/*
    * 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.
   */
  package org.apache.maven.lifecycle.internal.builder.multithreaded;
  
  import java.util.ArrayList;
  import java.util.HashSet;
  import java.util.LinkedHashSet;
  import java.util.List;
  import java.util.Set;
  
  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;
  
  /**
   * <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
   */
  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());
              }
          }
          if (result.isEmpty() && projectBuilds.size() > 0) {
              // Must return at least one project
              result.add(projectBuilds.get(0).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;
     }
 }