/// <summary>
/// Parses the date time of year.
/// </summary>
/// <param name="tokens">The tokens to parse.</param>
/// <param name="forRule">True if this is for a Rule line, in which case ON/AT are mandatory;
/// false for a Zone line, in which case it's part of "until" and they're optional</param>
/// <returns>The DateTimeOfYear object.</returns>
/// <remarks>
/// IN ON AT
/// </remarks>
internal ZoneYearOffset ParseDateTimeOfYear(Tokens tokens, bool forRule)
{
var mode = ZoneYearOffset.StartOfYear.Mode;
var timeOfDay = ZoneYearOffset.StartOfYear.TimeOfDay;
int monthOfYear = NextMonth(tokens, "MonthOfYear");
int dayOfMonth = 1;
int dayOfWeek = 0;
bool advanceDayOfWeek = false;
bool addDay = false;
if (tokens.HasNextToken || forRule)
{
var on = NextString(tokens, "On");
if (on.StartsWith("last", StringComparison.Ordinal))
{
dayOfMonth = -1;
dayOfWeek = ParseDayOfWeek(on.Substring(4));
}
else
{
int index = on.IndexOf(">=", StringComparison.Ordinal);
if (index > 0)
{
dayOfMonth = Int32.Parse(on.Substring(index + 2), CultureInfo.InvariantCulture);
dayOfWeek = ParseDayOfWeek(on.Substring(0, index));
advanceDayOfWeek = true;
}
else
{
index = on.IndexOf("<=", StringComparison.Ordinal);
if (index > 0)
{
dayOfMonth = Int32.Parse(on.Substring(index + 2), CultureInfo.InvariantCulture);
dayOfWeek = ParseDayOfWeek(on.Substring(0, index));
}
else
{
try
{
dayOfMonth = Int32.Parse(on, CultureInfo.InvariantCulture);
dayOfWeek = 0;
}
catch (FormatException e)
{
throw new ArgumentException("Unparsable ON token: " + on, e);
}
}
}
}
if (tokens.HasNextToken || forRule)
{
var atTime = NextString(tokens, "AT");
if (!string.IsNullOrEmpty(atTime))
{
if (Char.IsLetter(atTime[atTime.Length - 1]))
{
char zoneCharacter = atTime[atTime.Length - 1];
mode = ZoneYearOffset.NormalizeModeCharacter(zoneCharacter);
atTime = atTime.Substring(0, atTime.Length - 1);
}
if (atTime == "24:00")
{
timeOfDay = LocalTime.Midnight;
addDay = true;
}
else
{
// We happen to parse the time as if it's an offset...
Offset tickOfDay = ParserHelper.ParseOffset(atTime);
timeOfDay = new LocalTime(new LocalInstant(tickOfDay.Ticks));
}
}
}
}
return(new ZoneYearOffset(mode, monthOfYear, dayOfMonth, dayOfWeek, advanceDayOfWeek, timeOfDay, addDay));
}