/// <summary>
/// Gets the <see cref="DaylightSavingsRule" /> in effect at a particular <paramref name="moment" />
/// </summary>
/// <param name="standardOffset"></param>
/// <param name="moment"></param>
/// <param name="mostRecentDaylightSavingsRule"></param>
/// <returns></returns>
private bool TryGetMostRecentDaylightSavingsRule(TimeSpan standardOffset, Moment moment,
out DaylightSavingsRule mostRecentDaylightSavingsRule)
{
mostRecentDaylightSavingsRule = null;
DateTime dateTimeOfMoment = moment.ToDateTime();
TimeSpan mostRecentOffsetAdjustment = TimeSpan.Zero;
DaylightSavingsRule mostRecentDaylightSavingsRulePriorToYear;
if (TryGetMostRecentDaylightSavingsRulePriorToYear(dateTimeOfMoment.Year,
out mostRecentDaylightSavingsRulePriorToYear))
{
mostRecentOffsetAdjustment = mostRecentDaylightSavingsRulePriorToYear.AdjustmentToStandardOffset;
mostRecentDaylightSavingsRule = mostRecentDaylightSavingsRulePriorToYear;
}
DaylightSavingsRule mostRecentDaylightSavingsRuleDuringYear;
if (TryGetMostRecentDaylightSavingsRuleDuringYear(standardOffset, mostRecentOffsetAdjustment, moment,
out mostRecentDaylightSavingsRuleDuringYear))
{
mostRecentDaylightSavingsRule = mostRecentDaylightSavingsRuleDuringYear;
}
if (null == mostRecentDaylightSavingsRule)
{
return(false);
}
return(true);
}
private bool TryGetMostRecentDaylightSavingsRuleDuringYear(TimeSpan standardOffset,
TimeSpan mostRecentAdjustmentToStandardOffset, Moment moment,
out DaylightSavingsRule mostRecentDaylightSavingsRule)
{
mostRecentDaylightSavingsRule = null;
DateTime dateTimeOfMoment = moment.ToDateTime();
// get the DaylightSavingsRules from the current year.
IEnumerable <DaylightSavingsRule> currentYearDaylightSavingsRules =
GetAllDaylightSavingsRulesEffectiveInYear(dateTimeOfMoment.Year);
// Guard: current year has no rules
if (!currentYearDaylightSavingsRules.Any())
{
return(false);
}
var momentRulesDictionary = new Dictionary <Moment, DaylightSavingsRule>();
IEnumerable <DaylightSavingsRule> orderedCurrentYearRules =
OrderRulesByDayOfYear(currentYearDaylightSavingsRules,
dateTimeOfMoment.Year);
// initialize offset to offset at end of previous year
TimeSpan effectiveAdjustmentToStandardOffset = mostRecentAdjustmentToStandardOffset;
// determine the Moment each DaylightSavingsRule occurs
foreach (DaylightSavingsRule daylightSavingsRule in orderedCurrentYearRules)
{
Moment momentDaylightSavingsRuleOccurs = daylightSavingsRule.ToMoment(standardOffset,
effectiveAdjustmentToStandardOffset, dateTimeOfMoment.Year);
momentRulesDictionary.Add(momentDaylightSavingsRuleOccurs, daylightSavingsRule);
// update daylight savings adjustment
effectiveAdjustmentToStandardOffset = daylightSavingsRule.AdjustmentToStandardOffset;
}
// locate the most recent rule to have occured this year
int i = 0;
while (momentRulesDictionary.Count > i && momentRulesDictionary.ElementAt(i).Key < moment)
{
mostRecentDaylightSavingsRule = momentRulesDictionary.ElementAt(i).Value;
i++;
}
return(true);
}
