class AbstractMultipartPart

abstract class AbstractMultipartPart extends AbstractPart {
    private ?string $boundary = null;
    private array $parts = [];
    public function __construct(AbstractPart ...$parts) {
        parent::__construct();
        foreach ($parts as $part) {
            $this->parts[] = $part;
        }
    }
    
    /**
     * @return AbstractPart[]
     */
    public function getParts() : array {
        return $this->parts;
    }
    public function getMediaType() : string {
        return 'multipart';
    }
    public function getPreparedHeaders() : Headers {
        $headers = parent::getPreparedHeaders();
        $headers->setHeaderParameter('Content-Type', 'boundary', $this->getBoundary());
        return $headers;
    }
    public function bodyToString() : string {
        $parts = $this->getParts();
        $string = '';
        foreach ($parts as $part) {
            $string .= '--' . $this->getBoundary() . "\r\n" . $part->toString() . "\r\n";
        }
        $string .= '--' . $this->getBoundary() . "--\r\n";
        return $string;
    }
    public function bodyToIterable() : iterable {
        $parts = $this->getParts();
        foreach ($parts as $part) {
            (yield '--' . $this->getBoundary() . "\r\n");
            yield from $part->toIterable();
            (yield "\r\n");
        }
        (yield '--' . $this->getBoundary() . "--\r\n");
    }
    public function asDebugString() : string {
        $str = parent::asDebugString();
        foreach ($this->getParts() as $part) {
            $lines = explode("\n", $part->asDebugString());
            $str .= "\n  └ " . array_shift($lines);
            foreach ($lines as $line) {
                $str .= "\n  |" . $line;
            }
        }
        return $str;
    }
    private function getBoundary() : string {
        return $this->boundary ??= strtr(base64_encode(random_bytes(6)), '+/', '-_');
    }

}