/// <summary>
/// This method enqueues an action to be run at a later time, according
/// to the scheduling policies (i.e. via priority and key).
/// </summary>
/// <typeparam name="T">The type of item for the observable.</typeparam>
/// <typeparam name="TDontCare">Used to allow any observable type.</typeparam>
/// <param name="priority">The priority of operation. Higher priorities run before lower ones.</param>
/// <param name="key">A key to apply to the operation. Items with the same key will be run in order.</param>
/// <param name="cancel">A observable which if signalled, the operation will be cancelled.</param>
/// <param name="asyncCalculationFunc">The async method to execute when scheduled.</param>
/// <returns>The result of the async calculation.</returns>
public IObservable <T> EnqueueObservableOperation <T, TDontCare>(int priority, string key, IObservable <TDontCare> cancel, Func <IObservable <T> > asyncCalculationFunc)
{
var id = Interlocked.Increment(ref sequenceNumber);
var cancelReplay = new ReplaySubject <TDontCare>();
var item = new KeyedOperation <T>
{
Key = key ?? DefaultKey,
Id = id,
Priority = priority,
CancelSignal = cancelReplay.Select(_ => Unit.Default),
Func = asyncCalculationFunc,
};
cancel
.Do(_ =>
{
Debug.WriteLine("Cancelling {0}", id);
item.CancelledEarly = true;
})
.Multicast(cancelReplay).Connect();
lock (_queuedOps)
{
Debug.WriteLine("Queued item {0}, priority {1}", item.Id, item.Priority);
_queuedOps.OnNext(item);
}
return(item.Result);
}
private static IObservable <KeyedOperation> ProcessOperation(KeyedOperation operation)
{
Debug.WriteLine("Processing item {0}, priority {1}", operation.Id, operation.Priority);
return(Observable.Defer(operation.EvaluateFunc)
.Select(_ => operation)
.Catch(Observable.Return(operation)));
}