<?phpnamespace GuzzleHttp;use GuzzleHttp\Promise\PromiseInterface;use Psr\Http\Message\RequestInterface;/** * Prepares requests that contain a body, adding the Content-Length, * Content-Type, and Expect headers. * * @final */class PrepareBodyMiddleware{    /**     * @var callable(RequestInterface, array): PromiseInterface     */    private $nextHandler;    /**     * @param callable(RequestInterface, array): PromiseInterface $nextHandler Next handler to invoke.     */    public function __construct(callable $nextHandler)    {        $this->nextHandler = $nextHandler;    }    public function __invoke(RequestInterface $request, array $options): PromiseInterface    {        $fn = $this->nextHandler;        // Don't do anything if the request has no body.        if ($request->getBody()->getSize() === 0) {            return $fn($request, $options);        }        $modify = [];        // Add a default content-type if possible.        if (!$request->hasHeader('Content-Type')) {            if ($uri = $request->getBody()->getMetadata('uri')) {                if (is_string($uri) && $type = Psr7\MimeType::fromFilename($uri)) {                    $modify['set_headers']['Content-Type'] = $type;                }            }        }        // Add a default content-length or transfer-encoding header.        if (!$request->hasHeader('Content-Length')            && !$request->hasHeader('Transfer-Encoding')        ) {            $size = $request->getBody()->getSize();            if ($size !== null) {                $modify['set_headers']['Content-Length'] = $size;            } else {                $modify['set_headers']['Transfer-Encoding'] = 'chunked';            }        }        // Add the expect header if needed.        $this->addExpectHeader($request, $options, $modify);        return $fn(Psr7\Utils::modifyRequest($request, $modify), $options);    }    /**     * Add expect header     */    private function addExpectHeader(RequestInterface $request, array $options, array &$modify): void    {        // Determine if the Expect header should be used        if ($request->hasHeader('Expect')) {            return;        }        $expect = $options['expect'] ?? null;        // Return if disabled or if you're not using HTTP/1.1 or HTTP/2.0        if ($expect === false || $request->getProtocolVersion() < 1.1) {            return;        }        // The expect header is unconditionally enabled        if ($expect === true) {            $modify['set_headers']['Expect'] = '100-Continue';            return;        }        // By default, send the expect header when the payload is > 1mb        if ($expect === null) {            $expect = 1048576;        }        // Always add if the body cannot be rewound, the size cannot be        // determined, or the size is greater than the cutoff threshold        $body = $request->getBody();        $size = $body->getSize();        if ($size === null || $size >= (int) $expect || !$body->isSeekable()) {            $modify['set_headers']['Expect'] = '100-Continue';        }    }}