using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Marechai.Database.Models;
using Microsoft.AspNetCore.Authentication;
using Microsoft.AspNetCore.Identity;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;

namespace Marechai.Areas.Identity.Pages.Account.Manage
{
    public class ExternalLoginsModel : PageModel
    {
        readonly SignInManager<ApplicationUser> _signInManager;
        readonly UserManager<ApplicationUser>   _userManager;

        public ExternalLoginsModel(UserManager<ApplicationUser> userManager,
                                   SignInManager<ApplicationUser> signInManager)
        {
            _userManager   = userManager;
            _signInManager = signInManager;
        }

        public IList<UserLoginInfo> CurrentLogins { get; set; }

        public IList<AuthenticationScheme> OtherLogins { get; set; }

        public bool ShowRemoveButton { get; set; }

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

        public async Task<IActionResult> OnGetAsync()
        {
            ApplicationUser user = await _userManager.GetUserAsync(User);

            if(user == null)
            {
                return NotFound("Unable to load user with ID 'user.Id'.");
            }

            CurrentLogins = await _userManager.GetLoginsAsync(user);

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

            ShowRemoveButton = user.PasswordHash != null || CurrentLogins.Count > 1;

            return Page();
        }

        public async Task<IActionResult> OnPostRemoveLoginAsync(string loginProvider, string providerKey)
        {
            ApplicationUser user = await _userManager.GetUserAsync(User);

            if(user == null)
            {
                return NotFound("Unable to load user with ID 'user.Id'.");
            }

            IdentityResult 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 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
            string redirectUrl = Url.Page("./ExternalLogins", "LinkLoginCallback");

            AuthenticationProperties properties =
                _signInManager.ConfigureExternalAuthenticationProperties(provider, redirectUrl,
                                                                         _userManager.GetUserId(User));

            return new ChallengeResult(provider, properties);
        }

        public async Task<IActionResult> OnGetLinkLoginCallbackAsync()
        {
            ApplicationUser user = await _userManager.GetUserAsync(User);

            if(user == null)
            {
                return NotFound("Unable to load user with ID 'user.Id'.");
            }

            ExternalLoginInfo info = await _signInManager.GetExternalLoginInfoAsync(user.Id);

            if(info == null)
            {
                throw new
                    InvalidOperationException($"Unexpected error occurred loading external login info for user with ID '{user.Id}'.");
            }

            IdentityResult 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();
        }
    }
}