/*
    * SPDX-FileCopyrightText: none
    * SPDX-License-Identifier: CC0-1.0
    */
   
   package dev.metaschema.oscal.lib.profile.resolver;
   
   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 dev.metaschema.core.util.CollectionUtil;
  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;
              }));
    }
  }