/*******************************************************************************
 * Copyright (c) 2000, 2007 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.jsdt.internal.ui.propertiesfileeditor;

import org.eclipse.jface.text.rules.ICharacterScanner;
import org.eclipse.jface.text.rules.IToken;
import org.eclipse.jface.text.rules.IWordDetector;
import org.eclipse.jface.text.rules.WordPatternRule;


/**
 * A leading white space predicate rule.
 *
 * @since 3.1
 */
public final class LeadingWhitespacePredicateRule extends WordPatternRule {


	private static class DummyDetector implements IWordDetector {

		/*
		 * @see IWordDetector#isWordStart
		 */
		public boolean isWordStart(char c) {
			return false;
		}

		/*
		 * @see IWordDetector#isWordPart
		 */
		public boolean isWordPart(char c) {
			return false;
		}
	}


	/**
	 * Creates a white space rule for the given <code>token</code>.
	 *
	 * @param token the token to be returned on success
	 */
	public LeadingWhitespacePredicateRule(IToken token, String whitespace) {
		super(new DummyDetector(), whitespace, "dummy", token); //$NON-NLS-1$
		setColumnConstraint(0);
	}

	/*
	 * @see org.eclipse.jface.text.rules.WordPatternRule#endSequenceDetected(org.eclipse.jface.text.rules.ICharacterScanner)
	 */
	protected boolean endSequenceDetected(ICharacterScanner scanner) {
		int c;
		do {
			c= scanner.read();
		} while (Character.isWhitespace((char) c));

		scanner.unread();

		return true;
	}
}