// Copyright (c) Brock Allen & Dominick Baier. All rights reserved.
// Licensed under the Apache License, Version 2.0. See LICENSE in the project root for license information.

using Microsoft.AspNetCore.Authentication;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Identity;
using Microsoft.AspNetCore.Mvc;
using nuget_host.Models;
using System;
using System.Linq;
using System.Threading.Tasks;

namespace nuget_host.Controllers
{
    [AllowAnonymous]
    public class AccountController : Controller
    {       
        private readonly IAuthenticationSchemeProvider _schemeProvider;

        private readonly SignInManager<ApplicationUser> _signInManager;
        private readonly UserManager<ApplicationUser> _userManager;

        public AccountController(
            IAuthenticationSchemeProvider schemeProvider,
            SignInManager<ApplicationUser> signInManager,
            UserManager<ApplicationUser> userManager)
        {
            _schemeProvider = schemeProvider;
            _signInManager = signInManager;
            _userManager = userManager;
        }

        /// <summary>
        /// Entry point into the login workflow
        /// </summary>
        [HttpGet]
        public async Task<IActionResult> Login(string returnUrl)
        {
            // build a model so we know what to show on the login page
            var vm = await BuildLoginViewModelAsync(returnUrl);

            if (vm.IsExternalLoginOnly)
            {
                // we only have one option for logging in and it's an external provider
                return RedirectToAction("Challenge", "External", new { scheme = vm.ExternalLoginScheme, returnUrl });
            }

            return View(vm);
        }

        /// <summary>
        /// Handle postback from username/password login
        /// </summary>
        [HttpPost]
        [ValidateAntiForgeryToken]
        public async Task<IActionResult> Login(LoginInputModel model, string button)
        {
          
            // the user clicked the "cancel" button
            if (button != "login")
            {
               
                // since we don't have a valid context, then we just go back to the home page
                return Redirect("~/");
            }

            if (ModelState.IsValid)
            {
                // validate username/password
                var user = await _userManager.FindByNameAsync(model.Username);
                var signResult = await _signInManager.CheckPasswordSignInAsync(user, model.Password, true);

                if (signResult.Succeeded)
                {
                    
                    // only set explicit expiration here if user chooses "remember me". 
                    // otherwise we rely upon expiration configured in cookie middleware.
                    AuthenticationProperties props = null;
                    if (AccountOptions.AllowRememberLogin && model.RememberLogin)
                    {
                        props = new AuthenticationProperties
                        {
                            IsPersistent = true,
                            ExpiresUtc = DateTimeOffset.UtcNow.Add(AccountOptions.RememberMeLoginDuration)
                        };
                    };
                    
                    await _signInManager.SignInAsync(user, model.RememberLogin && AccountOptions.AllowRememberLogin);
                    if (Url.IsLocalUrl(model.ReturnUrl))
                    {
                        return Redirect(model.ReturnUrl);
                    }
                    else if (string.IsNullOrEmpty(model.ReturnUrl))
                    {
                        return Redirect("~/");
                    }
                    else
                    {
                        // user might have clicked on a malicious link - should be logged
                        throw new Exception("invalid return URL");
                    }
                }

                ModelState.AddModelError(string.Empty, AccountOptions.InvalidCredentialsErrorMessage);
            }

            // something went wrong, show form with error
            var vm = await BuildLoginViewModelAsync(model);
            return View(vm);
        }

        
        /// <summary>
        /// Show logout page
        /// </summary>
        [HttpGet]
        public async Task<IActionResult> Logout(string logoutId)
        {
            // build a model so the logout page knows what to display
            var vm = await BuildLogoutViewModelAsync(logoutId);

            if (vm.ShowLogoutPrompt == false)
            {
                // if the request for logout was properly authenticated from IdentityServer, then
                // we don't need to show the prompt and can just log the user out directly.
                return await Logout(vm);
            }

            return View(vm);
        }

        /// <summary>
        /// Handle logout page postback
        /// </summary>
        [HttpPost]
        [ValidateAntiForgeryToken]
        public async Task<IActionResult> Logout(LogoutInputModel model)
        {
            // build a model so the logged out page knows what to display
            var vm = await BuildLoggedOutViewModelAsync(model.LogoutId);

            if (User?.Identity.IsAuthenticated == true)
            {
                // delete local authentication cookie
                await HttpContext.SignOutAsync();
            }

            // check if we need to trigger sign-out at an upstream identity provider
            if (vm.TriggerExternalSignout)
            {
                // build a return URL so the upstream provider will redirect back
                // to us after the user has logged out. this allows us to then
                // complete our single sign-out processing.
                string url = Url.Action("Logout", new { logoutId = vm.LogoutId });

                // this triggers a redirect to the external provider for sign-out
                return SignOut(new AuthenticationProperties { RedirectUri = url }, vm.ExternalAuthenticationScheme);
            }
            
            return View("LoggedOut", vm);
        }

        [HttpGet]
        public IActionResult AccessDenied()
        {
            return new BadRequestObjectResult(403);
        }


        /*****************************************/
        /* helper APIs for the AccountController */
        /*****************************************/
        private async Task<LoginViewModel> BuildLoginViewModelAsync(string returnUrl)
        {
            

            var schemes = await _schemeProvider.GetAllSchemesAsync();

            var providers = schemes
                .Where(x => x.DisplayName != null)
                .Select(x => new ExternalProvider
                {
                    DisplayName = x.DisplayName ?? x.Name,
                    AuthenticationScheme = x.Name
                }).ToList();

            var allowLocal = true;
            

            return new LoginViewModel
            {
                AllowRememberLogin = AccountOptions.AllowRememberLogin,
                EnableLocalLogin = allowLocal && AccountOptions.AllowLocalLogin,
                ReturnUrl = returnUrl,
                ExternalProviders = providers.ToArray()
            };
        }

        private async Task<LoginViewModel> BuildLoginViewModelAsync(LoginInputModel model)
        {
            var vm = await BuildLoginViewModelAsync(model.ReturnUrl);
            vm.Username = model.Username;
            vm.RememberLogin = model.RememberLogin;
            return vm;
        }

        private async Task<LogoutViewModel> BuildLogoutViewModelAsync(string logoutId)
        {
            var vm = new LogoutViewModel { LogoutId = logoutId, ShowLogoutPrompt = AccountOptions.ShowLogoutPrompt };

            if (User?.Identity.IsAuthenticated != true)
            {
                // if the user is not authenticated, then just show logged out page
                vm.ShowLogoutPrompt = false;
                return vm;
            }

            // show the logout prompt. this prevents attacks where the user
            // is automatically signed out by another malicious web page.
            return vm;
        }

        private async Task<LoggedOutViewModel> BuildLoggedOutViewModelAsync(string logoutId)
        {
           
            var vm = new LoggedOutViewModel
            {
                AutomaticRedirectAfterSignOut = AccountOptions.AutomaticRedirectAfterSignOut,
                LogoutId = logoutId
            };
        
            return vm;
        }
    }
}