Copyright (c) 2004, 2016 IBM Corporation and others.
This program and the accompanying materials
are made available under the terms of the Eclipse Public License 2.0
which accompanies this distribution, and is available at
https://www.eclipse.org/legal/epl-2.0/
SPDX-License-Identifier: EPL-2.0
Contributors:
    IBM Corporation - initial API and implementation
/*******************************************************************************
 * Copyright (c) 2004, 2016 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/

package org.eclipse.osgi.internal.url;

import java.lang.reflect.Method;
import java.net.*;
import java.security.AccessController;
import java.util.*;
import org.eclipse.osgi.framework.log.FrameworkLogEntry;
import org.eclipse.osgi.framework.util.SecureAction;
import org.eclipse.osgi.internal.framework.EquinoxContainer;
import org.eclipse.osgi.internal.location.EquinoxLocations;
import org.eclipse.osgi.internal.messages.Msg;
import org.eclipse.osgi.storage.url.BundleResourceHandler;
import org.eclipse.osgi.util.NLS;
import org.osgi.framework.BundleContext;
import org.osgi.framework.ServiceReference;
import org.osgi.service.url.URLConstants;
import org.osgi.service.url.URLStreamHandlerService;
import org.osgi.util.tracker.ServiceTracker;

This class contains the URL stream handler factory for the OSGi framework.
/**
 * This class contains the URL stream handler factory for the OSGi framework.
 */
public class URLStreamHandlerFactoryImpl extends MultiplexingFactory implements URLStreamHandlerFactory {
	protected static final String URLSTREAMHANDLERCLASS = "org.osgi.service.url.URLStreamHandlerService"; //$NON-NLS-1$
	protected static final String PROTOCOL_HANDLER_PKGS = "java.protocol.handler.pkgs"; //$NON-NLS-1$
	public static final String PROTOCOL_REFERENCE = "reference"; //$NON-NLS-1$
	static final SecureAction secureAction = AccessController.doPrivileged(SecureAction.createSecureAction());

	private ServiceTracker<URLStreamHandlerService, URLStreamHandlerService> handlerTracker;

	private static final List<Class<?>> ignoredClasses = Arrays.asList(new Class<?>[] {MultiplexingURLStreamHandler.class, URLStreamHandlerFactoryImpl.class, URL.class});
	private Map<String, URLStreamHandler> proxies;
	private URLStreamHandlerFactory parentFactory;
	private ThreadLocal<List<String>> creatingProtocols = new ThreadLocal<>();

	
Create the factory.
Params:
context – BundleContext for the system bundle/**
	 * Create the factory.
	 *
	 * @param context BundleContext for the system bundle
	 */
	public URLStreamHandlerFactoryImpl(BundleContext context, EquinoxContainer container) {
		super(context, container);

		proxies = new Hashtable<>(15);
		handlerTracker = new ServiceTracker<>(context, URLSTREAMHANDLERCLASS, null);
		handlerTracker.open();
	}

	private Class<?> getBuiltIn(String protocol, String builtInHandlers) {
		if (builtInHandlers == null)
			return null;
		Class<?> clazz;
		StringTokenizer tok = new StringTokenizer(builtInHandlers, "|"); //$NON-NLS-1$
		while (tok.hasMoreElements()) {
			StringBuilder name = new StringBuilder();
			name.append(tok.nextToken());
			name.append("."); //$NON-NLS-1$
			name.append(protocol);
			name.append(".Handler"); //$NON-NLS-1$
			try {
				clazz = secureAction.loadSystemClass(name.toString());
				if (clazz != null)
					return clazz; //this class exists, it is a built in handler	
			} catch (ClassNotFoundException ex) {
				// keep looking
			}
		}
		return null;
	}

	
Creates a new URLStreamHandler instance for the specified
protocol.
Params:
protocol – The desired protocol
Returns:
a URLStreamHandler for the specific protocol./**
	 * Creates a new URLStreamHandler instance for the specified
	 * protocol.
	 *
	 * @param protocol The desired protocol
	 * @return a URLStreamHandler for the specific protocol.
	 */
	@Override
	public URLStreamHandler createURLStreamHandler(String protocol) {
		// Check if we are recursing
		if (isRecursive(protocol))
			return null;
		try {
			//first check for built in handlers
			String builtInHandlers = secureAction.getProperty(PROTOCOL_HANDLER_PKGS);
			Class<?> clazz = getBuiltIn(protocol, builtInHandlers);
			if (clazz != null)
				return null; // let the VM handle it
			URLStreamHandler result = null;
			if (isMultiplexing()) {
				URLStreamHandler authorized = findAuthorizedURLStreamHandler(protocol);
				if (authorized != null)
					result = new MultiplexingURLStreamHandler(protocol, this, authorized);
			} else {
				result = createInternalURLStreamHandler(protocol);
			}
			// if parent is present do parent lookup
			if (result == null && parentFactory != null)
				result = parentFactory.createURLStreamHandler(protocol);
			return result; //result may be null; let the VM handle it (consider sun.net.protocol.www.*)
		} catch (Throwable t) {
			container.getLogServices().log(URLStreamHandlerFactoryImpl.class.getName(), FrameworkLogEntry.ERROR, "Unexpected error in factory.", t); //$NON-NLS-1$
			return null;
		} finally {
			releaseRecursive(protocol);
		}
	}

	private boolean isRecursive(String protocol) {
		List<String> protocols = creatingProtocols.get();
		if (protocols == null) {
			protocols = new ArrayList<>(1);
			creatingProtocols.set(protocols);
		}
		if (protocols.contains(protocol))
			return true;
		protocols.add(protocol);
		return false;
	}

	private void releaseRecursive(String protocol) {
		List<String> protocols = creatingProtocols.get();
		protocols.remove(protocol);
	}

	private URLStreamHandler getFrameworkHandler(String protocol) {
		if (BundleResourceHandler.OSGI_ENTRY_URL_PROTOCOL.equals(protocol)) {
			return new org.eclipse.osgi.storage.url.bundleentry.Handler(container.getStorage().getModuleContainer(), null);
		} else if (BundleResourceHandler.OSGI_RESOURCE_URL_PROTOCOL.equals(protocol)) {
			return new org.eclipse.osgi.storage.url.bundleresource.Handler(container.getStorage().getModuleContainer(), null);
		} else if (PROTOCOL_REFERENCE.equals(protocol)) {
			return new org.eclipse.osgi.storage.url.reference.Handler(container.getConfiguration().getConfiguration(EquinoxLocations.PROP_INSTALL_AREA));
		}
		return null;
	}

	public URLStreamHandler createInternalURLStreamHandler(String protocol) {
		//internal protocol handlers
		URLStreamHandler frameworkHandler = getFrameworkHandler(protocol);
		if (frameworkHandler != null) {
			return frameworkHandler;
		}

		//Now we check the service registry
		//first check to see if the handler is in the cache
		URLStreamHandlerProxy handler = (URLStreamHandlerProxy) proxies.get(protocol);
		if (handler != null)
			return (handler);
		//look through the service registry for a URLStramHandler registered for this protocol
		ServiceReference<URLStreamHandlerService>[] serviceReferences = handlerTracker.getServiceReferences();
		if (serviceReferences == null)
			return null;
		for (ServiceReference<URLStreamHandlerService> serviceReference : serviceReferences) {
			Object prop = serviceReference.getProperty(URLConstants.URL_HANDLER_PROTOCOL);
			if (prop instanceof String)
				prop = new String[] {(String) prop}; // TODO should this be a warning?
			if (!(prop instanceof String[])) {
				String message = NLS.bind(Msg.URL_HANDLER_INCORRECT_TYPE, new Object[]{URLConstants.URL_HANDLER_PROTOCOL, URLSTREAMHANDLERCLASS, serviceReference.getBundle()});
				container.getLogServices().log(EquinoxContainer.NAME, FrameworkLogEntry.WARNING, message, null);
				continue;
			}
			String[] protocols = (String[]) prop;
			for (String candidateProtocol : protocols) {
				if (candidateProtocol.equals(protocol)) {
					handler = new URLStreamHandlerProxy(protocol, serviceReference, context);
					proxies.put(protocol, handler);
					return (handler);
				}
			}
		}
		return null;
	}

	protected URLStreamHandler findAuthorizedURLStreamHandler(String protocol) {
		Object factory = findAuthorizedFactory(ignoredClasses);
		if (factory == null)
			return null;

		if (factory == this)
			return createInternalURLStreamHandler(protocol);

		try {
			Method createInternalURLStreamHandlerMethod = factory.getClass().getMethod("createInternalURLStreamHandler", new Class[] {String.class}); //$NON-NLS-1$
			return (URLStreamHandler) createInternalURLStreamHandlerMethod.invoke(factory, new Object[] {protocol});
		} catch (Exception e) {
			container.getLogServices().log(URLStreamHandlerFactoryImpl.class.getName(), FrameworkLogEntry.ERROR, "findAuthorizedURLStreamHandler-loop", e); //$NON-NLS-1$
			throw new RuntimeException(e.getMessage(), e);
		}
	}

	@Override
	public Object getParentFactory() {
		return parentFactory;
	}

	@Override
	public void setParentFactory(Object parentFactory) {
		if (this.parentFactory == null) // only allow it to be set once
			this.parentFactory = (URLStreamHandlerFactory) parentFactory;
	}
}