/*
    * 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.maven.extension.internal;
  
  import java.io.File;
  import java.io.IOException;
  import java.io.InputStream;
  import java.net.URL;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.Enumeration;
  import java.util.HashSet;
  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;
  
  /**
   * 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 = Collections.unmodifiableSet(new HashSet<>(artifacts));
          this.packages = Collections.unmodifiableSet(new HashSet<>(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<>();
          Set<String> packages = new LinkedHashSet<>();
  
          try {
              Enumeration<URL> urls = loader.getResources(BUILDER.getExtensionDescriptorLocation());
              while (urls.hasMoreElements()) {
  
                  try (InputStream is = urls.nextElement().openStream()) {
                      ExtensionDescriptor descriptor = BUILDER.build(is);
                      artifacts.addAll(descriptor.getExportedArtifacts());
                      packages.addAll(descriptor.getExportedPackages());
                  }
              }
          } 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<>();
         Set<String> packages = new LinkedHashSet<>();
 
         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);
     }
 }