/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.activiti.osgi.blueprint;

import java.io.IOException;
import java.net.URL;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Enumeration;

import org.osgi.framework.Bundle;

/**
 * A ClassLoader delegating to a given OSGi bundle.
 * 
 */
public class BundleDelegatingClassLoader extends ClassLoader {

  private final Bundle bundle;
  private final ClassLoader classLoader;

  public BundleDelegatingClassLoader(Bundle bundle) {
    this(bundle, null);
  }

  public BundleDelegatingClassLoader(Bundle bundle, ClassLoader classLoader) {
    this.bundle = bundle;
    this.classLoader = classLoader;
  }

  @SuppressWarnings({ "unchecked", "rawtypes" })
  protected Class findClass(final String name) throws ClassNotFoundException {
    try {
      return AccessController
          .doPrivileged(new PrivilegedExceptionAction<Class<?>>() {
            public Class<?> run() throws ClassNotFoundException {
              return bundle.loadClass(name);
            }

          });
    } catch (PrivilegedActionException e) {
      Exception cause = e.getException();

      if (cause instanceof ClassNotFoundException)
        throw (ClassNotFoundException) cause;
      else
        throw (RuntimeException) cause;
    }
  }

  protected URL findResource(final String name) {
    URL resource = AccessController.doPrivileged(new PrivilegedAction<URL>() {
      public URL run() {
        return bundle.getResource(name);
      }
    });
    if (classLoader != null && resource == null) {
      resource = classLoader.getResource(name);
    }
    return resource;
  }

  @SuppressWarnings({ "rawtypes", "unchecked" })
  protected Enumeration findResources(final String name) throws IOException {
    Enumeration<URL> urls;
    try {
      urls = AccessController
          .doPrivileged(new PrivilegedExceptionAction<Enumeration<URL>>() {

            public Enumeration<URL> run() throws IOException {
              return (Enumeration<URL>) bundle.getResources(name);
            }

          });
    } catch (PrivilegedActionException e) {
      Exception cause = e.getException();

      if (cause instanceof IOException)
        throw (IOException) cause;
      else
        throw (RuntimeException) cause;
    }

    if (urls == null) {
      urls = Collections.enumeration(new ArrayList<URL>());
    }

    return urls;
  }

  @SuppressWarnings({ "rawtypes", "unchecked" })
  protected Class loadClass(String name, boolean resolve)
      throws ClassNotFoundException {
    Class clazz;
    try {
      clazz = findClass(name);
    } catch (ClassNotFoundException cnfe) {
      if (classLoader != null) {
        try {
          clazz = classLoader.loadClass(name);
        } catch (ClassNotFoundException e) {
          throw new ClassNotFoundException(name + " from bundle "
              + bundle.getBundleId() + " (" + bundle.getSymbolicName() + ")",
              cnfe);
        }
      } else {
        throw new ClassNotFoundException(name + " from bundle "
            + bundle.getBundleId() + " (" + bundle.getSymbolicName() + ")",
            cnfe);
      }
    }
    if (resolve) {
      resolveClass(clazz);
    }
    return clazz;
  }

  public Bundle getBundle() {
    return bundle;
  }
}