package com.atlassian.plugin.osgi.bridge;
   
   import com.atlassian.plugin.PluginAccessor;
   import com.atlassian.plugin.event.PluginEventManager;
   import com.atlassian.plugin.osgi.bridge.external.PluginRetrievalService;
   import org.eclipse.gemini.blueprint.context.event.OsgiBundleApplicationContextListener;
   import org.osgi.framework.BundleActivator;
   import org.osgi.framework.BundleContext;
   import org.osgi.framework.ServiceReference;
  
  import java.util.Dictionary;
  import java.util.Hashtable;
  
  /**
   * Registers services for bridging Spring events with the plugin event system
   *
   * @since 2.2.0
   */
  public class BridgeActivator implements BundleActivator {
      public void start(BundleContext bundleContext) {
          // We can do this because the plugin event manager is a host component
          PluginEventManager pluginEventManager = getHostComponent(bundleContext, PluginEventManager.class);
  
          // Register the listener for context refreshed and failed events
          bundleContext.registerService(
                  OsgiBundleApplicationContextListener.class.getName(),
                  new SpringOsgiEventBridge(pluginEventManager),
                  null);
  
          // Register the listener for internal application context events like waiting for dependencies
          Dictionary<String, String> dict = new Hashtable<>();
          dict.put("plugin-bridge", "true");
          bundleContext.registerService(
                  OsgiBundleApplicationContextListener.class.getName(),
                  new SpringContextEventBridge(pluginEventManager),
                  dict);
  
          // Register the {@link PluginRetrievalService} service
          PluginAccessor pluginAccessor = getHostComponent(bundleContext, PluginAccessor.class);
          bundleContext.registerService(
                  PluginRetrievalService.class.getName(),
                  new PluginRetrievalServiceFactory(pluginAccessor),
                  null);
      }
  
      private <T> T getHostComponent(BundleContext bundleContext, Class<T> componentClass) {
          ServiceReference ref = bundleContext.getServiceReference(componentClass.getName());
          if (ref == null) {
              throw new IllegalStateException("The " + componentClass.getName() + " service must be exported from the application");
          }
          //noinspection unchecked
          return (T) bundleContext.getService(ref);
      }
  
      public void stop(BundleContext bundleContext) {
      }
  }