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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) 2011-2012, 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:

 *

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 *    this list of conditions and the following disclaimer.

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package java.time.temporal;

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

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

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

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

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

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

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

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

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

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

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

import java.io.InvalidObjectException;

import java.io.Serializable;

import java.time.DayOfWeek;

import java.time.chrono.ChronoLocalDate;

import java.time.chrono.Chronology;

import java.time.format.ResolverStyle;

import java.util.Collections;

import java.util.HashMap;

import java.util.Locale;

import java.util.Map;

import java.util.Objects;

import java.util.ResourceBundle;

import java.util.concurrent.ConcurrentHashMap;

import java.util.concurrent.ConcurrentMap;

import sun.util.locale.provider.CalendarDataUtility;

import sun.util.locale.provider.LocaleProviderAdapter;

import sun.util.locale.provider.LocaleResources;

/**

 * Localized definitions of the day-of-week, week-of-month and week-of-year fields.

 * <p>

 * A standard week is seven days long, but cultures have different definitions for some

 * other aspects of a week. This class represents the definition of the week, for the

 * purpose of providing {@link TemporalField} instances.

 * <p>

 * WeekFields provides five fields,

 * {@link #dayOfWeek()}, {@link #weekOfMonth()}, {@link #weekOfYear()},

 * {@link #weekOfWeekBasedYear()}, and {@link #weekBasedYear()}

 * that provide access to the values from any {@linkplain Temporal temporal object}.

 * <p>

 * The computations for day-of-week, week-of-month, and week-of-year are based

 * on the  {@linkplain ChronoField#YEAR proleptic-year},

 * {@linkplain ChronoField#MONTH_OF_YEAR month-of-year},

 * {@linkplain ChronoField#DAY_OF_MONTH day-of-month}, and

 * {@linkplain ChronoField#DAY_OF_WEEK ISO day-of-week} which are based on the

 * {@linkplain ChronoField#EPOCH_DAY epoch-day} and the chronology.

 * The values may not be aligned with the {@linkplain ChronoField#YEAR_OF_ERA year-of-Era}

 * depending on the Chronology.

 * <p>A week is defined by:

 * <ul>

 * <li>The first day-of-week.

 * For example, the ISO-8601 standard considers Monday to be the first day-of-week.

 * <li>The minimal number of days in the first week.

 * For example, the ISO-8601 standard counts the first week as needing at least 4 days.

 * </ul><p>

 * Together these two values allow a year or month to be divided into weeks.

 * <p>

 * <h3>Week of Month</h3>

 * One field is used: week-of-month.

 * The calculation ensures that weeks never overlap a month boundary.

 * The month is divided into periods where each period starts on the defined first day-of-week.

 * The earliest period is referred to as week 0 if it has less than the minimal number of days

 * and week 1 if it has at least the minimal number of days.

 * <p>

 * <table cellpadding="0" cellspacing="3" border="0" style="text-align: left; width: 50%;">

 * <caption>Examples of WeekFields</caption>

 * <tr><th>Date</th><td>Day-of-week</td>

 *  <td>First day: Monday<br>Minimal days: 4</td><td>First day: Monday<br>Minimal days: 5</td></tr>

 * <tr><th>2008-12-31</th><td>Wednesday</td>

 *  <td>Week 5 of December 2008</td><td>Week 5 of December 2008</td></tr>

 * <tr><th>2009-01-01</th><td>Thursday</td>

 *  <td>Week 1 of January 2009</td><td>Week 0 of January 2009</td></tr>

 * <tr><th>2009-01-04</th><td>Sunday</td>

 *  <td>Week 1 of January 2009</td><td>Week 0 of January 2009</td></tr>

 * <tr><th>2009-01-05</th><td>Monday</td>

 *  <td>Week 2 of January 2009</td><td>Week 1 of January 2009</td></tr>

 * </table>

 *

 * <h3>Week of Year</h3>

 * One field is used: week-of-year.

 * The calculation ensures that weeks never overlap a year boundary.

 * The year is divided into periods where each period starts on the defined first day-of-week.

 * The earliest period is referred to as week 0 if it has less than the minimal number of days

 * and week 1 if it has at least the minimal number of days.

 *

 * <h3>Week Based Year</h3>

 * Two fields are used for week-based-year, one for the

 * {@link #weekOfWeekBasedYear() week-of-week-based-year} and one for

 * {@link #weekBasedYear() week-based-year}.  In a week-based-year, each week

 * belongs to only a single year.  Week 1 of a year is the first week that

 * starts on the first day-of-week and has at least the minimum number of days.

 * The first and last weeks of a year may contain days from the

 * previous calendar year or next calendar year respectively.

 *

 * <table cellpadding="0" cellspacing="3" border="0" style="text-align: left; width: 50%;">

 * <caption>Examples of WeekFields for week-based-year</caption>

 * <tr><th>Date</th><td>Day-of-week</td>

 *  <td>First day: Monday<br>Minimal days: 4</td><td>First day: Monday<br>Minimal days: 5</td></tr>

 * <tr><th>2008-12-31</th><td>Wednesday</td>

 *  <td>Week 1 of 2009</td><td>Week 53 of 2008</td></tr>

 * <tr><th>2009-01-01</th><td>Thursday</td>

 *  <td>Week 1 of 2009</td><td>Week 53 of 2008</td></tr>

 * <tr><th>2009-01-04</th><td>Sunday</td>

 *  <td>Week 1 of 2009</td><td>Week 53 of 2008</td></tr>

 * <tr><th>2009-01-05</th><td>Monday</td>

 *  <td>Week 2 of 2009</td><td>Week 1 of 2009</td></tr>

 * </table>

 *

 * @implSpec

 * This class is immutable and thread-safe.

 *

 * @since 1.8

 */

public final class WeekFields implements Serializable {

    // implementation notes

    // querying week-of-month or week-of-year should return the week value bound within the month/year

    // however, setting the week value should be lenient (use plus/minus weeks)

    // allow week-of-month outer range [0 to 6]

    // allow week-of-year outer range [0 to 54]

    // this is because callers shouldn't be expected to know the details of validity

    /**

     * The cache of rules by firstDayOfWeek plus minimalDays.

     * Initialized first to be available for definition of ISO, etc.

     */

    private static final ConcurrentMap<String, WeekFields> CACHE = new ConcurrentHashMap<>(4, 0.75f, 2);

    /**

     * The ISO-8601 definition, where a week starts on Monday and the first week

     * has a minimum of 4 days.

     * <p>

     * The ISO-8601 standard defines a calendar system based on weeks.

     * It uses the week-based-year and week-of-week-based-year concepts to split

     * up the passage of days instead of the standard year/month/day.

     * <p>

     * Note that the first week may start in the previous calendar year.

     * Note also that the first few days of a calendar year may be in the

     * week-based-year corresponding to the previous calendar year.

     */

    public static final WeekFields ISO = new WeekFields(DayOfWeek.MONDAY, 4);

    /**

     * The common definition of a week that starts on Sunday and the first week

     * has a minimum of 1 day.

     * <p>

     * Defined as starting on Sunday and with a minimum of 1 day in the month.

     * This week definition is in use in the US and other European countries.

     */

    public static final WeekFields SUNDAY_START = WeekFields.of(DayOfWeek.SUNDAY, 1);

    /**

     * The unit that represents week-based-years for the purpose of addition and subtraction.

     * <p>

     * This allows a number of week-based-years to be added to, or subtracted from, a date.

     * The unit is equal to either 52 or 53 weeks.

     * The estimated duration of a week-based-year is the same as that of a standard ISO

     * year at {@code 365.2425 Days}.

     * <p>

     * The rules for addition add the number of week-based-years to the existing value

     * for the week-based-year field retaining the week-of-week-based-year

     * and day-of-week, unless the week number it too large for the target year.

     * In that case, the week is set to the last week of the year

     * with the same day-of-week.

     * <p>

     * This unit is an immutable and thread-safe singleton.

     */

    public static final TemporalUnit WEEK_BASED_YEARS = IsoFields.WEEK_BASED_YEARS;

    /**

     * Serialization version.

     */

    private static final long serialVersionUID = -1177360819670808121L;

    /**

     * The first day-of-week.

     */

    private final DayOfWeek firstDayOfWeek;

    /**

     * The minimal number of days in the first week.

     */

    private final int minimalDays;

    /**

     * The field used to access the computed DayOfWeek.

     */

    private transient final TemporalField dayOfWeek = ComputedDayOfField.ofDayOfWeekField(this);

    /**

     * The field used to access the computed WeekOfMonth.

     */

    private transient final TemporalField weekOfMonth = ComputedDayOfField.ofWeekOfMonthField(this);

    /**

     * The field used to access the computed WeekOfYear.

     */

    private transient final TemporalField weekOfYear = ComputedDayOfField.ofWeekOfYearField(this);

    /**

     * The field that represents the week-of-week-based-year.

     * <p>

     * This field allows the week of the week-based-year value to be queried and set.

     * <p>

     * This unit is an immutable and thread-safe singleton.

     */

    private transient final TemporalField weekOfWeekBasedYear = ComputedDayOfField.ofWeekOfWeekBasedYearField(this);

    /**

     * The field that represents the week-based-year.

     * <p>

     * This field allows the week-based-year value to be queried and set.

     * <p>

     * This unit is an immutable and thread-safe singleton.

     */

    private transient final TemporalField weekBasedYear = ComputedDayOfField.ofWeekBasedYearField(this);

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

    /**

     * Obtains an instance of {@code WeekFields} appropriate for a locale.

     * <p>

     * This will look up appropriate values from the provider of localization data.

     *

     * @param locale  the locale to use, not null

     * @return the week-definition, not null

     */

    public static WeekFields of(Locale locale) {

        Objects.requireNonNull(locale, "locale");

        locale = new Locale(locale.getLanguage(), locale.getCountry());  // elminate variants

        int calDow = CalendarDataUtility.retrieveFirstDayOfWeek(locale);

        DayOfWeek dow = DayOfWeek.SUNDAY.plus(calDow - 1);

        int minDays = CalendarDataUtility.retrieveMinimalDaysInFirstWeek(locale);

        return WeekFields.of(dow, minDays);

    }

    /**

     * Obtains an instance of {@code WeekFields} from the first day-of-week and minimal days.

     * <p>

     * The first day-of-week defines the ISO {@code DayOfWeek} that is day 1 of the week.

     * The minimal number of days in the first week defines how many days must be present

     * in a month or year, starting from the first day-of-week, before the week is counted

     * as the first week. A value of 1 will count the first day of the month or year as part

     * of the first week, whereas a value of 7 will require the whole seven days to be in

     * the new month or year.

     * <p>

     * WeekFields instances are singletons; for each unique combination

     * of {@code firstDayOfWeek} and {@code minimalDaysInFirstWeek} the

     * the same instance will be returned.

     *

     * @param firstDayOfWeek  the first day of the week, not null

     * @param minimalDaysInFirstWeek  the minimal number of days in the first week, from 1 to 7

     * @return the week-definition, not null

     * @throws IllegalArgumentException if the minimal days value is less than one

     *      or greater than 7

     */

    public static WeekFields of(DayOfWeek firstDayOfWeek, int minimalDaysInFirstWeek) {

        String key = firstDayOfWeek.toString() + minimalDaysInFirstWeek;

        WeekFields rules = CACHE.get(key);

        if (rules == null) {

            rules = new WeekFields(firstDayOfWeek, minimalDaysInFirstWeek);

            CACHE.putIfAbsent(key, rules);

            rules = CACHE.get(key);

        }

        return rules;

    }

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

    /**

     * Creates an instance of the definition.

     *

     * @param firstDayOfWeek  the first day of the week, not null

     * @param minimalDaysInFirstWeek  the minimal number of days in the first week, from 1 to 7

     * @throws IllegalArgumentException if the minimal days value is invalid

     */

    private WeekFields(DayOfWeek firstDayOfWeek, int minimalDaysInFirstWeek) {

        Objects.requireNonNull(firstDayOfWeek, "firstDayOfWeek");

        if (minimalDaysInFirstWeek < 1 || minimalDaysInFirstWeek > 7) {

            throw new IllegalArgumentException("Minimal number of days is invalid");

        }

        this.firstDayOfWeek = firstDayOfWeek;

        this.minimalDays = minimalDaysInFirstWeek;

    }

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

    /**

     * Return the singleton WeekFields associated with the

     * {@code firstDayOfWeek} and {@code minimalDays}.

     * @return the singleton WeekFields for the firstDayOfWeek and minimalDays.

     * @throws InvalidObjectException if the serialized object has invalid

     *     values for firstDayOfWeek or minimalDays.

     */

    private Object readResolve() throws InvalidObjectException {

        try {

            return WeekFields.of(firstDayOfWeek, minimalDays);

        } catch (IllegalArgumentException iae) {

            throw new InvalidObjectException("Invalid serialized WeekFields: " + iae.getMessage());

        }

    }

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

    /**

     * Gets the first day-of-week.

     * <p>

     * The first day-of-week varies by culture.

     * For example, the US uses Sunday, while France and the ISO-8601 standard use Monday.

     * This method returns the first day using the standard {@code DayOfWeek} enum.

     *

     * @return the first day-of-week, not null

     */

    public DayOfWeek getFirstDayOfWeek() {

        return firstDayOfWeek;

    }

    /**

     * Gets the minimal number of days in the first week.

     * <p>

     * The number of days considered to define the first week of a month or year

     * varies by culture.

     * For example, the ISO-8601 requires 4 days (more than half a week) to

     * be present before counting the first week.

     *

     * @return the minimal number of days in the first week of a month or year, from 1 to 7

     */

    public int getMinimalDaysInFirstWeek() {

        return minimalDays;

    }

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

    /**

     * Returns a field to access the day of week based on this {@code WeekFields}.

     * <p>

     * This is similar to {@link ChronoField#DAY_OF_WEEK} but uses values for

     * the day-of-week based on this {@code WeekFields}.

     * The days are numbered from 1 to 7 where the

     * {@link #getFirstDayOfWeek() first day-of-week} is assigned the value 1.

     * <p>

     * For example, if the first day-of-week is Sunday, then that will have the

     * value 1, with other days ranging from Monday as 2 to Saturday as 7.

     *

     * @return a field providing access to the day-of-week with localized numbering, not null

     */

    public TemporalField dayOfWeek() {

        return dayOfWeek;

    }

    /**

     * Returns a field to access the week of month based on this {@code WeekFields}.

     * <p>

     * This represents the concept of the count of weeks within the month where weeks

     * start on a fixed day-of-week, such as Monday.

     * This field is typically used with {@link WeekFields#dayOfWeek()}.

     * <p>

     * Week one (1) is the week starting on the {@link WeekFields#getFirstDayOfWeek}

     * where there are at least {@link WeekFields#getMinimalDaysInFirstWeek()} days in the month.

     * Thus, week one may start up to {@code minDays} days before the start of the month.

     * If the first week starts after the start of the month then the period before is week zero (0).

     * <p>

     * For example:<br>

     * - if the 1st day of the month is a Monday, week one starts on the 1st and there is no week zero<br>

     * - if the 2nd day of the month is a Monday, week one starts on the 2nd and the 1st is in week zero<br>

     * - if the 4th day of the month is a Monday, week one starts on the 4th and the 1st to 3rd is in week zero<br>

     * - if the 5th day of the month is a Monday, week two starts on the 5th and the 1st to 4th is in week one<br>

     * <p>

     * This field can be used with any calendar system.

     *

     * @return a field providing access to the week-of-month, not null

     */

    public TemporalField weekOfMonth() {

        return weekOfMonth;

    }

    /**

     * Returns a field to access the week of year based on this {@code WeekFields}.

     * <p>

     * This represents the concept of the count of weeks within the year where weeks

     * start on a fixed day-of-week, such as Monday.

     * This field is typically used with {@link WeekFields#dayOfWeek()}.

     * <p>

     * Week one(1) is the week starting on the {@link WeekFields#getFirstDayOfWeek}

     * where there are at least {@link WeekFields#getMinimalDaysInFirstWeek()} days in the year.

     * Thus, week one may start up to {@code minDays} days before the start of the year.

     * If the first week starts after the start of the year then the period before is week zero (0).

     * <p>

     * For example:<br>

     * - if the 1st day of the year is a Monday, week one starts on the 1st and there is no week zero<br>

     * - if the 2nd day of the year is a Monday, week one starts on the 2nd and the 1st is in week zero<br>

     * - if the 4th day of the year is a Monday, week one starts on the 4th and the 1st to 3rd is in week zero<br>

     * - if the 5th day of the year is a Monday, week two starts on the 5th and the 1st to 4th is in week one<br>

     * <p>

     * This field can be used with any calendar system.

     *

     * @return a field providing access to the week-of-year, not null

     */

    public TemporalField weekOfYear() {

        return weekOfYear;

    }

    /**

     * Returns a field to access the week of a week-based-year based on this {@code WeekFields}.

     * <p>

     * This represents the concept of the count of weeks within the year where weeks

     * start on a fixed day-of-week, such as Monday and each week belongs to exactly one year.

     * This field is typically used with {@link WeekFields#dayOfWeek()} and

     * {@link WeekFields#weekBasedYear()}.

     * <p>

     * Week one(1) is the week starting on the {@link WeekFields#getFirstDayOfWeek}

     * where there are at least {@link WeekFields#getMinimalDaysInFirstWeek()} days in the year.

     * If the first week starts after the start of the year then the period before