/* This file is part of the KDE libraries
   Copyright (C) 2000-2005 David Faure <faure@kde.org>

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

   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.
*/

#include "kgzipfilter.h"

#include <time.h>
#include <zlib.h>
#include <kdebug.h>
#include <QtCore/QIODevice>


/* gzip flag byte */
#define ASCII_FLAG   0x01 /* bit 0 set: file probably ascii text */
#define HEAD_CRC     0x02 /* bit 1 set: header CRC present */
#define EXTRA_FIELD  0x04 /* bit 2 set: extra field present */
#define ORIG_NAME    0x08 /* bit 3 set: original file name present */
#define COMMENT      0x10 /* bit 4 set: file comment present */
#define RESERVED     0xE0 /* bits 5..7: reserved */

// #define DEBUG_GZIP

class KGzipFilter::Private
{
public:
    Private()
    {
        zStream.zalloc = (alloc_func)0;
        zStream.zfree = (free_func)0;
        zStream.opaque = (voidpf)0;
        headerWritten = false;
        footerWritten = false;
        compressed = false;
        mode = 0;
    }

    z_stream zStream;
    bool headerWritten;
    bool footerWritten;
    bool compressed;
    int mode;
    ulong crc;
};

KGzipFilter::KGzipFilter()
    : d(new Private)
{
}


KGzipFilter::~KGzipFilter()
{
    delete d;
}

void KGzipFilter::init( int mode )
{
    d->zStream.next_in = Z_NULL;
    d->zStream.avail_in = 0;
    if ( mode == QIODevice::ReadOnly )
    {
        int result = inflateInit2(&d->zStream, -MAX_WBITS); // windowBits is passed < 0 to suppress zlib header
        if ( result != Z_OK )
            kDebug(7005) << "inflateInit returned " << result;
        // No idea what to do with result :)
    } else if ( mode == QIODevice::WriteOnly )
    {
        int result = deflateInit2(&d->zStream, Z_DEFAULT_COMPRESSION, Z_DEFLATED, -MAX_WBITS, 8, Z_DEFAULT_STRATEGY); // same here
        if ( result != Z_OK )
            kDebug(7005) << "deflateInit returned " << result;
    } else {
        kWarning(7005) << "KGzipFilter: Unsupported mode " << mode << ". Only QIODevice::ReadOnly and QIODevice::WriteOnly supported";
    }
    d->mode = mode;
    d->compressed = true;
    d->headerWritten = false;
    d->footerWritten = false;
}

int KGzipFilter::mode() const
{
    return d->mode;
}

void KGzipFilter::terminate()
{
    if ( d->mode == QIODevice::ReadOnly )
    {
        int result = inflateEnd(&d->zStream);
        if ( result != Z_OK )
            kDebug(7005) << "inflateEnd returned " << result;
    } else if ( d->mode == QIODevice::WriteOnly )
    {
        int result = deflateEnd(&d->zStream);
        if ( result != Z_OK )
            kDebug(7005) << "deflateEnd returned " << result;
    }
}


void KGzipFilter::reset()
{
    if ( d->mode == QIODevice::ReadOnly )
    {
        int result = inflateReset(&d->zStream);
        if ( result != Z_OK )
            kDebug(7005) << "inflateReset returned " << result;
    } else if ( d->mode == QIODevice::WriteOnly ) {
        int result = deflateReset(&d->zStream);
        if ( result != Z_OK )
            kDebug(7005) << "deflateReset returned " << result;
        d->headerWritten = false;
        d->footerWritten = false;
    }
}

bool KGzipFilter::readHeader()
{
#ifdef DEBUG_GZIP
    kDebug(7005) << "avail=" << d->zStream.avail_in;
#endif
    // Assume not compressed until we successfully decode the header
    d->compressed = false;
    // Assume the first block of data contains the whole header.
    // The right way is to build this as a big state machine which
    // is a pain in the ass.
    // With 8K-blocks, we don't risk much anyway.
    Bytef *p = d->zStream.next_in;
    int i = d->zStream.avail_in;
    if ((i -= 10)  < 0) return false; // Need at least 10 bytes
#ifdef DEBUG_GZIP
    kDebug(7005) << "first byte is " << QString::number(*p,16);
#endif
    if (*p++ != 0x1f) return false; // GZip magic
#ifdef DEBUG_GZIP
    kDebug(7005) << "second byte is " << QString::number(*p,16);
#endif
    if (*p++ != 0x8b) return false;
    int method = *p++;
    int flags = *p++;
    if ((method != Z_DEFLATED) || (flags & RESERVED) != 0) return false;
    p += 6;
    if ((flags & EXTRA_FIELD) != 0) // skip extra field
    {
        if ((i -= 2) < 0) return false; // Need at least 2 bytes
        int len = *p++;
        len += (*p++) << 8;
        if ((i -= len) < 0) return false; // Need at least len bytes
        p += len;
    }
    if ((flags & ORIG_NAME) != 0) // skip original file name
    {
#ifdef DEBUG_GZIP
        kDebug(7005) << "ORIG_NAME=" << (char*)p;
#endif
        while( (i > 0) && (*p))
        {
            i--; p++;
        }
        if (--i <= 0) return false;
        p++;
    }
    if ((flags & COMMENT) != 0) // skip comment
    {
        while( (i > 0) && (*p))
        {
            i--; p++;
        }
        if (--i <= 0) return false;
        p++;
    }
    if ((flags & HEAD_CRC) != 0) // skip the header crc
    {
        if ((i-=2) < 0) return false;
        p += 2;
    }

    d->zStream.avail_in = i;
    d->zStream.next_in = p;
    d->compressed = true;
#ifdef DEBUG_GZIP
    kDebug(7005) << "header OK";
#endif
    return true;
}

/* Output a 16 bit value, lsb first */
#define put_short(w) \
    *p++ = (uchar) ((w) & 0xff); \
    *p++ = (uchar) ((ushort)(w) >> 8);

/* Output a 32 bit value to the bit stream, lsb first */
#define put_long(n) \
    put_short((n) & 0xffff); \
    put_short(((ulong)(n)) >> 16);

bool KGzipFilter::writeHeader( const QByteArray & fileName )
{
    Bytef *p = d->zStream.next_out;
    int i = d->zStream.avail_out;
    *p++ = 0x1f;
    *p++ = 0x8b;
    *p++ = Z_DEFLATED;
    *p++ = ORIG_NAME;
    put_long( time( 0L ) ); // Modification time (in unix format)
    *p++ = 0; // Extra flags (2=max compress, 4=fastest compress)
    *p++ = 3; // Unix

    uint len = fileName.length();
    for ( uint j = 0 ; j < len ; ++j )
        *p++ = fileName[j];
    *p++ = 0;
    int headerSize = p - d->zStream.next_out;
    i -= headerSize;
    Q_ASSERT(i>0);
    d->crc = crc32(0L, Z_NULL, 0);
    d->zStream.next_out = p;
    d->zStream.avail_out = i;
    d->headerWritten = true;
    return true;
}

void KGzipFilter::writeFooter()
{
    Q_ASSERT( d->headerWritten );
    if (!d->headerWritten) kDebug() << kBacktrace();
    Q_ASSERT(!d->footerWritten);
    Bytef *p = d->zStream.next_out;
    int i = d->zStream.avail_out;
    //kDebug(7005) << "avail_out=" << i << "writing CRC=" << QString::number(d->crc, 16) << "at p=" << p;
    put_long( d->crc );
    //kDebug(7005) << "writing totalin=" << d->zStream.total_in << "at p=" << p;
    put_long( d->zStream.total_in );
    i -= p - d->zStream.next_out;
    d->zStream.next_out = p;
    d->zStream.avail_out = i;
    d->footerWritten = true;
}

void KGzipFilter::setOutBuffer( char * data, uint maxlen )
{
    d->zStream.avail_out = maxlen;
    d->zStream.next_out = (Bytef *) data;
}
void KGzipFilter::setInBuffer( const char * data, uint size )
{
#ifdef DEBUG_GZIP
    kDebug(7005) << "avail_in=" << size;
#endif
    d->zStream.avail_in = size;
    d->zStream.next_in = (Bytef*) data;
}
int KGzipFilter::inBufferAvailable() const
{
    return d->zStream.avail_in;
}
int KGzipFilter::outBufferAvailable() const
{
    return d->zStream.avail_out;
}

KGzipFilter::Result KGzipFilter::uncompress_noop()
{
    // I'm not sure we really need support for that (uncompressed streams),
    // but why not, it can't hurt to have it. One case I can think of is someone
    // naming a tar file "blah.tar.gz" :-)
    if ( d->zStream.avail_in > 0 )
    {
        int n = (d->zStream.avail_in < d->zStream.avail_out) ? d->zStream.avail_in : d->zStream.avail_out;
        memcpy( d->zStream.next_out, d->zStream.next_in, n );
        d->zStream.avail_out -= n;
        d->zStream.next_in += n;
        d->zStream.avail_in -= n;
        return KFilterBase::Ok;
    } else
        return KFilterBase::End;
}

KGzipFilter::Result KGzipFilter::uncompress()
{
    Q_ASSERT ( d->mode == QIODevice::ReadOnly );
    if ( d->compressed )
    {
#ifdef DEBUG_GZIP
        kDebug(7005) << "Calling inflate with avail_in=" << inBufferAvailable() << " avail_out=" << outBufferAvailable();
        kDebug(7005) << "    next_in=" << d->zStream.next_in;
#endif
        int result = inflate(&d->zStream, Z_SYNC_FLUSH);
#ifdef DEBUG_GZIP
        kDebug(7005) << " -> inflate returned " << result;
        kDebug(7005) << "Now avail_in=" << inBufferAvailable() << " avail_out=" << outBufferAvailable();
        kDebug(7005) << "    next_in=" << d->zStream.next_in;
#else
        if ( result != Z_OK && result != Z_STREAM_END )
            kDebug(7005) << "Warning: inflate() returned " << result;
#endif
        return ( result == Z_OK ? KFilterBase::Ok : ( result == Z_STREAM_END ? KFilterBase::End : KFilterBase::Error ) );
    } else
        return uncompress_noop();
}

KGzipFilter::Result KGzipFilter::compress( bool finish )
{
    Q_ASSERT ( d->compressed );
    Q_ASSERT ( d->mode == QIODevice::WriteOnly );

    Bytef* p = d->zStream.next_in;
    ulong len = d->zStream.avail_in;
#ifdef DEBUG_GZIP
    kDebug(7005) << "  calling deflate with avail_in=" << inBufferAvailable() << " avail_out=" << outBufferAvailable();
#endif
    const int result = deflate(&d->zStream, finish ? Z_FINISH : Z_NO_FLUSH);
    if ( result != Z_OK && result != Z_STREAM_END )
        kDebug(7005) << "  deflate returned " << result;
    if ( d->headerWritten )
    {
        //kDebug(7005) << "Computing CRC for the next " << len - d->zStream.avail_in << " bytes";
        d->crc = crc32(d->crc, p, len - d->zStream.avail_in);
    }
    KGzipFilter::Result callerResult = result == Z_OK ? KFilterBase::Ok : (Z_STREAM_END ? KFilterBase::End : KFilterBase::Error);

    if (result == Z_STREAM_END && d->headerWritten && !d->footerWritten) {
        if (d->zStream.avail_out >= 8 /*footer size*/) {
            //kDebug(7005) << "finished, write footer";
            writeFooter();
        } else {
            // No room to write the footer (#157706/#188415), we'll have to do it on the next pass.
            //kDebug(7005) << "finished, but no room for footer yet";
            callerResult = KFilterBase::Ok;
        }
    }
    return callerResult;
}
