AuthController.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;
using netcore_postgres_oauth_boiler.Models;

namespace netcore_postgres_oauth_boiler.Controllers
{
    public class AuthController : Controller
    {

        private readonly DatabaseContext _context;

        private readonly ILogger<AuthController> _logger;

        public AuthController(ILogger<AuthController> logger, DatabaseContext context)
        {
            _logger = logger;
            _context = context;
        }
        public IActionResult Login()
        {
            return View();
        }

        public IActionResult Register()
        {
            return View();
        }

        [HttpPost]
        public async Task<IActionResult> Login([FromForm] string email, [FromForm] string password)
        {
            Console.WriteLine($"{email} is logging in.");

            // Loading session
            if (!HttpContext.Session.IsAvailable)
                await HttpContext.Session.LoadAsync();

            // Disallowing already logged-in users
            if (HttpContext.Session.GetString("user") != null)
            {
                ViewData["error"] = "You are already logged in!";
                return View("Login");
            }

            // Fetching the user
            var user = await _context.Users.Where(c => Regex.IsMatch(c.email, email)).FirstOrDefaultAsync();

            // Checking if user exists and verifying password
            if (user == null || !BCrypt.Net.BCrypt.Verify(password, user.password))
            {
                ViewData["error"] = "Incorrect email or password!";
                return View("Login");
            }

            // Attaching user to session
            HttpContext.Session.SetString("user", user.id);

            // Setting info alert to be shown
            ViewData["info"] = "You have logged in!";

            // Rendering index
            return View("~/Views/Home/Index.cshtml");
        }

        [HttpPost]
        public async Task<IActionResult> Register([FromForm] string email, [FromForm] string password)
        {
            // Loading session
            if (!HttpContext.Session.IsAvailable)
                await HttpContext.Session.LoadAsync();

            // Verifying user is not logged in
            if (HttpContext.Session.GetString("user") != null)
            {
                ViewData["error"] = "You are already logged in!";
                return View("Register");
            }

            // Verifying data
            if (email == null || password == null)
            {
                ViewData["error"] = "Missing username or password!";
                return View("Register");
            }

            // Checking for duplicates
            var count = await _context.Users.Where(c => Regex.IsMatch(c.email, email)).CountAsync();
            if (count != 0)
            {
                ViewData["error"] = "This email is already taken!";
                return View("Register");
            }

            // Saving the user
            User u = new User(email, password);
            _context.Users.Add(u);
            await _context.SaveChangesAsync();

            // Assigning user id to session
            HttpContext.Session.SetString("user", u.id);

            // Setting info alert
            ViewData["info"] = "You have successfully registered!";

            return View("~/Views/Home/Index.cshtml");
        }

        [HttpGet]
        public async Task<IActionResult> SessionTest()
        {
            if (!HttpContext.Session.IsAvailable)
                await HttpContext.Session.LoadAsync();
            var c = HttpContext.Session.GetString("user");

            return Ok("You are: " + c ?? "not logged in.");
        }


        [HttpGet]
        public async Task<IActionResult> Logout()
        {
            // Removing session
            if (!HttpContext.Session.IsAvailable)
                await HttpContext.Session.LoadAsync();
            HttpContext.Session.Clear();

            ViewData["info"] = "You have logged out!";
            return View("~/Views/Home/Index.cshtml");
        }

        [ResponseCache(Duration = 0, Location = ResponseCacheLocation.None, NoStore = true)]
        public IActionResult Error()
        {
            return View(new ErrorViewModel { RequestId = Activity.Current?.Id ?? HttpContext.TraceIdentifier });
        }
    }
}