Handle leap seconds with DateTimeFormatter

DateTimeSerdes.java

package foo;

import java.time.Instant;
import java.time.OffsetDateTime;
import java.time.format.DateTimeFormatter;
import java.time.temporal.TemporalAccessor;
import java.time.temporal.TemporalQuery;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

class DateTimeSerdes {

  private static final Logger logger = LoggerFactory.getLogger(DateTimeSerdes.class);

  OffsetDateTime toOffsetDateTime(String raw) {
    return toDateObject(raw, OffsetDateTime::from);
  }

  Instant toInstant(String raw) {
    return toDateObject(raw, Instant::from);
  }

  private <T> T toDateObject(String raw, TemporalQuery<T> from) {
    // hack to detect a leap
    if (raw.contains(":59:60")) { 
      // ISO_INSTANT doesn't crash on leap seconds 
      TemporalAccessor parse = DateTimeFormatter.ISO_INSTANT.parse(raw);
      if (parse.query(DateTimeFormatter.parsedLeapSecond())) {
        logger.warn("saw leap second, shifting the date back 1s, {}", raw);
        return DateTimeFormatter.ISO_OFFSET_DATE_TIME.parse(raw.replace(":59:60", ":59:59"),
            from);
      }
    }
    return DateTimeFormatter.ISO_OFFSET_DATE_TIME.parse(raw, from);
  }
}