/*
 * 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: FilterExprIteratorSimple.java 468655 2006-10-28 07:12:06Z minchau $
 */
package org.apache.xpath.axes;

import org.apache.xml.dtm.Axis;
import org.apache.xml.dtm.DTM;
import org.apache.xml.utils.PrefixResolver;
import org.apache.xpath.Expression;
import org.apache.xpath.ExpressionOwner;
import org.apache.xpath.VariableStack;
import org.apache.xpath.XPathContext;
import org.apache.xpath.XPathVisitor;
import org.apache.xpath.objects.XNodeSet;

Class to use for one-step iteration that doesn't have a predicate, and 
doesn't need to set the context.
/**
 * Class to use for one-step iteration that doesn't have a predicate, and 
 * doesn't need to set the context.
 */
public class FilterExprIteratorSimple extends LocPathIterator
{
    static final long serialVersionUID = -6978977187025375579L;
  
The contained expression. Should be non-null.
 @serial   /** The contained expression. Should be non-null.
   *  @serial   */
  private Expression m_expr;

  
The result of executing m_expr.  Needs to be deep cloned on clone op.  /** The result of executing m_expr.  Needs to be deep cloned on clone op.  */
  transient private XNodeSet m_exprObj;

  private boolean m_mustHardReset = false;
  private boolean m_canDetachNodeset = true;

  
Create a FilterExprIteratorSimple object.
/**
   * Create a FilterExprIteratorSimple object.
   *
   */
  public FilterExprIteratorSimple()
  {
    super(null);
  }
  
  
Create a FilterExprIteratorSimple object.
/**
   * Create a FilterExprIteratorSimple object.
   *
   */
  public FilterExprIteratorSimple(Expression expr)
  {
    super(null);
    m_expr = expr;
  }
  
  
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_exprObj = executeFilterExpr(context, m_execContext, getPrefixResolver(), 
  	                  getIsTopLevel(), m_stackFrame, m_expr);
  }

  
Execute the expression.  Meant for reuse by other FilterExpr iterators 
that are not derived from this object.
/**
   * Execute the expression.  Meant for reuse by other FilterExpr iterators 
   * that are not derived from this object.
   */
  public static XNodeSet executeFilterExpr(int context, XPathContext xctxt, 
  												PrefixResolver prefixResolver,
  												boolean isTopLevel,
  												int stackFrame,
  												Expression expr )
    throws org.apache.xml.utils.WrappedRuntimeException
  {
    PrefixResolver savedResolver = xctxt.getNamespaceContext();
    XNodeSet result = null;

    try
    {
      xctxt.pushCurrentNode(context);
      xctxt.setNamespaceContext(prefixResolver);

      // The setRoot operation can take place with a reset operation, 
      // and so we may not be in the context of LocPathIterator#nextNode, 
      // so we have to set up the variable context, execute the expression, 
      // and then restore the variable context.

      if (isTopLevel)
      {
        // System.out.println("calling m_expr.execute(getXPathContext())");
        VariableStack vars = xctxt.getVarStack();

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

        result = (org.apache.xpath.objects.XNodeSet) expr.execute(xctxt);
        result.setShouldCacheNodes(true);

        // These two statements need to be combined into one operation.
        vars.setStackFrame(savedStart);
      }
      else
          result = (org.apache.xpath.objects.XNodeSet) expr.execute(xctxt);

    }
    catch (javax.xml.transform.TransformerException se)
    {

      // TODO: Fix...
      throw new org.apache.xml.utils.WrappedRuntimeException(se);
    }
    finally
    {
      xctxt.popCurrentNode();
      xctxt.setNamespaceContext(savedResolver);
    }
    return result;
  }
  
  
 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.
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.
   */
  public int nextNode()
  {
  	if(m_foundLast)
  		return DTM.NULL;

    int next;

    if (null != m_exprObj)
    {
      m_lastFetched = next = m_exprObj.nextNode();
    }
    else
      m_lastFetched = next = DTM.NULL;

    // m_lastFetched = next;
    if (DTM.NULL != next)
    {
      m_pos++;
      return next;
    }
    else
    {
      m_foundLast = true;

      return DTM.NULL;
    }
  }
  
  
Detaches the walker from the set which it iterated over, releasing
any computational resources and placing the iterator in the INVALID
state.
/**
   * Detaches the walker from the set which it iterated over, releasing
   * any computational resources and placing the iterator in the INVALID
   * state.
   */
  public void detach()
  {  
    if(m_allowDetach)
    {
  		super.detach();
  		m_exprObj.detach();
  		m_exprObj = null;
    }
  }

  
This function is used to fixup variables from QNames to stack frame 
indexes at stylesheet build time.
Params:
vars – List of QNames that correspond to variables.  This list 
should be searched backwards for the first qualified name that 
corresponds to the variable reference qname.  The position of the 
QName in the vector from the start of the vector will be its position 
in the stack frame (but variables above the globalsTop value will need 
to be offset to the current stack frame)./**
   * This function is used to fixup variables from QNames to stack frame 
   * indexes at stylesheet build time.
   * @param vars List of QNames that correspond to variables.  This list 
   * should be searched backwards for the first qualified name that 
   * corresponds to the variable reference qname.  The position of the 
   * QName in the vector from the start of the vector will be its position 
   * in the stack frame (but variables above the globalsTop value will need 
   * to be offset to the current stack frame).
   */
  public void fixupVariables(java.util.Vector vars, int globalsSize)
  {
    super.fixupVariables(vars, globalsSize);
    m_expr.fixupVariables(vars, globalsSize);
  }

  
Get the inner contained expression of this filter.
/**
   * Get the inner contained expression of this filter.
   */
  public Expression getInnerExpression()
  {
    return m_expr;
  }

  
Set the inner contained expression of this filter.
/**
   * Set the inner contained expression of this filter.
   */
  public void setInnerExpression(Expression expr)
  {
    expr.exprSetParent(this);
    m_expr = expr;
  }

  
Get the analysis bits for this walker, as defined in the WalkerFactory.
Returns:
One of WalkerFactory#BIT_DESCENDANT, etc./** 
   * Get the analysis bits for this walker, as defined in the WalkerFactory.
   * @return One of WalkerFactory#BIT_DESCENDANT, etc.
   */
  public int getAnalysisBits()
  {
    if (null != m_expr && m_expr instanceof PathComponent)
    {
      return ((PathComponent) m_expr).getAnalysisBits();
    }
    return WalkerFactory.BIT_FILTER;
  }

  
Returns true if all the nodes in the iteration well be returned in document 
order.
Warning: This can only be called after setRoot has been called!
Returns:
true as a default./**
   * Returns true if all the nodes in the iteration well be returned in document 
   * order.
   * Warning: This can only be called after setRoot has been called!
   * 
   * @return true as a default.
   */
  public boolean isDocOrdered()
  {
    return m_exprObj.isDocOrdered();
  }

  class filterExprOwner implements ExpressionOwner
  {
    
See Also:
getExpression.getExpression()/**
    * @see ExpressionOwner#getExpression()
    */
    public Expression getExpression()
    {
      return m_expr;
    }

    
See Also:
setExpression.setExpression(Expression)/**
     * @see ExpressionOwner#setExpression(Expression)
     */
    public void setExpression(Expression exp)
    {
      exp.exprSetParent(FilterExprIteratorSimple.this);
      m_expr = exp;
    }

  }

  
This will traverse the heararchy, calling the visitor for 
each member.  If the called visitor method returns 
false, the subtree should not be called.
Params:
visitor – The visitor whose appropriate method will be called./**
   * This will traverse the heararchy, calling the visitor for 
   * each member.  If the called visitor method returns 
   * false, the subtree should not be called.
   * 
   * @param visitor The visitor whose appropriate method will be called.
   */
  public void callPredicateVisitors(XPathVisitor visitor)
  {
    m_expr.callVisitors(new filterExprOwner(), visitor);

    super.callPredicateVisitors(visitor);
  }

  
See Also:
deepEquals.deepEquals(Expression)/**
   * @see Expression#deepEquals(Expression)
   */
  public boolean deepEquals(Expression expr)
  {
    if (!super.deepEquals(expr))
      return false;

    FilterExprIteratorSimple fet = (FilterExprIteratorSimple) expr;
    if (!m_expr.deepEquals(fet.m_expr))
      return false;

    return true;
  }
  
  
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()
  {
  	if(null != m_exprObj)
    	return m_exprObj.getAxis();
    else
    	return Axis.FILTEREDLIST;
  }


}