public function decode(string $data): string
    {
        $this->validateInput($data);

        $data = str_split($data);
        $data = array_map(function ($character) {
            return strpos($this->options["characters"], $character);
        }, $data);

        $leadingZeroes = 0;
        while (!empty($data) && 0 === $data[0]) {
            $leadingZeroes++;
            array_shift($data);
        }

        $converted = $this->baseConvert($data, 62, 256);

        if (0 < $leadingZeroes) {
            $converted = array_merge(
                array_fill(0, $leadingZeroes, 0),
                $converted
            );
        }

        return implode("", array_map("chr", $converted));
    }