<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Event/etc/events.xsd">
<event name="controller_action_predispatch">
    <observer name="controller_action_predispatch" instance="BBBBObserverControllerPredispatch" />
</event>
</config>

<?php

namespace BBBBObserver;

use MagentoFrameworkEventObserverInterface;
use MagentoFrameworkEventObserver;

class ControllerPredispatch implements ObserverInterface
{
    /**
     * @var MagentoFrameworkUrlInterface
     */
    protected $url;

    /**
     * @var MagentoFrameworkAppResponseHttp
     */
    protected $http;

    /** @var MagentoCustomerModelSession */
    protected $customerSession;

    /**
     * @param MagentoFrameworkUrlInterface $url
     * @param MagentoFrameworkAppResponseHttp $http
     * @param MagentoCustomerModelSession $customerSession
     */
    public function __construct(
        MagentoFrameworkUrlInterface $url,
        MagentoFrameworkAppResponseHttp $http,
        MagentoCustomerModelSession $customerSession
    )
    {
        $this->url = $url;
        $this->http = $http;
        $this->customerSession = $customerSession;
    }

    /**
     * Manages redirect
     */
    public function execute(Observer $observer)
    {
        /**
         * Check if user logged in
         */
        if ($this->customerSession->isLoggedIn()) {
            return;
        }

        if ($observer->getRequest()->getFullActionName() == 'cms_index_index') {
            /**
             * Redirect to login
             */
            $this->http->setRedirect($this->url->getUrl('bb-check-extension.html'), 301);
        }
    }
}