/*
    * $Id: ELContextImpl.java 836180 2009-11-14 14:00:02Z 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.el;
  
  import java.lang.reflect.Method;
  import java.util.HashMap;
  import java.util.Map;
  
  import javax.el.ELContext;
  import javax.el.ELResolver;
  import javax.el.FunctionMapper;
  import javax.el.ValueExpression;
  import javax.el.VariableMapper;
  
  /**
   * Implementation of ELContext.<br>
   * Copied from Apache Tomcat 6.0.16 source code.
   *
   * @since 2.2.1
   */
  public class ELContextImpl extends ELContext {
  
      /**
       * A null function mapper.
       */
      private static final FunctionMapper NULL_FUNCTION_MAPPER = new FunctionMapper() {
          @Override
          public Method resolveFunction(String prefix, String localName) {
              return null;
          }
      };
  
      /**
       * Default implementation for the variable mapper.
       */
      private static final class VariableMapperImpl extends VariableMapper {
  
          /**
           * The mapped variables.
           */
          private Map<String, ValueExpression> vars;
  
          /** {@inheritDoc} */
          @Override
          public ValueExpression resolveVariable(String variable) {
              if (vars == null) {
                  return null;
              }
              return vars.get(variable);
          }
  
          /** {@inheritDoc} */
          @Override
          public ValueExpression setVariable(String variable,
                  ValueExpression expression) {
              if (vars == null) {
                  vars = new HashMap<String, ValueExpression>();
              }
              return vars.put(variable, expression);
          }
  
      }
  
      /**
       * The EL resolver to use.
       */
      private final ELResolver resolver;
  
      /**
       * The function mapper to use.
       */
      private FunctionMapper functionMapper = NULL_FUNCTION_MAPPER;
  
      /**
       * The variable mapper to use.
       */
      private VariableMapper variableMapper;
  
      /**
       * Constructor.
      *
      * @param resolver The resolver to use.
      */
     public ELContextImpl(ELResolver resolver) {
         this.resolver = resolver;
     }
 
     /** {@inheritDoc} */
     @Override
     public ELResolver getELResolver() {
         return this.resolver;
     }
 
     /** {@inheritDoc} */
     @Override
     public FunctionMapper getFunctionMapper() {
         return this.functionMapper;
     }
 
     /** {@inheritDoc} */
     @Override
     public VariableMapper getVariableMapper() {
         if (this.variableMapper == null) {
             this.variableMapper = new VariableMapperImpl();
         }
         return this.variableMapper;
     }
 
     /**
      * Sets the function mapper to use.
      *
      * @param functionMapper The function mapper.
      * @since 2.2.1
      */
     public void setFunctionMapper(FunctionMapper functionMapper) {
         this.functionMapper = functionMapper;
     }
 
     /**
      * Sets the variable mapper to use.
      *
      * @param variableMapper The variable mapper.
      * @since 2.2.1
      */
     public void setVariableMapper(VariableMapper variableMapper) {
         this.variableMapper = variableMapper;
     }
 }