/*
    * $Id: ComponentContext.java 471754 2006-11-06 14:55:09Z husted $
    *
    * 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.struts.tiles;
  
  import java.io.Serializable;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.Iterator;
  import java.util.Map;
  import java.util.Set;
  
  import javax.servlet.ServletRequest;
  import javax.servlet.jsp.PageContext;
  
  import org.apache.struts.tiles.taglib.ComponentConstants;
  
  /**
   * Component context.
   */
  public class ComponentContext implements Serializable {
  
      /**
       * Component attributes.
       */
      private Map attributes=null;
  
      /**
       * Constructor.
       */
      public ComponentContext() {
          super();
      }
  
      /**
       * Constructor.
       * Create a context and set specified attributes.
       * @param attributes Attributes to initialize context.
       */
      public ComponentContext(Map attributes) {
          if (attributes != null) {
              this.attributes = new HashMap(attributes);
          }
      }
  
      /**
       * Add all attributes to this context.
       * Copies all of the mappings from the specified attribute map to this context.
       * New attribute mappings will replace any mappings that this context had for any of the keys
       * currently in the specified attribute map.
       * @param newAttributes Attributes to add.
       */
      public void addAll(Map newAttributes) {
          if (attributes == null) {
              attributes = new HashMap(newAttributes);
              return;
          }
  
          attributes.putAll(newAttributes);
      }
  
      /**
       * Add all missing attributes to this context.
       * Copies all of the mappings from the specified attributes map to this context.
       * New attribute mappings will be added only if they don't already exist in
       * this context.
       * @param defaultAttributes Attributes to add.
       */
      public void addMissing(Map defaultAttributes) {
          if (defaultAttributes == null) {
              return;
          }
  
          if (attributes == null) {
              attributes = new HashMap(defaultAttributes);
              return;
          }
  
          Set entries = defaultAttributes.entrySet();
          Iterator iterator = entries.iterator();
          while (iterator.hasNext()) {
             Map.Entry entry = (Map.Entry) iterator.next();
             if (!attributes.containsKey(entry.getKey())) {
                 attributes.put(entry.getKey(), entry.getValue());
             }
         }
     }
 
     /**
      * Get an attribute from context.
      * @param name Name of the attribute.
      * @return <{Object}>
      */
     public Object getAttribute(String name) {
         if (attributes == null){
             return null;
         }
 
         return attributes.get(name);
     }
 
     /**
      * Get names of all attributes.
      * @return <{Object}>
      */
     public Iterator getAttributeNames() {
         if (attributes == null) {
             return Collections.EMPTY_LIST.iterator();
         }
 
         return attributes.keySet().iterator();
     }
 
     /**
      * Put a new attribute to context.
      * @param name Name of the attribute.
      * @param value Value of the attribute.
      */
     public void putAttribute(String name, Object value) {
         if (attributes == null) {
             attributes = new HashMap();
         }
 
         attributes.put(name, value);
     }
 
     /**
      * Find object in one of the contexts.
      * Order : component then pageContext.findAttribute()
      * @param beanName Name of the bean to find.
      * @param pageContext Page context.
      * @return Requested bean or <code>null</code> if not found.
      */
     public Object findAttribute(String beanName, PageContext pageContext) {
         Object attribute = getAttribute(beanName);
         if (attribute == null) {
             attribute = pageContext.findAttribute(beanName);
         }
 
         return attribute;
     }
 
     /**
      * Get object from requested context.
      * Context can be 'component'.
      * @param beanName Name of the bean to find.
      * @param scope Search scope (see {@link PageContext}).
      * @param pageContext Page context.
      * @return requested bean or <code>null</code> if not found.
      */
     public Object getAttribute(
         String beanName,
         int scope,
         PageContext pageContext) {
 
         if (scope == ComponentConstants.COMPONENT_SCOPE){
             return getAttribute(beanName);
         }
 
         return pageContext.getAttribute(beanName, scope);
     }
 
     /**
      * Get component context from request.
      * @param request ServletRequest.
      * @return ComponentContext or null if context is not found or an
      * jspException is present in the request.
      */
     static public ComponentContext getContext(ServletRequest request) {
        if (request.getAttribute("javax.servlet.jsp.jspException") != null) {
            return null;
         }        return (ComponentContext) request.getAttribute(
             ComponentConstants.COMPONENT_CONTEXT);
     }
 
     /**
      * Store component context into request.
      * @param context ComponentContext to store.
      * @param request Request to store ComponentContext.
      */
     static public void setContext(
         ComponentContext context,
         ServletRequest request) {
 
         request.setAttribute(ComponentConstants.COMPONENT_CONTEXT, context);
     }
 }