/*******************************************************************************
 * Copyright (c) 2006 Sybase, Inc. 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:
 *     Sybase, Inc. - initial API and implementation
 *******************************************************************************/
package org.eclipse.jst.jsf.common.ui.internal.utils;

/**
 * @author mengbo
 * @version 1.5
 */
public class UTF8Util {
	private static final char[] HEX_DIGITS = { '0', '1', '2', '3', '4', '5',
			'6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };

	public static String unwindEscapeChars(String s) {
		StringBuffer sb = new StringBuffer(s.length());
		int length = s.length();
		for (int i = 0; i < length; i++) {
			char c = s.charAt(i);
			sb.append(getUnwoundString(c));
		}
		return sb.toString();
	}

	private static String getUnwoundString(char c) {
		switch (c) {
		case '\b':
			return "\\b";//$NON-NLS-1$
		case '\t':
			return "\\t";//$NON-NLS-1$
		case '\n':
			return "\\n";//$NON-NLS-1$
		case '\f':
			return "\\f";//$NON-NLS-1$	
		case '\r':
			return "\\r";//$NON-NLS-1$

			// These can be used unescaped in properties file:
		case '\"':
			return "\\\"";//$NON-NLS-1$
		case '\'':
			return "\\\'";//$NON-NLS-1$

		case '\\':
			return "\\\\";//$NON-NLS-1$

		case '=':
			return "\\=";//$NON-NLS-1$

			// This is only done when writing to the .properties file in
			// #unwindValue(String)
			// case '!':
			// return "\\!";//$NON-NLS-1$
			// case '#':
			// return "\\#";//$NON-NLS-1$

		default:
			if (((c < 0x0020) || (c > 0x007e))) {
				return new StringBuffer().append('\\').append('u').append(
						toHex((c >> 12) & 0xF)).append(toHex((c >> 8) & 0xF))
						.append(toHex((c >> 4) & 0xF)).append(toHex(c & 0xF))
						.toString();

			}
			return String.valueOf(c);
		}
	}

	private static char toHex(int halfByte) {
		return HEX_DIGITS[(halfByte & 0xF)];
	}

}