/*
    * 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.
   *
   * @author Dmitri Plotnikov
   * @version $Revision: 670727 $ $Date: 2008-06-23 22:10:38 +0200 (Mo, 23 Jun 2008) $
   */
  public class DescendantContext extends EvalContext {
      private NodeTest nodeTest;
      private boolean setStarted = false;
      private Stack stack = null;
      private NodePointer currentNodePointer = null;
      private boolean includeSelf;
      private static final NodeTest ELEMENT_NODE_TEST =
              new NodeTypeTest(Compiler.NODE_TYPE_NODE);
  
      /**
       * Create a new DescendantContext.
       * @param parentContext parent context
       * @param includeSelf whether to include this node
       * @param nodeTest test
       */
      public DescendantContext(EvalContext parentContext, boolean includeSelf,
              NodeTest nodeTest) {
          super(parentContext);
          this.includeSelf = includeSelf;
          this.nodeTest = nodeTest;
      }
  
      public boolean isChildOrderingRequired() {
          return true;
      }
  
      public NodePointer getCurrentNodePointer() {
          if (position == 0 && !setPosition(1)) {
              return null;
          }
          return currentNodePointer;
      }
  
      public void reset() {
          super.reset();
          setStarted = false;
      }
  
      public boolean setPosition(int position) {
          if (position < this.position) {
              reset();
          }
  
          while (this.position < position) {
              if (!nextNode()) {
                  return false;
              }
          }
          return true;
      }
  
      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()) {
             NodeIterator it = (NodeIterator) 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;
     }
 
     /**
      * 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() {
         Object node = currentNodePointer.getNode();
         for (int i = stack.size() - 1; --i >= 0;) {
             NodeIterator it = (NodeIterator) stack.get(i);
             Pointer pointer = it.getNodePointer();
             if (pointer != null && pointer.getNode() == node) {
                 return true;
             }
         }
         return false;
     }
 }