Question

I know we can easily limit the max quantity of a given product a customer can purchase per order, but is it possible (natively or even with a plugin) to limit max quantity of a given product per CUSTOMER ??

I don’t want to use a coupon nor modify the code: it needs to be a sale price with the help of native or extension functionality.

Magento 1.5.1

Answer 1

It is not possible native, but you can make a module that will perform such restrictions.

1. You need to create a resource model, that will retrieve not canceled and not refunded orders for product(s) with particular product id. Actually it just a simple select to sales/order and sales/order_item table. Method of resource model might look like the following:

   public function getPurchasedProductQty(array $productIds, $customerId)
   {
       $select = $this->_getReadAdapter()->select();
       $select
           ->from(array('order_item' => $this->getTable('sales/order_item')),
                     array(
                         'qty' => new Zend_Db_Expr('order_item.ordered_qty - order_item.canceled_qty - order_item.refunded_qty'),
                         'product_id'))
           // Joining order to retrieve info about item and filter out canceled or refunded orders
           ->join(array('order' => $this->getTable('sales/order')),
                  'order.entity_id = order_item.order_id',
                  array())
           // Limit it to the current customer
           ->where('order.customer_id = ?', $customerId)
           // Filter out refunded and canceled orders
           ->where('order.state NOT IN(?)', array(
               Mage_Sales_Model_Order::STATE_CLOSED,
               Mage_Sales_Model_Order::STATE_CANCELED
           ))
           // Add Product Id Condition
           ->where('order_item.product_id IN(?)', $productIds);
   
       return $this->_getReadAdapter()->fetchCol($select);
   }
   

2. Then when you observe sales_quote_item_collection_products_after_load event you just can place your custom logic with checking the restrictions on products that are going to be used in the cart and remove that ones from loaded collection. This logic you should implement yourself.