/**
    * 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.util.List;
  
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.CellScannable;
  import org.apache.hadoop.hbase.CellScanner;
  import org.apache.hadoop.hbase.CellUtil;
  import org.apache.hadoop.hbase.HConstants;
  import org.apache.hadoop.hbase.TableName;
  
  import com.google.protobuf.RpcCallback;
  import com.google.protobuf.RpcController;
  
  /**
   * Optionally carries Cells across the proxy/service interface down into ipc. On its
   * way out it optionally carries a set of result Cell data.  We stick the Cells here when we want
   * to avoid having to protobuf them.  This class is used ferrying data across the proxy/protobuf
   * service chasm.  Used by client and server ipc'ing.
   */
  @InterfaceAudience.Private
  public class PayloadCarryingRpcController implements RpcController, CellScannable {
    /**
     * Priority to set on this request.  Set it here in controller so available composing the
     * request.  This is the ordained way of setting priorities going forward.  We will be
     * undoing the old annotation-based mechanism.
     */
    // Currently only multi call makes use of this.  Eventually this should be only way to set
    // priority.
    private int priority = 0;
  
    // TODO: Fill out the rest of this class methods rather than return UnsupportedOperationException
  
    /**
     * They are optionally set on construction, cleared after we make the call, and then optionally
     * set on response with the result. We use this lowest common denominator access to Cells because
     * sometimes the scanner is backed by a List of Cells and other times, it is backed by an
     * encoded block that implements CellScanner.
     */
    private CellScanner cellScanner;
  
    public PayloadCarryingRpcController() {
      this((CellScanner)null);
    }
  
    public PayloadCarryingRpcController(final CellScanner cellScanner) {
      this.cellScanner = cellScanner;
    }
  
    public PayloadCarryingRpcController(final List<CellScannable> cellIterables) {
      this.cellScanner = cellIterables == null? null: CellUtil.createCellScanner(cellIterables);
    }
  
    /**
     * @return One-shot cell scanner (you cannot back it up and restart)
     */
    public CellScanner cellScanner() {
      return cellScanner;
    }
  
    public void setCellScanner(final CellScanner cellScanner) {
      this.cellScanner = cellScanner;
    }
  
    @Override
    public String errorText() {
      throw new UnsupportedOperationException();
    }
  
    @Override
    public boolean failed() {
      throw new UnsupportedOperationException();
    }
  
    @Override
    public boolean isCanceled() {
      throw new UnsupportedOperationException();
    }
  
    @Override
    public void notifyOnCancel(RpcCallback<Object> arg0) {
      throw new UnsupportedOperationException();
   }
 
   @Override
   public void reset() {
     throw new UnsupportedOperationException();
   }
 
   @Override
   public void setFailed(String arg0) {
     throw new UnsupportedOperationException();
   }
 
   @Override
   public void startCancel() {
     throw new UnsupportedOperationException();
   }
 
   /**
    * @param priority Priority for this request; should fall roughly in the range
    * {@link HConstants#NORMAL_QOS} to {@link HConstants#HIGH_QOS}
    */
   public void setPriority(int priority) {
     this.priority = priority;
   }
 
   /**
    * @param tn Set priority based off the table we are going against.
    */
   public void setPriority(final TableName tn) {
     this.priority = tn != null && tn.isSystemTable()? HConstants.HIGH_QOS: HConstants.NORMAL_QOS;
   }
 
   /**
    * @return The priority of this request
    */
   public int getPriority() {
     return priority;
   }
 }