package org.apache.maven;
   
   /*
    * 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.HashSet;
  import java.util.List;
  
  import org.apache.maven.execution.ProjectDependencyGraph;
  import org.apache.maven.project.MavenProject;
  import org.apache.maven.project.ProjectSorter;
  
  /**
   * Describes the inter-dependencies between projects in the reactor.
   * 
   * @author Benjamin Bentmann
   */
  class DefaultProjectDependencyGraph
      implements ProjectDependencyGraph
  {
  
      private ProjectSorter sorter;
  
      /**
       * Creates a new project dependency graph based on the specified project sorting.
       * 
       * @param sorter The project sorter backing the graph, must not be {@code null}.
       */
      public DefaultProjectDependencyGraph( ProjectSorter sorter )
      {
          if ( sorter == null )
          {
              throw new IllegalArgumentException( "project sorter missing" );
          }
  
          this.sorter = sorter;
      }
  
      public List<MavenProject> getSortedProjects()
      {
          return new ArrayList<MavenProject>( sorter.getSortedProjects() );
      }
  
      public List<MavenProject> getDownstreamProjects( MavenProject project, boolean transitive )
      {
          if ( project == null )
          {
              throw new IllegalArgumentException( "project missing" );
          }
  
          Collection<String> projectIds = new HashSet<String>();
  
          getDownstreamProjects( ProjectSorter.getId( project ), projectIds, transitive );
  
          return getProjects( projectIds );
      }
  
      private void getDownstreamProjects( String projectId, Collection<String> projectIds, boolean transitive )
      {
          for ( String id : sorter.getDependents( projectId ) )
          {
              if ( projectIds.add( id ) )
              {
                  if ( transitive )
                  {
                      getDownstreamProjects( id, projectIds, transitive );
                  }
              }
          }
      }
  
      public List<MavenProject> getUpstreamProjects( MavenProject project, boolean transitive )
      {
          if ( project == null )
          {
              throw new IllegalArgumentException( "project missing" );
          }
  
          Collection<String> projectIds = new HashSet<String>();
  
          getUpstreamProjects( ProjectSorter.getId( project ), projectIds, transitive );
 
         return getProjects( projectIds );
     }
 
     private void getUpstreamProjects( String projectId, Collection<String> projectIds, boolean transitive )
     {
         for ( String id : sorter.getDependencies( projectId ) )
         {
             if ( projectIds.add( id ) && transitive )
             {
                 getUpstreamProjects( id, projectIds, transitive );
             }
         }
     }
 
     private List<MavenProject> getProjects( Collection<String> projectIds )
     {
         List<MavenProject> projects = new ArrayList<MavenProject>();
 
         for ( MavenProject p : sorter.getSortedProjects() )
         {
             if ( projectIds.contains( ProjectSorter.getId( p ) ) )
             {
                 projects.add( p );
             }
         }
 
         return projects;
     }
 
     @Override
     public String toString()
     {
         return sorter.getSortedProjects().toString();
     }
 
 }