package org.apache.maven.project;
   
   /*
    * 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.util.Collections;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  
  import org.codehaus.plexus.classworlds.realm.ClassRealm;
  import org.codehaus.plexus.component.annotations.Component;
  import org.sonatype.aether.graph.DependencyFilter;
  
  /**
   * Default project realm cache implementation. Assumes cached data does not change.
   */
  @Component( role = ProjectRealmCache.class )
  public class DefaultProjectRealmCache
      implements ProjectRealmCache
  {
  
      private static class CacheKey
      {
  
          private final List<? extends ClassRealm> extensionRealms;
  
          private final int hashCode;
  
          public CacheKey( List<? extends ClassRealm> extensionRealms )
          {
              this.extensionRealms = ( extensionRealms != null ) ? extensionRealms : Collections.<ClassRealm> emptyList();
  
              this.hashCode = this.extensionRealms.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 extensionRealms.equals( other.extensionRealms );
          }
  
      }
  
      private final Map<CacheKey, CacheRecord> cache = new HashMap<CacheKey, CacheRecord>();
  
      public CacheRecord get( List<? extends ClassRealm> extensionRealms )
      {
          return cache.get( new CacheKey( extensionRealms ) );
      }
  
      public CacheRecord put( List<? extends ClassRealm> extensionRealms, ClassRealm projectRealm,
                              DependencyFilter extensionArtifactFilter )
      {
          if ( projectRealm == null )
          {
              throw new NullPointerException();
          }
  
          CacheKey key = new CacheKey( extensionRealms );
  
          if ( cache.containsKey( key ) )
          {
              throw new IllegalStateException( "Duplicate project realm for extensions " + extensionRealms );
          }
 
         CacheRecord record = new CacheRecord( projectRealm, extensionArtifactFilter );
 
         cache.put( key, record );
 
         return record;
     }
 
     public void flush()
     {
         cache.clear();
     }
 
     public void register( MavenProject project, CacheRecord record )
     {
         // default cache does not track record usage
     }
 
 }