package org.apache.maven.repository.metadata;
   
   /*
    * 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.List;
  import java.util.TreeSet;
  
  import org.apache.maven.artifact.ArtifactScopeEnum;
  import org.codehaus.plexus.component.annotations.Component;
  import org.codehaus.plexus.component.annotations.Requirement;
  
  /**
   * Default conflict resolver.Implements closer newer first policy by default, but could be configured via plexus
   *
   * @author <a href="mailto:oleg@codehaus.org">Oleg Gusakov</a>
   */
  @Component( role = GraphConflictResolver.class )
  public class DefaultGraphConflictResolver
      implements GraphConflictResolver
  {
      /**
       * artifact, closer to the entry point, is selected
       */
      @Requirement( role = GraphConflictResolutionPolicy.class )
      protected GraphConflictResolutionPolicy policy;
  
      // -------------------------------------------------------------------------------------
      // -------------------------------------------------------------------------------------
      public MetadataGraph resolveConflicts( MetadataGraph graph, ArtifactScopeEnum scope )
          throws GraphConflictResolutionException
      {
          if ( policy == null )
          {
              throw new GraphConflictResolutionException( "no GraphConflictResolutionPolicy injected" );
          }
  
          if ( graph == null )
          {
              return null;
          }
  
          final MetadataGraphVertex entry = graph.getEntry();
          if ( entry == null )
          {
              return null;
          }
  
          if ( graph.isEmpty() )
          {
              throw new GraphConflictResolutionException( "graph with an entry, but not vertices do not exist" );
          }
  
          if ( graph.isEmptyEdges() )
          {
              return null; // no edges - nothing to worry about
          }
  
          final TreeSet<MetadataGraphVertex> vertices = graph.getVertices();
  
          try
          {
              // edge case - single vertex graph
              if ( vertices.size() == 1 )
              {
                  return new MetadataGraph( entry );
              }
  
              final ArtifactScopeEnum requestedScope = ArtifactScopeEnum.checkScope( scope );
  
              MetadataGraph res = new MetadataGraph( vertices.size() );
              res.setVersionedVertices( false );
              res.setScopedVertices( false );
  
              MetadataGraphVertex resEntry = res.addVertex( entry.getMd() );
              res.setEntry( resEntry );
  
              res.setScope( requestedScope );
  
              for ( MetadataGraphVertex v : vertices )
              {
                  final List<MetadataGraphEdge> ins = graph.getIncidentEdges( v );
                 final MetadataGraphEdge edge = cleanEdges( v, ins, requestedScope );
 
                 if ( edge == null )
                 { // no edges - don't need this vertex any more
                     if ( entry.equals( v ) )
                     { // unless it's an entry point.
                         // currently processing the entry point - it should not have any entry incident edges
                         res.getEntry().getMd().setWhy( "This is a graph entry point. No links." );
                     }
                     else
                     {
                         // System.out.println("--->"+v.getMd().toDomainString()
                         // +" has been terminated on this entry set\n-------------------\n"
                         // +ins
                         // +"\n-------------------\n"
                         // );
                     }
                 }
                 else
                 {
                     // System.out.println("+++>"+v.getMd().toDomainString()+" still has "+edge.toString() );
                     // fill in domain md with actual version data
                     ArtifactMetadata md = v.getMd();
                     ArtifactMetadata newMd =
                         new ArtifactMetadata( md.getGroupId(), md.getArtifactId(), edge.getVersion(), md.getType(),
                                               md.getScopeAsEnum(), md.getClassifier(), edge.getArtifactUri(),
                                               edge.getSource() == null ? "" : edge.getSource().getMd().toString(),
                                               edge.isResolved(), edge.getTarget() == null ? null
                                                               : edge.getTarget().getMd().getError() );
                     MetadataGraphVertex newV = res.addVertex( newMd );
                     MetadataGraphVertex sourceV = res.addVertex( edge.getSource().getMd() );
 
                     res.addEdge( sourceV, newV, edge );
                 }
             }
             MetadataGraph linkedRes = findLinkedSubgraph( res );
             // System.err.println("Original graph("+graph.getVertices().size()+"):\n"+graph.toString());
             // System.err.println("Cleaned("+requestedScope+") graph("+res.getVertices().size()+"):\n"+res.toString());
             // System.err.println("Linked("+requestedScope+")
             // subgraph("+linkedRes.getVertices().size()+"):\n"+linkedRes.toString());
             return linkedRes;
         }
         catch ( MetadataResolutionException e )
         {
             throw new GraphConflictResolutionException( e );
         }
     }
 
     // -------------------------------------------------------------------------------------
     private MetadataGraph findLinkedSubgraph( MetadataGraph g )
     {
         if ( g.getVertices().size() == 1 )
         {
             return g;
         }
 
         List<MetadataGraphVertex> visited = new ArrayList<MetadataGraphVertex>( g.getVertices().size() );
         visit( g.getEntry(), visited, g );
 
         List<MetadataGraphVertex> dropList = new ArrayList<MetadataGraphVertex>( g.getVertices().size() );
 
         // collect drop list
         for ( MetadataGraphVertex v : g.getVertices() )
         {
             if ( !visited.contains( v ) )
             {
                 dropList.add( v );
             }
         }
 
         if ( dropList.size() < 1 )
         {
             return g;
         }
 
         // now - drop vertices
         TreeSet<MetadataGraphVertex> vertices = g.getVertices();
         for ( MetadataGraphVertex v : dropList )
         {
             vertices.remove( v );
         }
 
         return g;
     }
 
     // -------------------------------------------------------------------------------------
     private void visit( MetadataGraphVertex from, List<MetadataGraphVertex> visited, MetadataGraph graph )
     {
         if ( visited.contains( from ) )
         {
             return;
         }
 
         visited.add( from );
 
         List<MetadataGraphEdge> exitList = graph.getExcidentEdges( from );
         // String s = "|---> "+from.getMd().toString()+" - "+(exitList == null ? -1 : exitList.size()) + " exit links";
         if ( exitList != null && exitList.size() > 0 )
         {
             for ( MetadataGraphEdge e : graph.getExcidentEdges( from ) )
             {
                 visit( e.getTarget(), visited, graph );
             }
         }
     }
 
     // -------------------------------------------------------------------------------------
     private MetadataGraphEdge cleanEdges( MetadataGraphVertex v, List<MetadataGraphEdge> edges,
                                           ArtifactScopeEnum scope )
     {
         if ( edges == null || edges.isEmpty() )
         {
             return null;
         }
 
         if ( edges.size() == 1 )
         {
             MetadataGraphEdge e = edges.get( 0 );
             if ( scope.encloses( e.getScope() ) )
             {
                 return e;
             }
 
             return null;
         }
 
         MetadataGraphEdge res = null;
 
         for ( MetadataGraphEdge e : edges )
         {
             if ( !scope.encloses( e.getScope() ) )
             {
                 continue;
             }
 
             if ( res == null )
             {
                 res = e;
             }
             else
             {
                 res = policy.apply( e, res );
             }
         }
 
         return res;
     }
     // -------------------------------------------------------------------------------------
     // -------------------------------------------------------------------------------------
 }