/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you 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.apache.maven.settings.merge;
  
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  import java.util.stream.Collectors;
  import java.util.stream.Stream;
  import org.apache.maven.api.settings.IdentifiableBase;
  import org.apache.maven.api.settings.Settings;
  import org.codehaus.plexus.util.StringUtils;
  
  /**
   * @author <a href="mailto:vincent.siveton@gmail.com">Vincent Siveton</a>
   * @author Benjamin Bentmann
   */
  public class MavenSettingsMerger {
  
      /**
       * @param dominant
       * @param recessive
       * @param recessiveSourceLevel
       */
      public Settings merge(Settings dominant, Settings recessive, String recessiveSourceLevel) {
          if (dominant == null) {
              return recessive;
          } else if (recessive == null) {
              return dominant;
          }
  
          recessive.setSourceLevel(recessiveSourceLevel);
  
          Settings.Builder merged = Settings.newBuilder(dominant);
  
          List<String> dominantActiveProfiles = dominant.getActiveProfiles();
          List<String> recessiveActiveProfiles = recessive.getActiveProfiles();
          List<String> mergedActiveProfiles = Stream.of(dominantActiveProfiles, recessiveActiveProfiles)
                  .flatMap(Collection::stream)
                  .distinct()
                  .collect(Collectors.toList());
          merged.activeProfiles(mergedActiveProfiles);
  
          List<String> dominantPluginGroupIds = dominant.getPluginGroups();
          List<String> recessivePluginGroupIds = recessive.getPluginGroups();
          List<String> mergedPluginGroupIds = Stream.of(dominantPluginGroupIds, recessivePluginGroupIds)
                  .flatMap(Collection::stream)
                  .distinct()
                  .collect(Collectors.toList());
          merged.pluginGroups(mergedPluginGroupIds);
  
          String localRepository = StringUtils.isEmpty(dominant.getLocalRepository())
                  ? recessive.getLocalRepository()
                  : dominant.getLocalRepository();
          merged.localRepository(localRepository);
  
          merged.mirrors(shallowMergeById(dominant.getMirrors(), recessive.getMirrors(), recessiveSourceLevel));
          merged.servers(shallowMergeById(dominant.getServers(), recessive.getServers(), recessiveSourceLevel));
          merged.proxies(shallowMergeById(dominant.getProxies(), recessive.getProxies(), recessiveSourceLevel));
          merged.profiles(shallowMergeById(dominant.getProfiles(), recessive.getProfiles(), recessiveSourceLevel));
  
          return merged.build();
      }
  
      /**
       * @param dominant
       * @param recessive
       * @param recessiveSourceLevel
       */
      private static <T extends IdentifiableBase> List<T> shallowMergeById(
              List<T> dominant, List<T> recessive, String recessiveSourceLevel) {
          Set<String> dominantIds = dominant.stream().map(IdentifiableBase::getId).collect(Collectors.toSet());
          final List<T> merged = new ArrayList<>(dominant.size() + recessive.size());
          merged.addAll(dominant);
          for (T identifiable : recessive) {
              if (!dominantIds.contains(identifiable.getId())) {
                  identifiable.setSourceLevel(recessiveSourceLevel);
                  merged.add(identifiable);
              }
          }
         return merged;
     }
 
     /**
      * @param identifiables
      * @return a map
      */
     private static <T extends IdentifiableBase> Map<String, T> mapById(List<T> identifiables) {
         Map<String, T> byId = new HashMap<>();
 
         for (T identifiable : identifiables) {
             byId.put(identifiable.getId(), identifiable);
         }
 
         return byId;
     }
 }