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/*
 * Based on JUEL 2.2.1 code, 2006-2009 Odysseus Software GmbH
 *
 * Licensed 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.activiti.engine.impl.juel;

import java.lang.reflect.Method;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

import org.activiti.engine.impl.javax.el.ELContext;
import org.activiti.engine.impl.javax.el.ELResolver;
import org.activiti.engine.impl.javax.el.FunctionMapper;
import org.activiti.engine.impl.javax.el.ValueExpression;
import org.activiti.engine.impl.javax.el.VariableMapper;

/**
 * Simple context implementation.
 * 
 * @author Christoph Beck
 */
public class SimpleContext extends ELContext {
  static class Functions extends FunctionMapper {
    Map map = Collections.emptyMap();

    @Override
    public Method resolveFunction(String prefix, String localName) {
      return map.get(prefix + ":" + localName);
    }

    public void setFunction(String prefix, String localName, Method method) {
      if (map.isEmpty()) {
        map = new HashMap();
      }
      map.put(prefix + ":" + localName, method);
    }
  }

  static class Variables extends VariableMapper {
    Map map = Collections.emptyMap();

    @Override
    public ValueExpression resolveVariable(String variable) {
      return map.get(variable);
    }

    @Override
    public ValueExpression setVariable(String variable, ValueExpression expression) {
      if (map.isEmpty()) {
        map = new HashMap();
      }
      return map.put(variable, expression);
    }
  }

  private Functions functions;
  private Variables variables;
  private ELResolver resolver;

  /**
   * Create a context.
   */
  public SimpleContext() {
    this(null);
  }

  /**
   * Create a context, use the specified resolver.
   */
  public SimpleContext(ELResolver resolver) {
    this.resolver = resolver;
  }

  /**
   * Define a function.
   */
  public void setFunction(String prefix, String localName, Method method) {
    if (functions == null) {
      functions = new Functions();
    }
    functions.setFunction(prefix, localName, method);
  }

  /**
   * Define a variable.
   */
  public ValueExpression setVariable(String name, ValueExpression expression) {
    if (variables == null) {
      variables = new Variables();
    }
    return variables.setVariable(name, expression);
  }

  /**
   * Get our function mapper.
   */
  @Override
  public FunctionMapper getFunctionMapper() {
    if (functions == null) {
      functions = new Functions();
    }
    return functions;
  }

  /**
   * Get our variable mapper.
   */
  @Override
  public VariableMapper getVariableMapper() {
    if (variables == null) {
      variables = new Variables();
    }
    return variables;
  }

  /**
   * Get our resolver. Lazy initialize to a {@link SimpleResolver} if necessary.
   */
  @Override
  public ELResolver getELResolver() {
    if (resolver == null) {
      resolver = new SimpleResolver();
    }
    return resolver;
  }

  /**
   * Set our resolver.
   * 
   * @param resolver
   */
  public void setELResolver(ELResolver resolver) {
    this.resolver = resolver;
  }
}