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vendor/workerman/validation/library/Rules/Luhn.php

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+<?php
+
+/*
+ * This file is part of Respect/Validation.
+ *
+ * (c) Alexandre Gomes Gaigalas <alexandre@gaigalas.net>
+ *
+ * For the full copyright and license information, please view the LICENSE file
+ * that was distributed with this source code.
+ */
+
+declare(strict_types=1);
+
+namespace Respect\Validation\Rules;
+
+use function array_map;
+use function count;
+use function str_split;
+
+/**
+ * Validate whether a given input is a Luhn number.
+ *
+ * @see https://en.wikipedia.org/wiki/Luhn_algorithm
+ *
+ * @author Alexander Gorshkov <mazanax@yandex.ru>
+ * @author Danilo Correa <danilosilva87@gmail.com>
+ * @author Henrique Moody <henriquemoody@gmail.com>
+ */
+final class Luhn extends AbstractRule
+{
+    /**
+     * {@inheritDoc}
+     */
+    public function validate($input): bool
+    {
+        if (!(new Digit())->validate($input)) {
+            return false;
+        }
+
+        return $this->isValid((string) $input);
+    }
+
+    private function isValid(string $input): bool
+    {
+        $sum = 0;
+        $digits = array_map('intval', str_split($input));
+        $numDigits = count($digits);
+        $parity = $numDigits % 2;
+        for ($i = 0; $i < $numDigits; ++$i) {
+            $digit = $digits[$i];
+            if ($parity == ($i % 2)) {
+                $digit <<= 1;
+                if (9 < $digit) {
+                    $digit = $digit - 9;
+                }
+            }
+            $sum += $digit;
+        }
+
+        return ($sum % 10) == 0;
+    }
+}