/*
    * 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.axes;
  
  import java.util.Stack;
  
  import org.apache.commons.jxpath.Pointer;
  import org.apache.commons.jxpath.ri.Compiler;
  import org.apache.commons.jxpath.ri.EvalContext;
  import org.apache.commons.jxpath.ri.compiler.NodeTest;
  import org.apache.commons.jxpath.ri.compiler.NodeTypeTest;
  import org.apache.commons.jxpath.ri.model.NodeIterator;
  import org.apache.commons.jxpath.ri.model.NodePointer;
  
  /**
   * An EvalContext that walks the "descendant::" and "descendant-or-self::" axes.
   */
  public class DescendantContext extends EvalContext {
  
      private static final NodeTest ELEMENT_NODE_TEST = new NodeTypeTest(Compiler.NODE_TYPE_NODE);
      private final NodeTest nodeTest;
      private boolean setStarted;
      private Stack<NodeIterator> stack;
      private NodePointer currentNodePointer;
      private final boolean includeSelf;
  
      /**
       * Constructs a new DescendantContext.
       *
       * @param parentContext parent context
       * @param includeSelf   whether to include this node
       * @param nodeTest      test
       */
      public DescendantContext(final EvalContext parentContext, final boolean includeSelf, final NodeTest nodeTest) {
          super(parentContext);
          this.includeSelf = includeSelf;
          this.nodeTest = nodeTest;
      }
  
      @Override
      public NodePointer getCurrentNodePointer() {
          if (position == 0 && !setPosition(1)) {
              return null;
          }
          return currentNodePointer;
      }
  
      @Override
      public boolean isChildOrderingRequired() {
          return true;
      }
  
      /**
       * Checks if we are reentering a bean we have already seen and if so returns true to prevent infinite recursion.
       *
       * @return boolean
       */
      private boolean isRecursive() {
          final Object node = currentNodePointer.getNode();
          for (int i = stack.size() - 1; --i >= 0;) {
              final NodeIterator it = stack.get(i);
              final Pointer pointer = it.getNodePointer();
              if (pointer != null && pointer.getNode() == node) {
                  return true;
              }
          }
          return false;
      }
  
      @Override
      public boolean nextNode() {
          if (!setStarted) {
              setStarted = true;
              if (stack == null) {
                  stack = new Stack<>();
              } else {
                  stack.clear();
              }
              currentNodePointer = parentContext.getCurrentNodePointer();
              if (currentNodePointer != null) {
                  if (!currentNodePointer.isLeaf()) {
                      stack.push(currentNodePointer.childIterator(ELEMENT_NODE_TEST, false, null));
                  }
                  if (includeSelf && currentNodePointer.testNode(nodeTest)) {
                     position++;
                     return true;
                 }
             }
         }
         while (!stack.isEmpty()) {
             final NodeIterator it = stack.peek();
             if (it.setPosition(it.getPosition() + 1)) {
                 currentNodePointer = it.getNodePointer();
                 if (!isRecursive()) {
                     if (!currentNodePointer.isLeaf()) {
                         stack.push(currentNodePointer.childIterator(ELEMENT_NODE_TEST, false, null));
                     }
                     if (currentNodePointer.testNode(nodeTest)) {
                         position++;
                         return true;
                     }
                 }
             } else {
                 // We get here only if the name test failed
                 // and the iterator ended
                 stack.pop();
             }
         }
         return false;
     }
 
     @Override
     public void reset() {
         super.reset();
         setStarted = false;
     }
 
     @Override
     public boolean setPosition(final int position) {
         if (position < this.position) {
             reset();
         }
         while (this.position < position) {
             if (!nextNode()) {
                 return false;
             }
         }
         return true;
     }
 }