/*
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* @copyright (c) 2016, Philipp Thürwächter & Pattrick Hüper
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* @copyright (c) 2007-present, Stephen Colebourne & Michael Nascimento Santos
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* @license BSD-3-Clause (see LICENSE in the root directory of this source tree)
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*/
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import { requireNonNull, requireInstance } from '../assert';
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import { ChronoField } from '../temporal/ChronoField';
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import { ChronoUnit } from '../temporal/ChronoUnit';
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import { DateTimeFormatter } from '../format/DateTimeFormatter';
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import { TemporalQueries } from '../temporal/TemporalQueries';
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import { Temporal } from '../temporal/Temporal';
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import { LocalDate } from '../LocalDate';
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/**
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* A date without time-of-day or time-zone in an arbitrary chronology, intended
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* for advanced globalization use cases.
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*
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* **Most applications should declare method signatures, fields and variables
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* as {@link LocalDate}, not this interface.**
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*
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* A {@link ChronoLocalDate} is the abstract representation of a date where the
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* {@link Chronology}, or calendar system, is pluggable.
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* The date is defined in terms of fields expressed by {@link TemporalField},
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* where most common implementations are defined in {@link ChronoField}.
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* The chronology defines how the calendar system operates and the meaning of
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* the standard fields.
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*
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* #### When to use this interface
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*
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* The design of the API encourages the use of {@link LocalDate} rather than this
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* interface, even in the case where the application needs to deal with multiple
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* calendar systems. The rationale for this is explored in the following documentation.
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*
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* The primary use case where this interface should be used is where the generic
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* type parameter `C` is fully defined as a specific chronology.
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* In that case, the assumptions of that chronology are known at development
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* time and specified in the code.
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*
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* When the chronology is defined in the generic type parameter as ? or otherwise
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* unknown at development time, the rest of the discussion below applies.
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*
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* To emphasize the point, declaring a method signature, field or variable as this
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* interface type can initially seem like the sensible way to globalize an application,
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* however it is usually the wrong approach.
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* As such, it should be considered an application-wide architectural decision to choose
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* to use this interface as opposed to {@link LocalDate}.
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*
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* #### Architectural issues to consider
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*
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* These are some of the points that must be considered before using this interface
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* throughout an application.
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*
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* 1) Applications using this interface, as opposed to using just {@link LocalDate},
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* face a significantly higher probability of bugs. This is because the calendar system
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* in use is not known at development time. A key cause of bugs is where the developer
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* applies assumptions from their day-to-day knowledge of the ISO calendar system
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* to code that is intended to deal with any arbitrary calendar system.
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* The section below outlines how those assumptions can cause problems
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* The primary mechanism for reducing this increased risk of bugs is a strong code review process.
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* This should also be considered a extra cost in maintenance for the lifetime of the code.
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*
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* 2) This interface does not enforce immutability of implementations.
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* While the implementation notes indicate that all implementations must be immutable
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* there is nothing in the code or type system to enforce this. Any method declared
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* to accept a {@link ChronoLocalDate} could therefore be passed a poorly or
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* maliciously written mutable implementation.
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*
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* 3) Applications using this interface must consider the impact of eras.
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* {@link LocalDate} shields users from the concept of eras, by ensuring that `getYear()`
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* returns the proleptic year. That decision ensures that developers can think of
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* {@link LocalDate} instances as consisting of three fields - year, month-of-year and day-of-month.
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* By contrast, users of this interface must think of dates as consisting of four fields -
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* era, year-of-era, month-of-year and day-of-month. The extra era field is frequently
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* forgotten, yet it is of vital importance to dates in an arbitrary calendar system.
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* For example, in the Japanese calendar system, the era represents the reign of an Emperor.
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* Whenever one reign ends and another starts, the year-of-era is reset to one.
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*
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* 4) The only agreed international standard for passing a date between two systems
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* is the ISO-8601 standard which requires the ISO calendar system. Using this interface
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* throughout the application will inevitably lead to the requirement to pass the date
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* across a network or component boundary, requiring an application specific protocol or format.
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*
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* 5) Long term persistence, such as a database, will almost always only accept dates in the
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* ISO-8601 calendar system (or the related Julian-Gregorian). Passing around dates in other
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* calendar systems increases the complications of interacting with persistence.
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*
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* 6) Most of the time, passing a {@link ChronoLocalDate} throughout an application
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* is unnecessary, as discussed in the last section below.
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*
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* #### False assumptions causing bugs in multi-calendar system code
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*
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* As indicated above, there are many issues to consider when try to use and manipulate a
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* date in an arbitrary calendar system. These are some of the key issues.
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*
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* Code that queries the day-of-month and assumes that the value will never be more than
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* 31 is invalid. Some calendar systems have more than 31 days in some months.
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*
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* Code that adds 12 months to a date and assumes that a year has been added is invalid.
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* Some calendar systems have a different number of months, such as 13 in the Coptic or Ethiopic.
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*
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* Code that adds one month to a date and assumes that the month-of-year value will increase
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* by one or wrap to the next year is invalid. Some calendar systems have a variable number
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* of months in a year, such as the Hebrew.
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*
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* Code that adds one month, then adds a second one month and assumes that the day-of-month
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* will remain close to its original value is invalid. Some calendar systems have a large difference
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* between the length of the longest month and the length of the shortest month.
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* For example, the Coptic or Ethiopic have 12 months of 30 days and 1 month of 5 days.
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*
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* Code that adds seven days and assumes that a week has been added is invalid.
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* Some calendar systems have weeks of other than seven days, such as the French Revolutionary.
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*
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* Code that assumes that because the year of `date1` is greater than the year of `date2`
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* then `date1` is after `date2` is invalid. This is invalid for all calendar systems
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* when referring to the year-of-era, and especially untrue of the Japanese calendar system
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* where the year-of-era restarts with the reign of every new Emperor.
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*
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* Code that treats month-of-year one and day-of-month one as the start of the year is invalid.
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* Not all calendar systems start the year when the month value is one.
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*
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* In general, manipulating a date, and even querying a date, is wide open to bugs when the
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* calendar system is unknown at development time. This is why it is essential that code using
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* this interface is subjected to additional code reviews. It is also why an architectural
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* decision to avoid this interface type is usually the correct one.
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*
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* #### Using LocalDate instead
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*
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* The primary alternative to using this interface throughout your application is as follows.
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*
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* * Declare all method signatures referring to dates in terms of {@link LocalDate}.
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* * Either store the chronology (calendar system) in the user profile or lookup the chronology
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* from the user locale.
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* * Convert the ISO {@link LocalDate} to and from the user's preferred calendar system during
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* printing and parsing.
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*
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* This approach treats the problem of globalized calendar systems as a localization issue
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* and confines it to the UI layer. This approach is in keeping with other localization
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* issues in the java platform.
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*
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* As discussed above, performing calculations on a date where the rules of the calendar system
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* are pluggable requires skill and is not recommended.
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* Fortunately, the need to perform calculations on a date in an arbitrary calendar system
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* is extremely rare. For example, it is highly unlikely that the business rules of a library
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* book rental scheme will allow rentals to be for one month, where meaning of the month
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* is dependent on the user's preferred calendar system.
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*
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* A key use case for calculations on a date in an arbitrary calendar system is producing
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* a month-by-month calendar for display and user interaction. Again, this is a UI issue,
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* and use of this interface solely within a few methods of the UI layer may be justified.
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*
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* In any other part of the system, where a date must be manipulated in a calendar system
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* other than ISO, the use case will generally specify the calendar system to use.
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* For example, an application may need to calculate the next Islamic or Hebrew holiday
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* which may require manipulating the date.
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* This kind of use case can be handled as follows:
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*
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* * start from the ISO {@link LocalDate} being passed to the method
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* * convert the date to the alternate calendar system, which for this use case is known
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* rather than arbitrary
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* * perform the calculation
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* * convert back to {@link LocalDate}
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*
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* Developers writing low-level frameworks or libraries should also avoid this interface.
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* Instead, one of the two general purpose access interfaces should be used.
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* Use {@link TemporalAccessor} if read-only access is required, or use {@link Temporal}
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* if read-write access is required.
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*
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* ### Specification for implementors
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*
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* This interface must be implemented with care to ensure other classes operate correctly.
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* All implementations that can be instantiated must be final, immutable and thread-safe.
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* Subclasses should be Serializable wherever possible.
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*
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* Additional calendar systems may be added to the system.
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* See {@link Chronology} for more details.
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*
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* In JDK 8, this is an interface with default methods.
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* Since there are no default methods in JDK 7, an abstract class is used.
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*/
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export class ChronoLocalDate extends Temporal {
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isSupported(fieldOrUnit) {
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if (fieldOrUnit instanceof ChronoField) {
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return fieldOrUnit.isDateBased();
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} else if (fieldOrUnit instanceof ChronoUnit) {
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return fieldOrUnit.isDateBased();
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}
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return fieldOrUnit != null && fieldOrUnit.isSupportedBy(this);
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}
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query(query) {
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if (query === TemporalQueries.chronology()) {
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return this.chronology();
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} else if (query === TemporalQueries.precision()) {
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return ChronoUnit.DAYS;
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} else if (query === TemporalQueries.localDate()) {
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return LocalDate.ofEpochDay(this.toEpochDay());
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} else if (query === TemporalQueries.localTime() || query === TemporalQueries.zone() ||
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query === TemporalQueries.zoneId() || query === TemporalQueries.offset()) {
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return null;
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}
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return super.query(query);
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}
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adjustInto(temporal) {
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return temporal.with(ChronoField.EPOCH_DAY, this.toEpochDay());
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}
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/**
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* Formats this date using the specified formatter.
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*
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* This date will be passed to the formatter to produce a string.
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*
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* The default implementation must behave as follows:
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* <pre>
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* return formatter.format(this);
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* </pre>
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*
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* @param {DateTimeFormatter} formatter the formatter to use, not null
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* @return {String} the formatted date string, not null
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* @throws DateTimeException if an error occurs during printing
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*/
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format(formatter) {
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requireNonNull(formatter, 'formatter');
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requireInstance(formatter, DateTimeFormatter, 'formatter');
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return formatter.format(this);
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}
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}
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