using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Tango.Core.Commands;
using Tango.PPC.Common;
using Tango.PPC.Common.Navigation;
using SimpleValidator.Extensions;
using System.ComponentModel.DataAnnotations;
using Tango.SharedUI.Helpers;
using Tango.PPC.Common.Authentication;
using Tango.BL.Entities;
using Tango.BL.Enumerations;
using Tango.Logging;

namespace Tango.PPC.UI.ViewModels
{
    /// <summary>
    /// Represents the PPC login view ViewModel.
    /// </summary>
    /// <seealso cref="Tango.PPC.Common.PPCViewModel" />
    public class LoginViewVM : PPCViewModel
    {
        public RelayCommand LoginCommand { get; set; }

        #region Properties

        private String _email;
        /// <summary>
        /// Gets or sets the email.
        /// </summary>
        [Required(ErrorMessage = "Email is required")]
        [EmailAddress(ErrorMessage = "Please enter a valid email address")]
        public String Email
        {
            get { return _email; }
            set { _email = value; RaisePropertyChangedAuto(); }
        }

        private String _password;
        /// <summary>
        /// Gets or sets the password.
        /// </summary>
        [Required(ErrorMessage = "Password is required")]
        public String Password
        {
            get { return _password; }
            set { _password = value; RaisePropertyChangedAuto(); }
        }

        private bool _isLoading;
        /// <summary>
        /// Gets or sets a value indicating whether the application is busy with loading modules.
        /// </summary>
        public bool IsLoading
        {
            get { return _isLoading; }
            set { _isLoading = value; RaisePropertyChangedAuto(); }
        }

        #endregion

        #region Constructors

        /// <summary>
        /// Initializes a new instance of the <see cref="LoginViewVM"/> class.
        /// </summary>
        public LoginViewVM()
        {
            LoginCommand = new RelayCommand(Login);

            Email = "roy@twine-s.com";
            Password = "1234";
        }

        #endregion

        #region Override Methods

        /// <summary>
        /// Called when the application has been started.
        /// </summary>
        public override void OnApplicationStarted()
        {
            AuthenticationProvider.CurrentUserChanged += AuthenticationProvider_CurrentUserChanged;
        }

        public override async void OnApplicationReady()
        {
            base.OnApplicationReady();

            await Task.Delay(500);

            if (!AuthenticationProvider.AuthenticationRequired)
            {
                LogManager.Log("Application is ready! Navigating to home module...");
                await NavigationManager.NavigateTo(NavigationView.HomeModule);
                IsLoading = false;
            }
            else if (AuthenticationProvider.CurrentUser != null && AuthenticationProvider.CurrentUser.HasPermission(Permissions.RunPPC))
            {
                LogManager.Log("Application is ready! Navigating to home module...");
                await NavigationManager.NavigateTo(NavigationView.HomeModule);
                IsLoading = false;
            }
            else
            {
                LogManager.Log("Application is ready! The logged in user does not have permission to run the application!", LogCategory.Warning);
                await NavigationManager.NavigateTo(NavigationView.NoPermissionsView);
                IsLoading = false;
            }
        }

        #endregion

        #region Event Handlers

        /// <summary>
        /// Handles the <see cref="IAuthenticationProvider.CurrentUserChanged"/> event.
        /// </summary>
        /// <param name="sender">The sender.</param>
        /// <param name="user">The user.</param>
        private void AuthenticationProvider_CurrentUserChanged(object sender, User user)
        {
            if (user == null)
            {
                Password = String.Empty;
            }
        }

        #endregion

        #region Private Methods

        /// <summary>
        /// Login to the application using the user name and password.
        /// </summary>
        private async void Login()
        {
            LogManager.Log("Login command pressed.");

            if (Validate())
            {
                IsLoading = true;
                UIHelper.DoEvents();

                var user = await AuthenticationProvider.Login(Email, Password);

                if (user == null)
                {
                    IsLoading = false;
                    await NotificationProvider.ShowWarning("Email or password are incorrect.");
                }
            }
            else
            {
                LogManager.Log("Invalid user credentials.");
            }
        }

        #endregion
    }
}