content: /**
   * JBoss, Home of Professional Open Source
   * Copyright Red Hat, Inc., and individual contributors.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   * 	http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.jboss.aerogear.unifiedpush.message.token;
  
  import com.google.android.gcm.server.Constants;
  import org.jboss.aerogear.unifiedpush.message.Criteria;
  
  import java.util.List;
  import java.util.Set;
  import java.util.TreeSet;
  import java.util.stream.Collectors;
  
  public final class TokenLoaderUtils {
  
      private TokenLoaderUtils () {
          // no-op
      }
  
      /**
       * Extracts FCM topic names out of a given Criteria object (e.g. /topics/nameOfcategory).
       * If the Criteria is empty, the given variant ID will be returned as topic name (/topics/variantID)
       *
       * @param criteria the push message filter criteria
       * @param variantID variant ID, used as global fallback FCM topic name
       *
       * @return FCM topic names for the given push message criteria filter.
       */
      public static Set<String> extractFCMTopics(final Criteria criteria, final String variantID) {
          final Set<String> topics = new TreeSet<>();
  
          if (isEmptyCriteria(criteria)) {
              // use the variant 'convenience' topic
              topics.add(Constants.TOPIC_PREFIX + variantID);
  
          } else if (isCategoryOnlyCriteria(criteria)) {
              // use the given categories
              topics.addAll(criteria.getCategories().stream()
                      .map(category -> Constants.TOPIC_PREFIX + category)
                      .collect(Collectors.toList()));
          }
          return topics;
      }
  
      /**
       * Helper method to check if only categories are applied. Useful in FCM land, where we use topics
       */
      public static boolean isCategoryOnlyCriteria(final Criteria criteria) {
  
          return  isEmpty(criteria.getAliases()) &&      // we are not subscribing to alias topic (yet)
                  isEmpty(criteria.getDeviceTypes()) &&  // we are not subscribing to device type topic (yet)
                  !isEmpty(criteria.getCategories());    // BUT! categories are mapped to topics
      }
  
      /**
       * Helper method to check if all criteria are empty. Useful in FCM land, where we use topics.
       */
      public static boolean isEmptyCriteria(final Criteria criteria) {
  
          return  isEmpty(criteria.getAliases()) &&
                  isEmpty(criteria.getDeviceTypes()) &&
                  isEmpty(criteria.getCategories());
      }
  
      /**
       * Helper method to check if we should do FCM topic request.
       */
      public static boolean isFCMTopicRequest(final Criteria criteria) {
          return isEmptyCriteria(criteria) || isCategoryOnlyCriteria(criteria);
      }
  
      /**
       * Checks if the list is empty, and not null
       */
      private static boolean isEmpty(List list) {
          return list == null || list.isEmpty();
      }
  }
  