/**
 * 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.io.FileReader;
import java.io.IOException;
import java.net.InetAddress;
import java.util.Properties;
import java.util.StringTokenizer;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import org.apache.cassandra.config.ConfigurationException;
import org.apache.cassandra.utils.FBUtilities;
import org.apache.cassandra.utils.ResourceWatcher;
import org.apache.cassandra.utils.WrappedRunnable;

/**
 * Used to determine if two IP's are in the same datacenter or on the same rack.
 * <p/>
 * Based on a properties file configuration.
 */
public class PropertyFileSnitch extends AbstractNetworkTopologySnitch
{
    /**
     * A list of properties with keys being host:port and values being datacenter:rack
     */
    private volatile Properties hostProperties;

    /**
     * The default rack property file to be read.
     */
    private static String RACK_PROPERTY_FILENAME = "cassandra-rack.properties";

    /**
     * Reference to the logger.
     */
    private static Logger logger_ = LoggerFactory.getLogger(PropertyFileSnitch.class);

    public PropertyFileSnitch() throws ConfigurationException {
        reloadConfiguration();
        Runnable runnable = new WrappedRunnable()
        {
            protected void runMayThrow() throws ConfigurationException
            {
                reloadConfiguration();
            }
        };
        ResourceWatcher.watch(RACK_PROPERTY_FILENAME, runnable, 60 * 1000);
    }

    /**
     * Get the raw information about an end point
     * 
     * @param endpoint endpoint to process
     * 
     * @return a array of string with the first index being the data center and the second being the rack
     */
    public String[] getEndpointInfo(InetAddress endpoint) {
        String key = endpoint.getHostAddress();
        String value = hostProperties.getProperty(key);
        if (value == null)
        {
            logger_.error("Could not find end point information for {}, will use default.", key);
            value = hostProperties.getProperty("default");
        }
        StringTokenizer st = new StringTokenizer(value, ":");
        if (st.countTokens() < 2)
        {
            logger_.error("Value for " + key + " is invalid: " + value);
            return new String [] {"default", "default"};
        }
        return new String[] {st.nextToken(), st.nextToken()};
    }

    /**
     * Return the data center for which an endpoint resides in
     *  
     * @param endpoint the endpoint to process
     * @return string of data center
     */
    public String getDatacenter(InetAddress endpoint) {
        return getEndpointInfo(endpoint)[0];
    }

    /**
     * Return the rack for which an endpoint resides in
     *  
     * @param endpoint the endpoint to process
     * 
     * @return string of rack
     */
    public String getRack(InetAddress endpoint) {
        return getEndpointInfo(endpoint)[1];
    }

    public void reloadConfiguration() throws ConfigurationException
    {
        hostProperties = resourceToProperties(RACK_PROPERTY_FILENAME);
        clearEndpointCache();
    }

    public static Properties resourceToProperties(String filename) throws ConfigurationException
    {
        String rackPropertyFilename = FBUtilities.resourceToFile(filename);

        Properties localHostProperties;
        try
        {
            localHostProperties = new Properties();
            localHostProperties.load(new FileReader(rackPropertyFilename));
        }
        catch (IOException e)
        {
            throw new ConfigurationException("Unable to load " + rackPropertyFilename, e);
        }
        return localHostProperties;
    }
}