/*
 * 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;
	}
}