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/*
* This file is available under and governed by the GNU General Public
* License version 2 only, as published by the Free Software Foundation.
* However, the following notice accompanied the original version of this
* file:
*
* Copyright (c) 2009-2012, Stephen Colebourne & Michael Nascimento Santos
*
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
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package build.tools.tzdb;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Objects;
/**
* A transition between two offsets caused by a discontinuity in the local time-line.
*
* @since 1.8
*/
final class ZoneOffsetTransition implements Comparable<ZoneOffsetTransition> {
/**
* The local transition date-time at the transition.
*/
private final LocalDateTime transition;
/**
* The offset before transition.
*/
private final ZoneOffset offsetBefore;
/**
* The offset after transition.
*/
private final ZoneOffset offsetAfter;
/**
* Creates an instance defining a transition between two offsets.
*
* @param transition the transition date-time with the offset before the transition, not null
* @param offsetBefore the offset before the transition, not null
* @param offsetAfter the offset at and after the transition, not null
*/
ZoneOffsetTransition(LocalDateTime transition, ZoneOffset offsetBefore, ZoneOffset offsetAfter) {
Objects.requireNonNull(transition, "transition");
Objects.requireNonNull(offsetBefore, "offsetBefore");
Objects.requireNonNull(offsetAfter, "offsetAfter");
if (offsetBefore.equals(offsetAfter)) {
throw new IllegalArgumentException("Offsets must not be equal");
}
this.transition = transition;
this.offsetBefore = offsetBefore;
this.offsetAfter = offsetAfter;
}
/**
* Creates an instance from epoch-second and offsets.
*
* @param epochSecond the transition epoch-second
* @param offsetBefore the offset before the transition, not null
* @param offsetAfter the offset at and after the transition, not null
*/
ZoneOffsetTransition(long epochSecond, ZoneOffset offsetBefore, ZoneOffset offsetAfter) {
this.transition = LocalDateTime.ofEpochSecond(epochSecond, 0, offsetBefore);
this.offsetBefore = offsetBefore;
this.offsetAfter = offsetAfter;
}
/**
* Gets the transition instant as an epoch second.
*
* @return the transition epoch second
*/
public long toEpochSecond() {
return transition.toEpochSecond(offsetBefore);
}
/**
* Gets the local transition date-time, as would be expressed with the 'before' offset.
* <p>
* This is the date-time where the discontinuity begins expressed with the 'before' offset.
* At this instant, the 'after' offset is actually used, therefore the combination of this
* date-time and the 'before' offset will never occur.
* <p>
* The combination of the 'before' date-time and offset represents the same instant
* as the 'after' date-time and offset.
*
* @return the transition date-time expressed with the before offset, not null
*/
public LocalDateTime getDateTimeBefore() {
return transition;
}
/**
* Gets the local transition date-time, as would be expressed with the 'after' offset.
* <p>
* This is the first date-time after the discontinuity, when the new offset applies.
* <p>
* The combination of the 'before' date-time and offset represents the same instant
* as the 'after' date-time and offset.
*
* @return the transition date-time expressed with the after offset, not null
*/
public LocalDateTime getDateTimeAfter() {
return transition.plusSeconds(getDurationSeconds());
}
/**
* Gets the offset before the transition.
* <p>
* This is the offset in use before the instant of the transition.
*
* @return the offset before the transition, not null
*/
public ZoneOffset getOffsetBefore() {
return offsetBefore;
}
/**
* Gets the offset after the transition.
* <p>
* This is the offset in use on and after the instant of the transition.
*
* @return the offset after the transition, not null
*/
public ZoneOffset getOffsetAfter() {
return offsetAfter;
}
/**
* Gets the duration of the transition in seconds.
*
* @return the duration in seconds
*/
private int getDurationSeconds() {
return getOffsetAfter().getTotalSeconds() - getOffsetBefore().getTotalSeconds();
}
/**
* Does this transition represent a gap in the local time-line.
* <p>
* Gaps occur where there are local date-times that simply do not not exist.
* An example would be when the offset changes from {@code +01:00} to {@code +02:00}.
* This might be described as 'the clocks will move forward one hour tonight at 1am'.
*
* @return true if this transition is a gap, false if it is an overlap
*/
public boolean isGap() {
return getOffsetAfter().getTotalSeconds() > getOffsetBefore().getTotalSeconds();
}
/**
* Does this transition represent a gap in the local time-line.
* <p>
* Overlaps occur where there are local date-times that exist twice.
* An example would be when the offset changes from {@code +02:00} to {@code +01:00}.
* This might be described as 'the clocks will move back one hour tonight at 2am'.
*
* @return true if this transition is an overlap, false if it is a gap
*/
public boolean isOverlap() {
return getOffsetAfter().getTotalSeconds() < getOffsetBefore().getTotalSeconds();
}
/**
* Checks if the specified offset is valid during this transition.
* <p>
* This checks to see if the given offset will be valid at some point in the transition.
* A gap will always return false.
* An overlap will return true if the offset is either the before or after offset.
*
* @param offset the offset to check, null returns false
* @return true if the offset is valid during the transition
*/
public boolean isValidOffset(ZoneOffset offset) {
return isGap() ? false : (getOffsetBefore().equals(offset) || getOffsetAfter().equals(offset));
}
/**
* Gets the valid offsets during this transition.
* <p>
* A gap will return an empty list, while an overlap will return both offsets.
*
* @return the list of valid offsets
*/
List<ZoneOffset> getValidOffsets() {
if (isGap()) {
return Collections.emptyList();
}
return Arrays.asList(getOffsetBefore(), getOffsetAfter());
}
/**
* Compares this transition to another based on the transition instant.
* <p>
* This compares the instants of each transition.
* The offsets are ignored, making this order inconsistent with equals.
*
* @param transition the transition to compare to, not null
* @return the comparator value, negative if less, positive if greater
*/
@Override
public int compareTo(ZoneOffsetTransition transition) {
return Long.compare(this.toEpochSecond(), transition.toEpochSecond());
}
/**
* Checks if this object equals another.
* <p>
* The entire state of the object is compared.
*
* @param other the other object to compare to, null returns false
* @return true if equal
*/
@Override
public boolean equals(Object other) {
if (other == this) {
return true;
}
if (other instanceof ZoneOffsetTransition) {
ZoneOffsetTransition d = (ZoneOffsetTransition) other;
return transition.equals(d.transition) &&
offsetBefore.equals(d.offsetBefore) && offsetAfter.equals(d.offsetAfter);
}
return false;
}
/**
* Returns a suitable hash code.
*
* @return the hash code
*/
@Override
public int hashCode() {
return transition.hashCode() ^ offsetBefore.hashCode() ^ Integer.rotateLeft(offsetAfter.hashCode(), 16);
}
}