/*
    * 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.shardingsphere.sharding.route.engine.type.broadcast;
  
  import com.google.common.collect.Sets;
  import org.apache.shardingsphere.infra.route.context.RouteContext;
  import org.apache.shardingsphere.infra.route.context.RouteMapper;
  import org.apache.shardingsphere.infra.route.context.RouteUnit;
  import org.apache.shardingsphere.sharding.route.engine.type.ShardingRouteEngine;
  import org.apache.shardingsphere.sharding.rule.ShardingRule;
  import org.apache.shardingsphere.sharding.rule.ShardingTable;
  
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.LinkedList;
  import java.util.Set;
  import java.util.concurrent.ThreadLocalRandom;
  
  /**
   * Sharding data source group broadcast routing engine.
   */
  public final class ShardingDataSourceGroupBroadcastRoutingEngine implements ShardingRouteEngine {
      
      @Override
      public RouteContext route(final ShardingRule shardingRule) {
          RouteContext result = new RouteContext();
          Collection<Set<String>> broadcastDataSourceGroup = getBroadcastDataSourceGroup(getDataSourceGroup(shardingRule));
          for (Set<String> each : broadcastDataSourceGroup) {
              String dataSourceName = getRandomDataSourceName(each);
              result.getRouteUnits().add(new RouteUnit(new RouteMapper(dataSourceName, dataSourceName), Collections.emptyList()));
          }
          return result;
      }
      
      private Collection<Set<String>> getBroadcastDataSourceGroup(final Collection<Set<String>> dataSourceGroup) {
          Collection<Set<String>> result = new LinkedList<>();
          for (Set<String> each : dataSourceGroup) {
              result = getCandidateDataSourceGroup(result, each);
          }
          return result;
      }
      
      private Collection<Set<String>> getDataSourceGroup(final ShardingRule shardingRule) {
          Collection<Set<String>> result = new LinkedList<>();
          for (ShardingTable each : shardingRule.getShardingTables().values()) {
              result.add(each.getDataNodeGroups().keySet());
          }
          return result;
      }
      
      private Collection<Set<String>> getCandidateDataSourceGroup(final Collection<Set<String>> dataSourceSetGroup, final Set<String> compareSet) {
          Collection<Set<String>> result = new LinkedList<>();
          if (dataSourceSetGroup.isEmpty()) {
              result.add(compareSet);
              return result;
          }
          Set<String> intersections;
          boolean hasIntersection = false;
          for (Set<String> each : dataSourceSetGroup) {
              intersections = Sets.intersection(each, compareSet);
              if (intersections.isEmpty()) {
                  result.add(each);
              } else {
                  result.add(intersections);
                  hasIntersection = true;
              }
          }
          if (!hasIntersection) {
              result.add(compareSet);
          }
          return result;
      }
      
      private String getRandomDataSourceName(final Collection<String> dataSourceNames) {
          return new ArrayList<>(dataSourceNames).get(ThreadLocalRandom.current().nextInt(dataSourceNames.size()));
      }
  }