/*
    * 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.commons.jxpath.ri.model.beans;
  
  import java.util.ArrayList;
  import java.util.List;
  
  import org.apache.commons.jxpath.JXPathException;
  import org.apache.commons.jxpath.ri.model.NodeIterator;
  import org.apache.commons.jxpath.ri.model.NodePointer;
  
  /**
   * Combines node iterators of all elements of a collection into one aggregate node iterator.
   */
  public abstract class CollectionNodeIterator implements NodeIterator {
  
      private final CollectionPointer pointer;
      private final boolean reverse;
      private final NodePointer startWith;
      private int position;
      private List<NodePointer> collection;
  
      /**
       * Constructs a new CollectionNodeIterator.
       *
       * @param pointer   collection pointer
       * @param reverse   iteration order
       * @param startWith starting pointer
       */
      protected CollectionNodeIterator(final CollectionPointer pointer, final boolean reverse, final NodePointer startWith) {
          this.pointer = pointer;
          this.reverse = reverse;
          this.startWith = startWith;
      }
  
      /**
       * Implemented by subclasses to produce child/attribute node iterators.
       *
       * @param elementPointer owning pointer
       * @return NodeIterator
       */
      protected abstract NodeIterator getElementNodeIterator(NodePointer elementPointer);
  
      @Override
      public NodePointer getNodePointer() {
          if (position == 0) {
              return null;
          }
          return collection.get(position - 1);
      }
  
      @Override
      public int getPosition() {
          return position;
      }
  
      /**
       * Prepare...
       */
      private void prepare() {
          collection = new ArrayList<>();
          final NodePointer ptr = (NodePointer) pointer.clone();
          final int length = ptr.getLength();
          for (int i = 0; i < length; i++) {
              ptr.setIndex(i);
              final NodePointer elementPointer = ptr.getValuePointer();
              final NodeIterator iter = getElementNodeIterator(elementPointer);
              for (int j = 1; iter.setPosition(j); j++) {
                  final NodePointer childPointer = iter.getNodePointer();
                  if (reverse) {
                      collection.add(0, childPointer);
                  } else {
                      collection.add(childPointer);
                  }
              }
          }
          if (startWith != null) {
              final int index = collection.indexOf(startWith);
              if (index == -1) {
                  throw new JXPathException("Invalid starting pointer for iterator: " + startWith);
              }
              while (collection.size() > index) {
                  if (!reverse) {
                      collection.remove(collection.size() - 1);
                 } else {
                     collection.remove(0);
                 }
             }
         }
     }
 
     @Override
     public boolean setPosition(final int position) {
         if (collection == null) {
             prepare();
         }
         if (position < 1 || position > collection.size()) {
             return false;
         }
         this.position = position;
         return true;
     }
 }