<?php

/**
 * This file was originally part of brick/math
 *
 * Copyright (c) 2013-present Benjamin Morel
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 *
 * @link https://github.com/brick/math brick/math at GitHub
 */

declare(strict_types=1);

namespace Ramsey\Uuid\Math;

/**
 * Specifies a rounding behavior for numerical operations capable of discarding
 * precision.
 *
 * Each rounding mode indicates how the least significant returned digit of a
 * rounded result is to be calculated. If fewer digits are returned than the
 * digits needed to represent the exact numerical result, the discarded digits
 * will be referred to as the discarded fraction regardless the digits'
 * contribution to the value of the number. In other words, considered as a
 * numerical value, the discarded fraction could have an absolute value greater
 * than one.
 */
final class RoundingMode
{
    /**
     * Private constructor. This class is not instantiable.
     *
     * @codeCoverageIgnore
     */
    private function __construct()
    {
    }

    /**
     * Asserts that the requested operation has an exact result, hence no
     * rounding is necessary.
     */
    public const UNNECESSARY = 0;

    /**
     * Rounds away from zero.
     *
     * Always increments the digit prior to a nonzero discarded fraction.
     * Note that this rounding mode never decreases the magnitude of the
     * calculated value.
     */
    public const UP = 1;

    /**
     * Rounds towards zero.
     *
     * Never increments the digit prior to a discarded fraction (i.e.,
     * truncates). Note that this rounding mode never increases the magnitude of
     * the calculated value.
     */
    public const DOWN = 2;

    /**
     * Rounds towards positive infinity.
     *
     * If the result is positive, behaves as for UP; if negative, behaves as for
     * DOWN. Note that this rounding mode never decreases the calculated value.
     */
    public const CEILING = 3;

    /**
     * Rounds towards negative infinity.
     *
     * If the result is positive, behave as for DOWN; if negative, behave as for
     * UP. Note that this rounding mode never increases the calculated value.
     */
    public const FLOOR = 4;

    /**
     * Rounds towards "nearest neighbor" unless both neighbors are equidistant,
     * in which case round up.
     *
     * Behaves as for UP if the discarded fraction is >= 0.5; otherwise, behaves
     * as for DOWN. Note that this is the rounding mode commonly taught at
     * school.
     */
    public const HALF_UP = 5;

    /**
     * Rounds towards "nearest neighbor" unless both neighbors are equidistant,
     * in which case round down.
     *
     * Behaves as for UP if the discarded fraction is > 0.5; otherwise, behaves
     * as for DOWN.
     */
    public const HALF_DOWN = 6;

    /**
     * Rounds towards "nearest neighbor" unless both neighbors are equidistant,
     * in which case round towards positive infinity.
     *
     * If the result is positive, behaves as for HALF_UP; if negative, behaves
     * as for HALF_DOWN.
     */
    public const HALF_CEILING = 7;

    /**
     * Rounds towards "nearest neighbor" unless both neighbors are equidistant,
     * in which case round towards negative infinity.
     *
     * If the result is positive, behaves as for HALF_DOWN; if negative, behaves
     * as for HALF_UP.
     */
    public const HALF_FLOOR = 8;

    /**
     * Rounds towards the "nearest neighbor" unless both neighbors are
     * equidistant, in which case rounds towards the even neighbor.
     *
     * Behaves as for HALF_UP if the digit to the left of the discarded fraction
     * is odd; behaves as for HALF_DOWN if it's even.
     *
     * Note that this is the rounding mode that statistically minimizes
     * cumulative error when applied repeatedly over a sequence of calculations.
     * It is sometimes known as "Banker's rounding", and is chiefly used in the
     * USA.
     */
    public const HALF_EVEN = 9;
}
