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.causeway.commons.internal.hash;
  
  import java.io.ByteArrayInputStream;
  import java.io.InputStream;
  import java.security.DigestInputStream;
  import java.security.MessageDigest;
  import java.security.NoSuchAlgorithmException;
  import java.util.Optional;
  
  import org.jspecify.annotations.Nullable;
  
  import org.apache.causeway.commons.internal.base._NullSafe;
  
  import org.jspecify.annotations.NonNull;
  import lombok.RequiredArgsConstructor;
  import lombok.SneakyThrows;
  
  /**
   * <h1>- internal use only -</h1>
   * <p>
   * <b>WARNING</b>: Do <b>NOT</b> use any of the classes provided by this package! <br/>
   * These may be changed or removed without notice!
   * </p>
   *
   * @since 2.0
   */
  public final class _Hashes {
  
      @RequiredArgsConstructor
      public static enum Algorithm {
          MD5("MD5"),
          SHA1("SHA"),
          SHA224("SHA-224"),
          SHA256("SHA-256"),
          SHA384("SHA-384"),
          SHA512("SHA-512"),
          ;
          private final String algorithmName;
  
          public Optional<MessageDigest> getMessageDigest() {
              try {
                  return Optional.ofNullable(MessageDigest.getInstance(algorithmName));
              } catch (NoSuchAlgorithmException e) {
                  return Optional.empty();
              }
          }
  
      }
  
      public static Optional<byte[]> digest(@NonNull Algorithm algorithm, @Nullable byte[] bytes) {
          final int size = _NullSafe.size(bytes);
          if(size==0) {
              return Optional.empty();
          }
          return algorithm.getMessageDigest()
          .map(md->digest(md, new ByteArrayInputStream(bytes), Math.max(size, 4096)));
      }
  
      // -- HELPER
  
      @SneakyThrows
      private static byte[] digest(@NonNull MessageDigest md, @NonNull InputStream inputStream, int buffersize) {
          md.reset();
          try(DigestInputStream dis = new DigestInputStream(inputStream, md)){
              byte[] buffer = new byte[buffersize];
              while(dis.read(buffer)>0);
          }
          return md.digest();
      }
  
  }
  