/*
    * 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.maven.buildcache.hash;
  
  import java.security.MessageDigest;
  import java.security.NoSuchAlgorithmException;
  import java.util.Objects;
  
  /**
   * ThreadLocalDigest
   */
  public class ThreadLocalDigest {
  
      public static MessageDigest get(ThreadLocal<MessageDigest> local, String algorithm) {
          final MessageDigest digest = local.get();
          if (digest == null) {
              return create(local, algorithm);
          }
  
          if (Objects.equals(digest.getAlgorithm(), algorithm)) {
              return reset(digest);
          }
  
          reset(digest);
          return create(local, algorithm);
      }
  
      private static MessageDigest create(ThreadLocal<MessageDigest> local, String algorithm) {
          try {
              final MessageDigest digest = MessageDigest.getInstance(algorithm);
              local.set(digest);
              return digest;
          } catch (NoSuchAlgorithmException e) {
              throw new RuntimeException("Cannot create message digest with algorithm: " + algorithm, e);
          }
      }
  
      private static MessageDigest reset(MessageDigest digest) {
          digest.reset();
          return digest;
      }
  
      private ThreadLocalDigest() {}
  }