updating product subtotal in cart contents – Woocommerce

I’ve trying to write my campaign plugin.
Here is the problem,

I want to update, line_subtotal and line_total in a product in $cart_items.

1- woocommerce_cart_product_subtotal is not really working.

2- I tried to redefine array’s element by cart_item_key

                foreach($cartItems as $hash => $perProduct)
                { 
                    if($perProduct['product_id'] = $lastItemsProductId)
                    {
                        if($lastItemsQuantity > 1)
                        {
                            $lineSubtotal = data_get($lastItemInCart, 'line_subtotal');
                            $lineTotal = data_get($lastItemInCart, 'line_total');
                            $newQuantity = $lastItemsQuantity-1; 
                            
                            $lastItemInCart['line_subtotal'] = $newQuantity * $lastItemsPrice;
                            $lastItemInCart['line_total'] = $newQuantity * $lastItemsPrice;  
                            $cartItems[$lastItemsKey] = $lastItemInCart;  
 
                            WC()->cart->calculate_totals();
             
 
                            
                        } else {
                             
                        }
                    }
                     
                }

Also this function runs, in woocommerce_before_calculate_totals action.

When i try it, with woocommerce_get_cart_contents filter, my cart empty itself .

3- The scenario :

When i add A product, (if is selected by system) and if quantity is more than 2, i want to make discount about this product.

Any helps ? Thanks.

Here is the answer

        /**
         * Add filter for order list 
         *
         * @param [int] $product_subtotal
         * @param [object] $product
         * @param [int] $quantity
         * @param [array] $cart
         * @return void
         */
        public function filterWoocommerceCartProductSubtotal($product_subtotal, $product, $quantity, $cart) : string
        {
            $appliedCoupons  = $cart ? $cart->get_applied_coupons() : null;
            $cartCount = $cart ? count($cart->get_cart()) : 0;
            $cartItems = $cart->get_cart();
            $lastItemInCart = last($cartItems);
            $lastItemsProductId = data_get($lastItemInCart, 'product_id', data_get($lastItemInCart, 'product_id'));
            $lastItemsPrice = $lastItemInCart['data']->get_regular_price();
            $lastItemsQuantity = data_get($lastItemInCart, 'quantity');
            $lastItemsKey = data_get($lastItemInCart, 'key');
            
            if( in_array('3al2ode', $appliedCoupons)){  
                if($lastItemsQuantity > 1) {
                    if(@data_get($product,'id') == $lastItemsProductId)
                    {
                        $newSubTotal = 0;
                        $price = $product->get_price();  

                        $newQuantity = $lastItemsQuantity-1; 
                        $quantity = $newQuantity; 
                        $newSubTotal += $price * $quantity;
                
                        return $newSubTotal ? wc_price($newSubTotal) : $product_subtotal; 
                    }
                } 
                
            }  
            return $product_subtotal;
            
        }

The right, filter should be like;

add_filter( 'woocommerce_cart_product_subtotal', [$this,'filterWoocommerceCartProductSubtotal'], 10, 4);