/*
 * Copyright 2002-2007 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.context.config;

import org.w3c.dom.Element;

import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.support.AbstractBeanDefinition;
import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.beans.factory.support.RootBeanDefinition;
import org.springframework.beans.factory.xml.AbstractSingleBeanDefinitionParser;
import org.springframework.beans.factory.xml.ParserContext;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.util.ClassUtils;

/**
 * Parser for the <context:load-time-weaver/> element.
 *
 * @author Juergen Hoeller
 * @since 2.5
 */
class LoadTimeWeaverBeanDefinitionParser extends AbstractSingleBeanDefinitionParser {

	private static final String WEAVER_CLASS_ATTRIBUTE = "weaver-class";

	private static final String ASPECTJ_WEAVING_ATTRIBUTE = "aspectj-weaving";

	private static final String ASPECTJ_AOP_XML_RESOURCE = "META-INF/aop.xml";

	private static final String DEFAULT_LOAD_TIME_WEAVER_CLASS_NAME =
			"org.springframework.context.weaving.DefaultContextLoadTimeWeaver";

	private static final String ASPECTJ_WEAVING_ENABLER_CLASS_NAME =
			"org.springframework.context.weaving.AspectJWeavingEnabler";


	protected String getBeanClassName(Element element) {
		if (element.hasAttribute(WEAVER_CLASS_ATTRIBUTE)) {
			return element.getAttribute(WEAVER_CLASS_ATTRIBUTE);
		}
		return DEFAULT_LOAD_TIME_WEAVER_CLASS_NAME;
	}

	protected String resolveId(Element element, AbstractBeanDefinition definition, ParserContext parserContext) {
		return ConfigurableApplicationContext.LOAD_TIME_WEAVER_BEAN_NAME;
	}

	protected void doParse(Element element, ParserContext parserContext, BeanDefinitionBuilder builder) {
		builder.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);

		if (isAspectJWeavingEnabled(element.getAttribute(ASPECTJ_WEAVING_ATTRIBUTE), parserContext)) {
			RootBeanDefinition weavingEnablerDef = new RootBeanDefinition();
			weavingEnablerDef.setBeanClassName(ASPECTJ_WEAVING_ENABLER_CLASS_NAME);
			parserContext.getReaderContext().registerWithGeneratedName(weavingEnablerDef);

			if (isBeanConfigurerAspectEnabled(parserContext.getReaderContext().getBeanClassLoader())) {
				new SpringConfiguredBeanDefinitionParser().parse(element, parserContext);
			}
		}
	}

	protected boolean isAspectJWeavingEnabled(String value, ParserContext parserContext) {
		if ("on".equals(value)) {
			return true;
		}
		else if ("off".equals(value)) {
			return false;
		}
		else {
			// Determine default...
			ClassLoader cl = parserContext.getReaderContext().getResourceLoader().getClassLoader();
			return (cl.getResource(ASPECTJ_AOP_XML_RESOURCE) != null);
		}
	}

	protected boolean isBeanConfigurerAspectEnabled(ClassLoader beanClassLoader) {
		return ClassUtils.isPresent(SpringConfiguredBeanDefinitionParser.BEAN_CONFIGURER_ASPECT_CLASS_NAME,
				beanClassLoader);
	}

}