Set position of product when it sells out in Magento - magento

Question

A client wants all products that are sold out to appear at the end of the product listings and I'm struggling to get it to work at the minute, hence the question. It's worth noting that all the categories in the system are set to only use 'Best Value' positioning for their product ordering and that this repositioning must be done automatically.
Currently I've added an observer to the 'sales_convert_quote_item_to_order_item' event which is the point where the cart items are added to the order itself (seemed like a sensible place to target).
The problem I've found is that obviously the qty available for a product is stored on the products inventory record but the products positioning is stored against the category itself (and then indexed).
I don't really want to resort to using SQL so was hoping someone here would be able to offer some sort of suggestion for a method to use.
My Observer method currently looks like this but it doesn't work because the getUsedProducts method isn't available for some reason. Here it is anyway:
$cart = Mage::getModel('checkout/cart')->getQuote();
foreach($cart->getAllItems() as $key=>$item):
print_r(get_class_methods($item));
echo ">>> ".$item->getProductType();
if($item->getProductType()):
$item = $item->load($item->getId());
//print_r(get_class_methods($item));
$_productCollection = Mage::getModel('catalog/product_type_configurable')->getUsedProducts(null,$item);
print_r($_productCollection);
$stockLevel = 0;
foreach($_productCollection as $product):
$childProductData = $product->getData();
$stockLevel+= $childProductData['stock_item']['qty'];
endforeach;
echo "<br />STOCK LEVEL: $stockLevel<br />";
if($stockLevel <= 0):
echo "ZERO";
//return true;
endif;
endif;
echo "<br />";
endforeach;
I recognise that this isn't a great way of doing this and as such would be quite intensive it there were a lot of products in the cart. But as the order isn't created at this point then I can't use that either.
Any pointers or suggestions would be gratefully received.
Thanks.

Answer 1

If I am correctly understood from the Problem:
...A client wants all products that are sold out to appear at the end of the product listings...
If listings = categories then why don't u change rendering logic? Simply extend catalog product list and override get product collection method.
What u need to achieve is that all sold out products are at the end of the list. So you can sort loaded collection of products with one of these functions.

Answer 2

You can also use Bestseller logic for listing the products.With the help of this link http://inchoo.net/ecommerce/magento/bestseller-products-in-magento/ Or http://blog.magikcommerce.com/how-to-display-best-selling-products-on-magento-store-home-page/ you will know how to get the bestseller products and then you need to call this best seller block in product list.Hope this will help you if you are still searching for the solution.