/*
 *
 * 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.cassandra.locator;

import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.*;

/**
 * An endpoint snitch tells Cassandra information about network topology that it can use to route
 * requests more efficiently.
 */
public abstract class AbstractNetworkTopologySnitch extends AbstractEndpointSnitch
{
    /**
     * Return the rack for which an endpoint resides in
     * @param endpoint a specified endpoint
     * @return string of rack
     * @throws UnknownHostException
     */
    abstract public String getRack(InetAddress endpoint);

    /**
     * Return the data center for which an endpoint resides in
     * @param endpoint a specified endpoint
     * @return string of data center
     * @throws UnknownHostException
     */
    abstract public String getDatacenter(InetAddress endpoint);

    /**
     * Sorts the <tt>Collection</tt> of node addresses by proximity to the given address
     * @param address the address to sort by proximity to
     * @param addresses the nodes to sort
     * @return a new sorted <tt>List</tt>
     */
    public List<InetAddress> getSortedListByProximity(final InetAddress address, Collection<InetAddress> addresses)
    {
        List<InetAddress> preferred = new ArrayList<InetAddress>(addresses);
        sortByProximity(address, preferred);
        return preferred;
    }

    /**
     * Sorts the <tt>List</tt> of node addresses by proximity to the given address
     * @param address the address to sort the proximity by
     * @param addresses the nodes to sort
     * @return the sorted <tt>List</tt>
     */
    public void sortByProximity(final InetAddress address, List<InetAddress> addresses)
    {
        Collections.sort(addresses, new Comparator<InetAddress>()
        {
            public int compare(InetAddress a1, InetAddress a2)
            {
                   return compareEndpoints(address, a1, a2);
            }
        });
    }

    public int compareEndpoints(InetAddress address, InetAddress a1, InetAddress a2)
    {
        if (address.equals(a1) && !address.equals(a2))
            return -1;
        if (address.equals(a2) && !address.equals(a1))
            return 1;

        String addressRack = getRack(address);
        String a1Rack = getRack(a1);
        String a2Rack = getRack(a2);
        if (addressRack.equals(a1Rack) && !addressRack.equals(a2Rack))
            return -1;
        if (addressRack.equals(a2Rack) && !addressRack.equals(a1Rack))
            return 1;

        String addressDatacenter = getDatacenter(address);
        String a1Datacenter = getDatacenter(a1);
        String a2Datacenter = getDatacenter(a2);
        if (addressDatacenter.equals(a1Datacenter) && !addressDatacenter.equals(a2Datacenter))
            return -1;
        if (addressDatacenter.equals(a2Datacenter) && !addressDatacenter.equals(a1Datacenter))
            return 1;

        return 0;
    }
}