Ignore taxes and fees for free orders (#754)

Author: daveearley

backend/app/DomainObjects/ProductPriceDomainObject.php

@@ -113,4 +113,9 @@ public function getOffSaleReason(): ?string
     {
         return $this->offSaleReason;
     }
+
+    public function isFree(): bool
+    {
+        return $this->getPrice() === 0.00;
+    }
 }

backend/app/Services/Domain/Order/OrderItemProcessingService.php

@@ -19,13 +19,13 @@
 use Illuminate\Support\Collection;
 use Symfony\Component\Routing\Exception\ResourceNotFoundException;
 
-readonly class OrderItemProcessingService
+class OrderItemProcessingService
 {
     public function __construct(
-        private OrderRepositoryInterface    $orderRepository,
-        private ProductRepositoryInterface  $productRepository,
-        private TaxAndFeeCalculationService $taxCalculationService,
-        private ProductPriceService         $productPriceService,
+        private readonly OrderRepositoryInterface    $orderRepository,
+        private readonly ProductRepositoryInterface  $productRepository,
+        private readonly TaxAndFeeCalculationService $taxCalculationService,
+        private readonly ProductPriceService         $productPriceService,
     )
     {
     }

backend/app/Services/Domain/Product/ProductFilterService.php

@@ -162,12 +162,15 @@ private function filterProduct(
 
     private function processProductPrice(ProductDomainObject $product, ProductPriceDomainObject $price): void
     {
-        $taxAndFees = $this->taxCalculationService
-            ->calculateTaxAndFeesForProductPrice($product, $price);
-
-        $price
-            ->setTaxTotal(Currency::round($taxAndFees->taxTotal))
-            ->setFeeTotal(Currency::round($taxAndFees->feeTotal));
+        // If the product is free of charge, we don't charge service fees or taxes
+        if (!$price->isFree()) {
+            $taxAndFees = $this->taxCalculationService
+                ->calculateTaxAndFeesForProductPrice($product, $price);
+
+            $price
+                ->setTaxTotal(Currency::round($taxAndFees->taxTotal))
+                ->setFeeTotal(Currency::round($taxAndFees->feeTotal));
+        }
 
         $price->setIsAvailable($this->getPriceAvailability($price, $product));
     }

backend/app/Services/Domain/Tax/TaxAndFeeCalculationService.php

@@ -3,9 +3,9 @@
 namespace HiEvents\Services\Domain\Tax;
 
 use HiEvents\DomainObjects\Enums\TaxCalculationType;
-use HiEvents\DomainObjects\TaxAndFeesDomainObject;
 use HiEvents\DomainObjects\ProductDomainObject;
 use HiEvents\DomainObjects\ProductPriceDomainObject;
+use HiEvents\DomainObjects\TaxAndFeesDomainObject;
 use HiEvents\Services\Domain\Tax\DTO\TaxCalculationResponse;
 use InvalidArgumentException;
 
@@ -49,6 +49,13 @@ public function calculateTaxAndFeesForProduct(
 
     private function calculateFee(TaxAndFeesDomainObject $taxOrFee, float $price, int $quantity): float
     {
+        // We do not charge a tax or fee on items which are free of charge
+        if ($price === 0.00) {
+            $this->taxRollupService->addToRollUp($taxOrFee, 0);
+
+            return 0.00;
+        }
+
         $amount = match ($taxOrFee->getCalculationType()) {
             TaxCalculationType::FIXED->name => $taxOrFee->getRate(),
             TaxCalculationType::PERCENTAGE->name => ($price * $taxOrFee->getRate()) / 100,