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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.
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 * file:
 *
 * Copyright (c) 2012, Stephen Colebourne & Michael Nascimento Santos
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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.

 This is the base interface type for date, time and offset objects. It is implemented by those classes that can provide information as fields or queries. 
 Most date and time information can be represented as a number. These are modeled using TemporalField with the number held using a long to handle large values. Year, month and day-of-month are simple examples of fields, but they also include instant and offsets. See ChronoField for the standard set of fields. 
 Two pieces of date/time information cannot be represented by numbers, the chronology and the time-zone. These can be accessed via queries using the static methods defined on TemporalQuery. 
 A sub-interface, Temporal, extends this definition to one that also supports adjustment and manipulation on more complete temporal objects. 
 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 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 ChronoLocalDate for a fuller discussion of the issues. 
Implementation Requirements:
This interface places no restrictions on the mutability of implementations,
however immutability is strongly recommended.
Since:1.8
/**
 * 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.

 This checks if the date-time can be queried for the specified field. If false, then calling the range and get methods will throw an exception. 
Params:
  • field –  the field to check, null returns false
Implementation Requirements: Implementations must check and handle all fields defined in ChronoField. If the field is supported, then true must be returned, otherwise false must be returned. 
 If the field is not a ChronoField, then the result of this method is obtained by invoking TemporalField.isSupportedBy(TemporalAccessor) passing this as the argument. 

Implementations must ensure that no observable state is altered when this
read-only method is invoked.
Returns:true if this date-time can be queried for the field, false if not
/**
     * 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.

 All fields can be expressed as a 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. 

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.

Params:
  • field –  the field to query the range for, not null
Throws:
Implementation Requirements: Implementations must check and handle all fields defined in ChronoField. If the field is supported, then the range of the field must be returned. If unsupported, then an UnsupportedTemporalTypeException must be thrown. 
 If the field is not a ChronoField, then the result of this method is obtained by invoking TemporalField.rangeRefinedBy(TemporalAccessorl) passing this as the argument. 

Implementations must ensure that no observable state is altered when this
read-only method is invoked.


The default implementation must behave equivalent to this code:

 if (field instanceof ChronoField) {
   if (isSupported(field)) {
     return field.range();
   }
   throw new UnsupportedTemporalTypeException("Unsupported field: " + field);
 }
 return field.rangeRefinedBy(this);

Returns:the range of valid values for the field, not null
/**
     * 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 int. 

This queries the date-time for the value of 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.

Params:
  • field –  the field to get, not null
Throws:
Implementation Requirements: Implementations must check and handle all fields defined in ChronoField. If the field is supported and has an int range, then the value of the field must be returned. If unsupported, then an UnsupportedTemporalTypeException must be thrown. 
 If the field is not a ChronoField, then the result of this method is obtained by invoking TemporalField.getFrom(TemporalAccessor) passing this as the argument. 

Implementations must ensure that no observable state is altered when this
read-only method is invoked.


The default implementation must behave equivalent to this code:

 if (range(field).isIntValue()) {
   return range(field).checkValidIntValue(getLong(field), field);
 }
 throw new UnsupportedTemporalTypeException("Invalid field " + field + " + for get() method, use getLong() instead");

Returns:the value for the field, within the valid range of values
/**
     * Gets the value of the specified field as an {@code int}.
     * <p>
     * This queries the date-time for the value of 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 long. 

This queries the date-time for the value of 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.

Params:
  • field –  the field to get, not null
Throws:
Implementation Requirements: Implementations must check and handle all fields defined in ChronoField. If the field is supported, then the value of the field must be returned. If unsupported, then an UnsupportedTemporalTypeException must be thrown. 
 If the field is not a ChronoField, then the result of this method is obtained by invoking TemporalField.getFrom(TemporalAccessor) passing this as the argument. 

Implementations must ensure that no observable state is altered when this
read-only method is invoked.
Returns:the value for the field
/**
     * Gets the value of the specified field as a {@code long}.
     * <p>
     * This queries the date-time for the value of 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.


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


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.

 The most common query implementations are method references, such as LocalDate::from and ZoneId::from. Additional implementations are provided as static methods on TemporalQuery. 
Params:
  • query –  the query to invoke, not null
Type parameters:
  • <R> – the type of the result
Throws:
Implementation Requirements:
The default implementation must behave equivalent to this code:

 if (query == TemporalQueries.zoneId() ||
       query == TemporalQueries.chronology() || query == TemporalQueries.precision()) {
   return null;
 }
 return query.queryFrom(this);


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

 All classes implementing this interface and overriding this method must call 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 super. 
 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 HourMin class storing the hour and minute must override this method as follows: 
 if (query == TemporalQueries.precision()) {
   return MINUTES;
 }
 return TemporalAccessor.super.query(query);




Implementations must ensure that no observable state is altered when this
read-only method is invoked.
Returns:the query result, null may be returned (defined by the query)
/**
     * 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);
    }

}