/*
    * $Id: VelocityUtil.java 902965 2010-01-25 20:12:46Z apetrelli $
    *
    * 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.tiles.velocity.context;
  
  import java.io.IOException;
  import java.io.StringWriter;
  import java.io.Writer;
  import java.util.Map;
  
  import javax.servlet.ServletContext;
  import javax.servlet.http.HttpServletRequest;
  
  import org.apache.tiles.ArrayStack;
  import org.apache.velocity.context.Context;
  import org.apache.velocity.context.InternalContextAdapter;
  import org.apache.velocity.runtime.Renderable;
  import org.apache.velocity.runtime.parser.node.ASTBlock;
  import org.apache.velocity.runtime.parser.node.ASTMap;
  import org.apache.velocity.runtime.parser.node.Node;
  
  /***
   * Utilities for Velocity usage in Tiles.
   *
   * @version $Rev: 902965 $ $Date: 2010-01-25 21:12:46 +0100 (lun, 25 gen 2010) $
   * @since 2.2.0
   */
  public final class VelocityUtil {
  
      /***
       * A renderable object that does not render anything.
       *
       * @since 2.2.0
       */
      public static final Renderable EMPTY_RENDERABLE;
  
      static {
          EMPTY_RENDERABLE = new Renderable() {
  
              @Override
              public String toString() {
                  return "";
              }
  
              public boolean render(InternalContextAdapter context, Writer writer) {
                  // Does nothing, really!
                  return true;
              }
          };
      }
  
      /***
       * The attribute key that will be used to store the parameter map, to use across Velocity tool calls.
       *
       * @since 2.2.0
       */
      private static final String PARAMETER_MAP_STACK_KEY = "org.apache.tiles.velocity.PARAMETER_MAP_STACK";
  
      /***
       * Private constructor to avoid instantiation.
       */
      private VelocityUtil() {
      }
  
      /***
       * Null-safe conversion from Boolean to boolean.
       *
       * @param obj The Boolean object.
       * @param defaultValue This value will be returned if <code>obj</code> is null.
       * @return The boolean value of <code>obj</code> or, if null, <code>defaultValue</code>.
       * @since 2.2.0
       */
      public static boolean toSimpleBoolean(Boolean obj, boolean defaultValue) {
          return obj != null ? obj : defaultValue;
      }
  
      /***
       * Returns or creates the parameter stack to use. It is useful to store parameters across tool calls.
       *
       * @param context The Velocity context.
       * @return The parameter stack.
      * @since 2.2.0
      * @deprecated Use Velocity directives.
      */
     @Deprecated
     @SuppressWarnings("unchecked")
     public static ArrayStack<Map<String, Object>> getParameterStack(Context context) {
         ArrayStack<Map<String, Object>> stack = (ArrayStack<Map<String, Object>>) context
                 .get(PARAMETER_MAP_STACK_KEY);
         if (stack == null) {
             stack = new ArrayStack<Map<String, Object>>();
             context.put(PARAMETER_MAP_STACK_KEY, stack);
         }
         return stack;
     }
 
     /***
      * Sets an attribute in the desired scope.
      *
      * @param velocityContext The Velocity context.
      * @param request The HTTP request.
      * @param servletContext The servlet context.
      * @param name The name of the attribute.
      * @param obj The value of the attribute.
      * @param scope The scope. It can be <code>page</code>, <code>request</code>
      * , <code>session</code>, <code>application</code>.
      * @since 2.2.0
      */
     public static void setAttribute(Context velocityContext,
             HttpServletRequest request, ServletContext servletContext,
             String name, Object obj, String scope) {
         if (scope == null) {
             scope = "page";
         }
         if ("page".equals(scope)) {
             velocityContext.put(name, obj);
         } else if ("request".equals(scope)) {
             request.setAttribute(name, obj);
         } else if ("session".equals(scope)) {
             request.getSession().setAttribute(name, obj);
         } else if ("application".equals(scope)) {
             servletContext.setAttribute(name, obj);
         }
     }
 
     /***
      * Evaluates the body (child node at position 1) and returns it as a string.
      *
      * @param context The Velocity context.
      * @param node The node to use.
      * @return The evaluated body.
      * @throws IOException If something goes wrong.
      * @since 2.2.2
      */
     public static String getBodyAsString(InternalContextAdapter context, Node node)
             throws IOException {
         ASTBlock block = (ASTBlock) node.jjtGetChild(1);
         StringWriter stringWriter = new StringWriter();
         block.render(context, stringWriter);
         stringWriter.close();
         String body = stringWriter.toString();
         if (body != null) {
             body = body.replaceAll("^//s*|//s*$", "");
             if (body.length() <= 0) {
                 body = null;
             }
         }
         return body;
     }
 
     /***
      * Evaluates the body writing in the passed writer.
      *
      * @param context The Velocity context.
      * @param writer The writer to write into.
      * @param node The node to use.
      * @throws IOException If something goes wrong.
      * @since 2.2.2
      */
     public static void evaluateBody(InternalContextAdapter context, Writer writer,
             Node node) throws IOException {
         ASTBlock block = (ASTBlock) node.jjtGetChild(1);
         block.render(context, writer);
     }
 
     /***
      * Extracts the parameters from the directives, by getting the child at
      * position 0 supposing it is a map.
      *
      * @param context The Velocity context.
      * @param node The node to use.
      * @return The extracted parameters.
      * @since 2.2.2
      */
     @SuppressWarnings("unchecked")
     public static Map<String, Object> getParameters(InternalContextAdapter context,
             Node node) {
         ASTMap astMap = (ASTMap) node.jjtGetChild(0);
         Map<String, Object> params = (Map<String, Object>) astMap
                 .value(context);
         return params;
     }
 }