package org.apache.maven.plugin;
   
   /*
    * 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.util.ArrayList;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  
  import org.apache.maven.project.ExtensionDescriptor;
  import org.apache.maven.project.MavenProject;
  import org.codehaus.plexus.classworlds.realm.ClassRealm;
  import org.codehaus.plexus.component.annotations.Component;
  import org.sonatype.aether.artifact.Artifact;
  
  /**
   * Default extension realm cache implementation. Assumes cached data does not change.
   */
  @Component( role = ExtensionRealmCache.class )
  public class DefaultExtensionRealmCache
      implements ExtensionRealmCache
  {
  
      private static class CacheKey
      {
  
          private final List<File> files;
  
          private final List<Long> timestamps;
  
          private final List<Long> sizes;
  
          private final List<String> ids;
  
          private final int hashCode;
  
          public CacheKey( List<? extends Artifact> extensionArtifacts )
          {
              this.files = new ArrayList<File>( extensionArtifacts.size() );
              this.timestamps = new ArrayList<Long>( extensionArtifacts.size() );
              this.sizes = new ArrayList<Long>( extensionArtifacts.size() );
              this.ids = new ArrayList<String>( extensionArtifacts.size() );
  
              for ( Artifact artifact : extensionArtifacts )
              {
                  File file = artifact.getFile();
                  files.add( file );
                  timestamps.add( ( file != null ) ? Long.valueOf( file.lastModified() ) : Long.valueOf( 0 ) );
                  sizes.add( ( file != null ) ? Long.valueOf( file.length() ) : Long.valueOf( 0 ) );
                  ids.add( artifact.getVersion() );
              }
  
              this.hashCode =
                  31 * files.hashCode() + 31 * ids.hashCode() + 31 * timestamps.hashCode() + 31 * sizes.hashCode();
          }
  
          @Override
          public int hashCode()
          {
              return hashCode;
          }
  
          @Override
          public boolean equals( Object o )
          {
              if ( o == this )
              {
                  return true;
              }
  
              if ( !( o instanceof CacheKey ) )
              {
                  return false;
              }
  
              CacheKey other = (CacheKey) o;
  
              return ids.equals( other.ids ) && files.equals( other.files ) && timestamps.equals( other.timestamps )
                  && sizes.equals( other.sizes );
          }
  
     }
 
     private final Map<CacheKey, CacheRecord> cache = new HashMap<CacheKey, CacheRecord>();
 
     public CacheRecord get( List<? extends Artifact> extensionArtifacts )
     {
         return cache.get( new CacheKey( extensionArtifacts ) );
     }
 
     public CacheRecord put( List<? extends Artifact> extensionArtifacts, ClassRealm extensionRealm,
                             ExtensionDescriptor extensionDescriptor )
     {
         if ( extensionRealm == null )
         {
             throw new NullPointerException();
         }
 
         CacheKey key = new CacheKey( extensionArtifacts );
 
         if ( cache.containsKey( key ) )
         {
             throw new IllegalStateException( "Duplicate extension realm for extension " + extensionArtifacts );
         }
 
         CacheRecord record = new CacheRecord( extensionRealm, extensionDescriptor );
 
         cache.put( key, record );
 
         return record;
     }
 
     public void flush()
     {
         cache.clear();
     }
 
     public void register( MavenProject project, CacheRecord record )
     {
         // default cache does not track extension usage
     }
 
 }