<--LoginControler-->
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using WellnessAndSpaCentar.web.Models;
using WellnessAndSpaCentar.web.ViewModels;
using WellnessAndSpaCentar.web.Helper;
using Microsoft.AspNetCore.Mvc.ModelBinding;
using Microsoft.AspNetCore.Http;

namespace WellnessAndSpaCentar.web.Controllers
{
    public class LoginController : Controller
    {
        private Wellness___spa_centar___RSIContext ctx = new Wellness___spa_centar___RSIContext();
        public IActionResult LoginPage()
        {

            if (Authentication.GetLoggedUser(HttpContext) != null)
                return RedirectToAction("");

            return View("LoginPage", new LoginVM());
        }
        public IActionResult VerifyRequest(LoginVM model)
        {
            User user = ctx.User.Where(x => x.UserName == model.LoginData).FirstOrDefault();
            if(user == null)
            {
                ModelState.AddModelError("", "User does not exist!");
            }
            else
            {
                if(!Security.UserExist(model.LoginData, model.Password, user))
                {
                    ModelState.AddModelError("", "Username or password is incorrect!");
                }
            }
            if (!ModelState.IsValid)
            {
                return View("LoginPage", model);
            }
            Authentication.NewSession(user, HttpContext); //httpContext je null
            return RedirectToAction("Index", "Home");
        }
    }
}




<--Folder: Helper, Klasa: Autentifikacija-->
using Microsoft.AspNetCore.Http;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using WellnessAndSpaCentar.web.Models;

namespace WellnessAndSpaCentar.web.Helper
{
    public class Authentication
    {
        //Authentication is the act of confirming the truth of an attribute of a single piece of data claimed true by an entity.
        private const string _loggedUser = "logged_user";
        private IHttpContextAccessor _httpContextAccessor;
        public Authentication(IHttpContextAccessor httpContextAccessor)
        {
            this._httpContextAccessor = httpContextAccessor;
        }
        public static void NewSession(User user, HttpContext ctx)
        {
            ctx.Session.SetJson(_loggedUser, user);
        }
        public static void EndSession(User user, HttpContext ctx)
        {
            ctx.Session.SetJson(_loggedUser, null);
            // ukoliko ne bude prihvatao null koristiti ovu komandu -> ctx.Session.SetString(_loggedUser, "");
        }
        public static User GetLoggedUser(HttpContext ctx)
        {
            User user = ctx.Session.GetJson<User>(_loggedUser);
            if(user != null)
            {
                return user;
            }
            NewSession(user, ctx);
            return user;
        }
    }
}




<--folder Helper, klasa Autorizacija-->
using Microsoft.AspNetCore.Mvc.Filters;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using WellnessAndSpaCentar.web.Models;

namespace WellnessAndSpaCentar.web.Helper
{
    public class Authorization
    {
        //Authorization is the function of specifying access rights/privileges to resources
        private readonly bool _allUsers;
        public Authorization(bool allUsers)
        {
            _allUsers = allUsers;
        }
        public void OnAuthoritazion(AuthorizationFilterContext context)
        {
            User user = Authentication.GetLoggedUser(context.HttpContext);
            if(user == null)
            {
                context.HttpContext.Response.Redirect("/Login/LoginPage");//neka akcija
                return;
            }
            if(_allUsers && user.Active)
            {
                return;
            }
            if(!_allUsers && user.Active && user.RoleId == 1) //provjera da li je administrator
            {
                return;
            }
            if (!_allUsers && user.Active && user.RoleId == 2) //provjera da li je employee
            {
                return;
            }
            if (!_allUsers && user.Active && user.RoleId == 3) //provjera da li je client
            {
                return;
            }
            if (!_allUsers && user.Active && user.RoleId == 4) //provjera da li je supplier
            {
                return;
            }
            context.HttpContext.Response.Redirect("/Login/LoginPage");
        }
    }
}


<--folder Helper, klasa Security-->
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using WellnessAndSpaCentar.web.Models;

namespace WellnessAndSpaCentar.web.Helper
{
    public class Security
    {
        public static bool UserExist(string username, string password, User user)
        {
            if(user.UserName == username && user.Password == password)
            {
                return true;
            }
            return false;
        }
    }
}


<--folder Helper, klasa Session-->
using Microsoft.AspNetCore.Http;
using Newtonsoft.Json;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace WellnessAndSpaCentar.web.Helper
{
    public static class SessionExtension
    {
        public static void SetJson(this ISession session, string key, object value) => session.SetString(key, JsonConvert.SerializeObject(value));
        public static T GetJson<T>(this ISession session, string key) => session.GetString(key) == null ? default(T) : JsonConvert.DeserializeObject<T>(session.GetString(key));
    }
}


<-- folder Viewv, klasa LoginPage-->
@{
    Layout = "_Layout";
}

@model WellnessAndSpaCentar.web.ViewModels.LoginVM

<body>
    <div class="login-div">
        <div class="login-content">
            <img src="~/images/logo-white.png" alt="Logo" style="width:150px; height:150px;" />
            <h5 style="color:white; text-transform:uppercase; font-size:24px;">Wellness & spa center</h5>
            <form name="login-form" asp-action="VerifyRequest" method="post" onsubmit="validateForm()">

                <br />
                <input asp-for="LoginData" name="LoginData" class="form-control" placeholder="Username" autofocus /><br/>
                <input asp-for="Password" name="Password" class="form-control" placeholder="Password"/><br />
                <button type="submit" class="btn btn-primary">Login</button><br /><br />
                @if (!ViewData.ModelState.IsValid)
                {
                    <div asp-validation-summary="All" class="alert alert-danger"> </div>
                }
            </form>
        </div>
    </div>

</body>