content: /*
   *  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.
   */
  package org.apache.causeway.core.metamodel.facets.collections;
  
  import java.util.AbstractList;
  import java.util.AbstractSet;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.HashSet;
  import java.util.LinkedHashSet;
  import java.util.LinkedList;
  import java.util.List;
  import java.util.Map;
  import java.util.Optional;
  import java.util.Set;
  import java.util.SortedSet;
  import java.util.TreeSet;
  import java.util.concurrent.CopyOnWriteArrayList;
  import java.util.concurrent.CopyOnWriteArraySet;
  import java.util.function.Supplier;
  import java.util.stream.Collector;
  import java.util.stream.Collectors;
  import java.util.stream.Stream;
  
  import org.jspecify.annotations.Nullable;
  
  import org.apache.causeway.commons.collections.Can;
  import org.apache.causeway.commons.internal.collections._Arrays;
  import org.apache.causeway.commons.internal.collections._Lists;
  import org.apache.causeway.commons.internal.collections._Sets;
  import org.apache.causeway.core.metamodel.facetapi.Facet;
  import org.apache.causeway.core.metamodel.facets.actcoll.typeof.TypeOfFacet;
  import org.apache.causeway.core.metamodel.object.ManagedObject;
  import org.apache.causeway.core.metamodel.object.MmUnwrapUtils;
  import org.apache.causeway.core.metamodel.object.PackedManagedObject;
  import org.apache.causeway.core.metamodel.spec.ObjectSpecification;
  
  import org.jspecify.annotations.NonNull;
  import lombok.experimental.UtilityClass;
  
  /**
   * Attached to {@link ObjectSpecification}s that represent a collection.
   *
   * @implNote Factories of (implementations of this) facet should ensure that a
   * {@link TypeOfFacet} is also attached to the same facet holder. The
   * {@link #getTypeOfFacet()} is a convenience for this.
   */
  public interface CollectionFacet extends Facet {
  
      int size(ManagedObject collectionAdapter);
  
      /**
       * @param collectionAdapter
       * @return Stream of specified {@code collectionAdapter}'s elements
       * (typically the elements of a collection or array)
       * @since 2.0
       */
      Stream<ManagedObject> stream(ManagedObject collectionAdapter);
  
      default Optional<ManagedObject> firstElement(final ManagedObject collectionAdapter) {
          return stream(collectionAdapter).findFirst();
      }
  
      /**
       * Set the contents of the collection (POJO) as provided by the optional supplier.
       * <p>
       *
       * @param emptyCollectionPojoFactory empty collection or array factory
       * @param collectionSpec
       * @param elements
       * @param elementCount
       * @return a possibly new instance
       * @since 2.0
       */
      Object populatePojo(
              Supplier<Object> emptyCollectionPojoFactory,
              ObjectSpecification collectionSpec,
              Stream<ManagedObject> elements,
              int elementCount);
  
      /**
       * Convenience method that returns the {@link TypeOfFacet} on this facet's
       * {@link #getFacetHolder() holder}.
       */
      TypeOfFacet getTypeOfFacet();
  
      // -- UTILS
  
      public static Optional<CollectionFacet> lookup(final @Nullable ManagedObject container) {
          return container!=null
              ? container.objSpec().lookupFacet(CollectionFacet.class)
              : Optional.empty();
      }
  
      public static int elementCount(final @Nullable ManagedObject container) {
          return container instanceof PackedManagedObject packedManagedObject
              ? packedManagedObject.unpack().size()
              : lookup(container)
                  .map(collectionFacet->collectionFacet.size(container))
                  .orElse(0);
      }
  
      public static Stream<ManagedObject> streamAdapters(final @Nullable ManagedObject container) {
          return container instanceof PackedManagedObject packedManagedObject
              ? packedManagedObject.unpack().stream()
              : lookup(container)
                  .map(collectionFacet->collectionFacet.stream(container))
                  .orElse(Stream.empty());
      }
  
      public static Object[] toArrayOfPojos(final @Nullable ManagedObject container) {
          var elementAdapters = streamAdapters(container)
                  .collect(Collectors.toList());
          return MmUnwrapUtils.multipleAsArray(elementAdapters);
      }
  
      @UtilityClass
      public static class AutofitUtils {
  
          /**
           * Copies the iterable into the specified type.
           */
          @SuppressWarnings({ "rawtypes", "unchecked" })
          public static Object collect(
                  final @NonNull Stream<?> stream,
                  final @NonNull Class<?> requiredType) {
  
              Stream rawStream = stream;
  
              var factoryIfAny = factoriesByType.get(requiredType);
              if(factoryIfAny!=null) {
                  Supplier rawFactory = factoryIfAny;
                  Collector rawCollector = Collectors.toCollection(rawFactory);
                  return rawStream.collect(rawCollector);
              }
  
              // Array
              if (requiredType.isArray()) {
                  Class<?> elementType = requiredType.getComponentType();
                  return rawStream.collect(_Arrays.toArray(elementType));
              }
  
              // Can
              if (Can.class.equals(requiredType)) {
                  return rawStream.collect(Can.toCan());
              }
  
              // not recognized
              return null;
  
          }
  
          // -- HELPER
  
          private static final Map<Class<?>, Supplier<Collection<?>>> factoriesByType = Map.ofEntries(
  
                      // specific list implementations
                  Map.entry(CopyOnWriteArrayList.class, _Lists::newConcurrentList),
                  Map.entry(LinkedList.class, _Lists::newLinkedList),
                  Map.entry(ArrayList.class, _Lists::newArrayList),
                  Map.entry(AbstractList.class, _Lists::newArrayList),
  
                      // specific set implementations
                  Map.entry(CopyOnWriteArraySet.class, _Sets::newCopyOnWriteArraySet),
                  Map.entry(LinkedHashSet.class, _Sets::newLinkedHashSet),
                  Map.entry(HashSet.class, _Sets::newHashSet),
                  Map.entry(TreeSet.class, _Sets::newTreeSet),
                  Map.entry(AbstractSet.class, _Sets::newLinkedHashSet),
  
                      // interfaces
                  Map.entry(List.class, _Lists::newArrayList),
                  Map.entry(SortedSet.class, _Sets::newTreeSet),
                  Map.entry(Set.class, _Sets::newLinkedHashSet),
                  Map.entry(Collection.class, _Lists::newArrayList)
                  );
  
      }
  
  }
  