/// <summary>
/// This is used to expand one or more months by day of the week. It is used by the monthly and yearly
/// frequencies.
/// </summary>
/// <param name="r">A reference to the recurrence</param>
/// <param name="dates">A reference to the collection of current instances that have been generated</param>
/// <returns>The number of instances in the collection. If zero, subsequent rules don't have to be
/// checked as there's nothing else to do.</returns>
/// <remarks>If an expanded date is invalid, it will be discarded</remarks>
public static int ByDayInMonths(Recurrence r, RecurDateTimeCollection dates)
{
RecurDateTime rdt, rdtNew;
DayOfWeek dow;
int expIdx, instance, count = dates.Count;
DayInstanceCollection byDay = r.ByDay;
// Don't bother if either collection is empty
if (count != 0 && byDay.Count != 0)
{
for (int idx = 0; idx < count; idx++)
{
rdt = dates[0];
dates.RemoveAt(0);
// Expand the date/time by adding a new entry for each week day instance specified
for (expIdx = 0; expIdx < byDay.Count; expIdx++)
{
instance = byDay[expIdx].Instance;
dow = byDay[expIdx].DayOfWeek;
if (instance == 0)
{
// Expand to every specified day of the week
// in the month.
rdtNew = new RecurDateTime(rdt)
{
Day = 1
};
rdtNew.AddDays(((int)dow + 7 - (int)rdtNew.DayOfWeek) % 7);
while (rdtNew.IsValidDate() && rdtNew.Year == rdt.Year && rdtNew.Month == rdt.Month)
{
dates.Add(new RecurDateTime(rdtNew));
rdtNew.AddDays(7);
}
continue;
}
if (instance > 0)
{
// Add the nth instance of the day of the week
rdtNew = new RecurDateTime(rdt)
{
Day = 1
};
rdtNew.AddDays((((int)dow + 7 - (int)rdtNew.DayOfWeek) % 7) + ((instance - 1) * 7));
}
else
{
// Add the nth instance of the day of the week
// from the end of the month.
rdtNew = new RecurDateTime(rdt)
{
Day = DateTime.DaysInMonth(rdt.Year, rdt.Month + 1)
};
rdtNew.AddDays(0 - (((int)rdtNew.DayOfWeek + 7 - (int)dow) % 7) + ((instance + 1) * 7));
}
// If not in the year, discard it
if (rdtNew.Year != rdt.Year || rdtNew.Month != rdt.Month)
{
continue;
}
dates.Add(new RecurDateTime(rdtNew));
}
}
}
return(dates.Count);
}
