/**********************************************************************
 *
 *   rfccodecs.cpp - handler for various rfc/mime encodings
 *   Copyright (C) 2000 s.carstens@gmx.de
 *
 *   This library is free software; you can redistribute it and/or
 *   modify it under the terms of the GNU Library General Public
 *   License as published by the Free Software Foundation; either
 *   version 2 of the License, or (at your option) any later version.
 *
 *   This library 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
 *   Library General Public License for more details.
 *
 *   You should have received a copy of the GNU Library General Public License
 *   along with this library; see the file COPYING.LIB.  If not, write to
 *   the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 *   Boston, MA 02110-1301, USA.
 *
 *********************************************************************/
/**
 * @file
 * This file is part of the IMAP support library and defines the
 * RfcCodecs class.
 *
 * @brief
 * Defines the RfcCodecs class.
 *
 * @author Sven Carstens
 */

#include "rfccodecs.h"

#include <ctype.h>
#include <sys/types.h>

#include <stdio.h>
#include <stdlib.h>

#include <QtCore/QTextCodec>
#include <QtCore/QBuffer>
#include <QtCore/QRegExp>
#include <QtCore/QByteArray>
#include <QtCore/QLatin1Char>
#include <kcodecs.h>

using namespace KIMAP;

// This part taken from rfc 2192 IMAP URL Scheme. C. Newman. September 1997.
// adapted to QT-Toolkit by Sven Carstens <s.carstens@gmx.de> 2000

//@cond PRIVATE
static const unsigned char base64chars[] =
  "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";
#define UNDEFINED 64
#define MAXLINE  76
static const char especials[17] = "()<>@,;:\"/[]?.= ";

/* UTF16 definitions */
#define UTF16MASK       0x03FFUL
#define UTF16SHIFT      10
#define UTF16BASE       0x10000UL
#define UTF16HIGHSTART  0xD800UL
#define UTF16HIGHEND    0xDBFFUL
#define UTF16LOSTART    0xDC00UL
#define UTF16LOEND      0xDFFFUL
//@endcond

//-----------------------------------------------------------------------------
QByteArray KIMAP::decodeImapFolderName( const QByteArray &inSrc )
{
  unsigned char c, i, bitcount;
  unsigned long ucs4, utf16, bitbuf;
  unsigned char base64[256], utf8[6];
  unsigned int srcPtr = 0;
  QByteArray dst;
  QByteArray src = inSrc;
  uint srcLen = inSrc.length();

  /* initialize modified base64 decoding table */
  memset( base64, UNDEFINED, sizeof( base64 ) );
  for ( i = 0; i < sizeof( base64chars ); ++i ) {
    base64[(int)base64chars[i]] = i;
  }

  /* loop until end of string */
  while ( srcPtr < srcLen ) {
    c = src[srcPtr++];
    /* deal with literal characters and &- */
    if ( c != '&' || src[srcPtr] == '-' ) {
      /* encode literally */
      dst += c;
      /* skip over the '-' if this is an &- sequence */
      if ( c == '&' ) {
        srcPtr++;
      }
    } else {
      /* convert modified UTF-7 -> UTF-16 -> UCS-4 -> UTF-8 -> HEX */
      bitbuf = 0;
      bitcount = 0;
      ucs4 = 0;
      while ( ( c = base64[(unsigned char)src[srcPtr]] ) != UNDEFINED ) {
        ++srcPtr;
        bitbuf = ( bitbuf << 6 ) | c;
        bitcount += 6;
        /* enough bits for a UTF-16 character? */
        if ( bitcount >= 16 ) {
          bitcount -= 16;
          utf16 = ( bitcount ? bitbuf >> bitcount : bitbuf ) & 0xffff;
          /* convert UTF16 to UCS4 */
          if ( utf16 >= UTF16HIGHSTART && utf16 <= UTF16HIGHEND ) {
            ucs4 = ( utf16 - UTF16HIGHSTART ) << UTF16SHIFT;
            continue;
          } else if ( utf16 >= UTF16LOSTART && utf16 <= UTF16LOEND ) {
            ucs4 += utf16 - UTF16LOSTART + UTF16BASE;
          } else {
            ucs4 = utf16;
          }
          /* convert UTF-16 range of UCS4 to UTF-8 */
          if ( ucs4 <= 0x7fUL ) {
            utf8[0] = ucs4;
            i = 1;
          } else if ( ucs4 <= 0x7ffUL ) {
            utf8[0] = 0xc0 | ( ucs4 >> 6 );
            utf8[1] = 0x80 | ( ucs4 & 0x3f );
            i = 2;
          } else if ( ucs4 <= 0xffffUL ) {
            utf8[0] = 0xe0 | ( ucs4 >> 12 );
            utf8[1] = 0x80 | ( ( ucs4 >> 6 ) & 0x3f );
            utf8[2] = 0x80 | ( ucs4 & 0x3f );
            i = 3;
          } else {
            utf8[0] = 0xf0 | ( ucs4 >> 18 );
            utf8[1] = 0x80 | ( ( ucs4 >> 12 ) & 0x3f );
            utf8[2] = 0x80 | ( ( ucs4 >> 6 ) & 0x3f );
            utf8[3] = 0x80 | ( ucs4 & 0x3f );
            i = 4;
          }
          /* copy it */
          for ( c = 0; c < i; ++c ) {
            dst += utf8[c];
          }
        }
      }
      /* skip over trailing '-' in modified UTF-7 encoding */
      if ( src[srcPtr] == '-' ) {
        ++srcPtr;
      }
    }
  }
  return dst;
}

QString KIMAP::decodeImapFolderName( const QString &inSrc )
{
  return QString::fromUtf8( decodeImapFolderName( inSrc.toUtf8() ).data() );
}

//-----------------------------------------------------------------------------

QByteArray KIMAP::quoteIMAP( const QByteArray &src )
{
  uint len = src.length();
  QByteArray result;
  result.reserve( 2 * len );
  for ( unsigned int i = 0; i < len; i++ ) {
    if ( src[i] == '"' || src[i] == '\\' ) {
      result += '\\';
    }
    result += src[i];
  }
  result.squeeze();
  return result;
}

QString KIMAP::quoteIMAP( const QString &src )
{
  uint len = src.length();
  QString result;
  result.reserve( 2 * len );
  for ( unsigned int i = 0; i < len; i++ ) {
    if ( src[i] == QLatin1Char('"') || src[i] == QLatin1Char('\\') ) {
      result += QLatin1Char('\\');
    }
    result += src[i];
  }
  //result.squeeze(); - unnecessary and slow
  return result;
}

//-----------------------------------------------------------------------------
QString KIMAP::encodeImapFolderName( const QString &inSrc )
{
  return QString::fromUtf8( encodeImapFolderName( inSrc.toUtf8() ).data() );
}

QByteArray KIMAP::encodeImapFolderName( const QByteArray &inSrc )
{
  unsigned int utf8pos, utf8total, c, utf7mode, bitstogo, utf16flag;
  unsigned int ucs4, bitbuf;
  QByteArray src = inSrc;
  QByteArray dst;

  int srcPtr = 0;
  utf7mode = 0;
  utf8total = 0;
  bitstogo = 0;
  utf8pos = 0;
  bitbuf = 0;
  ucs4 = 0;
  while ( srcPtr < src.length () ) {
    c = (unsigned char)src[srcPtr++];
    /* normal character? */
    if ( c >= ' ' && c <= '~' ) {
      /* switch out of UTF-7 mode */
      if ( utf7mode ) {
        if ( bitstogo ) {
          dst += base64chars[( bitbuf << ( 6 - bitstogo ) ) & 0x3F];
          bitstogo = 0;
        }
        dst += '-';
        utf7mode = 0;
      }
      dst += c;
      /* encode '&' as '&-' */
      if ( c == '&' ) {
        dst += '-';
      }
      continue;
    }
    /* switch to UTF-7 mode */
    if ( !utf7mode ) {
      dst += '&';
      utf7mode = 1;
    }
    /* Encode US-ASCII characters as themselves */
    if ( c < 0x80 ) {
      ucs4 = c;
      utf8total = 1;
    } else if ( utf8total ) {
      /* save UTF8 bits into UCS4 */
      ucs4 = ( ucs4 << 6 ) | ( c & 0x3FUL );
      if ( ++utf8pos < utf8total ) {
        continue;
      }
    } else {
      utf8pos = 1;
      if ( c < 0xE0 ) {
        utf8total = 2;
        ucs4 = c & 0x1F;
      } else if ( c < 0xF0 ) {
        utf8total = 3;
        ucs4 = c & 0x0F;
      } else {
        /* NOTE: can't convert UTF8 sequences longer than 4 */
        utf8total = 4;
        ucs4 = c & 0x03;
      }
      continue;
    }
    /* loop to split ucs4 into two utf16 chars if necessary */
    utf8total = 0;
    do
    {
      if ( ucs4 >= UTF16BASE ) {
        ucs4 -= UTF16BASE;
        bitbuf =
          ( bitbuf << 16 ) | ( ( ucs4 >> UTF16SHIFT ) + UTF16HIGHSTART );
        ucs4 = ( ucs4 & UTF16MASK ) + UTF16LOSTART;
        utf16flag = 1;
      } else {
        bitbuf = ( bitbuf << 16 ) | ucs4;
        utf16flag = 0;
      }
      bitstogo += 16;
      /* spew out base64 */
      while ( bitstogo >= 6 ) {
        bitstogo -= 6;
        dst +=
          base64chars[( bitstogo ? ( bitbuf >> bitstogo ) : bitbuf ) & 0x3F];
      }
    }
    while ( utf16flag );
  }
  /* if in UTF-7 mode, finish in ASCII */
  if ( utf7mode ) {
    if ( bitstogo ) {
      dst += base64chars[( bitbuf << ( 6 - bitstogo ) ) & 0x3F];
    }
    dst += '-';
  }
  return quoteIMAP( dst );
}

//-----------------------------------------------------------------------------
QTextCodec *KIMAP::codecForName( const QString &str )
{
  if ( str.isEmpty () ) {
    return 0;
  }
  return QTextCodec::codecForName ( str.toLower ().
                                    replace ( QLatin1String("windows"), QLatin1String("cp") ).toLatin1 () );
}

//-----------------------------------------------------------------------------
const QString KIMAP::decodeRFC2047String( const QString &str )
{
  QString throw_away;

  return decodeRFC2047String( str, throw_away );
}

//-----------------------------------------------------------------------------
const QString KIMAP::decodeRFC2047String( const QString &str,
                                          QString &charset )
{
  QString throw_away;

  return decodeRFC2047String( str, charset, throw_away );
}

//-----------------------------------------------------------------------------
const QString KIMAP::decodeRFC2047String( const QString &str,
                                          QString &charset,
                                          QString &language )
{
  //do we have a rfc string
  if ( !str.contains( QLatin1String("=?") ) ) {
    return str;
  }

  // FIXME get rid of the conversion?
  QByteArray aStr = str.toLatin1 ();  // QString.length() means Unicode chars
  QByteArray result;
  char *pos, *beg, *end, *mid = 0;
  QByteArray cstr;
  char encoding = 0, ch;
  bool valid;
  const int maxLen = 200;
  int i;

//  result.truncate(aStr.length());
  for ( pos = aStr.data (); *pos; pos++ ) {
    if ( pos[0] != '=' || pos[1] != '?' ) {
      result += *pos;
      continue;
    }
    beg = pos + 2;
    end = beg;
    valid = true;
    // parse charset name
    for ( i = 2, pos += 2;
          i < maxLen &&
              ( *pos != '?' && ( ispunct( *pos ) || isalnum ( *pos ) ) );
          i++ ) {
      pos++;
    }
    if ( *pos != '?' || i < 4 || i >= maxLen ) {
      valid = false;
    } else {
      charset = QLatin1String(QByteArray( beg, i - 1 ));  // -2 + 1 for the zero
      int pt = charset.lastIndexOf( QLatin1Char('*') );
      if ( pt != -1 ) {
        // save language for later usage
        language = charset.right( charset.length () - pt - 1 );

        // tie off language as defined in rfc2047
        charset.truncate( pt );
      }
      // get encoding and check delimiting question marks
      encoding = toupper( pos[1] );
      if ( pos[2] != '?' ||
           ( encoding != 'Q' && encoding != 'B' &&
             encoding != 'q' && encoding != 'b' ) ) {
        valid = false;
      }
      pos += 3;
      i += 3;
//  kDebug() << "Charset:" << charset << "- Language:" << language << "-'" << pos << "'";
    }
    if ( valid ) {
      mid = pos;
      // search for end of encoded part
      while ( i < maxLen && *pos && !( *pos == '?' && *( pos + 1 ) == '=' ) ) {
        i++;
        pos++;
      }
      end = pos + 2;//end now points to the first char after the encoded string
      if ( i >= maxLen || !*pos ) {
        valid = false;
      }
    }
    if ( valid ) {
      ch = *pos;
      *pos = '\0';
      cstr = QByteArray (mid).left( (int)( mid - pos - 1 ) );
      if ( encoding == 'Q' ) {
        // decode quoted printable text
        for ( i = cstr.length () - 1; i >= 0; --i ) {
          if ( cstr[i] == '_' ) {
            cstr[i] = ' ';
          }
        }
//    kDebug() << "before QP '"
//    << cstr << "'";
        cstr = KCodecs::quotedPrintableDecode( cstr );
//    kDebug() << "after QP '"
//    << cstr << "'";
      } else {
        // decode base64 text
        cstr = QByteArray::fromBase64( cstr );
      }
      *pos = ch;
      int len = cstr.length();
      for ( i = 0; i < len; ++i ) {
        result += cstr[i];
      }

      pos = end - 1;
    } else {
//    kDebug() << "invalid";
      //result += "=?";
      //pos = beg -1; // because pos gets increased shortly afterwards
      pos = beg - 2;
      result += *pos++;
      result += *pos;
    }
  }
  if ( !charset.isEmpty () ) {
    QTextCodec *aCodec = codecForName( QLatin1String(charset.toLatin1 ()) );
    if ( aCodec ) {
//    kDebug() << "Codec is" << aCodec->name();
      return aCodec->toUnicode( result );
    }
  }
  return QLatin1String(result);
}

//-----------------------------------------------------------------------------
const QString KIMAP::encodeRFC2047String( const QString &str )
{
  return QLatin1String(encodeRFC2047String( str.toLatin1() ));
}

//-----------------------------------------------------------------------------
const QByteArray KIMAP::encodeRFC2047String( const QByteArray &str )
{
  if ( str.isEmpty () ) {
    return str;
  }

  const signed char *latin =
    reinterpret_cast<const signed char *>
    ( str.data() ), *l, *start, *stop;
  char hexcode;
  int numQuotes, i;
  int rptr = 0;
  // My stats show this number results in 12 resize() out of 73,000
  int resultLen = 3 * str.length() / 2;
  QByteArray result( resultLen, '\0' );

  while ( *latin ) {
    l = latin;
    start = latin;
    while ( *l ) {
      if ( *l == 32 ) {
        start = l + 1;
      }
      if ( *l < 0 ) {
        break;
      }
      l++;
    }
    if ( *l ) {
      numQuotes = 1;
      while ( *l ) {
        /* The encoded word must be limited to 75 character */
        for ( i = 0; i < 16; ++i ) {
          if ( *l == especials[i] ) {
            numQuotes++;
          }
        }
        if ( *l < 0 ) {
          numQuotes++;
        }
        /* Stop after 58 = 75 - 17 characters or at "<user@host..." */
        if ( l - start + 2 * numQuotes >= 58 || *l == 60 ) {
          break;
        }
        l++;
      }
      if ( *l ) {
        stop = l - 1;
        while ( stop >= start && *stop != 32 ) {
          stop--;
        }
        if ( stop <= start ) {
          stop = l;
        }
      } else {
        stop = l;
      }
      if ( resultLen - rptr - 1 <= start -  latin + 1 + 16 ) {
        // =?iso-88...
        resultLen += ( start - latin + 1 ) * 2 + 20; // more space
        result.resize( resultLen );
      }
      while ( latin < start ) {
        result[rptr++] = *latin;
        latin++;
      }
      result.replace( rptr, 15, "=?iso-8859-1?q?" );
      rptr += 15;
      if ( resultLen - rptr - 1 <= 3 * ( stop - latin + 1 ) ) {
        resultLen += ( stop - latin + 1 ) * 4 + 20; // more space
        result.resize( resultLen );
      }
      while ( latin < stop ) {
        // can add up to 3 chars/iteration
        numQuotes = 0;
        for ( i = 0; i < 16; ++i ) {
          if ( *latin == especials[i] ) {
            numQuotes = 1;
          }
        }
        if ( *latin < 0 ) {
          numQuotes = 1;
        }
        if ( numQuotes ) {
          result[rptr++] = '=';
          hexcode = ( ( *latin & 0xF0 ) >> 4 ) + 48;
          if ( hexcode >= 58 ) {
            hexcode += 7;
          }
          result[rptr++] = hexcode;
          hexcode = ( *latin & 0x0F ) + 48;
          if ( hexcode >= 58 ) {
            hexcode += 7;
          }
          result[rptr++] = hexcode;
        } else {
          result[rptr++] = *latin;
        }
        latin++;
      }
      result[rptr++] = '?';
      result[rptr++] = '=';
    } else {
      while ( *latin ) {
        if ( rptr == resultLen - 1 ) {
          resultLen += 30;
          result.resize( resultLen );
        }
        result[rptr++] = *latin;
        latin++;
      }
    }
  }
  result[rptr] = 0;
  return result;
}

//-----------------------------------------------------------------------------
const QString KIMAP::encodeRFC2231String( const QString &str )
{
  if ( str.isEmpty () ) {
    return str;
  }

  signed char *latin = (signed char *)calloc( 1, str.length () + 1 );
  char *latin_us = (char *)latin;
  strcpy( latin_us, str.toLatin1 () );
  signed char *l = latin;
  char hexcode;
  int i;
  bool quote;
  while ( *l ) {
    if ( *l < 0 ) {
      break;
    }
    l++;
  }
  if ( !*l ) {
    free( latin );
    return str;
  }
  QByteArray result;
  l = latin;
  while ( *l ) {
    quote = *l < 0;
    for ( i = 0; i < 16; ++i ) {
      if ( *l == especials[i] ) {
        quote = true;
      }
    }
    if ( quote ) {
      result += '%';
      hexcode = ( ( *l & 0xF0 ) >> 4 ) + 48;
      if ( hexcode >= 58 ) {
        hexcode += 7;
      }
      result += hexcode;
      hexcode = ( *l & 0x0F ) + 48;
      if ( hexcode >= 58 ) {
        hexcode += 7;
      }
      result += hexcode;
    } else {
      result += *l;
    }
    l++;
  }
  free( latin );
  return QLatin1String(result);
}

//-----------------------------------------------------------------------------
const QString KIMAP::decodeRFC2231String( const QString &str )
{
  int p = str.indexOf ( QLatin1Char('\'') );

  //see if it is an rfc string
  if ( p < 0 ) {
    return str;
  }

  int l = str.lastIndexOf( QLatin1Char('\'') );

  //second is language
  if ( p >= l ) {
    return str;
  }

  //first is charset or empty
  //QString charset = str.left ( p );
  QString st = str.mid ( l + 1 );
  //QString language = str.mid ( p + 1, l - p - 1 );

  //kDebug() << "Charset:" << charset << "Language:" << language;

  char ch, ch2;
  p = 0;
  while ( p < (int) st.length () ) {
    if ( st.at( p ) == 37 ) {
      ch = st.at( p + 1 ).toLatin1 () - 48;
      if ( ch > 16 ) {
        ch -= 7;
      }
      ch2 = st.at( p + 2 ).toLatin1 () - 48;
      if ( ch2 > 16 ) {
        ch2 -= 7;
      }
      st.replace( p, 1, ch * 16 + ch2 );
      st.remove ( p + 1, 2 );
    }
    p++;
  }
  return st;
}