package org.apache.maven.plugins.invoker;
   
   /*
    * 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.LinkedHashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.concurrent.Callable;
  import java.util.concurrent.ExecutorService;
  import java.util.concurrent.Executors;
  import java.util.stream.Collectors;
  
  import org.apache.maven.plugins.invoker.model.BuildJob;
  
  /**
   * Execute build jobs with parallel.
   *
   * @author Slawomir Jaranowski
   */
  class JobExecutor
  {
      interface ThrowableJobConsumer
      {
          void accept( BuildJob t ) throws Throwable;
      }
  
      private final List<BuildJob> jobs;
      private final int threadsCount;
  
      JobExecutor( List<BuildJob> jobs, int threadsCount )
      {
          this.jobs = jobs;
          this.threadsCount = threadsCount;
      }
  
      public void forEach( ThrowableJobConsumer jobConsumer )
      {
          // group and sort jobs by ordinal
          Map<Integer, List<BuildJob>> groupedJobs = jobs.stream()
              .sorted( ( j1, j2 ) -> Integer.compare( j2.getOrdinal(), j1.getOrdinal() ) )
              .collect( Collectors.groupingBy( BuildJob::getOrdinal, LinkedHashMap::new, Collectors.toList() ) );
  
          ExecutorService executorService = Executors.newFixedThreadPool( threadsCount );
  
          groupedJobs.forEach( ( key, value ) ->
          {
              // prepare list of callable tasks
              List<Callable<Void>> callableJobs = value.stream().map( buildJob -> (Callable<Void>) () ->
              {
                  try
                  {
                      jobConsumer.accept( buildJob );
                  }
                  catch ( Throwable e )
                  {
                      buildJob.setResult( BuildJob.Result.ERROR );
                      buildJob.setFailureMessage( String.valueOf( e ) );
                  }
                  return null;
              } ).collect( Collectors.toList() );
  
              try
              {
                  executorService.invokeAll( callableJobs );
              }
              catch ( InterruptedException e )
              {
                  Thread.currentThread().interrupt();
                  throw new RuntimeException( e );
              }
          } );
  
          // all task are finished here
          executorService.shutdownNow();
      }
  }