class Key

final class Key {
    private ?float $expiringTime = null;
    private array $state = [];
    private bool $serializable = true;
    public function __construct(string $resource) {
    }
    public function __toString() : string {
        return $this->resource;
    }
    public function hasState(string $stateKey) : bool {
        return isset($this->state[$stateKey]);
    }
    public function setState(string $stateKey, mixed $state) : void {
        $this->state[$stateKey] = $state;
    }
    public function removeState(string $stateKey) : void {
        unset($this->state[$stateKey]);
    }
    public function getState(string $stateKey) : mixed {
        return $this->state[$stateKey];
    }
    public function markUnserializable() : void {
        $this->serializable = false;
    }
    public function resetLifetime() : void {
        $this->expiringTime = null;
    }
    
    /**
     * @param float $ttl the expiration delay of locks in seconds
     */
    public function reduceLifetime(float $ttl) : void {
        $newTime = microtime(true) + $ttl;
        if (null === $this->expiringTime || $this->expiringTime > $newTime) {
            $this->expiringTime = $newTime;
        }
    }
    
    /**
     * Returns the remaining lifetime in seconds.
     */
    public function getRemainingLifetime() : ?float {
        return null === $this->expiringTime ? null : $this->expiringTime - microtime(true);
    }
    public function isExpired() : bool {
        return null !== $this->expiringTime && $this->expiringTime <= microtime(true);
    }
    public function __sleep() : array {
        if (!$this->serializable) {
            throw new UnserializableKeyException('The key cannot be serialized.');
        }
        return [
            'resource',
            'expiringTime',
            'state',
        ];
    }

}