content: // 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.cloudstack.agent.lb.algorithm;
  
  import java.util.ArrayList;
  import java.util.List;
  
  import org.apache.cloudstack.agent.lb.IndirectAgentLBAlgorithm;
  
  public class IndirectAgentLBRoundRobinAlgorithm implements IndirectAgentLBAlgorithm {
  
      private int findRRPivotIndex(final List<String> msList, final List<Long> orderedHostList, final Long hostId) {
          return orderedHostList.indexOf(hostId) % msList.size();
      }
  
      @Override
      public List<String> sort(final List<String> msList, final List<Long> orderedHostList, final Long hostId) {
          if (msList.size() < 2) {
              return msList;
          }
  
          final List<Long> hostList = new ArrayList<>(orderedHostList);
          Long searchId = hostId;
          if (hostId == null) {
              searchId = -1L;
              hostList.add(searchId);
          }
  
          final int pivotIndex = findRRPivotIndex(msList, hostList, searchId);
          final List<String> roundRobin = new ArrayList<>(msList.subList(pivotIndex, msList.size()));
          roundRobin.addAll(msList.subList(0, pivotIndex));
  
          return roundRobin;
      }
  
      @Override
      public String getName() {
          return "roundrobin";
      }
  
      @Override
      public boolean compare(final List<String> msList, final List<String> receivedMsList) {
          return msList != null && receivedMsList != null && msList.equals(receivedMsList);
      }
  
      @Override
      public boolean isHostListNeeded() {
          return true;
      }
  }
  