Magento 2 get quantity of product in cart without loop

Question

I have written a controller in Magento 2 that adds products to the logged in users account.

The controller is working properly however i am facing a slight issue.

You cannot add a product to your cart with a greater quantity than what is in stock. so you cannot add a quantity of 6 if there are only 5 in stock, this results in a 500 error. to get around this I am using this:

if($QuantityToAdd > $ProductStock){
   // throw error
}
else{
   // add to cart
}

and this is working fine for the scenario above.

however, this will also allow the user to add 4 products, and then try to add another 2 products separately. This will again result in a 500 error, stating:

main.ERROR: We don't have as many "XXXX" as you requested.

in the logs.

So I added a foreach, on the current cart items to get the quantity of that product already in the cart:

if(($QuantityToAdd + $QuantityInCart) > $ProductStock){
   // throw error
}
else{
   // add to cart
}

this solved my errors. However now the controller regularly times out as it will cycle the cart foreach within the add products for each, so if the user is trying to add 200 product variants and they already have 200 products in the cart, the controller will loop over 40,000 times.

200x200 = 40,000 loops

The quantities mentioned here are potentially at the lower end of possible usage.

To optimise this I have found a function:

if ($this->checkoutSession->create()->getQuote()->hasProductId($productId)) {
    //product is available in the cart
}

Without performing another foreach, or any kind of loop, is it possible to get the current quantity of the product in the cart, if the above if statement is true?

or alternatively,

$this->cart->addProduct($productToadd, $params);

is there a function that updates the product in the cart instead of adding the new quantity on to the existing quantity?

Thanks.

EDIT:

Foreach by request:

foreach($products as $purchase){
        $productSku = $purchase['Sku'];
        $qty = $purchase['Quantity'];

        $loadedProduct = $this->getProductBySku($productSku);

        $productStock = $this->stockRegistry->getStockItem($loadedProduct->getId());
        $manageStock = $productStock->getData('manage_stock');

        if($manageStock == "1"){
          $productQty = $productStock->getQty();
          $quantityInCart = 0;
          $items = $this->cart->getQuote()->getAllItems();
          $productId=$loadedProduct->getId();
          foreach ($items as $item) {
                if ($item->getProductId() == $productId) {
                  $quantityInCart = $quantityInCart + $item->getQty();
                }
            }
          if($productStock->getBackorders() > 1){
            if(($qty + $quantityInCart) > $productQty){
              $this->_messageManager->addError(__("Failed to add " . $purchase['Name'] . " - " .$purchase['Option'] . " " . $productQty . " available"));
              $return[] = $purchase['Name'] . " - " .$purchase['Option'] . " " . $productQty . " available";
              $proceed = false;
              $returnObject->success = false;
            }
          }
        }
      }

This foreach checks through each of the products the user is trying to add, if they are all fine, there is a second for each to add the products.

Answer 1

I don't fully understand your need, but I think I can help a bit.
this code

        foreach ($items as $item) {
            if ($item->getProductId() == $productId) {
              $quantityInCart = $quantityInCart + $item->getQty();
            }
        }

gets executed multiple times with the same result.
You can try to call it outside the other foreach loop like this:

$qtysInCart = [];
$items = $this->cart->getQuote()->getAllItems();
foreach ($items as $item) {
    $cartProductId = $item->getProductId();
    if (!isset($qtysInCart[$cartProductId])) {
        $qtysInCart[$cartProductId] = 0;
    }
    $qtysInCart[$cartProductId] += $item->getQty();
}

Now you should have an array with all the qtys in the cart for each product in the cart.

Now do the other loop:

foreach($products as $purchase){
    $productSku = $purchase['Sku'];
    $qty = $purchase['Quantity'];
    $loadedProduct = $this->getProductBySku($productSku);
    //rest of your code here except the other foreach
    //but instead of `if(($qty + $quantityInCart) > $productQty){` do this
    ...
    $productId = $loadedProduct->getId();
    if (isset($qtysInCart[$productId]) and $qty + $qtysInCart[$productId] > $productQty) {
         //error code in here
    }
}

Now the complexity will be O(n) instead of O(n^2). like you had before.
So for 200 products in the cart and adding 200 more you will get 200 + 200 checks instead of 200 * 200.

Note: I didn't test the code so watch out for typos.

Answer 2

In addition to Marius answer, and considering the amount of products you mentioned in your question. You have $quoteId

$quoteId = $this->cart->getQuote()->getId();

So, in terms of performance, you can get this info directly from quote_item database table. You'd just add \Magento\Framework\App\ResourceConnection in your constructor class, and then...

$qtysInCart = [];
$connection = $this->_resourceConnection->getConnection();
$query = $connection->select()
    ->from($this->_resourceConnection->getTableName('quote_item'))
    ->where('quote_id = ?', $quoteId)
foreach ($connection->fetchAll($query) as $row){
    $qtysInCart[$row['product_id']] = $row['qty'];
}

Using same approach you can get inventory info for involved product IDs (querying cataloginventory_stock_item database table) to check if requested qty can be satisfied, which will make your request kindly lighter & faster

UPDATE

In fact, if I've understood what you want, you'll need only 2 SQL queries (you get all product IDs in quote with the first, so you can run the inventory one using IN condition & you'll get all info you need in your controller logic)