#region License

// Copyright (C) 2020 Reetus
// 
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// 
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
// 
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.

#endregion

using System.Collections.Specialized;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Interactivity;

namespace ClassicAssist.UI.Misc
{
    public class ItemsControlAutoScrollBehaviour : Behavior<ItemsControl>
    {
        public static readonly DependencyProperty ScrollViewerProperty = DependencyProperty.Register( "ScrollViewer",
            typeof( ScrollViewer ), typeof( ItemsControlAutoScrollBehaviour ),
            new PropertyMetadata( default( ScrollViewer ) ) );

        public ScrollViewer ScrollViewer
        {
            get => (ScrollViewer) GetValue( ScrollViewerProperty );
            set => SetValue( ScrollViewerProperty, value );
        }

        protected override void OnAttached()
        {
            base.OnAttached();

            ( (INotifyCollectionChanged) AssociatedObject.Items ).CollectionChanged += OnCollectionChanged;
        }

        private void OnCollectionChanged( object sender, NotifyCollectionChangedEventArgs e )
        {
            ScrollViewer?.ScrollToEnd();
        }

        protected override void OnDetaching()
        {
            base.OnDetaching();

            ( (INotifyCollectionChanged) AssociatedObject.Items ).CollectionChanged -= OnCollectionChanged;
        }
    }
}