/// <summary>
/// Adjusts the lifetime of incoming events to implement, when used in combination with aggregates, hopping windows. In this implementation each incoming
/// event results in a single outgoing event, which means that subsequent aggregates only produce output when the input changes. For instance, if a single
/// point event is received and the windowSize, period, and offset are 100, 2, and 0 respectively, a single aggregate output is produced with a lifetime of
/// 100 ticks.
/// </summary>
/// <typeparam name="TKey">Type of (mapping) key in the stream</typeparam>
/// <typeparam name="TPayload">Type of payload in the stream</typeparam>
/// <param name="source">Input stream</param>
/// <param name="windowSize">Window size</param>
/// <param name="period">Period (or hop size)</param>
/// <param name="offset">Offset from the start of time</param>
/// <returns>Result (output) stream</returns>
public static IStreamable <TKey, TPayload> HoppingWindowLifetime <TKey, TPayload>(
this IStreamable <TKey, TPayload> source,
long windowSize,
long period,
long offset = 0)
{
if (period > windowSize)
{
return(source
.Select((vs, e) => new { StartTime = vs, Payload = e })
.Where(x => (((x.StartTime + period - offset) % period) > (period - windowSize)) || ((x.StartTime + period - offset) % period == 0))
.Select(x => x.Payload)
.AlterEventLifetime(vs => AdjustStartTime(vs, offset, period), windowSize)
.SetProperty().IsConstantHop(true, period, offset));
}
if (windowSize % period == 0)
{
return(source.AlterEventLifetime(vs => AdjustStartTime(vs, offset, period), windowSize)
.SetProperty().IsConstantHop(true, period, offset));
}
else
{
return(source.AlterEventLifetime(
vs => AdjustStartTime(vs, offset, period),
vs => AdjustStartTime(vs + windowSize, offset, period) - AdjustStartTime(vs, offset, period))
.SetProperty().IsConstantHop(true, period, offset));
}
}