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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.
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  package java.time.temporal;
  
  import java.time.DateTimeException;
  
  /**
   * Framework-level interface defining read-write 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 that
   * are complete enough to be manipulated using plus and minus.
   * It is implemented by those classes that can provide and manipulate information
   * as {@linkplain TemporalField fields} or {@linkplain TemporalQuery queries}.
   * See {@link TemporalAccessor} for the read-only version of this interface.
   * <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 {@link #query(TemporalQuery) queries} using
   * the static methods defined on {@link TemporalQuery}.
   * <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.
   *
   * <h3>When to implement</h3>
   * <p>
   * A class should implement this interface if it meets three criteria:
   * <ul>
   * <li>it provides access to date/time/offset information, as per {@code TemporalAccessor}
   * <li>the set of fields are contiguous from the largest to the smallest
   * <li>the set of fields are complete, such that no other field is needed to define the
   *  valid range of values for the fields that are represented
   * </ul>
   * <p>
   * Four examples make this clear:
   * <ul>
   * <li>{@code LocalDate} implements this interface as it represents a set of fields
   *  that are contiguous from days to forever and require no external information to determine
   *  the validity of each date. It is therefore able to implement plus/minus correctly.
   * <li>{@code LocalTime} implements this interface as it represents a set of fields
   *  that are contiguous from nanos to within days and require no external information to determine
   *  validity. It is able to implement plus/minus correctly, by wrapping around the day.
   * <li>{@code MonthDay}, the combination of month-of-year and day-of-month, does not implement
   *  this interface.  While the combination is contiguous, from days to months within years,
   *  the combination does not have sufficient information to define the valid range of values
   *  for day-of-month.  As such, it is unable to implement plus/minus correctly.
   * <li>The combination day-of-week and day-of-month ("Friday the 13th") should not implement
   *  this interface. It does not represent a contiguous set of fields, as days to weeks overlaps
   *  days to months.
   * </ul>
   *
   * @implSpec
   * This interface places no restrictions on the mutability of implementations,
   * however immutability is strongly recommended.
   * All implementations must be {@link Comparable}.
   *
   * @since 1.8
   */
  public interface Temporal extends TemporalAccessor {
  
      /**
       * Checks if the specified unit is supported.
       * <p>
       * This checks if the specified unit can be added to, or subtracted from, this date-time.
       * If false, then calling the {@link #plus(long, TemporalUnit)} and
       * {@link #minus(long, TemporalUnit) minus} methods will throw an exception.
       *
       * @implSpec
       * Implementations must check and handle all units defined in {@link ChronoUnit}.
       * If the unit is supported, then true must be returned, otherwise false must be returned.
       * <p>
       * If the field is not a {@code ChronoUnit}, then the result of this method
       * is obtained by invoking {@code TemporalUnit.isSupportedBy(Temporal)}
       * passing {@code this} as the argument.
       * <p>
       * Implementations must ensure that no observable state is altered when this
       * read-only method is invoked.
       *
       * @param unit  the unit to check, null returns false
       * @return true if the unit can be added/subtracted, false if not
       */
      boolean isSupported(TemporalUnit unit);
  
      /**
       * Returns an adjusted object of the same type as this object with the adjustment made.
       * <p>
       * This adjusts this date-time according to the rules of the specified adjuster.
       * A simple adjuster might simply set the one of the fields, such as the year field.
       * A more complex adjuster might set the date to the last day of the month.
       * A selection of common adjustments is provided in
       * {@link TemporalAdjusters TemporalAdjusters}.
       * These include finding the "last day of the month" and "next Wednesday".
       * The adjuster is responsible for handling special cases, such as the varying
       * lengths of month and leap years.
       * <p>
       * Some example code indicating how and why this method is used:
       * <pre>
       *  date = date.with(Month.JULY);        // most key classes implement TemporalAdjuster
       *  date = date.with(lastDayOfMonth());  // static import from Adjusters
       *  date = date.with(next(WEDNESDAY));   // static import from Adjusters and DayOfWeek
       * </pre>
       *
       * @implSpec
       * <p>
       * Implementations must not alter either this object or the specified temporal object.
       * Instead, an adjusted copy of the original must be returned.
       * This provides equivalent, safe behavior for immutable and mutable implementations.
       * <p>
       * The default implementation must behave equivalent to this code:
       * <pre>
       *  return adjuster.adjustInto(this);
       * </pre>
       *
       * @param adjuster  the adjuster to use, not null
       * @return an object of the same type with the specified adjustment made, not null
       * @throws DateTimeException if unable to make the adjustment
       * @throws ArithmeticException if numeric overflow occurs
       */
      default Temporal with(TemporalAdjuster adjuster) {
          return adjuster.adjustInto(this);
      }
  
      /**
       * Returns an object of the same type as this object with the specified field altered.
       * <p>
       * This returns a new object based on this one with the value for the specified field changed.
       * For example, on a {@code LocalDate}, this could be used to set the year, month or day-of-month.
       * The returned object will have the same observable type as this object.
       * <p>
       * In some cases, changing a field is not fully defined. For example, if the target object is
       * a date representing the 31st January, then changing the month to February would be unclear.
       * In cases like this, the field is responsible for resolving the result. Typically it will choose
       * the previous valid date, which would be the last valid day of February in this example.
       *
       * @implSpec
       * Implementations must check and handle all fields defined in {@link ChronoField}.
       * If the field is supported, then the adjustment must be performed.
       * 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.adjustInto(Temporal, long)}
       * passing {@code this} as the first argument.
       * <p>
       * Implementations must not alter this object.
       * Instead, an adjusted copy of the original must be returned.
       * This provides equivalent, safe behavior for immutable and mutable implementations.
       *
       * @param field  the field to set in the result, not null
       * @param newValue  the new value of the field in the result
       * @return an object of the same type with the specified field set, not null
       * @throws DateTimeException if the field cannot be set
       * @throws UnsupportedTemporalTypeException if the field is not supported
       * @throws ArithmeticException if numeric overflow occurs
       */
      Temporal with(TemporalField field, long newValue);
  
      //-----------------------------------------------------------------------
      /**
       * Returns an object of the same type as this object with an amount added.
       * <p>
       * This adjusts this temporal, adding according to the rules of the specified amount.
       * The amount is typically a {@link java.time.Period} but may be any other type implementing
       * the {@link TemporalAmount} interface, such as {@link java.time.Duration}.
       * <p>
       * Some example code indicating how and why this method is used:
       * <pre>
       *  date = date.plus(period);                // add a Period instance
       *  date = date.plus(duration);              // add a Duration instance
       *  date = date.plus(workingDays(6));        // example user-written workingDays method
       * </pre>
       * <p>
       * Note that calling {@code plus} followed by {@code minus} is not guaranteed to
       * return the same date-time.
       *
       * @implSpec
       * <p>
       * Implementations must not alter either this object or the specified temporal object.
       * Instead, an adjusted copy of the original must be returned.
       * This provides equivalent, safe behavior for immutable and mutable implementations.
       * <p>
       * The default implementation must behave equivalent to this code:
       * <pre>
       *  return amount.addTo(this);
       * </pre>
       *
       * @param amount  the amount to add, not null
       * @return an object of the same type with the specified adjustment made, not null
       * @throws DateTimeException if the addition cannot be made
       * @throws ArithmeticException if numeric overflow occurs
       */
      default Temporal plus(TemporalAmount amount) {
          return amount.addTo(this);
      }
  
      /**
       * Returns an object of the same type as this object with the specified period added.
       * <p>
       * This method returns a new object based on this one with the specified period added.
       * For example, on a {@code LocalDate}, this could be used to add a number of years, months or days.
       * The returned object will have the same observable type as this object.
       * <p>
       * In some cases, changing a field is not fully defined. For example, if the target object is
       * a date representing the 31st January, then adding one month would be unclear.
       * In cases like this, the field is responsible for resolving the result. Typically it will choose
       * the previous valid date, which would be the last valid day of February in this example.
       *
       * @implSpec
       * Implementations must check and handle all units defined in {@link ChronoUnit}.
       * If the unit is supported, then the addition must be performed.
       * If unsupported, then an {@code UnsupportedTemporalTypeException} must be thrown.
       * <p>
       * If the unit is not a {@code ChronoUnit}, then the result of this method
       * is obtained by invoking {@code TemporalUnit.addTo(Temporal, long)}
       * passing {@code this} as the first argument.
       * <p>
       * Implementations must not alter this object.
       * Instead, an adjusted copy of the original must be returned.
       * This provides equivalent, safe behavior for immutable and mutable implementations.
       *
       * @param amountToAdd  the amount of the specified unit to add, may be negative
       * @param unit  the unit of the amount to add, not null
       * @return an object of the same type with the specified period added, not null
       * @throws DateTimeException if the unit cannot be added
       * @throws UnsupportedTemporalTypeException if the unit is not supported
       * @throws ArithmeticException if numeric overflow occurs
       */
      Temporal plus(long amountToAdd, TemporalUnit unit);
  
      //-----------------------------------------------------------------------
      /**
       * Returns an object of the same type as this object with an amount subtracted.
       * <p>
       * This adjusts this temporal, subtracting according to the rules of the specified amount.
       * The amount is typically a {@link java.time.Period} but may be any other type implementing
       * the {@link TemporalAmount} interface, such as {@link java.time.Duration}.
       * <p>
       * Some example code indicating how and why this method is used:
       * <pre>
       *  date = date.minus(period);               // subtract a Period instance
       *  date = date.minus(duration);             // subtract a Duration instance
       *  date = date.minus(workingDays(6));       // example user-written workingDays method
       * </pre>
       * <p>
       * Note that calling {@code plus} followed by {@code minus} is not guaranteed to
       * return the same date-time.
       *
       * @implSpec
       * <p>
       * Implementations must not alter either this object or the specified temporal object.
       * Instead, an adjusted copy of the original must be returned.
       * This provides equivalent, safe behavior for immutable and mutable implementations.
       * <p>
       * The default implementation must behave equivalent to this code:
       * <pre>
       *  return amount.subtractFrom(this);
       * </pre>
       *
       * @param amount  the amount to subtract, not null
       * @return an object of the same type with the specified adjustment made, not null
       * @throws DateTimeException if the subtraction cannot be made
       * @throws ArithmeticException if numeric overflow occurs
       */
      default Temporal minus(TemporalAmount amount) {
          return amount.subtractFrom(this);
      }
  
      /**
       * Returns an object of the same type as this object with the specified period subtracted.
       * <p>
       * This method returns a new object based on this one with the specified period subtracted.
       * For example, on a {@code LocalDate}, this could be used to subtract a number of years, months or days.
       * The returned object will have the same observable type as this object.
       * <p>
       * In some cases, changing a field is not fully defined. For example, if the target object is
       * a date representing the 31st March, then subtracting one month would be unclear.
       * In cases like this, the field is responsible for resolving the result. Typically it will choose
       * the previous valid date, which would be the last valid day of February in this example.
       *
       * @implSpec
       * Implementations must behave in a manor equivalent to the default method behavior.
       * <p>
       * Implementations must not alter this object.
       * Instead, an adjusted copy of the original must be returned.
       * This provides equivalent, safe behavior for immutable and mutable implementations.
       * <p>
       * The default implementation must behave equivalent to this code:
       * <pre>
       *  return (amountToSubtract == Long.MIN_VALUE ?
       *      plus(Long.MAX_VALUE, unit).plus(1, unit) : plus(-amountToSubtract, unit));
       * </pre>
       *
       * @param amountToSubtract  the amount of the specified unit to subtract, may be negative
       * @param unit  the unit of the amount to subtract, not null
       * @return an object of the same type with the specified period subtracted, not null
       * @throws DateTimeException if the unit cannot be subtracted
       * @throws UnsupportedTemporalTypeException if the unit is not supported
       * @throws ArithmeticException if numeric overflow occurs
       */
      default Temporal minus(long amountToSubtract, TemporalUnit unit) {
          return (amountToSubtract == Long.MIN_VALUE ? plus(Long.MAX_VALUE, unit).plus(1, unit) : plus(-amountToSubtract, unit));
      }
  
      //-----------------------------------------------------------------------
      /**
       * Calculates the amount of time until another temporal in terms of the specified unit.
       * <p>
       * This calculates the amount of time between two temporal objects
       * in terms of a single {@code TemporalUnit}.
       * The start and end points are {@code this} and the specified temporal.
       * The end point is converted to be of the same type as the start point if different.
       * The result will be negative if the end is before the start.
       * For example, the amount in hours between two temporal objects can be
       * calculated using {@code startTime.until(endTime, HOURS)}.
       * <p>
       * The calculation returns a whole number, representing the number of
       * complete units between the two temporals.
       * For example, the amount in hours between the times 11:30 and 13:29
       * will only be one hour as it is one minute short of two hours.
       * <p>
       * There are two equivalent ways of using this method.
       * The first is to invoke this method directly.
       * The second is to use {@link TemporalUnit#between(Temporal, Temporal)}:
       * <pre>
       *   // these two lines are equivalent
       *   temporal = start.until(end, unit);
       *   temporal = unit.between(start, end);
       * </pre>
       * The choice should be made based on which makes the code more readable.
       * <p>
       * For example, this method allows the number of days between two dates to
       * be calculated:
       * <pre>
       *  long daysBetween = start.until(end, DAYS);
       *  // or alternatively
       *  long daysBetween = DAYS.between(start, end);
       * </pre>
       *
       * @implSpec
       * Implementations must begin by checking to ensure that the input temporal
       * object is of the same observable type as the implementation.
       * They must then perform the calculation for all instances of {@link ChronoUnit}.
       * An {@code UnsupportedTemporalTypeException} must be thrown for {@code ChronoUnit}
       * instances that are unsupported.
       * <p>
       * If the unit is not a {@code ChronoUnit}, then the result of this method
       * is obtained by invoking {@code TemporalUnit.between(Temporal, Temporal)}
       * passing {@code this} as the first argument and the converted input temporal as
       * the second argument.
       * <p>
       * In summary, implementations must behave in a manner equivalent to this pseudo-code:
       * <pre>
       *  // convert the end temporal to the same type as this class
       *  if (unit instanceof ChronoUnit) {
       *    // if unit is supported, then calculate and return result
       *    // else throw UnsupportedTemporalTypeException for unsupported units
       *  }
       *  return unit.between(this, convertedEndTemporal);
       * </pre>
       * <p>
       * Note that the unit's {@code between} method must only be invoked if the
       * two temporal objects have exactly the same type evaluated by {@code getClass()}.
       * <p>
       * Implementations must ensure that no observable state is altered when this
       * read-only method is invoked.
       *
       * @param endExclusive  the end temporal, exclusive, converted to be of the
       *  same type as this object, not null
       * @param unit  the unit to measure the amount in, not null
       * @return the amount of time between this temporal object and the specified one
       *  in terms of the unit; positive if the specified object is later than this one,
       *  negative if it is earlier than this one
       * @throws DateTimeException if the amount cannot be calculated, or the end
       *  temporal cannot be converted to the same type as this temporal
       * @throws UnsupportedTemporalTypeException if the unit is not supported
       * @throws ArithmeticException if numeric overflow occurs
       */
      long until(Temporal endExclusive, TemporalUnit unit);
  
  }
  