package org.apache.maven.lifecycle.internal.builder.multithreaded;
   
   /*
    * 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 org.apache.maven.execution.ProjectDependencyGraph;
  import org.apache.maven.lifecycle.internal.ProjectBuildList;
  import org.apache.maven.lifecycle.internal.ProjectSegment;
  import org.apache.maven.project.MavenProject;
  
  import java.util.ArrayList;
  import java.util.HashSet;
  import java.util.LinkedHashSet;
  import java.util.List;
  import java.util.Set;
  
  /**
   * <p>
   * Presents a view of the Dependency Graph that is suited for concurrent building.
   * </p>
   * <strong>NOTE:</strong> This class is not part of any public api and can be changed or deleted without prior notice.
   *
   * @since 3.0
   * @author Kristian Rosenvold
   */
  public class ConcurrencyDependencyGraph
  {
  
      private final ProjectBuildList projectBuilds;
  
      private final ProjectDependencyGraph projectDependencyGraph;
  
      private final Set<MavenProject> finishedProjects = new HashSet<>();
  
      public ConcurrencyDependencyGraph( ProjectBuildList projectBuilds, ProjectDependencyGraph projectDependencyGraph )
      {
          this.projectDependencyGraph = projectDependencyGraph;
          this.projectBuilds = projectBuilds;
      }
  
      public int getNumberOfBuilds()
      {
          return projectBuilds.size();
      }
  
      /**
       * Gets all the builds that have no reactor-dependencies
       *
       * @return A set of all the initial builds
       */
  
      public List<MavenProject> getRootSchedulableBuilds()
      {
          Set<MavenProject> result = new LinkedHashSet<>();
          for ( ProjectSegment projectBuild : projectBuilds )
          {
              if ( projectDependencyGraph.getUpstreamProjects( projectBuild.getProject(), false ).isEmpty() )
              {
                  result.add( projectBuild.getProject() );
              }
          }
          return new ArrayList<>( result );
      }
  
      /**
       * Marks the provided project as finished. Returns a list of
       *
       * @param mavenProject The project
       * @return The list of builds that are eligible for starting now that the provided project is done
       */
      public List<MavenProject> markAsFinished( MavenProject mavenProject )
      {
          finishedProjects.add( mavenProject );
          return getSchedulableNewProcesses( mavenProject );
      }
  
      private List<MavenProject> getSchedulableNewProcesses( MavenProject finishedProject )
      {
          List<MavenProject> result = new ArrayList<>();
          // schedule dependent projects, if all of their requirements are met
          for ( MavenProject dependentProject : projectDependencyGraph.getDownstreamProjects( finishedProject, false ) )
          {
              final List<MavenProject> upstreamProjects =
                 projectDependencyGraph.getUpstreamProjects( dependentProject, false );
             if ( finishedProjects.containsAll( upstreamProjects ) )
             {
                 result.add( dependentProject );
             }
         }
         return result;
     }
 
     /**
      * @return set of projects that have yet to be processed successfully by the build.
      */
     public Set<MavenProject> getUnfinishedProjects()
     {
         Set<MavenProject> unfinished = new HashSet<>( projectBuilds.getProjects() );
         unfinished.removeAll( finishedProjects );
         return unfinished;
     }
 
     /**
      * @return set of projects that have been successfully processed by the build.
      */
     protected Set<MavenProject> getFinishedProjects()
     {
         return finishedProjects;
     }
 
     protected ProjectBuildList getProjectBuilds()
     {
         return projectBuilds;
     }
 
     /**
      * For the given {@link MavenProject} {@code p}, return all of {@code p}'s dependencies.
      *
      * @param p
      * @return List of prerequisite projects
      */
     protected List<MavenProject> getDependencies( MavenProject p )
     {
         return projectDependencyGraph.getUpstreamProjects( p, false );
     }
 
     /**
      * For the given {@link MavenProject} {@code p} return {@code p}'s uncompleted dependencies.
      *
      * @param p
      * @return List of uncompleted prerequisite projects
      */
     public List<MavenProject> getActiveDependencies( MavenProject p )
     {
         List<MavenProject> activeDependencies = projectDependencyGraph.getUpstreamProjects( p, false );
         activeDependencies.removeAll( finishedProjects );
         return activeDependencies;
     }
 }