/*
 * 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.
 */
/*
 * $Id$
 */
package org.apache.xpath.functions;

import java.util.Vector;

import org.apache.xalan.res.XSLMessages;
import org.apache.xpath.Expression;
import org.apache.xpath.ExpressionNode;
import org.apache.xpath.ExpressionOwner;
import org.apache.xpath.ExtensionsProvider;
import org.apache.xpath.XPathContext;
import org.apache.xpath.XPathVisitor;
import org.apache.xpath.objects.XNull;
import org.apache.xpath.objects.XObject;
import org.apache.xpath.res.XPATHErrorResources;
import org.apache.xpath.res.XPATHMessages;

/**
 * An object of this class represents an extension call expression.  When
 * the expression executes, it calls ExtensionsTable#extFunction, and then
 * converts the result to the appropriate XObject.
 * @xsl.usage advanced
 */
public class FuncExtFunction extends Function
{
    static final long serialVersionUID = 5196115554693708718L;

  /**
   * The namespace for the extension function, which should not normally
   *  be null or empty.
   *  @serial    
   */
  String m_namespace;

  /**
   * The local name of the extension.
   *  @serial   
   */
  String m_extensionName;

  /**
   * Unique method key, which is passed to ExtensionsTable#extFunction in
   *  order to allow caching of the method.
   *  @serial 
   */
  Object m_methodKey;

  /**
   * Array of static expressions which represent the parameters to the
   *  function.
   *  @serial   
   */
  Vector m_argVec = new Vector();

  /**
   * 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).
   * NEEDSDOC @param globalsSize
   */
  public void fixupVariables(java.util.Vector vars, int globalsSize)
  {

    if (null != m_argVec)
    {
      int nArgs = m_argVec.size();

      for (int i = 0; i < nArgs; i++)
      {
        Expression arg = (Expression) m_argVec.elementAt(i);

        arg.fixupVariables(vars, globalsSize);
      }
    }
  }
  
  /**
   * Return the namespace of the extension function.
   *
   * @return The namespace of the extension function.
   */
  public String getNamespace()
  {
    return m_namespace;
  }
  
  /**
   * Return the name of the extension function.
   *
   * @return The name of the extension function.
   */
  public String getFunctionName()
  {
    return m_extensionName;
  }
  
  /**
   * Return the method key of the extension function.
   *
   * @return The method key of the extension function.
   */
  public Object getMethodKey()
  {
    return m_methodKey;
  }

  /** 
   * Return the nth argument passed to the extension function.
   * 
   * @param n The argument number index.
   * @return The Expression object at the given index.
   */    
  public Expression getArg(int n) {
    if (n >= 0 && n < m_argVec.size())
      return (Expression) m_argVec.elementAt(n);
    else
      return null;
  }

  /**
   * Return the number of arguments that were passed
   * into this extension function.
   *
   * @return The number of arguments.
   */    
  public int getArgCount() {
    return m_argVec.size();
  }

  /**
   * Create a new FuncExtFunction based on the qualified name of the extension,
   * and a unique method key.
   *
   * @param namespace The namespace for the extension function, which should
   *                  not normally be null or empty.
   * @param extensionName The local name of the extension.
   * @param methodKey Unique method key, which is passed to
   *                  ExtensionsTable#extFunction in order to allow caching
   *                  of the method.
   */
  public FuncExtFunction(java.lang.String namespace,
                         java.lang.String extensionName, Object methodKey)
  {
    //try{throw new Exception("FuncExtFunction() " + namespace + " " + extensionName);} catch (Exception e){e.printStackTrace();}
    m_namespace = namespace;
    m_extensionName = extensionName;
    m_methodKey = methodKey;
  }

  /**
   * Execute the function.  The function must return
   * a valid object.
   * @param xctxt The current execution context.
   * @return A valid XObject.
   *
   * @throws javax.xml.transform.TransformerException
   */
  public XObject execute(XPathContext xctxt)
          throws javax.xml.transform.TransformerException
  {
    if (xctxt.isSecureProcessing())
      throw new javax.xml.transform.TransformerException(
        XPATHMessages.createXPATHMessage(
          XPATHErrorResources.ER_EXTENSION_FUNCTION_CANNOT_BE_INVOKED,
          new Object[] {toString()}));
      
    XObject result;
    Vector argVec = new Vector();
    int nArgs = m_argVec.size();

    for (int i = 0; i < nArgs; i++)
    {
      Expression arg = (Expression) m_argVec.elementAt(i);
      
      XObject xobj = arg.execute(xctxt);
      /*
       * Should cache the arguments for func:function
       */
      xobj.allowDetachToRelease(false); 
      argVec.addElement(xobj);
    }
    //dml
    ExtensionsProvider extProvider = (ExtensionsProvider)xctxt.getOwnerObject();
    Object val = extProvider.extFunction(this, argVec);

    if (null != val)
    {
      result = XObject.create(val, xctxt);
    }
    else
    {
      result = new XNull();
    }

    return result;
  }

  /**
   * Set an argument expression for a function.  This method is called by the
   * XPath compiler.
   *
   * @param arg non-null expression that represents the argument.
   * @param argNum The argument number index.
   *
   * @throws WrongNumberArgsException If the argNum parameter is beyond what
   * is specified for this function.
   */
  public void setArg(Expression arg, int argNum)
          throws WrongNumberArgsException
  {
    m_argVec.addElement(arg);
    arg.exprSetParent(this);
  }

  /**
   * Check that the number of arguments passed to this function is correct.
   *
   *
   * @param argNum The number of arguments that is being passed to the function.
   *
   * @throws WrongNumberArgsException
   */
  public void checkNumberArgs(int argNum) throws WrongNumberArgsException{}


  class ArgExtOwner implements ExpressionOwner
  {
  
    Expression m_exp;
  	
  	ArgExtOwner(Expression exp)
  	{
  		m_exp = exp;
  	}
  	
    /**
     * @see ExpressionOwner#getExpression()
     */
    public Expression getExpression()
    {
      return m_exp;
    }


    /**
     * @see ExpressionOwner#setExpression(Expression)
     */
    public void setExpression(Expression exp)
    {
    	exp.exprSetParent(FuncExtFunction.this);
    	m_exp = exp;
    }
  }
  
  
  /**
   * Call the visitors for the function arguments.
   */
  public void callArgVisitors(XPathVisitor visitor)
  {
      for (int i = 0; i < m_argVec.size(); i++)
      {
         Expression exp = (Expression)m_argVec.elementAt(i);
         exp.callVisitors(new ArgExtOwner(exp), visitor);
      }
    
  }

  /**
   * Set the parent node.
   * For an extension function, we also need to set the parent
   * node for all argument expressions.
   * 
   * @param n The parent node
   */
  public void exprSetParent(ExpressionNode n) 
  {
	
    super.exprSetParent(n);
      
    int nArgs = m_argVec.size();

    for (int i = 0; i < nArgs; i++)
    {
      Expression arg = (Expression) m_argVec.elementAt(i);

      arg.exprSetParent(n);
    }		
  }

  /**
   * Constructs and throws a WrongNumberArgException with the appropriate
   * message for this function object.  This class supports an arbitrary
   * number of arguments, so this method must never be called.
   *
   * @throws WrongNumberArgsException
   */
  protected void reportWrongNumberArgs() throws WrongNumberArgsException {
    String fMsg = XSLMessages.createXPATHMessage(
        XPATHErrorResources.ER_INCORRECT_PROGRAMMER_ASSERTION,
        new Object[]{ "Programmer's assertion:  the method FunctionMultiArgs.reportWrongNumberArgs() should never be called." });

    throw new RuntimeException(fMsg);
  }
  
  /**
   * Return the name of the extesion function in string format
   */
  public String toString()
  {
    if (m_namespace != null && m_namespace.length() > 0)
      return "{" + m_namespace + "}" + m_extensionName;
    else
      return m_extensionName;
  }  
}