xref: /webtrees/app/Factories/IdFactory.php (revision b344f1f7922af1b65f23df39e4b97959ef06b6b4) 
1<?php
2
3/**
4 * webtrees: online genealogy
5 * Copyright (C) 2022 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\Factories;
21
22use Fisharebest\Webtrees\Contracts\IdFactoryInterface;
23use Ramsey\Uuid\Exception\RandomSourceException;
24use Ramsey\Uuid\Uuid;
25
26use function dechex;
27use function hexdec;
28use function str_pad;
29use function strtoupper;
30use function substr;
31
32use const STR_PAD_LEFT;
33
34/**
35 * Create a unique identifier.
36 */
37class IdFactory implements IdFactoryInterface
38{
39    /**
40     * @return string
41     */
42    public function uuid(): string
43    {
44        try {
45            return strtolower(strtr(Uuid::uuid4()->toString(), ['-' => '']));
46        } catch (RandomSourceException) {
47            // uuid4() can fail if there is insufficient entropy in the system.
48            return '';
49        }
50    }
51
52    /**
53     * An identifier for use in CSS/HTML
54     *
55     * @param string $prefix
56     *
57     * @return string
58     */
59    public function id(string $prefix = 'id-'): string
60    {
61        return $prefix . $this->uuid();
62    }
63
64    /**
65     * A value for _UID fields, as created by PAF
66     *
67     * @return string
68     */
69    public function pafUid(): string
70    {
71        $uid = strtoupper(strtr($this->uuid(), ['-' => '']));
72
73        if ($uid === '') {
74            return '';
75        }
76
77        return $uid . $this->pafUidChecksum($uid);
78    }
79
80    /**
81     * @param string $uid - exactly 32 hex characters
82     *
83     * @return string
84     */
85    public function pafUidChecksum(string $uid): string
86    {
87        $checksum_a = 0; // a sum of the bytes
88        $checksum_b = 0; // a sum of the incremental values of $checksum_a
89
90        for ($i = 0; $i < 32; $i += 2) {
91            $checksum_a += hexdec(substr($uid, $i, 2));
92            $checksum_b += $checksum_a & 0xff;
93        }
94
95        $digit1 = str_pad(dechex($checksum_a), 2, '0', STR_PAD_LEFT);
96        $digit2 = str_pad(dechex($checksum_b), 2, '0', STR_PAD_LEFT);
97
98        return strtoupper($digit1 . $digit2);
99    }
100}
101