Magento Buy X Get Y free Price rules - magento

Question

I have added new rule in Magneto for buying x product and getting y free . I have added a configurable product with multiple simple products . This rule works fine if I buy two of simple products with same sku values. What I want is that if user buys two simple products with different sku they should get second free .
How can i achieve this ?

Answer 1

This cannot be done with the default implementation of cart rules. You need to create new module and add your own type of rule to the list. I have made once such a module, in the following manner:
1) I add my own option to action dropdown. Luckily there is an event adminhtml_block_salesrule_actions_prepareform where you can hook. I used something like this
$form = $observer->getEvent()->getForm();
$options = $form->getElement('simple_action')->getValues();
$options[] = array(
'value' => self::BUY_ANY_X_GET_Y_ACTION,
'label' => Mage::helper('mymodule')->__('Extended Buy X get Y free (search all cart, discount amount is Y)'),
);
$form->getElement('simple_action')->setValues($options);
2) Then I hook into salesrule_validator_process where I checked whether cart items match the rule.
This was a little bit tricky as this validator is run for each cart item so you have to count how many times it was called and which items you have checked. I used conditions tab to prepare rules that says which X items have to be bought in order to get Y items according to conditions in actions tab.
With the first run of the validator you iterate over all cart collection and divides all products in two groups: one contains items that met criteria set by conditions tab, the second one met the criteria set by actions tab. In other words you form two arrays that contains items for X and items for Y.
foreach($quote->getItemsCollection() as $item) {
if (!$item->hasParentItemId()) {
if ($rule->getActions()->validate($item)) {
$ruleItems['y'][] = $item;
}
foreach($rule->getConditions()->getConditions() as $condition) {
foreach($condition->getConditions() as $check) {
if ($check->validate($item)) {
$ruleItems['x'][] = $item;
}
}
}
}
}
You calculate how many X's are there and how many Y's products will get discount. The when the event is called for each item you check if the item is in Y array and if there is enough discounts left for that item. If so you need to set discount amount and base discount amount calculated as item_qty * price and item_qty * base_price respectively. You need to set those values on result object that is in data passed to the observer method like:
$item = $observer->getEvent()->getItem();
$result = $observer->getEvent()->getResult();
$result->setDiscountAmount($item->getQty * $item->getPrice());
$result->setBaseDiscountAmount($item->getQty * $item->getBasePrice());