class StackedHttpKernel

class StackedHttpKernel implements HttpKernelInterface, TerminableInterface {
    
    /**
     * The decorated kernel.
     *
     * @var \Symfony\Component\HttpKernel\HttpKernelInterface
     */
    private $kernel;
    
    /**
     * A set of middlewares that are wrapped around this kernel.
     *
     * @var array
     */
    private $middlewares = [];
    
    /**
     * Constructs a stacked HTTP kernel.
     *
     * @param \Symfony\Component\HttpKernel\HttpKernelInterface $kernel
     *   The decorated kernel.
     * @param array $middlewares
     *   An array of previous middleware services.
     */
    public function __construct(HttpKernelInterface $kernel, array $middlewares) {
        $this->kernel = $kernel;
        $this->middlewares = $middlewares;
    }
    
    /**
     * {@inheritdoc}
     */
    public function handle(Request $request, $type = HttpKernelInterface::MAIN_REQUEST, $catch = TRUE) : Response {
        return $this->kernel
            ->handle($request, $type, $catch);
    }
    
    /**
     * {@inheritdoc}
     */
    public function terminate(Request $request, Response $response) : void {
        $previous = NULL;
        foreach ($this->middlewares as $kernel) {
            // If the previous kernel was terminable we can assume this middleware
            // has already been called.
            if (!$previous instanceof TerminableInterface && $kernel instanceof TerminableInterface) {
                $kernel->terminate($request, $response);
            }
            $previous = $kernel;
        }
    }

}