TheInfinityIQ_GCP/src/gcp-backend/GCP.Api/Areas/Identity/Pages/Account/ExternalLogin.cshtml.cs
#nullable disable

using System.ComponentModel.DataAnnotations;
using System.Security.Claims;
using System.Text;
using System.Text.Encodings.Web;

using GCP.Api.Data.Entities;

using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Identity;
using Microsoft.AspNetCore.Identity.UI.Services;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;
using Microsoft.AspNetCore.WebUtilities;

namespace GCP.Api.Areas.Identity.Pages.Account
{
	[AllowAnonymous]
	public class ExternalLoginModel : PageModel
	{
		private readonly SignInManager<User> _signInManager;
		private readonly UserManager<User> _userManager;
		private readonly IUserStore<User> _userStore;
		private readonly IUserEmailStore<User> _emailStore;
		private readonly IEmailSender _emailSender;
		private readonly ILogger<ExternalLoginModel> _logger;

		public ExternalLoginModel(
			SignInManager<User> signInManager,
			UserManager<User> userManager,
			IUserStore<User> userStore,
			ILogger<ExternalLoginModel> logger,
			IEmailSender emailSender)
		{
			_signInManager = signInManager;
			_userManager = userManager;
			_userStore = userStore;
			_emailStore = GetEmailStore();
			_logger = logger;
			_emailSender = emailSender;
		}

		[BindProperty]
		public InputModel Input { get; set; }

		public string ProviderDisplayName { get; set; }
		public string ReturnUrl { get; set; }

		[TempData]
		public string ErrorMessage { get; set; }

		public class InputModel
		{
			[Required]
			[EmailAddress]
			public string Email { get; set; }
		}

		public IActionResult OnGet() => RedirectToPage("./Login");

		public IActionResult OnPost(string provider, string returnUrl = null)
		{
			// Request a redirect to the external login provider.
			var redirectUrl = Url.Page("./ExternalLogin", pageHandler: "Callback", values: new { returnUrl });
			var properties = _signInManager.ConfigureExternalAuthenticationProperties(provider, redirectUrl);
			return new ChallengeResult(provider, properties);
		}

		public async Task<IActionResult> OnGetCallbackAsync(string returnUrl = null, string remoteError = null)
		{
			returnUrl ??= Url.Content("~/");
			if (remoteError is not null)
			{
				ErrorMessage = $"Error from external provider: {remoteError}";
				return RedirectToPage("./Login", new { ReturnUrl = returnUrl });
			}
			var info = await _signInManager.GetExternalLoginInfoAsync();
			if (info is null)
			{
				ErrorMessage = "Error loading external login information.";
				return RedirectToPage("./Login", new { ReturnUrl = returnUrl });
			}

			// Sign in the user with this external login provider if the user already has a login.
			var result = await _signInManager.ExternalLoginSignInAsync(info.LoginProvider, info.ProviderKey, isPersistent: false, bypassTwoFactor: true);
			if (result.Succeeded)
			{
				_logger.LogInformation("{Name} logged in with {LoginProvider} provider.", info.Principal.Identity.Name, info.LoginProvider);
				return LocalRedirect(returnUrl);
			}
			if (result.IsLockedOut)
			{
				return RedirectToPage("./Lockout");
			}
			else
			{
				// If the user does not have an account, then ask the user to create an account.
				ReturnUrl = returnUrl;
				ProviderDisplayName = info.ProviderDisplayName;
				if (info.Principal.HasClaim(c => c.Type == ClaimTypes.Email))
				{
					Input = new InputModel
					{
						Email = info.Principal.FindFirstValue(ClaimTypes.Email)
					};
				}
				return Page();
			}
		}

		public async Task<IActionResult> OnPostConfirmationAsync(string returnUrl = null)
		{
			returnUrl ??= Url.Content("~/");
			// Get the information about the user from the external login provider
			var info = await _signInManager.GetExternalLoginInfoAsync();
			if (info is null)
			{
				ErrorMessage = "Error loading external login information during confirmation.";
				return RedirectToPage("./Login", new { ReturnUrl = returnUrl });
			}

			if (ModelState.IsValid)
			{
				var user = CreateUser();

				await _userStore.SetUserNameAsync(user, Input.Email, CancellationToken.None);
				await _emailStore.SetEmailAsync(user, Input.Email, CancellationToken.None);

				var result = await _userManager.CreateAsync(user);
				if (result.Succeeded)
				{
					result = await _userManager.AddLoginAsync(user, info);
					if (result.Succeeded)
					{
						_logger.LogInformation("User created an account using {Name} provider.", info.LoginProvider);

						var userId = await _userManager.GetUserIdAsync(user);
						var code = await _userManager.GenerateEmailConfirmationTokenAsync(user);
						code = WebEncoders.Base64UrlEncode(Encoding.UTF8.GetBytes(code));
						var callbackUrl = Url.Page(
							"/Account/ConfirmEmail",
							pageHandler: null,
							values: new { area = "Identity", userId, code },
							protocol: Request.Scheme);

						await _emailSender.SendEmailAsync(Input.Email, "Confirm your email",
							$"Please confirm your account by <a href='{HtmlEncoder.Default.Encode(callbackUrl)}'>clicking here</a>.");

						// If account confirmation is required, we need to show the link if we don't have a real email sender
						if (_userManager.Options.SignIn.RequireConfirmedAccount)
						{
							return RedirectToPage("./RegisterConfirmation", new { Input.Email });
						}

						await _signInManager.SignInAsync(user, isPersistent: false, info.LoginProvider);
						return LocalRedirect(returnUrl);
					}
				}
				foreach (var error in result.Errors)
				{
					ModelState.AddModelError(string.Empty, error.Description);
				}
			}

			ProviderDisplayName = info.ProviderDisplayName;
			ReturnUrl = returnUrl;
			return Page();
		}

		private User CreateUser()
		{
			try
			{
				return Activator.CreateInstance<User>();
			}
			catch
			{
				throw new InvalidOperationException($"Can't create an instance of '{nameof(User)}'. " +
					$"Ensure that '{nameof(User)}' is not an abstract class and has a parameterless constructor, or alternatively " +
					$"override the external login page in /Areas/Identity/Pages/Account/ExternalLogin.cshtml");
			}
		}

		private IUserEmailStore<User> GetEmailStore()
		{
			if (!_userManager.SupportsUserEmail)
			{
				throw new NotSupportedException("The default UI requires a user store with email support.");
			}
			return (IUserEmailStore<User>)_userStore;
		}
	}
}
