package org.eclipse.aether.collection;
   
   /*
    * 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.Collection;
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.LinkedHashSet;
  import java.util.List;
  
  import org.eclipse.aether.RepositoryException;
  import org.eclipse.aether.artifact.Artifact;
  import org.eclipse.aether.graph.DependencyNode;
  import org.eclipse.aether.version.VersionConstraint;
  
  /**
   * Thrown in case of an unsolvable conflict between different version constraints for a dependency.
   */
  public class UnsolvableVersionConflictException
      extends RepositoryException
  {
  
      private final transient Collection<String> versions;
  
      private final transient Collection<? extends List<? extends DependencyNode>> paths;
  
      /**
       * Creates a new exception with the specified paths to conflicting nodes in the dependency graph.
       * 
       * @param paths The paths to the dependency nodes that participate in the version conflict, may be {@code null}.
       */
      public UnsolvableVersionConflictException( Collection<? extends List<? extends DependencyNode>> paths )
      {
          super( "Could not resolve version conflict among " + toPaths( paths ) );
          if ( paths == null )
          {
              this.paths = Collections.emptyList();
              this.versions = Collections.emptyList();
          }
          else
          {
              this.paths = paths;
              this.versions = new LinkedHashSet<String>();
              for ( List<? extends DependencyNode> path : paths )
              {
                  VersionConstraint constraint = path.get( path.size() - 1 ).getVersionConstraint();
                  if ( constraint != null && constraint.getRange() != null )
                  {
                      versions.add( constraint.toString() );
                  }
              }
          }
      }
  
      private static String toPaths( Collection<? extends List<? extends DependencyNode>> paths )
      {
          String result = "";
  
          if ( paths != null )
          {
              Collection<String> strings = new LinkedHashSet<String>();
  
              for ( List<? extends DependencyNode> path : paths )
              {
                  strings.add( toPath( path ) );
              }
  
              result = strings.toString();
          }
  
          return result;
      }
  
      private static String toPath( List<? extends DependencyNode> path )
      {
          StringBuilder buffer = new StringBuilder( 256 );
  
          for ( Iterator<? extends DependencyNode> it = path.iterator(); it.hasNext(); )
          {
              DependencyNode node = it.next();
              if ( node.getDependency() == null )
              {
                 continue;
             }
 
             Artifact artifact = node.getDependency().getArtifact();
             buffer.append( artifact.getGroupId() );
             buffer.append( ':' ).append( artifact.getArtifactId() );
             buffer.append( ':' ).append( artifact.getExtension() );
             if ( artifact.getClassifier().length() > 0 )
             {
                 buffer.append( ':' ).append( artifact.getClassifier() );
             }
             buffer.append( ':' ).append( node.getVersionConstraint() );
 
             if ( it.hasNext() )
             {
                 buffer.append( " -> " );
             }
         }
 
         return buffer.toString();
     }
 
     /**
      * Gets the paths leading to the conflicting dependencies.
      * 
      * @return The (read-only) paths leading to the conflicting dependencies, never {@code null}.
      */
     public Collection<? extends List<? extends DependencyNode>> getPaths()
     {
         return paths;
     }
 
     /**
      * Gets the conflicting version constraints of the dependency.
      * 
      * @return The (read-only) conflicting version constraints, never {@code null}.
      */
     public Collection<String> getVersions()
     {
         return versions;
     }
 
 }