packages/core/src/temporal/TemporalUnit.js
/*
* @copyright (c) 2016, 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 { abstractMethodFail } from '../assert';
/**
* A unit of date-time, such as Days or Hours.
*
* Measurement of time is built on units, such as years, months, days, hours, minutes and seconds.
* Implementations of this interface represent those units.
*
* An instance of this interface represents the unit itself, rather than an amount of the unit.
* See {@link Period} for a class that represents an amount in terms of the common units.
*
* The most commonly used units are defined in {@link ChronoUnit}.
* Further units are supplied in {@link IsoFields}.
* Units can also be written by application code by implementing this interface.
*
* The unit works using double dispatch. Client code calls methods on a date-time like
* {@link LocalDateTime} which check if the unit is a {@link ChronoUnit}.
* If it is, then the date-time must handle it.
* Otherwise, the method call is re-dispatched to the matching method in this interface.
*
* @interface
*/
export class TemporalUnit {
/**
* Gets the duration of this unit, which may be an estimate.
*
* All units return a duration measured in standard nanoseconds from this method.
* The duration will be positive and non-zero.
* For example, an hour has a duration of `60 * 60 * 1,000,000,000 ns`.
*
* Some units may return an accurate duration while others return an estimate.
* For example, days have an estimated duration due to the possibility of
* daylight saving time changes.
* To determine if the duration is an estimate, use {@link isDurationEstimated}.
*
* @return {Duration} the duration of this unit, which may be an estimate.
*/
duration() {
abstractMethodFail('duration');
}
/**
* Checks if the duration of the unit is an estimate.
*
* All units have a duration, however the duration is not always accurate.
* For example, days have an estimated duration due to the possibility of
* daylight saving time changes.
* This method returns true if the duration is an estimate and false if it is
* accurate. Note that accurate/estimated ignores leap seconds.
*
* @return {boolean} `true` if the duration is estimated, `false` if accurate.
*/
isDurationEstimated() {
abstractMethodFail('isDurationEstimated');
}
/**
* Checks if this unit is date-based.
*
* @return {boolean} `true` if date unit, `false` if a time unit.
*/
isDateBased() {
abstractMethodFail('isDateBased');
}
/**
* Checks if this unit is time-based.
*
* @return {boolean} `true` if time unit, `false` if a date unit.
*/
isTimeBased() {
abstractMethodFail('isTimeBased');
}
//-----------------------------------------------------------------------
/**
* Checks if this unit is supported by the specified temporal object.
*
* This checks that the implementing date-time can add/subtract this unit.
* This can be used to avoid throwing an exception.
*
* @param {!Temporal} temporal the temporal object to check.
* @return {boolean} `true` if the unit is supported.
*/
// eslint-disable-next-line no-unused-vars
isSupportedBy(temporal) {
abstractMethodFail('isSupportedBy');
}
/**
* Returns a copy of the specified temporal object with the specified period added.
*
* The period added is a multiple of this unit. For example, this method
* could be used to add "3 days" to a date by calling this method on the
* instance representing "days", passing the date and the period "3".
* The period to be added may be negative, which is equivalent to subtraction.
*
* There are two equivalent ways of using this method.
* The first is to invoke this method directly.
* The second is to use {@link Temporal#plus}:
* <pre>
* // these two lines are equivalent, but the second approach is recommended
* temporal = thisUnit.doPlus(temporal);
* temporal = temporal.plus(thisUnit);
* </pre>
* It is recommended to use the second approach, {@link plus},
* as it is a lot clearer to read in code.
*
* Implementations should perform any queries or calculations using the units
* available in {@link ChronoUnit} or the fields available in {@link ChronoField}.
* If the field is not supported a {@link DateTimeException} must be thrown.
*
* Implementations must not alter the specified temporal object.
* Instead, an adjusted copy of the original must be returned.
* This provides equivalent, safe behavior for immutable and mutable implementations.
*
* @param {!Temporal} dateTime the temporal object to adjust.
* @param {number} periodToAdd the period of this unit to add, positive or negative.
* @return {Temporal} the adjusted temporal object.
* @throws DateTimeException if the period cannot be added.
*/
// eslint-disable-next-line no-unused-vars
addTo(dateTime, periodToAdd) {
abstractMethodFail('addTo');
}
//-----------------------------------------------------------------------
/**
* Calculates the period in terms of this unit between two temporal objects of the same type.
*
* This calculates the period between two temporals in terms of this unit.
* The start and end points are supplied as temporal objects and must be of the same type.
* The result will be negative if the end is before the start.
* For example, the period in hours between two temporal objects can be calculated
* using {@link HOURS.between}.
*
* The calculation returns a whole number, representing the number of complete units between the two temporals.
* For example, the period in hours between the times 11:30 and 13:29 will only be
* one hour as it is one minute short of two hours.
*
* There are two equivalent ways of using this method.
* The first is to invoke this method directly.
* The second is to use {@link Temporal#until}:
* <pre>
* // these two lines are equivalent
* between = thisUnit.between(start, end);
* between = start.until(end, thisUnit);
* </pre>
* The choice should be made based on which makes the code more readable.
*
* For example, this method allows the number of days between two dates to be calculated:
* <pre>
* long daysBetween = DAYS.between(start, end);
* // or alternatively
* long daysBetween = start.until(end, DAYS);
* </pre>
* Implementations should perform any queries or calculations using the units available in
* {@link ChronoUnit} or the fields available in {@link ChronoField}.
* If the unit is not supported a {@link DateTimeException} must be thrown.
* Implementations must not alter the specified temporal objects.
*
* @param {!Temporal} temporal1 the base temporal object.
* @param {!Temporal} temporal2 the other temporal object.
* @return {number} the period between temporal1 and temporal2 in terms of this unit;
* positive if temporal2 is later than temporal1, negative if earlier.
* @throws DateTimeException if the period cannot be calculated.
* @throws ArithmeticException if numeric overflow occurs.
*/
// eslint-disable-next-line no-unused-vars
between(temporal1, temporal2) {
abstractMethodFail('between');
}
}
