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
   *
   *      https://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.tools.ant.types.resources;
  
  import java.io.File;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Stack;
  import java.util.stream.Collectors;
  
  import org.apache.tools.ant.BuildException;
  import org.apache.tools.ant.Project;
  import org.apache.tools.ant.types.DataType;
  import org.apache.tools.ant.types.Resource;
  import org.apache.tools.ant.types.ResourceCollection;
  
  /**
   * Base class for ResourceCollections that nest multiple ResourceCollections.
   * @since Ant 1.7
   */
  public abstract class BaseResourceCollectionContainer
          extends DataType implements AppendableResourceCollection, Cloneable {
      private List<ResourceCollection> rc = new ArrayList<>();
      private Collection<Resource> coll = null;
      private boolean cache = true;
  
      /**
       * Create a new BaseResourceCollectionContainer.
       */
      public BaseResourceCollectionContainer() {
      }
  
      /**
       * Create a new BaseResourceCollectionContainer.
       * @param project Project
       * @since Ant 1.8
       */
      public BaseResourceCollectionContainer(Project project) {
          setProject(project);
      }
  
      /**
       * Set whether to cache collections.
       * @param b boolean cache flag.
       */
      public synchronized void setCache(boolean b) {
          cache = b;
      }
  
      /**
       * Learn whether to cache collections. Default is <code>true</code>.
       * @return boolean cache flag.
       */
      public synchronized boolean isCache() {
          return cache;
      }
  
      /**
       * Clear the container.
       * @throws BuildException on error.
       */
      public synchronized void clear() throws BuildException {
          if (isReference()) {
              throw noChildrenAllowed();
          }
          rc.clear();
          FailFast.invalidate(this);
          coll = null;
          setChecked(false);
      }
  
      /**
       * Add a ResourceCollection to the container.
       * @param c the ResourceCollection to add.
       * @throws BuildException on error.
       */
      @Override
      public synchronized void add(ResourceCollection c) throws BuildException {
          if (isReference()) {
              throw noChildrenAllowed();
          }
          if (c == null) {
              return;
          }
          if (Project.getProject(c) == null) {
              Project p = getProject();
              if (p != null) {
                  p.setProjectReference(c);
              }
          }
          rc.add(c);
          FailFast.invalidate(this);
          coll = null;
          setChecked(false);
      }
  
      /**
       * Add the Collection of ResourceCollections to the container.
       * @param c the Collection whose elements to add.
       * @throws BuildException on error.
       */
      public synchronized void addAll(Collection<? extends ResourceCollection> c) throws BuildException {
          if (isReference()) {
              throw noChildrenAllowed();
          }
          try {
              c.forEach(this::add);
          } catch (ClassCastException e) {
              throw new BuildException(e);
          }
      }
  
      /**
       * Fulfill the ResourceCollection contract. The Iterator returned
       * will throw ConcurrentModificationExceptions if ResourceCollections
       * are added to this container while the Iterator is in use.
       * @return a "fail-fast" Iterator.
       */
      @Override
      public final synchronized Iterator<Resource> iterator() {
          if (isReference()) {
              return getRef().iterator();
          }
          dieOnCircularReference();
          return new FailFast(this, cacheCollection().iterator());
      }
  
      /**
       * Fulfill the ResourceCollection contract.
       * @return number of elements as int.
       */
      @Override
      public synchronized int size() {
          if (isReference()) {
              return getRef().size();
          }
          dieOnCircularReference();
          return cacheCollection().size();
      }
  
      /**
       * Fulfill the ResourceCollection contract.
       * @return whether this is a filesystem-only resource collection.
       */
      @Override
      public synchronized boolean isFilesystemOnly() {
          if (isReference()) {
              return getRef().isFilesystemOnly();
          }
          dieOnCircularReference();
          //first the easy way, if all children are filesystem-only, return true:
          if (rc.stream().allMatch(ResourceCollection::isFilesystemOnly)) {
              return true;
          }
          /* now check each Resource in case the child only
             lets through files from any children IT may have: */
          return cacheCollection().stream()
              .allMatch(r -> r.asOptional(FileProvider.class).isPresent());
      }
  
      /**
       * Overrides the version of DataType to recurse on all DataType
       * child elements that may have been added.
       * @param stk the stack of data types to use (recursively).
       * @param p   the project to use to dereference the references.
       * @throws BuildException on error.
       */
      protected synchronized void dieOnCircularReference(Stack<Object> stk, Project p)
          throws BuildException {
          if (isChecked()) {
              return;
          }
          if (isReference()) {
              super.dieOnCircularReference(stk, p);
          } else {
              for (ResourceCollection resourceCollection : rc) {
                  if (resourceCollection instanceof DataType) {
                      pushAndInvokeCircularReferenceCheck((DataType) resourceCollection, stk, p);
                  }
              }
              setChecked(true);
          }
      }
  
      /**
       * Get the nested ResourceCollections.
       * @return List.
       */
      public final synchronized List<ResourceCollection> getResourceCollections() {
          dieOnCircularReference();
          return Collections.unmodifiableList(rc);
      }
  
      /**
       * Template method for subclasses to return a Collection object of Resources.
       * @return Collection.
       */
      protected abstract Collection<Resource> getCollection();
  
      /**
       * Implement clone.  The set of nested resource
       * collections is shallowly cloned.
       * @return a cloned instance.
       */
      @Override
      public Object clone() {
          try {
              BaseResourceCollectionContainer c
                  = (BaseResourceCollectionContainer) super.clone();
              c.rc = new ArrayList<>(rc);
              c.coll = null;
              return c;
          } catch (CloneNotSupportedException e) {
              throw new BuildException(e);
          }
      }
  
      /**
       * Format this BaseResourceCollectionContainer as a String.
       * @return a descriptive <code>String</code>.
       */
      @Override
      public synchronized String toString() {
          if (isReference()) {
              return getRef().toString();
          }
          if (cacheCollection().isEmpty()) {
              return "";
          }
          return coll.stream().map(Object::toString)
              .collect(Collectors.joining(File.pathSeparator));
      }
  
       private BaseResourceCollectionContainer getRef() {
          return getCheckedRef(BaseResourceCollectionContainer.class);
      }
  
      private synchronized Collection<Resource> cacheCollection() {
          if (coll == null || !isCache()) {
              coll = getCollection();
          }
          return coll;
      }
  
  }
  