package org.eclipse.aether.internal.impl.checksum;
   
   /*
    * 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.
   */
  
  import org.eclipse.aether.spi.connector.checksum.ChecksumAlgorithm;
  import org.eclipse.aether.spi.connector.checksum.ChecksumAlgorithmFactory;
  import org.eclipse.aether.spi.connector.checksum.ChecksumAlgorithmFactorySupport;
  import org.eclipse.aether.util.ChecksumUtils;
  
  import java.nio.ByteBuffer;
  import java.security.MessageDigest;
  import java.security.NoSuchAlgorithmException;
  
  /**
   * Support class to implement {@link ChecksumAlgorithmFactory} based on Java {@link MessageDigest}.
   *
   * @since 1.8.0
   */
  public abstract class MessageDigestChecksumAlgorithmFactorySupport
          extends ChecksumAlgorithmFactorySupport
  {
      public MessageDigestChecksumAlgorithmFactorySupport( String name, String extension )
      {
          super( name, extension );
      }
  
      @Override
      public ChecksumAlgorithm getAlgorithm()
      {
          try
          {
              MessageDigest messageDigest = MessageDigest.getInstance( getName() );
              return new ChecksumAlgorithm()
              {
                  @Override
                  public void update( final ByteBuffer input )
                  {
                      messageDigest.update( input );
                  }
  
                  @Override
                  public String checksum()
                  {
                      return ChecksumUtils.toHexString( messageDigest.digest() );
                  }
              };
          }
          catch ( NoSuchAlgorithmException e )
          {
              throw new IllegalStateException(
                      "MessageDigest algorithm " + getName() + " not supported, but is required by resolver.", e );
          }
      }
  }