/*
    * 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.repository.metadata;
  
  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<>(g.getVertices().size());
         visit(g.getEntry(), visited, g);
 
         List<MetadataGraphVertex> dropList = new ArrayList<>(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;
     }
     // -------------------------------------------------------------------------------------
     // -------------------------------------------------------------------------------------
 }