/**
 * Copyright (C) 2009 eXo Platform SAS.
 * 
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 * 
 * This software 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
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */

package org.exoplatform.services.text;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintStream;

public class CharacterEncoder
{

   private PrintStream printStream;

   private char pemArray[] = {
   // 0   1   2   3   4   5   6   7
      'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', // 0
      'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', // 1
      'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', // 2
      'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', // 3
      'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', // 4
      'o', 'p', 'q', 'r', 's', 't', 'u', 'v', // 5
      'w', 'x', 'y', 'z', '0', '1', '2', '3', // 6
      '4', '5', '6', '7', '8', '9', '+', '-' // 7
      };

   //encodes 57 bytes per line
   private int bytesPerLine()
   {
      return (57);
   }

   //encodes pree bytes per atom
   private int bytesPerAtom()
   {
      return (3);
   }

   @SuppressWarnings("unused")
   private void encodeLineSuffix(OutputStream aStream) throws Exception
   {
      printStream.println();
   }

   @SuppressWarnings("unused")
   private void encodeBufferSuffix(OutputStream aStream) throws Exception
   {
   }

   @SuppressWarnings("unused")
   private void encodeBufferPrefix(OutputStream aStream) throws Exception
   {
      this.printStream = new PrintStream(aStream);
   }

   @SuppressWarnings("unused")
   private void encodeLinePrefix(OutputStream aStream, int aLength) throws Exception
   {
   }

   private int readFully(InputStream in, byte buffer[]) throws IOException
   {
      for (int i = 0; i < buffer.length; i++)
      {
         int q = in.read();
         if (q == -1)
            return i;
         buffer[i] = (byte)q;
      }
      return buffer.length;
   }

   public String encodeBuffer(byte aBuffer[])
   {
      ByteArrayInputStream in = new ByteArrayInputStream(aBuffer);
      ByteArrayOutputStream out = new ByteArrayOutputStream();
      try
      {
         encodeBuffer(in, out);
      }
      catch (Exception IOException)
      {
         throw new Error("ChracterEncoder::encodeBuffer internal error");
      }
      return (out.toString().trim());
   }

   public void encodeBuffer(InputStream in, OutputStream out) throws Exception
   {
      int j;
      int numBytes;
      byte tmpbuffer[] = new byte[bytesPerLine()];

      encodeBufferPrefix(out);

      while (true)
      {
         numBytes = readFully(in, tmpbuffer);
         if (numBytes == -1)
         {
            break;
         }
         encodeLinePrefix(out, numBytes);
         for (j = 0; j < numBytes; j += bytesPerAtom())
         {
            if ((j + bytesPerAtom()) <= numBytes)
            {
               encodeAtom(out, tmpbuffer, j, bytesPerAtom());
            }
            else
            {
               encodeAtom(out, tmpbuffer, j, (numBytes) - j);
            }
         }
         encodeLineSuffix(out);
         if (numBytes < bytesPerLine())
         {
            break;
         }
      }
      encodeBufferSuffix(out);
   }

   private void encodeAtom(OutputStream outStream, byte data[], int offset, int len) throws IOException
   {
      byte a, b, c;
      if (len == 1)
      {
         a = data[offset];
         b = 0;
         c = 0;
         outStream.write(pemArray[(a >>> 2) & 0x3F]);
         outStream.write(pemArray[((a << 4) & 0x30) + ((b >>> 4) & 0xf)]);
         outStream.write('=');
         outStream.write('=');
      }
      else if (len == 2)
      {
         a = data[offset];
         b = data[offset + 1];
         c = 0;
         outStream.write(pemArray[(a >>> 2) & 0x3F]);
         outStream.write(pemArray[((a << 4) & 0x30) + ((b >>> 4) & 0xf)]);
         outStream.write(pemArray[((b << 2) & 0x3c) + ((c >>> 6) & 0x3)]);
         outStream.write('=');
      }
      else
      {
         a = data[offset];
         b = data[offset + 1];
         c = data[offset + 2];
         outStream.write(pemArray[(a >>> 2) & 0x3F]);
         outStream.write(pemArray[((a << 4) & 0x30) + ((b >>> 4) & 0xf)]);
         outStream.write(pemArray[((b << 2) & 0x3c) + ((c >>> 6) & 0x3)]);
         outStream.write(pemArray[c & 0x3F]);
      }
   }
}
