/*

 * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

/*

 * 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) 2008-2012, 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.

 *

 *  * Redistributions in binary form must reproduce the above copyright notice,

 *    this list of conditions and the following disclaimer in the documentation

 *    and/or other materials provided with the distribution.

 *

 *  * Neither the name of JSR-310 nor the names of its contributors

 *    may be used to endorse or promote products derived from this software

 *    without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR

 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,

 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,

 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR

 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF

 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING

 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS

 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 */

package java.time;

import static java.time.LocalTime.NANOS_PER_DAY;

import static java.time.LocalTime.NANOS_PER_HOUR;

import static java.time.LocalTime.NANOS_PER_MINUTE;

import static java.time.LocalTime.NANOS_PER_SECOND;

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

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

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

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

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

import static java.time.temporal.ChronoUnit.DAYS;

import static java.time.temporal.ChronoUnit.MONTHS;

import static java.time.temporal.ChronoUnit.NANOS;

import static java.time.temporal.ChronoUnit.YEARS;

import java.io.Serializable;

import java.time.format.DateTimeParseException;

import java.time.temporal.Chrono;

import java.time.temporal.ChronoField;

import java.time.temporal.ChronoUnit;

import java.time.temporal.Temporal;

import java.time.temporal.TemporalAccessor;

import java.time.temporal.TemporalAdder;

import java.time.temporal.TemporalSubtractor;

import java.time.temporal.TemporalUnit;

import java.time.temporal.ValueRange;

import java.util.Objects;

/**

 * A period of time, measured using the most common units, such as '3 Months, 4 Days and 7 Hours'.

 * <p>

 * A {@code Period} represents an amount of time measured in terms of the most commonly used units:

 * <p><ul>

 * <li>{@link ChronoUnit#YEARS YEARS}</li>

 * <li>{@link ChronoUnit#MONTHS MONTHS}</li>

 * <li>{@link ChronoUnit#DAYS DAYS}</li>

 * <li>time units with an {@linkplain TemporalUnit#isDurationEstimated() exact duration}</li>

 * </ul><p>

 * The period may be used with any calendar system with the exception is methods with an "ISO" suffix.

 * The meaning of a "year" or a "month" is only applied when the object is added to a date.

 * <p>

 * The period is modeled as a directed amount of time, meaning that individual parts of the

 * period may be negative.

 *

 * <h3>Specification for implementors</h3>

 * This class is immutable and thread-safe.

 * The maximum number of hours that can be stored is about 2.5 million, limited by storing

 * a single {@code long} nanoseconds for all time units internally.

 *

 * @since 1.8

 */

public final class Period

        implements TemporalAdder, TemporalSubtractor, Serializable {

    // maximum hours is 2,562,047

    /**

     * A constant for a period of zero.

     */

    public static final Period ZERO = new Period(0, 0, 0, 0);

    /**

     * Serialization version.

     */

    private static final long serialVersionUID = -8290556941213247973L;

    /**

     * The number of years.

     */

    private final int years;

    /**

     * The number of months.

     */

    private final int months;

    /**

     * The number of days.

     */

    private final int days;

    /**

     * The number of nanoseconds.

     */

    private final long nanos;

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

    /**

     * Obtains a {@code Period} from date-based and time-based fields.

     * <p>

     * This creates an instance based on years, months, days, hours, minutes and seconds.

     * Within a period, the time fields are always normalized.

     *

     * @param years  the amount of years, may be negative

     * @param months  the amount of months, may be negative

     * @param days  the amount of days, may be negative

     * @param hours  the amount of hours, may be negative

     * @param minutes  the amount of minutes, may be negative

     * @param seconds  the amount of seconds, may be negative

     * @return the period, not null

     */

    public static Period of(int years, int months, int days, int hours, int minutes, int seconds) {

        return of(years, months, days, hours, minutes, seconds, 0);

    }

    /**

     * Obtains a {@code Period} from date-based and time-based fields.

     * <p>

     * This creates an instance based on years, months, days, hours, minutes, seconds and nanoseconds.

     * Within a period, the time fields are always normalized.

     *

     * @param years  the amount of years, may be negative

     * @param months  the amount of months, may be negative

     * @param days  the amount of days, may be negative

     * @param hours  the amount of hours, may be negative

     * @param minutes  the amount of minutes, may be negative

     * @param seconds  the amount of seconds, may be negative

     * @param nanos  the amount of nanos, may be negative

     * @return the period, not null

     */

    public static Period of(int years, int months, int days, int hours, int minutes, int seconds, long nanos) {

        if ((years | months | days | hours | minutes | seconds | nanos) == 0) {

            return ZERO;

        }

        long totSecs = Math.addExact(hours * 3600L, minutes * 60L) + seconds;

        long totNanos = Math.addExact(Math.multiplyExact(totSecs, 1_000_000_000L), nanos);

        return create(years, months, days, totNanos);

    }

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

    /**

     * Obtains a {@code Period} from date-based fields.

     * <p>

     * This creates an instance based on years, months and days.

     *

     * @param years  the amount of years, may be negative

     * @param months  the amount of months, may be negative

     * @param days  the amount of days, may be negative

     * @return the period, not null

     */

    public static Period ofDate(int years, int months, int days) {

        return of(years, months, days, 0, 0, 0, 0);

    }

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

    /**

     * Obtains a {@code Period} from time-based fields.

     * <p>

     * This creates an instance based on hours, minutes and seconds.

     * Within a period, the time fields are always normalized.

     *

     * @param hours  the amount of hours, may be negative

     * @param minutes  the amount of minutes, may be negative

     * @param seconds  the amount of seconds, may be negative

     * @return the period, not null

     */

    public static Period ofTime(int hours, int minutes, int seconds) {

        return of(0, 0, 0, hours, minutes, seconds, 0);

    }

    /**

     * Obtains a {@code Period} from time-based fields.

     * <p>

     * This creates an instance based on hours, minutes, seconds and nanoseconds.

     * Within a period, the time fields are always normalized.

     *

     * @param hours  the amount of hours, may be negative

     * @param minutes  the amount of minutes, may be negative

     * @param seconds  the amount of seconds, may be negative

     * @param nanos  the amount of nanos, may be negative

     * @return the period, not null

     */

    public static Period ofTime(int hours, int minutes, int seconds, long nanos) {

        return of(0, 0, 0, hours, minutes, seconds, nanos);

    }

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

    /**

     * Obtains an instance of {@code Period} from a period in the specified unit.

     * <p>

     * The parameters represent the two parts of a phrase like '6 Days'. For example:

     * <pre>

     *  Period.of(3, SECONDS);

     *  Period.of(5, YEARS);

     * </pre>

     * The specified unit must be one of the supported units from {@link ChronoUnit},

     * {@code YEARS}, {@code MONTHS} or {@code DAYS} or be a time unit with an

     * {@linkplain TemporalUnit#isDurationEstimated() exact duration}.

     * Other units throw an exception.

     *

     * @param amount  the amount of the period, measured in terms of the unit, positive or negative

     * @param unit  the unit that the period is measured in, must have an exact duration, not null

     * @return the period, not null

     * @throws DateTimeException if the period unit is invalid

     * @throws ArithmeticException if a numeric overflow occurs

     */

    public static Period of(long amount, TemporalUnit unit) {

        return ZERO.plus(amount, unit);

    }

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

    /**

     * Obtains a {@code Period} from a {@code Duration}.

     * <p>

     * This converts the duration to a period.

     * Within a period, the time fields are always normalized.

     * The years, months and days fields will be zero.

     * <p>

     * To populate the days field, call {@link #normalizedHoursToDays()} on the created period.

     *

     * @param duration  the duration to convert, not null

     * @return the period, not null

     * @throws ArithmeticException if numeric overflow occurs

     */

    public static Period of(Duration duration) {

        Objects.requireNonNull(duration, "duration");

        if (duration.isZero()) {

            return ZERO;

        }

        return new Period(0, 0, 0, duration.toNanos());

    }

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

    /**

     * Returns a {@code Period} consisting of the number of years, months, days,

     * hours, minutes, seconds, and nanoseconds between two {@code TemporalAccessor} instances.

     * <p>

     * The start date is included, but the end date is not. Only whole years count.

     * For example, from {@code 2010-01-15} to {@code 2011-03-18} is one year, two months and three days.

     * <p>

     * This method examines the {@link ChronoField fields} {@code YEAR}, {@code MONTH_OF_YEAR},

     * {@code DAY_OF_MONTH} and {@code NANO_OF_DAY}

     * The difference between each of the fields is calculated independently from the others.

     * At least one of the four fields must be present.

     * <p>

     * The four units are typically retained without normalization.

     * However, years and months are normalized if the range of months is fixed, as it is with ISO.

     * <p>

     * The result of this method can be a negative period if the end is before the start.

     * The negative sign can be different in each of the four major units.

     *

     * @param start  the start date, inclusive, not null

     * @param end  the end date, exclusive, not null

     * @return the period between the date-times, not null

     * @throws DateTimeException if the two date-times do have similar available fields

     * @throws ArithmeticException if numeric overflow occurs

     */

    public static Period between(TemporalAccessor start, TemporalAccessor end) {

        if (Chrono.from(start).equals(Chrono.from(end)) == false) {

            throw new DateTimeException("Unable to calculate period as date-times have different chronologies");

        }

        int years = 0;

        int months = 0;

        int days = 0;

        long nanos = 0;

        boolean valid = false;

        if (start.isSupported(YEAR)) {

            years = Math.toIntExact(Math.subtractExact(end.getLong(YEAR), start.getLong(YEAR)));

            valid = true;

        }

        if (start.isSupported(MONTH_OF_YEAR)) {

            months = Math.toIntExact(Math.subtractExact(end.getLong(MONTH_OF_YEAR), start.getLong(MONTH_OF_YEAR)));

            ValueRange startRange = Chrono.from(start).range(MONTH_OF_YEAR);

            ValueRange endRange = Chrono.from(end).range(MONTH_OF_YEAR);

            if (startRange.isFixed() && startRange.isIntValue() && startRange.equals(endRange)) {

                int monthCount = (int) (startRange.getMaximum() - startRange.getMinimum() + 1);

                long totMonths = ((long) months) + years * monthCount;

                months = (int) (totMonths % monthCount);

                years = Math.toIntExact(totMonths / monthCount);

            }

            valid = true;

        }

        if (start.isSupported(DAY_OF_MONTH)) {

            days = Math.toIntExact(Math.subtractExact(end.getLong(DAY_OF_MONTH), start.getLong(DAY_OF_MONTH)));

            valid = true;

        }

        if (start.isSupported(NANO_OF_DAY)) {

            nanos = Math.subtractExact(end.getLong(NANO_OF_DAY), start.getLong(NANO_OF_DAY));

            valid = true;

        }

        if (valid == false) {

            throw new DateTimeException("Unable to calculate period as date-times do not have any valid fields");

        }

        return create(years, months, days, nanos);

    }

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

    /**

     * Obtains a {@code Period} consisting of the number of years, months,

     * and days between two dates.

     * <p>

     * The start date is included, but the end date is not.

     * The period is calculated by removing complete months, then calculating

     * the remaining number of days, adjusting to ensure that both have the same sign.

     * The number of months is then split into years and months based on a 12 month year.

     * A month is considered if the end day-of-month is greater than or equal to the start day-of-month.

     * For example, from {@code 2010-01-15} to {@code 2011-03-18} is one year, two months and three days.

     * <p>

     * The result of this method can be a negative period if the end is before the start.

     * The negative sign will be the same in each of year, month and day.

     *

     * @param startDate  the start date, inclusive, not null

     * @param endDate  the end date, exclusive, not null

     * @return the period between the dates, not null

     * @throws ArithmeticException if numeric overflow occurs

     */

    public static Period betweenISO(LocalDate startDate, LocalDate endDate) {

        long startMonth = startDate.getLong(EPOCH_MONTH);

        long endMonth = endDate.getLong(EPOCH_MONTH);

        long totalMonths = endMonth - startMonth;  // safe

        int days = endDate.getDayOfMonth() - startDate.getDayOfMonth();

        if (totalMonths > 0 && days < 0) {

            totalMonths--;

            LocalDate calcDate = startDate.plusMonths(totalMonths);

            days = (int) (endDate.toEpochDay() - calcDate.toEpochDay());  // safe

        } else if (totalMonths < 0 && days > 0) {

            totalMonths++;

            days -= endDate.lengthOfMonth();

        }

        long years = totalMonths / 12;  // safe

        int months = (int) (totalMonths % 12);  // safe

        return ofDate(Math.toIntExact(years), months, days);

    }

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

    /**

     * Obtains a {@code Period} consisting of the number of hours, minutes,

     * seconds and nanoseconds between two times.

     * <p>

     * The start time is included, but the end time is not.

     * The period is calculated from the difference between the nano-of-day values

     * of the two times. For example, from {@code 13:45:00} to {@code 14:50:30.123456789}

     * is {@code P1H5M30.123456789S}.

     * <p>

     * The result of this method can be a negative period if the end is before the start.

     *

     * @param startTime  the start time, inclusive, not null

     * @param endTime  the end time, exclusive, not null

     * @return the period between the times, not null

     * @throws ArithmeticException if numeric overflow occurs

     */

    public static Period betweenISO(LocalTime startTime, LocalTime endTime) {

        return create(0, 0, 0, endTime.toNanoOfDay() - startTime.toNanoOfDay());

    }

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

    /**

     * Obtains a {@code Period} from a text string such as {@code PnYnMnDTnHnMn.nS}.

     * <p>

     * This will parse the string produced by {@code toString()} which is

     * a subset of the ISO-8601 period format {@code PnYnMnDTnHnMn.nS}.

     * <p>

     * The string consists of a series of numbers with a suffix identifying their meaning.

     * The values, and suffixes, must be in the sequence year, month, day, hour, minute, second.

     * Any of the number/suffix pairs may be omitted providing at least one is present.

     * If the period is zero, the value is normally represented as {@code PT0S}.

     * The numbers must consist of ASCII digits.

     * Any of the numbers may be negative. Negative zero is not accepted.

     * The number of nanoseconds is expressed as an optional fraction of the seconds.

     * There must be at least one digit before any decimal point.

     * There must be between 1 and 9 inclusive digits after any decimal point.

     * The letters will all be accepted in upper or lower case.

     * The decimal point may be either a dot or a comma.

     *

     * @param text  the text to parse, not null

     * @return the parsed period, not null

     * @throws DateTimeParseException if the text cannot be parsed to a period

     */

    public static Period parse(final CharSequence text) {

        Objects.requireNonNull(text, "text");

        return new PeriodParser(text).parse();

    }

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

    /**

     * Creates an instance.

     *

     * @param years  the amount

     * @param months  the amount

     * @param days  the amount

     * @param nanos  the amount

     */

    private static Period create(int years, int months, int days, long nanos) {

        if ((years | months | days | nanos) == 0) {

            return ZERO;

        }

        return new Period(years, months, days, nanos);

    }

    /**

     * Constructor.

     *

     * @param years  the amount

     * @param months  the amount

     * @param days  the amount

     * @param nanos  the amount

     */

    private Period(int years, int months, int days, long nanos) {

        this.years = years;

        this.months = months;

        this.days = days;

        this.nanos = nanos;

    }

    /**

     * Resolves singletons.

     *

     * @return the resolved instance

     */

    private Object readResolve() {

        if ((years | months | days | nanos) == 0) {

            return ZERO;

        }

        return this;

    }

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

    /**

     * Checks if this period is zero-length.

     *

     * @return true if this period is zero-length

     */

    public boolean isZero() {

        return (this == ZERO);

    }

    /**

     * Checks if this period is fully positive, excluding zero.

     * <p>

     * This checks whether all the amounts in the period are positive,

     * defined as greater than zero.

     *

     * @return true if this period is fully positive excluding zero

     */

    public boolean isPositive() {

        return ((years | months | days | nanos) > 0);

    }

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

    /**

     * Gets the amount of years of this period.

     *

     * @return the amount of years of this period

     */

    public int getYears() {

        return years;

    }

    /**

     * Gets the amount of months of this period.

     *

     * @return the amount of months of this period

     */

    public int getMonths() {

        return months;

    }

    /**

     * Gets the amount of days of this period.

     *

     * @return the amount of days of this period

     */

    public int getDays() {

        return days;

    }

    /**

     * Gets the amount of hours of this period.

     * <p>

     * Within a period, the time fields are always normalized.

     *

     * @return the amount of hours of this period