/*
 * 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.
 */
/*
 * $Id: DescendantIterator.java 469314 2006-10-30 23:31:59Z minchau $
 */
package org.apache.xpath.axes;

import org.apache.xml.dtm.Axis;
import org.apache.xml.dtm.DTM;
import org.apache.xml.dtm.DTMAxisTraverser;
import org.apache.xml.dtm.DTMFilter;
import org.apache.xml.dtm.DTMIterator;
import org.apache.xpath.Expression;
import org.apache.xpath.XPathContext;
import org.apache.xpath.compiler.Compiler;
import org.apache.xpath.compiler.OpCodes;
import org.apache.xpath.compiler.OpMap;
import org.apache.xpath.patterns.NodeTest;

This class implements an optimized iterator for
descendant, descendant-or-self, or "//foo" patterns.
See Also:
LocPathIterator
@xsl.usage
advanced/**
 * This class implements an optimized iterator for
 * descendant, descendant-or-self, or "//foo" patterns.
 * @see org.apache.xpath.axes.LocPathIterator
 * @xsl.usage advanced
 */
public class DescendantIterator extends LocPathIterator
{
    static final long serialVersionUID = -1190338607743976938L;
  
Create a DescendantIterator object.
Params:
compiler – A reference to the Compiler that contains the op map.
opPos – The position within the op map, which contains the
location path expression for this itterator.
Throws:
TransformerException – /**
   * Create a DescendantIterator object.
   *
   * @param compiler A reference to the Compiler that contains the op map.
   * @param opPos The position within the op map, which contains the
   * location path expression for this itterator.
   *
   * @throws javax.xml.transform.TransformerException
   */
  DescendantIterator(Compiler compiler, int opPos, int analysis)
          throws javax.xml.transform.TransformerException
  {

    super(compiler, opPos, analysis, false);

    int firstStepPos = OpMap.getFirstChildPos(opPos);
    int stepType = compiler.getOp(firstStepPos);

    boolean orSelf = (OpCodes.FROM_DESCENDANTS_OR_SELF == stepType);
    boolean fromRoot = false;
    if (OpCodes.FROM_SELF == stepType)
    {
      orSelf = true;
      // firstStepPos += 8;
    }
    else if(OpCodes.FROM_ROOT == stepType)
    {
      fromRoot = true;
      // Ugly code... will go away when AST work is done.
      int nextStepPos = compiler.getNextStepPos(firstStepPos);
      if(compiler.getOp(nextStepPos) == OpCodes.FROM_DESCENDANTS_OR_SELF)
        orSelf = true;
      // firstStepPos += 8;
    }
    
    // Find the position of the last step.
    int nextStepPos = firstStepPos;
    while(true)
    {
      nextStepPos = compiler.getNextStepPos(nextStepPos);
      if(nextStepPos > 0)
      {
        int stepOp = compiler.getOp(nextStepPos);
        if(OpCodes.ENDOP != stepOp)
          firstStepPos = nextStepPos;
        else
          break;
      }
      else
        break;
      
    }
    
    // Fix for http://nagoya.apache.org/bugzilla/show_bug.cgi?id=1336
    if((analysis & WalkerFactory.BIT_CHILD) != 0)
      orSelf = false;
      
    if(fromRoot)
    {
      if(orSelf)
        m_axis = Axis.DESCENDANTSORSELFFROMROOT;
      else
        m_axis = Axis.DESCENDANTSFROMROOT;
    }
    else if(orSelf)
      m_axis = Axis.DESCENDANTORSELF;
    else
      m_axis = Axis.DESCENDANT;

    int whatToShow = compiler.getWhatToShow(firstStepPos);

    if ((0 == (whatToShow
               & (DTMFilter.SHOW_ATTRIBUTE | DTMFilter.SHOW_ELEMENT
                  | DTMFilter.SHOW_PROCESSING_INSTRUCTION))) || 
                   (whatToShow == DTMFilter.SHOW_ALL))
      initNodeTest(whatToShow);
    else
    {
      initNodeTest(whatToShow, compiler.getStepNS(firstStepPos),
                              compiler.getStepLocalName(firstStepPos));
    }
    initPredicateInfo(compiler, firstStepPos);
  }
  
  
Create a DescendantIterator object.
/**
   * Create a DescendantIterator object.
   *
   */
  public DescendantIterator()
  {
    super(null);
    m_axis = Axis.DESCENDANTSORSELFFROMROOT;
    int whatToShow = DTMFilter.SHOW_ALL;
    initNodeTest(whatToShow);
  }

  
  
 Get a cloned Iterator that is reset to the beginning
 of the query.
 @return A cloned NodeIterator set of the start of the query.
 @throws CloneNotSupportedException
/**
   *  Get a cloned Iterator that is reset to the beginning
   *  of the query.
   * 
   *  @return A cloned NodeIterator set of the start of the query.
   * 
   *  @throws CloneNotSupportedException
   */
  public DTMIterator cloneWithReset() throws CloneNotSupportedException
  {

    DescendantIterator clone = (DescendantIterator) super.cloneWithReset();
    clone.m_traverser = m_traverser;

    clone.resetProximityPositions();

    return clone;
  }

  
 Returns the next node in the set and advances the position of the
iterator in the set. After a NodeIterator is created, the first call
to nextNode() returns the first node in the set.
Throws:
DOMException – 
   INVALID_STATE_ERR: Raised if this method is called after the
  detach method was invoked.
Returns:
 The next Node in the set being iterated over, or
  null if there are no more members in that set./**
   *  Returns the next node in the set and advances the position of the
   * iterator in the set. After a NodeIterator is created, the first call
   * to nextNode() returns the first node in the set.
   *
   * @return  The next <code>Node</code> in the set being iterated over, or
   *   <code>null</code> if there are no more members in that set.
   *
   * @throws DOMException
   *    INVALID_STATE_ERR: Raised if this method is called after the
   *   <code>detach</code> method was invoked.
   */
  public int nextNode()
  {
   	if(m_foundLast)
  		return DTM.NULL;

    if(DTM.NULL == m_lastFetched)
    {
      resetProximityPositions();
    }

    int next;
    
    org.apache.xpath.VariableStack vars;
    int savedStart;
    if (-1 != m_stackFrame)
    {
      vars = m_execContext.getVarStack();

      // These three statements need to be combined into one operation.
      savedStart = vars.getStackFrame();

      vars.setStackFrame(m_stackFrame);
    }
    else
    {
      // Yuck.  Just to shut up the compiler!
      vars = null;
      savedStart = 0;
    }
    
    try
    {
      do
      {
        if(0 == m_extendedTypeID)
        {
          next = m_lastFetched = (DTM.NULL == m_lastFetched)
                       ? m_traverser.first(m_context)
                       : m_traverser.next(m_context, m_lastFetched);
        }
        else
        {
          next = m_lastFetched = (DTM.NULL == m_lastFetched)
                       ? m_traverser.first(m_context, m_extendedTypeID)
                       : m_traverser.next(m_context, m_lastFetched, 
                                          m_extendedTypeID);
        }
  
        if (DTM.NULL != next)
        {
          if(DTMIterator.FILTER_ACCEPT == acceptNode(next))
            break;
          else
            continue;
        }
        else
          break;
      }
      while (next != DTM.NULL);
  
      if (DTM.NULL != next)
      {
      	m_pos++;
        return next;
      }
      else
      {
        m_foundLast = true;
  
        return DTM.NULL;
      }
    }
    finally
    {
      if (-1 != m_stackFrame)
      {
        // These two statements need to be combined into one operation.
        vars.setStackFrame(savedStart);
      }
    }
  }
  
  
Initialize the context values for this expression
after it is cloned.
Params:
context – The XPath runtime context for this
transformation./**
   * Initialize the context values for this expression
   * after it is cloned.
   *
   * @param context The XPath runtime context for this
   * transformation.
   */
  public void setRoot(int context, Object environment)
  {
    super.setRoot(context, environment);
    m_traverser = m_cdtm.getAxisTraverser(m_axis);
    
    String localName = getLocalName();
    String namespace = getNamespace();
    int what = m_whatToShow;
    // System.out.println("what: ");
    // NodeTest.debugWhatToShow(what);
    if(DTMFilter.SHOW_ALL == what
       || NodeTest.WILD.equals(localName)
       || NodeTest.WILD.equals(namespace))
    {
      m_extendedTypeID = 0;
    }
    else
    {
      int type = getNodeTypeTest(what);
      m_extendedTypeID = m_cdtm.getExpandedTypeID(namespace, localName, type);
    }
    
  }
  
  
Return the first node out of the nodeset, if this expression is 
a nodeset expression.  This is the default implementation for 
nodesets.
WARNING: Do not mutate this class from this function!
Params:
xctxt – The XPath runtime context.
Returns:
the first node out of the nodeset, or DTM.NULL./**
   * Return the first node out of the nodeset, if this expression is 
   * a nodeset expression.  This is the default implementation for 
   * nodesets.
   * <p>WARNING: Do not mutate this class from this function!</p>
   * @param xctxt The XPath runtime context.
   * @return the first node out of the nodeset, or DTM.NULL.
   */
  public int asNode(XPathContext xctxt)
    throws javax.xml.transform.TransformerException
  {
    if(getPredicateCount() > 0)
      return super.asNode(xctxt);

    int current = xctxt.getCurrentNode();
    
    DTM dtm = xctxt.getDTM(current);
    DTMAxisTraverser traverser = dtm.getAxisTraverser(m_axis);
    
    String localName = getLocalName();
    String namespace = getNamespace();
    int what = m_whatToShow;
    
    // System.out.print(" (DescendantIterator) ");
    
    // System.out.println("what: ");
    // NodeTest.debugWhatToShow(what);
    if(DTMFilter.SHOW_ALL == what
       || localName == NodeTest.WILD
       || namespace == NodeTest.WILD)
    {
      return traverser.first(current);
    }
    else
    {
      int type = getNodeTypeTest(what);
      int extendedType = dtm.getExpandedTypeID(namespace, localName, type);
      return traverser.first(current, extendedType);
    }
  }
  
  
 Detaches the iterator from the set which it iterated over, releasing
any computational resources and placing the iterator in the INVALID
state. Afterdetach has been invoked, calls to
nextNode orpreviousNode will raise the
exception INVALID_STATE_ERR.
/**
   *  Detaches the iterator from the set which it iterated over, releasing
   * any computational resources and placing the iterator in the INVALID
   * state. After<code>detach</code> has been invoked, calls to
   * <code>nextNode</code> or<code>previousNode</code> will raise the
   * exception INVALID_STATE_ERR.
   */
  public void detach()
  {
    if (m_allowDetach) {
      m_traverser = null;    
      m_extendedTypeID = 0;

      // Always call the superclass detach last!
      super.detach();
    }
  }
  
  
Returns the axis being iterated, if it is known.
Returns:
Axis.CHILD, etc., or -1 if the axis is not known or is of multiple 
types./**
   * Returns the axis being iterated, if it is known.
   * 
   * @return Axis.CHILD, etc., or -1 if the axis is not known or is of multiple 
   * types.
   */
  public int getAxis()
  {
    return m_axis;
  }
  
  
  
The traverser to use to navigate over the descendants. /** The traverser to use to navigate over the descendants. */
  transient protected DTMAxisTraverser m_traverser;
  
  
The axis that we are traversing. /** The axis that we are traversing. */
  protected int m_axis;
  
  
The extended type ID, not set until setRoot. /** The extended type ID, not set until setRoot. */
  protected int m_extendedTypeID;
  
  
See Also:
deepEquals.deepEquals(Expression)/**
   * @see Expression#deepEquals(Expression)
   */
  public boolean deepEquals(Expression expr)
  {
  	if(!super.deepEquals(expr))
  		return false;
  		
  	if(m_axis != ((DescendantIterator)expr).m_axis)
  		return false;
  		
  	return true;
  }

  
}