public void GuessZoneIdByTransitionsUncached(NamedWrapper <TimeZoneInfo> bclZoneWrapper)
{
var bclZone = bclZoneWrapper.Value;
// As of November 21st 2019, the Windows time zone database hasn't caught up
// with the Morocco change in TZDB 2019a. Skip it for now.
if (bclZone.Id == "Morocco Standard Time")
{
return;
}
string?id = TzdbDateTimeZoneSource.GuessZoneIdByTransitionsUncached(bclZone, TzdbDefaultZonesForIdGuessZoneIdByTransitionsUncached);
// Unmappable zones may not be mapped, or may be mapped to something reasonably accurate.
// We don't mind either way.
if (!TzdbDateTimeZoneSource.Default.WindowsMapping.PrimaryMapping.ContainsKey(bclZone.Id))
{
return;
}
Assert.IsNotNull(id, $"Unable to guess time zone for {bclZone.Id}");
var tzdbZone = TzdbDateTimeZoneSource.Default.ForId(id !);
var thisYear = SystemClock.Instance.GetCurrentInstant().InUtc().Year;
LocalDate?lastIncorrectDate = null;
Offset? lastIncorrectBclOffset = null;
Offset? lastIncorrectTzdbOffset = null;
int total = 0;
int correct = 0;
// From the start of this year to the end of next year, we should have an 80% hit rate or better.
// That's stronger than the 70% we limit to in the code, because if it starts going between 70% and 80% we
// should have another look at the algorithm. (And this is dealing with 80% of days, not 80% of transitions,
// so it's not quite equivalent anyway.)
for (var date = new LocalDate(thisYear, 1, 1); date.Year < thisYear + 2; date = date.PlusDays(1))
{
Instant startOfUtcDay = date.AtMidnight().InUtc().ToInstant();
Offset tzdbOffset = tzdbZone.GetUtcOffset(startOfUtcDay);
Offset bclOffset = Offset.FromTimeSpan(bclZone.GetUtcOffset(startOfUtcDay.ToDateTimeOffset()));
if (tzdbOffset == bclOffset)
{
correct++;
}
else
{
// Useful for debugging (by having somewhere to put a breakpoint) as well as for the message.
lastIncorrectDate = date;
lastIncorrectBclOffset = bclOffset;
lastIncorrectTzdbOffset = tzdbOffset;
}
total++;
}
Assert.That(correct * 100.0 / total, Is.GreaterThanOrEqualTo(75.0),
"Last incorrect date for {0} vs {1}: {2} (BCL: {3}; TZDB: {4})",
bclZone.Id,
id,
lastIncorrectDate, lastIncorrectBclOffset, lastIncorrectTzdbOffset);
}
