/**
    * Portions of this software was developed by employees of the National Institute
    * of Standards and Technology (NIST), an agency of the Federal Government and is
    * being made available as a public service. Pursuant to title 17 United States
    * Code Section 105, works of NIST employees are not subject to copyright
    * protection in the United States. This software may be subject to foreign
    * copyright. Permission in the United States and in foreign countries, to the
    * extent that NIST may hold copyright, to use, copy, modify, create derivative
    * works, and distribute this software and its documentation without fee is hereby
   * granted on a non-exclusive basis, provided that this notice and disclaimer
   * of warranty appears in all copies.
   *
   * THE SOFTWARE IS PROVIDED 'AS IS' WITHOUT ANY WARRANTY OF ANY KIND, EITHER
   * EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING, BUT NOT LIMITED TO, ANY WARRANTY
   * THAT THE SOFTWARE WILL CONFORM TO SPECIFICATIONS, ANY IMPLIED WARRANTIES OF
   * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, AND FREEDOM FROM
   * INFRINGEMENT, AND ANY WARRANTY THAT THE DOCUMENTATION WILL CONFORM TO THE
   * SOFTWARE, OR ANY WARRANTY THAT THE SOFTWARE WILL BE ERROR FREE.  IN NO EVENT
   * SHALL NIST BE LIABLE FOR ANY DAMAGES, INCLUDING, BUT NOT LIMITED TO, DIRECT,
   * INDIRECT, SPECIAL OR CONSEQUENTIAL DAMAGES, ARISING OUT OF, RESULTING FROM,
   * OR IN ANY WAY CONNECTED WITH THIS SOFTWARE, WHETHER OR NOT BASED UPON WARRANTY,
   * CONTRACT, TORT, OR OTHERWISE, WHETHER OR NOT INJURY WAS SUSTAINED BY PERSONS OR
   * PROPERTY OR OTHERWISE, AND WHETHER OR NOT LOSS WAS SUSTAINED FROM, OR AROSE OUT
   * OF THE RESULTS OF, OR USE OF, THE SOFTWARE OR SERVICES PROVIDED HEREUNDER.
   */
  
  package gov.nist.secauto.decima.core.assessment;
  
  import gov.nist.secauto.decima.core.assessment.result.AssessmentResultBuilder;
  import gov.nist.secauto.decima.core.document.Document;
  
  import org.apache.logging.log4j.LogManager;
  import org.apache.logging.log4j.Logger;
  
  import java.util.HashSet;
  import java.util.List;
  import java.util.Objects;
  import java.util.Set;
  import java.util.concurrent.Callable;
  import java.util.concurrent.CompletionService;
  import java.util.concurrent.ExecutionException;
  import java.util.concurrent.Executor;
  import java.util.concurrent.ExecutorCompletionService;
  import java.util.concurrent.Future;
  
  public class ConcurrentAssessmentExecutor<DOC extends Document>
      extends AbstractAssessmentExecutor<DOC> {
    private static final Logger log = LogManager.getLogger(ConcurrentAssessmentExecutor.class);
    private final Executor executor;
  
    /**
     * Constructs a new AssessmentExecutor that is capable of executing multiple assessments
     * Concurrently, using the provided Executor to execute the provided assessments.
     * 
     * @param executor
     *          the executor to use to execute the assessment tasks
     * @param assessments
     *          the assessments to perform
     */
    public ConcurrentAssessmentExecutor(Executor executor, List<? extends Assessment<DOC>> assessments) {
      super(assessments);
      Objects.requireNonNull(executor, "executor");
      this.executor = executor;
    }
  
    public Executor getExecutor() {
      return executor;
    }
  
    @Override
    protected final void executeInternal(DOC targetDocument, AssessmentResultBuilder builder) throws AssessmentException {
      CompletionService<Void> completionService = new ExecutorCompletionService<>(executor);
      Set<Future<Void>> futures = new HashSet<>();
      for (Assessment<DOC> assessment : getExecutableAssessments(targetDocument)) {
        log.info("Submitting assessment for execution: " + assessment.getName(true));
        futures.add(completionService.submit(new AssessmentTask(assessment, targetDocument, builder)));
      }
  
      try {
        while (!futures.isEmpty()) {
          Future<Void> future = completionService.take();
          futures.remove(future);
          future.get();
        }
      } catch (InterruptedException e) {
        throw new AssessmentException("the assessment execution was interrupted", e);
      } catch (ExecutionException e) {
        if (e.getCause() instanceof AssessmentException) {
          throw (AssessmentException) e.getCause();
        }
      } finally {
        for (Future<Void> future : futures) {
          future.cancel(true);
        }
      }
    }
  
    private class AssessmentTask implements Callable<Void> {
      private final Assessment<DOC> assessment;
     private final DOC documentToAssess;
     private final AssessmentResultBuilder builder;
 
     public AssessmentTask(Assessment<DOC> assessment, DOC documentToAssess, AssessmentResultBuilder builder) {
       Objects.requireNonNull(assessment, "assessment");
       Objects.requireNonNull(documentToAssess, "documentToAssess");
       Objects.requireNonNull(builder, "builder");
       this.assessment = assessment;
       this.documentToAssess = documentToAssess;
       this.builder = builder;
     }
 
     @Override
     public Void call() throws AssessmentException {
       AssessmentExecutionHelper.executeAssessment(assessment, documentToAssess, builder);
       return null;
     }
 
   }
 
 }