/*
    * 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.omid.tso;
  
  import org.apache.phoenix.thirdparty.com.google.common.annotations.VisibleForTesting;
  import org.apache.phoenix.thirdparty.com.google.common.util.concurrent.ThreadFactoryBuilder;
  import org.apache.omid.metrics.MetricsRegistry;
  import org.apache.omid.proto.TSOProto;
  import org.jboss.netty.bootstrap.ServerBootstrap;
  import org.jboss.netty.channel.Channel;
  import org.jboss.netty.channel.ChannelFactory;
  import org.jboss.netty.channel.ChannelHandler;
  import org.jboss.netty.channel.ChannelHandlerContext;
  import org.jboss.netty.channel.ChannelPipeline;
  import org.jboss.netty.channel.ChannelPipelineFactory;
  import org.jboss.netty.channel.ChannelStateEvent;
  import org.jboss.netty.channel.Channels;
  import org.jboss.netty.channel.ExceptionEvent;
  import org.jboss.netty.channel.MessageEvent;
  import org.jboss.netty.channel.SimpleChannelHandler;
  import org.jboss.netty.channel.group.ChannelGroup;
  import org.jboss.netty.channel.group.DefaultChannelGroup;
  import org.jboss.netty.channel.socket.nio.NioServerSocketChannelFactory;
  import org.jboss.netty.handler.codec.frame.LengthFieldBasedFrameDecoder;
  import org.jboss.netty.handler.codec.frame.LengthFieldPrepender;
  import org.jboss.netty.handler.codec.protobuf.ProtobufDecoder;
  import org.jboss.netty.handler.codec.protobuf.ProtobufEncoder;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import javax.inject.Inject;
  import java.io.Closeable;
  import java.io.IOException;
  import java.net.InetSocketAddress;
  import java.nio.channels.ClosedChannelException;
  import java.util.concurrent.Executors;
  
  /**
   * ChannelHandler for the TSO Server.
   *
   * Incoming requests are processed in this class
   */
  public class TSOChannelHandler extends SimpleChannelHandler implements Closeable {
  
      private static final Logger LOG = LoggerFactory.getLogger(TSOChannelHandler.class);
  
      private final ChannelFactory factory;
  
      private final ServerBootstrap bootstrap;
  
      @VisibleForTesting
      Channel listeningChannel;
      @VisibleForTesting
      ChannelGroup channelGroup;
  
      private RequestProcessor requestProcessor;
  
      private TSOServerConfig config;
  
      private MetricsRegistry metrics;
  
      @Inject
      public TSOChannelHandler(TSOServerConfig config, RequestProcessor requestProcessor, MetricsRegistry metrics) {
  
          this.config = config;
          this.metrics = metrics;
          this.requestProcessor = requestProcessor;
          // Setup netty listener
          this.factory = new NioServerSocketChannelFactory(
                  Executors.newCachedThreadPool(new ThreadFactoryBuilder().setNameFormat("boss-%d").build()),
                  Executors.newCachedThreadPool(new ThreadFactoryBuilder().setNameFormat("worker-%d").build()),
                  (Runtime.getRuntime().availableProcessors() * 2 + 1) * 2);
  
          this.bootstrap = new ServerBootstrap(factory);
          bootstrap.setPipelineFactory(new TSOPipelineFactory(this));
  
      }
  
      /**
       * Allows to create and connect the communication channel closing the previous one if existed
       */
      void reconnect() {
          if (listeningChannel == null && channelGroup == null) {
              LOG.debug("Creating communication channel...");
         } else {
             LOG.debug("Reconnecting communication channel...");
             closeConnection();
         }
         // Create the global ChannelGroup
         channelGroup = new DefaultChannelGroup(TSOChannelHandler.class.getName());
         LOG.debug("\tCreating channel to listening for incoming connections in port {}", config.getPort());
         listeningChannel = bootstrap.bind(new InetSocketAddress(config.getPort()));
         channelGroup.add(listeningChannel);
         LOG.debug("\tListening channel created and connected: {}", listeningChannel);
     }
 
     /**
      * Allows to close the communication channel
      */
     void closeConnection() {
         LOG.debug("Closing communication channel...");
         if (listeningChannel != null) {
             LOG.debug("\tUnbinding listening channel {}", listeningChannel);
             listeningChannel.unbind().awaitUninterruptibly();
             LOG.debug("\tListening channel {} unbound", listeningChannel);
         }
         if (channelGroup != null) {
             LOG.debug("\tClosing channel group {}", channelGroup);
             channelGroup.close().awaitUninterruptibly();
             LOG.debug("\tChannel group {} closed", channelGroup);
         }
     }
 
     // ----------------------------------------------------------------------------------------------------------------
     // Netty SimpleChannelHandler implementation
     // ----------------------------------------------------------------------------------------------------------------
 
     @Override
     public void channelConnected(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
         channelGroup.add(ctx.getChannel());
         LOG.debug("TSO channel connected: {}", ctx.getChannel());
     }
 
     @Override
     public void channelDisconnected(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
         channelGroup.remove(ctx.getChannel());
         LOG.debug("TSO channel disconnected: {}", ctx.getChannel());
     }
 
     @Override
     public void channelClosed(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
         LOG.debug("TSO channel closed: {}", ctx.getChannel());
     }
 
     /**
      * Handle received messages
      */
     @Override
     public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) {
         Object msg = e.getMessage();
         if (msg instanceof TSOProto.Request) {
             TSOProto.Request request = (TSOProto.Request) msg;
             if (request.hasHandshakeRequest()) {
                 checkHandshake(ctx, request.getHandshakeRequest());
                 return;
             }
             if (!handshakeCompleted(ctx)) {
                 LOG.error("Handshake not completed. Closing channel {}", ctx.getChannel());
                 ctx.getChannel().close();
             }
 
             if (request.hasTimestampRequest()) {
                 requestProcessor.timestampRequest(ctx.getChannel(), MonitoringContextFactory.getInstance(config,metrics));
             } else if (request.hasCommitRequest()) {
                 TSOProto.CommitRequest cr = request.getCommitRequest();
                 requestProcessor.commitRequest(cr.getStartTimestamp(),
                                                cr.getCellIdList(),
                                                cr.getTableIdList(),
                                                cr.getIsRetry(),
                                                ctx.getChannel(),
                                                MonitoringContextFactory.getInstance(config,metrics));
             } else if (request.hasFenceRequest()) {
                 TSOProto.FenceRequest fr = request.getFenceRequest();
                 requestProcessor.fenceRequest(fr.getTableId(),
                         ctx.getChannel(),
                         MonitoringContextFactory.getInstance(config,metrics));
             } else {
                 LOG.error("Invalid request {}. Closing channel {}", request, ctx.getChannel());
                 ctx.getChannel().close();
             }
         } else {
             LOG.error("Unknown message type", msg);
         }
     }
 
     @SuppressWarnings("ThrowableResultOfMethodCallIgnored")
     @Override
     public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e) {
         if (e.getCause() instanceof ClosedChannelException) {
             LOG.warn("ClosedChannelException caught. Cause: ", e.getCause());
             return;
         }
         LOG.warn("Unexpected exception from downstream. Closing channel {} {}", ctx.getChannel(), e.getCause());
         ctx.getChannel().close();
     }
 
     // ----------------------------------------------------------------------------------------------------------------
     // Closeable implementation
     // ----------------------------------------------------------------------------------------------------------------
     @Override
     public void close() throws IOException {
         closeConnection();
         factory.releaseExternalResources();
     }
 
     // ----------------------------------------------------------------------------------------------------------------
     // Helper methods and classes
     // ----------------------------------------------------------------------------------------------------------------
 
     /**
      * Contains the required context for handshake
      */
     private static class TSOChannelContext {
 
         boolean handshakeComplete;
 
         TSOChannelContext() {
             handshakeComplete = false;
         }
 
         boolean getHandshakeComplete() {
             return handshakeComplete;
         }
 
         void setHandshakeComplete() {
             handshakeComplete = true;
         }
 
     }
 
     private void checkHandshake(final ChannelHandlerContext ctx, TSOProto.HandshakeRequest request) {
 
         TSOProto.HandshakeResponse.Builder response = TSOProto.HandshakeResponse.newBuilder();
         if (request.hasClientCapabilities()) {
 
             response.setClientCompatible(true)
                     .setServerCapabilities(TSOProto.Capabilities.newBuilder().build());
             TSOChannelContext tsoCtx = new TSOChannelContext();
             tsoCtx.setHandshakeComplete();
             ctx.setAttachment(tsoCtx);
         } else {
             response.setClientCompatible(false);
         }
         response.setLowLatency(config.getLowLatency());
         ctx.getChannel().write(TSOProto.Response.newBuilder().setHandshakeResponse(response.build()).build());
 
     }
 
     private boolean handshakeCompleted(ChannelHandlerContext ctx) {
 
         Object o = ctx.getAttachment();
         if (o instanceof TSOChannelContext) {
             TSOChannelContext tsoCtx = (TSOChannelContext) o;
             return tsoCtx.getHandshakeComplete();
         }
         return false;
 
     }
 
     /**
      * Netty pipeline configuration
      */
     static class TSOPipelineFactory implements ChannelPipelineFactory {
 
         private final ChannelHandler handler;
 
         TSOPipelineFactory(ChannelHandler handler) {
             this.handler = handler;
         }
 
         public ChannelPipeline getPipeline() throws Exception {
 
             ChannelPipeline pipeline = Channels.pipeline();
             // Max packet length is 10MB. Transactions with so many cells
             // that the packet is rejected will receive a ServiceUnavailableException.
             // 10MB is enough for 2 million cells in a transaction though.
             pipeline.addLast("lengthbaseddecoder", new LengthFieldBasedFrameDecoder(10 * 1024 * 1024, 0, 4, 0, 4));
             pipeline.addLast("lengthprepender", new LengthFieldPrepender(4));
             pipeline.addLast("protobufdecoder", new ProtobufDecoder(TSOProto.Request.getDefaultInstance()));
             pipeline.addLast("protobufencoder", new ProtobufEncoder());
             pipeline.addLast("handler", handler);
 
             return pipeline;
         }
     }
 
 }