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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

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package java.time.chrono;

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

import java.io.DataInput;

import java.io.DataOutput;

import java.io.IOException;

import java.io.InvalidObjectException;

import java.io.ObjectStreamException;

import java.io.Serializable;

import java.time.DateTimeException;

import java.time.LocalDate;

import java.time.temporal.ChronoField;

import java.time.temporal.TemporalField;

import java.time.temporal.UnsupportedTemporalTypeException;

import java.time.temporal.ValueRange;

import java.util.Arrays;

import java.util.Objects;

import sun.util.calendar.CalendarDate;

/**

 * An era in the Japanese Imperial calendar system.

 * <p>

 * This class defines the valid eras for the Japanese chronology.

 * Only Meiji (1868-09-08 - 1912-07-29) and later eras are supported.

 * Japan introduced the Gregorian calendar since Meiji 6. The dates

 * between Meiji 1 - 5 are not historically correct.

 * The older eras are recognized as Seireki (Western calendar) era,

 * and the year of era of Seireki is proleptic Gregorian year.

 * (The Julian to Gregorian transition is not supported.)

 *

 * This class is immutable and thread-safe.

 *

 * @since 1.8

 */

public final class JapaneseEra

        implements Era, Serializable {

    // The offset value to 0-based index from the era value.

    // i.e., getValue() + ERA_OFFSET == 0-based index; except that -999 is mapped to zero

    static final int ERA_OFFSET = 2;

    static final sun.util.calendar.Era[] ERA_CONFIG;

    /**

     * The singleton instance for the before Meiji era ( - 1868-09-07)

     * which has the value -999.

     */

    public static final JapaneseEra SEIREKI = new JapaneseEra(-999, LocalDate.MIN);

    /**

     * The singleton instance for the 'Meiji' era (1868-09-08 - 1912-07-29)

     * which has the value -1.

     */

    public static final JapaneseEra MEIJI = new JapaneseEra(-1, LocalDate.of(1868, 9, 8));

    /**

     * The singleton instance for the 'Taisho' era (1912-07-30 - 1926-12-24)

     * which has the value 0.

     */

    public static final JapaneseEra TAISHO = new JapaneseEra(0, LocalDate.of(1912, 7, 30));

    /**

     * The singleton instance for the 'Showa' era (1926-12-25 - 1989-01-07)

     * which has the value 1.

     */

    public static final JapaneseEra SHOWA = new JapaneseEra(1, LocalDate.of(1926, 12, 25));

    /**

     * The singleton instance for the 'Heisei' era (1989-01-08 - current)

     * which has the value 2.

     */

    public static final JapaneseEra HEISEI = new JapaneseEra(2, LocalDate.of(1989, 1, 8));

    // the number of defined JapaneseEra constants.

    // There could be an extra era defined in its configuration.

    private static final int N_ERA_CONSTANTS = HEISEI.getValue() + ERA_OFFSET + 1;

    /**

     * Serialization version.

     */

    private static final long serialVersionUID = 1466499369062886794L;

    // array for the singleton JapaneseEra instances

    private static final JapaneseEra[] KNOWN_ERAS;

    static {

        sun.util.calendar.Era[] sunEras = JapaneseChronology.JCAL.getEras();

        ERA_CONFIG = new sun.util.calendar.Era[sunEras.length + 1];

        for (int i = 1; i < ERA_CONFIG.length; i++) {

            ERA_CONFIG[i] = sunEras[i - 1];

        }

        KNOWN_ERAS = new JapaneseEra[ERA_CONFIG.length];

        KNOWN_ERAS[0] = SEIREKI;

        KNOWN_ERAS[1] = MEIJI;

        KNOWN_ERAS[2] = TAISHO;

        KNOWN_ERAS[3] = SHOWA;

        KNOWN_ERAS[4] = HEISEI;

        for (int i = N_ERA_CONSTANTS; i < ERA_CONFIG.length; i++) {

            CalendarDate date = ERA_CONFIG[i].getSinceDate();

            LocalDate isoDate = LocalDate.of(date.getYear(), date.getMonth(), date.getDayOfMonth());

            KNOWN_ERAS[i] = new JapaneseEra(i - ERA_OFFSET, isoDate);

        }

    };

    /**

     * The era value.

     * @serial

     */

    private final int eraValue;

    // the first day of the era

    private final transient LocalDate since;

    /**

     * Creates an instance.

     *

     * @param eraValue  the era value, validated

     * @param since  the date representing the first date of the era, validated not null

     */

    private JapaneseEra(int eraValue, LocalDate since) {

        this.eraValue = eraValue;

        this.since = since;

    }

    /**

     * Returns the singleton {@code JapaneseEra} corresponding to this object.

     * It's possible that this version of {@code JapaneseEra} doesn't support the latest era value.

     * In that case, this method throws an {@code ObjectStreamException}.

     *

     * @return the singleton {@code JapaneseEra} for this object

     * @throws ObjectStreamException if the deserialized object has any unknown numeric era value.

     */

    private Object readResolve() throws ObjectStreamException {

        try {

            return of(eraValue);

        } catch (DateTimeException e) {

            InvalidObjectException ex = new InvalidObjectException("Invalid era");

            ex.initCause(e);

            throw ex;

        }

    }

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

    /**

     * Returns the Sun private Era instance corresponding to this {@code JapaneseEra}.

     * SEIREKI doesn't have its corresponding one.

     *

     * @return the Sun private Era instance for this {@code JapaneseEra},

     *         or null for SEIREKI.

     */

    sun.util.calendar.Era getPrivateEra() {

        return ERA_CONFIG[ordinal(eraValue)];

    }

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

    /**

     * Obtains an instance of {@code JapaneseEra} from an {@code int} value.

     * <p>

     * The {@link #SHOWA} era that contains 1970-01-01 (ISO calendar system) has the value 1

     * Later era is numbered 2 ({@link #HEISEI}). Earlier eras are numbered 0 ({@link #TAISHO}),

     * -1 ({@link #MEIJI}), only Meiji and later eras are supported. The prior to Meiji,

     * {@link #SEIREKI} is used.

     *

     * @param japaneseEra  the era to represent

     * @return the {@code JapaneseEra} singleton, not null

     * @throws DateTimeException if the value is invalid

     */

    public static JapaneseEra of(int japaneseEra) {

        if (japaneseEra != SEIREKI.eraValue &&

            (japaneseEra < MEIJI.eraValue || japaneseEra > HEISEI.eraValue)) {

            throw new DateTimeException("Invalid era: " + japaneseEra);

        }

        return KNOWN_ERAS[ordinal(japaneseEra)];

    }

    /**

     * Returns the {@code JapaneseEra} with the name.

     * <p>

     * The string must match exactly the name of the era.

     * (Extraneous whitespace characters are not permitted.)

     *

     * @param japaneseEra  the japaneseEra name; non-null

     * @return the {@code JapaneseEra} singleton, never null

     * @throws IllegalArgumentException if there is not JapaneseEra with the specified name

     */

    public static JapaneseEra valueOf(String japaneseEra) {

        Objects.requireNonNull(japaneseEra, "japaneseEra");

        for (JapaneseEra era : KNOWN_ERAS) {

            if (era.getName().equals(japaneseEra)) {

                return era;

            }

        }

        throw new IllegalArgumentException("japaneseEra is invalid");

    }

    /**

     * Returns an array of JapaneseEras.

     * <p>

     * This method may be used to iterate over the JapaneseEras as follows:

     * <pre>

     * for (JapaneseEra c : JapaneseEra.values())

     *     System.out.println(c);

     * </pre>

     *

     * @return an array of JapaneseEras

     */

    public static JapaneseEra[] values() {

        return Arrays.copyOf(KNOWN_ERAS, KNOWN_ERAS.length);

    }

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

    /**

     * Obtains an instance of {@code JapaneseEra} from a date.

     *

     * @param date  the date, not null

     * @return the Era singleton, never null

     */

    static JapaneseEra from(LocalDate date) {

        for (int i = KNOWN_ERAS.length - 1; i > 0; i--) {

            JapaneseEra era = KNOWN_ERAS[i];

            if (date.compareTo(era.since) >= 0) {

                return era;

            }

        }

        return SEIREKI;

    }

    static JapaneseEra toJapaneseEra(sun.util.calendar.Era privateEra) {

        for (int i = ERA_CONFIG.length - 1; i > 0; i--) {

            if (ERA_CONFIG[i].equals(privateEra)) {

                return KNOWN_ERAS[i];

            }

        }

        return SEIREKI;

    }

    static sun.util.calendar.Era privateEraFrom(LocalDate isoDate) {

        for (int i = KNOWN_ERAS.length - 1; i > 0; i--) {

            JapaneseEra era = KNOWN_ERAS[i];

            if (isoDate.compareTo(era.since) >= 0) {

                return ERA_CONFIG[i];

            }

        }

        return null;

    }

    /**

     * Returns the index into the arrays from the Era value.

     * the eraValue is a valid Era number, -999, -1..2.

     *

     * @param eraValue  the era value to convert to the index

     * @return the index of the current Era

     */

    private static int ordinal(int eraValue) {

        return (eraValue == SEIREKI.eraValue) ? 0 : eraValue + ERA_OFFSET;

    }

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

    /**

     * Gets the numeric era {@code int} value.

     * <p>

     * The {@link #SHOWA} era that contains 1970-01-01 (ISO calendar system) has the value 1.

     * Later eras are numbered from 2 ({@link #HEISEI}).

     * Earlier eras are numbered 0 ({@link #TAISHO}), -1 ({@link #MEIJI}), and -999 ({@link #SEIREKI}).

     *

     * @return the era value

     */

    @Override

    public int getValue() {

        return eraValue;

    }

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

    /**

     * Gets the range of valid values for the specified field.

     * <p>

     * The range object expresses the minimum and maximum valid values for a field.

     * This era is used to enhance the accuracy of the returned range.

     * If it is not possible to return the range, because the field is not supported

     * or for some other reason, an exception is thrown.

     * <p>

     * If the field is a {@link ChronoField} then the query is implemented here.

     * The {@code ERA} field returns the range.

     * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}.

     * <p>

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

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

     * passing {@code this} as the argument.

     * Whether the range can be obtained is determined by the field.

     * <p>

     * The range of valid Japanese eras can change over time due to the nature

     * of the Japanese calendar system.

     *

     * @param field  the field to query the range for, not null

     * @return the range of valid values for the field, not null

     * @throws DateTimeException if the range for the field cannot be obtained

     * @throws UnsupportedTemporalTypeException if the unit is not supported

     */

    @Override  // override as super would return range from 0 to 1

    public ValueRange range(TemporalField field) {

        if (field == ERA) {

            return JapaneseChronology.INSTANCE.range(ERA);

        }

        return Era.super.range(field);

    }

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

    String getAbbreviation() {

        int index = ordinal(getValue());

        if (index == 0) {

            return "";

        }

        return ERA_CONFIG[index].getAbbreviation();

    }

    String getName() {

        int index = ordinal(getValue());

        if (index == 0) {

            return "Seireki";

        }

        return ERA_CONFIG[index].getName();

    }

    @Override

    public String toString() {

        return getName();

    }

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

    private Object writeReplace() {

        return new Ser(Ser.JAPANESE_ERA_TYPE, this);

    }

    void writeExternal(DataOutput out) throws IOException {

        out.writeByte(this.getValue());

    }

    static JapaneseEra readExternal(DataInput in) throws IOException {

        byte eraValue = in.readByte();

        return JapaneseEra.of(eraValue);

    }

}