using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace LoginSystem
{
    class Program
    {
        static void Main(string[] args)
        {

            Console.WriteLine("This is a protected system. Unautherized access is strictly prohibited. Please login or exit.\n");

            bool loggedIn = false;

            while (loggedIn == false)
            {

                loggedIn = Verification.Login();

            }

            Console.ReadKey();

        }
    }
}


class Database
{

    public static LoginSystem.LoginSystems db = new LoginSystem.LoginSystems();

    public static void AddUser(string username, string password)
    {
            LoginSystem.User NewUser = new LoginSystem.User();
            NewUser.Username = username;
            NewUser.Password = password;
            NewUser.LastLogin = System.DateTime.Now;

            db.Users.Add(NewUser);
            db.SaveChanges();
    }

    public static bool CheckLogin(string username, string password)
    {

        foreach (var User in db.Users)
        {

            if (User.Username == username && User.Password == password)
            {
                Console.WriteLine("\nYou have been successfully logged in.");
                return true;

            } else {

                Console.WriteLine("\nYour username/password is incorrect. Please try again.");
                return false;
            }
        }
        return false;
    }

}


class Verification
{

    public static bool Login()
    {
        Console.Write("Username:"); string username = Console.ReadLine();
        Console.Write("Password:"); string password = Console.ReadLine();

        bool LoginCheck = Database.CheckLogin(username, password);

        return LoginCheck;
    }

}