/*
    * Copyright 2006-2008 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.osgi.context.support;
  
  import java.beans.PropertyEditor;
  import java.io.IOException;
  import java.util.Dictionary;
  import java.util.Map;
  
  import org.osgi.framework.Bundle;
  import org.osgi.framework.BundleContext;
  import org.osgi.framework.Constants;
  import org.osgi.framework.ServiceRegistration;
  import org.springframework.beans.BeanUtils;
  import org.springframework.beans.BeansException;
  import org.springframework.beans.factory.BeanFactoryAware;
  import org.springframework.beans.factory.config.BeanPostProcessor;
  import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
  import org.springframework.beans.factory.config.Scope;
  import org.springframework.context.ApplicationContext;
  import org.springframework.context.ApplicationContextException;
  import org.springframework.context.support.AbstractRefreshableApplicationContext;
  import org.springframework.core.io.Resource;
  import org.springframework.core.io.support.ResourcePatternResolver;
  import org.springframework.osgi.context.BundleContextAware;
  import org.springframework.osgi.context.ConfigurableOsgiBundleApplicationContext;
  import org.springframework.osgi.context.internal.classloader.ClassLoaderFactory;
  import org.springframework.osgi.context.support.internal.OsgiBundleScope;
  import org.springframework.osgi.io.OsgiBundleResource;
  import org.springframework.osgi.io.OsgiBundleResourcePatternResolver;
  import org.springframework.osgi.util.OsgiBundleUtils;
  import org.springframework.osgi.util.OsgiServiceUtils;
  import org.springframework.osgi.util.OsgiStringUtils;
  import org.springframework.osgi.util.internal.MapBasedDictionary;
  import org.springframework.util.Assert;
  import org.springframework.util.ClassUtils;
  import org.springframework.util.ObjectUtils;
  import org.springframework.util.StringUtils;
  
  /**
   * 
   * <code>AbstractRefreshableApplicationContext</code> subclass that implements
   * the {@link ConfigurableOsgiBundleApplicationContext} interface for OSGi
   * environments. Pre-implements a <code>configLocation</code> property, to be
   * populated through the <code>ConfigurableOsgiApplicationContext</code>
   * interface after OSGi bundle startup.
   * 
   * <p>
   * This class is as easy to subclass as
   * <code>AbstractRefreshableApplicationContext</code>(see the javadoc for
   * details): all you need to implement is the <code>loadBeanDefinitions</code>
   * method Note that implementations are supposed to load bean definitions from
   * the files specified by the locations returned by
   * <code>getConfigLocations</code> method.
   * 
   * <p>
   * In addition to the special beans detected by
   * <code>AbstractApplicationContext</code>, this class registers the
   * <code>BundleContextAwareProcessor</code> for processing beans that
   * implement the <code>BundleContextAware</code> interface. Also it interprets
   * resource paths as OSGi bundle resources (either from the bundle class space,
   * bundle space or jar space).
   * 
   * <p>
   * This application context implementation offers the OSGi-specific,
   * <em>bundle</em> scope.
   * 
   * <p>
   * <strong>Note:</strong> <code>OsgiApplicationContext</code> implementations
   * are generally supposed to configure themselves based on the configuration
   * received through the <code>ConfigurableOsgiBundleApplicationContext</code>
   * interface. In contrast, a stand-alone application context might allow for
   * configuration in custom startup code (for example,
   * <code>GenericApplicationContext</code>).
   * 
   * @author Costin Leau
   * @author Adrian Colyer
   * @author Hal Hildebrand
   * 
   */
  public abstract class AbstractOsgiBundleApplicationContext extends AbstractRefreshableApplicationContext implements
  		ConfigurableOsgiBundleApplicationContext {
  
  	private static final String EXPORTER_IMPORTER_DEPENDENCY_MANAGER = "org.springframework.osgi.service.dependency.internal.MandatoryDependencyBeanPostProcessor";
  
 	/** OSGi bundle - determined from the BundleContext */
 	private Bundle bundle;
 
 	/** OSGi bundle context */
 	private BundleContext bundleContext;
 
 	/** Path to configuration files */
 	private String[] configLocations;
 
 	/** Used for publishing the app context */
 	private ServiceRegistration serviceRegistration;
 
 	/** Should context be published as an OSGi service? */
 	private boolean publishContextAsService = true;
 
 	/** class loader used for loading the beans */
 	private ClassLoader classLoader;
 
 	/**
 	 * Internal pattern resolver. The parent one can't be used since it is being
 	 * instantiated inside the constructor when the bundle field is not
 	 * initialized yet.
 	 */
 	private ResourcePatternResolver osgiPatternResolver;
 
 
 	/**
 	 * Creates a new <code>AbstractOsgiBundleApplicationContext</code> with no
 	 * parent.
 	 */
 	public AbstractOsgiBundleApplicationContext() {
 		super();
 		setDisplayName("Root OsgiBundleApplicationContext");
 	}
 
 	/**
 	 * Creates a new <code>AbstractOsgiBundleApplicationContext</code> with
 	 * the given parent context.
 	 * 
 	 * @param parent the parent context
 	 */
 	public AbstractOsgiBundleApplicationContext(ApplicationContext parent) {
 		super(parent);
 	}
 
 	/**
 	 * {@inheritDoc}
 	 * 
 	 * <p/> Will automatically determine the bundle, create a new
 	 * <code>ResourceLoader</code> (and set its <code>ClassLoader</code> (if
 	 * none is set already) to a custom implementation that will delegate the
 	 * calls to the bundle).
 	 */
 	public void setBundleContext(BundleContext bundleContext) {
 		this.bundleContext = bundleContext;
 		this.bundle = bundleContext.getBundle();
 		this.osgiPatternResolver = createResourcePatternResolver();
 
 		if (getClassLoader() == null)
 			this.setClassLoader(createBundleClassLoader(this.bundle));
 
 		this.setDisplayName(ClassUtils.getShortName(getClass()) + "(bundle=" + getBundleSymbolicName() + ", config="
 				+ StringUtils.arrayToCommaDelimitedString(getConfigLocations()) + ")");
 	}
 
 	public BundleContext getBundleContext() {
 		return this.bundleContext;
 	}
 
 	public Bundle getBundle() {
 		return this.bundle;
 	}
 
 	public void setConfigLocations(String[] configLocations) {
 		this.configLocations = configLocations;
 	}
 
 	/**
 	 * Returns this application context configuration locations. The default
 	 * implementation will check whether there are any locations configured and,
 	 * if not, will return the default locations.
 	 * 
 	 * @return application context configuration locations.
 	 * @see #getDefaultConfigLocations()
 	 */
 	public String[] getConfigLocations() {
 		return (this.configLocations != null ? this.configLocations : getDefaultConfigLocations());
 	}
 
 	/**
 	 * Unregister the ApplicationContext OSGi service (in case there is any).
 	 */
 	protected void doClose() {
 		if (!OsgiServiceUtils.unregisterService(serviceRegistration)) {
 			logger.info("Unpublishing application context OSGi service for bundle "
 					+ OsgiStringUtils.nullSafeNameAndSymName(bundle));
 			serviceRegistration = null;
 		}
 		else {
 			if (publishContextAsService)
 				logger.info("Application Context service already unpublished");
 		}
 
 		// call super class
 		super.doClose();
 	}
 
 	/*
 	 * Clean up any beans from the bundle scope.
 	 */
 	protected void destroyBeans() {
 		super.destroyBeans();
 
 		try {
 			cleanOsgiBundleScope(getBeanFactory());
 		}
 		catch (Exception ex) {
 			logger.warn("got exception when closing", ex);
 		}
 	}
 
 	/**
 	 * Returns the default configuration locations to use, for the case where no
 	 * explicit configuration locations have been specified.
 	 * <p>
 	 * Default implementation returns <code>null</code>, requiring explicit
 	 * configuration locations.
 	 * 
 	 * @return application context default configuration locations
 	 * @see #setConfigLocations
 	 */
 	protected String[] getDefaultConfigLocations() {
 		return null;
 	}
 
 	protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
 		super.postProcessBeanFactory(beanFactory);
 
 		beanFactory.addBeanPostProcessor(new BundleContextAwareProcessor(this.bundleContext));
 		beanFactory.ignoreDependencyInterface(BundleContextAware.class);
 
 		enforceExporterImporterDependency(beanFactory);
 
 		// add bundleContext bean
 		if (!beanFactory.containsLocalBean(BUNDLE_CONTEXT_BEAN_NAME)) {
 			logger.debug("Registering BundleContext as a bean named " + BUNDLE_CONTEXT_BEAN_NAME);
 			beanFactory.registerSingleton(BUNDLE_CONTEXT_BEAN_NAME, this.bundleContext);
 		}
 		else {
 			logger.warn("A bean named " + BUNDLE_CONTEXT_BEAN_NAME
 					+ " already exists; the bundleContext will not be registered as a bean");
 		}
 
 		// register property editors
 		registerPropertyEditors(beanFactory);
 
 		// register a 'bundle' scope
 		beanFactory.registerScope(OsgiBundleScope.SCOPE_NAME, new OsgiBundleScope());
 	}
 
 	/**
 	 * Takes care of enforcing the relationship between exporter and importers.
 	 * 
 	 * @param beanFactory
 	 */
 	private void enforceExporterImporterDependency(ConfigurableListableBeanFactory beanFactory) {
 		// create the service manager
 		ClassLoader loader = AbstractOsgiBundleApplicationContext.class.getClassLoader();
 		Object instance = null;
 		try {
 			Class managerClass = loader.loadClass(EXPORTER_IMPORTER_DEPENDENCY_MANAGER);
 			instance = BeanUtils.instantiateClass(managerClass);
 		}
 		catch (ClassNotFoundException cnfe) {
 			throw new ApplicationContextException("Cannot load class " + EXPORTER_IMPORTER_DEPENDENCY_MANAGER, cnfe);
 		}
 
 		// sanity check
 		Assert.isInstanceOf(BeanFactoryAware.class, instance);
 		Assert.isInstanceOf(BeanPostProcessor.class, instance);
 		((BeanFactoryAware) instance).setBeanFactory(beanFactory);
 		beanFactory.addBeanPostProcessor((BeanPostProcessor) instance);
 	}
 
 	/**
 	 * Register OSGi-specific {@link PropertyEditor}s.
 	 * 
 	 * @param beanFactory beanFactory used for registration.
 	 */
 	private void registerPropertyEditors(ConfigurableListableBeanFactory beanFactory) {
 		beanFactory.addPropertyEditorRegistrar(new OsgiPropertyEditorRegistrar());
 	}
 
 	private void cleanOsgiBundleScope(ConfigurableListableBeanFactory beanFactory) {
 		Scope scope = beanFactory.getRegisteredScope(OsgiBundleScope.SCOPE_NAME);
 		if (scope != null && scope instanceof OsgiBundleScope) {
 			if (logger.isDebugEnabled())
 				logger.debug("Destroying existing bundle scope beans...");
 			((OsgiBundleScope) scope).destroy();
 		}
 	}
 
 	/**
 	 * Publish the application context as an OSGi service. The method internally
 	 * takes care of parsing the bundle headers and determined if actual
 	 * publishing is required or not.
 	 * 
 	 */
 	void publishContextAsOsgiServiceIfNecessary() {
 		if (publishContextAsService) {
 			Dictionary serviceProperties = new MapBasedDictionary();
 
 			customizeApplicationContextServiceProperties((Map) serviceProperties);
 
 			if (logger.isInfoEnabled()) {
 				logger.info("Publishing application context as OSGi service with properties " + serviceProperties);
 			}
 
 			// export only interfaces
 			Class[] classes = org.springframework.osgi.util.internal.ClassUtils.getClassHierarchy(getClass(),
 				org.springframework.osgi.util.internal.ClassUtils.INCLUDE_INTERFACES);
 
 			// filter classes based on visibility
 			Class[] filterClasses = org.springframework.osgi.util.internal.ClassUtils.getVisibleClasses(classes,
 				this.getClass().getClassLoader());
 
 			String[] serviceNames = org.springframework.osgi.util.internal.ClassUtils.toStringArray(filterClasses);
 
 			if (logger.isDebugEnabled())
 				logger.debug("Publishing service under classes " + ObjectUtils.nullSafeToString(serviceNames));
 
 			// Publish under all the significant interfaces we see
 			this.serviceRegistration = getBundleContext().registerService(serviceNames, this, serviceProperties);
 		}
 		else {
 			if (logger.isInfoEnabled()) {
 				logger.info("Not publishing application context OSGi service for bundle "
 						+ OsgiStringUtils.nullSafeNameAndSymName(bundle));
 			}
 		}
 	}
 
 	/**
 	 * Customizes the properties of the application context OSGi service. This
 	 * method is called only if the application context will be published as an
 	 * OSGi service.
 	 * 
 	 * <p/>The default implementation stores the bundle symbolic name under
 	 * {@link Constants#BUNDLE_SYMBOLICNAME} and
 	 * {@link ConfigurableOsgiBundleApplicationContext#APPLICATION_CONTEXT_SERVICE_PROPERTY_NAME}
 	 * and the bundle version under {@link Constants#BUNDLE_VERSION} property.
 	 * 
 	 * Can be overridden by subclasses to add more properties if needed (for
 	 * example for web applications where multiple application contexts are
 	 * available inside the same bundle).
 	 * 
 	 * @param serviceProperties service properties map (can be casted to
 	 * {@link Dictionary})
 	 */
 	protected void customizeApplicationContextServiceProperties(Map serviceProperties) {
 		serviceProperties.put(APPLICATION_CONTEXT_SERVICE_PROPERTY_NAME, getBundleSymbolicName());
 		serviceProperties.put(Constants.BUNDLE_SYMBOLICNAME, getBundleSymbolicName());
 		serviceProperties.put(Constants.BUNDLE_VERSION, OsgiBundleUtils.getBundleVersion(bundle));
 	}
 
 	private String getBundleSymbolicName() {
 		return OsgiStringUtils.nullSafeSymbolicName(getBundle());
 	}
 
 	/**
 	 * Creates an OSGi specific resource pattern resolver.
 	 * 
 	 * @return returns an OSGi specific pattern resolver.
 	 */
 	protected ResourcePatternResolver createResourcePatternResolver() {
 		return new OsgiBundleResourcePatternResolver(getBundle());
 	}
 
 	/**
 	 * This implementation supports pattern matching inside the OSGi bundle.
 	 * 
 	 * @see OsgiBundleResourcePatternResolver
 	 */
 	protected ResourcePatternResolver getResourcePatternResolver() {
 		return osgiPatternResolver;
 	}
 
 	// delegate methods to a proper osgi resource loader
 
 	public ClassLoader getClassLoader() {
 		return classLoader;
 	}
 
 	public Resource getResource(String location) {
 		return (osgiPatternResolver != null ? osgiPatternResolver.getResource(location) : null);
 	}
 
 	public Resource[] getResources(String locationPattern) throws IOException {
 		return (osgiPatternResolver != null ? osgiPatternResolver.getResources(locationPattern) : null);
 	}
 
 	public void setClassLoader(ClassLoader classLoader) {
 		this.classLoader = classLoader;
 	}
 
 	protected Resource getResourceByPath(String path) {
 		Assert.notNull(path, "Path is required");
 		return new OsgiBundleResource(this.bundle, path);
 	}
 
 	public void setPublishContextAsService(boolean publishContextAsService) {
 		this.publishContextAsService = publishContextAsService;
 	}
 
 	/**
 	 * Create the class loader that delegates to the underlying OSGi bundle.
 	 * 
 	 * @param bundle
 	 * @return
 	 */
 	private ClassLoader createBundleClassLoader(Bundle bundle) {
 		return ClassLoaderFactory.getBundleClassLoaderFor(bundle);
 	}
 }