PocketBook/Sources/BookApp/ViewModel/ViewModelNavigation.cs

using ToolKit;
using System.Windows.Input;
using System.Diagnostics;
using Model;

namespace BookApp.ViewModel
{
    public class ViewModelNavigation : BaseViewModel
    {
        private ViewModelMenuItem _selectedItem;
        public ViewModelMenuItem SelectedItem
        {
            get { return _selectedItem; }
            set { SetProperty(ref _selectedItem, value); }
        }

        private Book _selectedBook;
        public Book SelectedBook
        {
            get { return _selectedBook; }
            set { SetProperty(ref _selectedBook, value); }
        }
        public INavigation Navigation { get; set; }

        public ICommand MenuItemsFiltre { get; private set; }
        public ICommand ItemSelectedCommandMain { get; private set; }
        public ICommand BookSelected { get; private set; }

        public ICommand BackButtonCommand { get; private set; }

        public ViewModelNavigation()
        {
            MenuItemsFiltre = new Command(async () => await OnItemSelected(SelectedItem));
            ItemSelectedCommandMain = new Command(async () => await OnItemSelected(SelectedItem));

            BackButtonCommand = new Command(async () => await BackButton(this, EventArgs.Empty));

            BookSelected = new Command(async () => await OnBookSelected(SelectedBook));
        }

        private async Task OnItemSelected(ViewModelMenuItem selectedItem)
        {
            SelectedItem = selectedItem;

            if (string.IsNullOrEmpty(SelectedItem?.Route))
            {
                return;
            }
            try
            {
                await Shell.Current.GoToAsync(selectedItem.Route);
            }
            catch (Exception ex)
            {
                Debug.WriteLine($"Navigation failed: {ex.Message}");
            }
        }

        private async Task OnBookSelected(Book SelectedBook)
        {
            if (SelectedBook == null)
            {
                return;
            }
            try
            {
                await Shell.Current.GoToAsync("DetailBookPage");
            }
            catch (Exception ex)
            {
                Debug.WriteLine($"Navigation failed: {ex.Message}");
            }
        }

        async Task BackButton(object sender, EventArgs args)
        {
            if (Shell.Current.Navigation.NavigationStack.Count > 1)
            {
                await Shell.Current.Navigation.PopAsync();
            }
        }
    }
}