// ========================================================================
   // Copyright (c) 2009 Intalio, Inc.
   // ------------------------------------------------------------------------
   // All rights reserved. This program and the accompanying materials
   // are made available under the terms of the Eclipse Public License v1.0
   // and Apache License v2.0 which accompanies this distribution.
   // The Eclipse Public License is available at 
   // http://www.eclipse.org/legal/epl-v10.html
   // The Apache License v2.0 is available at
  // http://www.opensource.org/licenses/apache2.0.php
  // You may elect to redistribute this code under either of these licenses. 
  // ========================================================================
  package org.eclipse.jetty.osgi.boot.utils.internal;
  
  import java.lang.reflect.Field;
  import java.lang.reflect.Method;
  import java.util.List;
  
  import org.eclipse.jetty.osgi.boot.utils.BundleClassLoaderHelper;
  import org.osgi.framework.Bundle;
  
  /**
   * Default implementation of the BundleClassLoaderHelper. Uses introspection to
   * support equinox-3.5 and felix-2.0.0
   */
  public class DefaultBundleClassLoaderHelper implements BundleClassLoaderHelper
  {
  
      private static boolean identifiedOsgiImpl = false;
  
      private static boolean isEquinox = false;
  
      private static boolean isFelix = false;
  
      private static void init(Bundle bundle)
      {
          identifiedOsgiImpl = true;
          try
          {
              isEquinox = bundle.getClass().getClassLoader().loadClass("org.eclipse.osgi.framework.internal.core.BundleHost") != null;
          }
          catch (Throwable t)
          {
              isEquinox = false;
          }
          if (!isEquinox)
          {
              try
              {
                  isFelix = bundle.getClass().getClassLoader().loadClass("org.apache.felix.framework.BundleImpl") != null;
              }
              catch (Throwable t2)
              {
                  isFelix = false;
              }
          }
      }
  
      /**
       * Assuming the bundle is started.
       * 
       * @param bundle
       * @return classloader object
       */
      public ClassLoader getBundleClassLoader(Bundle bundle)
      {
          String bundleActivator = (String) bundle.getHeaders().get("Bundle-Activator");
          if (bundleActivator == null)
          {
              bundleActivator = (String) bundle.getHeaders().get("Jetty-ClassInBundle");
          }
          if (bundleActivator != null)
          {
              try
              {
                  return bundle.loadClass(bundleActivator).getClassLoader();
              }
              catch (ClassNotFoundException e)
              {
                  // should not happen as we are called if the bundle is started
                  // anyways.
                  e.printStackTrace();
              }
          }
          // resort to introspection
          if (!identifiedOsgiImpl)
          {
              init(bundle);
          }
          if (isEquinox)
          {
              return internalGetEquinoxBundleClassLoader(bundle);
          }
          else if (isFelix) { return internalGetFelixBundleClassLoader(bundle); }
          return null;
      }
  
      private static Method Equinox_BundleHost_getBundleLoader_method;
  
     private static Method Equinox_BundleLoader_createClassLoader_method;
 
     private static ClassLoader internalGetEquinoxBundleClassLoader(Bundle bundle)
     {
         // assume equinox:
         try
         {
             if (Equinox_BundleHost_getBundleLoader_method == null)
             {
                 Equinox_BundleHost_getBundleLoader_method = 
                     bundle.getClass().getClassLoader().loadClass("org.eclipse.osgi.framework.internal.core.BundleHost").getDeclaredMethod("getBundleLoader", new Class[] {});
                 Equinox_BundleHost_getBundleLoader_method.setAccessible(true);
             }
             Object bundleLoader = Equinox_BundleHost_getBundleLoader_method.invoke(bundle, new Object[] {});
             if (Equinox_BundleLoader_createClassLoader_method == null && bundleLoader != null)
             {
                 Equinox_BundleLoader_createClassLoader_method = 
                     bundleLoader.getClass().getClassLoader().loadClass("org.eclipse.osgi.internal.loader.BundleLoader").getDeclaredMethod("createClassLoader", new Class[] {});
                 Equinox_BundleLoader_createClassLoader_method.setAccessible(true);
             }
             return (ClassLoader) Equinox_BundleLoader_createClassLoader_method.invoke(bundleLoader, new Object[] {});
         }
         catch (Throwable t)
         {
             t.printStackTrace();
         }
         return null;
     }
 
     private static Field Felix_BundleImpl_m_modules_field;
 
     private static Field Felix_ModuleImpl_m_classLoader_field;
 
     private static ClassLoader internalGetFelixBundleClassLoader(Bundle bundle)
     {
         // assume felix:
         try
         {
             // now get the current module from the bundle.
             // and return the private field m_classLoader of ModuleImpl
             if (Felix_BundleImpl_m_modules_field == null)
             {
                 Felix_BundleImpl_m_modules_field = bundle.getClass().getClassLoader().loadClass("org.apache.felix.framework.BundleImpl").getDeclaredField("m_modules");
                 Felix_BundleImpl_m_modules_field.setAccessible(true);
             }
 
             // Figure out which version of the modules is exported
             Object currentModuleImpl;
             try
             {
                 Object[] moduleArray = (Object[]) Felix_BundleImpl_m_modules_field.get(bundle);
                 currentModuleImpl = moduleArray[moduleArray.length - 1];
             }
             catch (Throwable t2)
             {
                 @SuppressWarnings("unchecked")
                 List<Object> moduleArray = (List<Object>) Felix_BundleImpl_m_modules_field.get(bundle);
                 currentModuleImpl = moduleArray.get(moduleArray.size() - 1);
             }
 
             if (Felix_ModuleImpl_m_classLoader_field == null && currentModuleImpl != null)
             {
                 Felix_ModuleImpl_m_classLoader_field = bundle.getClass().getClassLoader().loadClass("org.apache.felix.framework.ModuleImpl").getDeclaredField("m_classLoader");
                 Felix_ModuleImpl_m_classLoader_field.setAccessible(true);
             }
             // first make sure that the classloader is ready:
             // the m_classLoader field must be initialized by the
             // ModuleImpl.getClassLoader() private method.
             ClassLoader cl = (ClassLoader) Felix_ModuleImpl_m_classLoader_field.get(currentModuleImpl);
             if (cl == null)
             {
                 // looks like it was not ready:
                 // the m_classLoader field must be initialized by the
                 // ModuleImpl.getClassLoader() private method.
                 // this call will do that.
                 bundle.loadClass("java.lang.Object");
                 cl = (ClassLoader) Felix_ModuleImpl_m_classLoader_field.get(currentModuleImpl);
                 return cl;
             }
             else
             {
                 return cl;
             }
         }
         catch (Throwable t)
         {
             t.printStackTrace();
         }
         return null;
     }
 
 }