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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) 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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 *    this list of conditions and the following disclaimer in the documentation

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package java.time.chrono;

import static java.time.temporal.ChronoField.EPOCH_DAY;

import static java.time.temporal.ChronoField.ERA;

import static java.time.temporal.ChronoField.YEAR;

import static java.time.temporal.ChronoUnit.DAYS;

import java.time.DateTimeException;

import java.time.LocalDate;

import java.time.LocalTime;

import java.time.format.DateTimeFormatter;

import java.time.temporal.ChronoField;

import java.time.temporal.ChronoUnit;

import java.time.temporal.Temporal;

import java.time.temporal.TemporalAccessor;

import java.time.temporal.TemporalAdjuster;

import java.time.temporal.TemporalAmount;

import java.time.temporal.TemporalField;

import java.time.temporal.TemporalQueries;

import java.time.temporal.TemporalQuery;

import java.time.temporal.TemporalUnit;

import java.time.temporal.UnsupportedTemporalTypeException;

import java.util.Comparator;

import java.util.Objects;

/**

 * A date without time-of-day or time-zone in an arbitrary chronology, intended

 * for advanced globalization use cases.

 * <p>

 * <b>Most applications should declare method signatures, fields and variables

 * as {@link LocalDate}, not this interface.</b>

 * <p>

 * A {@code ChronoLocalDate} is the abstract representation of a date where the

 * {@code Chronology chronology}, or calendar system, is pluggable.

 * The date is defined in terms of fields expressed by {@link TemporalField},

 * where most common implementations are defined in {@link ChronoField}.

 * The chronology defines how the calendar system operates and the meaning of

 * the standard fields.

 *

 * <h3>When to use this interface</h3>

 * The design of the API encourages the use of {@code LocalDate} rather than this

 * interface, even in the case where the application needs to deal with multiple

 * calendar systems.

 * <p>

 * This concept can seem surprising at first, as the natural way to globalize an

 * application might initially appear to be to abstract the calendar system.

 * However, as explored below, abstracting the calendar system is usually the wrong

 * approach, resulting in logic errors and hard to find bugs.

 * As such, it should be considered an application-wide architectural decision to choose

 * to use this interface as opposed to {@code LocalDate}.

 *

 * <h3>Architectural issues to consider</h3>

 * These are some of the points that must be considered before using this interface

 * throughout an application.

 * <p>

 * 1) Applications using this interface, as opposed to using just {@code LocalDate},

 * face a significantly higher probability of bugs. This is because the calendar system

 * in use is not known at development time. A key cause of bugs is where the developer

 * applies assumptions from their day-to-day knowledge of the ISO calendar system

 * to code that is intended to deal with any arbitrary calendar system.

 * The section below outlines how those assumptions can cause problems

 * The primary mechanism for reducing this increased risk of bugs is a strong code review process.

 * This should also be considered a extra cost in maintenance for the lifetime of the code.

 * <p>

 * 2) This interface does not enforce immutability of implementations.

 * While the implementation notes indicate that all implementations must be immutable

 * there is nothing in the code or type system to enforce this. Any method declared

 * to accept a {@code ChronoLocalDate} could therefore be passed a poorly or

 * maliciously written mutable implementation.

 * <p>

 * 3) Applications using this interface  must consider the impact of eras.

 * {@code LocalDate} shields users from the concept of eras, by ensuring that {@code getYear()}

 * returns the proleptic year. That decision ensures that developers can think of

 * {@code LocalDate} instances as consisting of three fields - year, month-of-year and day-of-month.

 * By contrast, users of this interface must think of dates as consisting of four fields -

 * era, year-of-era, month-of-year and day-of-month. The extra era field is frequently

 * forgotten, yet it is of vital importance to dates in an arbitrary calendar system.

 * For example, in the Japanese calendar system, the era represents the reign of an Emperor.

 * Whenever one reign ends and another starts, the year-of-era is reset to one.

 * <p>

 * 4) The only agreed international standard for passing a date between two systems

 * is the ISO-8601 standard which requires the ISO calendar system. Using this interface

 * throughout the application will inevitably lead to the requirement to pass the date

 * across a network or component boundary, requiring an application specific protocol or format.

 * <p>

 * 5) Long term persistence, such as a database, will almost always only accept dates in the

 * ISO-8601 calendar system (or the related Julian-Gregorian). Passing around dates in other

 * calendar systems increases the complications of interacting with persistence.

 * <p>

 * 6) Most of the time, passing a {@code ChronoLocalDate} throughout an application

 * is unnecessary, as discussed in the last section below.

 *

 * <h3>False assumptions causing bugs in multi-calendar system code</h3>

 * As indicated above, there are many issues to consider when try to use and manipulate a

 * date in an arbitrary calendar system. These are some of the key issues.

 * <p>

 * Code that queries the day-of-month and assumes that the value will never be more than

 * 31 is invalid. Some calendar systems have more than 31 days in some months.

 * <p>

 * Code that adds 12 months to a date and assumes that a year has been added is invalid.

 * Some calendar systems have a different number of months, such as 13 in the Coptic or Ethiopic.

 * <p>

 * Code that adds one month to a date and assumes that the month-of-year value will increase

 * by one or wrap to the next year is invalid. Some calendar systems have a variable number

 * of months in a year, such as the Hebrew.

 * <p>

 * Code that adds one month, then adds a second one month and assumes that the day-of-month

 * will remain close to its original value is invalid. Some calendar systems have a large difference

 * between the length of the longest month and the length of the shortest month.

 * For example, the Coptic or Ethiopic have 12 months of 30 days and 1 month of 5 days.

 * <p>

 * Code that adds seven days and assumes that a week has been added is invalid.

 * Some calendar systems have weeks of other than seven days, such as the French Revolutionary.

 * <p>

 * Code that assumes that because the year of {@code date1} is greater than the year of {@code date2}

 * then {@code date1} is after {@code date2} is invalid. This is invalid for all calendar systems

 * when referring to the year-of-era, and especially untrue of the Japanese calendar system

 * where the year-of-era restarts with the reign of every new Emperor.

 * <p>

 * Code that treats month-of-year one and day-of-month one as the start of the year is invalid.

 * Not all calendar systems start the year when the month value is one.

 * <p>

 * In general, manipulating a date, and even querying a date, is wide open to bugs when the

 * calendar system is unknown at development time. This is why it is essential that code using

 * this interface is subjected to additional code reviews. It is also why an architectural

 * decision to avoid this interface type is usually the correct one.

 *

 * <h3>Using LocalDate instead</h3>

 * The primary alternative to using this interface throughout your application is as follows.

 * <ul>

 * <li>Declare all method signatures referring to dates in terms of {@code LocalDate}.

 * <li>Either store the chronology (calendar system) in the user profile or lookup

 *  the chronology from the user locale

 * <li>Convert the ISO {@code LocalDate} to and from the user's preferred calendar system during

 *  printing and parsing

 * </ul>

 * This approach treats the problem of globalized calendar systems as a localization issue

 * and confines it to the UI layer. This approach is in keeping with other localization

 * issues in the java platform.

 * <p>

 * As discussed above, performing calculations on a date where the rules of the calendar system

 * are pluggable requires skill and is not recommended.

 * Fortunately, the need to perform calculations on a date in an arbitrary calendar system

 * is extremely rare. For example, it is highly unlikely that the business rules of a library

 * book rental scheme will allow rentals to be for one month, where meaning of the month

 * is dependent on the user's preferred calendar system.

 * <p>

 * A key use case for calculations on a date in an arbitrary calendar system is producing

 * a month-by-month calendar for display and user interaction. Again, this is a UI issue,

 * and use of this interface solely within a few methods of the UI layer may be justified.

 * <p>

 * In any other part of the system, where a date must be manipulated in a calendar system

 * other than ISO, the use case will generally specify the calendar system to use.

 * For example, an application may need to calculate the next Islamic or Hebrew holiday

 * which may require manipulating the date.

 * This kind of use case can be handled as follows:

 * <ul>

 * <li>start from the ISO {@code LocalDate} being passed to the method

 * <li>convert the date to the alternate calendar system, which for this use case is known

 *  rather than arbitrary

 * <li>perform the calculation

 * <li>convert back to {@code LocalDate}

 * </ul>

 * Developers writing low-level frameworks or libraries should also avoid this interface.

 * Instead, one of the two general purpose access interfaces should be used.

 * Use {@link TemporalAccessor} if read-only access is required, or use {@link Temporal}

 * if read-write access is required.

 *

 * @implSpec

 * This interface must be implemented with care to ensure other classes operate correctly.

 * All implementations that can be instantiated must be final, immutable and thread-safe.

 * Subclasses should be Serializable wherever possible.

 * <p>

 * Additional calendar systems may be added to the system.

 * See {@link Chronology} for more details.

 *

 * @since 1.8

 */

public interface ChronoLocalDate

        extends Temporal, TemporalAdjuster, Comparable<ChronoLocalDate> {

    /**

     * Gets a comparator that compares {@code ChronoLocalDate} in

     * time-line order ignoring the chronology.

     * <p>

     * This comparator differs from the comparison in {@link #compareTo} in that it

     * only compares the underlying date and not the chronology.

     * This allows dates in different calendar systems to be compared based

     * on the position of the date on the local time-line.

     * The underlying comparison is equivalent to comparing the epoch-day.

     * @return a comparator that compares in time-line order ignoring the chronology

     * @see #isAfter

     * @see #isBefore

     * @see #isEqual

     */

    static Comparator<ChronoLocalDate> timeLineOrder() {

        return AbstractChronology.DATE_ORDER;

    }

    //-----------------------------------------------------------------------

    /**

     * Obtains an instance of {@code ChronoLocalDate} from a temporal object.

     * <p>

     * This obtains a local date based on the specified temporal.

     * A {@code TemporalAccessor} represents an arbitrary set of date and time information,

     * which this factory converts to an instance of {@code ChronoLocalDate}.

     * <p>

     * The conversion extracts and combines the chronology and the date

     * from the temporal object. The behavior is equivalent to using

     * {@link Chronology#date(TemporalAccessor)} with the extracted chronology.

     * Implementations are permitted to perform optimizations such as accessing

     * those fields that are equivalent to the relevant objects.

     * <p>

     * This method matches the signature of the functional interface {@link TemporalQuery}

     * allowing it to be used as a query via method reference, {@code ChronoLocalDate::from}.

     *

     * @param temporal  the temporal object to convert, not null

     * @return the date, not null

     * @throws DateTimeException if unable to convert to a {@code ChronoLocalDate}

     * @see Chronology#date(TemporalAccessor)

     */

    static ChronoLocalDate from(TemporalAccessor temporal) {

        if (temporal instanceof ChronoLocalDate) {

            return (ChronoLocalDate) temporal;

        }

        Objects.requireNonNull(temporal, "temporal");

        Chronology chrono = temporal.query(TemporalQueries.chronology());

        if (chrono == null) {

            throw new DateTimeException("Unable to obtain ChronoLocalDate from TemporalAccessor: " + temporal.getClass());

        }

        return chrono.date(temporal);

    }

    //-----------------------------------------------------------------------

    /**

     * Gets the chronology of this date.

     * <p>

     * The {@code Chronology} represents the calendar system in use.

     * The era and other fields in {@link ChronoField} are defined by the chronology.

     *

     * @return the chronology, not null

     */

    Chronology getChronology();

    /**

     * Gets the era, as defined by the chronology.

     * <p>

     * The era is, conceptually, the largest division of the time-line.

     * Most calendar systems have a single epoch dividing the time-line into two eras.

     * However, some have multiple eras, such as one for the reign of each leader.

     * The exact meaning is determined by the {@code Chronology}.

     * <p>

     * All correctly implemented {@code Era} classes are singletons, thus it

     * is valid code to write {@code date.getEra() == SomeChrono.ERA_NAME)}.

     * <p>

     * This default implementation uses {@link Chronology#eraOf(int)}.

     *

     * @return the chronology specific era constant applicable at this date, not null

     */

    default Era getEra() {

        return getChronology().eraOf(get(ERA));

    }

    /**

     * Checks if the year is a leap year, as defined by the calendar system.

     * <p>

     * A leap-year is a year of a longer length than normal.

     * The exact meaning is determined by the chronology with the constraint that

     * a leap-year must imply a year-length longer than a non leap-year.

     * <p>

     * This default implementation uses {@link Chronology#isLeapYear(long)}.

     *

     * @return true if this date is in a leap year, false otherwise

     */

    default boolean isLeapYear() {

        return getChronology().isLeapYear(getLong(YEAR));

    }

    /**

     * Returns the length of the month represented by this date, as defined by the calendar system.

     * <p>

     * This returns the length of the month in days.

     *

     * @return the length of the month in days

     */

    int lengthOfMonth();

    /**

     * Returns the length of the year represented by this date, as defined by the calendar system.

     * <p>

     * This returns the length of the year in days.

     * <p>

     * The default implementation uses {@link #isLeapYear()} and returns 365 or 366.

     *

     * @return the length of the year in days

     */

    default int lengthOfYear() {

        return (isLeapYear() ? 366 : 365);

    }

    /**

     * Checks if the specified field is supported.

     * <p>

     * This checks if the specified field can be queried on this date.

     * If false, then calling the {@link #range(TemporalField) range},

     * {@link #get(TemporalField) get} and {@link #with(TemporalField, long)}

     * methods will throw an exception.

     * <p>

     * The set of supported fields is defined by the chronology and normally includes

     * all {@code ChronoField} date fields.

     * <p>

     * If the field is not a {@code ChronoField}, then the result of this method

     * is obtained by invoking {@code TemporalField.isSupportedBy(TemporalAccessor)}

     * passing {@code this} as the argument.

     * Whether the field is supported is determined by the field.

     *

     * @param field  the field to check, null returns false

     * @return true if the field can be queried, false if not

     */

    @Override

    default boolean isSupported(TemporalField field) {

        if (field instanceof ChronoField) {

            return field.isDateBased();

        }

        return field != null && field.isSupportedBy(this);

    }

    /**

     * Checks if the specified unit is supported.

     * <p>

     * This checks if the specified unit can be added to or subtracted from this date.

     * If false, then calling the {@link #plus(long, TemporalUnit)} and

     * {@link #minus(long, TemporalUnit) minus} methods will throw an exception.

     * <p>

     * The set of supported units is defined by the chronology and normally includes

     * all {@code ChronoUnit} date units except {@code FOREVER}.

     * <p>

     * If the unit is not a {@code ChronoUnit}, then the result of this method

     * is obtained by invoking {@code TemporalUnit.isSupportedBy(Temporal)}

     * passing {@code this} as the argument.

     * Whether the unit is supported is determined by the unit.

     *

     * @param unit  the unit to check, null returns false

     * @return true if the unit can be added/subtracted, false if not

     */

    @Override

    default boolean isSupported(TemporalUnit unit) {

        if (unit instanceof ChronoUnit) {

            return unit.isDateBased();

        }

        return unit != null && unit.isSupportedBy(this);

    }

    //-----------------------------------------------------------------------

    // override for covariant return type

    /**

     * {@inheritDoc}

     * @throws DateTimeException {@inheritDoc}

     * @throws ArithmeticException {@inheritDoc}

     */

    @Override

    default ChronoLocalDate with(TemporalAdjuster adjuster) {

        return ChronoLocalDateImpl.ensureValid(getChronology(), Temporal.super.with(adjuster));

    }

    /**

     * {@inheritDoc}

     * @throws DateTimeException {@inheritDoc}

     * @throws UnsupportedTemporalTypeException {@inheritDoc}

     * @throws ArithmeticException {@inheritDoc}

     */

    @Override

    default ChronoLocalDate with(TemporalField field, long newValue) {

        if (field instanceof ChronoField) {

            throw new UnsupportedTemporalTypeException("Unsupported field: " + field);

        }

        return ChronoLocalDateImpl.ensureValid(getChronology(), field.adjustInto(this, newValue));

    }

    /**

     * {@inheritDoc}

     * @throws DateTimeException {@inheritDoc}

     * @throws ArithmeticException {@inheritDoc}

     */

    @Override

    default ChronoLocalDate plus(TemporalAmount amount) {

        return ChronoLocalDateImpl.ensureValid(getChronology(), Temporal.super.plus(amount));

    }

    /**

     * {@inheritDoc}

     * @throws DateTimeException {@inheritDoc}

     * @throws ArithmeticException {@inheritDoc}

     */

    @Override

    default ChronoLocalDate plus(long amountToAdd, TemporalUnit unit) {

        if (unit instanceof ChronoUnit) {

            throw new UnsupportedTemporalTypeException("Unsupported unit: " + unit);

        }

        return ChronoLocalDateImpl.ensureValid(getChronology(), unit.addTo(this, amountToAdd));

    }

    /**

     * {@inheritDoc}

     * @throws DateTimeException {@inheritDoc}

     * @throws ArithmeticException {@inheritDoc}

     */

    @Override

    default ChronoLocalDate minus(TemporalAmount amount) {

        return ChronoLocalDateImpl.ensureValid(getChronology(), Temporal.super.minus(amount));

    }

    /**

     * {@inheritDoc}

     * @throws DateTimeException {@inheritDoc}

     * @throws UnsupportedTemporalTypeException {@inheritDoc}

     * @throws ArithmeticException {@inheritDoc}

     */

    @Override

    default ChronoLocalDate minus(long amountToSubtract, TemporalUnit unit) {

        return ChronoLocalDateImpl.ensureValid(getChronology(), Temporal.super.minus(amountToSubtract, unit));

    }

    //-----------------------------------------------------------------------

    /**

     * Queries this date using the specified query.

     * <p>

     * This queries this date using the specified query strategy object.

     * The {@code TemporalQuery} object defines the logic to be used to

     * obtain the result. Read the documentation of the query to understand

     * what the result of this method will be.

     * <p>

     * The result of this method is obtained by invoking the

     * {@link TemporalQuery#queryFrom(TemporalAccessor)} method on the

     * specified query passing {@code this} as the argument.

     *

     * @param <R> the type of the result

     * @param query  the query to invoke, not null

     * @return the query result, null may be returned (defined by the query)

     * @throws DateTimeException if unable to query (defined by the query)

     * @throws ArithmeticException if numeric overflow occurs (defined by the query)

     */

    @SuppressWarnings("unchecked")

    @Override

    default <R> R query(TemporalQuery<R> query) {

        if (query == TemporalQueries.zoneId() || query == TemporalQueries.zone() || query == TemporalQueries.offset()) {

            return null;

        } else if (query == TemporalQueries.localTime()) {

            return null;

        } else if (query == TemporalQueries.chronology()) {

            return (R) getChronology();

        } else if (query == TemporalQueries.precision()) {