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	/*
	* Copyright (c) 2012, 2017, 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
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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.
	*
	* * 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,
	* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
	* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
	* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
	* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
	* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
	* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/
	package java.time.chrono;

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

	import java.time.DateTimeException;
	import java.time.temporal.UnsupportedTemporalTypeException;
	import java.time.format.DateTimeFormatterBuilder;
	import java.time.format.TextStyle;
	import java.time.temporal.ChronoField;
	import java.time.temporal.Temporal;
	import java.time.temporal.TemporalAccessor;
	import java.time.temporal.TemporalAdjuster;
	import java.time.temporal.TemporalField;
	import java.time.temporal.TemporalQueries;
	import java.time.temporal.TemporalQuery;
	import java.time.temporal.ValueRange;
	import java.util.Locale;

	/**
	* An era of the time-line.
	* <p>
	* Most calendar systems have a single epoch dividing the time-line into two eras.
	* However, some calendar systems, have multiple eras, such as one for the reign
	* of each leader.
	* In all cases, the era is conceptually the largest division of the time-line.
	* Each chronology defines the Era's that are known Eras and a
	* {@link Chronology#eras Chronology.eras} to get the valid eras.
	* <p>
	* For example, the Thai Buddhist calendar system divides time into two eras,
	* before and after a single date. By contrast, the Japanese calendar system
	* has one era for the reign of each Emperor.
	* <p>
	* Instances of {@code Era} may be compared using the {@code ==} operator.
	*
	* @implSpec
	* This interface must be implemented with care to ensure other classes operate correctly.
	* All implementations must be singletons - final, immutable and thread-safe.
	* It is recommended to use an enum whenever possible.
	*
	* @since 1.8
	*/
	public interface Era extends TemporalAccessor, TemporalAdjuster {

	/**
	* Gets the numeric value associated with the era as defined by the chronology.
	* Each chronology defines the predefined Eras and methods to list the Eras
	* of the chronology.
	* <p>
	* All fields, including eras, have an associated numeric value.
	* The meaning of the numeric value for era is determined by the chronology
	* according to these principles:
	* <ul>
	* <li>The era in use at the epoch 1970-01-01 (ISO) has the value 1.
	* <li>Later eras have sequentially higher values.
	* <li>Earlier eras have sequentially lower values, which may be negative.
	* </ul>
	*
	* @return the numeric era value
	*/
	int getValue();

	//-----------------------------------------------------------------------
	/**
	* Checks if the specified field is supported.
	* <p>
	* This checks if this era can be queried for the specified field.
	* If false, then calling the {@link #range(TemporalField) range} and
	* {@link #get(TemporalField) get} methods will throw an exception.
	* <p>
	* If the field is a {@link ChronoField} then the query is implemented here.
	* The {@code ERA} field returns true.
	* All other {@code ChronoField} instances will return false.
	* <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 is supported on this era, false if not
	*/
	@Override
	default boolean isSupported(TemporalField field) {
	if (field instanceof ChronoField) {
	return field == ERA;
	}
	return field != null && field.isSupportedBy(this);
	}

	/**
	* 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 default implementation must return a range for {@code ERA} from
	* zero to one, suitable for two era calendar systems such as ISO.
	*
	* @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 for Javadoc
	default ValueRange range(TemporalField field) {
	return TemporalAccessor.super.range(field);
	}

	/**
	* Gets the value of the specified field from this era as an {@code int}.
	* <p>
	* This queries this era for the value of the specified field.
	* The returned value will always be within the valid range of values for the field.
	* If it is not possible to return the value, 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 value of the era.
	* 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.getFrom(TemporalAccessor)}
	* passing {@code this} as the argument. Whether the value can be obtained,
	* and what the value represents, is determined by the field.
	*
	* @param field the field to get, not null
	* @return the value for the field
	* @throws DateTimeException if a value for the field cannot be obtained or
	* the value is outside the range of valid values for the field
	* @throws UnsupportedTemporalTypeException if the field is not supported or
	* the range of values exceeds an {@code int}
	* @throws ArithmeticException if numeric overflow occurs
	*/
	@Override // override for Javadoc and performance
	default int get(TemporalField field) {
	if (field == ERA) {
	return getValue();
	}
	return TemporalAccessor.super.get(field);
	}

	/**
	* Gets the value of the specified field from this era as a {@code long}.
	* <p>
	* This queries this era for the value of the specified field.
	* If it is not possible to return the value, 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 value of the era.
	* 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.getFrom(TemporalAccessor)}
	* passing {@code this} as the argument. Whether the value can be obtained,
	* and what the value represents, is determined by the field.
	*
	* @param field the field to get, not null
	* @return the value for the field
	* @throws DateTimeException if a value for the field cannot be obtained
	* @throws UnsupportedTemporalTypeException if the field is not supported
	* @throws ArithmeticException if numeric overflow occurs
	*/
	@Override
	default long getLong(TemporalField field) {
	if (field == ERA) {
	return getValue();
	} else if (field instanceof ChronoField) {
	throw new UnsupportedTemporalTypeException("Unsupported field: " + field);
	}
	return field.getFrom(this);
	}

	//-----------------------------------------------------------------------
	/**
	* Queries this era using the specified query.
	* <p>
	* This queries this era 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.precision()) {
	return (R) ERAS;
	}
	return TemporalAccessor.super.query(query);
	}

	/**
	* Adjusts the specified temporal object to have the same era as this object.
	* <p>
	* This returns a temporal object of the same observable type as the input
	* with the era changed to be the same as this.
	* <p>
	* The adjustment is equivalent to using {@link Temporal#with(TemporalField, long)}
	* passing {@link ChronoField#ERA} as the field.
	* <p>
	* In most cases, it is clearer to reverse the calling pattern by using
	* {@link Temporal#with(TemporalAdjuster)}:
	* <pre>
	* // these two lines are equivalent, but the second approach is recommended
	* temporal = thisEra.adjustInto(temporal);
	* temporal = temporal.with(thisEra);
	* </pre>
	* <p>
	* This instance is immutable and unaffected by this method call.
	*
	* @param temporal the target object to be adjusted, not null
	* @return the adjusted object, not null
	* @throws DateTimeException if unable to make the adjustment
	* @throws ArithmeticException if numeric overflow occurs
	*/
	@Override
	default Temporal adjustInto(Temporal temporal) {
	return temporal.with(ERA, getValue());
	}

	//-----------------------------------------------------------------------
	/**
	* Gets the textual representation of this era.
	* <p>
	* This returns the textual name used to identify the era,
	* suitable for presentation to the user.
	* The parameters control the style of the returned text and the locale.
	* <p>
	* If no textual mapping is found then the {@link #getValue() numeric value} is returned.
	*
	* @apiNote This default implementation is suitable for most implementations.
	*
	* @param style the style of the text required, not null
	* @param locale the locale to use, not null
	* @return the text value of the era, not null
	*/
	default String getDisplayName(TextStyle style, Locale locale) {
	return new DateTimeFormatterBuilder().appendText(ERA, style).toFormatter(locale).format(this);
	}

	// NOTE: methods to convert year-of-era/proleptic-year cannot be here as they may depend on month/day (Japanese)
	}

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