/*
    * 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.compiler;
  
  import java.util.Arrays;
  
  import org.apache.commons.jxpath.Function;
  import org.apache.commons.jxpath.JXPathFunctionNotFoundException;
  import org.apache.commons.jxpath.NodeSet;
  import org.apache.commons.jxpath.ri.EvalContext;
  import org.apache.commons.jxpath.ri.QName;
  import org.apache.commons.jxpath.ri.axes.NodeSetContext;
  
  /**
   * Represents an element of the parse tree representing an extension function
   * call.
   *
   * @author Dmitri Plotnikov
   * @version $Revision: 652845 $ $Date: 2008-05-02 19:46:46 +0200 (Fr, 02 Mai 2008) $
   */
  public class ExtensionFunction extends Operation {
  
      private QName functionName;
  
      /**
       * Create a new ExtensionFunction.
       * @param functionName name of the function
       * @param args Expression[] of function args
       */
      public ExtensionFunction(QName functionName, Expression[] args) {
          super(args);
          this.functionName = functionName;
      }
  
      /**
       * Get the function name
       * @return QName
       */
      public QName getFunctionName() {
          return functionName;
      }
  
      /**
       * An extension function gets the current context, therefore it MAY be
       * context dependent.
       * @return true
       */
      public boolean computeContextDependent() {
          return true;
      }
  
      public String toString() {
          StringBuffer buffer = new StringBuffer();
          buffer.append(functionName);
          buffer.append('(');
          Expression[] args = getArguments();
          if (args != null) {
              for (int i = 0; i < args.length; i++) {
                  if (i > 0) {
                      buffer.append(", ");
                  }
                  buffer.append(args[i]);
              }
          }
          buffer.append(')');
          return buffer.toString();
      }
  
      public Object compute(EvalContext context) {
          return computeValue(context);
      }
  
      public Object computeValue(EvalContext context) {
          Object[] parameters = null;
          if (args != null) {
              parameters = new Object[args.length];
              for (int i = 0; i < args.length; i++) {
                  parameters[i] = convert(args[i].compute(context));
              }
          }
  
          Function function =
              context.getRootContext().getFunction(functionName, parameters);
          if (function == null) {
              throw new JXPathFunctionNotFoundException("No such function: "
                     + functionName + Arrays.asList(parameters));
         }
         Object result = function.invoke(context, parameters);
         return result instanceof NodeSet ? new NodeSetContext(context,
                 (NodeSet) result) : result;
     }
 
     /**
      * Convert any incoming context to a value.
      * @param object Object to convert
      * @return context value or <code>object</code> unscathed.
      */
     private Object convert(Object object) {
         return object instanceof EvalContext ? ((EvalContext) object).getValue() : object;
     }
 }