app.js

const express = require('express');
const { check, validationResult } = require('express-validator');
const app = express();

// Set EJS as the template view engine
app.set('view engine', 'ejs');
app.set('views', __dirname + '/views');


// Middleware to parse form data
app.use(express.urlencoded({ extended: true }));
app.use(express.json());

// In-memory array to track registered emails
let usedEmails = [];

// GET route to render the initial empty registration form
app.get('/users', (req, res) => {
  res.render('register', { errors: [], successMessage: null, formData: {} });
});

// POST route handling registration logic and validations
app.post('/users', [
  // Part 1: Username Validations
  check('username')
    .notEmpty().withMessage('Username should not be empty')
    .bail()
    .isLength({ min: 4 }).withMessage('Username must be at least 4 characters long')
    .bail()
    .custom(value => !/\s/.test(value)).withMessage('Username should not include spaces'),

  // Part 2: Email Validations
  check('email')
    .notEmpty().withMessage('Email should not be empty')
    .bail()
    .isEmail().withMessage('Invalid email')
    .bail()
    .custom(value => {
      if (usedEmails.includes(value)) {
        throw new Error('Email already exists');
      }
      return true;
    }),

  // Part 3: Password Validations
  check('password')
    .notEmpty().withMessage('Password should not be empty')
    .bail()
    .isLength({ min: 5 }).withMessage('Password must be at least 5 characters long')
    .bail()
    .matches(/^(?=.*\d)(?=.*[a-z])(?=.*[A-Z]).*$/)
    .withMessage('Password must contain a number, uppercase and lowercase'),

  // Part 3: Confirm Password Custom Match Validation
  check('confirmPassword')
    .custom((value, { req }) => {
      if (value !== req.body.password) {
        throw new Error('Passwords are not matching');
      }
      return true;
    })
], (req, res) => {
  const errors = validationResult(req);
  
  // If validation fails, re-render form with errors and existing input data
  if (!errors.isEmpty()) {
    return res.render('register', { 
      errors: errors.array(), 
      successMessage: null,
      formData: req.body 
    });
  }

  // Part 4: Successful validation actions
  const { email } = req.body;
  usedEmails.push(email);

  return res.render('register', { 
    errors: [], 
    successMessage: "Congratulations, your account has been successfully created!",
    formData: {} // Clear fields on success
  });
});
// Start the server loop on port 3000
const PORT = 3000;
app.listen(PORT, () => {
    console.log(`Server is running successfully on http://localhost:${PORT}/users`);
});