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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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 * All rights reserved.

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package java.time.temporal;

import java.time.DateTimeException;

import java.util.Objects;

/**

 * Framework-level interface defining read-only access to a temporal object,

 * such as a date, time, offset or some combination of these.

 * <p>

 * This is the base interface type for date, time and offset objects.

 * It is implemented by those classes that can provide information

 * as {@linkplain TemporalField fields} or {@linkplain TemporalQuery queries}.

 * <p>

 * Most date and time information can be represented as a number.

 * These are modeled using {@code TemporalField} with the number held using

 * a {@code long} to handle large values. Year, month and day-of-month are

 * simple examples of fields, but they also include instant and offsets.

 * See {@link ChronoField} for the standard set of fields.

 * <p>

 * Two pieces of date/time information cannot be represented by numbers,

 * the {@linkplain java.time.chrono.Chronology chronology} and the

 * {@linkplain java.time.ZoneId time-zone}.

 * These can be accessed via {@linkplain #query(TemporalQuery) queries} using

 * the static methods defined on {@link TemporalQuery}.

 * <p>

 * A sub-interface, {@link Temporal}, extends this definition to one that also

 * supports adjustment and manipulation on more complete temporal objects.

 * <p>

 * This interface is a framework-level interface that should not be widely

 * used in application code. Instead, applications should create and pass

 * around instances of concrete types, such as {@code LocalDate}.

 * There are many reasons for this, part of which is that implementations

 * of this interface may be in calendar systems other than ISO.

 * See {@link java.time.chrono.ChronoLocalDate} for a fuller discussion of the issues.

 *

 * @implSpec

 * This interface places no restrictions on the mutability of implementations,

 * however immutability is strongly recommended.

 *

 * @since 1.8

 */

public interface TemporalAccessor {

    /**

     * Checks if the specified field is supported.

     * <p>

     * This checks if the date-time 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.

     *

     * @implSpec

     * Implementations must check and handle all fields defined in {@link ChronoField}.

     * If the field is supported, then true must be returned, otherwise false must be returned.

     * <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.

     * <p>

     * Implementations must ensure that no observable state is altered when this

     * read-only method is invoked.

     *

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

     * @return true if this date-time can be queried for the field, false if not

     */

    boolean isSupported(TemporalField field);

    /**

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

     * <p>

     * All fields can be expressed as a {@code long} integer.

     * This method returns an object that describes the valid range for that value.

     * The value of this temporal object is used to enhance the accuracy of the returned range.

     * If the date-time cannot return the range, because the field is unsupported or for

     * some other reason, an exception will be thrown.

     * <p>

     * Note that the result only describes the minimum and maximum valid values

     * and it is important not to read too much into them. For example, there

     * could be values within the range that are invalid for the field.

     *

     * @implSpec

     * Implementations must check and handle all fields defined in {@link ChronoField}.

     * If the field is supported, then the range of the field must be returned.

     * If unsupported, then an {@code UnsupportedTemporalTypeException} must be thrown.

     * <p>

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

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

     * passing {@code this} as the argument.

     * <p>

     * Implementations must ensure that no observable state is altered when this

     * read-only method is invoked.

     * <p>

     * The default implementation must behave equivalent to this code:

     * <pre>

     *  if (field instanceof ChronoField) {

     *    if (isSupported(field)) {

     *      return field.range();

     *    }

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

     *  }

     *  return field.rangeRefinedBy(this);

     * </pre>

     *

     * @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 field is not supported

     */

    default ValueRange range(TemporalField field) {

        if (field instanceof ChronoField) {

            if (isSupported(field)) {

                return field.range();

            }

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

        }

        Objects.requireNonNull(field, "field");

        return field.rangeRefinedBy(this);

    }

    /**

     * Gets the value of the specified field as an {@code int}.

     * <p>

     * This queries the date-time for the value for the specified field.

     * The returned value will always be within the valid range of values for the field.

     * If the date-time cannot return the value, because the field is unsupported or for

     * some other reason, an exception will be thrown.

     *

     * @implSpec

     * Implementations must check and handle all fields defined in {@link ChronoField}.

     * If the field is supported and has an {@code int} range, then the value of

     * the field must be returned.

     * If unsupported, then an {@code UnsupportedTemporalTypeException} must be thrown.

     * <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.

     * <p>

     * Implementations must ensure that no observable state is altered when this

     * read-only method is invoked.

     * <p>

     * The default implementation must behave equivalent to this code:

     * <pre>

     *  if (range(field).isIntValue()) {

     *    return range(field).checkValidIntValue(getLong(field), field);

     *  }

     *  throw new UnsupportedTemporalTypeException("Invalid field " + field + " + for get() method, use getLong() instead");

     * </pre>

     *

     * @param field  the field to get, not null

     * @return the value for the field, within the valid range of values

     * @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

     */

    default int get(TemporalField field) {

        ValueRange range = range(field);

        if (range.isIntValue() == false) {

            throw new UnsupportedTemporalTypeException("Invalid field " + field + " + for get() method, use getLong() instead");

        }

        long value = getLong(field);

        if (range.isValidValue(value) == false) {

            throw new DateTimeException("Invalid value for " + field + " (valid values " + range + "): " + value);

        }

        return (int) value;

    }

    /**

     * Gets the value of the specified field as a {@code long}.

     * <p>

     * This queries the date-time for the value for the specified field.

     * The returned value may be outside the valid range of values for the field.

     * If the date-time cannot return the value, because the field is unsupported or for

     * some other reason, an exception will be thrown.

     *

     * @implSpec

     * Implementations must check and handle all fields defined in {@link ChronoField}.

     * If the field is supported, then the value of the field must be returned.

     * If unsupported, then an {@code UnsupportedTemporalTypeException} must be thrown.

     * <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.

     * <p>

     * Implementations must ensure that no observable state is altered when this

     * read-only method is invoked.

     *

     * @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

     */

    long getLong(TemporalField field);

    /**

     * Queries this date-time.

     * <p>

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

     * <p>

     * Queries are a key tool for extracting information from date-times.

     * They exists to externalize the process of querying, permitting different

     * approaches, as per the strategy design pattern.

     * Examples might be a query that checks if the date is the day before February 29th

     * in a leap year, or calculates the number of days to your next birthday.

     * <p>

     * The most common query implementations are method references, such as

     * {@code LocalDate::from} and {@code ZoneId::from}.

     * Additional implementations are provided as static methods on {@link TemporalQuery}.

     *

     * @implSpec

     * The default implementation must behave equivalent to this code:

     * <pre>

     *  if (query == TemporalQueries.zoneId() ||

     *        query == TemporalQueries.chronology() || query == TemporalQueries.precision()) {

     *    return null;

     *  }

     *  return query.queryFrom(this);

     * </pre>

     * Future versions are permitted to add further queries to the if statement.

     * <p>

     * All classes implementing this interface and overriding this method must call

     * {@code TemporalAccessor.super.query(query)}. JDK classes may avoid calling

     * super if they provide behavior equivalent to the default behaviour, however

     * non-JDK classes may not utilize this optimization and must call {@code super}.

     * <p>

     * If the implementation can supply a value for one of the queries listed in the

     * if statement of the default implementation, then it must do so.

     * For example, an application-defined {@code HourMin} class storing the hour

     * and minute must override this method as follows:

     * <pre>

     *  if (query == TemporalQueries.precision()) {

     *    return MINUTES;

     *  }

     *  return TemporalAccessor.super.query(query);

     * </pre>

     * <p>

     * Implementations must ensure that no observable state is altered when this

     * read-only method is invoked.

     *

     * @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

     * @throws ArithmeticException if numeric overflow occurs

     */

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

        if (query == TemporalQueries.zoneId()

                || query == TemporalQueries.chronology()

                || query == TemporalQueries.precision()) {

            return null;

        }

        return query.queryFrom(this);

    }

}