package org.apache.maven.exception;
   
   /*
    * 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.io.IOException;
  import java.net.ConnectException;
  import java.net.UnknownHostException;
  import java.util.ArrayList;
  import java.util.List;
  
  import org.apache.maven.lifecycle.LifecycleExecutionException;
  import org.apache.maven.model.building.ModelProblem;
  import org.apache.maven.model.building.ModelProblemUtils;
  import org.apache.maven.plugin.AbstractMojoExecutionException;
  import org.apache.maven.plugin.MojoExecutionException;
  import org.apache.maven.plugin.MojoFailureException;
  import org.apache.maven.plugin.PluginContainerException;
  import org.apache.maven.plugin.PluginExecutionException;
  import org.apache.maven.project.ProjectBuildingException;
  import org.apache.maven.project.ProjectBuildingResult;
  import org.codehaus.plexus.component.annotations.Component;
  import org.codehaus.plexus.util.StringUtils;
  
  /*
  
  - test projects for each of these
  - how to categorize the problems so that the id of the problem can be match to a page with descriptive help and the test
    project
  - nice little sample projects that could be run in the core as well as integration tests
  
  All Possible Errors
  - invalid lifecycle phase (maybe same as bad CLI param, though you were talking about embedder too)
  - <module> specified is not found
  - malformed settings
  - malformed POM
  - local repository not writable
  - remote repositories not available
  - artifact metadata missing
  - extension metadata missing
  - extension artifact missing
  - artifact metadata retrieval problem
  - version range violation
  - circular dependency
  - artifact missing
  - artifact retrieval exception
  - md5 checksum doesn't match for local artifact, need to redownload this
  - POM doesn't exist for a goal that requires one
  - parent POM missing (in both the repository + relative path)
  - component not found
  
  Plugins:
  - plugin metadata missing
  - plugin metadata retrieval problem
  - plugin artifact missing
  - plugin artifact retrieval problem
  - plugin dependency metadata missing
  - plugin dependency metadata retrieval problem
  - plugin configuration problem
  - plugin execution failure due to something that is know to possibly go wrong (like compilation failure)
  - plugin execution error due to something that is not expected to go wrong (the compiler executable missing)
  - asking to use a plugin for which you do not have a version defined - tools to easily select versions
  - goal not found in a plugin (probably could list the ones that are)
  
   */
  
  //PluginNotFoundException, PluginResolutionException, PluginDescriptorParsingException, CycleDetectedInPluginGraphException;
  
  @Component( role = ExceptionHandler.class )
  public class DefaultExceptionHandler
      implements ExceptionHandler
  {
  
      public ExceptionSummary handleException( Throwable exception )
      {
          return handle( "", exception );
      }
  
      private ExceptionSummary handle( String message, Throwable exception )
      {
          String reference = getReference( exception );
  
          List<ExceptionSummary> children = null;
 
         if ( exception instanceof ProjectBuildingException )
         {
             List<ProjectBuildingResult> results = ( (ProjectBuildingException) exception ).getResults();
 
             children = new ArrayList<ExceptionSummary>();
 
             for ( ProjectBuildingResult result : results )
             {
                 ExceptionSummary child = handle( result );
                 if ( child != null )
                 {
                     children.add( child );
                 }
             }
 
             message = "The build could not read " + children.size() + " project" + ( children.size() == 1 ? "" : "s" );
         }
         else
         {
             message = getMessage( message, exception );
         }
 
         return new ExceptionSummary( exception, message, reference, children );
     }
 
     private ExceptionSummary handle( ProjectBuildingResult result )
     {
         List<ExceptionSummary> children = new ArrayList<ExceptionSummary>();
 
         for ( ModelProblem problem : result.getProblems() )
         {
             ExceptionSummary child = handle( problem, result.getProjectId() );
             if ( child != null )
             {
                 children.add( child );
             }
         }
 
         if ( children.isEmpty() )
         {
             return null;
         }
 
         String message =
             "\nThe project " + result.getProjectId() + " (" + result.getPomFile() + ") has "
                 + children.size() + " error" + ( children.size() == 1 ? "" : "s" );
 
         return new ExceptionSummary( null, message, null, children );
     }
 
     private ExceptionSummary handle( ModelProblem problem, String projectId )
     {
         if ( ModelProblem.Severity.ERROR.compareTo( problem.getSeverity() ) >= 0 )
         {
             String message = problem.getMessage();
 
             String location = ModelProblemUtils.formatLocation( problem, projectId );
 
             if ( StringUtils.isNotEmpty( location ) )
             {
                 message += " @ " + location;
             }
 
             return handle( message, problem.getException() );
         }
         else
         {
             return null;
         }
     }
 
     private String getReference( Throwable exception )
     {
         String reference = "";
 
         if ( exception != null )
         {
             if ( exception instanceof MojoExecutionException )
             {
                 reference = MojoExecutionException.class.getSimpleName();
 
                 Throwable cause = exception.getCause();
                 if ( cause instanceof IOException )
                 {
                     cause = cause.getCause();
                     if ( cause instanceof ConnectException )
                     {
                         reference = ConnectException.class.getSimpleName();
                     }
                 }
             }
             else if ( exception instanceof MojoFailureException )
             {
                 reference = MojoFailureException.class.getSimpleName();
             }
             else if ( exception instanceof LinkageError )
             {
                 reference = LinkageError.class.getSimpleName();
             }
             else if ( exception instanceof PluginExecutionException )
             {
                 Throwable cause = exception.getCause();
 
                 if ( cause instanceof PluginContainerException )
                 {
                     Throwable cause2 = cause.getCause();
 
                     if ( cause2 instanceof NoClassDefFoundError
                         && cause2.getMessage().contains( "org/sonatype/aether/" ) )
                     {
                         reference = "AetherClassNotFound";
                     }
                 }
 
                 if ( StringUtils.isEmpty( reference ) )
                 {
                     reference = getReference( cause );
                 }
 
                 if ( StringUtils.isEmpty( reference ) )
                 {
                     reference = exception.getClass().getSimpleName();
                 }
             }
             else if ( exception instanceof LifecycleExecutionException )
             {
                 reference = getReference( exception.getCause() );
             }
             else if ( isNoteworthyException( exception ) )
             {
                 reference = exception.getClass().getSimpleName();
             }
         }
 
         if ( StringUtils.isNotEmpty( reference ) && !reference.startsWith( "http:" ) )
         {
             reference = "http://cwiki.apache.org/confluence/display/MAVEN/" + reference;
         }
 
         return reference;
     }
 
     private boolean isNoteworthyException( Throwable exception )
     {
         if ( exception == null )
         {
             return false;
         }
         else if ( exception instanceof Error )
         {
             return true;
         }
         else if ( exception instanceof RuntimeException )
         {
             return false;
         }
         else if ( exception.getClass().getName().startsWith( "java" ) )
         {
             return false;
         }
         return true;
     }
 
     private String getMessage( String message, Throwable exception )
     {
         String fullMessage = ( message != null ) ? message : "";
 
         for ( Throwable t = exception; t != null; t = t.getCause() )
         {
             String exceptionMessage = t.getMessage();
 
             if ( t instanceof AbstractMojoExecutionException )
             {
                 String longMessage = ( (AbstractMojoExecutionException) t ).getLongMessage();
                 if ( StringUtils.isNotEmpty( longMessage ) )
                 {
                     if ( StringUtils.isEmpty( exceptionMessage ) || longMessage.contains( exceptionMessage ) )
                     {
                         exceptionMessage = longMessage;
                     }
                     else if ( !exceptionMessage.contains( longMessage ) )
                     {
                         exceptionMessage = join( exceptionMessage, '\n' + longMessage );
                     }
                 }
             }
 
             if ( StringUtils.isEmpty( exceptionMessage ) )
             {
                 exceptionMessage = t.getClass().getSimpleName();
             }
 
             if ( t instanceof UnknownHostException && !fullMessage.contains( "host" ) )
             {
                 fullMessage = join( fullMessage, "Unknown host " + exceptionMessage );
             }
             else if ( !fullMessage.contains( exceptionMessage ) )
             {
                 fullMessage = join( fullMessage, exceptionMessage );
             }
         }
 
         return fullMessage.trim();
     }
 
     private String join( String message1, String message2 )
     {
         String message = "";
 
         if ( StringUtils.isNotEmpty( message1 ) )
         {
             message = message1.trim();
         }
 
         if ( StringUtils.isNotEmpty( message2 ) )
         {
             if ( StringUtils.isNotEmpty( message ) )
             {
                 if ( message.endsWith( "." ) || message.endsWith( "!" ) || message.endsWith( ":" ) )
                 {
                     message += " ";
                 }
                 else
                 {
                     message += ": ";
                 }
             }
 
             message += message2;
         }
 
         return message;
     }
 
 }