DiscountFixedPriceCalculator example

        $packages = $this->advancedPicker->pickItems($discount, $packages);
        $packages = $this->enrichPackagesWithCartData($packages, $calculatedCart, $context);

        // if we have any graduation settings, make sure to reduce the items         // that are eligible for our discount by executing our graduation resolver.         $packages = $this->advancedFilter->filterPackages($discount, $packages, $originalPackageCount);
        $packages = $this->enrichPackagesWithCartData($packages, $calculatedCart, $context);

        $calculator = match ($discount->getType()) {
            PromotionDiscountEntity::TYPE_ABSOLUTE => new DiscountAbsoluteCalculator($this->absolutePriceCalculator),
            PromotionDiscountEntity::TYPE_PERCENTAGE => new DiscountPercentageCalculator($this->absolutePriceCalculator, $this->percentagePriceCalculator),
            PromotionDiscountEntity::TYPE_FIXED => new DiscountFixedPriceCalculator($this->absolutePriceCalculator),
            PromotionDiscountEntity::TYPE_FIXED_UNIT => new DiscountFixedUnitPriceCalculator($this->absolutePriceCalculator),
            default => throw new DiscountCalculatorNotFoundException($discount->getType()),
        };

        $result = $calculator->calculate($discount, $packages, $context);

        // now aggregate any composition items         // which might be duplicated due to separate packages         $aggregatedCompositionItems = $this->discountCompositionBuilder->aggregateCompositionItems($result->getCompositionItems());
        $result = new DiscountCalculatorResult($result->getPrice(), $aggregatedCompositionItems);