/*

  * #%L

  * LatencyServerSelector.java - mongodb-async-driver - Allanbank Consulting, Inc.

  * %%

  * Copyright (C) 2011 - 2014 Allanbank Consulting, Inc.

  * %%

  * 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.

  * #L%

  */

 package com.allanbank.mongodb.client.state;

 import java.util.ArrayList;

 import java.util.Collections;

 import java.util.List;

 /**

  * LatencyServerSelector provides an implementation of the server selector that

  * uses the server latencies to determine the server to select.

  * 

  * @api.no This class is <b>NOT</b> part of the drivers API. This class may be

  *         mutated in incompatible ways between any two releases of the driver.

  * @copyright 2012-2013, Allanbank Consulting, Inc., All Rights Reserved

  */

 public class LatencyServerSelector implements ServerSelector {

     /** The cluster to choose from. */

     private final Cluster myCluster;

     /** If true then only writable servers should be selected. */

     private final boolean myWritableOnly;

     /**

      * Creates a new LatencyServerSelector.

      * 

      * @param cluster

      *            The cluster to choose from.

      * @param writableOnly

      *            If true then only writable servers should be selected. If

      *            false then any server (writable and not writable) may be

      *            selected.

      */

     public LatencyServerSelector(final Cluster cluster,

             final boolean writableOnly) {

         myCluster = cluster;

         myWritableOnly = writableOnly;

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden to order the servers with the lowest latency first.

      * </p>

      */

     @Override

     public List<Server> pickServers() {

         List<Server> servers;

         if (myWritableOnly) {

             servers = myCluster.getWritableServers();

         }

         else {

             servers = myCluster.getServers();

         }

         // If there are no servers then there is no one to pick.

         if (servers.isEmpty()) {

             return Collections.emptyList();

         }

         // Copy to a list we know we can modify and sort.

         servers = new ArrayList<Server>(servers);

         Collections.sort(servers, ServerLatencyComparator.COMPARATOR);

         return servers;

     }

 }