packages/timezone/src/MomentZoneRules.js
/*
* @copyright (c) 2016-present, Philipp Thürwächter, Pattrick Hüper
* @copyright (c) 2007-present, Stephen Colebourne & Michael Nascimento Santos
* @license BSD-3-Clause (see LICENSE in the root directory of this source tree)
*/
import {
LocalDateTime, Instant, ZoneOffset, ZoneOffsetTransition, ZoneRules
} from '@js-joda/core';
export class MomentZoneRules extends ZoneRules{
constructor(tzdbInfo){
super();
this._tzdbInfo = tzdbInfo;
this._ldtUntils = new LDTUntils(this._tzdbInfo.untils, this._tzdbInfo.offsets);
}
/**
* Checks of the zone rules are fixed, such that the offset never varies.
*
* @return {boolean} true if the time-zone is fixed and the offset never changes
*/
isFixedOffset(){
return this._tzdbInfo.offsets.length === 1;
}
//-----------------------------------------------------------------------
/**
* Gets the offset applicable at the specified instant in these rules.
* <p>
* The mapping from an instant to an offset is simple, there is only
* one valid offset for each instant.
* This method returns that offset.
*
* @param {Instant} instant - the instant to find the offset for, not null, but null
* may be ignored if the rules have a single offset for all instants
* @return {ZoneOffset} the offset, not null
*/
offsetOfInstant(instant){
const epochMilli = instant.toEpochMilli();
return this.offsetOfEpochMilli(epochMilli);
}
/**
* Gets the offset applicable at the specified epochMilli in these rules.
*
* The method is for javascript performance optimisation.
*
* @param {number} epochMilli - the epoch millisecond to find the offset for, not null, but null
* may be ignored if the rules have a single offset for all instants
* @return {ZoneOffset} the offset, not null
*/
offsetOfEpochMilli(epochMilli){
const index = binarySearch(this._tzdbInfo.untils, epochMilli);
return ZoneOffset.ofTotalSeconds(this._offsetByIndexInSeconds(index));
}
/**
* Gets a suitable offset for the specified local date-time in these rules.
* <p>
* The mapping from a local date-time to an offset is not straightforward.
* There are three cases:
* <p><ul>
* <li>Normal, with one valid offset. For the vast majority of the year, the normal
* case applies, where there is a single valid offset for the local date-time.</li>
* <li>Gap, with zero valid offsets. This is when clocks jump forward typically
* due to the spring daylight savings change from "winter" to "summer".
* In a gap there are local date-time values with no valid offset.</li>
* <li>Overlap, with two valid offsets. This is when clocks are set back typically
* due to the autumn daylight savings change from "summer" to "winter".
* In an overlap there are local date-time values with two valid offsets.</li>
* </ul><p>
* Thus, for any given local date-time there can be zero, one or two valid offsets.
* This method returns the single offset in the Normal case, and in the Gap or Overlap
* case it returns the offset before the transition.
* <p>
* Since, in the case of Gap and Overlap, the offset returned is a "best" value, rather
* than the "correct" value, it should be treated with care. Applications that care
* about the correct offset should use a combination of this method,
* {@link #getValidOffsets(LocalDateTime)} and {@link #getTransition(LocalDateTime)}.
*
* @param {LocalDateTime} localDateTime - the local date-time to query, not null, but null
* may be ignored if the rules have a single offset for all instants
* @return {ZoneOffset} the best available offset for the local date-time, not null
*/
offsetOfLocalDateTime(localDateTime){
const info = this._offsetInfo(localDateTime);
if (info instanceof ZoneOffsetTransition) {
return info.offsetBefore();
}
return info;
}
_offsetInfo(localDateTime) {
const index = ldtBinarySearch(this._ldtUntils, localDateTime);
const offsetIndex = index >> 1;
if (index % 2 === 1){
const ldtBefore = this._ldtUntils.get(Math.max(index-1, 0));
const ldtAfter = this._ldtUntils.get(Math.min(index, this._ldtUntils.size-1));
const offsetBefore = ZoneOffset.ofTotalSeconds(this._offsetByIndexInSeconds(offsetIndex));
const offsetAfter = ZoneOffset.ofTotalSeconds(this._offsetByIndexInSeconds(Math.min(offsetIndex+1, this._tzdbInfo.offsets.length-1)));
// console.log(offsetBefore.toString(), offsetAfter.toString());
if (offsetBefore.compareTo(offsetAfter) > 0) {
// gap
// console.log('gap', ldtBefore.toString(), localDateTime.toString(), ldtAfter.toString());
return ZoneOffsetTransition.of(ldtBefore, offsetBefore, offsetAfter);
} else {
// overlap
// console.log('overlap', ldtBefore.toString(), localDateTime.toString(), ldtAfter.toString());
return ZoneOffsetTransition.of(ldtAfter, offsetBefore, offsetAfter);
}
}
return ZoneOffset.ofTotalSeconds(this._offsetByIndexInSeconds(offsetIndex));
}
_offsetByIndexInSeconds(index){
return -offsetInSeconds(this._tzdbInfo.offsets[index]);
}
/**
* Gets the offset applicable at the specified local date-time in these rules.
* <p>
* The mapping from a local date-time to an offset is not straightforward.
* There are three cases:
* <p><ul>
* <li>Normal, with one valid offset. For the vast majority of the year, the normal
* case applies, where there is a single valid offset for the local date-time.</li>
* <li>Gap, with zero valid offsets. This is when clocks jump forward typically
* due to the spring daylight savings change from "winter" to "summer".
* In a gap there are local date-time values with no valid offset.</li>
* <li>Overlap, with two valid offsets. This is when clocks are set back typically
* due to the autumn daylight savings change from "summer" to "winter".
* In an overlap there are local date-time values with two valid offsets.</li>
* </ul><p>
* Thus, for any given local date-time there can be zero, one or two valid offsets.
* This method returns that list of valid offsets, which is a list of size 0, 1 or 2.
* In the case where there are two offsets, the earlier offset is returned at index 0
* and the later offset at index 1.
* <p>
* There are various ways to handle the conversion from a {@code LocalDateTime}.
* One technique, using this method, would be:
* <pre>
* List<ZoneOffset> validOffsets = rules.getOffset(localDT);
* if (validOffsets.size() == 1) {
* // Normal case: only one valid offset
* zoneOffset = validOffsets.get(0);
* } else {
* // Gap or Overlap: determine what to do from transition (which will be non-null)
* ZoneOffsetTransition trans = rules.getTransition(localDT);
* }
* </pre>
* <p>
* In theory, it is possible for there to be more than two valid offsets.
* This would happen if clocks to be put back more than once in quick succession.
* This has never happened in the history of time-zones and thus has no special handling.
* However, if it were to happen, then the list would return more than 2 entries.
*
* @param {LocalDateTime} localDateTime - the local date-time to query for valid offsets, not null
* may be ignored if the rules have a single offset for all instants
* @return {ZoneOffsetTransition | ZoneOffset[]} the list of valid offsets, may be immutable, not null
*/
validOffsets(localDateTime){
const info = this._offsetInfo(localDateTime);
if (info instanceof ZoneOffsetTransition) {
return info.validOffsets();
}
return [info];
}
/**
* Gets the offset transition applicable at the specified local date-time in these rules.
* <p>
* The mapping from a local date-time to an offset is not straightforward.
* There are three cases:
* <p><ul>
* <li>Normal, with one valid offset. For the vast majority of the year, the normal
* case applies, where there is a single valid offset for the local date-time.</li>
* <li>Gap, with zero valid offsets. This is when clocks jump forward typically
* due to the spring daylight savings change from "winter" to "summer".
* In a gap there are local date-time values with no valid offset.</li>
* <li>Overlap, with two valid offsets. This is when clocks are set back typically
* due to the autumn daylight savings change from "summer" to "winter".
* In an overlap there are local date-time values with two valid offsets.</li>
* </ul><p>
* A transition is used to model the cases of a Gap or Overlap.
* The Normal case will return null.
* <p>
* There are various ways to handle the conversion from a {@code LocalDateTime}.
* One technique, using this method, would be:
* <pre>
* ZoneOffsetTransition trans = rules.getTransition(localDT);
* if (trans != null) {
* // Gap or Overlap: determine what to do from transition
* } else {
* // Normal case: only one valid offset
* zoneOffset = rule.getOffset(localDT);
* }
* </pre>
*
* @param {LocalDateTime} localDateTime the local date-time to query for offset transition, not null, but null
* may be ignored if the rules have a single offset for all instants
* @return {ZoneOffsetTransition} the offset transition, null if the local date-time is not in transition
*/
// eslint-disable-next-line no-unused-vars
transition(localDateTime){
const info = this._offsetInfo(localDateTime);
if (info instanceof ZoneOffsetTransition) {
return info;
}
return null;
}
//-----------------------------------------------------------------------
/**
* Gets the standard offset for the specified instant in this zone.
* <p>
* This provides access to historic information on how the standard offset
* has changed over time.
* The standard offset is the offset before any daylight saving time is applied.
* This is typically the offset applicable during winter.
*
* @param {Instant} instant - the instant to find the offset information for, not null, but null
* may be ignored if the rules have a single offset for all instants
* @return {ZoneOffset} the standard offset, not null
*/
// eslint-disable-next-line no-unused-vars
standardOffset(instant){
notSupported('ZoneRules.standardOffset');
}
/**
* Gets the amount of daylight savings in use for the specified instant in this zone.
* <p>
* This provides access to historic information on how the amount of daylight
* savings has changed over time.
* This is the difference between the standard offset and the actual offset.
* Typically the amount is zero during winter and one hour during summer.
* Time-zones are second-based, so the nanosecond part of the duration will be zero.
*
* @param {Instant} instant - the instant to find the daylight savings for, not null, but null
* may be ignored if the rules have a single offset for all instants
* @return {Duration} the difference between the standard and actual offset, not null
*/
// eslint-disable-next-line no-unused-vars
daylightSavings(instant){
notSupported('ZoneRules.daylightSavings');
}
/**
* Checks if the specified instant is in daylight savings.
* <p>
* This checks if the standard and actual offsets are the same at the specified instant.
*
* @param {Instant} instant - the instant to find the offset information for, not null, but null
* may be ignored if the rules have a single offset for all instants
* @return {boolean} the standard offset, not null
*/
// eslint-disable-next-line no-unused-vars
isDaylightSavings(instant) {
notSupported('ZoneRules.isDaylightSavings');
}
/**
* Checks if the offset date-time is valid for these rules.
* <p>
* To be valid, the local date-time must not be in a gap and the offset
* must match the valid offsets.
*
* @param {LocalDateTime} localDateTime - the date-time to check, not null, but null
* may be ignored if the rules have a single offset for all instants
* @param {ZoneOffset} offset - the offset to check, null returns false
* @return {boolean} true if the offset date-time is valid for these rules
*/
isValidOffset(localDateTime, offset){
return this.validOffsets(localDateTime).some( o => o.equals(offset));
}
//-----------------------------------------------------------------------
/**
* Gets the next transition after the specified instant.
* <p>
* This returns details of the next transition after the specified instant.
* For example, if the instant represents a point where "Summer" daylight savings time
* applies, then the method will return the transition to the next "Winter" time.
*
* @param {Instant} instant - the instant to get the next transition after, not null, but null
* may be ignored if the rules have a single offset for all instants
* @return {ZoneOffsetTransition} the next transition after the specified instant, null if this is after the last transition
*/
// eslint-disable-next-line no-unused-vars
nextTransition(instant){
notSupported('ZoneRules.nextTransition');
}
/**
* Gets the previous transition before the specified instant.
* <p>
* This returns details of the previous transition after the specified instant.
* For example, if the instant represents a point where "summer" daylight saving time
* applies, then the method will return the transition from the previous "winter" time.
*
* @param {Instant} instant - the instant to get the previous transition after, not null, but null
* may be ignored if the rules have a single offset for all instants
* @return {ZoneOffsetTransition} the previous transition after the specified instant, null if this is before the first transition
*/
// eslint-disable-next-line no-unused-vars
previousTransition(instant){
notSupported('ZoneRules.previousTransition');
}
/**
* Gets the complete list of fully defined transitions.
* <p>
* The complete set of transitions for this rules instance is defined by this method
* and {@link #getTransitionRules()}. This method returns those transitions that have
* been fully defined. These are typically historical, but may be in the future.
* <p>
* The list will be empty for fixed offset rules and for any time-zone where there has
* only ever been a single offset. The list will also be empty if the transition rules are unknown.
*
* @return {ZoneOffsetTransition[]} an immutable list of fully defined transitions, not null
*/
transitions(){
notSupported('ZoneRules.transitions');
}
/**
* Gets the list of transition rules for years beyond those defined in the transition list.
* <p>
* The complete set of transitions for this rules instance is defined by this method
* and {@link #getTransitions()}. This method returns instances of {@link ZoneOffsetTransitionRule}
* that define an algorithm for when transitions will occur.
* <p>
* For any given {@code ZoneRules}, this list contains the transition rules for years
* beyond those years that have been fully defined. These rules typically refer to future
* daylight saving time rule changes.
* <p>
* If the zone defines daylight savings into the future, then the list will normally
* be of size two and hold information about entering and exiting daylight savings.
* If the zone does not have daylight savings, or information about future changes
* is uncertain, then the list will be empty.
* <p>
* The list will be empty for fixed offset rules and for any time-zone where there is no
* daylight saving time. The list will also be empty if the transition rules are unknown.
*
* @return {ZoneOffsetTransitionRule[]} an immutable list of transition rules, not null
*/
transitionRules(){
notSupported('ZoneRules.transitionRules');
}
/**
*
* @param other
* @returns {boolean}
*/
equals(other) {
if (this === other) {
return true;
}
if (other instanceof MomentZoneRules) {
return this._tzdbInfo === other._tzdbInfo;
}
return false;
}
/**
*
* @returns {string}
*/
toString() {
return this._tzdbInfo.name;
}
}
class LDTUntils {
constructor(_tzdbUntils, tzdbOffsets) {
this._tzdbUntils = _tzdbUntils;
this._tzdbOffsets = tzdbOffsets;
this._ldtUntils = [];
this.size = this._tzdbUntils.length * 2;
}
_generateTupple(index) {
const epochMillis = this._tzdbUntils[index];
if (epochMillis === Infinity) {
return [LocalDateTime.MAX, LocalDateTime.MAX];
}
const instant = Instant.ofEpochMilli(epochMillis);
const offset1 = offsetInSeconds(this._tzdbOffsets[index]);
const zone1 = ZoneOffset.ofTotalSeconds(-offset1);
const ldt1 = LocalDateTime.ofInstant(instant, zone1);
const nextIndex = Math.min(index + 1, this._tzdbOffsets.length - 1);
const offset2 = offsetInSeconds(this._tzdbOffsets[nextIndex]);
const zone2 = ZoneOffset.ofTotalSeconds(-offset2);
const ldt2 = LocalDateTime.ofInstant(instant, zone2);
if(offset1 > offset2) {
return [ldt1, ldt2];
} else {
return [ldt2, ldt1];
}
}
_getTupple(index){
if (this._ldtUntils[index] == null) {
this._ldtUntils[index] = this._generateTupple(index);
}
return this._ldtUntils[index];
}
get(index) {
const ldtTupple = this._getTupple(index >> 1);
return ldtTupple[index % 2];
}
}
// modified bin-search, to always find existing indices for non-empty arrays
// value in array at index is larger than input value (or last index of array)
function ldtBinarySearch(array, value) {
let hi = array.size - 1, lo = -1, mid;
while (hi - lo > 1) {
if (!value.isBefore(array.get(mid = hi + lo >> 1))) {
lo = mid;
} else {
hi = mid;
}
}
return hi;
}
function offsetInSeconds(tzdbOffset){
return roundDown(+tzdbOffset*60);
}
function roundDown(r){
if (r < 0) {
return Math.ceil(r);
} else {
return Math.floor(r);
}
}
// modified bin-search, to always find existing indices for non-empty arrays
// value in array at index is larger than input value (or last index of array)
function binarySearch(array, value) {
let hi = array.length - 1, lo = -1, mid;
while (hi - lo > 1) {
if (array[mid = hi + lo >> 1] <= value) {
lo = mid;
} else {
hi = mid;
}
}
return hi;
}
function notSupported(msg){
throw new Error(`not supported: ${msg}`);
}
