Woocommerce - Add Coupon is not deducting totals - php

Question

I am creating my order like so:
$order = wc_create_order();
$product = wc_get_product( $_POST["product"] );
$order->add_product( $product, 1 );
$kupon = new WC_Coupon( $_POST["coupon"] );
$amount = $kupon->get_discount_amount( $product->price );
$order->add_coupon( $_POST["coupon"], $amount, $amount );
$order->calculate_shipping();
$order->calculate_totals();
If you take a closer look, I am adding a coupon code dynamicaly with add_coupon function from WC_Order class. Everythings works perfectly, the order is added to database with correct product, quantites, and ALSO the coupon is added - but the problem is that coupon is not "applied" to the total. It is not deducting the totals price. Here is the image:

Answer 1

While adding a product to an Order, we should pass an argument containing subtotal and total like this:
$args = array(
"totals" => array('subtotal' => $item["price"],
'total' => $item["price"] - $coupon_discount)
);
$order->add_product( $product, 1, $args);
Where $product is Woocommerce product. Hope this helps somebody.

Answer 2

Here is the solution that worked in my case for modifying order line items then applying a discount afterward - $order is a WC_Order object:
$order_total = $order->get_total()
$coupon_code = $this->get_coupon_code( $order );
$coupon = new WC_Coupon( $coupon_code );
$coupon_type = $coupon->discount_type;
$coupon_amount = $coupon->coupon_amount;
$final_discount = 0;
// You must calculate the discount yourself! I have not found a convenient method outside the WC_Cart context to do this for you.
$final_discount = $coupon_amount * ( $order_total / 100 );
$order->add_coupon( $coupon_code, $final_discount, 0 );
$order->set_total( $final_discount );
Here is the method to retrieve the coupon code for a WC_Order object. In my case I know there will never be more then 1 coupon per order so you may want to adjust it to accommodate more:
public function get_coupon_code( $subscription ) {
$coupon_used = '';
if( $subscription->get_used_coupons() ) {
$coupons_count = count( $subscription->get_used_coupons() );
foreach( $subscription->get_used_coupons() as $coupon) {
$coupon_used = $coupon;
break;
}
}
if ( $coupon_used !== '' ) {
return $coupon_used;
} else {
return false;
}
}