/*******************************************************************************
 * Copyright (c) 2003, 2004 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * Contributors:
 * IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.wst.common.internal.emf.utilities;

import org.eclipse.jem.util.logger.proxy.Logger;


/**
 * <code>Assert</code> is useful for for embedding runtime sanity checks in code. The predicate
 * methods all test a condition and throw some type of unchecked exception if the condition does not
 * hold.
 * <p>
 * Assertion failure exceptions, like most runtime exceptions, are thrown when something is
 * misbehaving. Assertion failures are invariably unspecified behavior; consequently, clients should
 * never rely on these being thrown (and certainly should not being catching them specifically).
 * </p>
 */
// This class was, originally, copied directly from com.ibm.itp.common.
// It was copied to our own package just to minimize minor dependencies
// on other packages and internal APIs.
public final class Assert {
	/* This class is not intended to be instantiated. */

	private Assert() {
	}

	/**
	 * Asserts that an argument is legal. If the given boolean is not <code>true</code>, an
	 * <code>IllegalArgumentException</code> is thrown.
	 * 
	 * @param expression
	 *            the outcode of the check
	 * @return <code>true</code> if the check passes (does not return if the check fails)
	 * @exception IllegalArgumentException
	 *                if the legality test failed
	 */
	public static boolean isLegal(boolean expression) {
		return isLegal(expression, "");//$NON-NLS-1$
	}

	/**
	 * Asserts that an argument is legal. If the given boolean is not <code>true</code>, an
	 * <code>IllegalArgumentException</code> is thrown. The given message is included in that
	 * exception, to aid debugging.
	 * 
	 * @param expression
	 *            the outcode of the check
	 * @param message
	 *            the message to include in the exception
	 * @return <code>true</code> if the check passes (does not return if the check fails)
	 * @exception IllegalArgumentException
	 *                if the legality test failed
	 */
	public static boolean isLegal(boolean expression, String message) {
		if (!expression)
			throw new IllegalArgumentException();
		return expression;
	}

	/**
	 * Asserts that the given object is not <code>null</code>. If this is not the case, some kind
	 * of unchecked exception is thrown.
	 * 
	 * @param object
	 *            the value to test
	 * @exception IllegalArgumentException
	 *                if the object is <code>null</code>
	 */
	public static void isNotNull(Object object) {
		isNotNull(object, "");//$NON-NLS-1$
	}

	/**
	 * Asserts that the given object is not <code>null</code>. If this is not the case, some kind
	 * of unchecked exception is thrown. The given message is included in that exception, to aid
	 * debugging.
	 * 
	 * @param object
	 *            the value to test
	 * @param message
	 *            the message to include in the exception
	 * @exception IllegalArgumentException
	 *                if the object is <code>null</code>
	 */
	public static void isNotNull(Object object, String message) {
		if (object == null) {
			Logger.getLogger().logError("null_argument: " + message);//$NON-NLS-1$
			throw new AssertionFailedException();
		}
	}

	/**
	 * Asserts that the given boolean is <code>true</code>. If this is not the case, some kind of
	 * unchecked exception is thrown.
	 * 
	 * @param expression
	 *            the outcode of the check
	 * @return <code>true</code> if the check passes (does not return if the check fails)
	 */
	public static boolean isTrue(boolean expression) {
		return isTrue(expression, "");//$NON-NLS-1$
	}

	/**
	 * Asserts that the given boolean is <code>true</code>. If this is not the case, some kind of
	 * unchecked exception is thrown. The given message is included in that exception, to aid
	 * debugging.
	 * 
	 * @param expression
	 *            the outcode of the check
	 * @param message
	 *            the message to include in the exception
	 * @return <code>true</code> if the check passes (does not return if the check fails)
	 */
	public static boolean isTrue(boolean expression, String message) {
		if (!expression) {
			Logger.getLogger().logError("assertion failed: " + message);//$NON-NLS-1$
			throw new AssertionFailedException();
		}
		return expression;
	}
}