/*
 * 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.HConstants;
import org.apache.hadoop.hbase.classification.InterfaceAudience;
import org.apache.hadoop.hbase.client.HConnection;
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;

/**
 * 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 Log LOG = LogFactory.getLog(MasterCoprocessorRpcChannel.class);

  private final HConnection connection;

  public MasterCoprocessorRpcChannel(HConnection conn) {
    this.connection = conn;
  }

  @Override
  protected Message callExecService(Descriptors.MethodDescriptor method,
                                  Message request, Message responsePrototype)
      throws IOException {
    if (LOG.isDebugEnabled()) {
      LOG.debug("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();
    CoprocessorServiceResponse result = ProtobufUtil.execService(connection.getMaster(), call);
    Message response = null;
    if (result.getValue().hasValue()) {
      response = responsePrototype.newBuilderForType()
          .mergeFrom(result.getValue().getValue()).build();
    } else {
      response = responsePrototype.getDefaultInstanceForType();
    }
    if (LOG.isTraceEnabled()) {
      LOG.trace("Master Result is value=" + response);
    }
    return response;
  }

}
