package org.apache.velocity.runtime.parser.node;
   
   import org.apache.velocity.context.InternalContextAdapter;
   import org.apache.velocity.exception.MethodInvocationException;
   import org.apache.velocity.exception.TemplateInitException;
   import org.apache.velocity.exception.VelocityException;
   import org.apache.velocity.runtime.RuntimeConstants;
   import org.apache.velocity.runtime.log.Log;
   import org.apache.velocity.runtime.parser.Parser;
  import org.apache.velocity.util.ClassUtils;
  import org.apache.velocity.util.introspection.VelMethod;
  
  /*
   * 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.    
   */
  
  /**
   *  This node is responsible for the bracket notation at the end of
   *  a reference, e.g., $foo[1]
   */
  
  public class ASTIndex extends SimpleNode
  {
      private final String methodName = "get";
  
      /**
       * Indicates if we are running in strict reference mode.
       */
      protected boolean strictRef = false;
  
      public ASTIndex(int i)
      {
          super(i);
      }
  
      public ASTIndex(Parser p, int i)
      {
          super(p, i);
      }
    
      public Object init(InternalContextAdapter context, Object data)
          throws TemplateInitException
      {
          super.init(context, data);    
          strictRef = rsvc.getBoolean(RuntimeConstants.RUNTIME_REFERENCES_STRICT, false);
          return data;
      }  
  
  
      
      private final static Object[] noParams = {};
      private final static Class[] noTypes = {};      
      /**
       * If argument is an Integer and negative, then return (o.size() - argument). 
       * Otherwise return the original argument.  We use this to calculate the true
       * index of a negative index e.g., $foo[-1]. If no size() method is found on the
       * 'o' object, then we throw an VelocityException.
       * @param context Used to access the method cache.
       * @param node  ASTNode used for error reporting.
       */
      public static Object adjMinusIndexArg(Object argument, Object o, 
                                 InternalContextAdapter context, SimpleNode node)
      {
        if (argument instanceof Integer && ((Integer)argument).intValue() < 0)
        {
            // The index value is a negative number, $foo[-1], so we want to actually
            // Index [size - value], so try and call the size method.
            VelMethod method = ClassUtils.getMethod("size", noParams, noTypes, 
                               o, context, node, false);
            if (method == null)
            {
                // The object doesn't have a size method, so there is no notion of "at the end"
                throw new VelocityException(
                  "A 'size()' method required for negative value "
                   + ((Integer)argument).intValue() + " does not exist for class '" 
                   + o.getClass().getName() + "' at " + Log.formatFileString(node));
            }             
  
            Object size = null;
            try
            {
                size = method.invoke(o, noParams);
            }
            catch (Exception e)
           {
               throw new VelocityException("Error trying to calls the 'size()' method on '"
                 + o.getClass().getName() + "' at " + Log.formatFileString(node), e);
           }
           
           int sizeint = 0;          
           try
           {
               sizeint = ((Integer)size).intValue();
           }
           catch (ClassCastException e)
           {
               // If size() doesn't return an Integer we want to report a pretty error
               throw new VelocityException("Method 'size()' on class '" 
                   + o.getClass().getName() + "' returned '" + size.getClass().getName()
                   + "' when Integer was expected at " + Log.formatFileString(node));
           }
           
           argument = new Integer(sizeint + ((Integer)argument).intValue());
       }
       
       // Nothing to do, return the original argument
       return argument;
     }
     
     public Object execute(Object o, InternalContextAdapter context)
         throws MethodInvocationException
     {
         Object argument = jjtGetChild(0).value(context);
         // If negative, turn -1 into size - 1
         argument = adjMinusIndexArg(argument, o, context, this);
         Object [] params = {argument};
         Class[] paramClasses = {argument == null ? null : argument.getClass()};
 
         VelMethod method = ClassUtils.getMethod(methodName, params, paramClasses, 
                                                 o, context, this, strictRef);
 
         if (method == null) return null;
     
         try
         {
             /*
              *  get the returned object.  It may be null, and that is
              *  valid for something declared with a void return type.
              *  Since the caller is expecting something to be returned,
              *  as long as things are peachy, we can return an empty
              *  String so ASTReference() correctly figures out that
              *  all is well.
              */
             Object obj = method.invoke(o, params);
 
             if (obj == null)
             {
                 if( method.getReturnType() == Void.TYPE)
                 {
                     return "";
                 }
             }
 
             return obj;
         }
         /**
          * pass through application level runtime exceptions
          */
         catch( RuntimeException e )
         {
             throw e;
         }
         catch( Exception e )
         {
             String msg = "Error invoking method 'get("
               + (argument == null ? "null" : argument.getClass().getName()) 
               + ")' in " + o.getClass().getName()
               + " at " + Log.formatFileString(this);
             log.error(msg, e);
             throw new VelocityException(msg, e);
         }
     }  
 }