/// <summary>
/// Subscribes the specified aggregator to a catchup.
/// </summary>
/// <typeparam name="TProjection">The type of the projection.</typeparam>
/// <typeparam name="TData">The type of the stream's data.</typeparam>
/// <typeparam name="TCursor">The type of the cursor.</typeparam>
/// <param name="catchup">The catchup.</param>
/// <param name="aggregator">The aggregator.</param>
/// <returns>A disposable that, when disposed, unsubscribes the aggregator.</returns>
public static IDisposable Subscribe <TProjection, TData, TCursor>(
this IStreamCatchup <TData, TCursor> catchup,
IStreamAggregator <TProjection, TData> aggregator,
FetchAndSaveProjection <TProjection> manageProjection,
HandleAggregatorError <TProjection> onError = null)
{
return(catchup.SubscribeAggregator(aggregator, manageProjection, onError));
}
/// <summary>
/// Wraps a stream aggregator in a decorator function having the same signature.
/// </summary>
/// <typeparam name="TProjection">The type of the projection.</typeparam>
/// <typeparam name="TData">The type of the data.</typeparam>
/// <param name="aggregator">The aggregator.</param>
/// <param name="initial">The prior state of the projection.</param>
/// <returns>A new aggregator that wraps calls to the specified aggregator.</returns>
public static IStreamAggregator <TProjection, TData> Pipeline <TProjection, TData>(
this IStreamAggregator <TProjection, TData> aggregator,
Func <TProjection, IStreamBatch <TData>, AggregateAsync <TProjection, TData>, Task> initial)
{
return(Create <TProjection, TData>((projection, batch) => initial(projection,
batch,
aggregator.Aggregate)));
}
/// <summary>
/// Subscribes the specified aggregator to a catchup.
/// </summary>
/// <typeparam name="TProjection">The type of the projection.</typeparam>
/// <typeparam name="TData">The type of the stream's data.</typeparam>
/// <typeparam name="TCursor">The type of the cursor.</typeparam>
/// <param name="catchup">The catchup.</param>
/// <param name="aggregator">The aggregator.</param>
/// <param name="projectionStore">The projection store.</param>
/// <returns>A disposable that, when disposed, unsubscribes the aggregator.</returns>
public static IDisposable Subscribe <TProjection, TData, TCursor>(
this IStreamCatchup <TData, TCursor> catchup,
IStreamAggregator <TProjection, TData> aggregator,
IProjectionStore <string, TProjection> projectionStore = null)
{
return(catchup.Subscribe(aggregator,
projectionStore.AsHandler()));
}
/// <summary>
/// Traces calls to the specified aggregator.
/// </summary>
/// <typeparam name="TProjection">The type of the projection.</typeparam>
/// <typeparam name="TData">The type of the data.</typeparam>
/// <param name="aggregator">The aggregator.</param>
/// <param name="write">A delegate that can be used to specify how the arguments should be traced. If this is not provided, output is sent to <see cref="System.Diagnostics.Trace" />.</param>
/// <returns>The original aggregator wrapped in a tracing decorator.</returns>
public static IStreamAggregator <TProjection, TData> Trace <TProjection, TData>(
this IStreamAggregator <TProjection, TData> aggregator,
Action <TProjection, IStreamBatch <TData> > write = null)
{
write = write ?? TraceDefault;
return(aggregator.Pipeline(async(projection, batch, next) =>
{
try
{
write(projection, batch);
return await next(projection, batch);
}
catch (Exception exception)
{
System.Diagnostics.Trace.WriteLine("[Aggregate] Exception: " + exception);
throw;
}
}));
}
/// <summary>
/// Aggregates a single batch of data from a stream using the specified aggregator and projection.
/// </summary>
/// <typeparam name="TProjection">The type of the projection.</typeparam>
/// <typeparam name="TData">The type of the data.</typeparam>
/// <typeparam name="TCursor">The type of the cursor.</typeparam>
/// <param name="stream">The stream.</param>
/// <param name="aggregator">The aggregator.</param>
/// <param name="projection">The projection.</param>
/// <returns>The updated state of the projection.</returns>
/// <remarks>This method can be used to create on-demand projections. It does not do any projection persistence.</remarks>
public static async Task <TProjection> Aggregate <TProjection, TData, TCursor>(
this IStream <TData, TCursor> stream,
IStreamAggregator <TProjection, TData> aggregator,
TProjection projection = null)
where TProjection : class
{
var cursor = (projection as ICursor <TCursor>) ??
stream.NewCursor();
var query = stream.CreateQuery(cursor);
var data = await query.NextBatch();
if (data.Any())
{
projection = await aggregator.Aggregate(projection, data);
}
return(projection);
}
public IDisposable SubscribeAggregator <TProjection>(
IStreamAggregator <TProjection, TData> aggregator,
FetchAndSaveProjection <TProjection> fetchAndSaveProjection,
HandleAggregatorError <TProjection> onError)
{
var added = aggregatorSubscriptions.TryAdd(typeof(TProjection),
new AggregatorSubscription <TProjection, TData>(aggregator,
fetchAndSaveProjection,
onError));
if (!added)
{
throw new InvalidOperationException(string.Format("Aggregator for projection of type {0} is already subscribed.", typeof(TProjection)));
}
return(Disposable.Create(() =>
{
IAggregatorSubscription _;
aggregatorSubscriptions.TryRemove(typeof(TProjection), out _);
}));
}
public AggregatorSubscription(
IStreamAggregator <TProjection, TData> aggregator,
FetchAndSaveProjection <TProjection> fetchAndSaveProjection = null,
HandleAggregatorError <TProjection> onError = null)
{
if (aggregator == null)
{
throw new ArgumentNullException("aggregator");
}
OnError = onError ?? (error => { });
if (onError != null)
{
fetchAndSaveProjection = fetchAndSaveProjection.Catch(onError);
}
FetchAndSaveProjection = fetchAndSaveProjection ??
(async(streamId, aggregate) =>
{
await aggregate(Activator.CreateInstance <TProjection>());
});
Aggregator = aggregator;
}
