TwoStepAut

===================================================Program=============================================================================
class Program {
        static string ReadPassword() {
            StringBuilder sb = new StringBuilder();
            ConsoleKeyInfo key;
            do {
                key = Console.ReadKey(true);
                if (key.Key != ConsoleKey.Backspace && key.Key != ConsoleKey.Enter && key.Key != ConsoleKey.Escape) {
                    sb.Append(key.KeyChar);
                    Console.Write("*");
                }
                else {
                    if (key.Key == ConsoleKey.Backspace && sb.Length > 0) {
                        sb.Remove(sb.Length - 1, 1);
                        Console.Write("\b \b");
                    }
                }
            } while (key.Key != ConsoleKey.Enter);
            Console.WriteLine();
            return sb.ToString();
        }

        static void Main(string[] args) {
            Console.Write("Enter username: ");
            var username = Console.ReadLine();
            Console.Write("Enter password: ");
            var password = ReadPassword();

            var authenticator = new Authenticator();
            if (authenticator.CheckFirstStep(username, password)) {
                Console.WriteLine("Enter confirmation code: ");
                var code = Console.ReadLine();
                if (authenticator.CheckSecondStep(username, code))
                    Console.WriteLine("Success!!!");
                else
                    Console.WriteLine("Invalid confirmation code");
            }
            else {
                Console.WriteLine("Incorrect username / password");
            }
            Console.ReadKey();
        }
    }
======================================================================================================================================================================================SmsConfirmationChannel==================================================================
class SmsConfirmationChannel : IConfirmationChannel {
        public void SendConfirmationCode(User user, string code) {
            // Just a placeholder function
            Console.WriteLine($"SMS on {user.Telephone}: Your confirmation code is {code}");
        }
    }
=======================================================================================================================================
==============================================User=====================================================================================
 public class User {
        public int Id { get; set; }
        public string Username { get; set; }
        public string PasswordHash { get; set; }
        public string Email { get; set; }
        public string Telephone { get; set; }
        public string Code { get; set; }
        public DateTime CodeGenerationDt { get; set; }
    }
=======================================================================================================================================
============================================UserRepository=============================================================================
class UserRepository : IDisposable {
        private Context _context = new Context();

        public IQueryable<User> Users {
            get {
                return _context.Users;
            }
        }

        public void UpdateConfirmationCode(User user, string code) {
            user.Code = code;
            user.CodeGenerationDt = DateTime.Now;
            _context.SaveChanges();
        }

        public void Dispose() {
            _context.Dispose();
        }
    }
====================================================================================================================================================================================IConfirmationChannel======================================================================
public interface IConfirmationChannel {
        void SendConfirmationCode(User user, string code);
    }
====================================================================================================================================================================================Helpers===================================================================================
static class Helpers {
        private static Random r = new Random();

        public static string GetHash(string password) {
            var md5 = MD5.Create();
            var hash = md5.ComputeHash(Encoding.UTF8.GetBytes(password));
            return Convert.ToBase64String(hash);
        }

        public static string GenerateConfirmationCode(int length) {
            var sb = new StringBuilder();
            for (int i = 0; i < length; i++) {
                sb.Append((char)('0' + r.Next(10)));
            }
            return sb.ToString();
        }
    }
======================================================================================================================================================================================Factory=================================================================================
class Factory {
        private static Factory _default;

        public static Factory Default {
            get {
                return _default ?? (_default = new Factory());
            }
        }

        private Factory() {

        }

        public IConfirmationChannel CreateConfirmationChannel() {
            return new EmailConfirmationChannel();
        }
    }
==============================================================================================================================================================================================EmailConfirmationChannel========================================================
class EmailConfirmationChannel : IConfirmationChannel {
        public void SendConfirmationCode(User user, string code) {
            // Just a placeholder function
            Console.WriteLine($"New e-mail on {user.Email}: Your confirmation code is {code}");
        }
    }
==============================================================================================================================================================================================Context=========================================================================
class Context : DbContext {
        public DbSet<User> Users { get; set; }

        public Context() : base("UserDB") {

        }
    }
=======================================================================================================================================
======================================================Authenticator====================================================================
public class Authenticator {
        private const int CodeLength = 6;

        IConfirmationChannel _confirmationChannel = Factory.Default.CreateConfirmationChannel();

        public bool CheckFirstStep(string username, string password) {
            // Compare username and password with the ones stored in the internal container
            var passwordHash = Helpers.GetHash(password);
            using (var repo = new UserRepository()) {
                var user = repo.Users.FirstOrDefault(u => u.Username == username && u.PasswordHash == passwordHash);
                if (user != null) {
                    var code = Helpers.GenerateConfirmationCode(CodeLength);
                    repo.UpdateConfirmationCode(user, code);
                    _confirmationChannel.SendConfirmationCode(user, code);
                    return true;
                }
                else
                    return false;
            }
        }

        public bool CheckSecondStep(string username, string code) {
            using (var repo = new UserRepository()) {
                var user = repo.Users.FirstOrDefault(u => u.Username == username && u.Code == code);
                if (user != null && user.CodeGenerationDt.AddMinutes(2) > DateTime.Now)
                    return true;
                else
                    return false;
            }
        }
    }
=======================================================================================================================================
=========================================================Configuration=================================================================
using System;
    using System.Data.Entity;
    using System.Data.Entity.Migrations;
    using System.Linq;

    internal sealed class Configuration : DbMigrationsConfiguration<TwoStepAuth.Context>
    {
        public Configuration()
        {
            AutomaticMigrationsEnabled = false;
        }

        protected override void Seed(TwoStepAuth.Context context)
        {
            //  This method will be called after migrating to the latest version.

            // CodeGenerationDt has to be filled or it can be made nullable
            // (DateTime?)

            context.Users.AddOrUpdate(u => u.Username,
                new User
                {
                    Username = "ivan",
                    PasswordHash = Helpers.GetHash("ivanpass"),
                    Telephone = "+79101112233",
                    Email = "ivan@yandex.ru",
                    CodeGenerationDt = new DateTime(2000, 1, 1)
                },
                new User
                {
                    Username = "petya",
                    PasswordHash = Helpers.GetHash("petyapass"),
                    Telephone = "+79102221144",
                    Email = "petya@yandex.ru",
                    CodeGenerationDt = new DateTime(2000, 1, 1)
                }
             );
        }
    }