TYPO3 CMS 7 fully loaded TSFE in EiD

CustomerAutocompletion.php

<?php

namespace Project\Namespace\Hooks;

use Psr\Http\Message\ResponseInterface;
use Psr\Http\Message\ServerRequestInterface;
use TYPO3\CMS\Backend\Utility\BackendUtility;
use TYPO3\CMS\Core\Core\Bootstrap;
use TYPO3\CMS\Core\Utility\ExtensionManagementUtility;
use TYPO3\CMS\Core\Utility\GeneralUtility;
use TYPO3\CMS\Extbase\Object\ObjectManager;
use TYPO3\CMS\Extensionmanager\Utility\ConfigurationUtility;
use TYPO3\CMS\Frontend\ContentObject\ContentObjectRenderer;
use TYPO3\CMS\Frontend\Controller\TypoScriptFrontendController;

class CustomerAutocompletion {
    /**
     * @var TypoScriptFrontendController
     */
    protected $controller;

    /**
     * @var Bootstrap
     */
    protected $bootstrap;

    public function processRequest(ServerRequestInterface $request, ResponseInterface $response)
    {
        $extConf = $this->getExtensionConfiguration();

        $this->initializeController();
        $this->boot();

        $cObj = $this->getContentObjectRenderer();
      
        // generate $output
      
        $response = $response->withHeader('Content-Type', 'text/html; charset=utf-8');
        $response->getBody()->write($output);

        return $response;
    }
  
    /**
     * @return array
     */
    protected function getExtensionConfiguration()
    {
        /** @var ObjectManager $objectManager */
        $objectManager = GeneralUtility::makeInstance(ObjectManager::class);

        $configurationUtility = $objectManager->get(ConfigurationUtility::class);

        return $configurationUtility->getCurrentConfiguration(static::EXT_KEY);
    }

    /**
     * @return ContentObjectRenderer
     */
    protected function getContentObjectRenderer()
    {
        return GeneralUtility::makeInstance(ContentObjectRenderer::class);
    }

    /**
     * Creates an instance of TSFE and sets it as a global variable
     *
     * @return void
     */
    protected function initializeController()
    {
        $this->controller = GeneralUtility::makeInstance(
            TypoScriptFrontendController::class,
            $GLOBALS['TYPO3_CONF_VARS'],
            GeneralUtility::_GP('id'),
            GeneralUtility::_GP('type'),
            GeneralUtility::_GP('no_cache'),
            GeneralUtility::_GP('cHash'),
            GeneralUtility::_GP('jumpurl'),
            GeneralUtility::_GP('MP'),
            GeneralUtility::_GP('RDCT')
        );
        // setting the global variable for the controller
        // We have to define this as reference here, because there is code around
        // which exchanges the TSFE object in the global variable. The reference ensures
        // that the $controller member always works on the same object as the global variable.
        // This is a dirty workaround and bypasses the protected access modifier of the controller member.
        $GLOBALS['TSFE'] = &$this->controller;
    }

    /**
     * Boot the environment
     */
    protected function boot()
    {
        $this->bootstrap = Bootstrap::getInstance();
        $this->bootstrap->loadCachedTca();

        $this->controller->connectToDB();
        $this->controller->initFEuser();

        $this->controller->determineId();
        $this->controller->initTemplate();
        $this->controller->getConfigArray();

        if (ExtensionManagementUtility::isLoaded('realurl')) {
            $rootline = BackendUtility::BEgetRootLine(1);
            $host = BackendUtility::firstDomainRecord($rootline);
            $_SERVER['HTTP_HOST'] = $host;
        }
    }
}

ext_localconf.php

<?php

if (!defined('TYPO3_MODE')) {
    die('Access denied.');
}

$TYPO3_CONF_VARS['FE']['eID_include']['autocomplete'] = \Project\Namespace\Hooks\CustomerAutocompletion::class . '::processRequest';