feat: add discount_percentage attribute to product export feed

Model/Write/Products/CollectionDecorator/DiscountPercentage.php

@@ -0,0 +1,57 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tweakwise\Magento2TweakwiseExport\Model\Write\Products\CollectionDecorator;
+
+use Magento\Bundle\Model\Product\Type as BundleType;
+use Tweakwise\Magento2TweakwiseExport\Exception\InvalidArgumentException;
+use Tweakwise\Magento2TweakwiseExport\Model\Write\Products\Collection;
+use Tweakwise\Magento2TweakwiseExport\Model\Write\Products\ExportEntity;
+
+class DiscountPercentage implements DecoratorInterface
+{
+    private const ATTRIBUTE_NAME = 'discount_percentage';
+
+    /**
+     * Decorate items with a computed discount_percentage attribute.
+     * Skipped for bundle products (pricing too complex) and products with no discount.
+     *
+     * @param Collection $collection
+     */
+    public function decorate(Collection $collection): void
+    {
+        foreach ($collection as $entity) {
+            if ($entity->getTypeId() === BundleType::TYPE_CODE) {
+                continue;
+            }
+
+            $discount = $this->calculateDiscount($entity);
+            if ($discount <= 0) {
+                continue;
+            }
+
+            $entity->addAttribute(self::ATTRIBUTE_NAME, $discount);
+        }
+    }
+
+    /**
+     * @param ExportEntity $entity
+     * @return int
+     */
+    private function calculateDiscount(ExportEntity $entity): int
+    {
+        try {
+            $regularPrice = (float)$entity->getAttribute('regular_price', false);
+            $finalPrice = (float)$entity->getAttribute('final_price', false);
+        } catch (InvalidArgumentException $e) {
+            return 0;
+        }
+
+        if ($regularPrice <= 0.00001 || $finalPrice >= $regularPrice) {
+            return 0;
+        }
+
+        return (int)round(($regularPrice - $finalPrice) / $regularPrice * 100);
+    }
+}

Model/Write/Products/CollectionDecorator/Price.php

@@ -87,6 +87,7 @@ public function decorate(Collection|PriceCollection $collection): void
 
             $row = $this->applyCombinedPrices($row, $product, $store);
             $row = $this->applyPriceFields($row, $priceFields);
+            $row['regular_price'] = (float) $row['price'];
             $row['price'] = $this->getPriceValue($row, $priceFields);
 
             $collection->get($entityId)->setFromArray($row);

etc/di.xml

@@ -81,6 +81,7 @@
                 <item name="stock_data" xsi:type="object">Tweakwise\Magento2TweakwiseExport\Model\Write\Products\CollectionDecorator\StockData</item>
                 <item name="children_attributes" xsi:type="object">Tweakwise\Magento2TweakwiseExport\Model\Write\Products\CollectionDecorator\ChildrenAttributes</item>
                 <item name="price" xsi:type="object">Tweakwise\Magento2TweakwiseExport\Model\Write\Products\CollectionDecorator\Price</item>
+                <item name="discount_percentage" xsi:type="object">Tweakwise\Magento2TweakwiseExport\Model\Write\Products\CollectionDecorator\DiscountPercentage</item>
                 <item name="website_link" xsi:type="object">Tweakwise\Magento2TweakwiseExport\Model\Write\Products\CollectionDecorator\WebsiteLink</item>
                 <item name="review" xsi:type="object">Tweakwise\Magento2TweakwiseExport\Model\Write\Products\CollectionDecorator\Review</item>
             </argument>
@@ -104,6 +105,7 @@
             <argument name="collectionDecorators" xsi:type="array">
                 <item name="children" xsi:type="object">Tweakwise\Magento2TweakwiseExport\Model\Write\Products\CollectionDecorator\Children</item>
                 <item name="price" xsi:type="object">Tweakwise\Magento2TweakwiseExport\Model\Write\Products\CollectionDecorator\Price</item>
+                <item name="discount_percentage" xsi:type="object">Tweakwise\Magento2TweakwiseExport\Model\Write\Products\CollectionDecorator\DiscountPercentage</item>
                 <item name="website_link" xsi:type="object">Tweakwise\Magento2TweakwiseExport\Model\Write\Products\CollectionDecorator\WebsiteLink</item>
             </argument>
         </arguments>