commerce_discounted_product: example implementation for categories

ProductCategoryApplicabilityChecker.php

<?php

namespace Drupal\fp_shop\Applicability;

use Drupal\commerce_discounted_product\Applicability\ApplicabilityCheckerInterface;
use Drupal\commerce_promotion\Entity\PromotionInterface;
use Drupal\commerce_promotion\Plugin\Commerce\PromotionOffer\OrderItemPromotionOfferInterface;
use Drupal\fp_shop\Commerce\CategoryRepositoryInterface;
use Drupal\fp_shop\Commerce\ProductRepositoryInterface;

/**
 * Applicability checker implementation for 'order_item_category' condition.
 */
class ProductCategoryApplicabilityChecker implements ApplicabilityCheckerInterface {

  /**
   * The category repository.
   *
   * @var \Drupal\fp_shop\Commerce\CategoryRepositoryInterface
   */
  protected $categoryRepository;

  /**
   * The product repository.
   *
   * @var \Drupal\fp_shop\Commerce\ProductRepositoryInterface
   */
  protected $productRepository;

  /**
   * Constructs a new ProductCategoryApplicabilityChecker object.
   *
   * @var \Drupal\fp_shop\Commerce\CategoryRepositoryInterface $category_repository
   *   The category repository.
   * @var \Drupal\fp_shop\Commerce\ProductRepositoryInterface $product_repository
   *   The product repository.
   */
  public function __construct(CategoryRepositoryInterface $category_repository, ProductRepositoryInterface $product_repository) {
    $this->categoryRepository = $category_repository;
    $this->productRepository = $product_repository;
  }

  /**
   * {@inheritdoc}
   */
  public function applies(PromotionInterface $promotion) {
    $offer = $promotion->getOffer();
    if (empty($offer) || !($offer instanceof OrderItemPromotionOfferInterface)) {
      return FALSE;
    }
    foreach ($offer->getConditions() as $condition) {
      if ($condition->getPluginId() == 'order_item_category') {
        return TRUE;
      }
    }
    return FALSE;
  }

  /**
   * {@inheritdoc}
   */
  public function determineAffectedProductIds(PromotionInterface $promotion) {
    $results = [];
    $offer = $promotion->getOffer();
    if (empty($offer)) {
      return $results;
    }
    foreach ($offer->getConditions() as $condition) {
      if ($condition->getPluginId() != 'order_item_category') {
        continue;
      }
      $configuration = $condition->getConfiguration();
      $category_ids = $configuration['categories'];
      $children = [];
      foreach ($category_ids as $category_id) {
        $children = array_merge($children, $this->categoryRepository->getChildCategoryIds($category_id));
      }
      $category_ids = array_merge($category_ids, $children);

      $single_result = [];
      foreach ($category_ids as $category_id) {
        $single_result = array_merge($single_result, $this->productRepository->getProductIdsByCategory($category_id, NULL, TRUE));
      }
      $results[] = $single_result;
    }

    $product_ids = [];
    foreach ($results as $result) {
      if ($promotion->getConditionOperator() === 'OR') {
        $product_ids = array_merge($product_ids, $result);
      }
      else {
        if (empty($result)) {
          return [];
        }
        $product_ids = !empty($product_ids) ? array_intersect($product_ids, $result) : $result;
        if (empty($product_ids)) {
          return [];
        }
      }
    }
    return $product_ids;
  }

}