Learn-WinUI-3-Second-Edition/Chapter03/Complete/MyMediaCollection/ViewModels/MainViewModel2.txt

using MyMediaCollection.Enums;
using MyMediaCollection.Model;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Windows.Input;

namespace MyMediaCollection.ViewModels
{
    public class MainViewModel : BindableBase
    {
        private string selectedMedium;
        private ObservableCollection<MediaItem> items;
        private ObservableCollection<MediaItem> allItems;
        private IList<string> mediums;
        private MediaItem selectedMediaItem;
        private int additionalItemCount = 1;

        public MainViewModel()
        {
            PopulateData();

            DeleteCommand = new RelayCommand(DeleteItem, CanDeleteItem);

            // No CanExecute param is needed for this command
            // because you can always add or edit items.
            AddEditCommand = new RelayCommand(AddOrEditItem);
        }

        public void PopulateData()
        {
            var cd = new MediaItem
            {
                Id = 1,
                Name = "Classical Favorites",
                MediaType = ItemType.Music,
                MediumInfo = new Medium { Id = 1, MediaType = ItemType.Music, Name = "CD" }
            };

            var book = new MediaItem
            {
                Id = 2,
                Name = "Classic Fairy Tales",
                MediaType = ItemType.Book,
                MediumInfo = new Medium { Id = 2, MediaType = ItemType.Book, Name = "Book" }
            };

            var bluRay = new MediaItem
            {
                Id = 3,
                Name = "The Mummy",
                MediaType = ItemType.Video,
                MediumInfo = new Medium { Id = 3, MediaType = ItemType.Video, Name = "Blu Ray" }
            };

            items = new ObservableCollection<MediaItem>
            {
                cd,
                book,
                bluRay
            };

            allItems = new ObservableCollection<MediaItem>(Items);

            mediums = new List<string>
            {
                "All",
                nameof(ItemType.Book),
                nameof(ItemType.Music),
                nameof(ItemType.Video)
            };

            selectedMedium = Mediums[0];
        }

        public ObservableCollection<MediaItem> Items
        {
            get
            {
                return items;
            }
            set
            {
                SetProperty(ref items, value);
            }
        }

        public IList<string> Mediums
        {
            get
            {
                return mediums;
            }
            set
            {
                SetProperty(ref mediums, value);
            }
        }

        public string SelectedMedium
        {
            get
            {
                return selectedMedium;
            }
            set
            {
                SetProperty(ref selectedMedium, value);

                Items.Clear();

                foreach (var item in allItems)
                {
                    if (string.IsNullOrWhiteSpace(selectedMedium) ||
                        selectedMedium == "All" ||
                        selectedMedium == item.MediaType.ToString())
                    {
                        Items.Add(item);
                    }
                }
            }
        }

        public MediaItem SelectedMediaItem
        {
            get => selectedMediaItem;
            set
            {
                SetProperty(ref selectedMediaItem, value);
                ((RelayCommand)DeleteCommand).RaiseCanExecuteChanged();
            }
        }

        public ICommand AddEditCommand { get; set; }

        public void AddOrEditItem()
        {
            // Note this is temporary until
            // we use a real data source for items.
            const int startingItemCount = 3;

            var newItem = new MediaItem
            {
                Id = startingItemCount + additionalItemCount,
                Location = LocationType.InCollection,
                MediaType = ItemType.Music,
                MediumInfo = new Medium { Id = 1, MediaType = ItemType.Music, Name = "CD" },
                Name = $"CD {additionalItemCount}"
            };

            allItems.Add(newItem);
            Items.Add(newItem);
            additionalItemCount++;
        }

        public ICommand DeleteCommand { get; set; }

        public void DeleteItem()
        {
            allItems.Remove(SelectedMediaItem);
            Items.Remove(SelectedMediaItem);
        }

        private bool CanDeleteItem() => selectedMediaItem != null;
    }
}