public static IObservable <IChangeSet <TObject> > DelayRemove <TObject>(this IObservable <IChangeSet <TObject> > source,
TimeSpan delayPeriod, Action <TObject> onDefer)
{
if (source == null)
{
throw new ArgumentNullException("source");
}
if (onDefer == null)
{
throw new ArgumentNullException("onDefer");
}
return(Observable.Create <IChangeSet <TObject> >(observer =>
{
var removed = new [] { ListChangeReason.Remove, ListChangeReason.Clear, ListChangeReason.RemoveRange };
var localList = new SourceList <TObject>();
var locker = new object();
var shared = source.Synchronize(locker).Publish();
var notRemoved = shared.WhereReasonsAreNot(removed)
.Subscribe(changes =>
{
localList.Edit(innerList =>
{
changes.ForEach(change =>
{
switch (change.Reason)
{
case ListChangeReason.Add:
innerList.Add(change.Item.Current);
break;
case ListChangeReason.AddRange:
change.Range.ForEach(innerList.Add);
break;
case ListChangeReason.Replace:
innerList.Replace(change.Item.Previous.Value, change.Item.Current);
break;
}
});
});
});
//when removed,invoke call back
var removes = shared.WhereReasonsAre(removed)
.ForEachItemChange(change => onDefer(change.Current))
.Delay(delayPeriod)
.Synchronize(locker)
.Subscribe(changes =>
{
//flatten removes into a single enumerable
var toRemove = changes.SelectMany(change =>
{
return change.Type == ChangeType.Item ? new[] { change.Item.Current } : change.Range.Select(t => t);
});
//remove in one hit
localList.RemoveMany(toRemove);
});
var subscriber = localList.Connect().SubscribeSafe(observer);
return new CompositeDisposable(subscriber, removes, notRemoved, shared.Connect());
}));
}