class ImmediateStalenessHandler

final class ImmediateStalenessHandler implements StalenessHandlerInterface, ReferenceCounterInterface {
    
    /** @var Closure[]|null */
    private ?array $onStale = [];
    private int $count = 0;
    public function acquire(bool $persistent = false) : void {
        $this->count++;
        if ($persistent) {
            $this->onStale = null;
        }
    }
    public function release() : void {
        if (--$this->count !== 0 || !$this->onStale) {
            return;
        }
        $callbacks = $this->onStale;
        $this->onStale = [];
        foreach ($callbacks as $callback) {
            $callback();
        }
    }
    public function onStale(Closure $callback) : void {
        if ($this->onStale === null) {
            return;
        }
        $this->onStale[] = $callback;
    }

}