protected DateTime?CalculateEnd(DateTime start, TimeSpan offset,
SeekDirection seekDirection, SeekBoundaryMode seekBoundaryMode, out TimeSpan?remaining)
{
if (offset < TimeSpan.Zero)
{
throw new InvalidOperationException("time span must be positive");
}
remaining = offset;
// search periods
TimePeriodCollection searchPeriods = new TimePeriodCollection(_includePeriods);
// no search periods specified: search anytime
if (searchPeriods.Count == 0)
{
searchPeriods.Add(TimeRange.Anytime);
}
// available periods
ITimePeriodCollection availablePeriods = new TimePeriodCollection();
// no exclude periods specified: use all search periods
if (_excludePeriods.Count == 0)
{
availablePeriods.AddAll(searchPeriods);
}
else // remove exclude periods
{
TimeGapCalculator <TimeRange> gapCalculator = new TimeGapCalculator <TimeRange>();
foreach (ITimePeriod searchPeriod in searchPeriods)
{
// no overlaps: use the entire search range
if (!_excludePeriods.HasOverlapPeriods(searchPeriod))
{
availablePeriods.Add(searchPeriod);
}
else // add gaps of search period using the exclude periods
{
availablePeriods.AddAll(gapCalculator.GetGaps(_excludePeriods, searchPeriod));
}
}
}
// no periods available
if (availablePeriods.Count == 0)
{
return(null);
}
// combine the available periods, ensure no overlapping
// used for FindNextPeriod/FindPreviousPeriod
if (availablePeriods.Count > 1)
{
TimePeriodCombiner <TimeRange> periodCombiner = new TimePeriodCombiner <TimeRange>();
availablePeriods = periodCombiner.CombinePeriods(availablePeriods);
}
// find the starting search period
ITimePeriod startPeriod = null;
DateTime seekMoment = start;
switch (seekDirection)
{
case SeekDirection.Forward:
startPeriod = FindNextPeriod(start, availablePeriods, out seekMoment);
break;
case SeekDirection.Backward:
startPeriod = FindPreviousPeriod(start, availablePeriods, out seekMoment);
break;
}
// no starting period available
if (startPeriod == null)
{
return(null);
}
// no offset: use the search staring position
// maybe moved to the next available search period
if (offset == TimeSpan.Zero)
{
return(seekMoment);
}
// setup destination search
switch (seekDirection)
{
case SeekDirection.Forward:
for (int i = availablePeriods.IndexOf(startPeriod); i < availablePeriods.Count; i++)
{
ITimePeriod gap = availablePeriods[i];
TimeSpan gapRemining = gap.End - seekMoment;
bool isTargetPeriod = false;
switch (seekBoundaryMode)
{
case SeekBoundaryMode.Fill:
isTargetPeriod = gapRemining >= remaining;
break;
case SeekBoundaryMode.Next:
isTargetPeriod = gapRemining > remaining;
break;
}
if (isTargetPeriod)
{
DateTime end = seekMoment + remaining.Value;
remaining = null;
return(end);
}
remaining = remaining - gapRemining;
if (i == availablePeriods.Count - 1)
{
return(null);
}
seekMoment = availablePeriods[i + 1].Start; // next period
}
break;
case SeekDirection.Backward:
for (int i = availablePeriods.IndexOf(startPeriod); i >= 0; i--)
{
ITimePeriod gap = availablePeriods[i];
TimeSpan gapRemining = seekMoment - gap.Start;
bool isTargetPeriod = false;
switch (seekBoundaryMode)
{
case SeekBoundaryMode.Fill:
isTargetPeriod = gapRemining >= remaining;
break;
case SeekBoundaryMode.Next:
isTargetPeriod = gapRemining > remaining;
break;
}
if (isTargetPeriod)
{
DateTime end = seekMoment - remaining.Value;
remaining = null;
return(end);
}
remaining = remaining - gapRemining;
if (i == 0)
{
return(null);
}
seekMoment = availablePeriods[i - 1].End; // previous period
}
break;
}
return(null);
}