/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at
 * trunk/opends/resource/legal-notices/OpenDS.LICENSE
 * or https://OpenDS.dev.java.net/OpenDS.LICENSE.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at
 * trunk/opends/resource/legal-notices/OpenDS.LICENSE.  If applicable,
 * add the following below this CDDL HEADER, with the fields enclosed
 * by brackets "[]" replaced with your own identifying * information:
 *      Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 *
 *
 *      Portions Copyright 2006 Sun Microsystems, Inc.
 */
package org.opends.server.util;



import static org.opends.server.loggers.Debug.debugEnter;
import static org.opends.server.messages.MessageHandler.getMessage;
import static org.opends.server.messages.UtilityMessages.*;
import static org.opends.server.util.Validator.*;

import java.nio.ByteBuffer;
import java.text.ParseException;



/**
 * This class provides methods for performing base64 encoding and decoding.
 * Base64 is a mechanism for encoding binary data in ASCII form by converting
 * sets of three bytes with eight significant bits each to sets of four bytes
 * with six significant bits each.
 */
public final class Base64
{
  /**
   * The fully-qualified name of this class for debugging purposes.
   */
  private static final String CLASS_NAME = "org.opends.server.util.Base64";



  /**
   * The set of characters that may be used in base64-encoded values.
   */
  private static final char[] BASE64_ALPHABET =
       ("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz" +
        "0123456789+/").toCharArray();

  /**
   * Prevent instance creation.
   */
  private Base64() {
    // No implementation required.
  }

  /**
   * Encodes the provided raw data using base64.
   *
   * @param  rawData  The raw data to encode.  It must not be <CODE>null</CODE>.
   *
   * @return  The base64-encoded representation of the provided raw data.
   */
  public static String encode(byte[] rawData)
  {
    assert debugEnter(CLASS_NAME, "encode", String.valueOf(rawData));

    ensureNotNull(rawData);


    StringBuilder buffer = new StringBuilder(4 * rawData.length / 3);

    int pos = 0;
    int iterations = rawData.length / 3;
    for (int i=0; i < iterations; i++)
    {
      int value = ((rawData[pos++] & 0xFF) << 16) |
                  ((rawData[pos++] & 0xFF) <<  8) | (rawData[pos++] & 0xFF);

      buffer.append(BASE64_ALPHABET[(value >>> 18) & 0x3F]);
      buffer.append(BASE64_ALPHABET[(value >>> 12) & 0x3F]);
      buffer.append(BASE64_ALPHABET[(value >>>  6) & 0x3F]);
      buffer.append(BASE64_ALPHABET[value & 0x3F]);
    }


    switch (rawData.length % 3)
    {
      case 1:
        buffer.append(BASE64_ALPHABET[(rawData[pos] >>> 2) & 0x3F]);
        buffer.append(BASE64_ALPHABET[(rawData[pos] <<  4) & 0x3F]);
        buffer.append("==");
        break;
      case 2:
        int value = ((rawData[pos++] & 0xFF) << 8) | (rawData[pos] & 0xFF);
        buffer.append(BASE64_ALPHABET[(value >>> 10) & 0x3F]);
        buffer.append(BASE64_ALPHABET[(value >>>  4) & 0x3F]);
        buffer.append(BASE64_ALPHABET[(value <<   2) & 0x3F]);
        buffer.append("=");
        break;
    }

    return buffer.toString();
  }



  /**
   * Decodes the provided set of base64-encoded data.
   *
   * @param  encodedData  The base64-encoded data to decode.  It must not be
   *                      <CODE>null</CODE>.
   *
   * @return  The decoded raw data.
   *
   * @throws  ParseException  If a problem occurs while attempting to decode the
   *                          provided data.
   */
  public static byte[] decode(String encodedData)
         throws ParseException
  {
    assert debugEnter(CLASS_NAME, "decode", String.valueOf(encodedData));

    ensureNotNull(encodedData);


    // The encoded value must have  length that is a multiple of four bytes.
    int length = encodedData.length();
    if ((length % 4) != 0)
    {
      int    msgID   = MSGID_BASE64_DECODE_INVALID_LENGTH;
      String message = getMessage(msgID, encodedData);
      throw new ParseException(message, 0);
    }


    ByteBuffer buffer = ByteBuffer.allocate(length);
    for (int i=0; i < length; i += 4)
    {
      boolean append = true;
      int     value  = 0;

      for (int j=0; j < 4; j++)
      {
        switch (encodedData.charAt(i+j))
        {
          case 'A':
            value <<= 6;
            break;
          case 'B':
            value = (value << 6) | 0x01;
            break;
          case 'C':
            value = (value << 6) | 0x02;
            break;
          case 'D':
            value = (value << 6) | 0x03;
            break;
          case 'E':
            value = (value << 6) | 0x04;
            break;
          case 'F':
            value = (value << 6) | 0x05;
            break;
          case 'G':
            value = (value << 6) | 0x06;
            break;
          case 'H':
            value = (value << 6) | 0x07;
            break;
          case 'I':
            value = (value << 6) | 0x08;
            break;
          case 'J':
            value = (value << 6) | 0x09;
            break;
          case 'K':
            value = (value << 6) | 0x0A;
            break;
          case 'L':
            value = (value << 6) | 0x0B;
            break;
          case 'M':
            value = (value << 6) | 0x0C;
            break;
          case 'N':
            value = (value << 6) | 0x0D;
            break;
          case 'O':
            value = (value << 6) | 0x0E;
            break;
          case 'P':
            value = (value << 6) | 0x0F;
            break;
          case 'Q':
            value = (value << 6) | 0x10;
            break;
          case 'R':
            value = (value << 6) | 0x11;
            break;
          case 'S':
            value = (value << 6) | 0x12;
            break;
          case 'T':
            value = (value << 6) | 0x13;
            break;
          case 'U':
            value = (value << 6) | 0x14;
            break;
          case 'V':
            value = (value << 6) | 0x15;
            break;
          case 'W':
            value = (value << 6) | 0x16;
            break;
          case 'X':
            value = (value << 6) | 0x17;
            break;
          case 'Y':
            value = (value << 6) | 0x18;
            break;
          case 'Z':
            value = (value << 6) | 0x19;
            break;
          case 'a':
            value = (value << 6) | 0x1A;
            break;
          case 'b':
            value = (value << 6) | 0x1B;
            break;
          case 'c':
            value = (value << 6) | 0x1C;
            break;
          case 'd':
            value = (value << 6) | 0x1D;
            break;
          case 'e':
            value = (value << 6) | 0x1E;
            break;
          case 'f':
            value = (value << 6) | 0x1F;
            break;
          case 'g':
            value = (value << 6) | 0x20;
            break;
          case 'h':
            value = (value << 6) | 0x21;
            break;
          case 'i':
            value = (value << 6) | 0x22;
            break;
          case 'j':
            value = (value << 6) | 0x23;
            break;
          case 'k':
            value = (value << 6) | 0x24;
            break;
          case 'l':
            value = (value << 6) | 0x25;
            break;
          case 'm':
            value = (value << 6) | 0x26;
            break;
          case 'n':
            value = (value << 6) | 0x27;
            break;
          case 'o':
            value = (value << 6) | 0x28;
            break;
          case 'p':
            value = (value << 6) | 0x29;
            break;
          case 'q':
            value = (value << 6) | 0x2A;
            break;
          case 'r':
            value = (value << 6) | 0x2B;
            break;
          case 's':
            value = (value << 6) | 0x2C;
            break;
          case 't':
            value = (value << 6) | 0x2D;
            break;
          case 'u':
            value = (value << 6) | 0x2E;
            break;
          case 'v':
            value = (value << 6) | 0x2F;
            break;
          case 'w':
            value = (value << 6) | 0x30;
            break;
          case 'x':
            value = (value << 6) | 0x31;
            break;
          case 'y':
            value = (value << 6) | 0x32;
            break;
          case 'z':
            value = (value << 6) | 0x33;
            break;
          case '0':
            value = (value << 6) | 0x34;
            break;
          case '1':
            value = (value << 6) | 0x35;
            break;
          case '2':
            value = (value << 6) | 0x36;
            break;
          case '3':
            value = (value << 6) | 0x37;
            break;
          case '4':
            value = (value << 6) | 0x38;
            break;
          case '5':
            value = (value << 6) | 0x39;
            break;
          case '6':
            value = (value << 6) | 0x3A;
            break;
          case '7':
            value = (value << 6) | 0x3B;
            break;
          case '8':
            value = (value << 6) | 0x3C;
            break;
          case '9':
            value = (value << 6) | 0x3D;
            break;
          case '+':
            value = (value << 6) | 0x3E;
            break;
          case '/':
            value = (value << 6) | 0x3F;
            break;
          case '=':
            append = false;
            switch (j)
            {
              case 2:
                buffer.put((byte) ((value >>> 4) & 0xFF));
                break;
              case 3:
                buffer.put((byte) ((value >>> 10) & 0xFF));
                buffer.put((byte) ((value >>>  2) & 0xFF));
                break;
            }
            break;
          default:
            int msgID = MSGID_BASE64_DECODE_INVALID_CHARACTER;
            String message = getMessage(msgID, encodedData,
                                        encodedData.charAt(i+j));
            throw new ParseException(message, i+j);
        }


        if (! append)
        {
          break;
        }
      }


      if (append)
      {
        buffer.put((byte) ((value >>> 16) & 0xFF));
        buffer.put((byte) ((value >>>  8) & 0xFF));
        buffer.put((byte) (value & 0xFF));
      }
      else
      {
        break;
      }
    }


    buffer.flip();
    byte[] returnArray = new byte[buffer.limit()];
    buffer.get(returnArray);
    return returnArray;
  }
}