/**
 * 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.block;

import java.util.Collection;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.security.token.Token;
import org.apache.hadoop.security.token.TokenIdentifier;
import org.apache.hadoop.security.token.TokenSelector;

/**
 * A block token selector for HDFS
 */
@InterfaceAudience.Private
public class BlockTokenSelector implements TokenSelector<BlockTokenIdentifier> {

  @SuppressWarnings("unchecked")
  public Token<BlockTokenIdentifier> selectToken(Text service,
      Collection<Token<? extends TokenIdentifier>> tokens) {
    if (service == null) {
      return null;
    }
    for (Token<? extends TokenIdentifier> token : tokens) {
      if (BlockTokenIdentifier.KIND_NAME.equals(token.getKind())) {
        return (Token<BlockTokenIdentifier>) token;
      }
    }
    return null;
  }
}
