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/*
* Copyright (C) 2000-2024 Vaadin Ltd
*
* This program is available under Vaadin Commercial License and Service Terms.
*
* See for the full
* license.
*/
package com.vaadin.util;
import java.io.Serializable;
import java.time.Duration;
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.time.zone.ZoneOffsetTransition;
import java.time.zone.ZoneRules;
import java.util.ArrayList;
import java.util.List;
import java.util.Locale;
import java.util.TimeZone;
import elemental.json.JsonArray;
import elemental.json.JsonObject;
import elemental.json.impl.JreJsonFactory;
import elemental.json.impl.JsonUtil;
/**
* Utilities related to {@code com.google.gwt.i18n.client.TimeZone}.
*
* @author Vaadin Ltd
* @since 8.2
*/
public final class TimeZoneUtil implements Serializable {
/**
* The default start year (inclusive) from which to calculate the
* daylight-saving time zone transition dates.
*/
private static final int STARTING_YEAR = 1980;
/**
* The default value of the number of future years from the current date for
* which the daylight-saving time zone transition dates are calculated.
*/
private static final int YEARS_FROM_NOW = 20;
private TimeZoneUtil() {
// Static utils only
}
/**
* Returns a JSON string of the specified {@code zoneId} and {@link Locale},
* which is used in
* {@code com.google.gwt.i18n.client.TimeZone.createTimeZone(String)}.
*
* This method calculates the JSON string from the year
* {@value #STARTING_YEAR} until {@value #YEARS_FROM_NOW} years into the
* future from the current date.
*
* @see #toJSON(ZoneId, Locale, int, int)
*
* @param zoneId
* the {@link ZoneId} to get the daylight transitions from
* @param locale
* the locale used to determine the short name of the time zone
*
* @return the encoded string
*/
public static String toJSON(ZoneId zoneId, Locale locale) {
int endYear = LocalDate.now().getYear() + YEARS_FROM_NOW;
return toJSON(zoneId, locale, STARTING_YEAR, endYear);
}
/**
* Returns a JSON string of the specified {@code zoneId} and {@link Locale},
* which is used in
* {@code com.google.gwt.i18n.client.TimeZone.createTimeZone(String)}.
*
* This method calculates the JSON string from {@code startYear} until
* {@code startYear}, both inclusive.
*
* @param zoneId
* the {@link ZoneId} to get the daylight transitions from
* @param locale
* the locale used to determine the short name of the time zone
* @param startYear
* the start year of DST transitions
* @param endYear
* the end year of DST transitions
*
* @return the encoded string
* @since 8.11
*/
public static String toJSON(ZoneId zoneId, Locale locale, int startYear,
int endYear) {
if (zoneId == null || locale == null) {
return null;
}
ZoneRules rules = zoneId.getRules();
TimeZone timeZone = TimeZone.getTimeZone(zoneId);
List transitionsList = new ArrayList<>();
TimeZoneInfo info = new TimeZoneInfo();
if (timeZone.useDaylightTime()) {
for (int year = startYear; year <= endYear; year++) {
ZonedDateTime i = LocalDateTime.of(year, 1, 1, 0, 0)
.atZone(zoneId);
while (true) {
ZoneOffsetTransition t = rules
.nextTransition(i.toInstant());
if (t == null) {
break;
}
i = t.getInstant().atZone(zoneId);
if (i.toLocalDate().getYear() != year) {
break;
}
long epochHours = Duration
.ofSeconds(t.getInstant().getEpochSecond())
.toHours();
long duration = Math.max(t.getDuration().toMinutes(), 0);
transitionsList.add(epochHours);
transitionsList.add(duration);
}
}
}
info.id = zoneId.getId();
info.transitions = transitionsList.stream().mapToLong(l -> l).toArray();
info.stdOffset = (int) Duration.ofMillis(timeZone.getRawOffset())
.toMinutes();
info.names = new String[] {
timeZone.getDisplayName(false, TimeZone.SHORT, locale),
timeZone.getDisplayName(false, TimeZone.LONG, locale),
timeZone.getDisplayName(true, TimeZone.SHORT, locale),
timeZone.getDisplayName(true, TimeZone.LONG, locale) };
return stringify(info);
}
private static String stringify(TimeZoneInfo info) {
JreJsonFactory factory = new JreJsonFactory();
JsonObject object = factory.createObject();
object.put("id", info.id);
object.put("std_offset", info.stdOffset);
object.put("names", getArray(factory, info.names));
object.put("transitions", getArray(factory, info.transitions));
return JsonUtil.stringify(object);
}
private static JsonArray getArray(JreJsonFactory factory, long[] array) {
JsonArray jsonArray = factory.createArray();
for (int i = 0; i < array.length; i++) {
jsonArray.set(i, array[i]);
}
return jsonArray;
}
private static JsonArray getArray(JreJsonFactory factory, String[] array) {
JsonArray jsonArray = factory.createArray();
for (int i = 0; i < array.length; i++) {
jsonArray.set(i, array[i]);
}
return jsonArray;
}
private static class TimeZoneInfo implements Serializable {
String id;
int stdOffset;
String[] names;
long[] transitions;
}
}
