/*
 * $Header: /cvshome/build/org.osgi.framework/src/org/osgi/framework/FrameworkUtil.java,v 1.10 2007/02/21 16:49:05 hargrave Exp $
 * 
 * Copyright (c) OSGi Alliance (2005, 2007). All Rights Reserved.
 * 
 * Licensed 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.osgi.framework;

import java.lang.reflect.*;
import java.security.AccessController;
import java.security.PrivilegedAction;

/**
 * Framework Utility class.
 * 
 * <p>
 * This class contains utility methods which access Framework functions that may
 * be useful to bundles.
 * 
 * @since 1.3
 * @ThreadSafe
 * @version $Revision: 1.10 $
 */
public class FrameworkUtil {
	/*
	 * NOTE: A framework implementor may also choose to replace this class in
	 * their distribution with a class that directly interfaces with the
	 * framework implementation.
	 */

	/*
	 * This class will load the FrameworkUtil class in the package named by the
	 * org.osgi.vendor.framework package. For each instance of this class, an
	 * instance of the vendor FrameworkUtil class will be created and this class
	 * will delegate method calls to the vendor FrameworkUtil instance.
	 */

	private static class ImplHolder implements PrivilegedAction<Method> {
		private static final String	packageProperty	= "org.osgi.vendor.framework";
		
		/*
		 * This is the delegate method used by createFilter.
		 */
		static final Method	createFilter;
		
		static {
			createFilter = AccessController.doPrivileged(new ImplHolder());
		}
		
		private ImplHolder() {
		}

		public Method run() {
			String packageName = System
			.getProperty(packageProperty);
			if (packageName == null) {
				throw new NoClassDefFoundError(packageProperty
						+ " property not set");
			}
			
			Class<?> delegateClass;
			try {
				delegateClass = Class.forName(packageName
						+ ".FrameworkUtil");
			}
			catch (ClassNotFoundException e) {
				throw new NoClassDefFoundError(e.toString());
			}
			
			Method result;
			try {
				result = delegateClass.getMethod("createFilter",
						new Class[] {String.class});
			}
			catch (NoSuchMethodException e) {
				throw new NoSuchMethodError(e.toString());
			}
			
			if (!Modifier.isStatic(result.getModifiers())) {
				throw new NoSuchMethodError(
				"createFilter method must be static");
			}
			
			return result;
		}
	}

	
	/**
	 * FrameworkUtil objects may not be constructed. 
	 */
	private FrameworkUtil() {}
	
	/**
	 * Creates a <code>Filter</code> object. This <code>Filter</code> object
	 * may be used to match a <code>ServiceReference</code> object or a
	 * <code>Dictionary</code> object.
	 * 
	 * <p>
	 * If the filter cannot be parsed, an {@link InvalidSyntaxException} will be
	 * thrown with a human readable message where the filter became unparsable.
	 * 
	 * @param filter The filter string.
	 * @return A <code>Filter</code> object encapsulating the filter string.
	 * @throws InvalidSyntaxException If <code>filter</code> contains an
	 *         invalid filter string that cannot be parsed.
	 * @throws NullPointerException If <code>filter</code> is null.
	 * 
	 * @see Filter
	 */
	public static Filter createFilter(String filter)
			throws InvalidSyntaxException {
		try {
			try {
				return (Filter) ImplHolder.createFilter
						.invoke(null, new Object[] {filter});
			}
			catch (InvocationTargetException e) {
				throw e.getTargetException();
			}
		}
		catch (InvalidSyntaxException e) {
			throw e;
		}
		catch (Error e) {
			throw e;
		}
		catch (RuntimeException e) {
			throw e;
		}
		catch (Throwable e) {
			throw new RuntimeException(e.toString());
		}
	}
}
