package org.apache.maven.extension.internal;
   
   /*
    * 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 java.io.File;
  import java.io.IOException;
  import java.io.InputStream;
  import java.net.URL;
  import java.util.Collection;
  import java.util.Enumeration;
  import java.util.LinkedHashSet;
  import java.util.Set;
  
  import org.apache.maven.project.ExtensionDescriptor;
  import org.apache.maven.project.ExtensionDescriptorBuilder;
  import org.codehaus.plexus.classworlds.realm.ClassRealm;
  import org.codehaus.plexus.util.IOUtil;
  
  import com.google.common.collect.ImmutableSet;
  
  /**
   * Provides information about artifacts (identified by groupId:artifactId string key) and classpath elements exported by
   * Maven core itself or a Maven core extension.
   * 
   * @since 3.3.0
   */
  public class CoreExtensionEntry
  {
      private final ClassRealm realm;
  
      private final Set<String> artifacts;
  
      private final Set<String> packages;
  
      public CoreExtensionEntry( ClassRealm realm, Collection<String> artifacts, Collection<String> packages )
      {
          this.realm = realm;
          this.artifacts = ImmutableSet.copyOf( artifacts );
          this.packages = ImmutableSet.copyOf( packages );
      }
  
      /**
       * Returns ClassLoader used to load extension classes.
       */
      public ClassRealm getClassRealm()
      {
          return realm;
      }
  
      /**
       * Returns artifacts exported by the extension, identified by groupId:artifactId string key.
       */
      public Set<String> getExportedArtifacts()
      {
          return artifacts;
      }
  
      /**
       * Returns classpath elements exported by the extension.
       */
      public Set<String> getExportedPackages()
      {
          return packages;
      }
  
      private static final ExtensionDescriptorBuilder builder = new ExtensionDescriptorBuilder();
  
      public static CoreExtensionEntry discoverFrom( ClassRealm loader )
      {
          Set<String> artifacts = new LinkedHashSet<String>();
          Set<String> packages = new LinkedHashSet<String>();
  
          try
          {
              Enumeration<URL> urls = loader.getResources( builder.getExtensionDescriptorLocation() );
              while ( urls.hasMoreElements() )
              {
                  InputStream is = urls.nextElement().openStream();
                  try
                  {
                      ExtensionDescriptor descriptor = builder.build( is );
                      artifacts.addAll( descriptor.getExportedArtifacts() );
                     packages.addAll( descriptor.getExportedPackages() );
                 }
                 finally
                 {
                     IOUtil.close( is );
                 }
             }
         }
         catch ( IOException ignored )
         {
             // exports descriptors are entirely optional
         }
 
         return new CoreExtensionEntry( loader, artifacts, packages );
     }
 
     public static CoreExtensionEntry discoverFrom( ClassRealm loader, Collection<File> classpath )
     {
         Set<String> artifacts = new LinkedHashSet<String>();
         Set<String> packages = new LinkedHashSet<String>();
 
         try
         {
             for ( File entry : classpath )
             {
                 ExtensionDescriptor descriptor = builder.build( entry );
                 if ( descriptor != null )
                 {
                     artifacts.addAll( descriptor.getExportedArtifacts() );
                     packages.addAll( descriptor.getExportedPackages() );
                 }
             }
         }
         catch ( IOException ignored )
         {
             // exports descriptors are entirely optional
         }
 
         return new CoreExtensionEntry( loader, artifacts, packages );
     }
 
 }