<?php
/**
* @see https://github.com/laminas/laminas-validator for the canonical source repository
* @copyright https://github.com/laminas/laminas-validator/blob/master/COPYRIGHT.md
* @license https://github.com/laminas/laminas-validator/blob/master/LICENSE.md New BSD License
*/
namespace Laminas\Validator\Isbn;
class Isbn10
{
/**
* @param int|string $value
* @return int|string
*/
public function getChecksum($value)
{
$sum = $this->sum($value);
return $this->checksum($sum);
}
/**
* Calculate the value sum.
*
* @param int|string $value
* @return int
*/
private function sum($value)
{
$sum = 0;
for ($i = 0; $i < 9; $i++) {
$sum += (10 - $i) * $value[$i];
}
return $sum;
}
/**
* Calculate the checksum for the value's sum.
*
* @param int $sum
* @return int|string
*/
private function checksum($sum)
{
$checksum = 11 - ($sum % 11);
if ($checksum == 11) {
return '0';
}
if ($checksum == 10) {
return 'X';
}
return $checksum;
}
}