/*
 * Copyright 2012 Christopher Pheby
 * 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.jadira.scanner.core.utils.reflection;

/**
 * Utility methods related to {@link ClassLoader} resolution and the like
 */
public final class ClassLoaderUtils {

	private ClassLoaderUtils() {
	}

	/**
	 * Gets {@link ClassLoader} for the current thread
	 * @param classLoaders ClassLoaders to be used if specified
	 * @return The ClassLoaders, either those specified, or discovered
	 * ClassLoaders for the current thread
	 */
	public static ClassLoader[] getClassLoaders(ClassLoader... classLoaders) {

		if (classLoaders != null && classLoaders.length > 0) {
			return classLoaders;
		}

		final ClassLoader ctxClassLoader = Thread.currentThread()
				.getContextClassLoader();
		final ClassLoader staticClassLoader = ClassLoaderUtils.class
				.getClassLoader();

		if (ctxClassLoader == null) {
			if (staticClassLoader == null) {
				return new ClassLoader[] {};
			} else {
				return new ClassLoader[] { staticClassLoader };
			}
		} else {
			if (staticClassLoader == null) {
				return new ClassLoader[] { ctxClassLoader };
			} else {
				return new ClassLoader[] { ctxClassLoader, staticClassLoader };
			}
		}
	}

	/**
	 * Attempts to instantiate the named class, using each of the specified
	 * ClassLoaders in turn or Class.forName if these do not work
	 * @param name The class name
	 * @param classLoaders ClassLoaders to be used
	 * @return The Class instance
	 * @throws ClassNotFoundException If the class cannot be found
	 */
	public static Class<?> classForName(String name,
			ClassLoader... classLoaders) throws ClassNotFoundException {

		ClassLoader[] cls = getClassLoaders(classLoaders);

		for (ClassLoader cl : cls) {
			try {
				if (cl != null) {
					return cl.loadClass(name);
				}
			} catch (ClassNotFoundException e) {
				// Ignore
			}
		}
		// Try using Class.forName()
		return Class.forName(name);
	}
}