using System.Windows;
using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using HC_APTBS.Services;

namespace HC_APTBS.ViewModels.Dialogs
{
    /// <summary>
    /// ViewModel for the user authentication dialog shown before report generation.
    /// Validates operator credentials against the stored user list.
    /// </summary>
    public sealed partial class UserCheckViewModel : ObservableObject
    {
        private readonly IConfigurationService _config;

        /// <summary>Initialises the dialog, optionally pre-filling the last used username.</summary>
        public UserCheckViewModel(IConfigurationService config, string lastUsername = "")
        {
            _config   = config;
            _username = lastUsername;
        }

        // ── Bindable properties ───────────────────────────────────────────────────

        /// <summary>Username entered by the operator.</summary>
        [ObservableProperty]
        [NotifyCanExecuteChangedFor(nameof(AcceptCommand))]
        private string _username = string.Empty;

        /// <summary>Password entered by the operator (set from code-behind PasswordChanged handler).</summary>
        [ObservableProperty]
        [NotifyCanExecuteChangedFor(nameof(AcceptCommand))]
        private string _password = string.Empty;

        // ── Dialog result ─────────────────────────────────────────────────────────

        /// <summary>True if the user authenticated successfully.</summary>
        public bool Accepted { get; private set; }

        /// <summary>The validated username, available after <see cref="Accepted"/> is true.</summary>
        public string AuthenticatedUser { get; private set; } = string.Empty;

        // ── Commands ──────────────────────────────────────────────────────────────

        /// <summary>Validates credentials and closes the dialog on success.</summary>
        [RelayCommand(CanExecute = nameof(CanAccept))]
        private void Accept()
        {
            if (_config.ValidateUser(Username, Password))
            {
                AuthenticatedUser = Username;
                Accepted = true;
                RequestClose?.Invoke();
            }
            else
            {
                MessageBox.Show(
                    "Invalid username or password.\n(Both are case-sensitive.)",
                    "Authentication Error",
                    MessageBoxButton.OK,
                    MessageBoxImage.Stop);
            }
        }

        private bool CanAccept() => !string.IsNullOrWhiteSpace(Username)
                                 && !string.IsNullOrEmpty(Password);

        /// <summary>Cancels authentication and closes the dialog.</summary>
        [RelayCommand]
        private void Cancel()
        {
            Accepted = false;
            RequestClose?.Invoke();
        }

        // ── Events ────────────────────────────────────────────────────────────────

        /// <summary>Raised when the dialog should close itself.</summary>
        public event System.Action? RequestClose;
    }
}