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.Comparator;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Map;
  import java.util.Objects;
  import java.util.Set;
  import java.util.stream.Collectors;
  
  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 interdependencies between projects in the reactor.
   *
   * @author Benjamin Bentmann
   */
  public class DefaultProjectDependencyGraph
          implements ProjectDependencyGraph
  {
  
      private final ProjectSorter sorter;
  
      private final List<MavenProject> allProjects;
  
      private final Map<MavenProject, Integer> order;
  
      private final Map<String, MavenProject> projects;
  
      /**
       * 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
      {
          this( projects, 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( Collection<MavenProject> allProjects,
                                            Collection<MavenProject> projects )
              throws CycleDetectedException, DuplicateProjectException
      {
          this.allProjects = Collections.unmodifiableList( new ArrayList<>( allProjects ) );
          this.sorter = new ProjectSorter( projects );
          this.order = new HashMap<>();
          this.projects = new HashMap<>();
          List<MavenProject> sorted = this.sorter.getSortedProjects();
          for ( int index = 0; index < sorted.size(); index++ )
          {
              MavenProject project = sorted.get( index );
              String id = ProjectSorter.getId( project );
              this.projects.put( id, project );
              this.order.put( project, index );
          }
      }
  
      /**
       * @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 )
     {
         return projectIds.stream()
                 .map( projects::get )
                 .sorted( Comparator.comparingInt( order::get ) )
                 .collect( Collectors.toList() );
     }
 
     @Override
     public String toString()
     {
         return sorter.getSortedProjects().toString();
     }
 
 }