class SwitchUserController

class SwitchUserController extends ControllerBase {
    
    /**
     * The current user.
     *
     * @var \Drupal\Core\Session\AccountProxyInterface
     */
    protected $account;
    
    /**
     * The user storage.
     *
     * @var \Drupal\Core\Entity\EntityStorageInterface
     */
    protected $userStorage;
    
    /**
     * The session manager service.
     *
     * @var \Drupal\Core\Session\SessionManagerInterface
     */
    protected $sessionManager;
    
    /**
     * The session.
     *
     * @var \Symfony\Component\HttpFoundation\Session\Session
     */
    protected $session;
    
    /**
     * Constructs a new SwitchUserController object.
     *
     * @param \Drupal\Core\Session\AccountProxyInterface $account
     *   The current user.
     * @param \Drupal\Core\Entity\EntityStorageInterface $user_storage
     *   The user storage.
     * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
     *   The user storage.
     * @param \Drupal\Core\Session\SessionManagerInterface $session_manager
     *   The session manager service.
     * @param \Symfony\Component\HttpFoundation\Session\Session $session
     *   The session.
     */
    public function __construct(AccountProxyInterface $account, EntityStorageInterface $user_storage, ModuleHandlerInterface $module_handler, SessionManagerInterface $session_manager, Session $session) {
        $this->account = $account;
        $this->userStorage = $user_storage;
        $this->moduleHandler = $module_handler;
        $this->sessionManager = $session_manager;
        $this->session = $session;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container) {
        return new static($container->get('current_user'), $container->get('entity_type.manager')
            ->getStorage('user'), $container->get('module_handler'), $container->get('session_manager'), $container->get('session'));
    }
    
    /**
     * Switches to a different user.
     *
     * We don't call session_save_session() because we really want to change
     * users. Usually unsafe!
     *
     * @param string $name
     *   The username to switch to, or NULL to log out.
     *
     * @return \Symfony\Component\HttpFoundation\RedirectResponse
     *   A redirect response object.
     *
     * @throws \Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException
     */
    public function switchUser($name = NULL) {
        if (empty($name) || !($account = $this->userStorage
            ->loadByProperties([
            'name' => $name,
        ]))) {
            throw new AccessDeniedHttpException();
        }
        $account = reset($account);
        // Call logout hooks when switching from original user.
        $this->moduleHandler
            ->invokeAll('user_logout', [
            $this->account,
        ]);
        // Regenerate the session ID to prevent against session fixation attacks.
        $this->sessionManager
            ->regenerate();
        // Based off masquarade module as:
        // https://www.drupal.org/node/218104 doesn't stick and instead only
        // keeps context until redirect.
        $this->account
            ->setAccount($account);
        $this->session
            ->set('uid', $account->id());
        // Call all login hooks when switching to masquerading user.
        $this->moduleHandler
            ->invokeAll('user_login', [
            $account,
        ]);
        return $this->redirect('<front>');
    }

}