code: private function extractMapping($mapping, $countryCode)
      {
          $final = null;
          $extractMapping = json_decode($mapping, true);
          if (!$extractMapping) {
              try {
                  $extractMapping = unserialize($mapping); // @codingStandardsIgnoreLine
              } catch (\Exception $e) {
                  $extractMapping = [];
              }
          }
  
          if (is_array($extractMapping)) {
              $countryId = 'country_id';
              $key = 'store_id';
              // check for direct match
              foreach ($extractMapping as $map) {
                  if (is_array($map) &&
                      isset($map[$countryId]) &&
                      strtolower(str_replace(' ', '', $map[$countryId])) == strtolower($countryCode)) {
                      if (isset($map[$key])) {
                          return (int)$map[$key];
                      }
                  } elseif (is_array($map) &&
                      isset($map[$countryId]) &&
                      $map[$countryId] == '*' &&
                      isset($map[$key]) &&
                      $final === null) {
                      // check for wildcard
                      $final = (int)$map[$key];
                  }
              }
          }
          return $final;
      }
docs: Filter country code mapping by priority
  
  @param $mapping
  @param $countryCode
  @return int|null