/*
 * Copyright IBM Corp. and others 2018
 *
 * 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/
 * or the Apache License, Version 2.0 which accompanies this distribution and
 * is available at https://www.apache.org/licenses/LICENSE-2.0.
 *
 * This Source Code may also be made available under the following
 * Secondary Licenses when the conditions for such availability set
 * forth in the Eclipse Public License, v. 2.0 are satisfied: GNU
 * General Public License, version 2 with the GNU Classpath
 * Exception [1] and GNU General Public License, version 2 with the
 * OpenJDK Assembly Exception [2].
 *
 * [1] https://www.gnu.org/software/classpath/license.html
 * [2] https://openjdk.org/legal/assembly-exception.html
 *
 * SPDX-License-Identifier: EPL-2.0 OR Apache-2.0 OR GPL-2.0-only WITH Classpath-exception-2.0 OR GPL-2.0-only WITH OpenJDK-assembly-exception-1.0
 */
package org.openj9.test.util;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

/**
 * Utility class to check the Java version.
 * Checks for the Runtime.Version and uses that if available (JDK9+)
 * otherwise defaults to identifying the JDK as JDK8.
 */
public final class VersionCheck {

	private static Integer major;

	/**
	 * Get the Major version for the running JVM
	 * 
	 * @return The JDK major version, defaults to 8 if not available
	 */
	public static int major() {
		if (major == null) {
			try {
				Method versionMethod = Runtime.class.getMethod("version");
				Object versionInstance = versionMethod.invoke(null);
				Method majorMethod = versionInstance.getClass().getMethod("major");

				major = (Integer) majorMethod.invoke(versionInstance);
			} catch (NoSuchMethodException e) {
				// expected for Java 8
				major = Integer.valueOf(8);
			} catch (SecurityException | IllegalAccessException | InvocationTargetException e) {
				throw new RuntimeException(e);
			}
		}
		return major.intValue();
	}

	/* Get the highest available class file version for this JDK.
	 *
	 * @return The highest available class file version
	 */
	public static int classFile() {
		return major() + 44;
	}

}
