/*******************************************************************************
 * Copyright (c) 2000, 2006 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.jdt.internal.corext;

import org.eclipse.jdt.internal.corext.refactoring.RefactoringCoreMessages;

/**
 * <code>Assert</code> is useful for for embedding runtime sanity checks
 * in code. The static 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 (or not thrown). <b>If you find yourself in the
 * position where you need to catch an assertion failure, you have most 
 * certainly written your program incorrectly.</b>
 * </p>
 * <p>
 * Note that an <code>assert</code> statement is slated to be added to the
 * Java language in JDK 1.4, rending this class obsolete.
 * </p>
 * @deprecated Use {@link org.eclipse.core.runtime.Assert} instead.
 */
public final class Assert {

	/**
	 * <code>AssertionFailedException</code> is a runtime exception thrown
	 * by some of the methods in <code>Assert</code>.
	 * <p>
	 * This class is not declared public to prevent some misuses; programs that catch 
	 * or otherwise depend on assertion failures are susceptible to unexpected
	 * breakage when assertions in the code are added or removed.
	 * </p>
	 */
	private static class AssertionFailedException extends RuntimeException {
		/** This class is not intended to be serialized. */
		private static final long serialVersionUID= 1L;

		/**
		 * Constructs a new exception.
		 */
		public AssertionFailedException() {
		}

		/**
		 * Constructs a new exception with the given message.
		 * @param detail the detail message
		 */
		public AssertionFailedException(String detail) {
			super(detail);
		}
	}

	/* This class is not intended to be instantiated. */
	private Assert() {
	}

	/**
	 * Asserts that the given object is not <code>null</code>. If this
	 * is not the case, some kind of unchecked exception is thrown.
	 * <p>
	 * As a general rule, parameters passed to API methods must not be
	 * <code>null</code> unless <b>explicitly</b> allowed in the method's
	 * specification. Similarly, results returned from API methods are never
	 * <code>null</code> unless <b>explicitly</b> allowed in the method's
	 * specification. Implementations are encouraged to make regular use of 
	 * <code>Assert.isNotNull</code> to ensure that <code>null</code> 
	 * parameters are detected as early as possible.
	 * </p>
	 * 
	 * @param object the value to test
	 */
	public static void isNotNull(Object object) {
		// succeed as quickly as possible
		if (object != null) {
			return;
		}
		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.
	 * <p>
	 * As a general rule, parameters passed to API methods must not be
	 * <code>null</code> unless <b>explicitly</b> allowed in the method's
	 * specification. Similarly, results returned from API methods are never
	 * <code>null</code> unless <b>explicitly</b> allowed in the method's
	 * specification. Implementations are encouraged to make regular use of 
	 * <code>Assert.isNotNull</code> to ensure that <code>null</code> 
	 * parameters are detected as early as possible.
	 * </p>
	 * 
	 * @param object the value to test
	 * @param message the message to include in the exception
	 */
	public static void isNotNull(Object object, String message)  {
		if (object == null)
			throw new AssertionFailedException(RefactoringCoreMessages.Assert_null_argument + message); 
	}

	/**
	 * 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 outcome of the check
	 * @return <code>true</code> if the check passes (does not return
	 *    if the check fails)
	 */
	public static boolean isTrue(boolean expression) {
		// succeed as quickly as possible
		if (expression) {
			return true;
		}
		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 outcome 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)
			throw new AssertionFailedException(RefactoringCoreMessages.Assert_assertion_failed + message); 
		return expression;
	}

}
