Set default combination automaticly based on stock Prestashop 1.7 - prestashop

Question

i need Prestashop to:
Check stock of combinations from a product.
If a combination is out of stock, set default combination to a different combination which is in stock.
This way the shop will not show : 'out of stock' at the product, on the category listing. Makes no sense, because the product is not out of stock, only 1 combination is out of stock.
Another solution will be: the out of stock sticker to check if there are any combinations in stock.
Please do not advise any modules.
Example given:
T-shirt in size Small, Medium and Large.
Small: 0 stock, Medium: 10 stock, Large: 10 stock.
Prestashop will now show T-shirt as out of stock on the frontend, unless i manually check Medium or Large as a default size.

Answer 1

You will need to modify ProductController(/controllers/front/ProductController.php)
Basically what i did was to check if the default attribute has stock. If there is stock,then there is no need to look else where.
If there is no stock, then get all the product attributes and loop through the attributes. Once attribute with stock is found, delete the old default attribute and set the found as default attribute.
Add this methods inside the productController Class
/*
start set default based on stock
*/
public function getProductAttributes()
{
$sql = "SELECT * FROM " . _DB_PREFIX_ . "product_attribute WHERE
id_product = ". (int) $this->product->id;
return Db::getInstance()->executeS($sql);
}
public function getProductStock($id_product_attribute)
{
return StockAvailable::getQuantityAvailableByProduct($this->product->id,
$id_product_attribute, $this->context->shop->id);
}
public function checkDefault()
{
$id_product_attribute = Product::getDefaultAttribute($this->product->id);
$stk = (int) $this->getProductStock($id_product_attribute);
if( $stk > 0){
return true;
}
return false;
}
public function checkAttributeStock( $id_product_attribute)
{
$stk = $this->getProductStock($id_product_attribute);
if( $stk > 0){
return true;
}
return false;
}
public function setDefaultBasedOnStock()
{
if($this->checkDefault()){
return true;
}
$product_atts = $this->getProductAttributes();
if(count($product_atts) >0){
foreach($product_atts as $attri){
if($this->checkAttributeStock($attri['id_product_attribute'])){
$this->product->deleteDefaultAttributes();
$this->product->setDefaultAttribute($attri['id_product_attribute']);
break;
}
}
}
}
/*
end set default based on stock
*/
Then you need to call setDefaultBasedOnStock method inside init Method just after parent::init();
public function init()
{
parent::init();
$this->setDefaultBasedOnStock();
// here is the rest of init code ......
//Do not delete the rest of init code
}
Please do not delete the rest of init() method code, just add this line $this->setDefaultBasedOnStock(); below parent::init();
The best way will be to override productController
Instead of modifying productController class, you can create productController override class inside /override/controllers/front/ folder
class ProductController extends ProductControllerCore {
// add all the methods above
// including the init method
}
// After add override you may need to clear cache if prestashop cache is enabled.