/*
 * IMAPResponseTokenizer.java
 * 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
 * 
 * Linking this library statically or dynamically with other modules is
 * making a combined work based on this library.  Thus, the terms and
 * conditions of the GNU General Public License cover the whole
 * combination.
 *
 * As a special exception, the copyright holders of this library give you
 * permission to link this library with independent modules to produce an
 * executable, regardless of the license terms of these independent
 * modules, and to copy and distribute the resulting executable under
 * terms of your choice, provided that you also meet, for each linked
 * independent module, the terms and conditions of the license of that
 * module.  An independent module is a module which is not derived from
 * or based on this library.  If you modify this library, you may extend
 * this exception to your version of the library, but you are not
 * obliged to do so.  If you do not wish to do so, delete this
 * exception statement from your version.
 */

package gnu.inet.imap;

import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.io.IOException;
import java.net.ProtocolException;
import java.util.ArrayList;
import java.util.List;
import java.util.Stack;

/**
 * An object that can parse an underlying socket stream containing IMAP
 * protocol server responses into IMAPResponse tokens.
 *
 * @author <a href='mailto:dog@gnu.org'>Chris Burdess</a>
 */
public class IMAPResponseTokenizer
  implements IMAPConstants
{

  /**
   * The server stream.
   */
  protected InputStream in;

  private byte[] buffer = null;

  private static final int BUFFER_SIZE = 4096; // Seems to be a good value
  private static final String DEFAULT_ENCODING = "US-ASCII";

  private static final int STATE_TAG = 0;
  private static final int STATE_COUNT = 1;
  private static final int STATE_ID = 2;
  private static final int STATE_MAYBE_CODE = 3;
  private static final int STATE_CODE = 4;
  private static final int STATE_LITERAL_LENGTH = 5;
  private static final int STATE_LITERAL = 6;
  private static final int STATE_TEXT = 7;
  private static final int STATE_STATUS = 8;

  /**
   * Constructor.
   * @param in the server socket input stream
   */
  public IMAPResponseTokenizer(InputStream in)
  {
    this.in = in;
  }

  /*
   * Reads bytes, from the underlying stream if necessary, or from the
   * cache. If moreNeeded is specified, always performs a read to append
   * more to the cache.
   */
  byte[] read(boolean moreNeeded)
    throws IOException
  {
    if (buffer != null && !moreNeeded && buffer.length > 0)
      {
        return buffer;
      }
    int max = in.available();
    if (max < 1)
      {
        max = BUFFER_SIZE;
      }
    byte[] tmp = new byte[max];
    int len = 0;
    while (len == 0)
      {
        len = in.read(tmp, 0, max);
      }
    if (len == -1)
      {
        return null;              // EOF
      }
    int blen =(buffer == null) ? 0 : buffer.length;
    byte[] uni = new byte[blen + len];
    if (blen != 0)
      {
        System.arraycopy(buffer, 0, uni, 0, blen);
      }
    System.arraycopy(tmp, 0, uni, blen, len);
    buffer = uni;
    return buffer;
  }

  /*
   * Invalidates the byte cache up to the specified index.
   */
  void mark(int index)
  {
    int len = buffer.length;
    int start = index + 1;
    if (start < len)
      {
        int n =(len - start);
        byte[] tmp = new byte[n];
        System.arraycopy(buffer, start, tmp, 0, n);
        buffer = tmp;
      }
    else
      {
        buffer = null;
      }
  }

  /**
   * Returns the next IMAPResponse.
   */
  public IMAPResponse next()
    throws IOException
  {
    // Perform read
    byte[] buf = read(false);
    if (buf == null)
      {
        return null;              // pass EOF back up the chain
      }
    int len = buf.length;
    
    IMAPResponse response = new IMAPResponse();
    ByteArrayOutputStream genericSink = new ByteArrayOutputStream();
    ByteArrayOutputStream literalSink = null;
    int literalCount = 0, literalLength = -1;
    Stack context = new Stack();
    int state = STATE_TAG;
    boolean inQuote = false;
    boolean inContent = false;
    for (int i = 0; i < len; i++)
      {
        byte b = buf[i];
        switch (state)
          {
          case STATE_TAG:          // expect tag
            if (i == 0 && b == 0x2a)        // untagged
              {
                response.tag = IMAPResponse.UNTAGGED;
              }
            else if (i == 0 && b == 0x2b)   // continuation
              {
                response.tag = IMAPResponse.CONTINUATION;
              }
            else if (b == 0x20)     // delimiter
              {
                if (response.tag == null)
                  {
                    byte[] tb = genericSink.toByteArray();
                    response.tag = new String(tb, DEFAULT_ENCODING);
                  }
                genericSink.reset();
                if (response.isContinuation())
                  {
                    state = STATE_TEXT;
                  }
                else
                  {
                    state = STATE_COUNT;
                  }
              }
            else                    // tag literal
              {
                genericSink.write(b);
              }
            break;
          case STATE_COUNT:        // expect count or id
            if (b < 0x30 || b > 0x39)
              {
                state = STATE_ID;
              }
            if (b == 0x20)          // delimiter
              {
                byte[] cb = genericSink.toByteArray();
                genericSink.reset();
                String cs = new String(cb, DEFAULT_ENCODING);
                try
                  {
                    response.count = Integer.parseInt(cs);
                  }
                catch (NumberFormatException e)
                  {
                    throw new ProtocolException("Expecting number: " + cs);
                  }
                state = STATE_ID;
              }
            else
              {
                genericSink.write(b);
              }
            break;
          case STATE_ID:           // expect id
            if (b == 0x20)          // delimiter
              {
                byte[] ib = genericSink.toByteArray();
                genericSink.reset();
                response.id = new String(ib, DEFAULT_ENCODING).intern();
                state = STATE_MAYBE_CODE;
              }
            else if (b == 0x0a)     // EOL
              {
                byte[] ib = genericSink.toByteArray();
                genericSink.reset();
                response.id = new String(ib, DEFAULT_ENCODING).intern();
                state = STATE_TAG;
                // mark bytes read
                mark(i);
                return response;
              }
            else if (b != 0x0d)     // id literal
              {
                genericSink.write(b);
              }
            break;
          case STATE_MAYBE_CODE:   // expect code or text
            if (b == 0x28 || b == 0x5b)
              {
                List top = new ArrayList();
                response.code = top;
                context.push(top);
                state = STATE_CODE;
              }
            else
              {
                if (response.id == FETCH)
                  {
                    // We can't have text here so it must be the beginning of
                    // FETCH FLAGS. Go back to ID state.
                    genericSink.reset();
                    byte[] fetchBytes =
                      new byte[] { 0x46, 0x45, 0x54, 0x43, 0x48, 0x20};
                    genericSink.write(fetchBytes);
                    genericSink.write(b);
                    state = STATE_ID;
                  }
                else if (response.id == STATUS)
                  {
                    // We are in the mailbox name part of the STATUS response
                    genericSink.write(b);
                    state = STATE_STATUS;
                  }
                else
                  {
                    genericSink.write(b);
                    state = STATE_TEXT;
                  }
              }
            break;
          case STATE_STATUS:
            if (b == 0x20)          // delimiter
              {
                response.mailbox = genericSink.toString();
                genericSink.reset();
                state = STATE_MAYBE_CODE;
              }
            else
              {
                genericSink.write(b);
              }
            break;
          case STATE_CODE:         // response code inside parentheses
            if (b == 0x22)          // quote delimiter
              {
                inQuote = !inQuote;
              }
            else if (inQuote)
              {
                genericSink.write(b);
              }
            else
              {
                if (b == 0x28 || b == 0x5b)   // start parenthesis/bracket
                  {
                    List parent =(List) context.peek();
                    List top = new ArrayList();
                    if (genericSink.size() > 0)
                      {
                        byte[] tb = genericSink.toByteArray();
                        String token =
                          new String(tb, DEFAULT_ENCODING).intern();
                        Pair pair = new Pair(token, top);
                        parent.add(pair);
                        genericSink.reset();
                      }
                    else
                      {
                        parent.add(top);
                      }
                    context.push(top);
                  }
                else if (b == 0x29 || b == 0x5d)      // end parenthesis/bracket
                  {
                    List top =(List) context.pop();
                    // flush genericSink
                    if (genericSink.size() > 0)
                      {
                        byte[] tb = genericSink.toByteArray();
                        String token =
                          new String(tb, DEFAULT_ENCODING).intern();
                        top.add(token);
                        genericSink.reset();
                      }
                  }
                else if (b == 0x7b)   // literal length
                  {
                    genericSink.reset();
                    state = STATE_LITERAL_LENGTH;
                  }
                else if (b == 0x20)   // token delimiter
                  {
                    if (context.size() == 0)    // end state
                      {
                        state = STATE_TEXT;
                      }
                    else                // add token
                      {
                        List top =(List) context.peek();
                        // flush genericSink
                        if (genericSink.size() > 0)
                          {
                            byte[] tb = genericSink.toByteArray();
                            String token =
                              new String(tb, DEFAULT_ENCODING).intern();
                            top.add(token);
                            genericSink.reset();
                          }
                      }
                  }
                else if (b == 0x0a)   // EOL
                  {
                    state = STATE_TAG;
                    // mark bytes read
                    mark(i);
                    return response;
                  }
                else if (b != 0x0d)   // ignore CR
                  {
                    genericSink.write(b);
                  }
              }
            break;
          case STATE_LITERAL_LENGTH:
            if (b == 0x7d)          // end literal length
              {
                byte[] cb = genericSink.toByteArray();
                genericSink.reset();
                String cs = new String(cb, DEFAULT_ENCODING);
                try
                  {
                    literalLength = Integer.parseInt(cs);
                  }
                catch (NumberFormatException e)
                  {
                    throw new ProtocolException("Expecting number: " + cs);
                  }
              }
            else if (b == 0x0a)     // start literal
              {
                state = STATE_LITERAL;
                literalSink = new ByteArrayOutputStream();
                literalCount = 0;
              }
            else if (b != 0x0d)     // ignore CR
              {
                genericSink.write(b);
              }
            break;
          case STATE_LITERAL:
            if (literalCount >= literalLength)
              {
                List top =(List) context.peek();
                byte[] literal = literalSink.toByteArray();
                top.add(literal);
                literalSink = null;
                inContent = false;
                state = STATE_CODE;
              }
            else
              {
                literalSink.write(b);
                literalCount++;
              }
            break;
          case STATE_TEXT:         // human-readable text
            if (b == 0x0a)          // delimiter
              {
                byte[] tb = genericSink.toByteArray();
                genericSink.reset();
                response.text = new String(tb, DEFAULT_ENCODING);
                state = STATE_TAG;
                // mark bytes read
                mark(i);
                return response;
              }
            else if (b != 0x0d)     // ignore CR
              {
                genericSink.write(b);
              }
            break;
          }
      }
    // get more bytes
    buf = read(true);
    return next();
  }
  
}