/*
    * 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 org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.classification.InterfaceStability;
  import org.apache.hadoop.hbase.protobuf.ResponseConverter;
  
  import com.google.protobuf.BlockingRpcChannel;
  import com.google.protobuf.Descriptors;
  import com.google.protobuf.Message;
  import com.google.protobuf.RpcCallback;
  import com.google.protobuf.RpcChannel;
  import com.google.protobuf.RpcController;
  import com.google.protobuf.ServiceException;
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  
  import java.io.IOException;
  
  /**
   * Base class which provides clients with an RPC connection to
   * call coprocessor endpoint {@link com.google.protobuf.Service}s. 
   * Note that clients should not use this class directly, except through
   * {@link org.apache.hadoop.hbase.client.HTableInterface#coprocessorService(byte[])}.
   */
  @InterfaceAudience.Public
  @InterfaceStability.Evolving
  public abstract class CoprocessorRpcChannel implements RpcChannel, BlockingRpcChannel {
    private static final Log LOG = LogFactory.getLog(CoprocessorRpcChannel.class);
  
    @Override
    @InterfaceAudience.Private
    public void callMethod(Descriptors.MethodDescriptor method,
                           RpcController controller,
                           Message request, Message responsePrototype,
                           RpcCallback<Message> callback) {
      Message response = null;
      try {
        response = callExecService(controller, method, request, responsePrototype);
      } catch (IOException ioe) {
        LOG.warn("Call failed on IOException", ioe);
        ResponseConverter.setControllerException(controller, ioe);
      }
      if (callback != null) {
        callback.run(response);
      }
    }
  
    @Override
    @InterfaceAudience.Private
    public Message callBlockingMethod(Descriptors.MethodDescriptor method,
                                      RpcController controller,
                                      Message request, Message responsePrototype)
        throws ServiceException {
      try {
        return callExecService(controller, method, request, responsePrototype);
      } catch (IOException ioe) {
        throw new ServiceException("Error calling method "+method.getFullName(), ioe);
      }
    }
  
    protected abstract Message callExecService(RpcController controller,
        Descriptors.MethodDescriptor method, Message request, Message responsePrototype)
            throws IOException;
  }