class HeaderProcessor

final class HeaderProcessor {
    
    /**
     * Returns the HTTP version, status code, reason phrase, and headers.
     *
     * @param string[] $headers
     *
     * @return array{0:string, 1:int, 2:?string, 3:array}
     *
     * @throws \RuntimeException
     */
    public static function parseHeaders(array $headers) : array {
        if ($headers === []) {
            throw new \RuntimeException('Expected a non-empty array of header data');
        }
        $parts = \explode(' ', \array_shift($headers), 3);
        $version = \explode('/', $parts[0])[1] ?? null;
        if ($version === null) {
            throw new \RuntimeException('HTTP version missing from header data');
        }
        $status = $parts[1] ?? null;
        if ($status === null) {
            throw new \RuntimeException('HTTP status code missing from header data');
        }
        return [
            $version,
            (int) $status,
            $parts[2] ?? null,
            Utils::headersFromLines($headers),
        ];
    }

}