/*
    * 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.shardingsphere.proxy.frontend.netty;
  
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.ChannelInboundHandlerAdapter;
  import lombok.RequiredArgsConstructor;
  import lombok.extern.slf4j.Slf4j;
  import org.apache.shardingsphere.proxy.frontend.connection.ConnectionLimitContext;
  import org.apache.shardingsphere.infra.exception.dialect.exception.connection.TooManyConnectionsException;
  import org.apache.shardingsphere.proxy.frontend.spi.DatabaseProtocolFrontendEngine;
  
  /**
   * Frontend channel limitation inbound handler.
   */
  @RequiredArgsConstructor
  @Slf4j
  public class FrontendChannelLimitationInboundHandler extends ChannelInboundHandlerAdapter {
      
      private final DatabaseProtocolFrontendEngine databaseProtocolFrontendEngine;
      
      @Override
      public void channelActive(final ChannelHandlerContext ctx) {
          if (ConnectionLimitContext.getInstance().connectionAllowed()) {
              ctx.fireChannelActive();
              return;
          }
          log.debug("Closing channel {} due to the number of server connections has reached max connections {}", ctx.channel().remoteAddress(), ConnectionLimitContext.getInstance().getMaxConnections());
          // TODO This is not how actual databases does and should be refactored.
          ctx.writeAndFlush(databaseProtocolFrontendEngine.getCommandExecuteEngine().getErrorPacket(new TooManyConnectionsException()));
          ctx.close();
      }
      
      @Override
      public void channelInactive(final ChannelHandlerContext ctx) {
          ctx.fireChannelInactive();
          ConnectionLimitContext.getInstance().connectionInactive();
      }
  }