<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Event/etc/events.xsd">
     <event name="salesrule_validator_process">
        <observer name="custom_cart_rules" instance="AlmusbahSendSmsObserverCustomCartPriceRules" />
    </event>
</config>

}

/**
 *
 * @param MagentoFrameworkEventObserver $observer
 * @return void
 */
public function execute(MagentoFrameworkEventObserver $observer) {

    $result = $observer->getEvent()->getResult();
    $item = $observer->getEvent()->getItem();
    $rule = $observer->getEvent()->getRule();
    $address = $observer->getEvent()->getAddress();
    $qty = $item->getQty();

    if ($rule->getData('name') == 'Buy 2 get 1 free'):

            // overriding magento rules here and updating Almusbah Offer
            $result->setAmount(0)
                ->setBaseAmount(0)
                ->setOriginalAmount(0)
                ->setBaseOriginalAmount(0);

            $item->setDiscountPercent(0);


        $products = [];
        $z = 0;
        $totalQty = 0;
        $dA = 0;
        foreach ($address->getAllItems() as $q):

            $validate = $rule->getActions()->validate($q);

            if ($validate):
                $products[$z]['sku'] = $q->getData('sku');
                $products[$z]['qty'] = $q->getData('qty');
                $totalQty += $q->getData('qty');
                $products[$z]['totalQty'] = $totalQty;
                $freeQty = (int) ($totalQty / 3);
                $products[$z]['freeQty'] = $freeQty;
                if ($products[$z]['freeQty'] > 0):
                    $products[$z]['applyDiscount'] = 1;
                    $dicountPercent = 100;
                    $dA = ($products[$z]['freeQty'] * $q->getData('price'));
                    $products[$z]['discountAmount'] = $dA;
                    $totalQty -= 3*$products[$z]['freeQty']; // appying on each 3 items
                endif;
                $z++;
            endif;
        endforeach;
        //echo '<pre>';print_r($products);
        $chkCurrentSku = $item->getSku();

        foreach ($products as $p):
            if(isset($p['applyDiscount']) && !empty($p['applyDiscount']) && $chkCurrentSku == $p['sku']):
                $discountAmount = $p['discountAmount'];
                $fullDiscount = 100;
                $item->setDiscountPercent($fullDiscount);
                $this->almusbahBuy2Get1Offer($discountAmount,$result);
            endif;
        endforeach;

    endif;


}

public function almusbahBuy2Get1Offer($discountAmount, $result) {

               $result->setAmount($discountAmount)
                    ->setBaseAmount($discountAmount)
                    ->setOriginalAmount($discountAmount)
                    ->setBaseOriginalAmount($discountAmount);
        }

}