/**
     * Add discount
     */
    if ((double)$this->getSource()->getDiscountAmount()) {
        if ($this->getSource()->getDiscountDescription()) {
            $discountLabel = __('Discount (%1)', $source->getDiscountDescription());
        } else {
            $discountLabel = __('Discount');
        }
        $this->_totals['discount'] = new MagentoFrameworkDataObject(
            [
                'code' => 'discount',
                'field' => 'discount_amount',
                'value' => $source->getDiscountAmount(),
                'label' => $discountLabel,
            ]
        );
    }

class Totals extends MagentoSalesBlockOrderTotals
{

    public function _initTotals() {
        $source = $this->getSource();

        $this->_totals = [];
        $this->_totals['subtotal'] = new MagentoFrameworkDataObject(
            ['code' => 'subtotal', 'value' => $source->getSubtotal(), 'label' => __('Subtotal')]
        );

        /**
         * Add shipping
         */
        if (!$source->getIsVirtual() && ((double)$source->getShippingAmount() || $source->getShippingDescription())) {
            $this->_totals['shipping'] = new MagentoFrameworkDataObject(
                [
                    'code' => 'shipping',
                    'field' => 'shipping_amount',
                    'value' => $this->getSource()->getShippingAmount(),
                    'label' => __('Shipping & Handling'),
                ]
            );
        }

        /**
         * Add discount
         */
        if ((double)$this->getSource()->getDiscountAmount() != 0 OR $this->getSource()->getDiscountDescription() != null) {
            if ($this->getSource()->getDiscountDescription()) {
                $discountLabel = __('Discount (%1)', $source->getDiscountDescription());
            } else {
                $discountLabel = __('Discount');
            }
            $this->_totals['discount'] = new MagentoFrameworkDataObject(
                [
                    'code' => 'discount',
                    'field' => 'discount_amount',
                    'value' => $source->getDiscountAmount(),
                    'label' => $discountLabel,
                ]
            );
        }

        $this->_totals['grand_total'] = new MagentoFrameworkDataObject(
            [
                'code' => 'grand_total',
                'field' => 'grand_total',
                'strong' => true,
                'value' => $source->getGrandTotal(),
                'label' => __('Grand Total'),
            ]
        );

        /**
         * Base grandtotal
         */
        if ($this->getOrder()->isCurrencyDifferent()) {
            $this->_totals['base_grandtotal'] = new MagentoFrameworkDataObject(
                [
                    'code' => 'base_grandtotal',
                    'value' => $this->getOrder()->formatBasePrice($source->getBaseGrandTotal()),
                    'label' => __('Grand Total to be Charged'),
                    'is_formated' => true,
                ]
            );
        }
        return $this;

    }
}

class Totals
{

    public function after_initTotals(
        MagentoSalesBlockOrderTotals $subject,
        $result
    ) {
        if ((double)$subject->getSource()->getDiscountAmount() != 0 OR $subject->getSource()->getDiscountDescription() != null) {
            if ($subject->getSource()->getDiscountDescription()) {
                $discountLabel = __('Offer (%1)', $source->getDiscountDescription());
            } else {
                $discountLabel = __('Offer');
            }
            $subject->_totals['discount'] = new MagentoFrameworkDataObject(
                [
                    'code' => 'discount',
                    'field' => 'discount_amount',
                    'value' => $source->getDiscountAmount(),
                    'label' => $discountLabel,
                ]
            );
        }

        return $subject;
    }
}