/**
 * 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.accumulo.core.rpc;

import java.io.IOException;
import java.security.PrivilegedExceptionAction;
import java.util.concurrent.atomic.AtomicReference;

import org.apache.hadoop.security.UserGroupInformation;
import org.apache.thrift.transport.TTransport;
import org.apache.thrift.transport.TTransportException;

/**
 * The Thrift SASL transports call Sasl.createSaslServer and Sasl.createSaslClient inside open(). So, we need to assume the correct UGI when the transport is
 * opened so that the SASL mechanisms have access to the right principal. This transport wraps the Sasl transports to set up the right UGI context for open().
 *
 * This is used on the client side, where the API explicitly opens a transport to the server.
 *
 * Lifted from Apache Hive 0.14
 */
public class UGIAssumingTransport extends FilterTransport {
  protected UserGroupInformation ugi;

  public UGIAssumingTransport(TTransport wrapped, UserGroupInformation ugi) {
    super(wrapped);
    this.ugi = ugi;
  }

  @Override
  public void open() throws TTransportException {
    final AtomicReference<TTransportException> holder = new AtomicReference<>(null);
    try {
      ugi.doAs(new PrivilegedExceptionAction<Void>() {
        @Override
        public Void run() {
          try {
            getWrapped().open();
          } catch (TTransportException tte) {
            holder.set(tte);
          }
          return null;
        }
      });
    } catch (IOException | InterruptedException e) {
      throw new RuntimeException(e);
    }

    // Make sure the transport exception gets (re)thrown if it happened
    TTransportException tte = holder.get();
    if (null != tte) {
      throw tte;
    }
  }
}