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.Collections;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Objects;
  import java.util.Set;
  
  import org.apache.maven.execution.ProjectDependencyGraph;
  import org.apache.maven.project.DuplicateProjectException;
  import org.apache.maven.project.MavenProject;
  import org.apache.maven.project.ProjectSorter;
  import org.codehaus.plexus.util.dag.CycleDetectedException;
  
  /**
   * Describes the inter-dependencies between projects in the reactor.
   *
   * @author Benjamin Bentmann
   */
  public class DefaultProjectDependencyGraph
      implements ProjectDependencyGraph
  {
  
      private ProjectSorter sorter;
  
      private List<MavenProject> allProjects;
  
      /**
       * Creates a new project dependency graph based on the specified projects.
       *
       * @param projects The projects to create the dependency graph with
       * @throws DuplicateProjectException
       * @throws CycleDetectedException
       */
      public DefaultProjectDependencyGraph( Collection<MavenProject> projects )
          throws CycleDetectedException, DuplicateProjectException
      {
          super();
          this.allProjects = Collections.unmodifiableList( new ArrayList<>( projects ) );
          this.sorter = new ProjectSorter( projects );
      }
  
      /**
       * Creates a new project dependency graph based on the specified projects.
       *
       * @param allProjects All collected projects.
       * @param projects The projects to create the dependency graph with.
       *
       * @throws DuplicateProjectException
       * @throws CycleDetectedException
       * @since 3.5.0
       */
      public DefaultProjectDependencyGraph( final List<MavenProject> allProjects,
                                            final Collection<MavenProject> projects )
          throws CycleDetectedException, DuplicateProjectException
      {
          super();
          this.allProjects = Collections.unmodifiableList( new ArrayList<>( allProjects ) );
          this.sorter = new ProjectSorter( projects );
      }
  
      /**
       * @since 3.5.0
       */
      public List<MavenProject> getAllProjects()
      {
          return this.allProjects;
      }
  
      public List<MavenProject> getSortedProjects()
      {
          return new ArrayList<>( sorter.getSortedProjects() );
      }
  
      public List<MavenProject> getDownstreamProjects( MavenProject project, boolean transitive )
      {
          Objects.requireNonNull( project, "project cannot be null" );
  
         Set<String> projectIds = new HashSet<>();
 
         getDownstreamProjects( ProjectSorter.getId( project ), projectIds, transitive );
 
         return getSortedProjects( projectIds );
     }
 
     private void getDownstreamProjects( String projectId, Set<String> projectIds, boolean transitive )
     {
         for ( String id : sorter.getDependents( projectId ) )
         {
             if ( projectIds.add( id ) && transitive )
             {
                 getDownstreamProjects( id, projectIds, transitive );
             }
         }
     }
 
     public List<MavenProject> getUpstreamProjects( MavenProject project, boolean transitive )
     {
         Objects.requireNonNull( project, "project cannot be null" );
 
         Set<String> projectIds = new HashSet<>();
 
         getUpstreamProjects( ProjectSorter.getId( project ), projectIds, transitive );
 
         return getSortedProjects( 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> getSortedProjects( Set<String> projectIds )
     {
         List<MavenProject> result = new ArrayList<>( projectIds.size() );
 
         for ( MavenProject mavenProject : sorter.getSortedProjects() )
         {
             if ( projectIds.contains( ProjectSorter.getId( mavenProject ) ) )
             {
                 result.add( mavenProject );
             }
         }
 
         return result;
     }
 
     @Override
     public String toString()
     {
         return sorter.getSortedProjects().toString();
     }
 
 }