xref: /webtrees/app/Factories/IdFactory.php (revision 5c3d04310abb803e416e94b25d8fc7d1ac558d9a) 
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 $ex) {
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     * @return string
56     */
57    public function id(string $prefix = 'id-'): string
58    {
59        return $prefix . $this->uuid();
60    }
61
62    /**
63     * A value for _UID fields, as created by PAF
64     *
65     * @return string
66     */
67    public function pafUid(): string
68    {
69        $uid = strtoupper(strtr($this->uuid(), ['-' => '']));
70
71        if ($uid === '') {
72            return '';
73        }
74
75        return $uid . $this->pafUidChecksum($uid);
76    }
77
78    /**
79     * @param string $uid - exactly 32 hex characters
80     *
81     * @return string
82     */
83    public function pafUidChecksum(string $uid): string
84    {
85        $checksum_a = 0; // a sum of the bytes
86        $checksum_b = 0; // a sum of the incremental values of $checksum_a
87
88        for ($i = 0; $i < 32; $i += 2) {
89            $checksum_a += hexdec(substr($uid, $i, 2));
90            $checksum_b += $checksum_a & 0xff;
91        }
92
93        $digit1 = str_pad(dechex($checksum_a), 2, '0', STR_PAD_LEFT);
94        $digit2 = str_pad(dechex($checksum_b), 2, '0', STR_PAD_LEFT);
95
96        return strtoupper($digit1 . $digit2);
97    }
98}
99