59 lines
1.3 KiB
PHP
59 lines
1.3 KiB
PHP
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<?php
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/*
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* Copyright (c) Alexandre Gomes Gaigalas <alganet@gmail.com>
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* SPDX-License-Identifier: MIT
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*/
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declare(strict_types=1);
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namespace Respect\Validation\Rules;
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use function array_map;
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use function count;
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use function str_split;
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/**
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* Validate whether a given input is a Luhn number.
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*
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* @see https://en.wikipedia.org/wiki/Luhn_algorithm
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*
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* @author Alexander Gorshkov <mazanax@yandex.ru>
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* @author Danilo Correa <danilosilva87@gmail.com>
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* @author Henrique Moody <henriquemoody@gmail.com>
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*/
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final class Luhn extends AbstractRule
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{
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/**
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* {@inheritDoc}
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*/
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public function validate($input): bool
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{
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if (!(new Digit())->validate($input)) {
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return false;
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}
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return $this->isValid((string) $input);
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}
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private function isValid(string $input): bool
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{
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$sum = 0;
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$digits = array_map('intval', str_split($input));
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$numDigits = count($digits);
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$parity = $numDigits % 2;
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for ($i = 0; $i < $numDigits; ++$i) {
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$digit = $digits[$i];
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if ($parity == $i % 2) {
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$digit <<= 1;
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if (9 < $digit) {
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$digit = $digit - 9;
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}
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}
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$sum += $digit;
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}
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return $sum % 10 == 0;
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}
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}
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