package com.sjtu.util;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import java.io.IOException;
import java.security.MessageDigest;

/**
 * String Utility Class This is used to encode passwords programmatically
 * 
 * <p>
 * <a h ref="StringUtil.java.html"><i>View Source</i></a>
 * </p>
 * 
 * @author <a href="mailto:matt@raibledesigns.com">Matt Raible</a>
 */
public class StringUtil {
	// ~ Static fields/initializers
	// =============================================

	private final static Log log = LogFactory.getLog(StringUtil.class);

	// ~ Methods
	// ================================================================

	/**
	 * Encode a string using algorithm specified in web.xml and return the
	 * resulting encrypted password. If exception, the plain credentials string
	 * is returned
	 * 
	 * @param password
	 *            Password or other credentials to use in authenticating this
	 *            username
	 * @param algorithm
	 *            Algorithm used to do the digest
	 * 
	 * @return encypted password based on the algorithm.
	 */
	public static String encodePassword(String password, String algorithm) {
		byte[] unencodedPassword = password.getBytes();

		MessageDigest md = null;

		try {
			// first create an instance, given the provider
			md = MessageDigest.getInstance(algorithm);
		} catch (Exception e) {
			log.error("Exception: " + e);

			return password;
		}

		md.reset();

		// call the update method one or more times
		// (useful when you don't know the size of your data, eg. stream)
		md.update(unencodedPassword);

		// now calculate the hash
		byte[] encodedPassword = md.digest();

		StringBuffer buf = new StringBuffer();

		for (int i = 0; i < encodedPassword.length; i++) {
			if ((encodedPassword[i] & 0xff) < 0x10) {
				buf.append("0");
			}

			buf.append(Long.toString(encodedPassword[i] & 0xff, 16));
		}

		return buf.toString();
	}

	/**
	 * Encode a string using Base64 encoding. Used when storing passwords as
	 * cookies.
	 * 
	 * This is weak encoding in that anyone can use the decodeString routine to
	 * reverse the encoding.
	 * 
	 * @param str
	 * @return String
	 */
	public static String encodeString(String str) {
		sun.misc.BASE64Encoder encoder = new sun.misc.BASE64Encoder();
		return encoder.encodeBuffer(str.getBytes()).trim();
	}

	/**
	 * Decode a string using Base64 encoding.
	 * 
	 * @param str
	 * @return String
	 */
	public static String decodeString(String str) {
		sun.misc.BASE64Decoder dec = new sun.misc.BASE64Decoder();
		try {
			return new String(dec.decodeBuffer(str));
		} catch (IOException io) {
			throw new RuntimeException(io.getMessage(), io.getCause());
		}
	}
}