/*

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

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

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

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 * 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,

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 *

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

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/*

 * Copyright (c) 2009-2012, 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 build.tools.tzdb;

import java.util.Objects;

class Utils {

    // Returns the largest (closest to positive infinity)

    public static long floorDiv(long x, long y) {

        long r = x / y;

        // if the signs are different and modulo not zero, round down

        if ((x ^ y) < 0 && (r * y != x)) {

            r--;

        }

        return r;

    }

    // Returns the floor modulus of the {@code long} arguments.

    public static long floorMod(long x, long y) {

        return x - floorDiv(x, y) * y;

    }

    // Returns the sum of its arguments,

    public static long addExact(long x, long y) {

        long r = x + y;

        // HD 2-12 Overflow iff both arguments have the opposite sign of the result

        if (((x ^ r) & (y ^ r)) < 0) {

            throw new ArithmeticException("long overflow");

        }

        return r;

    }

    // Year

    // Returns true if the specified year is a leap year.

    public static boolean isLeapYear(int year) {

        return ((year & 3) == 0) && ((year % 100) != 0 || (year % 400) == 0);

    }

    // The minimum supported year, '-999,999,999'.

    public static final int YEAR_MIN_VALUE = -999_999_999;

    // The maximum supported year, '+999,999,999'.

    public static final int YEAR_MAX_VALUE = 999_999_999;

    // Gets the length of the specified month in days.

    public static int lengthOfMonth(int month, boolean leapYear) {

        switch (month) {

            case 2:        //FEBRUARY:

                return (leapYear ? 29 : 28);

            case 4:        //APRIL:

            case 6:        //JUNE:

            case 9:        //SEPTEMBER:

            case 11:       //NOVEMBER:

                return 30;

            default:

                return 31;

        }

    }

    // Gets the maximum length of the specified month in days.

    public static int maxLengthOfMonth(int month) {

        switch (month) {

            case 2:           //FEBRUARY:

                return 29;

            case 4:           //APRIL:

            case 6:           //JUNE:

            case 9:           //SEPTEMBER:

            case 11:          //NOVEMBER:

                return 30;

            default:

                return 31;

        }

    }

    // DayOfWeek

    // Returns the day-of-week that is the specified number of days after

    // this one, from 1 to 7 for Monday to Sunday.

    public static int plusDayOfWeek(int dow, long days) {

        int amount = (int) (days % 7);

        return (dow - 1 + (amount + 7)) % 7 + 1;

    }

    // Returns the day-of-week that is the specified number of days before

    // this one, from 1 to 7 for Monday to Sunday.

    public static int minusDayOfWeek(int dow, long days) {

        return plusDayOfWeek(dow, -(days % 7));

    }

    // Adjusts the date to the first occurrence of the specified day-of-week

    // before the date being adjusted unless it is already on that day in

    // which case the same object is returned.

    public static LocalDate previousOrSame(LocalDate date, int dayOfWeek) {

        return adjust(date, dayOfWeek, 1);

    }

    // Adjusts the date to the first occurrence of the specified day-of-week

    // after the date being adjusted unless it is already on that day in

    // which case the same object is returned.

    public static LocalDate nextOrSame(LocalDate date, int dayOfWeek) {

        return adjust(date, dayOfWeek, 0);

    }

    // Implementation of next, previous or current day-of-week.

    // @param relative  whether the current date is a valid answer

    private static final LocalDate adjust(LocalDate date, int dow, int relative) {

        int calDow = date.getDayOfWeek();

        if (relative < 2 && calDow == dow) {

            return date;

        }

        if ((relative & 1) == 0) {

            int daysDiff = calDow - dow;

            return date.plusDays(daysDiff >= 0 ? 7 - daysDiff : -daysDiff);

        } else {

            int daysDiff = dow - calDow;

            return date.minusDays(daysDiff >= 0 ? 7 - daysDiff : -daysDiff);

        }

    }

}