/*
    * Copyright 2006-2007 the original author or authors.
    *
    * 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.springframework.batch.repeat.context;
  
  import org.springframework.core.AttributeAccessor;
  import org.springframework.core.AttributeAccessorSupport;
  
  /**
   * An {@link AttributeAccessor} that synchronizes on a mutex (not this) before
   * modifying or accessing the underlying attributes.
   * 
   * @author Dave Syer
   * 
   */
  public class SynchronizedAttributeAccessor implements AttributeAccessor {
  
  	/**
  	 * All methods are delegated to this support object.
  	 */
  	AttributeAccessorSupport support = new AttributeAccessorSupport() {
  		/**
  		 * Generated serial UID.
  		 */
  		private static final long serialVersionUID = -7664290016506582290L;
  	};
  
  	/*
  	 * (non-Javadoc)
  	 * @see org.springframework.core.AttributeAccessor#attributeNames()
  	 */
  	public String[] attributeNames() {
  		synchronized (support) {
  			return support.attributeNames();
  		}
  	}
  
  	/*
  	 * (non-Javadoc)
  	 * @see java.lang.Object#equals(java.lang.Object)
  	 */
  	public boolean equals(Object other) {
  		if (this == other) {
  			return true;
  		}
  		AttributeAccessorSupport that;
  		if (other instanceof SynchronizedAttributeAccessor) {
  			that = ((SynchronizedAttributeAccessor) other).support;
  		}
  		else if (other instanceof AttributeAccessorSupport) {
  			that = (AttributeAccessorSupport) other;
  		}
  		else {
  			return false;
  		}
  		synchronized (support) {
  			return support.equals(that);
  		}
  	}
  
  	/*
  	 * (non-Javadoc)
  	 * @see org.springframework.core.AttributeAccessor#getAttribute(java.lang.String)
  	 */
  	public Object getAttribute(String name) {
  		synchronized (support) {
  			return support.getAttribute(name);
  		}
  	}
  
  	/*
  	 * (non-Javadoc)
  	 * @see org.springframework.core.AttributeAccessor#hasAttribute(java.lang.String)
  	 */
  	public boolean hasAttribute(String name) {
  		synchronized (support) {
  			return support.hasAttribute(name);
  		}
  	}
  
  	/*
  	 * (non-Javadoc)
  	 * @see java.lang.Object#hashCode()
  	 */
  	public int hashCode() {
  		return support.hashCode();
 	}
 
 	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.core.AttributeAccessor#removeAttribute(java.lang.String)
 	 */
 	public Object removeAttribute(String name) {
 		synchronized (support) {
 			return support.removeAttribute(name);
 		}
 	}
 
 	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.core.AttributeAccessor#setAttribute(java.lang.String,
 	 * java.lang.Object)
 	 */
 	public void setAttribute(String name, Object value) {
 		synchronized (support) {
 			support.setAttribute(name, value);
 		}
 	}
 
 	/**
 	 * Additional support for atomic put if absent.
 	 * @param name the key for the attribute name
 	 * @param value the value of the attribute
 	 * @return null if the attribute was not already set, the existing value
 	 * otherwise.
 	 */
 	public Object setAttributeIfAbsent(String name, Object value) {
 		synchronized (support) {
 			Object old = getAttribute(name);
 			if (old != null) {
 				return old;
 			}
 			setAttribute(name, value);
 		}
 		return null;
 	}
 
 	/*
 	 * (non-Javadoc)
 	 * @see java.lang.Object#toString()
 	 */
 	public String toString() {
 		StringBuffer buffer = new StringBuffer("SynchronizedAttributeAccessor: [");
 		synchronized (support) {
 			String[] names = attributeNames();
 			for (int i = 0; i < names.length; i++) {
 				String name = names[i];
 				buffer.append(names[i]).append("=").append(getAttribute(name));
 				if (i < names.length - 1) {
 					buffer.append(", ");
 				}
 			}
 			buffer.append("]");
 			return buffer.toString();
 		}
 	}
 
 }