/*
 * Copyright 2005-2008 Les Hazlewood and the origional authors
 *
 * 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.jsecurity.util;

/**
 * Internal helper class used to find the Java/JDK version
 * that JSecurity is operating within, to allow for automatically
 * adapting to the present platform's capabilities.
 *
 * <p>Note that JSecurity does not support 1.2 or earlier JVMs - only 1.3 and later.
 *
 * <p><em>This class was borrowed and heavily based upon a nearly identical version found in
 * the <a href="http://www.springframework.org/">Spring Framework</a>, with minor modifications.
 * The original author names and copyright (Apache 2.0) has been left in place.  A special
 * thanks to Rod Johnson, Juergen Hoeller, and Rick Evans for making this available.</em>
 *
 * @since 0.2
 * 
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @author Rick Evans
 * @author Les Hazlewood
 */
public abstract class JavaEnvironment {

    //utilized in JSecurity environment-specific support checks:
    private static final String EHCACHE_VALID_CLASS_NAME = "net.sf.ehcache.CacheManager";


    /**
	 * Constant identifying the 1.3.x JVM (JDK 1.3).
	 */
	public static final int JAVA_13 = 0;

	/**
	 * Constant identifying the 1.4.x JVM (J2SE 1.4).
	 */
	public static final int JAVA_14 = 1;

	/**
	 * Constant identifying the 1.5 JVM (Java 5).
	 */
	public static final int JAVA_15 = 2;

	/**
	 * Constant identifying the 1.6 JVM (Java 6).
	 */
	public static final int JAVA_16 = 3;

	/**
	 * Constant identifying the 1.7 JVM.
	 */
	public static final int JAVA_17 = 4;


	private static final String version;

	private static final int majorVersion;

	static {
		version = System.getProperty("java.version");
		// version String should look like "1.4.2_10"
		if ( version.indexOf("1.7.") != -1) {
			majorVersion = JAVA_17;
		}
		else if ( version.indexOf("1.6.") != -1) {
			majorVersion = JAVA_16;
		}
		else if ( version.indexOf("1.5.") != -1) {
			majorVersion = JAVA_15;
		}
		else if ( version.indexOf("1.4.") != -1) {
			majorVersion = JAVA_14;
		}
		else {
			// else leave 1.3 as default (it's either 1.3 or unknown)
			majorVersion = JAVA_13;
		}
	}


	/**
	 * Return the full Java version string, as returned by
	 * <code>System.getProperty("java.version")</code>.
	 * @return the full Java version string
	 * @see System#getProperty(String)
	 */
	public static String getVersion() {
		return version;
	}

	/**
	 * Get the major version code. This means we can do things like
	 * <code>if (getMajorVersion() < JAVA_14)</code>.
	 * @return a code comparable to the JAVA_XX codes in this class
	 * @see #JAVA_13
	 * @see #JAVA_14
	 * @see #JAVA_15
	 * @see #JAVA_16
	 * @see #JAVA_17
	 */
	public static int getMajorVersion() {
		return majorVersion;
	}

	/**
	 * Convenience method to determine if the current JVM is at least Java 1.4.
	 * @return <code>true</code> if the current JVM is at least Java 1.4
	 * @see #getMajorVersion()
	 * @see #JAVA_14
	 * @see #JAVA_15
	 * @see #JAVA_16
	 * @see #JAVA_17
	 */
	public static boolean isAtLeastVersion14() {
		return getMajorVersion() >= JAVA_14;
	}

	/**
	 * Convenience method to determine if the current JVM is at least
	 * Java 1.5 (Java 5).
	 * @return <code>true</code> if the current JVM is at least Java 1.5
	 * @see #getMajorVersion()
	 * @see #JAVA_15
	 * @see #JAVA_16
	 * @see #JAVA_17
	 */
	public static boolean isAtLeastVersion15() {
		return getMajorVersion() >= JAVA_15;
	}

    /**
     * Returns if Ehcache is in the classpath and available to be used (e.g. when creating a
     * {@link org.jsecurity.cache.CacheManager CacheManager}.
     * @return true if Ehcache is in the classpath and can be used for caching, false otherwise.
     */
    public static boolean isEhcacheAvailable() {
        return ClassUtils.isAvailable( EHCACHE_VALID_CLASS_NAME );
    }

}