/*
    * 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.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.util.StringUtils;
  
  import com.google.protobuf.RpcCallback;
  import com.google.protobuf.RpcController;
  
  /**
   * Used for server-side protobuf RPC service invocations.  This handler allows
   * invocation exceptions to easily be passed through to the RPC server from coprocessor
   * {@link com.google.protobuf.Service} implementations.
   *
   * <p>
   * When implementing {@link com.google.protobuf.Service} defined methods, 
   * coprocessor endpoints can use the following pattern to pass exceptions back to the RPC client:
   * <code>
   * public void myMethod(RpcController controller, MyRequest request,
   *     RpcCallback&lt;MyResponse&gt; done) {
   *   MyResponse response = null;
   *   try {
   *     // do processing
   *     response = MyResponse.getDefaultInstance();  // or use a new builder to populate the response
   *   } catch (IOException ioe) {
   *     // pass exception back up
   *     ResponseConverter.setControllerException(controller, ioe);
   *   }
   *   done.run(response);
   * }
   * </code>
   * </p>
   */
  @InterfaceAudience.Private
  public class ServerRpcController implements RpcController {
    /**
     * The exception thrown within
     * {@link com.google.protobuf.Service#callMethod(
     *   Descriptors.MethodDescriptor, RpcController, Message, RpcCallback)},
     * if any.
     */
    // TODO: it would be good widen this to just Throwable, but IOException is what we allow now
    private IOException serviceException;
    private String errorMessage;
  
    @Override
    public void reset() {
      serviceException = null;
      errorMessage = null;
    }
  
    @Override
    public boolean failed() {
      return (failedOnException() || errorMessage != null);
    }
  
    @Override
    public String errorText() {
      return errorMessage;
    }
  
    @Override
    public void startCancel() {
      // not implemented
    }
  
    @Override
    public void setFailed(String message) {
      errorMessage = message;
    }
  
    @Override
    public boolean isCanceled() {
      return false;
    }
  
    @Override
    public void notifyOnCancel(RpcCallback<Object> objectRpcCallback) {
      // not implemented
    }
 
   /**
    * Sets an exception to be communicated back to the {@link com.google.protobuf.Service} client.
    * @param ioe the exception encountered during execution of the service method
    */
   public void setFailedOn(IOException ioe) {
     serviceException = ioe;
     setFailed(StringUtils.stringifyException(ioe));
   }
 
   /**
    * Returns any exception thrown during service method invocation, or {@code null} if no exception
    * was thrown.  This can be used by clients to receive exceptions generated by RPC calls, even
    * when {@link RpcCallback}s are used and no {@link com.google.protobuf.ServiceException} is
    * declared.
    */
   public IOException getFailedOn() {
     return serviceException;
   }
 
   /**
    * Returns whether or not a server exception was generated in the prior RPC invocation.
    */
   public boolean failedOnException() {
     return serviceException != null;
   }
 
   /**
    * Throws an IOException back out if one is currently stored.
    */
   public void checkFailed() throws IOException {
     if (failedOnException()) {
       throw getFailedOn();
     }
   }
 }