/*
 File: CyMain.java

 Copyright (c) 2010, The Cytoscape Consortium (www.cytoscape.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
 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.  The software and
 documentation provided hereunder is on an "as is" basis, and the
 Institute for Systems Biology and the Whitehead Institute
 have no obligations to provide maintenance, support,
 updates, enhancements or modifications.  In no event shall the
 Institute for Systems Biology and the Whitehead Institute
 be liable to any party for direct, indirect, special,
 incidental or consequential damages, including lost profits, arising
 out of the use of this software and its documentation, even if the
 Institute for Systems Biology and the Whitehead Institute
 have been advised of the possibility of such damage.  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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
 */
package cytoscape;


import cytoscape.logger.CyLogger;


/**
 *  A class that determines various components of the JVM version.
 *  Please <a href="http://java.sun.com/j2se/versioning_naming.html">see</a> for details.
 */
class JavaVersion {
	private static JavaVersion theJavaVersion;

	private final static CyLogger logger = CyLogger.getLogger(JavaVersion.class);

	private int major;
	private int minor;
	private int maintenanceLevel;
	private int update;

	private JavaVersion() {
		final String javaVersion = System.getProperty("java.version");

		int nonDigitPos = 0;
		while (Character.isDigit(javaVersion.charAt(nonDigitPos)))
			++nonDigitPos;
		try {
			major = Integer.parseInt(javaVersion.substring(0, nonDigitPos));
		} catch (final NumberFormatException e) {
			logger.error("Can't determine Java major version number from \"" + javaVersion + "\"!");
			major = 0;
		}

		++nonDigitPos;
		int intStart = nonDigitPos;
		while (Character.isDigit(javaVersion.charAt(nonDigitPos)))
			++nonDigitPos;
		try {
			minor = Integer.parseInt(javaVersion.substring(intStart, nonDigitPos));
		} catch (final NumberFormatException e) {
			logger.error("Can't determine Java major version number from \"" + javaVersion + "\"!");
			minor = 0;
		}

		++nonDigitPos;
		intStart = nonDigitPos;
		while (nonDigitPos < javaVersion.length() && Character.isDigit(javaVersion.charAt(nonDigitPos)))
			++nonDigitPos;
		try {
			maintenanceLevel = Integer.parseInt(javaVersion.substring(intStart, nonDigitPos));
		} catch (final NumberFormatException e) {
			logger.error("Can't determine Java maintenance level from \"" + javaVersion + "\"!");
			maintenanceLevel = 0;
		}

		++nonDigitPos;
		intStart = nonDigitPos;
		while (nonDigitPos < javaVersion.length() && Character.isDigit(javaVersion.charAt(nonDigitPos)))
			++nonDigitPos;
		if (nonDigitPos > javaVersion.length())
			update = 0;
		else {
			try {
				update = Integer.parseInt(javaVersion.substring(intStart, nonDigitPos));
			} catch (final NumberFormatException e) {
				logger.error("Can't determine Java update version number from \"" + javaVersion + "\"!");
				update = 0;
			}
		}
	}

	/**
	 *  Factory method returning the singleton.
	 */
	static synchronized JavaVersion getJavaVersion() {
		if (theJavaVersion == null)
			theJavaVersion = new JavaVersion();
		return theJavaVersion;
	}

	/**
	 *  We override clone() to prevent any callers from circumventing our singleton policy.
	 */
	@Override public Object clone() throws CloneNotSupportedException {
		throw new CloneNotSupportedException(); // That'll teach 'em!
	}

	int getMajor() { return major; }
	int getMinor() { return minor; }
	int getMaintenanceLevel() { return maintenanceLevel; }
	int getUpdate() { return update; }
}