class.ilCtrlStructureCidGenerator.php

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<?php

declare(strict_types=1);

class ilCtrlStructureCidGenerator
{
    private int $index;

    public function __construct(int $starting_index = 0)
    {
        $this->index = $starting_index;
    }

    public function getIndexByCid(string $cid): int
    {
        if (strpos($cid, '-') === 0) {
            $inverted_cid = str_replace('-', '', $cid);
            $index = (int) base_convert($inverted_cid, 36, 10);

            return $this->invertIndex($index);
        }

        return (int) base_convert($cid, 36, 10);
    }

    public function getCidByIndex(int $index): string
    {
        if (0 > $index) {
            return '-' . base_convert((string) $this->invertIndex($index), 10, 36);
        }

        return base_convert((string) $index, 10, 36);
    }

    public function getCid(): string
    {
        return $this->getCidByIndex($this->index++);
    }

    private function invertIndex(int $index): int
    {
        return (-1 * $index);
    }
}