package org.apache.maven.graph;
   
   /*
    * 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.ArrayList;
  import java.util.Collection;
  import java.util.IdentityHashMap;
  import java.util.List;
  import java.util.Map;
  
  import org.apache.commons.lang3.Validate;
  import org.apache.maven.execution.ProjectDependencyGraph;
  import org.apache.maven.project.MavenProject;
  
  /**
   * Provides a sub view of another dependency graph.
   *
   * @author Benjamin Bentmann
   */
  class FilteredProjectDependencyGraph
      implements ProjectDependencyGraph
  {
  
      private ProjectDependencyGraph projectDependencyGraph;
  
      private Map<MavenProject, ?> whiteList;
  
      private List<MavenProject> sortedProjects;
  
      /**
       * Creates a new project dependency graph from the specified graph.
       *
       * @param projectDependencyGraph The project dependency graph to create a sub view from, must not be {@code null}.
       * @param whiteList The projects on which the dependency view should focus, must not be {@code null}.
       */
      public FilteredProjectDependencyGraph( ProjectDependencyGraph projectDependencyGraph,
                                             Collection<? extends MavenProject> whiteList )
      {
          this.projectDependencyGraph =
              Validate.notNull( projectDependencyGraph, "projectDependencyGraph cannot be null" );
  
          this.whiteList = new IdentityHashMap<MavenProject, Object>();
  
          for ( MavenProject project : whiteList )
          {
              this.whiteList.put( project, null );
          }
      }
  
      public List<MavenProject> getSortedProjects()
      {
          if ( sortedProjects == null )
          {
              sortedProjects = applyFilter( projectDependencyGraph.getSortedProjects() );
          }
  
          return new ArrayList<>( sortedProjects );
      }
  
      public List<MavenProject> getDownstreamProjects( MavenProject project, boolean transitive )
      {
          return applyFilter( projectDependencyGraph.getDownstreamProjects( project, transitive ) );
      }
  
      public List<MavenProject> getUpstreamProjects( MavenProject project, boolean transitive )
      {
          return applyFilter( projectDependencyGraph.getUpstreamProjects( project, transitive ) );
      }
  
      private List<MavenProject> applyFilter( Collection<? extends MavenProject> projects )
      {
          List<MavenProject> filtered = new ArrayList<>( projects.size() );
  
          for ( MavenProject project : projects )
          {
              if ( whiteList.containsKey( project ) )
              {
                  filtered.add( project );
              }
          }
  
          return filtered;
     }
 
     @Override
     public String toString()
     {
         return getSortedProjects().toString();
     }
 
 }