/*
    * 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.
   */
  public class ExtensionFunction extends Operation {
  
      private final QName functionName;
  
      /**
       * Constructs a new ExtensionFunction.
       *
       * @param functionName name of the function
       * @param args         Expression[] of function args
       */
      public ExtensionFunction(final QName functionName, final Expression[] args) {
          super(args);
          this.functionName = functionName;
      }
  
      @Override
      public Object compute(final EvalContext context) {
          return computeValue(context);
      }
  
      /**
       * An extension function gets the current context, therefore it MAY be context dependent.
       *
       * @return true
       */
      @Override
      public boolean computeContextDependent() {
          return true;
      }
  
      @Override
      public Object computeValue(final 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));
              }
          }
          final Function function = context.getRootContext().getFunction(functionName, parameters);
          if (function == null) {
              throw new JXPathFunctionNotFoundException("No such function: " + functionName + Arrays.asList(parameters));
          }
          final 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} unscathed.
       */
      private Object convert(final Object object) {
          return object instanceof EvalContext ? ((EvalContext) object).getValue() : object;
      }
  
      /**
       * Gets the function name
       *
       * @return QName
       */
      public QName getFunctionName() {
          return functionName;
      }
  
      @Override
      public String toString() {
         final StringBuilder buffer = new StringBuilder();
         buffer.append(functionName);
         buffer.append('(');
         final 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();
     }
 }