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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) 2013, 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:
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   *  * 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.chrono;
  
  import java.time.DateTimeException;
  import java.time.temporal.ChronoUnit;
  import java.time.temporal.Temporal;
  import java.time.temporal.TemporalAmount;
  import java.time.temporal.TemporalUnit;
  import java.time.temporal.UnsupportedTemporalTypeException;
  import java.util.List;
  import java.util.Objects;
  
  /**
   * A date-based amount of time, such as '3 years, 4 months and 5 days' in an
   * arbitrary chronology, intended for advanced globalization use cases.
   * <p>
   * This interface models a date-based amount of time in a calendar system.
   * While most calendar systems use years, months and days, some do not.
   * Therefore, this interface operates solely in terms of a set of supported
   * units that are defined by the {@code Chronology}.
   * The set of supported units is fixed for a given chronology.
   * The amount of a supported unit may be set to zero.
   * <p>
   * The period is modeled as a directed amount of time, meaning that individual
   * parts of the period may be negative.
   *
   * @implSpec
   * This interface must be implemented with care to ensure other classes operate correctly.
   * All implementations that can be instantiated must be final, immutable and thread-safe.
   * Subclasses should be Serializable wherever possible.
   *
   * @since 1.8
   */
  public interface ChronoPeriod
          extends TemporalAmount {
  
      /**
       * Obtains a {@code ChronoPeriod} consisting of amount of time between two dates.
       * <p>
       * The start date is included, but the end date is not.
       * The period is calculated using {@link ChronoLocalDate#until(ChronoLocalDate)}.
       * As such, the calculation is chronology specific.
       * <p>
       * The chronology of the first date is used.
       * The chronology of the second date is ignored, with the date being converted
       * to the target chronology system before the calculation starts.
       * <p>
       * The result of this method can be a negative period if the end is before the start.
       * In most cases, the positive/negative sign will be the same in each of the supported fields.
       *
       * @param startDateInclusive  the start date, inclusive, specifying the chronology of the calculation, not null
       * @param endDateExclusive  the end date, exclusive, in any chronology, not null
       * @return the period between this date and the end date, not null
       * @see ChronoLocalDate#until(ChronoLocalDate)
       */
      public static ChronoPeriod between(ChronoLocalDate startDateInclusive, ChronoLocalDate endDateExclusive) {
          Objects.requireNonNull(startDateInclusive, "startDateInclusive");
          Objects.requireNonNull(endDateExclusive, "endDateExclusive");
          return startDateInclusive.until(endDateExclusive);
      }
  
      //-----------------------------------------------------------------------
      /**
       * Gets the value of the requested unit.
       * <p>
       * The supported units are chronology specific.
       * They will typically be {@link ChronoUnit#YEARS YEARS},
       * {@link ChronoUnit#MONTHS MONTHS} and {@link ChronoUnit#DAYS DAYS}.
       * Requesting an unsupported unit will throw an exception.
       *
       * @param unit the {@code TemporalUnit} for which to return the value
       * @return the long value of the unit
       * @throws DateTimeException if the unit is not supported
       * @throws UnsupportedTemporalTypeException if the unit is not supported
       */
      @Override
      long get(TemporalUnit unit);
  
      /**
       * Gets the set of units supported by this period.
       * <p>
       * The supported units are chronology specific.
       * They will typically be {@link ChronoUnit#YEARS YEARS},
       * {@link ChronoUnit#MONTHS MONTHS} and {@link ChronoUnit#DAYS DAYS}.
       * They are returned in order from largest to smallest.
       * <p>
       * This set can be used in conjunction with {@link #get(TemporalUnit)}
       * to access the entire state of the period.
       *
       * @return a list containing the supported units, not null
       */
      @Override
      List<TemporalUnit> getUnits();
  
      /**
       * Gets the chronology that defines the meaning of the supported units.
       * <p>
       * The period is defined by the chronology.
       * It controls the supported units and restricts addition/subtraction
       * to {@code ChronoLocalDate} instances of the same chronology.
       *
       * @return the chronology defining the period, not null
       */
      Chronology getChronology();
  
      //-----------------------------------------------------------------------
      /**
       * Checks if all the supported units of this period are zero.
       *
       * @return true if this period is zero-length
       */
      default boolean isZero() {
          for (TemporalUnit unit : getUnits()) {
              if (get(unit) != 0) {
                  return false;
              }
          }
          return true;
      }
  
      /**
       * Checks if any of the supported units of this period are negative.
       *
       * @return true if any unit of this period is negative
       */
      default boolean isNegative() {
          for (TemporalUnit unit : getUnits()) {
              if (get(unit) < 0) {
                  return true;
              }
          }
          return false;
      }
  
      //-----------------------------------------------------------------------
      /**
       * Returns a copy of this period with the specified period added.
       * <p>
       * If the specified amount is a {@code ChronoPeriod} then it must have
       * the same chronology as this period. Implementations may choose to
       * accept or reject other {@code TemporalAmount} implementations.
       * <p>
       * This instance is immutable and unaffected by this method call.
       *
       * @param amountToAdd  the period to add, not null
       * @return a {@code ChronoPeriod} based on this period with the requested period added, not null
       * @throws ArithmeticException if numeric overflow occurs
       */
      ChronoPeriod plus(TemporalAmount amountToAdd);
  
      /**
       * Returns a copy of this period with the specified period subtracted.
       * <p>
       * If the specified amount is a {@code ChronoPeriod} then it must have
       * the same chronology as this period. Implementations may choose to
       * accept or reject other {@code TemporalAmount} implementations.
       * <p>
       * This instance is immutable and unaffected by this method call.
       *
       * @param amountToSubtract  the period to subtract, not null
       * @return a {@code ChronoPeriod} based on this period with the requested period subtracted, not null
       * @throws ArithmeticException if numeric overflow occurs
       */
      ChronoPeriod minus(TemporalAmount amountToSubtract);
  
      //-----------------------------------------------------------------------
      /**
       * Returns a new instance with each amount in this period in this period
       * multiplied by the specified scalar.
       * <p>
       * This returns a period with each supported unit individually multiplied.
       * For example, a period of "2 years, -3 months and 4 days" multiplied by
       * 3 will return "6 years, -9 months and 12 days".
       * No normalization is performed.
       *
       * @param scalar  the scalar to multiply by, not null
       * @return a {@code ChronoPeriod} based on this period with the amounts multiplied
       *  by the scalar, not null
       * @throws ArithmeticException if numeric overflow occurs
       */
      ChronoPeriod multipliedBy(int scalar);
  
      /**
       * Returns a new instance with each amount in this period negated.
       * <p>
       * This returns a period with each supported unit individually negated.
       * For example, a period of "2 years, -3 months and 4 days" will be
       * negated to "-2 years, 3 months and -4 days".
       * No normalization is performed.
       *
       * @return a {@code ChronoPeriod} based on this period with the amounts negated, not null
       * @throws ArithmeticException if numeric overflow occurs, which only happens if
       *  one of the units has the value {@code Long.MIN_VALUE}
       */
      default ChronoPeriod negated() {
          return multipliedBy(-1);
      }
  
      //-----------------------------------------------------------------------
      /**
       * Returns a copy of this period with the amounts of each unit normalized.
       * <p>
       * The process of normalization is specific to each calendar system.
       * For example, in the ISO calendar system, the years and months are
       * normalized but the days are not, such that "15 months" would be
       * normalized to "1 year and 3 months".
       * <p>
       * This instance is immutable and unaffected by this method call.
       *
       * @return a {@code ChronoPeriod} based on this period with the amounts of each
       *  unit normalized, not null
       * @throws ArithmeticException if numeric overflow occurs
       */
      ChronoPeriod normalized();
  
      //-------------------------------------------------------------------------
      /**
       * Adds this period to the specified temporal object.
       * <p>
       * This returns a temporal object of the same observable type as the input
       * with this period added.
       * <p>
       * In most cases, it is clearer to reverse the calling pattern by using
       * {@link Temporal#plus(TemporalAmount)}.
       * <pre>
       *   // these two lines are equivalent, but the second approach is recommended
       *   dateTime = thisPeriod.addTo(dateTime);
       *   dateTime = dateTime.plus(thisPeriod);
       * </pre>
       * <p>
       * The specified temporal must have the same chronology as this period.
       * This returns a temporal with the non-zero supported units added.
       * <p>
       * This instance is immutable and unaffected by this method call.
       *
       * @param temporal  the temporal object to adjust, not null
       * @return an object of the same type with the adjustment made, not null
       * @throws DateTimeException if unable to add
       * @throws ArithmeticException if numeric overflow occurs
       */
      @Override
      Temporal addTo(Temporal temporal);
  
      /**
       * Subtracts this period from the specified temporal object.
       * <p>
       * This returns a temporal object of the same observable type as the input
       * with this period subtracted.
       * <p>
       * In most cases, it is clearer to reverse the calling pattern by using
       * {@link Temporal#minus(TemporalAmount)}.
       * <pre>
       *   // these two lines are equivalent, but the second approach is recommended
       *   dateTime = thisPeriod.subtractFrom(dateTime);
       *   dateTime = dateTime.minus(thisPeriod);
       * </pre>
       * <p>
       * The specified temporal must have the same chronology as this period.
       * This returns a temporal with the non-zero supported units subtracted.
       * <p>
       * This instance is immutable and unaffected by this method call.
       *
       * @param temporal  the temporal object to adjust, not null
       * @return an object of the same type with the adjustment made, not null
       * @throws DateTimeException if unable to subtract
       * @throws ArithmeticException if numeric overflow occurs
       */
      @Override
      Temporal subtractFrom(Temporal temporal);
  
      //-----------------------------------------------------------------------
      /**
       * Checks if this period is equal to another period, including the chronology.
       * <p>
       * Compares this period with another ensuring that the type, each amount and
       * the chronology are the same.
       * Note that this means that a period of "15 Months" is not equal to a period
       * of "1 Year and 3 Months".
       *
       * @param obj  the object to check, null returns false
       * @return true if this is equal to the other period
       */
      @Override
      boolean equals(Object obj);
  
      /**
       * A hash code for this period.
       *
       * @return a suitable hash code
       */
      @Override
      int hashCode();
  
      //-----------------------------------------------------------------------
      /**
       * Outputs this period as a {@code String}.
       * <p>
       * The output will include the period amounts and chronology.
       *
       * @return a string representation of this period, not null
       */
      @Override
      String toString();
  
  }
  