/*
    * 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.eclipse.aether.internal.impl.synccontext.named;
  
  import java.io.File;
  import java.net.InetAddress;
  import java.net.UnknownHostException;
  import java.util.Collection;
  
  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 static java.util.Objects.requireNonNull;
  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 = 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;
     }
 }