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.comparators;
  
  import java.util.Comparator;
  import java.util.List;
  import java.util.Stack;
  import java.util.Vector;
  
  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;
  
  /**
   * Delegates to other ResourceComparators or, if none specified,
   * uses Resources' natural ordering.
   * @since Ant 1.7
   */
  public class DelegatedResourceComparator extends ResourceComparator {
  
      private List<ResourceComparator> resourceComparators = null;
  
      /**
       * Add a delegate ResourceComparator.
       * @param c the next delegate ResourceComparator.
       */
      public synchronized void add(ResourceComparator c) {
          if (isReference()) {
              throw noChildrenAllowed();
          }
          if (c == null) {
              return;
          }
          resourceComparators = (resourceComparators == null) ? new Vector<>() : resourceComparators;
          resourceComparators.add(c);
          setChecked(false);
      }
  
      /**
       * Equality method based on the vector of resources,
       * or if a reference, the referred to object.
       * @param o the object to check against.
       * @return true if there is equality.
       */
      @Override
      public synchronized boolean equals(Object o) {
          if (o == this) {
              return true;
          }
          if (isReference()) {
              return getRef().equals(o);
          }
          if (o instanceof DelegatedResourceComparator) {
              List<ResourceComparator> ov = ((DelegatedResourceComparator) o).resourceComparators;
              return resourceComparators == null ? ov == null : resourceComparators.equals(ov);
          }
          return false;
      }
  
      /**
       * Hashcode based on the rules for equality.
       * @return a hashcode.
       */
      @Override
      public synchronized int hashCode() {
          if (isReference()) {
              return getRef().hashCode();
          }
          return resourceComparators == null ? 0 : resourceComparators.hashCode();
      }
  
      /** {@inheritDoc} */
      @Override
      protected synchronized int resourceCompare(Resource foo, Resource bar) {
          return composite(resourceComparators).compare(foo, bar);
      }
  
      /**
       * Overrides the version from DataType to recurse on nested ResourceSelector
  s.
       * @param stk the Stack of references.
       * @param p   the Project to resolve against.
       * @throws BuildException on error.
       */
      @Override
      protected void dieOnCircularReference(Stack<Object> stk, Project p)
          throws BuildException {
          if (isChecked()) {
              return;
          }
          if (isReference()) {
              super.dieOnCircularReference(stk, p);
          } else {
              if (resourceComparators != null && !resourceComparators.isEmpty()) {
                  for (ResourceComparator resourceComparator : resourceComparators) {
                      if (resourceComparator instanceof DataType) {
                          pushAndInvokeCircularReferenceCheck(resourceComparator, stk, p);
                      }
                  }
              }
              setChecked(true);
          }
      }
  
      private DelegatedResourceComparator getRef() {
          return getCheckedRef(DelegatedResourceComparator.class);
      }
  
      private static Comparator<Resource> composite(List<? extends Comparator<Resource>> foo) {
          Comparator<Resource> result = null;
          if (foo != null) {
              for (Comparator<Resource> comparator : foo) {
                  if (result == null) {
                      result = comparator;
                      continue;
                  }
                  result = result.thenComparing(comparator);
              }
          }
          return result == null ? Comparator.naturalOrder() : result;
      }
  }
  