/*
 * $Id$
 *
 * Copyright (C) 2003-2015 JNode.org
 *
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published
 * by the Free Software Foundation; either version 2.1 of the License, or
 * (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful, but 
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 
 * License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; If not, write to the Free Software Foundation, Inc., 
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
 
package org.jnode.protocol;

import java.net.URL;
import java.net.URLStreamHandler;
import java.net.URLStreamHandlerFactory;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.HashMap;

import org.jnode.bootlog.BootLogInstance;
import org.jnode.plugin.ConfigurationElement;
import org.jnode.plugin.Extension;
import org.jnode.plugin.ExtensionPoint;
import org.jnode.plugin.ExtensionPointListener;
import org.jnode.plugin.Plugin;
import org.jnode.plugin.PluginDescriptor;
import org.jnode.plugin.PluginException;

/**
 * Plugin that installs itself as an URL Handler Factory.
 * <p/>
 * This plugin has a "handlers" extension point which should be used
 * to register protocol handlers.
 *
 * @author Ewout Prangsma (epr@users.sourceforge.net)
 */
public class ProtocolHandlerFactoryPlugin extends Plugin implements
    URLStreamHandlerFactory, ExtensionPointListener {

    private final ExtensionPoint handlersEp;
    private final HashMap<String, Class<? extends URLStreamHandler>> handlerClasses =
        new HashMap<String, Class<? extends URLStreamHandler>>();

    /**
     * @param descriptor
     */
    public ProtocolHandlerFactoryPlugin(PluginDescriptor descriptor) {
        super(descriptor);
        this.handlersEp = descriptor.getExtensionPoint("handlers");
        reloadHandlers();
    }

    /**
     * @see org.jnode.plugin.Plugin#startPlugin()
     */
    protected void startPlugin() throws PluginException {
        handlersEp.addListener(this);
        try {
            setHandlerFactory(this);
        } catch (SecurityException ex) {
            BootLogInstance.get().error("Cannot set URL Handler Factory");
        }
    }

    /**
     * @see org.jnode.plugin.Plugin#stopPlugin()
     */
    protected void stopPlugin() throws PluginException {
        handlersEp.removeListener(this);
        try {
            setHandlerFactory(null);
        } catch (SecurityException ex) {
            BootLogInstance.get().error("Cannot reset URL Handler Factory");
        }
    }

    /**
     * @see java.net.URLStreamHandlerFactory#createURLStreamHandler(java.lang.String)
     */
    public synchronized URLStreamHandler createURLStreamHandler(String protocol) {
        final Class<? extends URLStreamHandler> cls = handlerClasses.get(protocol);
        if (cls != null) {
            try {
                return (URLStreamHandler) cls.newInstance();
            } catch (InstantiationException ex) {
                BootLogInstance.get().error("Cannot instantiate " + cls.getName());
            } catch (IllegalAccessException ex) {
                BootLogInstance.get().error("Illegal access to " + cls.getName());
            }
        }
        return null;
    }

    /**
     * @see org.jnode.plugin.ExtensionPointListener#extensionAdded(org.jnode.plugin.ExtensionPoint,
     * org.jnode.plugin.Extension)
     */
    public void extensionAdded(ExtensionPoint point, Extension extension) {
        reloadHandlers();
    }

    /**
     * @see org.jnode.plugin.ExtensionPointListener#extensionRemoved(org.jnode.plugin.ExtensionPoint,
     * org.jnode.plugin.Extension)
     */
    public void extensionRemoved(ExtensionPoint point, Extension extension) {
        reloadHandlers();
    }

    private void setHandlerFactory(final URLStreamHandlerFactory factory) {
        AccessController.doPrivileged(new PrivilegedAction() {

            public Object run() {
                URL.setURLStreamHandlerFactory(factory);
                return null;
            }
        });
    }

    private synchronized void reloadHandlers() {
        handlerClasses.clear();
        final Extension[] exts = handlersEp.getExtensions();
        final int count = exts.length;
        for (int i = 0; i < count; i++) {
            loadHandlers(exts[i]);
        }
    }

    private void loadHandlers(Extension ext) {
        final ConfigurationElement[] elems = ext.getConfigurationElements();
        final int count = elems.length;
        final ClassLoader cl = ext.getDeclaringPluginDescriptor().getPluginClassLoader();
        for (int i = 0; i < count; i++) {
            final ConfigurationElement elem = elems[i];
            if (elem.getName().equals("handler")) {
                final String protocol = elem.getAttribute("protocol");
                final String className = elem.getAttribute("class");
                if ((protocol != null) && (className != null)) {
                    try {
                        final Class<? extends URLStreamHandler> cls = cl.loadClass(className);
                        handlerClasses.put(protocol, cls);
                    } catch (ClassNotFoundException ex) {
                        BootLogInstance.get().error("Cannot load protocol handler class " + className);
                    }
                }
            }
        }
    }
}