Issue #2980195 by mglaman, bojanz: Fixed order offers should reduce each order item

Author: bojanz

modules/promotion/src/Plugin/Commerce/PromotionOffer/OrderFixedAmountOff.php

@@ -3,12 +3,17 @@
 namespace Drupal\commerce_promotion\Plugin\Commerce\PromotionOffer;
 
 use Drupal\commerce_order\Adjustment;
+use Drupal\commerce_order\PriceSplitterInterface;
+use Drupal\commerce_price\RounderInterface;
 use Drupal\commerce_promotion\Entity\PromotionInterface;
 use Drupal\Core\Entity\EntityInterface;
+use Symfony\Component\DependencyInjection\ContainerInterface;
 
 /**
  * Provides the fixed amount off offer for orders.
  *
+ * The discount is split between order items, to simplify VAT taxes and refunds.
+ *
  * @CommercePromotionOffer(
  *   id = "order_fixed_amount_off",
  *   label = @Translation("Fixed amount off the order subtotal"),
@@ -17,6 +22,46 @@
  */
 class OrderFixedAmountOff extends FixedAmountOffBase {
 
+  /**
+   * The price splitter.
+   *
+   * @var \Drupal\commerce_order\PriceSplitterInterface
+   */
+  protected $splitter;
+
+  /**
+   * Constructs a new OrderFixedAmountOff object.
+   *
+   * @param array $configuration
+   *   A configuration array containing information about the plugin instance.
+   * @param string $plugin_id
+   *   The pluginId for the plugin instance.
+   * @param mixed $plugin_definition
+   *   The plugin implementation definition.
+   * @param \Drupal\commerce_price\RounderInterface $rounder
+   *   The rounder.
+   * @param \Drupal\commerce_order\PriceSplitterInterface $splitter
+   *   The splitter.
+   */
+  public function __construct(array $configuration, $plugin_id, $plugin_definition, RounderInterface $rounder, PriceSplitterInterface $splitter) {
+    parent::__construct($configuration, $plugin_id, $plugin_definition, $rounder);
+
+    $this->splitter = $splitter;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
+    return new static(
+      $configuration,
+      $plugin_id,
+      $plugin_definition,
+      $container->get('commerce_price.rounder'),
+      $container->get('commerce_order.price_splitter')
+    );
+  }
+
   /**
    * {@inheritdoc}
    */
@@ -25,23 +70,29 @@ public function apply(EntityInterface $entity, PromotionInterface $promotion) {
     /** @var \Drupal\commerce_order\Entity\OrderInterface $order */
     $order = $entity;
     $subtotal_price = $order->getSubTotalPrice();
-    $adjustment_amount = $this->getAmount();
-    if ($subtotal_price->getCurrencyCode() != $adjustment_amount->getCurrencyCode()) {
+    $amount = $this->getAmount();
+    if ($subtotal_price->getCurrencyCode() != $amount->getCurrencyCode()) {
       return;
     }
     // The promotion amount can't be larger than the subtotal, to avoid
     // potentially having a negative order total.
-    if ($adjustment_amount->greaterThan($subtotal_price)) {
-      $adjustment_amount = $subtotal_price;
+    if ($amount->greaterThan($subtotal_price)) {
+      $amount = $subtotal_price;
     }
+    // Split the amount between order items.
+    $amounts = $this->splitter->split($order, $amount);
 
-    $order->addAdjustment(new Adjustment([
-      'type' => 'promotion',
-      // @todo Change to label from UI when added in #2770731.
-      'label' => t('Discount'),
-      'amount' => $adjustment_amount->multiply('-1'),
-      'source_id' => $promotion->id(),
-    ]));
+    foreach ($order->getItems() as $order_item) {
+      if (isset($amounts[$order_item->id()])) {
+        $order_item->addAdjustment(new Adjustment([
+          'type' => 'promotion',
+          // @todo Change to label from UI when added in #2770731.
+          'label' => t('Discount'),
+          'amount' => $amounts[$order_item->id()]->multiply('-1'),
+          'source_id' => $promotion->id(),
+        ]));
+      }
+    }
   }
 
 }

modules/promotion/src/Plugin/Commerce/PromotionOffer/OrderPercentageOff.php

@@ -70,7 +70,7 @@ public function apply(EntityInterface $entity, PromotionInterface $promotion) {
     /** @var \Drupal\commerce_order\Entity\OrderInterface $order */
     $order = $entity;
     $percentage = $this->getPercentage();
-    // Calculate the order-level discount and split it across order items.
+    // Calculate the order-level discount and split it between order items.
     $amount = $order->getSubtotalPrice()->multiply($percentage);
     $amount = $this->rounder->round($amount);
     $amounts = $this->splitter->split($order, $amount, $percentage);

modules/promotion/tests/src/Kernel/PromotionOfferTest.php

@@ -170,19 +170,39 @@ public function testOrderFixedAmountOff() {
     $this->order->state = 'draft';
     $this->order->save();
     $this->order = $this->reloadEntity($this->order);
+    $order_items = $this->order->getItems();
+    $order_item = reset($order_items);
+    $adjustments = $order_item->getAdjustments();
+    $this->assertEquals(1, count($adjustments));
+    /** @var \Drupal\commerce_order\Adjustment $adjustment */
+    $adjustment = reset($adjustments);
 
     // Offer amount larger than the order subtotal.
-    $this->assertEquals(1, count($this->order->getAdjustments()));
-    $this->assertEquals(new Price('-20.00', 'USD'), $this->order->getAdjustments()[0]->getAmount());
+    $this->assertEquals(0, count($this->order->getAdjustments()));
+    $this->assertEquals(1, count($order_item->getAdjustments()));
+    $this->assertEquals(new Price('20.00', 'USD'), $order_item->getTotalPrice());
+    $this->assertEquals(new Price('0.00', 'USD'), $order_item->getAdjustedTotalPrice());
+    $this->assertEquals(new Price('-20.00', 'USD'), $adjustment->getAmount());
     $this->assertEquals(new Price('0.00', 'USD'), $this->order->getTotalPrice());
 
     // Offer amount smaller than the order subtotal.
     $order_item->setQuantity(2);
     $order_item->save();
     $this->order->save();
     $this->order = $this->reloadEntity($this->order);
-    $this->assertEquals(1, count($this->order->getAdjustments()));
-    $this->assertEquals(new Price('-25.00', 'USD'), $this->order->getAdjustments()[0]->getAmount());
+    $order_items = $this->order->getItems();
+    $order_item = reset($order_items);
+    $adjustments = $order_item->getAdjustments();
+    $this->assertEquals(1, count($adjustments));
+    /** @var \Drupal\commerce_order\Adjustment $adjustment */
+    $adjustment = reset($adjustments);
+
+    // Offer amount larger than the order subtotal.
+    $this->assertEquals(0, count($this->order->getAdjustments()));
+    $this->assertEquals(1, count($order_item->getAdjustments()));
+    $this->assertEquals(new Price('40.00', 'USD'), $order_item->getTotalPrice());
+    $this->assertEquals(new Price('15.00', 'USD'), $order_item->getAdjustedTotalPrice());
+    $this->assertEquals(new Price('-25.00', 'USD'), $adjustment->getAmount());
     $this->assertEquals(new Price('15.00', 'USD'), $this->order->getTotalPrice());
   }