public function spaceLeft($usedSpace)
{
if (self::UNLIMITED === $this->amount) {
return $usedSpace;
}
if ($usedSpace >= $this->amount) {
return 0;
}
$spaceLeft = $this->amount - $usedSpace;
if (0 >= $spaceLeft) {
return 0;
}
return $spaceLeft;
}