ItemGroupCollection.cs

using System.Collections.ObjectModel;
using NeuroAccessMaui.Services;
 
namespace NeuroAccessMaui.UI.Pages
{
    public interface IUniqueItem
    {
        public string UniqueName { get; }
 
        public string LocalisedName => this.UniqueName;
    }
 
    public class ObservableItemGroup<T>(string Name, IEnumerable<T> Items) : ObservableCollection<T>(Items), IUniqueItem
        where T : IUniqueItem
    {
        public string UniqueName { get; } = Name;
 
        public string LocalisedName => ServiceRef.Localizer[this.UniqueName] ?? this.UniqueName;
 
        public override string ToString()
        {
            return this.UniqueName;
        }
 
        public static void UpdateGroupsItems(ObservableItemGroup<IUniqueItem> OldCollection, ObservableItemGroup<IUniqueItem> NewCollection)
        {
            // First, remove items which are no longer in the new collection
 
            Dictionary<string, IUniqueItem> ToRemove = [];
 
            foreach (IUniqueItem Item in OldCollection)
                ToRemove[Item.UniqueName] = Item;
 
            foreach (IUniqueItem Item in NewCollection)
                ToRemove.Remove(Item.UniqueName);
 
            foreach (IUniqueItem Item in ToRemove.Values)
                OldCollection.Remove(Item);
 
            // Then recursivelly update every item.
            // An old item might move or a new item might be inserted in the middle or appended to the end.
            for (int i = 0; i < NewCollection.Count; i++)
            {
                IUniqueItem NewItem = NewCollection[i];
 
                if (i >= OldCollection.Count)
                {
                    // appended to the end
                    OldCollection.Add(NewItem);
                }
                else
                {
                    IUniqueItem OldItem = OldCollection[i];
 
                    if (OldItem.UniqueName.Equals(NewItem.UniqueName, StringComparison.Ordinal))
                    {
                        // The item is in its right place.
                        // If it's a collection, do the update recursivelly
 
                        if (OldItem is ObservableItemGroup<IUniqueItem> OldItems && NewItem is ObservableItemGroup<IUniqueItem> NewItems)
                            UpdateGroupsItems(OldItems, NewItems);
                    }
                    else
                    {
                        // We removed the missing items, so this item is moved or has to be inserted
                        int OldIndex = -1;
 
                        for (int j = i + 1; j < OldCollection.Count; j++)
                        {
                            if (OldCollection[j].UniqueName.Equals(NewItem.UniqueName, StringComparison.Ordinal))
                            {
                                OldIndex = j;
                                break;
                            }
                        }
 
                        if (OldIndex == -1)
                        {
                            // The item isn't found in the old collection
                            OldCollection.Insert(i, NewItem);
                        }
                        else
                        {
                            // Move the item to it's new position
                            OldCollection.Move(OldIndex, i);
 
                            // If it's a collection, do the update recursivelly
                            if (OldItem is ObservableItemGroup<IUniqueItem> OldItems && NewItem is ObservableItemGroup<IUniqueItem> NewItems)
                                UpdateGroupsItems(OldItems, NewItems);
                        }
                    }
                }
            }
        }
    }
}