/*
    kmime_codec_uuencode.cpp

    This file is part of KMime, the KDE internet mail/usenet news message library.
    Copyright (c) 2002 Marc Mutz <mutz@kde.org>

    KMime is free software; you can redistribute it and/or modify it
    under the terms of the GNU General Public License, version 2, as
    published by the Free Software Foundation.

    KMime 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., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA

    In addition, as a special exception, the copyright holders give
    permission to link the code of this library with any edition of
    the TQt library by Trolltech AS, Norway (or with modified versions
    of TQt that use the same license as TQt), and distribute linked
    combinations including the two.  You must obey the GNU General
    Public License in all respects for all of the code used other than
    TQt.  If you modify this file, you may extend this exception to
    your version of the file, but you are not obligated to do so.  If
    you do not wish to do so, delete this exception statement from
    your version.
*/

#include "kmime_codec_uuencode.h"

#include <kdebug.h>

#include <cassert>

using namespace KMime;

namespace KMime {


class UUDecoder : public Decoder {
  uint mStepNo;
  uchar mAnnouncedOctetCount; // (on current line)
  uchar mCurrentOctetCount; // (on current line)
  uchar mOutbits;
  bool mLastWasCRLF : 1;
  bool mSawBegin : 1;      // whether we already saw ^begin...
  uint mIntoBeginLine : 3; // count #chars we compared against "begin" 0..5
  bool mSawEnd : 1;        // whether we already saw ^end...
  uint mIntoEndLine : 2;   // count #chars we compared against "end" 0..3

  void searchForBegin( const char* & scursor, const char * const send );

protected:
  friend class UUCodec;
  UUDecoder( bool withCRLF=false )
    : Decoder( withCRLF ), mStepNo(0),
      mAnnouncedOctetCount(0), mCurrentOctetCount(0),
      mOutbits(0), mLastWasCRLF(true),
      mSawBegin(false), mIntoBeginLine(0),
      mSawEnd(false), mIntoEndLine(0) {}

public:
  virtual ~UUDecoder() {}

  bool decode( const char* & scursor, const char * const send,
	       char* & dcursor, const char * const dend );
  // ### really needs no finishing???
  bool finish( char* & /*dcursor*/, const char * const /*dend*/ ) { return true; }
};



Encoder * UUCodec::makeEncoder( bool ) const {
  return 0; // encoding not supported
}

Decoder * UUCodec::makeDecoder( bool withCRLF ) const {
  return new UUDecoder( withCRLF );
}


  /********************************************************/
  /********************************************************/
  /********************************************************/



void UUDecoder::searchForBegin( const char* & scursor, const char * const send ) {
  static const char begin[] = "begin\n";
  static const uint beginLength = 5; // sic!

  assert( !mSawBegin || mIntoBeginLine > 0 );

  while ( scursor != send ) {
    uchar ch = *scursor++;
    if ( ch == begin[mIntoBeginLine] ) {
      if ( mIntoBeginLine < beginLength ) {
	// found another char
	++mIntoBeginLine;
	if ( mIntoBeginLine == beginLength )
	  mSawBegin = true; // "begin" complete, now search the next \n...
      } else /* mIntoBeginLine == beginLength */ {
	// found '\n': begin line complete
	mLastWasCRLF = true;
	mIntoBeginLine = 0;
	return;
      }
    } else if ( mSawBegin ) {
      // OK, skip stuff until the next \n
    } else {
      kdWarning() << "UUDecoder: garbage before \"begin\", resetting parser"
		  << endl;
      mIntoBeginLine = 0;
    }
  }

}


// uuencoding just shifts all 6-bit octets by 32 (SP/' '), except NUL,
// which gets mapped to 0x60
static inline uchar uuDecode( uchar c ) {
  return ( c - ' ' ) // undo shift and
         & 0x3F;     // map 0x40 (0x60-' ') to 0...
}


bool UUDecoder::decode( const char* & scursor, const char * const send,
			char* & dcursor, const char * const dend )
{
  // First, check whether we still need to find the "begin" line:
  if ( !mSawBegin || mIntoBeginLine != 0 )
    searchForBegin( scursor, send );
  // or if we are past the end line:
  else if ( mSawEnd ) {
    scursor = send; // do nothing anymore...
    return true;
  }

  while ( dcursor != dend && scursor != send ) {
    uchar ch = *scursor++;
    uchar value;

    // Check whether we need to look for the "end" line:
    if ( mIntoEndLine > 0 ) {
      static const char end[] = "end";
      static const uint endLength = 3;

      if ( ch == end[mIntoEndLine] ) {
	++mIntoEndLine;
	if ( mIntoEndLine == endLength ) {
	  mSawEnd = true;
	  scursor = send; // shortcut to the end
	  return true;
	}
	continue;
      } else {
	kdWarning() << "UUDecoder: invalid line octet count looks like \"end\" (mIntoEndLine = " << mIntoEndLine << " )!" << endl;
	mIntoEndLine = 0;
	// fall through...
      }
    }

    // Normal parsing:

    // The first char of a line is an encoding of the length of the
    // current line. We simply ignore it:
    if ( mLastWasCRLF ) {
      // reset char-per-line counter:
      mLastWasCRLF = false;
      mCurrentOctetCount = 0;

      // try to decode the chars-on-this-line announcement:
      if ( ch == 'e' ) // maybe the beginning of the "end"? ;-)
	mIntoEndLine = 1;
      else if ( ch > 0x60 )
	{} // ### invalid line length char: what shall we do??
      else if ( ch > ' ' )
	mAnnouncedOctetCount = uuDecode( ch );
      else if ( ch == '\n' )
	mLastWasCRLF = true; // oops, empty line

      continue;
    }

    // try converting ch to a 6-bit value:
    if ( ch > 0x60 )
      continue; // invalid char
    else if ( ch > ' ' )
      value = uuDecode( ch );
    else if ( ch == '\n' ) { // line end
      mLastWasCRLF = true;
      continue;
    } else
      continue;

    // add the new bits to the output stream and flush full octets:    
    switch ( mStepNo ) {
    case 0:
      mOutbits = value << 2;
      break;
    case 1:
      if ( mCurrentOctetCount < mAnnouncedOctetCount )
	*dcursor++ = (char)(mOutbits | value >> 4);
      ++mCurrentOctetCount;
      mOutbits = value << 4;
      break;
    case 2:
      if ( mCurrentOctetCount < mAnnouncedOctetCount )
	*dcursor++ = (char)(mOutbits | value >> 2);
      ++mCurrentOctetCount;
      mOutbits = value << 6;
      break;
    case 3:
      if ( mCurrentOctetCount < mAnnouncedOctetCount )
	*dcursor++ = (char)(mOutbits | value);
      ++mCurrentOctetCount;
      mOutbits = 0;
      break;
    default:
      assert( 0 );
    }
    mStepNo = (mStepNo + 1) % 4;

    // check whether we ran over the announced octet count for this line:
    kdWarning( mCurrentOctetCount == mAnnouncedOctetCount + 1 ) 
      << "UUDecoder: mismatch between announced ("
      << mAnnouncedOctetCount << ") and actual line octet count!" << endl;

  }

  // return false when caller should call us again:
  return (scursor == send);
} // UUDecoder::decode()


} // namespace KMime
