class ManifestElement

class ManifestElement {
    public const XMLNS = 'https://phar.io/xml/manifest/1.0';
    
    /** @var DOMElement */
    private $element;
    public function __construct(DOMElement $element) {
        $this->element = $element;
    }
    protected function getAttributeValue(string $name) : string {
        if (!$this->element
            ->hasAttribute($name)) {
            throw new ManifestElementException(sprintf('Attribute %s not set on element %s', $name, $this->element->localName));
        }
        return $this->element
            ->getAttribute($name);
    }
    protected function hasAttribute(string $name) : bool {
        return $this->element
            ->hasAttribute($name);
    }
    protected function getChildByName(string $elementName) : DOMElement {
        $element = $this->element
            ->getElementsByTagNameNS(self::XMLNS, $elementName)
            ->item(0);
        if (!$element instanceof DOMElement) {
            throw new ManifestElementException(sprintf('Element %s missing', $elementName));
        }
        return $element;
    }
    protected function getChildrenByName(string $elementName) : DOMNodeList {
        $elementList = $this->element
            ->getElementsByTagNameNS(self::XMLNS, $elementName);
        if ($elementList->length === 0) {
            throw new ManifestElementException(sprintf('Element(s) %s missing', $elementName));
        }
        return $elementList;
    }
    protected function hasChild(string $elementName) : bool {
        return $this->element
            ->getElementsByTagNameNS(self::XMLNS, $elementName)->length !== 0;
    }

}