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

using System.Linq;
using Microsoft.AspNetCore.Authentication;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;

namespace Microsoft.AspNetCore.Identity.UI.V4.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(ExternalLoginsModel<>))]
public abstract class ExternalLoginsModel : 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 IList<UserLoginInfo>? CurrentLogins { 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 IList<AuthenticationScheme>? OtherLogins { 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 bool ShowRemoveButton { 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>
    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> OnPostRemoveLoginAsync(string loginProvider, string providerKey) => 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> OnPostLinkLoginAsync(string provider) => 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> OnGetLinkLoginCallbackAsync() => throw new NotImplementedException();
}

internal sealed class ExternalLoginsModel<TUser> : ExternalLoginsModel where TUser : class
{
    private readonly UserManager<TUser> _userManager;
    private readonly SignInManager<TUser> _signInManager;
    private readonly IUserStore<TUser> _userStore;

    public ExternalLoginsModel(
        UserManager<TUser> userManager,
        SignInManager<TUser> signInManager,
        IUserStore<TUser> userStore)
    {
        _userManager = userManager;
        _signInManager = signInManager;
        _userStore = userStore;
    }

    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)}'.");
        }

        CurrentLogins = await _userManager.GetLoginsAsync(user);
        OtherLogins = (await _signInManager.GetExternalAuthenticationSchemesAsync())
            .Where(auth => CurrentLogins.All(ul => auth.Name != ul.LoginProvider))
            .ToList();

        string? passwordHash = null;
        if (_userStore is IUserPasswordStore<TUser> userPasswordStore)
        {
            passwordHash = await userPasswordStore.GetPasswordHashAsync(user, HttpContext.RequestAborted);
        }

        ShowRemoveButton = passwordHash != null || CurrentLogins.Count > 1;
        return Page();
    }

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

        var result = await _userManager.RemoveLoginAsync(user, loginProvider, providerKey);
        if (!result.Succeeded)
        {
            StatusMessage = "The external login was not removed.";
            return RedirectToPage();
        }

        await _signInManager.RefreshSignInAsync(user);
        StatusMessage = "The external login was removed.";
        return RedirectToPage();
    }

    public override async Task<IActionResult> OnPostLinkLoginAsync(string provider)
    {
        // Clear the existing external cookie to ensure a clean login process
        await HttpContext.SignOutAsync(IdentityConstants.ExternalScheme);

        // Request a redirect to the external login provider to link a login for the current user
        var redirectUrl = Url.Page("./ExternalLogins", pageHandler: "LinkLoginCallback");
        var properties = _signInManager.ConfigureExternalAuthenticationProperties(provider, redirectUrl, _userManager.GetUserId(User));
        return new ChallengeResult(provider, properties);
    }

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

        var userId = await _userManager.GetUserIdAsync(user);
        var info = await _signInManager.GetExternalLoginInfoAsync(userId);
        if (info == null)
        {
            throw new InvalidOperationException($"Unexpected error occurred loading external login info.");
        }

        var result = await _userManager.AddLoginAsync(user, info);
        if (!result.Succeeded)
        {
            StatusMessage = "The external login was not added. External logins can only be associated with one account.";
            return RedirectToPage();
        }

        // Clear the existing external cookie to ensure a clean login process
        await HttpContext.SignOutAsync(IdentityConstants.ExternalScheme);

        StatusMessage = "The external login was added.";
        return RedirectToPage();
    }
}
