using UtopiaCanteenSystem.ViewModels;

namespace UtopiaCanteenSystem.Services;

/// <summary>
/// Holds the current view model and notifies when it changes for binding in MainWindow.
/// </summary>
public class NavigationService : INavigationService
{
    private object? _currentViewModel;
    private DateTime? _dashboardSessionStartUtc;
    private readonly AppSession _session;

    public object? CurrentViewModel
    {
        get => _currentViewModel;
        private set
        {
            if (_currentViewModel == value) return;
            _currentViewModel = value;
            CurrentViewModelChanged?.Invoke(this, EventArgs.Empty);
        }
    }

    public event EventHandler? CurrentViewModelChanged;

    private readonly Func<AdminLoginViewModel> _adminLoginVm;
    private readonly Func<ScannerDashboardViewModel> _scannerVm;
    private readonly Func<MainDashboardViewModel> _dashboardVm;
    private readonly Func<AdminSettingsAuthViewModel> _adminSettingsAuthVm;
    private readonly Func<SettingsViewModel> _settingsVm;
    private readonly Func<MealSchedulesViewModel> _mealSchedulesVm;

    public NavigationService(
        AppSession session,
        Func<AdminLoginViewModel> adminLoginVm,
        Func<ScannerDashboardViewModel> scannerVm,
        Func<MainDashboardViewModel> dashboardVm,
        Func<AdminSettingsAuthViewModel> adminSettingsAuthVm,
        Func<SettingsViewModel> settingsVm,
        Func<MealSchedulesViewModel> mealSchedulesVm)
    {
        _session = session;
        _adminLoginVm = adminLoginVm;
        _scannerVm = scannerVm;
        _dashboardVm = dashboardVm;
        _adminSettingsAuthVm = adminSettingsAuthVm;
        _settingsVm = settingsVm;
        _mealSchedulesVm = mealSchedulesVm;
    }

    public void NavigateToAdminLogin()
    {
        CurrentViewModel = _adminLoginVm();
    }

    public void NavigateToScanner()
    {
        if (!_session.IsAdminAuthenticated)
        {
            NavigateToAdminLogin();
            return;
        }

        CurrentViewModel = _scannerVm();
    }

    public void NavigateToDashboard()
    {
        if (!_session.IsAdminAuthenticated)
        {
            NavigateToAdminLogin();
            return;
        }

        CurrentViewModel = _dashboardVm();
    }

    public void NavigateToSettings()
    {
        if (!_session.IsAdminAuthenticated)
        {
            NavigateToAdminLogin();
            return;
        }

        CurrentViewModel = _settingsVm();
    }

    public void NavigateToAdminSettingsAuth()
    {
        if (!_session.IsAdminAuthenticated)
        {
            NavigateToAdminLogin();
            return;
        }

        CurrentViewModel = _adminSettingsAuthVm();
    }

    public void NavigateToMealSchedules()
    {
        if (!_session.IsAdminAuthenticated)
        {
            NavigateToAdminLogin();
            return;
        }
        CurrentViewModel = _mealSchedulesVm();
    }

    public void StartDashboardSession()
    {
        _dashboardSessionStartUtc = DateTime.UtcNow;
    }

    public bool IsDashboardSessionExpired(TimeSpan timeout)
    {
        if (!_dashboardSessionStartUtc.HasValue)
            return true;

        return DateTime.UtcNow - _dashboardSessionStartUtc.Value >= timeout;
    }

    public TimeSpan GetDashboardSessionElapsed()
    {
        if (!_dashboardSessionStartUtc.HasValue)
            return TimeSpan.MaxValue;

        return DateTime.UtcNow - _dashboardSessionStartUtc.Value;
    }

    public void NavigateBackFromSettings(TimeSpan timeout)
    {
        // Single-screen mode: always return to the scanner/dashboard screen.
        NavigateToScanner();
    }
}