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vendor/fakerphp/faker/src/Faker/Calculator/Luhn.php

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+<?php
+
+namespace Faker\Calculator;
+
+/**
+ * Utility class for generating and validating Luhn numbers.
+ *
+ * Luhn algorithm is used to validate credit card numbers, IMEI numbers, and
+ * National Provider Identifier numbers.
+ *
+ * @see http://en.wikipedia.org/wiki/Luhn_algorithm
+ */
+class Luhn
+{
+    /**
+     * @return int
+     */
+    private static function checksum(string $number)
+    {
+        $number = (string) $number;
+        $length = strlen($number);
+        $sum = 0;
+
+        for ($i = $length - 1; $i >= 0; $i -= 2) {
+            $sum += $number[$i];
+        }
+
+        for ($i = $length - 2; $i >= 0; $i -= 2) {
+            $sum += array_sum(str_split($number[$i] * 2));
+        }
+
+        return $sum % 10;
+    }
+
+    /**
+     * @return string
+     */
+    public static function computeCheckDigit(string $partialNumber)
+    {
+        $checkDigit = self::checksum($partialNumber . '0');
+
+        if ($checkDigit === 0) {
+            return '0';
+        }
+
+        return (string) (10 - $checkDigit);
+    }
+
+    /**
+     * Checks whether a number (partial number + check digit) is Luhn compliant
+     *
+     * @return bool
+     */
+    public static function isValid(string $number)
+    {
+        return self::checksum($number) === 0;
+    }
+
+    /**
+     * Generate a Luhn compliant number.
+     *
+     * @return string
+     */
+    public static function generateLuhnNumber(string $partialValue)
+    {
+        if (!preg_match('/^\d+$/', $partialValue)) {
+            throw new \InvalidArgumentException('Argument should be an integer.');
+        }
+
+        return $partialValue . Luhn::computeCheckDigit($partialValue);
+    }
+}