private void Update(Chunk <NotifyCollectionChangedEventArgs> changes)
{
if (changes is null || changes.Count == 0)
{
return;
}
using (changes.ClearTransaction())
{
if (changes.Count > 1)
{
this.Refresh(changes);
return;
}
var e = changes[0];
switch (e.Action)
{
case NotifyCollectionChangedAction.Add:
{
if (!e.TryGetSingleNewItem <TSource>(out var newSource))
{
goto case NotifyCollectionChangedAction.Reset;
}
var index = e.NewStartingIndex;
var value = this.GetOrCreate(newSource, index);
this.Tracker.Insert(index, value);
var args = this.UpdateRange(index + 1, this.Count - 1);
args.Add(Diff.CreateAddEventArgs(value, index));
this.Notify(args);
break;
}
case NotifyCollectionChangedAction.Remove:
{
if (!e.TryGetSingleOldItem <TSource>(out var oldSource))
{
goto case NotifyCollectionChangedAction.Reset;
}
var index = e.OldStartingIndex;
var value = this.Tracker[index];
this.Tracker.RemoveAt(index);
var argses = this.UpdateRange(index, this.Count - 1);
argses.Add(Diff.CreateRemoveEventArgs(value, index));
this.Notify(argses);
this.factory.Remove(oldSource, value);
break;
}
case NotifyCollectionChangedAction.Replace:
{
if (!e.TryGetSingleNewItem <TSource>(out var newSource) ||
!e.TryGetSingleOldItem <TSource>(out var oldSource))
{
goto case NotifyCollectionChangedAction.Reset;
}
var index = e.NewStartingIndex;
var value = this.GetOrCreate(newSource, index);
var oldValue = this.Tracker[e.OldStartingIndex];
this.Tracker[index] = value;
var arg = Diff.CreateReplaceEventArgs(value, oldValue, index);
this.Notify(arg);
this.factory.Remove(oldSource, oldValue);
break;
}
case NotifyCollectionChangedAction.Move:
{
var value = this.Tracker[e.OldStartingIndex];
this.Tracker.RemoveAt(e.OldStartingIndex);
this.Tracker.Insert(e.NewStartingIndex, value);
var args = this.UpdateRange(Math.Min(e.OldStartingIndex, e.NewStartingIndex), Math.Max(e.OldStartingIndex, e.NewStartingIndex));
args.Add(Diff.CreateMoveEventArgs(value, e.NewStartingIndex, e.OldStartingIndex));
this.Notify(args);
break;
}
case NotifyCollectionChangedAction.Reset:
using (this.factory.RefreshTransaction())
{
this.Refresh(changes);
}
break;
default:
throw new ArgumentOutOfRangeException(nameof(changes));
}
}
}