content: /*
   * 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.ambari.server.agent.stomp;
  
  import java.io.UnsupportedEncodingException;
  import java.security.MessageDigest;
  import java.security.NoSuchAlgorithmException;
  import java.util.concurrent.locks.ReentrantLock;
  
  import org.apache.ambari.server.agent.stomp.dto.HashAndTimestampIgnoreMixIn;
  import org.apache.ambari.server.agent.stomp.dto.HashIgnoreMixIn;
  import org.apache.ambari.server.agent.stomp.dto.Hashable;
  import org.apache.ambari.server.events.AgentConfigsUpdateEvent;
  import org.apache.commons.lang.StringUtils;
  
  import com.fasterxml.jackson.core.JsonProcessingException;
  import com.fasterxml.jackson.databind.ObjectMapper;
  
  /**
   * Is used to hash generating for event
   * @param <T> event with hash to control version
   */
  public abstract class AgentDataHolder<T extends Hashable> {
    protected final ReentrantLock updateLock = new ReentrantLock();
    private final static ObjectMapper MAPPER = new ObjectMapper();
    static {
      MAPPER.addMixIn(Hashable.class, HashIgnoreMixIn.class);
      MAPPER.addMixIn(AgentConfigsUpdateEvent.class, HashAndTimestampIgnoreMixIn.class);
    }
  
    protected abstract T getEmptyData();
  
    protected void regenerateDataIdentifiers(T data) {
      data.setHash(getHash(data));
    }
  
    protected boolean isIdentifierValid(T data) {
      return StringUtils.isNotEmpty(data.getHash());
    }
  
    protected String getHash(T data) {
      return getHash(data, "");
    }
  
    protected String getHash(T data, String salt) {
      String json = null;
      try {
        json = MAPPER.writeValueAsString(data);
      } catch (JsonProcessingException e) {
        throw new RuntimeException("Error during mapping message to calculate hash", e);
      }
      String generatedPassword = null;
      try {
        MessageDigest md = MessageDigest.getInstance("SHA-512");
        md.update(salt.getBytes("UTF-8"));
        byte[] bytes = md.digest(json.getBytes("UTF-8"));
        StringBuilder sb = new StringBuilder();
        for (byte b : bytes) {
          sb.append(Integer.toString((b & 0xff) + 0x100, 16).substring(1));
        }
        generatedPassword = sb.toString();
      } catch (NoSuchAlgorithmException | UnsupportedEncodingException e) {
        e.printStackTrace();
      }
      return generatedPassword;
    }
  }
  