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	/*
	* Copyright (c) 2012, 2019, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	/*
	* 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.
	*
	* * Redistributions in binary form must reproduce the above copyright notice,
	* this list of conditions and the following disclaimer in the documentation
	* and/or other materials provided with the distribution.
	*
	* * Neither the name of JSR-310 nor the names of its contributors
	* may be used to endorse or promote products derived from this software
	* without specific prior written permission.
	*
	* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
	* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
	* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
	* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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	* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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	* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/
	package java.time.chrono;

	import static java.time.chrono.JapaneseDate.MEIJI_6_ISODATE;
	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.ObjectInputStream;
	import java.io.ObjectStreamException;
	import java.io.Serializable;
	import java.time.DateTimeException;
	import java.time.LocalDate;
	import java.time.format.DateTimeFormatterBuilder;
	import java.time.format.TextStyle;
	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.Locale;
	import java.util.Objects;

	import sun.util.calendar.CalendarDate;

	/**
	* An era in the Japanese Imperial calendar system.
	* <p>
	* The Japanese government defines the official name and start date of
	* each era. Eras are consecutive and their date ranges do not overlap,
	* so the end date of one era is always the day before the start date
	* of the next era.
	* <p>
	* The Java SE Platform supports all eras defined by the Japanese government,
	* beginning with the Meiji era. Each era is identified in the Platform by an
	* integer value and a name. The {@link #of(int)} and {@link #valueOf(String)}
	* methods may be used to obtain a singleton instance of JapaneseEra for each
	* era. The {@link #values()} method returns the singleton instances of all
	* supported eras.
	* <p>
	* For convenience, this class declares a number of public static final fields
	* that refer to singleton instances returned by the values() method.
	*
	* @apiNote
	* The fields declared in this class may evolve over time, in line with the
	* results of the {@link #values()} method. However, there is not necessarily
	* a 1:1 correspondence between the fields and the singleton instances.
	*
	* @apiNote
	* The Japanese government may announce a new era and define its start
	* date but not its official name. In this scenario, the singleton instance
	* that represents the new era may return a name that is not stable until
	* the official name is defined. Developers should exercise caution when
	* relying on the name returned by any singleton instance that does not
	* correspond to a public static final field.
	*
	* @implSpec
	* 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
	static final int ERA_OFFSET = 2;

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

	/**
	* The singleton instance for the 'Meiji' era (1868-01-01 - 1912-07-29)
	* which has the value -1.
	*/
	public static final JapaneseEra MEIJI = new JapaneseEra(-1, LocalDate.of(1868, 1, 1));
	/**
	* 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 - 2019-04-30)
	* which has the value 2.
	*/
	public static final JapaneseEra HEISEI = new JapaneseEra(2, LocalDate.of(1989, 1, 8));
	/**
	* The singleton instance for the 'Reiwa' era (2019-05-01 - )
	* which has the value 3.
	*/
	private static final JapaneseEra REIWA = new JapaneseEra(3, LocalDate.of(2019, 5, 1));

	// The number of predefined JapaneseEra constants.
	// There may be a supplemental era defined by the property.
	private static final int N_ERA_CONSTANTS = REIWA.getValue() + ERA_OFFSET;

	/**
	* Serialization version.
	*/
	private static final long serialVersionUID = 1466499369062886794L;

	// array for the singleton JapaneseEra instances
	private static final JapaneseEra[] KNOWN_ERAS;

	static {
	ERA_CONFIG = JapaneseChronology.JCAL.getEras();

	KNOWN_ERAS = new JapaneseEra[ERA_CONFIG.length];
	KNOWN_ERAS[0] = MEIJI;
	KNOWN_ERAS[1] = TAISHO;
	KNOWN_ERAS[2] = SHOWA;
	KNOWN_ERAS[3] = HEISEI;
	KNOWN_ERAS[4] = REIWA;
	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 + 1, isoDate);
	}
	};

	/**
	* The era value.
	* @serial
	*/
	private final transient 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 Sun private Era instance corresponding to this {@code JapaneseEra}.
	*
	* @return the Sun private Era instance for this {@code JapaneseEra}.
	*/
	sun.util.calendar.Era getPrivateEra() {
	return ERA_CONFIG[ordinal(eraValue)];
	}

	//-----------------------------------------------------------------------
	/**
	* Obtains an instance of {@code JapaneseEra} from an {@code int} value.
	* <ul>
	* <li>The value {@code 1} is associated with the 'Showa' era, because
	* it contains 1970-01-01 (ISO calendar system).</li>
	* <li>The values {@code -1} and {@code 0} are associated with two earlier
	* eras, Meiji and Taisho, respectively.</li>
	* <li>A value greater than {@code 1} is associated with a later era,
	* beginning with Heisei ({@code 2}).</li>
	* </ul>
	* <p>
	* Every instance of {@code JapaneseEra} that is returned from the {@link values()}
	* method has an int value (available via {@link Era#getValue()} which is
	* accepted by this method.
	*
	* @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 < MEIJI.eraValue \|\| japaneseEra + ERA_OFFSET > KNOWN_ERAS.length) {
	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);
	}

	/**
	* {@inheritDoc}
	*
	* @param style {@inheritDoc}
	* @param locale {@inheritDoc}
	*/
	@Override
	public String getDisplayName(TextStyle style, Locale locale) {
	// If this JapaneseEra is a supplemental one, obtain the name from
	// the era definition.
	if (getValue() > N_ERA_CONSTANTS - ERA_OFFSET) {
	Objects.requireNonNull(locale, "locale");
	return style.asNormal() == TextStyle.NARROW ? getAbbreviation() : getName();
	}

	return new DateTimeFormatterBuilder()
	.appendText(ERA, style)
	.toFormatter(locale)
	.withChronology(JapaneseChronology.INSTANCE)
	.format(this == MEIJI ? MEIJI_6_ISODATE : since);
	}

	//-----------------------------------------------------------------------
	/**
	* 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) {
	if (date.isBefore(MEIJI_6_ISODATE)) {
	throw new DateTimeException("JapaneseDate before Meiji 6 are not supported");
	}
	for (int i = KNOWN_ERAS.length - 1; i > 0; i--) {
	JapaneseEra era = KNOWN_ERAS[i];
	if (date.compareTo(era.since) >= 0) {
	return era;
	}
	}
	return null;
	}

	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 null;
	}

	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, -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 + ERA_OFFSET - 1;
	}

	//-----------------------------------------------------------------------
	/**
	* 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})).
	*
	* @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() {
	return ERA_CONFIG[ordinal(getValue())].getAbbreviation();
	}

	String getName() {
	return ERA_CONFIG[ordinal(getValue())].getName();
	}

	@Override
	public String toString() {
	return getName();
	}

	//-----------------------------------------------------------------------
	/**
	* Defend against malicious streams.
	*
	* @param s the stream to read
	* @throws InvalidObjectException always
	*/
	private void readObject(ObjectInputStream s) throws InvalidObjectException {
	throw new InvalidObjectException("Deserialization via serialization delegate");
	}

	//-----------------------------------------------------------------------
	/**
	* Writes the object using a
	* <a href="../../../serialized-form.html#java.time.chrono.Ser">dedicated serialized form</a>.
	* @serialData
	* <pre>
	* out.writeByte(5); // identifies a JapaneseEra
	* out.writeInt(getValue());
	* </pre>
	*
	* @return the instance of {@code Ser}, not null
	*/
	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);
	}

	}

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