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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) 2007-2012, Stephen Colebourne & Michael Nascimento Santos

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package java.time.temporal;

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

import java.time.ZoneId;

import java.time.ZoneOffset;

/**

 * Common implementations of {@code TemporalQuery}.

 * <p>

 * This class provides common implementations of {@link TemporalQuery}.

 * These queries are primarily used as optimizations, allowing the internals

 * of other objects to be extracted effectively. Note that application code

 * can also use the {@code from(TemporalAccessor)} method on most temporal

 * objects as a method reference matching the query interface, such as

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

 * <p>

 * There are two equivalent ways of using a {@code TemporalQuery}.

 * The first is to invoke the method on the interface directly.

 * The second is to use {@link TemporalAccessor#query(TemporalQuery)}:

 * <pre>

 *   // these two lines are equivalent, but the second approach is recommended

 *   dateTime = query.queryFrom(dateTime);

 *   dateTime = dateTime.query(query);

 * </pre>

 * It is recommended to use the second approach, {@code query(TemporalQuery)},

 * as it is a lot clearer to read in code.

 *

 * <h3>Specification for implementors</h3>

 * This is a thread-safe utility class.

 * All returned adjusters are immutable and thread-safe.

 *

 * @since 1.8

 */

public final class Queries {

    // note that it is vital that each method supplies a constant, not a

    // calculated value, as they will be checked for using ==

    // it is also vital that each constant is different (due to the == checking)

    // as such, alterations to use lambdas must be done with extreme care

    /**

     * Private constructor since this is a utility class.

     */

    private Queries() {

    }

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

    // special constants should be used to extract information from a TemporalAccessor

    // that cannot be derived in other ways

    // Javadoc added here, so as to pretend they are more normal than they really are

    /**

     * A strict query for the {@code ZoneId}.

     * <p>

     * This queries a {@code TemporalAccessor} for the zone.

     * The zone is only returned if the date-time conceptually contains a {@code ZoneId}.

     * It will not be returned if the date-time only conceptually has an {@code ZoneOffset}.

     * <p>

     * In most cases, applications should use {@link #ZONE} as this query is too strict.

     * <p>

     * The result from JDK classes implementing {@code TemporalAccessor} is as follows:<br>

     * {@code LocalDate} returns null<br>

     * {@code LocalTime} returns null<br>

     * {@code LocalDateTime} returns null<br>

     * {@code ZonedDateTime} returns the associated zone<br>

     * {@code OffsetTime} returns null<br>

     * {@code OffsetDateTime} returns null<br>

     * {@code ChronoLocalDate} returns null<br>

     * {@code ChronoLocalDateTime} returns null<br>

     * {@code ChronoZonedDateTime} returns the associated zone<br>

     * {@code Era} returns null<br>

     * {@code DayOfWeek} returns null<br>

     * {@code Month} returns null<br>

     * {@code Year} returns null<br>

     * {@code YearMonth} returns null<br>

     * {@code MonthDay} returns null<br>

     * {@code ZoneOffset} returns null<br>

     * {@code Instant} returns null<br>

     */

    public static final TemporalQuery<ZoneId> zoneId() {

        return ZONE_ID;

    }

    };

    /**

     * <p>

     * This queries a {@code TemporalAccessor} for the chronology.

     * If the target {@code TemporalAccessor} represents a date, or part of a date,

     * then it should return the chronology that the date is expressed in.

     * As a result of this definition, objects only representing time, such as

     * {@code LocalTime}, will return null.

     * <p>

     * The result from JDK classes implementing {@code TemporalAccessor} is as follows:<br>

     * {@code LocalTime} returns null (does not represent a date)<br>

     * {@code OffsetTime} returns null (does not represent a date)<br>

     * {@code ChronoLocalDate} returns the associated chronology<br>

     * {@code ChronoLocalDateTime} returns the associated chronology<br>

     * {@code ChronoZonedDateTime} returns the associated chronology<br>

     * {@code Era} returns the associated chronology<br>

     * {@code DayOfWeek} returns null (shared across chronologies)<br>

     * {@code ZoneOffset} returns null (does not represent a date)<br>

     * {@code Instant} returns null (does not represent a date)<br>

     * <p>

     * That method is equivalent to this query, except that it throws an

     * exception if a chronology cannot be obtained.

     */

        return CHRONO;

    }

    };

    /**

     * A query for the smallest supported unit.

     * <p>

     * This queries a {@code TemporalAccessor} for the time precision.

     * If the target {@code TemporalAccessor} represents a consistent or complete date-time,

     * date or time then this must return the smallest precision actually supported.

     * Note that fields such as {@code NANO_OF_DAY} and {@code NANO_OF_SECOND}

     * are defined to always return ignoring the precision, thus this is the only

     * way to find the actual smallest supported unit.

     * For example, were {@code GregorianCalendar} to implement {@code TemporalAccessor}

     * it would return a precision of {@code MILLIS}.

     * <p>

     * The result from JDK classes implementing {@code TemporalAccessor} is as follows:<br>

     * {@code LocalDate} returns {@code DAYS}<br>

     * {@code LocalTime} returns {@code NANOS}<br>

     * {@code LocalDateTime} returns {@code NANOS}<br>

     * {@code ZonedDateTime} returns {@code NANOS}<br>

     * {@code OffsetTime} returns {@code NANOS}<br>

     * {@code OffsetDateTime} returns {@code NANOS}<br>

     * {@code ChronoLocalDate} returns {@code DAYS}<br>

     * {@code ChronoLocalDateTime} returns {@code NANOS}<br>

     * {@code ChronoZonedDateTime} returns {@code NANOS}<br>

     * {@code Era} returns {@code ERAS}<br>

     * {@code DayOfWeek} returns {@code DAYS}<br>

     * {@code Month} returns {@code MONTHS}<br>

     * {@code Year} returns {@code YEARS}<br>

     * {@code YearMonth} returns {@code MONTHS}<br>

     * {@code MonthDay} returns null (does not represent a complete date or time)<br>

     * {@code ZoneOffset} returns null (does not represent a date or time)<br>

     * {@code Instant} returns {@code NANOS}<br>

     */

        return PRECISION;

    }

    };

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

    // non-special constants are standard queries that derive information from other information

    /**

     * A lenient query for the {@code ZoneId}, falling back to the {@code ZoneOffset}.

     * <p>

     * This queries a {@code TemporalAccessor} for the zone.

     * It first tries to obtain the zone, using {@link #zoneId()}.

     * If that is not found it tries to obtain the {@link #offset()}.

     * <p>

     * In most cases, applications should use this query rather than {@code #zoneId()}.

     * <p>

     * The method {@link ZoneId#from(TemporalAccessor)} can be used as a

     * {@code TemporalQuery} via a method reference, {@code ZoneId::from}.

     * That method is equivalent to this query, except that it throws an

     * exception if a zone cannot be obtained.

     */

    public static final TemporalQuery<ZoneId> zone() {

        return ZONE;

    }

    };

    /**

     * <p>

     * <p>

     * field and uses it to create a {@code ZoneOffset}.

     * <p>

     * The method {@link ZoneOffset#from(TemporalAccessor)} can be used as a

     * {@code TemporalQuery} via a method reference, {@code ZoneOffset::from}.

     */

    public static final TemporalQuery<ZoneOffset> offset() {

        return OFFSET;

    }

        }

    };

}