private ParseResult <LocalDate> DetermineYear(PatternFields usedFields)
{
int yearFromEra = 0;
if (IsFieldUsed(usedFields, PatternFields.YearOfEra))
{
// Odd to have a year-of-era without era, but it's valid...
if (!IsFieldUsed(usedFields, PatternFields.Era))
{
EraIndex = Calendar.Eras.IndexOf(templateValue.Era);
}
// Find the absolute year from the year-of-era and era
if (YearOfEra < Calendar.GetMinYearOfEra(EraIndex) ||
YearOfEra > Calendar.GetMaxYearOfEra(EraIndex))
{
return(ParseResult <LocalDate> .YearOfEraOutOfRange(YearOfEra, EraIndex, Calendar));
}
yearFromEra = Calendar.GetAbsoluteYear(YearOfEra, EraIndex);
}
// Note: we can't have YearTwoDigits without Year, hence there are only 6 options here rather than 8.
switch (usedFields & (PatternFields.Year | PatternFields.YearOfEra | PatternFields.YearTwoDigits))
{
case PatternFields.Year:
// Fine, we'll just use the Year value we've been provided
break;
case PatternFields.Year | PatternFields.YearTwoDigits:
Year = GetAbsoluteYearFromTwoDigits(templateValue.Year, Year);
break;
case PatternFields.YearOfEra:
Year = yearFromEra;
break;
case PatternFields.YearOfEra | PatternFields.Year | PatternFields.YearTwoDigits:
// We've been given a year of era, but only a two digit year. The year of era
// takes precedence, so we just check that the two digits are correct.
// This is a pretty bizarre situation...
if ((Math.Abs(yearFromEra) % 100) != Year)
{
return(ParseResult <LocalDate> .InconsistentValues('y', 'Y'));
}
Year = yearFromEra;
break;
case PatternFields.YearOfEra | PatternFields.Year:
if (Year != yearFromEra)
{
return(ParseResult <LocalDate> .InconsistentValues('y', 'Y'));
}
Year = yearFromEra;
break;
case 0:
Year = templateValue.Year;
break;
// No default: it would be impossible.
}
if (Year > Calendar.MaxYear || Year < Calendar.MinYear)
{
// The field can't be YearOfEra, as we've already validated that earlier.
return(ParseResult <LocalDate> .FieldValueOutOfRange(Year, 'y'));
}
return(null);
}