Describe the approach to implementing an authentication and access control system for three user levels: regular users, managers, and administrators.

To implement an authentication and access restriction system with three user levels (regular users, managers, administrators), the following approach can be used:

1. Authentication:

   • Use JWT (JSON Web Tokens) or sessions to verify the user's identity.
   • During login, verify credentials and issue a token with user role information.

2. Access restriction (authorization):

   • Store the user role in the token or session.
   • At the middleware level, check the role and allow or deny access to certain routes or operations.

3. Example role structure:

   • user — basic rights, access to personal account and main functions.
   • manager — extended rights, such as managing a group of users or viewing reports.
   • admin — full access, including system management and settings.

Example middleware in Node.js using Express and JWT:

const jwt = require('jsonwebtoken');

function authorize(allowedRoles) {
  return (req, res, next) => {
    const token = req.headers.authorization?.split(' ')[1];
    if (!token) return res.status(401).send('Unauthorized');

    try {
      const payload = jwt.verify(token, 'your_secret_key');
      if (!allowedRoles.includes(payload.role)) {
        return res.status(403).send('Forbidden');
      }
      req.user = payload;
      next();
    } catch (e) {
      return res.status(401).send('Invalid token');
    }
  };
}

// Usage:
// app.get('/admin', authorize(['admin']), (req, res) => { ... });

Thus, the system will control access based on roles, ensuring security and convenience.