/*
    * 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.graph;
  
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.IdentityHashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.Objects;
  
  import org.apache.maven.execution.ProjectDependencyGraph;
  import org.apache.maven.project.MavenProject;
  
  /**
   * Provides a sub view of another dependency graph.
   *
   * @author Benjamin Bentmann
   */
  class FilteredProjectDependencyGraph implements ProjectDependencyGraph {
  
      private ProjectDependencyGraph projectDependencyGraph;
  
      private Map<MavenProject, ?> whiteList;
  
      private List<MavenProject> sortedProjects;
  
      /**
       * Creates a new project dependency graph from the specified graph.
       *
       * @param projectDependencyGraph The project dependency graph to create a sub view from, must not be {@code null}.
       * @param whiteList The projects on which the dependency view should focus, must not be {@code null}.
       */
      FilteredProjectDependencyGraph(
              ProjectDependencyGraph projectDependencyGraph, Collection<? extends MavenProject> whiteList) {
          this.projectDependencyGraph =
                  Objects.requireNonNull(projectDependencyGraph, "projectDependencyGraph cannot be null");
  
          this.whiteList = new IdentityHashMap<MavenProject, Object>();
  
          for (MavenProject project : whiteList) {
              this.whiteList.put(project, null);
          }
      }
  
      /**
       * @since 3.5.0
       */
      public List<MavenProject> getAllProjects() {
          return this.projectDependencyGraph.getAllProjects();
      }
  
      public List<MavenProject> getSortedProjects() {
          if (sortedProjects == null) {
              sortedProjects = applyFilter(projectDependencyGraph.getSortedProjects());
          }
  
          return new ArrayList<>(sortedProjects);
      }
  
      public List<MavenProject> getDownstreamProjects(MavenProject project, boolean transitive) {
          return applyFilter(projectDependencyGraph.getDownstreamProjects(project, transitive));
      }
  
      public List<MavenProject> getUpstreamProjects(MavenProject project, boolean transitive) {
          return applyFilter(projectDependencyGraph.getUpstreamProjects(project, transitive));
      }
  
      private List<MavenProject> applyFilter(Collection<? extends MavenProject> projects) {
          List<MavenProject> filtered = new ArrayList<>(projects.size());
  
          for (MavenProject project : projects) {
              if (whiteList.containsKey(project)) {
                  filtered.add(project);
              }
          }
  
          return filtered;
      }
  
      @Override
      public String toString() {
          return getSortedProjects().toString();
     }
 }