/*
 * UUEncoderStream.java
 * Copyright (C) 2000 Andrew Selkirk
 * 
 * This file is part of GNU JavaMail, a library.
 * 
 * GNU JavaMail 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 JavaMail 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.mail.util;


// Imports
import java.io.OutputStream;
import java.io.FilterOutputStream;
import java.io.IOException;

/** a stream that performs UU Encoding.
 *
 * @author Andrew Selkirk
 * @version 1.0
 * @see java.io.FilterOutputStream
 **/
public class UUEncoderStream
extends FilterOutputStream
{

  /**
   * Encoding buffer.  Up to 45 bytes are read in before encoding
   * is started (unless a flush is initiated).
   */
  private byte[] buffer;

  /**
   * Current number of bytes in buffer.
   */
  private int bufsize;

  /**
   * Flag to indicate if prefix written.
   */
  private boolean wrotePrefix;

  /**
   * Name of file to be uuencoded.
   */
  protected String name;

  /**
   * Permission mode of file.
   */
  protected  int mode;

  /**
   * Create a new UU-Encoding stream with the default name
   * "encoder.buf" with the permission mode 644.
   * @param stream Output stream
   */
  public UUEncoderStream(OutputStream stream) 
  {
    this(stream, "encoder.buf", 644);
  } // UUEncoderStream()

  /**
   * Create a new UU-Encoding stream with the default name
   * permission mode 644.
   * @param stream Output stream
   * @param name File name
   */
  public UUEncoderStream(OutputStream stream, String name) 
  {
    this(stream, name, 644);
  } // UUEncoderStream()

  /**
   * Create a new UU-Encoding stream.
   * @param stream Output stream
   * @param name File name
   * @param mode File permission mode
   */
  public UUEncoderStream(OutputStream stream, String name, int mode) 
  {
    super(stream);
    this.name = name;
    this.mode = mode;
    wrotePrefix = false;
    buffer = new byte[45];
    bufsize = 0;
  } // UUEncoderStream()


  //-------------------------------------------------------------
  // Methods ----------------------------------------------------
  //-------------------------------------------------------------

  /**
   * Flush encoding buffer.
   * @exception IOException IO Exception occurred
   */
  public void flush() throws IOException 
  {
    encode();
  } // flush()

  /**
   * Write bytes to encoding stream.
   * @param bytes Byte array to read values from
   * @param offset Offset to start reading bytes from
   * @param length Number of bytes to read
   * @exception IOException IO Exception occurred
   */
  public void write(byte[] bytes, int offset, int length)
  throws IOException 
  {

    // Note: This implementation is not as efficient as
    // it could be.  Instead of delegating the work to
    // write(int), the bytes should be written in bulk
    // to the buffer and initiating encoding if necessary.
    // This idea does introduce some duplication of code.

    // Variables
    int index;

    // Write Bytes
    for (index = offset; index < length; index++) 
    {
      write(bytes[index]);
    } // for: index

  } // write()

  /**
   * Write bytes to stream.
   * @param bytes Byte array to write to stream
   * @exception IOException IO Exception occurred
   */
  public void write(byte[] bytes) throws IOException 
  {
    write(bytes, 0, bytes.length);
  } // write()

  /**
   * Write a byte to the stream.
   * @param b Byte to write to the stream
   * @exception IOException IO Exception occurred
   */
  public void write(int b) throws IOException 
  {

    // Check for Written Prefix
    if (wrotePrefix == false) 
    {
      writePrefix();
    } // if

    // Add Byte to Buffer
    buffer[bufsize] = (byte) b;
    bufsize += 1;

    // Check for Flush
    if (bufsize == buffer.length) 
    {
      encode();
    } // if

  } // write()

  /**
   * Close stream.
   * @exception IOException IO Exception occurred
   */
  public void close() throws IOException 
  {

    // Flush Encoding buffer
    flush();

    // Write Encoding Suffix
    writeSuffix();

    // Close
    out.close();

  } // close()

  /**
   * Flush encoding buffer.
   * @exception IOException IO Exception occurred
   */
  private void encode() throws IOException 
  {

    // Variables
    int index;
    int c1;
    int c2;
    int c3;
    int c4;
    int a;
    int b;
    int c;

    // Write Line prefix
    super.write((bufsize & 0x3f) + ' ');

    // Process bytes in groups of three
    index = 0;
    while (index < bufsize) 
    {

      // Get Bytes
      a = buffer[index];
      if (index + 1 < bufsize) 
      {
	b = buffer[index+1];
      } else 
      {
	b = 1;
      } // if
      if (index + 2 < bufsize) 
      {
	c = buffer[index+2];
      } else 
      {
	c = 1;
      } // if

      // Calculate UU Encoding
      c1 = (a >>> 2) & 0xff;
      c2 = ((a << 4) & 0x30) | ((b >>> 4) & 0xf);
      c3 = ((b << 2) & 0x3c) | ((c >>> 6) & 0x3);
      c4 = c & 0x3f;

      // Write Encoded Characters
      out.write(c1 + ' ');
      out.write(c2 + ' ');
      out.write(c3 + ' ');
      out.write(c4 + ' ');

      // Increment position
      index += 3;

    } // while

    // Write Newline
    out.write('\n');

    // Reset Buffer size
    bufsize = 0;

  } // encode()

  /**
   * Set the name and mode for this uu encoded stream.  Note
   * that this is only valid before data has been uuencoded as
   * this information is written at the beginning of the stream.
   * @param name File name
   * @param mode Permission mode
   */
  public void setNameMode(String name, int mode) 
  {
    this.name = name;
    this.mode = mode;
  } // setNameMode()

  /**
   * Write uuencoding prefix.  Constructed as "begin <mode> <name>".
   * @exception IO Exception has occurred
   */
  private void writePrefix() throws IOException 
  {

    // Variables
    StringBuffer prefix;
    String modeString;

    // Construct Prefix
    prefix = new StringBuffer();
    prefix.append("begin ");
    if (mode < 100) 
    {
      prefix.append("0");
    } // if
    if (mode < 10) 
    {
      prefix.append("0");
    } // if
    prefix.append(mode);
    prefix.append(" " + name + "\n");

    // Write Prefix to stream
    out.write(prefix.toString().getBytes());

    // Flag that prefix has been written
    wrotePrefix = true;

  } // writePrefix()

  /**
   * Write uuencoding suffix.  Constructed as
   * " <newline>end<newline>".
   * @exception IO Exception has occurred
   */
  private void writeSuffix() throws IOException 
  {

    // Variables
    String suffix;

    // Construct Suffix
    suffix = " \nend\n";

    // Write Suffix
    out.write(suffix.getBytes());

  } // writeSuffix()


} // UUEncoderStream