/*
    * 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.metaschema.core.util;
  
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.LinkedList;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  import java.util.Spliterator;
  import java.util.Spliterators;
  import java.util.stream.Collectors;
  import java.util.stream.IntStream;
  import java.util.stream.Stream;
  import java.util.stream.StreamSupport;
  
  import edu.umd.cs.findbugs.annotations.NonNull;
  import edu.umd.cs.findbugs.annotations.Nullable;
  
  public final class CollectionUtil {
  
    private CollectionUtil() {
      // disable construction
    }
  
    /**
     * Get a {@link Stream} for the provided {@link Iterable}.
     *
     * @param <T>
     *          the type to iterate on
     * @param iterator
     *          the iterator
     * @return the stream
     */
    public static <T> Stream<T> toStream(@NonNull Iterator<T> iterator) {
      Iterable<T> iterable = toIterable(iterator);
      return StreamSupport.stream(iterable.spliterator(), false);
    }
  
    /**
     * Get an {@link Iterable} for the provided {@link Stream}.
     *
     * @param <T>
     *          the type to iterate on
     * @param stream
     *          the stream to iterate over
     * @return the resulting iterable instance
     */
    @NonNull
    public static <T> Iterable<T> toIterable(@NonNull Stream<T> stream) {
      return toIterable(ObjectUtils.notNull(stream.iterator()));
    }
  
    /**
     * Get an {@link Iterable} for the provided {@link Iterator}.
     *
     * @param <T>
     *          the type to iterate on
     * @param iterator
     *          the iterator
     * @return the resulting iterable instance
     */
    @NonNull
    public static <T> Iterable<T> toIterable(@NonNull Iterator<T> iterator) {
      return () -> iterator;
    }
  
    /**
     * Get a reverse {@link Iterable} for the provided {@link List}.
     *
     * @param <T>
    *          the type to iterate on
    * @param list
    *          the list of items to iterate over
    * @return the resulting iterable instance
    */
   @NonNull
   public static <T> Iterable<T> toDescendingIterable(@NonNull List<T> list) {
     return toIterable(descendingIterator(list));
   }
 
   /**
    * Convert the provided {@link Iterable} to a list of the same generic type.
    *
    * @param <T>
    *          the collection item's generic type
    * @param iterable
    *          the Iterable to convert to a list
    * @return the list
    */
   @NonNull
   public static <T> List<T> toList(Iterable<T> iterable) {
     return ObjectUtils.notNull(StreamSupport.stream(iterable.spliterator(), false).collect(Collectors.toList()));
   }
 
   /**
    * Convert the provided {@link Iterator} to a list of the same generic type.
    *
    * @param <T>
    *          the collection item's generic type
    * @param iterator
    *          the Iterator to convert to a list
    * @return the list
    */
   @NonNull
   public static <T> List<T> toList(Iterator<T> iterator) {
     return ObjectUtils.notNull(
         StreamSupport.stream(Spliterators.spliteratorUnknownSize(iterator, Spliterator.ORDERED), false)
             .collect(Collectors.toList()));
   }
 
   /**
    * Get a reverse {@link Iterator} for the provided {@link List}.
    *
    * @param <T>
    *          the type to iterate on
    * @param list
    *          the list of items to iterate over
    * @return the resulting Iterator instance
    */
   @NonNull
   public static <T> Iterator<T> descendingIterator(@NonNull List<T> list) {
     Iterator<T> retval;
     if (list instanceof LinkedList) {
       retval = ((LinkedList<T>) list).descendingIterator();
     } else if (list instanceof ArrayList) {
       retval = IntStream.range(0, list.size())
           .map(i -> list.size() - 1 - i)
           .mapToObj(list::get).iterator();
     } else {
       throw new UnsupportedOperationException();
     }
     return ObjectUtils.notNull(retval);
   }
 
   @NonNull
   public static <T extends Collection<A>, A> T requireNonEmpty(@NonNull T collection) {
     if (collection.isEmpty()) {
       throw new IllegalStateException();
     }
     return collection;
   }
 
   @NonNull
   public static <T extends Collection<A>, A> T requireNonEmpty(@NonNull T collection, @NonNull String message) {
     if (collection.isEmpty()) {
       throw new IllegalStateException(message);
     }
     return collection;
   }
 
   /**
    * A wrapper of the {@link Collections#unmodifiableCollection(Collection)}
    * method that ensure a {@link NonNull} result is returned.
    *
    * @param <T>
    *          the collection's item type
    * @param collection
    *          the collection
    * @return a non-null unmodifiable instance of the provided collection
    */
   @SuppressWarnings("null")
   @NonNull
   public static <T> Collection<T> unmodifiableCollection(@NonNull Collection<T> collection) {
     return Collections.unmodifiableCollection(collection);
   }
 
   @SuppressWarnings("null")
   @NonNull
   public static <T> Set<T> singleton(@NonNull T value) {
     return Collections.singleton(value);
   }
 
   @SuppressWarnings("null")
   @NonNull
   public static <T> Set<T> emptySet() {
     return Collections.emptySet();
   }
 
   @SuppressWarnings("null")
   @NonNull
   public static <T> Set<T> unmodifiableSet(@NonNull Set<T> set) {
     return Collections.unmodifiableSet(set);
   }
 
   @NonNull
   public static <T> List<T> listOrEmpty(@Nullable List<T> list) {
     return list == null ? emptyList() : list;
   }
 
   @SafeVarargs
   @SuppressWarnings("null")
   @NonNull
   public static <T> List<T> listOrEmpty(@Nullable T... array) {
     return array == null || array.length == 0 ? emptyList() : Arrays.asList(array);
   }
 
   @SuppressWarnings("null")
   @NonNull
   public static <T> List<T> emptyList() {
     return Collections.emptyList();
   }
 
   @SuppressWarnings("null")
   @NonNull
   public static <T> List<T> unmodifiableList(@NonNull List<T> list) {
     return Collections.unmodifiableList(list);
   }
 
   @SuppressWarnings("null")
   @NonNull
   public static <T> List<T> singletonList(@NonNull T instance) {
     return Collections.singletonList(instance);
   }
 
   @SuppressWarnings("null")
   @NonNull
   public static <K, V> Map<K, V> emptyMap() {
     return Collections.emptyMap();
   }
 
   @SuppressWarnings("null")
   @NonNull
   public static <K, V> Map<K, V> singletonMap(@NonNull K key, @NonNull V value) {
     return Collections.singletonMap(key, value);
   }
 
   @SuppressWarnings("null")
   @NonNull
   public static <K, V> Map<K, V> unmodifiableMap(@NonNull Map<K, V> map) {
     return Collections.unmodifiableMap(map);
   }
 }