/// <summary>
///
/// </summary>
/// <typeparam name="TKey"></typeparam>
/// <typeparam name="TOld"></typeparam>
/// <typeparam name="TNew"></typeparam>
/// <typeparam name="TField1"></typeparam>
/// <typeparam name="TField2"></typeparam>
/// <param name="source"></param>
/// <param name="initializer"></param>
/// <param name="fieldSelector1"></param>
/// <param name="fieldInitializer1"></param>
/// <param name="fieldSelector2"></param>
/// <param name="fieldInitializer2"></param>
/// <returns></returns>
public static IStreamable <TKey, TNew> Select <TKey, TOld, TNew, TField1, TField2>(
this IStreamable <TKey, TOld> source,
Expression <Func <TNew> > initializer,
Expression <Func <TNew, TField1> > fieldSelector1,
Expression <Func <TOld, TField1> > fieldInitializer1,
Expression <Func <TNew, TField2> > fieldSelector2,
Expression <Func <TOld, TField2> > fieldInitializer2) where TNew : new()
{
Invariant.IsNotNull(source, nameof(source));
Invariant.IsNotNull(initializer, nameof(initializer));
// Validate that the field selector formulas are actually selector expressions
if (fieldSelector1.Body.NodeType != ExpressionType.MemberAccess)
{
throw new ArgumentException("Unable to determine destination field name from selector expression - expected a member selection expression.", nameof(fieldSelector1));
}
if (fieldSelector2.Body.NodeType != ExpressionType.MemberAccess)
{
throw new ArgumentException("Unable to determine destination field name from selector expression - expected a member selection expression.", nameof(fieldSelector2));
}
if (!(initializer.Body is NewExpression newExpression))
{
throw new ArgumentException("Initializer must return a constructor expression.", nameof(initializer));
}
return(source.Select(CreateAdjustColumnsExpression <TOld, TNew>(
new Dictionary <string, LambdaExpression>
{
{ ((MemberExpression)(fieldSelector1.Body)).Member.Name, fieldInitializer1 },
{ ((MemberExpression)(fieldSelector2.Body)).Member.Name, fieldInitializer2 },
},
newExpression)));
}
/// <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));
}
}
/// <summary>
///
/// </summary>
/// <typeparam name="TKey"></typeparam>
/// <typeparam name="TOld"></typeparam>
/// <typeparam name="TNew"></typeparam>
/// <param name="source"></param>
/// <param name="initializer"></param>
/// <param name="newColumnFormulas"></param>
/// <returns></returns>
public static IStreamable <TKey, TNew> Select <TKey, TOld, TNew>(
this IStreamable <TKey, TOld> source,
Expression <Func <TNew> > initializer,
IDictionary <string, Expression <Func <TOld, object> > > newColumnFormulas = null) where TNew : new()
{
Invariant.IsNotNull(source, nameof(source));
Invariant.IsNotNull(initializer, nameof(initializer));
// Validate that the dictionary parameter references proper fields
if (newColumnFormulas == null)
{
newColumnFormulas = new Dictionary <string, Expression <Func <TOld, object> > >();
}
Type newType = typeof(TNew);
foreach (var pair in newColumnFormulas)
{
if (newType.GetTypeInfo().GetMember(pair.Key).Length == 0)
{
throw new ArgumentException("Dictionary keys must refer to valid members of the destination type", nameof(newColumnFormulas));
}
}
if (!(initializer.Body is NewExpression newExpression))
{
throw new ArgumentException("Initializer must return a constructor expression.", nameof(initializer));
}
return(source.Select(CreateAdjustColumnsExpression <TOld, TNew>(
newColumnFormulas.ToDictionary(o => o.Key, o => (LambdaExpression)o.Value),
newExpression)));
}