/*******************************************************************************
 * Copyright (c) 2004, 2009 Tasktop Technologies 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:
 *     Tasktop Technologies - initial API and implementation
 *******************************************************************************/

package org.eclipse.mylyn.internal.commons.core;

/**
 * @author Ken Sueda
 */
// XXX should use xerces or some other parser's facilities
public class XmlStringConverter {

	@Deprecated
	public static String convertToXmlString(String s) {
		if (s == null) {
			return ""; //$NON-NLS-1$
		}
		StringBuffer res = new StringBuffer(s.length() + 20);
		for (int i = 0; i < s.length(); ++i) {
			appendEscapedChar(res, s.charAt(i));
		}
		return res.toString();
	}

	private static void appendEscapedChar(StringBuffer buffer, char c) {
		String replacement = getReplacementForSymbol(c);
		if (replacement != null) {
			buffer.append('&');
			buffer.append(replacement);
			buffer.append(';');
		} else {
			buffer.append(c);
		}
	}

	private static String getReplacementForSymbol(char c) {
		switch (c) {
		case '<':
			return "lt"; //$NON-NLS-1$
		case '>':
			return "gt"; //$NON-NLS-1$
		case '"':
			return "quot"; //$NON-NLS-1$
		case '\'':
			return "apos"; //$NON-NLS-1$
		case '&':
			return "amp"; //$NON-NLS-1$
		case '\r':
			return "#x0D"; //$NON-NLS-1$
		case '\n':
			return "#x0A"; //$NON-NLS-1$
		case '\u0009':
			return "#x09"; //$NON-NLS-1$
		}
		return null;
	}

	@Deprecated
	public static String convertXmlToString(String string) {
		StringBuilder result = new StringBuilder(string.length() + 10);
		for (int i = 0; i < string.length(); ++i) {
			char xChar = string.charAt(i);
			if (xChar == '&') {
				i++;
				StringBuffer escapeChar = new StringBuffer(10);
				boolean flag = true;
				while (flag) {
					xChar = string.charAt(i++);
					if (xChar == ';') {
						flag = false;
						i--;
					} else {
						escapeChar.append(xChar);
					}
				}
				result.append(getReplacementForXml(escapeChar.toString()));
			} else {
				result.append(xChar);
			}
		}
		return result.toString();
	}

	private static char getReplacementForXml(String s) {
		if (s.equals("lt")) { //$NON-NLS-1$
			return '<';
		} else if (s.equals("gt")) { //$NON-NLS-1$
			return '>';
		} else if (s.equals("quot")) { //$NON-NLS-1$
			return '"';
		} else if (s.equals("apos")) { //$NON-NLS-1$
			return '\'';
		} else if (s.equals("amp")) { //$NON-NLS-1$
			return '&';
		} else if (s.equals("#x0D")) { //$NON-NLS-1$
			return '\r';
		} else if (s.equals("#x0A")) { //$NON-NLS-1$
			return '\n';
		} else if (s.equals("#x09")) { //$NON-NLS-1$
			return '\u0009';
		}
		return 0;
	}

	/**
	 * @param text
	 *            string to clean
	 * @return string with all non valid characters removed, if text is null return null
	 */
	public static String cleanXmlString(String text) {
		if (text == null) {
			return null;
		}
		StringBuilder builder = new StringBuilder(text.length());
		for (int x = 0; x < text.length(); x++) {
			char ch = text.charAt(x);
			if (isValid(ch)) {
				builder.append(ch);
			}
		}
		return builder.toString();
	}

	/**
	 * Return true if character is a valid xml character
	 * 
	 * @see http://www.w3.org/TR/REC-xml/
	 */
	public static boolean isValid(char ch) {
		return (0x0A == ch || 0x0D == ch || 0x09 == ch) || (ch >= 0x20 && ch <= 0xD7FF)
				|| (ch >= 0xE000 && ch <= 0xFFFD) || (ch >= 0x10000 && ch <= 0x10FFFF);
	}

}