using System.Collections;
using System.Collections.Generic;
using System.Windows.Data;

namespace System.Windows.Forms
{
    public class ListViewGroupCollection : CollectionBase, IEnumerable
    {
        private ListView owner { get; }
        private Dictionary<string, ListViewGroup> groups { get; }
        private CollectionView CollectionView => (CollectionView)CollectionViewSource.GetDefaultView(owner.Items);

        public ListViewGroup this[string key] => groups[key];

        public new int Count => groups.Count;

        private void AddGroupView()
        {
            var view = CollectionView;
            if (view.GroupDescriptions.Count == 0)
                view.GroupDescriptions.Add(new PropertyGroupDescription("Group"));
        }

        private void ClearGroupView()
        {
            if (groups.Count == 0)
                CollectionView.GroupDescriptions.Clear();
        }

        public new IEnumerator GetEnumerator() => groups.Values.GetEnumerator();

        public void Add(string key, string header)
        {
            AddGroupView();
            groups[key] = new ListViewGroup() { Header = header };
        }

        public new void RemoveAt(int index) { }

        public void Remove(string key)
        {
            groups.Remove(key);
            ClearGroupView();
        }

        public new void Clear()
        {
            groups.Clear();
            ClearGroupView();
        }

        internal ListViewGroupCollection(ListView owner)
        {
            this.owner = owner;
            groups = new();
        }
    }
}