xref: /webtrees/app/Services/RomanNumeralsService.php (revision e873f434551745f888937263ff89e80db3b0f785) 
1<?php
2
3/**
4 * webtrees: online genealogy
5 * Copyright (C) 2023 webtrees development team
6 * This program is free software: you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation, either version 3 of the License, or
9 * (at your option) any later version.
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
14 * You should have received a copy of the GNU General Public License
15 * along with this program. If not, see <https://www.gnu.org/licenses/>.
16 */
17
18declare(strict_types=1);
19
20namespace Fisharebest\Webtrees\Services;
21
22use function str_starts_with;
23use function strlen;
24use function substr;
25
26/**
27 * Convert to and from Roman Numerals
28 */
29class RomanNumeralsService
30{
31    // Convert numbers to/from roman numerals
32    private const array ROMAN_NUMERALS = [
33        1000 => 'M',
34        900  => 'CM',
35        500  => 'D',
36        400  => 'CD',
37        100  => 'C',
38        90   => 'XC',
39        50   => 'L',
40        40   => 'XL',
41        10   => 'X',
42        9    => 'IX',
43        5    => 'V',
44        4    => 'IV',
45        1    => 'I',
46    ];
47
48    /**
49     * Convert a decimal number to roman numerals
50     *
51     * @param int $number
52     *
53     * @return string
54     */
55    public function numberToRomanNumerals(int $number): string
56    {
57        if ($number < 1) {
58            // Cannot convert zero/negative numbers
59            return (string) $number;
60        }
61        $roman = '';
62        foreach (self::ROMAN_NUMERALS as $key => $value) {
63            while ($number >= $key) {
64                $roman  .= $value;
65                $number -= $key;
66            }
67        }
68
69        return $roman;
70    }
71
72    /**
73     * Convert a roman numeral to decimal
74     *
75     * @param string $roman
76     *
77     * @return int
78     */
79    public function romanNumeralsToNumber(string $roman): int
80    {
81        $num = 0;
82        foreach (self::ROMAN_NUMERALS as $key => $value) {
83            while (str_starts_with($roman, $value)) {
84                $num += $key;
85                $roman = substr($roman, strlen($value));
86            }
87        }
88
89        return $num;
90    }
91}
92