/*
    * Copyright (C) 2007-2012 Argeo 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.argeo.eclipse.spring;
  
  import org.argeo.eclipse.ui.EclipseUiException;
  import org.eclipse.core.runtime.CoreException;
  import org.eclipse.core.runtime.IConfigurationElement;
  import org.eclipse.core.runtime.IExecutableExtension;
  import org.eclipse.core.runtime.IExecutableExtensionFactory;
  import org.eclipse.core.runtime.IExtension;
  import org.springframework.context.ApplicationContext;
  
  /**
   * The Spring Extension Factory builds a bridge between the Eclipse Extension
   * Registry and the Spring Framework (especially Spring Dynamic Modules).
   * 
   * It allows you to define your extension as a spring bean within the spring
   * application context of your bundle. If you would like to use this bean as an
   * instance of an extension (an Eclipse RCP view, for example) you define the
   * extension with this spring extension factory as the class to be created.
   * 
   * To let the spring extension factory pick the right bean from your application
   * context you need to set the bean id to the same value as the id of the view
   * within the view definition, for example. This is important if your extension
   * definition contains more than one element, where each element has its own id.
   * 
   * If the extension definition elements themselves have no id attribute the
   * spring extension factory uses the id of the extension itself to identify the
   * bean.
   * 
   * original code from: <a href=
   * "http://martinlippert.blogspot.com/2008/10/new-version-of-spring-extension-factory.html"
   * >Blog entry</a>
   * 
   * @author Martin Lippert
   * @author mbaudier
   */
  public class SpringExtensionFactory implements IExecutableExtensionFactory,
  		IExecutableExtension {
  
  	private Object bean;
  
  	public Object create() throws CoreException {
  		if (bean == null)
  			throw new EclipseUiException("No underlying bean for extension");
  		return bean;
  	}
  
  	public void setInitializationData(IConfigurationElement config,
  			String propertyName, Object data) throws CoreException {
  		String bundleSymbolicName = config.getContributor().getName();
  		ApplicationContext applicationContext = ApplicationContextTracker
  				.getApplicationContext(bundleSymbolicName);
  		if (applicationContext == null)
  			throw new EclipseUiException(
  					"Cannot find application context for bundle "
  							+ bundleSymbolicName);
  
  		String beanName = getBeanName(data, config);
  		if (beanName == null)
  			throw new EclipseUiException("Cannot find bean name for extension "
  					+ config);
  
  		if (!applicationContext.containsBean(beanName)) {
  			if (beanName.startsWith(bundleSymbolicName))
  				beanName = beanName.substring(bundleSymbolicName.length() + 1);
  		}
  
  		if (!applicationContext.containsBean(beanName))
  			throw new EclipseUiException("No bean with name '" + beanName + "'");
  
  		this.bean = applicationContext.getBean(beanName);
  		if (this.bean instanceof IExecutableExtension) {
  			((IExecutableExtension) this.bean).setInitializationData(config,
  					propertyName, data);
  		}
  	}
  
  	private String getBeanName(Object data, IConfigurationElement config) {
  
  		// try the specific bean id the extension defines
  		if (data != null && data.toString().length() > 0) {
  			return data.toString();
  		}
  
  		// try the id of the config element
 		if (config.getAttribute("id") != null) {
 			return config.getAttribute("id");
 		}
 
 		// try the id of the extension element itself
 		if (config.getParent() != null
 				&& config.getParent() instanceof IExtension) {
 			IExtension extensionDefinition = (IExtension) config.getParent();
 			return extensionDefinition.getSimpleIdentifier();
 		}
 
 		return null;
 	}
 }