CORE & BUILT-IN MODULES
// ============================================

const http = require('http');
const fs = require('fs');
const path = require('path');
const crypto = require('crypto');

// 1. Basic HTTP Server (No Framework)
const server = http.createServer((req, res) => {
  if (req.url === '/' && req.method === 'GET') {
    res.writeHead(200, { 'Content-Type': 'application/json' });
    res.end(JSON.stringify({ status: 'Online', service: 'Node API' }));
  } else {
    res.writeHead(404, { 'Content-Type': 'text/plain' });
    res.end('Not Found');
  }
});
// server.listen(3000, () => console.log('Server running on port 3000'));

// 2. File System (Async/Await)
const { readFile, writeFile } = require('fs/promises');

async function manageFiles() {
  try {
    const data = await readFile(path.join(__dirname, 'data.txt'), 'utf8');
    const hash = crypto.createHash('sha256').update(data).digest('hex');
    await writeFile(path.join(__dirname, 'hash.txt'), hash);
    console.log('File encrypted and written successfully.');
  } catch (err) {
    console.error('File operation failed:', err);
  }
}

// 3. Event Emitters
const EventEmitter = require('events');
class PaymentService extends EventEmitter {}
const payment = new PaymentService();

payment.on('purchase', (amount) => {
  console.log(`Sending receipt for purchase of $${amount}`);
});

payment.emit('purchase', 19.99);

// ============================================
// EXPRESS.JS FRAMEWORK 
// ============================================

const express = require('express');
const app = express();

// Middleware
app.use(express.json()); // Body parser

// Custom Application-Level Middleware
const requestLogger = (req, res, next) => {
  console.log(`[${new Date().toISOString()}] ${req.method} ${req.url}`);
  next();
};
app.use(requestLogger);

// Routing & Controllers
const users = [];

app.get('/api/users', (req, res) => {
  res.status(200).json({ success: true, count: users.length, data: users });
});

app.post('/api/users', (req, res) => {
  const { name, email } = req.body;
  
  if (!name || !email) {
    return res.status(400).json({ success: false, error: 'Please provide name and email' });
  }
  
  const newUser = { id: Date.now(), name, email };
  users.push(newUser);
  
  res.status(201).json({ success: true, data: newUser });
});

// Parameterized Route
app.get('/api/users/:id', (req, res) => {
  const user = users.find(u => u.id === parseInt(req.params.id));
  
  if (!user) {
    return res.status(404).json({ success: false, error: 'User not found' });
  }
  
  res.status(200).json({ success: true, data: user });
});

// Global Error Handler
app.use((err, req, res, next) => {
  console.error(err.stack);
  res.status(500).json({ success: false, error: 'Something broke internally!' });
});

// app.listen(5000, () => console.log('Express app running properly'));