code: public function getMainVariationNumber(array $mainVariation, array $variations = [])
      {
          $found = false;
  
          $mainVariationNumber = (string) $mainVariation['id'];
  
          if ($this->configService->get('variation_number_field', 'number') === 'number') {
              $mainVariationNumber = (string) $mainVariation['number'];
          }
  
          foreach ($variations as $variation) {
              if ($variation->getNumber() === $mainVariationNumber) {
                  $found = true;
                  break;
              }
          }
  
          if ($found) {
              $checkActiveMainVariation = json_decode($this->configService->get('check_active_main_variation'));
  
              if (!$checkActiveMainVariation && !$mainVariation['isActive']) {
                  foreach ($variations as $variation) {
                      if ($variation->getActive()) {
                          return $variation->getNumber();
                      }
                  }
              }
  
              return $mainVariationNumber;
          }
  
          foreach ($variations as $variation) {
              if ($variation->getActive()) {
                  return $variation->getNumber();
              }
          }
  
          return $mainVariationNumber;
      }
docs: @param array $mainVariation
  @param array $variations
  
  @return string