Check if promotion valid on product page

I am trying to add something on the product detail page to show if a promotion will be active for it. Let's assume I have the promotion id or its code. Is there any ready mechanism for this?

Due to the fact that I searched but didn't find one I thought in that case I could create a temporary shopping cart, add the product to it, add the promotion, recalculate and see if the promotion is active or not. My attempt is as follows:

$tempCart = $this->cartService->createNew(Uuid::randomHex());
        
$lineItem = $this->lineItemFactoryRegistry->create([
    'type' => LineItem::PRODUCT_LINE_ITEM_TYPE,
    'referencedId' => $productId,
    'quantity' => 1,
], $salesChannelContext);
$this->cartService->add($tempCart, $lineItem, $salesChannelContext);

$promotionItem = $this->promotionLineItemFactory->create([
    'referencedId' => 'a74cdde1e8bf41a3b2997ff3d5b61ed9',
], $salesChannelContext);
$this->cartService->add($tempCart, $promotionItem, $salesChannelContext);

$this->promotionProcessor->process($tempCart->getData(), $tempCart, $tempCart, $salesChannelContext, new CartBehavior());

$tempCart->markModified();
$tempCart2 = $this->cartService->recalculate($tempCart, $salesChannelContext);

But nothing happens. In the sense the basket is recalculated, but the line with the promotion disappears. Even though the promotion is certainly valid and available, because there are no conditions except the sales channel.

Can anyone give me a hint on how to approach this? Maybe I have started wrong?

You could try the PromotionCollector service with a placeholder promotion added to the cart, to see if it yields errors trying to collect the actual promotion based on the code. In theory the collector should also consider all limitations and conditions, given the code is valid.

$uniqueKey = Uuid::randomHex();
$code = 'foobar';

$item = new LineItem($uniqueKey, PromotionProcessor::LINE_ITEM_TYPE);
$item->setLabel($uniqueKey);
$item->setGood(false);
$item->setReferencedId($code);
$item->setPriceDefinition(new PercentagePriceDefinition(0));

$cart->add($item);

$behavior = new CartBehavior();
$container->get(PromotionCollector::class)->collect($cart->getData(), $cart, $salesChannelContext, $behavior);

var_dump($cart->getErrors()->count());
var_dump($cart->getErrors()->first()->getMessage());
// int(1)
// string(37) "Promotion with code foobar not found!"

Run it here.