/// <summary>
/// Constraint that defines whether a sequence of events is valid.
/// </summary>
/// <param name="es">The events.</param>
/// <returns>A Zen value for if the sequence is valid.</returns>
internal static Zen <bool> IsValidSequence(Zen <IList <Event> > es)
{
var areTimesAscending = PairwiseInvariant(es, (x, y) => x.GetTimeStamp() < y.GetTimeStamp());
var areTimeGapsValid = PairwiseInvariant(es, (x, y) => y.GetTimeStamp() - x.GetTimeStamp() <= maxEventTimeGap);
var arePrioritiesValid = es.All(e => e.GetPriorityClass() <= 1);
var hasPollingEvents = True();
for (int i = 0; i < numPollingIntervals; i++)
{
var et = Event.EventTypeAsInt(EventType.PollingIntervalEvent);
var value = (ushort)(pollingInterval * i);
var hasPollingEvent = es.Any(e => And(e.GetTimeStamp() == value, e.GetEventType() == et));
hasPollingEvents = And(hasPollingEvent, hasPollingEvents);
}
return(And(areTimesAscending, areTimeGapsValid, arePrioritiesValid, hasPollingEvents));
}