Code-Snippets-Functions/Execute a function on a child site/WooCommerce/double-discount-on-sale-products-with-coupon.txt

function filter_woocommerce_coupon_get_discount_amount( $discount, $price_to_discount , $cart_item, $single, $coupon ) {    
    // Only apply for this coupon
    if ( $coupon->get_code() == 'doublediscount' ) {
        // On sale
        if ( $cart_item['data']->is_on_sale() ) {
            // Regular price
            $cart_item_regular_price = $cart_item['data']->get_regular_price();
            
            // Sale price
            $cart_item_sale_price = $cart_item['data']->get_sale_price();
            
            // Calculate the percentage difference
            $cart_item_diff = $cart_item_regular_price - $cart_item_sale_price;
            $cart_item_percentage = round( $cart_item_diff / $cart_item_regular_price * 100, 0 );
            
            // Get maximum added discount
            $max_added_discount = $coupon->get_amount();
            
            // Less than maximum added discount
            if ( $cart_item_percentage < $max_added_discount ) {
                $discount = round( ( $price_to_discount * $cart_item_percentage ) / 100, 0 );
            }
        } else {
            $discount = 0;
        }
    }

    return $discount;
}
add_filter( 'woocommerce_coupon_get_discount_amount', 'filter_woocommerce_coupon_get_discount_amount', 10, 5 );