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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.beans.FeatureDescriptor;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
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.PropertyNotFoundException;
import org.activiti.engine.impl.javax.el.PropertyNotWritableException;

/**
 * Simple root property resolver implementation. This resolver handles root properties (i.e. base == null && property instanceof String), which are stored in a map. The properties
 * can be accessed via the {@link #getProperty(String)}, {@link #setProperty(String, Object)}, {@link #isProperty(String)} and {@link #properties()} methods.
 * 
 * @author Christoph Beck
 */
public class RootPropertyResolver extends ELResolver {
  private final Map map = Collections.synchronizedMap(new HashMap());
  private final boolean readOnly;

  /**
   * Create a read/write root property resolver
   */
  public RootPropertyResolver() {
    this(false);
  }

  /**
   * Create a root property resolver
   * 
   * @param readOnly
   */
  public RootPropertyResolver(boolean readOnly) {
    this.readOnly = readOnly;
  }

  private boolean isResolvable(Object base) {
    return base == null;
  }

  private boolean resolve(ELContext context, Object base, Object property) {
    context.setPropertyResolved(isResolvable(base) && property instanceof String);
    return context.isPropertyResolved();
  }

  @Override
  public Class getCommonPropertyType(ELContext context, Object base) {
    return isResolvable(context) ? String.class : null;
  }

  @Override
  public Iterator getFeatureDescriptors(ELContext context, Object base) {
    return null;
  }

  @Override
  public Class getType(ELContext context, Object base, Object property) {
    return resolve(context, base, property) ? Object.class : null;
  }

  @Override
  public Object getValue(ELContext context, Object base, Object property) {
    if (resolve(context, base, property)) {
      if (!isProperty((String) property)) {
        throw new PropertyNotFoundException("Cannot find property " + property);
      }
      return getProperty((String) property);
    }
    return null;
  }

  @Override
  public boolean isReadOnly(ELContext context, Object base, Object property) {
    return resolve(context, base, property) ? readOnly : false;
  }

  @Override
  public void setValue(ELContext context, Object base, Object property, Object value) throws PropertyNotWritableException {
    if (resolve(context, base, property)) {
      if (readOnly) {
        throw new PropertyNotWritableException("Resolver is read only!");
      }
      setProperty((String) property, value);
    }
  }

  @Override
  public Object invoke(ELContext context, Object base, Object method, Class[] paramTypes, Object[] params) {
    if (resolve(context, base, method)) {
      throw new NullPointerException("Cannot invoke method " + method + " on null");
    }
    return null;
  }

  /**
   * Get property value
   * 
   * @param property
   *          property name
   * @return value associated with the given property
   */
  public Object getProperty(String property) {
    return map.get(property);
  }

  /**
   * Set property value
   * 
   * @param property
   *          property name
   * @param value
   *          property value
   */
  public void setProperty(String property, Object value) {
    map.put(property, value);
  }

  /**
   * Test property
   * 
   * @param property
   *          property name
   * @return true if the given property is associated with a value
   */
  public boolean isProperty(String property) {
    return map.containsKey(property);
  }

  /**
   * Get properties
   * 
   * @return all property names (in no particular order)
   */
  public Iterable properties() {
    return map.keySet();
  }
}