/*
    * 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.classrealm;
  
  import javax.inject.Inject;
  import javax.inject.Named;
  import javax.inject.Singleton;
  
  import java.io.File;
  import java.net.MalformedURLException;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.LinkedHashSet;
  import java.util.List;
  import java.util.Map;
  import java.util.Objects;
  import java.util.Random;
  import java.util.Set;
  import java.util.TreeMap;
  
  import org.apache.maven.artifact.ArtifactUtils;
  import org.apache.maven.classrealm.ClassRealmRequest.RealmType;
  import org.apache.maven.extension.internal.CoreExports;
  import org.apache.maven.model.Model;
  import org.apache.maven.model.Plugin;
  import org.codehaus.plexus.MutablePlexusContainer;
  import org.codehaus.plexus.PlexusContainer;
  import org.codehaus.plexus.classworlds.ClassWorld;
  import org.codehaus.plexus.classworlds.realm.ClassRealm;
  import org.codehaus.plexus.classworlds.realm.DuplicateRealmException;
  import org.eclipse.aether.artifact.Artifact;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Manages the class realms used by Maven. <strong>Warning:</strong> This is an internal utility class that is only
   * public for technical reasons, it is not part of the public API. In particular, this class can be changed or deleted
   * without prior notice.
   *
   * @author Benjamin Bentmann
   */
  @Named
  @Singleton
  public class DefaultClassRealmManager implements ClassRealmManager {
      public static final String API_REALMID = "maven.api";
  
      /**
       * During normal command line build, ClassWorld is loaded by jvm system classloader, which only includes
       * plexus-classworlds jar and possibly javaagent classes, see https://issues.apache.org/jira/browse/MNG-4747.
       * <p>
       * Using ClassWorld to determine plugin/extensions realm parent classloaders gives m2e and integration test harness
       * flexibility to load multiple version of maven into dedicated classloaders without assuming state of jvm system
       * classloader.
       */
      private static final ClassLoader PARENT_CLASSLOADER = ClassWorld.class.getClassLoader();
  
      private final Logger logger = LoggerFactory.getLogger(getClass());
  
      private final ClassWorld world;
  
      private final ClassRealm containerRealm;
  
      // this is a live injected collection
      private final List<ClassRealmManagerDelegate> delegates;
  
      private final ClassRealm mavenApiRealm;
  
      /**
       * Patterns of artifacts provided by maven core and exported via maven api realm. These artifacts are filtered from
       * plugin and build extensions realms to avoid presence of duplicate and possibly conflicting classes on classpath.
       */
      private final Set<String> providedArtifacts;
  
      @Inject
      public DefaultClassRealmManager(
              PlexusContainer container, List<ClassRealmManagerDelegate> delegates, CoreExports exports) {
          this.world = ((MutablePlexusContainer) container).getClassWorld();
          this.containerRealm = container.getContainerRealm();
          this.delegates = delegates;
  
          Map<String, ClassLoader> foreignImports = exports.getExportedPackages();
  
          this.mavenApiRealm = createRealm(
                 API_REALMID,
                 RealmType.Core,
                 null /* parent */,
                 null /* parentImports */,
                 foreignImports,
                 null /* artifacts */);
 
         this.providedArtifacts = exports.getExportedArtifacts();
     }
 
     private ClassRealm newRealm(String id) {
         synchronized (world) {
             String realmId = id;
 
             Random random = new Random();
 
             while (true) {
                 try {
                     ClassRealm classRealm = world.newRealm(realmId, null);
 
                     if (logger.isDebugEnabled()) {
                         logger.debug("Created new class realm " + realmId);
                     }
 
                     return classRealm;
                 } catch (DuplicateRealmException e) {
                     realmId = id + '-' + random.nextInt();
                 }
             }
         }
     }
 
     public ClassRealm getMavenApiRealm() {
         return mavenApiRealm;
     }
 
     /**
      * Creates a new class realm with the specified parent and imports.
      *
      * @param baseRealmId The base id to use for the new realm, must not be {@code null}.
      * @param type The type of the class realm, must not be {@code null}.
      * @param parent The parent realm for the new realm, may be {@code null}.
      * @param parentImports The packages/types to import from the parent realm, may be {@code null}.
      * @param foreignImports The packages/types to import from foreign realms, may be {@code null}.
      * @param artifacts The artifacts to add to the realm, may be {@code null}. Unresolved artifacts (i.e. with a
      *            missing file) will automatically be excluded from the realm.
      * @return The created class realm, never {@code null}.
      */
     private ClassRealm createRealm(
             String baseRealmId,
             RealmType type,
             ClassLoader parent,
             List<String> parentImports,
             Map<String, ClassLoader> foreignImports,
             List<Artifact> artifacts) {
         Set<String> artifactIds = new LinkedHashSet<>();
 
         List<ClassRealmConstituent> constituents = new ArrayList<>();
 
         if (artifacts != null) {
             for (Artifact artifact : artifacts) {
                 if (!isProvidedArtifact(artifact)) {
                     artifactIds.add(getId(artifact));
                     if (artifact.getFile() != null) {
                         constituents.add(new ArtifactClassRealmConstituent(artifact));
                     }
                 }
             }
         }
 
         if (parentImports != null) {
             parentImports = new ArrayList<>(parentImports);
         } else {
             parentImports = new ArrayList<>();
         }
 
         if (foreignImports != null) {
             foreignImports = new TreeMap<>(foreignImports);
         } else {
             foreignImports = new TreeMap<>();
         }
 
         ClassRealm classRealm = newRealm(baseRealmId);
 
         if (parent != null) {
             classRealm.setParentClassLoader(parent);
         }
 
         callDelegates(classRealm, type, parent, parentImports, foreignImports, constituents);
 
         wireRealm(classRealm, parentImports, foreignImports);
 
         Set<String> includedIds = populateRealm(classRealm, constituents);
 
         if (logger.isDebugEnabled()) {
             artifactIds.removeAll(includedIds);
 
             for (String id : artifactIds) {
                 logger.debug("  Excluded: " + id);
             }
         }
 
         return classRealm;
     }
 
     public ClassRealm getCoreRealm() {
         return containerRealm;
     }
 
     public ClassRealm createProjectRealm(Model model, List<Artifact> artifacts) {
         Objects.requireNonNull(model, "model cannot be null");
 
         ClassLoader parent = getMavenApiRealm();
 
         return createRealm(getKey(model), RealmType.Project, parent, null, null, artifacts);
     }
 
     private static String getKey(Model model) {
         return "project>" + model.getGroupId() + ":" + model.getArtifactId() + ":" + model.getVersion();
     }
 
     public ClassRealm createExtensionRealm(Plugin plugin, List<Artifact> artifacts) {
         Objects.requireNonNull(plugin, "plugin cannot be null");
 
         Map<String, ClassLoader> foreignImports = Collections.singletonMap("", getMavenApiRealm());
 
         return createRealm(
                 getKey(plugin, true), RealmType.Extension, PARENT_CLASSLOADER, null, foreignImports, artifacts);
     }
 
     private boolean isProvidedArtifact(Artifact artifact) {
         return providedArtifacts.contains(artifact.getGroupId() + ":" + artifact.getArtifactId());
     }
 
     public ClassRealm createPluginRealm(
             Plugin plugin,
             ClassLoader parent,
             List<String> parentImports,
             Map<String, ClassLoader> foreignImports,
             List<Artifact> artifacts) {
         Objects.requireNonNull(plugin, "plugin cannot be null");
 
         if (parent == null) {
             parent = PARENT_CLASSLOADER;
         }
 
         return createRealm(getKey(plugin, false), RealmType.Plugin, parent, parentImports, foreignImports, artifacts);
     }
 
     private static String getKey(Plugin plugin, boolean extension) {
         String version = ArtifactUtils.toSnapshotVersion(plugin.getVersion());
         return (extension ? "extension>" : "plugin>") + plugin.getGroupId() + ":" + plugin.getArtifactId() + ":"
                 + version;
     }
 
     private static String getId(Artifact artifact) {
         return getId(
                 artifact.getGroupId(),
                 artifact.getArtifactId(),
                 artifact.getExtension(),
                 artifact.getClassifier(),
                 artifact.getBaseVersion());
     }
 
     private static String getId(ClassRealmConstituent constituent) {
         return getId(
                 constituent.getGroupId(),
                 constituent.getArtifactId(),
                 constituent.getType(),
                 constituent.getClassifier(),
                 constituent.getVersion());
     }
 
     private static String getId(String gid, String aid, String type, String cls, String ver) {
         return gid + ':' + aid + ':' + type + ((cls != null && !cls.isEmpty()) ? ':' + cls : "") + ':' + ver;
     }
 
     private void callDelegates(
             ClassRealm classRealm,
             RealmType type,
             ClassLoader parent,
             List<String> parentImports,
             Map<String, ClassLoader> foreignImports,
             List<ClassRealmConstituent> constituents) {
         List<ClassRealmManagerDelegate> delegates = new ArrayList<>(this.delegates);
 
         if (!delegates.isEmpty()) {
             ClassRealmRequest request =
                     new DefaultClassRealmRequest(type, parent, parentImports, foreignImports, constituents);
 
             for (ClassRealmManagerDelegate delegate : delegates) {
                 try {
                     delegate.setupRealm(classRealm, request);
                 } catch (Exception e) {
                     logger.error(
                             delegate.getClass().getName() + " failed to setup class realm " + classRealm + ": "
                                     + e.getMessage(),
                             e);
                 }
             }
         }
     }
 
     private Set<String> populateRealm(ClassRealm classRealm, List<ClassRealmConstituent> constituents) {
         Set<String> includedIds = new LinkedHashSet<>();
 
         if (logger.isDebugEnabled()) {
             logger.debug("Populating class realm " + classRealm.getId());
         }
 
         for (ClassRealmConstituent constituent : constituents) {
             File file = constituent.getFile();
 
             String id = getId(constituent);
             includedIds.add(id);
 
             if (logger.isDebugEnabled()) {
                 logger.debug("  Included: " + id);
             }
 
             try {
                 classRealm.addURL(file.toURI().toURL());
             } catch (MalformedURLException e) {
                 // Not going to happen
                 logger.error(e.getMessage(), e);
             }
         }
 
         return includedIds;
     }
 
     private void wireRealm(ClassRealm classRealm, List<String> parentImports, Map<String, ClassLoader> foreignImports) {
         if (foreignImports != null && !foreignImports.isEmpty()) {
             if (logger.isDebugEnabled()) {
                 logger.debug("Importing foreign packages into class realm " + classRealm.getId());
             }
 
             for (Map.Entry<String, ClassLoader> entry : foreignImports.entrySet()) {
                 ClassLoader importedRealm = entry.getValue();
                 String imp = entry.getKey();
 
                 if (logger.isDebugEnabled()) {
                     logger.debug("  Imported: " + imp + " < " + getId(importedRealm));
                 }
 
                 classRealm.importFrom(importedRealm, imp);
             }
         }
 
         if (parentImports != null && !parentImports.isEmpty()) {
             if (logger.isDebugEnabled()) {
                 logger.debug("Importing parent packages into class realm " + classRealm.getId());
             }
 
             for (String imp : parentImports) {
                 if (logger.isDebugEnabled()) {
                     logger.debug("  Imported: " + imp + " < " + getId(classRealm.getParentClassLoader()));
                 }
 
                 classRealm.importFromParent(imp);
             }
         }
     }
 
     private String getId(ClassLoader classLoader) {
         if (classLoader instanceof ClassRealm) {
             return ((ClassRealm) classLoader).getId();
         }
         return String.valueOf(classLoader);
     }
 }