/**
 *
 * 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.hadoop.hbase.client;

import java.io.Closeable;
import java.io.IOException;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.net.InetAddress;
import java.net.NetworkInterface;
import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.List;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.ClusterMetrics;
import org.apache.hadoop.hbase.ClusterMetricsBuilder;
import org.apache.hadoop.hbase.HBaseInterfaceAudience;
import org.apache.hadoop.hbase.HConstants;
import org.apache.hadoop.hbase.ServerName;
import org.apache.hadoop.hbase.util.Addressing;
import org.apache.hadoop.hbase.util.ExceptionUtil;
import org.apache.hadoop.hbase.util.Threads;
import org.apache.yetus.audience.InterfaceAudience;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import org.apache.hbase.thirdparty.io.netty.bootstrap.Bootstrap;
import org.apache.hbase.thirdparty.io.netty.buffer.ByteBufInputStream;
import org.apache.hbase.thirdparty.io.netty.channel.ChannelHandlerContext;
import org.apache.hbase.thirdparty.io.netty.channel.ChannelOption;
import org.apache.hbase.thirdparty.io.netty.channel.EventLoopGroup;
import org.apache.hbase.thirdparty.io.netty.channel.SimpleChannelInboundHandler;
import org.apache.hbase.thirdparty.io.netty.channel.nio.NioEventLoopGroup;
import org.apache.hbase.thirdparty.io.netty.channel.socket.DatagramChannel;
import org.apache.hbase.thirdparty.io.netty.channel.socket.DatagramPacket;
import org.apache.hbase.thirdparty.io.netty.channel.socket.nio.NioDatagramChannel;

import org.apache.hadoop.hbase.shaded.protobuf.generated.ClusterStatusProtos;

/**
 * A class that receives the cluster status, and provide it as a set of service to the client.
 * Today, manages only the dead server list.
 * The class is abstract to allow multiple implementations, from ZooKeeper to multicast based.
 */
@InterfaceAudience.Private
class ClusterStatusListener implements Closeable {
  private static final Logger LOG = LoggerFactory.getLogger(ClusterStatusListener.class);
  private final List<ServerName> deadServers = new ArrayList<>();
  protected final DeadServerHandler deadServerHandler;
  private final Listener listener;

  /**
   * The implementation class to use to read the status.
   */
  public static final String STATUS_LISTENER_CLASS = "hbase.status.listener.class";
  public static final Class<? extends Listener> DEFAULT_STATUS_LISTENER_CLASS =
      MulticastListener.class;

  /**
   * Class to be extended to manage a new dead server.
   */
  public interface DeadServerHandler {

    /**
     * Called when a server is identified as dead. Called only once even if we receive the
     * information multiple times.
     *
     * @param sn - the server name
     */
    void newDead(ServerName sn);
  }


  /**
   * The interface to be implemented by a listener of a cluster status event.
   */
  interface Listener extends Closeable {
    /**
     * Called to close the resources, if any. Cannot throw an exception.
     */
    @Override
    void close();

    /**
     * Called to connect.
     *
     * @param conf Configuration to use.
     * @throws IOException if failing to connect
     */
    void connect(Configuration conf) throws IOException;
  }

  public ClusterStatusListener(DeadServerHandler dsh, Configuration conf,
                               Class<? extends Listener> listenerClass) throws IOException {
    this.deadServerHandler = dsh;
    try {
      Constructor<? extends Listener> ctor =
          listenerClass.getConstructor(ClusterStatusListener.class);
      this.listener = ctor.newInstance(this);
    } catch (InstantiationException e) {
      throw new IOException("Can't create listener " + listenerClass.getName(), e);
    } catch (IllegalAccessException e) {
      throw new IOException("Can't create listener " + listenerClass.getName(), e);
    } catch (NoSuchMethodException e) {
      throw new IllegalStateException();
    } catch (InvocationTargetException e) {
      throw new IllegalStateException();
    }

    this.listener.connect(conf);
  }

  /**
   * Acts upon the reception of a new cluster status.
   *
   * @param ncs the cluster status
   */
  public void receive(ClusterMetrics ncs) {
    if (ncs.getDeadServerNames() != null) {
      for (ServerName sn : ncs.getDeadServerNames()) {
        if (!isDeadServer(sn)) {
          LOG.info("There is a new dead server: " + sn);
          deadServers.add(sn);
          if (deadServerHandler != null) {
            deadServerHandler.newDead(sn);
          }
        }
      }
    }
  }

  @Override
  public void close() {
    listener.close();
  }

  /**
   * Check if we know if a server is dead.
   *
   * @param sn the server name to check.
   * @return true if we know for sure that the server is dead, false otherwise.
   */
  public boolean isDeadServer(ServerName sn) {
    if (sn.getStartcode() <= 0) {
      return false;
    }

    for (ServerName dead : deadServers) {
      if (dead.getStartcode() >= sn.getStartcode() &&
          dead.getPort() == sn.getPort() &&
          dead.getHostname().equals(sn.getHostname())) {
        return true;
      }
    }

    return false;
  }


  /**
   * An implementation using a multicast message between the master & the client.
   */
  @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.CONFIG)
  class MulticastListener implements Listener {
    private DatagramChannel channel;
    private final EventLoopGroup group = new NioEventLoopGroup(
        1, Threads.newDaemonThreadFactory("hbase-client-clusterStatusListener"));

    public MulticastListener() {
    }

    @Override
    public void connect(Configuration conf) throws IOException {

      String mcAddress = conf.get(HConstants.STATUS_MULTICAST_ADDRESS,
          HConstants.DEFAULT_STATUS_MULTICAST_ADDRESS);
      String bindAddress = conf.get(HConstants.STATUS_MULTICAST_BIND_ADDRESS,
        HConstants.DEFAULT_STATUS_MULTICAST_BIND_ADDRESS);
      int port = conf.getInt(HConstants.STATUS_MULTICAST_PORT,
          HConstants.DEFAULT_STATUS_MULTICAST_PORT);
      String niName = conf.get(HConstants.STATUS_MULTICAST_NI_NAME);

      InetAddress ina;
      try {
        ina = InetAddress.getByName(mcAddress);
      } catch (UnknownHostException e) {
        close();
        throw new IOException("Can't connect to " + mcAddress, e);
      }

      try {
        Bootstrap b = new Bootstrap();
        b.group(group)
            .channel(NioDatagramChannel.class)
            .option(ChannelOption.SO_REUSEADDR, true)
            .handler(new ClusterStatusHandler());

        channel = (DatagramChannel)b.bind(bindAddress, port).sync().channel();
      } catch (InterruptedException e) {
        close();
        throw ExceptionUtil.asInterrupt(e);
      }

      NetworkInterface ni;
      if (niName != null) {
        ni = NetworkInterface.getByName(niName);
      } else {
        ni = NetworkInterface.getByInetAddress(Addressing.getIpAddress());
      }

      channel.joinGroup(ina, ni, null, channel.newPromise());
    }

    @Override
    public void close() {
      if (channel != null) {
        channel.close();
        channel = null;
      }
      group.shutdownGracefully();
    }



    /**
     * Class, conforming to the Netty framework, that manages the message received.
     */
    private class ClusterStatusHandler extends SimpleChannelInboundHandler<DatagramPacket> {

      @Override
      public void exceptionCaught(
          ChannelHandlerContext ctx, Throwable cause)
          throws Exception {
        LOG.error("Unexpected exception, continuing.", cause);
      }

      @Override
      public boolean acceptInboundMessage(Object msg)
          throws Exception {
        return super.acceptInboundMessage(msg);
      }


      @Override
      protected void channelRead0(ChannelHandlerContext ctx, DatagramPacket dp) throws Exception {
        ByteBufInputStream bis = new ByteBufInputStream(dp.content());
        try {
          ClusterStatusProtos.ClusterStatus csp = ClusterStatusProtos.ClusterStatus.parseFrom(bis);
          ClusterMetrics ncs = ClusterMetricsBuilder.toClusterMetrics(csp);
          receive(ncs);
        } finally {
          bis.close();
        }
      }
    }
  }
}
