/*
    * 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 com.google.protobuf.Descriptors;
  import com.google.protobuf.Message;
  import com.google.protobuf.RpcController;
  
  import java.io.IOException;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.hbase.HConstants;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  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;
  
  /**
   * Provides clients with an RPC connection to call coprocessor endpoint {@link com.google.protobuf.Service}s
   * against the active master.  An instance of this class may be obtained
   * by calling {@link org.apache.hadoop.hbase.client.HBaseAdmin#coprocessorService()},
   * 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()
   */
  @InterfaceAudience.Private
  public class MasterCoprocessorRpcChannel extends CoprocessorRpcChannel{
    private static final Log LOG = LogFactory.getLog(MasterCoprocessorRpcChannel.class);
  
    private final ClusterConnection connection;
  
    public MasterCoprocessorRpcChannel(ClusterConnection conn) {
      this.connection = conn;
    }
  
    @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 =
          CoprocessorRpcUtils.buildServiceCall(HConstants.EMPTY_BYTE_ARRAY, method, request);
  
      // TODO: Are we retrying here? Does not seem so. We should use RetryingRpcCaller
      CoprocessorServiceResponse result = ProtobufUtil.execService(controller,
        connection.getMaster(), 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("Master Result is value=" + response);
      }
      return response;
    }
  
  }