/// <summary>
/// Convert an observable collection into an observable change set
/// </summary>
/// <typeparam name="T">The type of the object.</typeparam>
/// <typeparam name="TCollection"></typeparam>
/// <param name="source">The source.</param>
/// <returns></returns>
/// <exception cref="System.ArgumentNullException">source</exception>
public static IObservable <IChangeSet <T> > ToObservableChangeSet <TCollection, T>(this TCollection source)
where TCollection : INotifyCollectionChanged, IEnumerable <T>
{
if (source == null)
{
throw new ArgumentNullException(nameof(source));
}
return(Observable.Create <IChangeSet <T> >(observer =>
{
var data = new ChangeAwareList <T>(source);
if (data.Count > 0)
{
observer.OnNext(data.CaptureChanges());
}
return source.ObserveCollectionChanges()
.Scan(data, (list, args) =>
{
var changes = args.EventArgs;
switch (changes.Action)
{
case NotifyCollectionChangedAction.Add:
{
if (changes.NewItems.Count == 1)
{
list.Insert(changes.NewStartingIndex, (T)changes.NewItems[0]);
}
else
{
list.InsertRange(changes.NewItems.Cast <T>(), changes.NewStartingIndex);
}
break;
}
case NotifyCollectionChangedAction.Remove:
{
if (changes.OldItems.Count == 1)
{
list.RemoveAt(changes.OldStartingIndex);
}
else
{
list.RemoveRange(changes.OldStartingIndex, changes.OldItems.Count);
}
break;
}
case NotifyCollectionChangedAction.Replace:
{
list[changes.NewStartingIndex] = (T)changes.NewItems[0];
break;
}
case NotifyCollectionChangedAction.Reset:
{
list.Clear();
list.AddRange(source);
break;
}
case NotifyCollectionChangedAction.Move:
{
list.Move(changes.OldStartingIndex, changes.NewStartingIndex);
break;
}
}
return list;
})
.Select(list => list.CaptureChanges())
.SubscribeSafe(observer);
}));
}
