/*
    * 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.oscal.lib.profile.resolver;
  
  import gov.nist.secauto.metaschema.model.common.util.CollectionUtil;
  
  import java.util.Collections;
  import java.util.LinkedHashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.Objects;
  import java.util.function.Function;
  import java.util.stream.Collectors;
  import java.util.stream.Stream;
  
  import edu.umd.cs.findbugs.annotations.NonNull;
  import edu.umd.cs.findbugs.annotations.Nullable;
  
  public final class ModifyPhaseUtils {
    private ModifyPhaseUtils() {
      // disable construction
    }
  
    public static <T> Function<? super T, String> identityKey() {
      return (item) -> Integer.toString(Objects.hashCode(item));
    }
  
    public static <T, R> Function<? super T, String> identifierKey(@NonNull Function<T, R> identifierFunction) {
      return (item) -> {
        R identifier = identifierFunction.apply(item);
        String retval;
        if (identifier == null) {
          retval = Integer.toString(Objects.hashCode(item));
        } else {
          retval = identifier.toString();
        }
        return retval;
      };
    }
  
    @SuppressWarnings("PMD.OnlyOneReturn") // readability
    public static <T> T mergeItem(@Nullable T original, @Nullable T additional) {
      if (additional == null) {
        return original;
      }
  
      return additional;
    }
  
    @SuppressWarnings("PMD.OnlyOneReturn") // readability
    public static <T> List<T> merge(@Nullable List<T> original, @Nullable List<T> additional,
        Function<? super T, String> keyFunction) {
      if (additional == null || additional.isEmpty()) {
        return original;
      }
  
      if (original == null || original.isEmpty()) {
        return additional;
      }
  
      // reverse the stream
      List<T> reversed = Stream.concat(
          CollectionUtil.listOrEmpty(original).stream(),
          CollectionUtil.listOrEmpty(additional).stream())
          .collect(Collectors.collectingAndThen(
              Collectors.toList(),
              l -> {
                Collections.reverse(l);
                return l;
              }));
  
      // build a map of each unique identity
      Map<String, List<T>> identityMap = reversed.stream()
          .collect(Collectors.groupingBy(keyFunction, LinkedHashMap::new, Collectors.toList()));
  
     // build a reversed list of items, using the first item
     return identityMap.values().stream()
         .map(list -> list.stream().findFirst().get())
         .collect(Collectors.collectingAndThen(
             Collectors.toList(),
             l -> {
               Collections.reverse(l);
               return l;
             }));
   }
 }