/**
 * 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.hdfs.security.token.delegation;

import java.net.URI;
import java.util.Collection;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hdfs.client.HdfsClientConfigKeys;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.net.NetUtils;
import org.apache.hadoop.security.SecurityUtil;
import org.apache.hadoop.security.token.Token;
import org.apache.hadoop.security.token.delegation.AbstractDelegationTokenSelector;

/**
 * A delegation token that is specialized for HDFS
 */
@InterfaceAudience.Private
public class DelegationTokenSelector
    extends AbstractDelegationTokenSelector<DelegationTokenIdentifier>{
  public static final String SERVICE_NAME_KEY = "hdfs.service.host_";

  /**
   * Select the delegation token for hdfs.  The port will be rewritten to
   * the port of hdfs.service.host_$nnAddr, or the default rpc namenode port. 
   * This method should only be called by non-hdfs filesystems that do not
   * use the rpc port to acquire tokens.  Ex. webhdfs, hftp 
   * @param nnUri of the remote namenode
   * @param tokens as a collection
   * @param conf hadoop configuration
   * @return Token
   */
  public Token<DelegationTokenIdentifier> selectToken(
      final URI nnUri, Collection<Token<?>> tokens,
      final Configuration conf) {
    // this guesses the remote cluster's rpc service port.
    // the current token design assumes it's the same as the local cluster's
    // rpc port unless a config key is set.  there should be a way to automatic
    // and correctly determine the value
    Text serviceName = SecurityUtil.buildTokenService(nnUri);
    final String nnServiceName = conf.get(SERVICE_NAME_KEY + serviceName);
    
    int nnRpcPort = HdfsClientConfigKeys.DFS_NAMENODE_RPC_PORT_DEFAULT;
    if (nnServiceName != null) {
      nnRpcPort = NetUtils.createSocketAddr(nnServiceName, nnRpcPort).getPort(); 
    }
    // use original hostname from the uri to avoid unintentional host resolving
    serviceName = SecurityUtil.buildTokenService(
    		NetUtils.createSocketAddrForHost(nnUri.getHost(), nnRpcPort));
    
    return selectToken(serviceName, tokens);
  }

  public DelegationTokenSelector() {
    super(DelegationTokenIdentifier.HDFS_DELEGATION_KIND);
  }
}
