// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System.ComponentModel.DataAnnotations;
using System.Globalization;
using System.Linq;
using System.Text;
using System.Text.Encodings.Web;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;
using Microsoft.Extensions.Logging;

namespace Microsoft.AspNetCore.Identity.UI.V5.Pages.Account.Manage.Internal;

/// <summary>
///     This API supports the ASP.NET Core Identity default UI infrastructure and is not intended to be used
///     directly from your code. This API may change or be removed in future releases.
/// </summary>
[IdentityDefaultUI(typeof(EnableAuthenticatorModel<>))]
public class EnableAuthenticatorModel : PageModel
{
    /// <summary>
    ///     This API supports the ASP.NET Core Identity default UI infrastructure and is not intended to be used
    ///     directly from your code. This API may change or be removed in future releases.
    /// </summary>
    public string? SharedKey { get; set; }

    /// <summary>
    ///     This API supports the ASP.NET Core Identity default UI infrastructure and is not intended to be used
    ///     directly from your code. This API may change or be removed in future releases.
    /// </summary>
    public string? AuthenticatorUri { get; set; }

    /// <summary>
    ///     This API supports the ASP.NET Core Identity default UI infrastructure and is not intended to be used
    ///     directly from your code. This API may change or be removed in future releases.
    /// </summary>
    [TempData]
    public string[]? RecoveryCodes { get; set; }

    /// <summary>
    ///     This API supports the ASP.NET Core Identity default UI infrastructure and is not intended to be used
    ///     directly from your code. This API may change or be removed in future releases.
    /// </summary>
    [TempData]
    public string? StatusMessage { get; set; }

    /// <summary>
    ///     This API supports the ASP.NET Core Identity default UI infrastructure and is not intended to be used
    ///     directly from your code. This API may change or be removed in future releases.
    /// </summary>
    [BindProperty]
    public InputModel Input { get; set; } = default!;

    /// <summary>
    ///     This API supports the ASP.NET Core Identity default UI infrastructure and is not intended to be used
    ///     directly from your code. This API may change or be removed in future releases.
    /// </summary>
    public class InputModel
    {
        /// <summary>
        ///     This API supports the ASP.NET Core Identity default UI infrastructure and is not intended to be used
        ///     directly from your code. This API may change or be removed in future releases.
        /// </summary>
        [Required]
        [StringLength(7, ErrorMessage = "The {0} must be at least {2} and at max {1} characters long.", MinimumLength = 6)]
        [DataType(DataType.Text)]
        [Display(Name = "Verification Code")]
        public string Code { get; set; } = default!;
    }

    /// <summary>
    ///     This API supports the ASP.NET Core Identity default UI infrastructure and is not intended to be used
    ///     directly from your code. This API may change or be removed in future releases.
    /// </summary>
    public virtual Task<IActionResult> OnGetAsync() => throw new NotImplementedException();

    /// <summary>
    ///     This API supports the ASP.NET Core Identity default UI infrastructure and is not intended to be used
    ///     directly from your code. This API may change or be removed in future releases.
    /// </summary>
    public virtual Task<IActionResult> OnPostAsync() => throw new NotImplementedException();
}

internal sealed class EnableAuthenticatorModel<TUser> : EnableAuthenticatorModel where TUser : class
{
    private readonly UserManager<TUser> _userManager;
    private readonly ILogger<EnableAuthenticatorModel> _logger;
    private readonly UrlEncoder _urlEncoder;

    private const string AuthenticatorUriFormat = "otpauth://totp/{0}:{1}?secret={2}&issuer={0}&digits=6";

    public EnableAuthenticatorModel(
        UserManager<TUser> userManager,
        ILogger<EnableAuthenticatorModel> logger,
        UrlEncoder urlEncoder)
    {
        _userManager = userManager;
        _logger = logger;
        _urlEncoder = urlEncoder;
    }

    public override async Task<IActionResult> OnGetAsync()
    {
        var user = await _userManager.GetUserAsync(User);
        if (user == null)
        {
            return NotFound($"Unable to load user with ID '{_userManager.GetUserId(User)}'.");
        }

        await LoadSharedKeyAndQrCodeUriAsync(user);

        return Page();
    }

    public override async Task<IActionResult> OnPostAsync()
    {
        var user = await _userManager.GetUserAsync(User);
        if (user == null)
        {
            return NotFound($"Unable to load user with ID '{_userManager.GetUserId(User)}'.");
        }

        if (!ModelState.IsValid)
        {
            await LoadSharedKeyAndQrCodeUriAsync(user);
            return Page();
        }

        // Strip spaces and hyphens
        var verificationCode = Input.Code.Replace(" ", string.Empty).Replace("-", string.Empty);

        var is2faTokenValid = await _userManager.VerifyTwoFactorTokenAsync(
            user, _userManager.Options.Tokens.AuthenticatorTokenProvider, verificationCode);

        if (!is2faTokenValid)
        {
            ModelState.AddModelError("Input.Code", "Verification code is invalid.");
            await LoadSharedKeyAndQrCodeUriAsync(user);
            return Page();
        }

        await _userManager.SetTwoFactorEnabledAsync(user, true);
        await _userManager.GetUserIdAsync(user);
        _logger.LogInformation(LoggerEventIds.TwoFAEnabled, "User has enabled 2FA with an authenticator app.");

        StatusMessage = "Your authenticator app has been verified.";

        if (await _userManager.CountRecoveryCodesAsync(user) == 0)
        {
            var recoveryCodes = await _userManager.GenerateNewTwoFactorRecoveryCodesAsync(user, 10);
            RecoveryCodes = recoveryCodes!.ToArray();
            return RedirectToPage("./ShowRecoveryCodes");
        }
        else
        {
            return RedirectToPage("./TwoFactorAuthentication");
        }
    }

    private async Task LoadSharedKeyAndQrCodeUriAsync(TUser user)
    {
        // Load the authenticator key & QR code URI to display on the form
        var unformattedKey = await _userManager.GetAuthenticatorKeyAsync(user);
        if (string.IsNullOrEmpty(unformattedKey))
        {
            await _userManager.ResetAuthenticatorKeyAsync(user);
            unformattedKey = await _userManager.GetAuthenticatorKeyAsync(user);
        }

        SharedKey = FormatKey(unformattedKey!);

        var email = await _userManager.GetEmailAsync(user);
        AuthenticatorUri = GenerateQrCodeUri(email!, unformattedKey!);
    }

    private static string FormatKey(string unformattedKey)
    {
        var result = new StringBuilder();
        int currentPosition = 0;
        while (currentPosition + 4 < unformattedKey.Length)
        {
            result.Append(unformattedKey.AsSpan(currentPosition, 4)).Append(' ');
            currentPosition += 4;
        }
        if (currentPosition < unformattedKey.Length)
        {
            result.Append(unformattedKey.AsSpan(currentPosition));
        }

        return result.ToString().ToLowerInvariant();
    }

    private string GenerateQrCodeUri(string email, string unformattedKey)
    {
        return string.Format(
            CultureInfo.InvariantCulture,
            AuthenticatorUriFormat,
            _urlEncoder.Encode("Microsoft.AspNetCore.Identity.UI"),
            _urlEncoder.Encode(email),
            unformattedKey);
    }
}
