package org.eclipse.aether.internal.impl.synccontext.named;
   
   /*
    * 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.RepositorySystemSession;
  import org.eclipse.aether.artifact.Artifact;
  import org.eclipse.aether.metadata.Metadata;
  import org.eclipse.aether.util.ConfigUtils;
  import org.eclipse.aether.util.StringDigestUtil;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.io.File;
  import java.net.InetAddress;
  import java.net.UnknownHostException;
  import java.util.Collection;
  import java.util.Objects;
  
  import static java.util.stream.Collectors.toList;
  
  /**
   * Wrapping {@link NameMapper}, that wraps another {@link NameMapper} and adds a "discriminator" as prefix, that
   * makes lock names unique including the hostname and local repository (by default). The discriminator may be passed
   * in via {@link RepositorySystemSession} or is automatically calculated based on the local hostname and repository
   * path. The implementation retains order of collection elements as it got it from
   * {@link NameMapper#nameLocks(RepositorySystemSession, Collection, Collection)} method.
   * <p>
   * The default setup wraps {@link GAVNameMapper}, but manually may be created any instance needed.
   */
  public class DiscriminatingNameMapper implements NameMapper
  {
      /**
       * Configuration property to pass in discriminator
       */
      private static final String CONFIG_PROP_DISCRIMINATOR = "aether.syncContext.named.discriminating.discriminator";
  
      /**
       * Configuration property to pass in hostname
       */
      private static final String CONFIG_PROP_HOSTNAME = "aether.syncContext.named.discriminating.hostname";
  
      private static final String DEFAULT_DISCRIMINATOR_DIGEST = "da39a3ee5e6b4b0d3255bfef95601890afd80709";
  
      private static final String DEFAULT_HOSTNAME = "localhost";
  
      private static final Logger LOGGER = LoggerFactory.getLogger( DiscriminatingNameMapper.class );
  
      private final NameMapper delegate;
  
      private final String hostname;
  
      public DiscriminatingNameMapper( final NameMapper delegate )
      {
          this.delegate = Objects.requireNonNull( delegate );
          this.hostname = getHostname();
      }
  
      @Override
      public boolean isFileSystemFriendly()
      {
          return false; // uses ":" in produced lock names
      }
  
      @Override
      public Collection<String> nameLocks( final RepositorySystemSession session,
                                           final Collection<? extends Artifact> artifacts,
                                           final Collection<? extends Metadata> metadatas )
      {
          String discriminator = createDiscriminator( session );
          return delegate.nameLocks( session, artifacts, metadatas ).stream()
                  .map( s -> discriminator + ":" + s )
                  .collect( toList() );
      }
  
      private String getHostname()
      {
          try
          {
              return InetAddress.getLocalHost().getHostName();
          }
          catch ( UnknownHostException e )
          {
             LOGGER.warn( "Failed to get hostname, using '{}'", DEFAULT_HOSTNAME, e );
             return DEFAULT_HOSTNAME;
         }
     }
 
     private String createDiscriminator( final RepositorySystemSession session )
     {
         String discriminator = ConfigUtils.getString( session, null, CONFIG_PROP_DISCRIMINATOR );
 
         if ( discriminator == null || discriminator.isEmpty() )
         {
             String hostname = ConfigUtils.getString( session, this.hostname, CONFIG_PROP_HOSTNAME );
             File basedir = session.getLocalRepository().getBasedir();
             discriminator = hostname + ":" + basedir;
             try
             {
                 return StringDigestUtil.sha1( discriminator );
             }
             catch ( Exception e )
             {
                 LOGGER.warn( "Failed to calculate discriminator digest, using '{}'", DEFAULT_DISCRIMINATOR_DIGEST, e );
                 return DEFAULT_DISCRIMINATOR_DIGEST;
             }
         }
         return discriminator;
     }
 }