/*
    * 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.ipc;
  
  import java.io.IOException;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.HConstants;
  import org.apache.hadoop.hbase.ServerName;
  import org.apache.hadoop.hbase.client.ClusterConnection;
  import org.apache.hadoop.hbase.protobuf.ProtobufUtil;
  import org.apache.hadoop.hbase.protobuf.generated.ClientProtos;
  import org.apache.hadoop.hbase.protobuf.generated.ClientProtos.CoprocessorServiceResponse;
  import org.apache.hadoop.hbase.util.ByteStringer;
  
  
  import com.google.protobuf.Descriptors;
  import com.google.protobuf.Message;
  import com.google.protobuf.RpcController;
  
  /**
   * Provides clients with an RPC connection to call coprocessor endpoint
   * {@link com.google.protobuf.Service}s against a given region server. An instance of this class may
   * be obtained by calling {@link org.apache.hadoop.hbase.client.HBaseAdmin#coprocessorService(ServerName)},
   * but should normally only be used in creating a new {@link com.google.protobuf.Service} stub to
   * call the endpoint methods.
   * @see org.apache.hadoop.hbase.client.HBaseAdmin#coprocessorService(ServerName)
   */
  @InterfaceAudience.Private
  public class RegionServerCoprocessorRpcChannel extends CoprocessorRpcChannel {
    private static final Log LOG = LogFactory.getLog(RegionServerCoprocessorRpcChannel.class);
    private final ClusterConnection connection;
    private final ServerName serverName;
  
    public RegionServerCoprocessorRpcChannel(ClusterConnection conn, ServerName serverName) {
      this.connection = conn;
      this.serverName = serverName;
    }
  
    @Override
    protected Message callExecService(RpcController controller,
        Descriptors.MethodDescriptor method, Message request, Message responsePrototype)
            throws IOException {
      if (LOG.isTraceEnabled()) {
        LOG.trace("Call: " + method.getName() + ", " + request.toString());
      }
      final ClientProtos.CoprocessorServiceCall call =
          ClientProtos.CoprocessorServiceCall.newBuilder()
              .setRow(ByteStringer.wrap(HConstants.EMPTY_BYTE_ARRAY))
              .setServiceName(method.getService().getFullName()).setMethodName(method.getName())
              .setRequest(request.toByteString()).build();
  
      // TODO: Are we retrying here? Does not seem so. We should use RetryingRpcCaller
      CoprocessorServiceResponse result =
          ProtobufUtil.execRegionServerService(controller, connection.getClient(serverName), call);
      Message response = null;
      if (result.getValue().hasValue()) {
        Message.Builder builder = responsePrototype.newBuilderForType();
        ProtobufUtil.mergeFrom(builder, result.getValue().getValue());
        response = builder.build();
      } else {
        response = responsePrototype.getDefaultInstanceForType();
      }
      if (LOG.isTraceEnabled()) {
        LOG.trace("Result is value=" + response);
      }
      return response;
    }
  }