using System;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Windows;
using System.Windows.Controls;
using JD.Core;

namespace JD.WPF.Controls
{
    public static class ListBoxExtensions
    {
        private static readonly Dictionary<ListBox, AutoScrollInfo> m_activeControls = new Dictionary<ListBox, AutoScrollInfo>();

        public static readonly DependencyProperty ScrollOnNewItemProperty = DependencyProperty.RegisterAttached("ScrollOnNewItem", typeof(bool), typeof(ListBoxExtensions), new UIPropertyMetadata(false, OnScrollOnNewItemChanged));

        public static bool GetScrollOnNewItem(DependencyObject obj)
        {
            return (bool)obj.GetValue(ScrollOnNewItemProperty);
        }

        public static void SetScrollOnNewItem(DependencyObject obj, bool value)
        {
            obj.SetValue(ScrollOnNewItemProperty, value);
        }

        private static void OnScrollOnNewItemChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            ListBox listBox = d as ListBox;
            if (listBox == null) return;
            bool oldValue = (bool)e.OldValue, newValue = (bool)e.NewValue;
            if (newValue == oldValue) return;
            if (newValue)
            {
                if (listBox.IsLoaded)
                    OnListBoxLoaded(listBox, new RoutedEventArgs());
                else
                    listBox.Loaded += new RoutedEventHandler(OnListBoxLoaded);
                listBox.Unloaded += new RoutedEventHandler(OnListBoxUnloaded);
            }
            else
            {
                OnListBoxUnloaded(listBox, new RoutedEventArgs());
            }
        }

        private static void OnListBoxLoaded(object sender, RoutedEventArgs e)
        {
            ListBox listBox = (ListBox)sender;
            INotifyCollectionChanged notifyableCollection = listBox.ItemsSource as INotifyCollectionChanged;
            if (notifyableCollection == null)
            {
                CodeHelper.DebugBreak("Trying to activate scroll on added item feature whereas the collection behind does not implement INotifyCollectionChanged. ");
                return;
            }

            listBox.Loaded -= OnListBoxLoaded;
            m_activeControls[listBox] = new AutoScrollInfo(listBox);
        }

        private static void OnListBoxUnloaded(object sender, RoutedEventArgs e)
        {
            ListBox listBox = (ListBox)sender;
            if (m_activeControls.ContainsKey(listBox))
            {
                m_activeControls[listBox].Dispose();
                m_activeControls.Remove(listBox);
            }
            listBox.Unloaded -= OnListBoxUnloaded;
        }

        private class AutoScrollInfo : IDisposable
        {
            public readonly ListBox m_listBox;
            public readonly INotifyCollectionChanged m_notifyableCollection;

            public AutoScrollInfo(ListBox listBox)
            {
                m_listBox = listBox;
                m_notifyableCollection = listBox.ItemsSource as INotifyCollectionChanged;
                if (m_notifyableCollection != null)
                {
                    m_notifyableCollection.CollectionChanged += OnCollectionChanged;
                }
            }

            public void Dispose()
            {
                if (m_notifyableCollection != null)
                {
                    m_notifyableCollection.CollectionChanged -= OnCollectionChanged;
                }
            }

            private void OnCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
            {
                if (e.Action == NotifyCollectionChangedAction.Add)
                {
                    m_listBox.ScrollIntoView(e.NewItems[0]);
                }
            }
        }
    }
}