Magento2 – Get Session ID and Make Cart Accessible from Anywhere

I need to make the cart page accessible to an external user?

In Magento 1 I had this in my Controller:

class Sostanza_Livehelp_IndexController extends Mage_Core_Controller_Front_Action {

    protected $_cartInfo;

    public function getcartlhinfoAction() {
    $query_params = $this->getRequest()->getParams();
    if(isset($query_params["MY_PARAM"]){

        $cart = Mage::getUrl('checkout/cart/', array(
                            '_secure' => true,
                            '_query' => array('SID' => $query_params["MY_PARAM"]),  
                            '_store_to_url' => true)
        ); // lastly add store to our url if needed

        $cookieName = "frontend";
        // AN UPPERCASE VERSION OF THIS "frontend" is available in Mag2
        //http://docs.magento.com/m2/ce/user_guide/stores/cookie-reference.html
        $cookieVal = $query_params["MY_PARAM"];
        $cookie = Mage::getSingleton('core/cookie');
        $cookie->set($cookieName, $cookieVal);
        $this->_redirectUrl($cart);
    }
    else {
        $session_id = Mage::getSingleton("core/session")->getEncryptedSessionId();
        $cart_url = Mage::getUrl() . "livehelp/index/getcartlhinfo/?MY_PARAM=" . $session_id;
        $this->_cartInfo = "<a href='";
        $this->_cartInfo .= $cart_url;
        $this->_cartInfo .= "' target='_blank' title='Magento Cart' class='magento-cart'>";
        $this->_cartInfo .= "Magento Cart";
        $this->_cartInfo .= "</a>";

        $cart_encoded = urlencode($this->_cartInfo);

        $this->getResponse()->setHeader("Content-type", "application/json");
        $this->getResponse()->setBody($cart_encoded);
    }

}

So basically if you call /livehelp/getcartlhinfo/ without param it will behave like a rest service and print the url with the session id, otherwise it will redirect you to associated user cart

I already have the route for a custom frontend page so basically I only need to convert this code to read cookie/session and do the redirect in Magento 2

Thank you so much

EDIT

Till now I accomplished this:

class Cart extends \Magento\Framework\App\Action\Action {

    protected $_resultPageFactory;
    protected $_urlBuilder;
    protected $_jsonResult;
    protected $cartParams = array(
        "_secure" => true,
        "_store_to_url" => true,
        "_query" => array()
    );

    CONST PARAM_NAME = "MY_PARAM";

    public function __construct(Context $context, \Magento\Framework\View\Result\PageFactory $resultPageFactory
    , \Magento\Framework\Controller\Result\JsonFactory $resultJsonFactory
    , \Magento\Framework\UrlInterface $urlBuilder
    ) {
        $this->_resultPageFactory = $resultPageFactory;
        $this->_urlBuilder = $urlBuilder;
        $this->_jsonResult = $resultJsonFactory;
        parent::__construct($context);
    }

    public function execute() {
        $params = $this->getRequest()->getParams();
        $cartParams = $this->cartParams;
        if (isset($params[self::PARAM_NAME])) {
            $cartParams["_query"] = array("SID" => $params[self::PARAM_NAME]);
            $cart = $this->_urlBuilder->getUrl("checkout/cart/", $cartParams);
            echo $cart;
            $resultPage = $this->_resultPageFactory->create();
            return $resultPage;
        } else {
           $session_id = "5";
        $cartParams["_query"] = array(self::PARAM_NAME => $session_id);
        $cart_url = $this->_urlBuilder->getUrl("livehelp/index/cart/", $cartParams);

        $cartInfo = "<a href='";
        $cartInfo .= $cart_url;
        $cartInfo .= "' target='_blank' title='Magento Cart' class='magento-cart'>";
        $cartInfo .= "Magento Cart";
        $cartInfo .= "</a>";
        $cart_encoded = urlencode($cartInfo);
        return $this->_jsonResult->create()->setData($cart_encoded);
        }
    }

}

This has the same behaviour, if MY_PARAM is in the URL then it prints something,
otherwise it returns a json response with the url to call.

What I miss now is

1. Acquire session ID
2. Redirect to cart

The idea is to make cart visible to anyone who has the url