/*
 * $Id: UTF7imap.java,v 1.4 2004/07/21 13:46:01 dog Exp $
 * Copyright (C) 2003 The Free Software Foundation
 * 
 * This file is part of GNU inetlib, a library.
 * 
 * GNU inetlib is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 * GNU inetlib is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * As a special exception, if you link this library with other files to
 * produce an executable, this library does not by itself cause the
 * resulting executable to be covered by the GNU General Public License.
 * This exception does not however invalidate any other reasons why the
 * executable file might be covered by the GNU General Public License.
 */

package gnu.inet.imap;

import java.io.ByteArrayOutputStream;
import java.io.IOException;

/**
 * Encodes and decodes text according to the IMAP4rev1 mailbox name
 * encoding scheme.
 *
 * @author <a href="mailto:dog@gnu.org">Chris Burdess</a>
 * @version $Revision: 1.4 $ $Date: 2004/07/21 13:46:01 $
 */
public final class UTF7imap
{

  private static final String US_ASCII = "US-ASCII";

  private static final byte[] src = {
    0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49, 0x4a,
    0x4b, 0x4c, 0x4d, 0x4e, 0x4f, 0x50, 0x51, 0x52, 0x53, 0x54,
    0x55, 0x56, 0x57, 0x58, 0x59, 0x5a, 0x61, 0x62, 0x63, 0x64,
    0x65, 0x66, 0x67, 0x68, 0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e,
    0x6f, 0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78,
    0x79, 0x7a, 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37,
    0x38, 0x39, 0x2b, 0x2c
  };

  private static final byte[] dst;
  static
  {
    dst = new byte[0x100];
    for (int i = 0; i < 0xff; i++)
      {
        dst[i] = -1;
      }
    for (int i = 0; i < src.length; i++)
      {
        dst[src[i]] = (byte) i;
      }

  }

  private UTF7imap ()
  {
  }

  /**
   * Encode the specified byte array using the modified BASE64 algorithm
   * specified by UTF-7, with further IMAP4rev1 modifications.
   *
   * @param bs the source byte array
   */
  static byte[] encode (byte[] bs)
    {
      int si = 0, ti = 0;         // source/target array indices
      byte[] bt = new byte[(((bs.length + 2) / 3) * 4) -1];// target byte array
      for (; si < bs.length; si += 3)
        {
          int buflen = bs.length - si;
          if (buflen == 1)
            {
              byte b = bs[si];
              int i = 0;
              boolean flag = false;
              bt[ti++] = src[b >>> 2 & 0x3f];
              bt[ti++] = src[(b << 4 & 0x30) + (i >>> 4 & 0xf)];
            }
          else if (buflen == 2)
            {
              byte b1 = bs[si], b2 = bs[si + 1];
              int i = 0;
              bt[ti++] = src[b1 >>> 2 & 0x3f];
              bt[ti++] = src[(b1 << 4 & 0x30) + (b2 >>> 4 & 0xf)];
              bt[ti++] = src[(b2 << 2 & 0x3c) + (i >>> 6 & 0x3)];
            }
          else if (buflen == 3)
            {
              byte b1 = bs[si], b2 = bs[si + 1], b3 = bs[si + 2];
              bt[ti++] = src[b1 >>> 2 & 0x3f];
              bt[ti++] = src[(b1 << 4 & 0x30) + (b2 >>> 4 & 0xf)];
              bt[ti++] = src[(b2 << 2 & 0x3c) + (b3 >>> 6 & 0x3)];
              bt[ti++] = src[b3 & 0x3f];
            }
        }
      return bt;
    }

  /**
   * Decode the specified byte array using the modified BASE64 algorithm
   * specified by UTF-7, with further IMAP4rev1 modifications.
   *
   * @param bs the source byte array
   */
  static int[] decode (byte[] bs)
    {
      int[] buffer = new int[bs.length];
      int buflen = 0;
      int si = 0;
      int len = bs.length - si;
      while (len > 0)
        {
          byte b0 = dst[bs[si++] & 0xff];
          byte b2 = dst[bs[si++] & 0xff];
          buffer[buflen++] = (b0 << 2 & 0xfc | b2 >>> 4 & 0x3);
          if (len > 2)
            {
              b0 = b2;
              b2 = dst[bs[si++] & 0xff];
              buffer[buflen++] = (b0 << 4 & 0xf0 | b2 >>> 2 & 0xf);
              if (len > 3)
                {
                  b0 = b2;
                  b2 = dst[bs[si++] & 0xff];
                  buffer[buflen++] = (b0 << 6 & 0xc0 | b2 & 0x3f);
                }
            }
          len = bs.length - si;
        }
      int[] bt = new int[buflen];
      System.arraycopy (buffer, 0, bt, 0, buflen);
      return bt;
    }

  /**
   * Encodes the specified name using the UTF-7.imap encoding.
   * See IMAP4rev1 spec, section 5.1.3
   */
  public static String encode (String name)
    {
      try
        {
          StringBuffer buffer = null;
          ByteArrayOutputStream encoderSink = null;
          char[] chars = name.toCharArray ();
          boolean encoding = false;
          for (int i = 0; i < chars.length; i++)
            {
              char c = chars[i];
              if (c == '&')
                {
                  if (buffer == null)
                    {
                      buffer = new StringBuffer ();
                      for (int j = 0; j < i; j++)
                        {
                          buffer.append (chars[j]);
                        }
                    }
                  buffer.append ('&');
                  buffer.append ('-');
                }
              if (c < 0x1f || c > 0x7f)
                {
                  // needs encoding
                  if (buffer == null)
                    {
                      buffer = new StringBuffer ();
                      for (int j = 0; j < i; j++)
                        {
                          buffer.append (chars[j]);
                        }
                      encoderSink = new ByteArrayOutputStream ();
                    }
                  if (!encoding)
                    {
                      encoderSink.reset ();
                      buffer.append ('&');
                      encoding = true;
                    }
                  encoderSink.write (((int) c) / 0x100);
                  encoderSink.write (((int) c) % 0x100);
                }
              else if (encoding)
                {
                  encoderSink.flush ();
                  byte[] encoded = encode (encoderSink.toByteArray ());
                  buffer.append (new String (encoded, US_ASCII));
                  buffer.append ('-');
                  encoding = false;
                  if (c != '-')
                    {
                      buffer.append (c);
                    }
                }
              else if (buffer != null)
                {
                  buffer.append (c);
                }
            }
          if (encoding)
            {
              encoderSink.flush ();
              byte[] encoded = encode (encoderSink.toByteArray ());
              buffer.append (new String(encoded, US_ASCII));
              buffer.append ('-');
            }
          if (buffer != null)
            {
              return buffer.toString ();
            }
        }
      catch (IOException e)
        {
          // This should never happen
          throw new RuntimeException (e.getMessage ());
        }
      return name;
    }

  /**
   * Decodes the specified name using the UTF-7.imap decoding.
   * See IMAP4rev1 spec, section 5.1.3
   */
  public static String decode (String name)
    {
      StringBuffer buffer = null;
      ByteArrayOutputStream decoderSink = null;
      char[] chars = name.toCharArray ();
      boolean encoded = false;
      for (int i = 0; i < chars.length; i++)
        {
          char c = chars[i];
          if (c == '&')
            {
              if (buffer == null)
                {
                  buffer = new StringBuffer ();
                  decoderSink = new ByteArrayOutputStream ();
                  for (int j = 0; j < i; j++)
                    {
                      buffer.append (chars[j]);
                    }
                }
              decoderSink.reset ();
              encoded = true;
            }
          else if (c == '-' && encoded)
            {
              if (decoderSink.size () == 0)
                {
                  buffer.append ('&');
                }
              else
                {
                  int[] decoded = decode (decoderSink.toByteArray ());
                  for (int j = 0; j < decoded.length - 1; j += 2)
                    {
                      int hibyte = decoded[j];
                      int lobyte = decoded[j + 1];
                      int d = (hibyte * 0x100) | lobyte;
                      buffer.append ((char) d);
                    }
                }
              encoded = false;
            }
          else if (encoded)
            {
              decoderSink.write ((byte) c);
            }
          else if (buffer != null)
            {
              buffer.append (c);
            }
        }
      if (buffer != null)
        {
          return buffer.toString ();
        }
      return name;
    }

  public static void main (String[] args)
    {
      boolean decode = false;
      for (int i = 0; i < args.length; i++)
        {
          if (args[i].equals ("-d"))
            {
              decode = true;
            }
          else
            {
              String ret = decode ? decode (args[i]) : encode (args[i]);
              StringBuffer buf = new StringBuffer (args[i]);
              buf.append (" = \"");
              buf.append (ret);
              buf.append ("\" (");
              for (int j = 0; j < ret.length (); j++)
                {
                  if (j > 0)
                    {
                      buf.append (' ');
                    }
                  int c = (int) (ret.charAt (j));
                  buf.append (Integer.toString (c, 16));
                }
              buf.append (")");
              System.out.println (buf.toString ());
            }
        }
    }

}