Customize 2FA in .NET Core MVC App Without Identity (Part -2)

				
					using Microsoft.EntityFrameworkCore;
using OtpNet;
using System.Linq.Expressions;
using System.Text;
using TwoFactorAuth.Entities;
using TwoFactorAuth.Models;
 
namespace TwoFactorAuth.Services
{
	public interface IUserService
	{
    	Task<bool> RegisterUser(RegisterViewModel registerRequest);
    	Task<bool> AuthenticateUser(LoginViewModel loginRequest);
    	Task<User> GetUser(Expression<Func<User, bool>> expression);
    	Task<(string secretKey, string qrCodeUrl)> GenerateTwoFactorInfo(string username);
    	Task<bool> EnableAuthenticator(EnableAuthenticatorViewModel model);
    	Task<bool> DisableAuthenticator(string username);
	}
	public class UserService : IUserService
	{
    	private AppDbContext _dbContext;
    	public UserService(AppDbContext appDBContext)
    	{
        	_dbContext = appDBContext;
    	}
 
    	public async Task<bool> RegisterUser(RegisterViewModel registerRequest)
    	{
        	try
        	{
            	bool isExist = await _dbContext.Users.AnyAsync(u => u.Username == registerRequest.Username);
            	if (isExist)
            	{
                	return false;
            	}
            	User user = new User();
 
            	user.Name = registerRequest.Name;
            	user.Username = registerRequest.Username;
 
            	user.Password = BCrypt.Net.BCrypt.HashPassword(registerRequest.Password);
 
            	var res = await _dbContext.Users.AddAsync(user);
 
            	await _dbContext.SaveChangesAsync();
 
            	return true;
        	}
        	catch (Exception ex)
        	{
            	return false;
        	}
 
    	}
    	public async Task<bool> AuthenticateUser(LoginViewModel loginRequest)
    	{
        	try
        	{
            	var user = await _dbContext.Users.FirstOrDefaultAsync(m => m.Username == loginRequest.Username);
 
            	if (user != null && BCrypt.Net.BCrypt.Verify(loginRequest.Password, user.Password))
            	{
                	return true;
            	}
            	else
            	{
                	return false;
            	}
 
        	}
        	catch (Exception ex)
        	{
            	return false;
        	}
 
    	}
    	public async Task<User> GetUser(Expression<Func<User, bool>> expression)
    	{
        	User user = await _dbContext.Users.FirstOrDefaultAsync(expression);
        	return user;
    	}
    	public async Task<(string secretKey, string qrCodeUrl)> GenerateTwoFactorInfo(string username)
    	{
        	const string validChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
        	var random = new Random();
 
        	// Generate a random secret key
        	var secretKeyBuilder = new StringBuilder(16);
        	for (int i = 0; i < 16; i++)
        	{
                secretKeyBuilder.Append(validChars[random.Next(validChars.Length)]);
        	}
 
        	var secretKey = secretKeyBuilder.ToString();
 
        	var encodedUsername = Uri.EscapeDataString(username);
        	var qrCodeUrl = $"otpauth://totp/{encodedUsername}?secret={secretKey}&issuer=TwoFactorAuthApp";
 
        	return (secretKey, qrCodeUrl);
    	}
 
    	public async Task<bool> EnableAuthenticator(EnableAuthenticatorViewModel model)
    	{
        	try
        	{
            	var totp = new Totp(Base32Encoding.ToBytes(model.SecretKey));
            	var verified = totp.VerifyTotp(model.Code, out _, new VerificationWindow(2, 2)); // Adjust window size as needed
            	if (verified)
            	{
                	var userDb = await _dbContext.Users.FirstOrDefaultAsync(u => u.Username == model.Username);
                	if (userDb != null)
                	{
                    	userDb.SecretKey = model.SecretKey;
                        userDb.IsTwoFactorEnabled = true;
                    	var res = _dbContext.Users.Update(userDb);
                    	await _dbContext.SaveChangesAsync();
                    	return true;
                	}
            	}
            	return false;
        	}
        	catch (Exception ex)
        	{
 
            	return false;
        	}
 
    	}
 
    	public async Task<bool> DisableAuthenticator(string username)
    	{
        	try
        	{
            	var user = await _dbContext.Users.FirstOrDefaultAsync(u => u.Username == username);
            	if (user != null)
            	{
                	user.SecretKey = string.Empty;
                	user.IsTwoFactorEnabled = false;
                	var res = _dbContext.Users.Update(user);
                	await _dbContext.SaveChangesAsync();
                	return true;
            	}
            	return false;
        	}
        	catch (Exception ex)
        	{
            	return false;
        	}
 
    	}
	}
}