Discounts exclude from existing discount

Hi,

You can actually do this with a normal discount, no coupon needed, thanks to the way discounts are prioritized.

For a given product, only one automatic discount applies, and HikaShop keeps the most specific one: a discount set on that product wins over a discount set on its category, which itself wins over a discount that applies to the whole shop.

So all you have to do is create one discount with:

- Value: 20 %
- No product restriction
- No category restriction (so it applies to the whole shop)

On the products that already have their own discount (set per product or per category), that more specific discount keeps winning, so your 20 % is not applied there. On all the other products, which have no discount, the 20 % is the only one available, so it applies. That is exactly the "20 % on everything except the products that are already discounted" behavior you are looking for, and it stays automatic.

The only thing to keep in mind is that this relies on your existing discounts being set on the products or on their categories, which is the case for you. Leave the new 20 % one with no product and no category so that it stays the lowest priority and only fills the gaps.

Hi,

For that last part there is no built-in "exclude this category" option on discounts, so the clean way is a small system plugin (group "hikashop") that reacts to the onSelectDiscount event. That event runs right before HikaShop picks the discount for each product, so you can remove the whole-shop discount for the products of the category you want to leave out, and those products then get no discount at all (no fake 0% or 0.001% discount, nothing shown on the front end).

Here is the method to put in your plugin, just set your category id at the top:

public function onSelectDiscount(&$product, &$discountsSelected, &$discounts, $zone_id, &$parent)
{
	// Category to keep out of the whole-shop discount
	$excludedCategoryId = 42;

	// The whole-shop discount is the least specific one, stored under key 20.
	// If it was not selected for this product, there is nothing to remove.
	if(empty($discountsSelected[20]))
		return;

	// Use the parent product id for variants
	$productId = (int)$product->product_id;
	if(!empty($product->product_parent_id))
		$productId = (int)$product->product_parent_id;

	$db = \Joomla\CMS\Factory::getDBO();

	// Bounds of the excluded category so its sub-categories are covered too
	$db->setQuery('SELECT category_left, category_right FROM '.hikashop_table('category').
		' WHERE category_id = '.(int)$excludedCategoryId);
	$cat = $db->loadObject();
	if(empty($cat))
		return;

	// Is the product linked to the excluded category or one of its children?
	$db->setQuery(
		'SELECT COUNT(*) FROM '.hikashop_table('product_category').' AS pc'.
		' JOIN '.hikashop_table('category').' AS c ON pc.category_id = c.category_id'.
		' WHERE pc.product_id = '.$productId.
		' AND c.category_left >= '.(int)$cat->category_left.
		' AND c.category_right <= '.(int)$cat->category_right
	);

	if($db->loadResult() > 0) {
		// Remove the whole-shop discount: this category gets no discount at all
		unset($discountsSelected[20]);
	}
}

We'll look into adding extra options for this in HikaShop for its next version in August / September.