/*
 * (c) Copyright IBM Corp. 2000, 2001.
 * All Rights Reserved.
 */
package net.sourceforge.phpdt.internal.corext;

// import
// org.phpeclipse.phpdt.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>
 */
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>
	 */
	public static class AssertionFailedException extends RuntimeException {

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

		/**
		 * Constructs a new exception with the given 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("nullargument" + message); //$NON-NLS-1$
	}

	/**
	 * Asserts that the given boolean is <code>true</code>. If this is not
	 * the case, some kind of unchecked exception is thrown.
	 * 
	 * @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("assertion failed" + message); //$NON-NLS-1$
		return expression;
	}

}
