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

import org.apache.xpath.Expression;
import org.apache.xpath.ExpressionOwner;
import org.apache.xpath.XPathContext;
import org.apache.xpath.XPathVisitor;
import org.apache.xpath.objects.XObject;

The baseclass for a binary operation.
/**
 * The baseclass for a binary operation.
 */
public class Operation extends Expression implements ExpressionOwner
{
    static final long serialVersionUID = -3037139537171050430L;

  
The left operand expression.
 @serial /** The left operand expression.
   *  @serial */
  protected Expression m_left;

  
The right operand expression.
 @serial /** The right operand expression.
   *  @serial */
  protected Expression m_right;
  
  
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)
  {
    m_left.fixupVariables(vars, globalsSize);
    m_right.fixupVariables(vars, globalsSize);
  }


  
Tell if this expression or it's subexpressions can traverse outside
the current subtree.
Returns:
true if traversal outside the context node's subtree can occur./**
   * Tell if this expression or it's subexpressions can traverse outside
   * the current subtree.
   *
   * @return true if traversal outside the context node's subtree can occur.
   */
  public boolean canTraverseOutsideSubtree()
  {

    if (null != m_left && m_left.canTraverseOutsideSubtree())
      return true;

    if (null != m_right && m_right.canTraverseOutsideSubtree())
      return true;

    return false;
  }

  
Set the left and right operand expressions for this operation.
Params:
l – The left expression operand.
r – The right expression operand./**
   * Set the left and right operand expressions for this operation.
   *
   *
   * @param l The left expression operand.
   * @param r The right expression operand.
   */
  public void setLeftRight(Expression l, Expression r)
  {
    m_left = l;
    m_right = r;
    l.exprSetParent(this);
    r.exprSetParent(this);
  }

  
Execute a binary operation by calling execute on each of the operands,
and then calling the operate method on the derived class.
Params:
xctxt – The runtime execution context.
Throws:
TransformerException – 
Returns:
The XObject result of the operation./**
   * Execute a binary operation by calling execute on each of the operands,
   * and then calling the operate method on the derived class.
   *
   *
   * @param xctxt The runtime execution context.
   *
   * @return The XObject result of the operation.
   *
   * @throws javax.xml.transform.TransformerException
   */
  public XObject execute(XPathContext xctxt)
          throws javax.xml.transform.TransformerException
  {

    XObject left = m_left.execute(xctxt, true);
    XObject right = m_right.execute(xctxt, true);

    XObject result = operate(left, right);
    left.detach();
    right.detach();
    return result;
  }

  
Apply the operation to two operands, and return the result.
Params:
left – non-null reference to the evaluated left operand.
right – non-null reference to the evaluated right operand.
Throws:
TransformerException – 
Returns:
non-null reference to the XObject that represents the result of the operation./**
   * Apply the operation to two operands, and return the result.
   *
   *
   * @param left non-null reference to the evaluated left operand.
   * @param right non-null reference to the evaluated right operand.
   *
   * @return non-null reference to the XObject that represents the result of the operation.
   *
   * @throws javax.xml.transform.TransformerException
   */
  public XObject operate(XObject left, XObject right)
          throws javax.xml.transform.TransformerException
  {
    return null;  // no-op
  }

  
Returns:
the left operand of binary operation, as an Expression./** @return the left operand of binary operation, as an Expression.
   */
  public Expression getLeftOperand(){
    return m_left;
  }

  
Returns:
the right operand of binary operation, as an Expression./** @return the right operand of binary operation, as an Expression.
   */
  public Expression getRightOperand(){
    return m_right;
  }
  
  class LeftExprOwner implements ExpressionOwner
  {
    
See Also:
getExpression.getExpression()/**
     * @see ExpressionOwner#getExpression()
     */
    public Expression getExpression()
    {
      return m_left;
    }

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

  
See Also:
callVisitors.callVisitors(ExpressionOwner, XPathVisitor)/**
   * @see org.apache.xpath.XPathVisitable#callVisitors(ExpressionOwner, XPathVisitor)
   */
  public void callVisitors(ExpressionOwner owner, XPathVisitor visitor)
  {
  	if(visitor.visitBinaryOperation(owner, this))
  	{
  		m_left.callVisitors(new LeftExprOwner(), visitor);
  		m_right.callVisitors(this, visitor);
  	}
  }

  
See Also:
getExpression.getExpression()/**
   * @see ExpressionOwner#getExpression()
   */
  public Expression getExpression()
  {
    return m_right;
  }

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

  
See Also:
deepEquals.deepEquals(Expression)/**
   * @see Expression#deepEquals(Expression)
   */
  public boolean deepEquals(Expression expr)
  {
  	if(!isSameClass(expr))
  		return false;
  		
  	if(!m_left.deepEquals(((Operation)expr).m_left))
  		return false;
  		
  	if(!m_right.deepEquals(((Operation)expr).m_right))
  		return false;
  		
  	return true;
  }
}