using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Threading.Tasks;
using System.Windows.Input;
using Plugin.Connectivity;
using Serilog;
using TINK.Model;
using TINK.Model.User;
using TINK.Model.User.Account;
using TINK.MultilingualResources;
using TINK.Repository.Exception;
using TINK.View;
using TINK.ViewModel.Map;
using Xamarin.Forms;

namespace TINK.ViewModel
{
	public class LoginPageViewModel : INotifyPropertyChanged
	{
		/// <summary>
		/// Reference on view service to show modal notifications and to perform navigation.
		/// </summary>
		private readonly IViewService m_oViewService;

#if BACKSTYLE
        /// <summary> Reference to naviagion object to navigate back to map page when login succeeded. </summary>
        private INavigation m_oNavigation;
#endif
		/// <summary> Reference on the tink app instance. </summary>
		private ITinkApp TinkApp { get; }

		/// <summary>
		/// Holds the mail address candidate being entered by user.
		/// </summary>
		private string m_strMailAddress;

		/// <summary>
		/// Holds the password candidate being entered by user.
		/// </summary>
		private string m_strPassword;

		private bool m_bMailAndPasswordCandidatesOk = false;

		/// <summary> Holds a reference to the external trigger service. </summary>
		private Action<string> OpenUrlInExternalBrowser { get; }

		/// <summary>
		/// Event which notifies clients about changed properties.
		/// </summary>
		public event PropertyChangedEventHandler PropertyChanged;

		/// <summary>
		/// 
		/// </summary>
		/// <param name="p_oSetCredentials">Delegate to set new mail address and password to model.</param>
		/// <param name="p_oUser">Mail address of user if login succeeded.</param>
		/// <param name="openUrlInExternalBrowser">Action to open an external browser.</param>
		/// <param name="p_oViewService">Interface to actuate methods on GUI.</param>
		/// <param name="p_oNavigation">Interface to navigate.</param>
		public LoginPageViewModel(
			ITinkApp tinkApp,
			Action<string> openUrlInExternalBrowser,
#if !BACKSTYLE
			IViewService p_oViewService)
#else
            IViewService p_oViewService,
            INavigation p_oNavigation)
#endif
		{
			TinkApp = tinkApp
				?? throw new ArgumentException("Can not instantiate map page view model- object. No tink app object available.");

			OpenUrlInExternalBrowser = openUrlInExternalBrowser
				?? throw new ArgumentException("Can not instantiate login page view model- object. No user external browse service available.");

			m_oViewService = p_oViewService
				?? throw new ArgumentException("Can not instantiate login page view model- object. No view available.");
#if BACKSTYLE
            m_oNavigation = p_oNavigation
                ?? throw new ArgumentException("Can not instantiate login page view model- object. No navigation service available.");
#endif

			m_strMailAddress = tinkApp.ActiveUser.Mail;
			m_strPassword = tinkApp.ActiveUser.Password;

			IsRegisterTargetsInfoVisible = new List<string> { Model.Services.CopriApi.ServerUris.CopriServerUriList.TINK_LIVE, Model.Services.CopriApi.ServerUris.CopriServerUriList.TINK_DEVEL }.Contains(tinkApp.Uris.ActiveUri.AbsoluteUri);

			tinkApp.ActiveUser.StateChanged += OnStateChanged;
		}

		/// <summary>
		/// Login state changed.
		/// </summary>
		/// <param name="p_oSender"></param>
		/// <param name="p_oEventArgs"></param>
		private void OnStateChanged(object p_oSender, EventArgs p_oEventArgs)
		{
			var l_oPropertyChanged = PropertyChanged;
			if (l_oPropertyChanged != null)
			{
				l_oPropertyChanged(this, new PropertyChangedEventArgs(nameof(IsLoggedOut)));
				l_oPropertyChanged(this, new PropertyChangedEventArgs(nameof(IsLoginRequestAllowed)));
			}
		}

		/// <summary> Gets a value indicating whether user is logged out or not.</summary>
		public bool IsLoggedOut { get { return !TinkApp.ActiveUser.IsLoggedIn; } }

		/// <summary> Gets a value indicating whether user can try to login.</summary>
		public bool IsLoginRequestAllowed
		{
			get
			{
				return !TinkApp.ActiveUser.IsLoggedIn
					&& m_bMailAndPasswordCandidatesOk;
			}
		}

		/// <summary> Gets mail address of user.</summary>
		public string MailAddress
		{
			get
			{
				return m_strMailAddress;
			}

			set
			{
				m_strMailAddress = value;
				UpdateAndFireIfRequiredOnEnteringMailOrPwd();
			}
		}

		/// <summary> Gets password user.</summary>
		public string Password
		{
			get
			{
				return m_strPassword;
			}

			set
			{
				m_strPassword = value;
				UpdateAndFireIfRequiredOnEnteringMailOrPwd();
			}
		}

		/// <summary>Update on password or mailaddress set. </summary>
		private void UpdateAndFireIfRequiredOnEnteringMailOrPwd()
		{
			var l_bLastMailAndPasswordCandidatesOk = m_bMailAndPasswordCandidatesOk;

			m_bMailAndPasswordCandidatesOk = Validator.ValidateMailAndPasswordDelegate(MailAddress, Password).ValidElement == Elements.Account;

			if (m_bMailAndPasswordCandidatesOk != l_bLastMailAndPasswordCandidatesOk)
			{
				PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(IsLoginRequestAllowed)));
			}
		}

		/// <summary>
		/// Command object to bind login button to view model.
		/// </summary>
		public ICommand OnLoginRequest
		{
			get
			{
				return new Command(async () => await Login());
			}
		}

		/// <summary> Processes request to register a new user. </summary>
		public ICommand OnRegisterRequest => new Command(async () =>
		{
			if (CrossConnectivity.Current.IsConnected)
			{
				await m_oViewService.PushAsync(ViewTypes.RegisterPage);
			}
			else
			{
				await m_oViewService.DisplayAlert(
					AppResources.MessageTitleHint,
					AppResources.MessageLoginRegisterNoNet,
					AppResources.MessageAnswerOk);
			}
		});

		/// <summary> Processes request to recover password. </summary>
		public ICommand OnPasswordForgottonRequest => new Command(async () =>
		{
			if (CrossConnectivity.Current.IsConnected)
			{
				await m_oViewService.PushAsync(ViewTypes.PasswordForgottenPage);
			}
			else
			{
				await m_oViewService.DisplayAlert(
					AppResources.MessageTitleHint,
					AppResources.MessageLoginRecoverPassword,
					AppResources.MessageAnswerOk);
			}
		});

		/// <summary>
		/// User request to log in.
		/// </summary>
#if BACKSTYLE
        public async void Login()
#else
		public async Task Login()
#endif
		{
			IAccount account = new EmptyAccount();
			try
			{
				Log.ForContext<LoginPageViewModel>().Information("User taped login button.");

				try
				{
					TinkApp.ActiveUser.CheckIsPasswordValid(MailAddress, Password);

					// Do login.
					account = await TinkApp.GetConnector(CrossConnectivity.Current.IsConnected).Command.DoLogin(MailAddress, Password, TinkApp.ActiveUser.DeviceId);

					await TinkApp.ActiveUser.Login(account);

					// Update map page filter because user might be of both groups TINK an Konrad.
					TinkApp.GroupFilterMapPage =
						GroupFilterMapPageHelper.CreateUpdated(
							TinkApp.GroupFilterMapPage,
							TinkApp.ActiveUser.DoFilter(TinkApp.FilterGroupSetting.DoFilter()));

					// Update settings page filter because user might be of both groups TINK an Konrad.
					TinkApp.FilterGroupSetting.DoFilter(TinkApp.ActiveUser.Group);

					// Persist new settings.
					TinkApp.Save();

					TinkApp.UpdateConnector();
				}
				catch (InvalidAuthorizationResponseException l_oException)
				{
					// Copri response is invalid.
					Log.ForContext<LoginPageViewModel>().Error("Login failed (invalid. auth. response). {@l_oException}.", l_oException);

					await m_oViewService.DisplayAlert(
						AppResources.MessageLoginErrorTitle,
						l_oException.Message,
						AppResources.MessageAnswerOk);

					return;
				}
				catch (UnsupportedCopriVersionDetectedException)
				{
					await m_oViewService.DisplayAlert(
						AppResources.MessageLoginErrorTitle,
						 string.Format(
							 AppResources.MessageAppVersionIsOutdated,
							 TinkApp.Flavor.GetDisplayName()),
						AppResources.MessageAnswerOk);

					return;
				}
				catch (Exception l_oException)
				{
					// Copri server is not reachable.
					if (l_oException is WebConnectFailureException)
					{
						Log.ForContext<LoginPageViewModel>().Information("Login failed (web communication exception). {@l_oException}.", l_oException);

						await m_oViewService.DisplayAlert(
							AppResources.MessageLoginConnectionErrorTitle,
							string.Format("{0}\r\n{1}", l_oException.Message, WebConnectFailureException.GetHintToPossibleExceptionsReasons),
							AppResources.MessageAnswerOk);
					}
					else if (l_oException is UsernamePasswordInvalidException)
					{
						// Cookie is empty.
						Log.ForContext<LoginPageViewModel>().Error("Login failed (empty cookie). {@l_oException}.", l_oException);
						await m_oViewService.DisplayAlert(
							AppResources.MessageLoginErrorTitle,
							string.Format(AppResources.MessageLoginConnectionErrorMessage, l_oException.Message),
							"OK");
					}
					else
					{
						Log.ForContext<LoginPageViewModel>().Error("Login failed. {@l_oException}.", l_oException);
						await m_oViewService.DisplayAlert(
							AppResources.MessageLoginErrorTitle,
							l_oException.Message,
							AppResources.MessageAnswerOk);
					}

					return;
				}

				// Display information that login succeeded.
				Log.ForContext<LoginPageViewModel>().Information("Login succeeded. {@tinkApp.ActiveUser}.", TinkApp.ActiveUser);

				var title = TinkApp.ActiveUser.Group.Intersect(new List<string> { Model.Connector.FilterHelper.CARGOBIKE, Model.Connector.FilterHelper.CITYBIKE }).Any()
					? string.Format(AppResources.MessageLoginWelcomeTitleGroup, TinkApp.ActiveUser.GetUserGroupDisplayName())
					: string.Format(AppResources.MessageLoginWelcomeTitle);

				await m_oViewService.DisplayAlert(
					title,
					string.Format(AppResources.MessageLoginWelcome, TinkApp.ActiveUser.Mail),
					AppResources.MessageAnswerOk);
			}
			catch (Exception p_oException)
			{
				Log.ForContext<LoginPageViewModel>().Error("An unexpected error occurred displaying log out page. {@Exception}", p_oException);
				return;
			}

			try
			{
				if (!TinkApp.ActiveUser.Group.Contains(Model.Connector.FilterHelper.CARGOBIKE))
				{
					// No need to show "Anleitung TINK Räder" because user can not use tink.
#if USEFLYOUT

                    m_oViewService.ShowPage(account.IsAgbAcknowledged ? ViewTypes.MapPage : ViewTypes.ManageAccountPage); 
#else
					await m_oViewService.ShowPage("//MapPage");
#endif
					return;
				}

				// Switch to map page
#if USEFLYOUT
                m_oViewService.ShowPage(ViewTypes.BikeInfoCarouselPage, AppResources.MarkingLoginInstructions);
#else
				await m_oViewService.ShowPage("//MapPage");
#endif
			}
			catch (Exception p_oException)
			{
				Log.ForContext<LoginPageViewModel>().Error("Ein unerwarteter Fehler ist auf der Seite Anleitung TINK Räder (nach Anmeldeseite) aufgetreten. {@Exception}", p_oException);
				return;
			}

#if BACKSTYLE
                // Navigate back to map page.
                await m_oNavigation.PopToRootAsync();
#endif
		}

		/// <summary> Holds whether TINK/ Copri info is shown.</summary>
		public bool IsRegisterTargetsInfoVisible { get; private set; }

		/// <summary> Text providing info about TINK/ konrad registration. </summary>
		public FormattedString RegisterTargetsInfo
		{
			get
			{
				var l_oHint = new FormattedString();
				l_oHint.Spans.Add(new Span { Text = AppResources.MarkingLoginInstructionsTinkKonradTitle });
				l_oHint.Spans.Add(new Span { Text = AppResources.MarkingLoginInstructionsTinkKonradMessage });

				return l_oHint;
			}
		}

		/// <summary> Opens login page.</summary>
		public void RegisterRequest(string url)
		{
			try
			{
				OpenUrlInExternalBrowser(url);
			}
			catch (Exception p_oException)
			{
				Log.Error("Ein unerwarteter Fehler ist auf der Login Seite beim Öffnen eines Browsers, Seite {url}, aufgetreten. {@Exception}", url, p_oException);
				return;
			}
		}
	}
}