package org.apache.maven.artifact.resolver;
   
   /*
    * 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.Collections;
  import java.util.Iterator;
  import java.util.LinkedList;
  import java.util.List;
  import java.util.Set;
  
  import org.apache.maven.artifact.Artifact;
  import org.apache.maven.artifact.repository.ArtifactRepository;
  import org.apache.maven.artifact.resolver.filter.ArtifactFilter;
  import org.apache.maven.artifact.versioning.ArtifactVersion;
  import org.apache.maven.artifact.versioning.OverConstrainedVersionException;
  
  /**
   * ResolutionNode
   */
  public class ResolutionNode
  {
      private Artifact artifact;
  
      private List<ResolutionNode> children;
  
      private final List<Object> parents;
  
      private final int depth;
  
      private final ResolutionNode parent;
  
      private final List<ArtifactRepository> remoteRepositories;
  
      private boolean active = true;
  
      private List<Artifact> trail;
  
      public ResolutionNode( Artifact artifact, List<ArtifactRepository> remoteRepositories )
      {
          this.artifact = artifact;
          this.remoteRepositories = remoteRepositories;
          depth = 0;
          parents = Collections.emptyList();
          parent = null;
      }
  
      public ResolutionNode( Artifact artifact, List<ArtifactRepository> remoteRepositories, ResolutionNode parent )
      {
          this.artifact = artifact;
          this.remoteRepositories = remoteRepositories;
          depth = parent.depth + 1;
          parents = new ArrayList<>();
          parents.addAll( parent.parents );
          parents.add( parent.getKey() );
          this.parent = parent;
      }
  
      public Artifact getArtifact()
      {
          return artifact;
      }
  
      public Object getKey()
      {
          return artifact.getDependencyConflictId();
      }
  
      public void addDependencies( Set<Artifact> artifacts, List<ArtifactRepository> remoteRepositories,
                                   ArtifactFilter filter )
          throws CyclicDependencyException, OverConstrainedVersionException
      {
          if ( artifacts != null && !artifacts.isEmpty() )
          {
              children = new ArrayList<>( artifacts.size() );
  
              for ( Artifact a : artifacts )
              {
                  if ( parents.contains( a.getDependencyConflictId() ) )
                  {
                      a.setDependencyTrail( getDependencyTrail() );
  
                     throw new CyclicDependencyException( "A dependency has introduced a cycle", a );
                 }
 
                 children.add( new ResolutionNode( a, remoteRepositories, this ) );
             }
             children = Collections.unmodifiableList( children );
         }
         else
         {
             children = Collections.emptyList();
         }
         trail = null;
     }
 
     /**
      * @return {@link List} &lt; {@link String} &gt; with artifact ids
      * @throws OverConstrainedVersionException if version specification is over constrained
      */
     public List<String> getDependencyTrail()
         throws OverConstrainedVersionException
     {
         List<Artifact> trial = getTrail();
 
         List<String> ret = new ArrayList<>( trial.size() );
 
         for ( Artifact artifact : trial )
         {
             ret.add( artifact.getId() );
         }
 
         return ret;
     }
 
     private List<Artifact> getTrail()
         throws OverConstrainedVersionException
     {
         if ( trail == null )
         {
             List<Artifact> ids = new LinkedList<>();
             ResolutionNode node = this;
             while ( node != null )
             {
                 Artifact artifact = node.getArtifact();
                 if ( artifact.getVersion() == null )
                 {
                     // set the recommended version
                     ArtifactVersion selected = artifact.getSelectedVersion();
                     // MNG-2123: null is a valid response to getSelectedVersion, don't
                     // assume it won't ever be.
                     if ( selected != null )
                     {
                         artifact.selectVersion( selected.toString() );
                     }
                     else
                     {
                         throw new OverConstrainedVersionException( "Unable to get a selected Version for "
                             + artifact.getArtifactId(), artifact );
                     }
                 }
 
                 ids.add( 0, artifact );
                 node = node.parent;
             }
             trail = ids;
         }
         return trail;
     }
 
     public boolean isResolved()
     {
         return children != null;
     }
 
     /**
      * Test whether the node is direct or transitive dependency.
      *
      * @return whether the node is direct or transitive dependency
      */
     public boolean isChildOfRootNode()
     {
         return parent != null && parent.parent == null;
     }
 
     public Iterator<ResolutionNode> getChildrenIterator()
     {
         return children.iterator();
     }
 
     public int getDepth()
     {
         return depth;
     }
 
     public List<ArtifactRepository> getRemoteRepositories()
     {
         return remoteRepositories;
     }
 
     public boolean isActive()
     {
         return active;
     }
 
     public void enable()
     {
         active = true;
 
         // TODO if it was null, we really need to go find them now... or is this taken care of by the ordering?
         if ( children != null )
         {
             for ( ResolutionNode node : children )
             {
                 node.enable();
             }
         }
     }
 
     public void disable()
     {
         active = false;
         if ( children != null )
         {
             for ( ResolutionNode node : children )
             {
                 node.disable();
             }
         }
     }
 
     public boolean filterTrail( ArtifactFilter filter )
         throws OverConstrainedVersionException
     {
         boolean success = true;
         if ( filter != null )
         {
             for ( Artifact artifact : getTrail() )
             {
                 if ( !filter.include( artifact ) )
                 {
                     success = false;
                 }
             }
         }
         return success;
     }
 
     @Override
     public String toString()
     {
         return artifact.toString() + " (" + depth + "; " + ( active ? "enabled" : "disabled" ) + ")";
     }
 
     public void setArtifact( Artifact artifact )
     {
         this.artifact = artifact;
     }
 
 }