/*
 * Copyright 2003 Federal Chancellery Austria
 * MOA-ID has been developed in a cooperation between BRZ, the Federal
 * Chancellery Austria - ICT staff unit, and Graz University of Technology.
 *
 * Licensed under the EUPL, Version 1.1 or - as soon they will be approved by
 * the European Commission - subsequent versions of the EUPL (the "Licence");
 * You may not use this work except in compliance with the Licence.
 * You may obtain a copy of the Licence at:
 * http://www.osor.eu/eupl/
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the Licence is distributed on an "AS IS" basis,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the Licence for the specific language governing permissions and
 * limitations under the Licence.
 *
 * This product combines work with different licenses. See the "NOTICE" text
 * file for details on the various modules and licenses.
 * The "NOTICE" text file is part of the distribution. Any derivative works
 * that you distribute must include a readable copy of the "NOTICE" text file.
 */

package at.gv.egovernment.moaspss.util;

import java.io.ByteArrayInputStream;
import java.io.StringWriter;
import java.io.UnsupportedEncodingException;

/**
 * Translates a string into mime format "x-www-form-urlencoded". Provides a
 * function missing in JDK 1.3.
 *
 * @author Paul Ivancsics
 * @version $Id$
 */
public class URLEncoder {

  /**
   * Translates a string into x-www-form-urlencoded format.
   *
   * @param s        the string to be translated
   * @param encoding the encoding to use
   * @return the translated string
   * @throws UnsupportedEncodingException when the desired encoding is not
   *                                      supported
   */
  public static String encode(String s, String encoding) throws UnsupportedEncodingException {
//	if (MiscUtil.isEmpty(s))
//		return null;
    final byte[] barr = s.getBytes(encoding);
    final ByteArrayInputStream bin = new ByteArrayInputStream(barr);
    final StringWriter out = new StringWriter();
    for (int b = bin.read(); b >= 0; b = bin.read()) {
      encode(b, out);
    }
    return out.toString();
  }

  /**
   * Encode a character.
   *
   * @param ch  The character to encode.
   * @param out The <code>StringWriter</code> containing the result.
   */
  private static void encode(int ch, StringWriter out) {
    if (ch >= 'a' && ch <= 'z'
        || ch >= 'A' && ch <= 'Z'
        || ch >= '0' && ch <= '9'
        || ch == '.' || ch == '-' || ch == '*' || ch == '_') {
      out.write(ch);
    } else if (ch == ' ') {
      out.write('+');
    } else {
      encodeHex(ch, out);
    }
  }

  /**
   * Encode a character as an escaped hex value.
   *
   * @param ch  The character to encode.
   * @param out The <code>StringWriter</code> containing the result.
   */
  private static void encodeHex(int ch, StringWriter out) {
    out.write('%');
    final String hex = Integer.toHexString(ch).toUpperCase();
    if (hex.length() < 2) {
      out.write('0');
    } else {
      out.write(hex.charAt(hex.length() - 2));
    }
    out.write(hex.charAt(hex.length() - 1));
  }

}