/******************************************************************************
 * $Id:$
 *
 * Copyright (c) 2005-2007 Transmission authors and contributors
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 *****************************************************************************/

/***********************************************************************
 * Fast resume
 ***********************************************************************
 * The format of the resume file is a 4 byte format version (currently 1),
 * followed by several variable-sized blocks of data.  Each block is
 * preceded by a 1 byte ID and a 4 byte length.  The currently recognized
 * IDs are defined below by the FR_ID_* macros.  The length does not include
 * the 5 bytes for the ID and length.
 *
 * The name of the resume file is "resume.<hash>-<tag>", although
 * older files with a name of "resume.<hash>" will be recognized if
 * the former doesn't exist.
 *
 * All values are stored in the native endianness. Moving a
 * libtransmission resume file from an architecture to another will not
 * work, although it will not hurt either (the version will be wrong,
 * so the resume file will not be read).
 **********************************************************************/

#include "transmission.h"
#include "fastresume.h"

/* time_t can be 32 or 64 bits... for consistency we'll hardwire 64 */ 
typedef uint64_t tr_time_t; 

/* deprecated */
#define FR_ID_PROGRESS_SLOTS    0x01
/* number of bytes downloaded */
#define FR_ID_DOWNLOADED        0x02
/* number of bytes uploaded */
#define FR_ID_UPLOADED          0x03
/* IPs and ports of connectable peers */
#define FR_ID_PEERS             0x04
/* progress data:
 *  - 4 bytes * number of files: mtimes of files
 *  - 1 bit * number of blocks: whether we have the block or not
 */
#define FR_ID_PROGRESS          0x05

/* macros for the length of various pieces of the progress data */
#define FR_MTIME_LEN( t ) \
  ( sizeof(tr_time_t) * (t)->info.fileCount )
#define FR_BLOCK_BITFIELD_LEN( t ) \
  ( ( (t)->blockCount + 7 ) / 8 )
#define FR_PROGRESS_LEN( t ) \
  ( FR_MTIME_LEN( t ) + FR_BLOCK_BITFIELD_LEN( t ) )

static void
fastResumeFileName( char * buf, size_t buflen, const tr_torrent_t * tor, int tag )
{
    const char * cacheDir = tr_getCacheDirectory ();
    const char * hash = tor->info.hashString;

    if( !tag )
    {
        tr_buildPath( buf, buflen, cacheDir, hash, NULL );
    }
    else
    {
        char base[1024];
        snprintf( base, sizeof(base), "%s-%s", hash, tor->handle->tag );
        tr_buildPath( buf, buflen, cacheDir, base, NULL );
    }
}

static tr_time_t*
getMTimes( const tr_torrent_t * tor, int * setme_n )
{
    int i;
    const int n = tor->info.fileCount;
    tr_time_t * m = calloc( n, sizeof(tr_time_t) );

    for( i=0; i<n; ++i ) {
        char fname[MAX_PATH_LENGTH];
        struct stat sb;
        tr_buildPath( fname, sizeof(fname),
                      tor->destination, tor->info.files[i].name, NULL );
        if ( !stat( fname, &sb ) && S_ISREG( sb.st_mode ) ) {
#ifdef SYS_DARWIN
            m[i] = sb.st_mtimespec.tv_sec;
#else
            m[i] = sb.st_mtime;
#endif
        }
    }

    *setme_n = n;
    return m;
}

static inline void fastResumeWriteData( uint8_t id, void * data, uint32_t size,
                                        uint32_t count, FILE * file )
{
    uint32_t  datalen = size * count;

    fwrite( &id, 1, 1, file );
    fwrite( &datalen, 4, 1, file );
    fwrite( data, size, count, file );
}

void fastResumeSave( const tr_torrent_t * tor )
{
    char      path[MAX_PATH_LENGTH];
    FILE    * file;
    const int version = 1;
    uint64_t  total;

    fastResumeFileName( path, sizeof path, tor, 1 );
    file = fopen( path, "w" );
    if( NULL == file ) {
        tr_err( "Couldn't open '%s' for writing", path );
        return;
    }
    
    /* Write format version */
    fwrite( &version, 4, 1, file );

    /* Write progress data */
    if (1) {
        int n;
        tr_time_t * mtimes;
        uint8_t * buf = malloc( FR_PROGRESS_LEN( tor ) );
        uint8_t * walk = buf;
        const tr_bitfield_t * bitfield;

        /* mtimes */
        mtimes = getMTimes( tor, &n );
        memcpy( walk, mtimes, n*sizeof(tr_time_t) );
        walk += n * sizeof(tr_time_t);

        /* completion bitfield */
        bitfield = tr_cpBlockBitfield( tor->completion );
        assert( (unsigned)FR_BLOCK_BITFIELD_LEN( tor ) == bitfield->len );
        memcpy( walk, bitfield->bits, bitfield->len );
        walk += bitfield->len;

        /* write it */
        assert( walk-buf == (int)FR_PROGRESS_LEN( tor ) );
        fastResumeWriteData( FR_ID_PROGRESS, buf, 1, walk-buf, file );

        /* cleanup */
        free( mtimes );
        free( buf );
    }

    /* Write download and upload totals */
    total = tor->downloadedCur + tor->downloadedPrev;
    fastResumeWriteData( FR_ID_DOWNLOADED, &total, 8, 1, file );
    total = tor->uploadedCur + tor->uploadedPrev;
    fastResumeWriteData( FR_ID_UPLOADED, &total, 8, 1, file );

    if( !( TR_FLAG_PRIVATE & tor->info.flags ) )
    {
        /* Write IPs and ports of connectable peers, if any */
        int size;
        uint8_t * buf = NULL;
        if( ( size = tr_peerGetConnectable( tor, &buf ) ) > 0 )
        {
            fastResumeWriteData( FR_ID_PEERS, buf, size, 1, file );
            free( buf );
        }
    }

    fclose( file );

    tr_dbg( "Resume file '%s' written", path );
}

static int
fastResumeLoadProgress( const tr_torrent_t  * tor,
                        tr_bitfield_t       * uncheckedPieces,
                        FILE                * file )
{
    const size_t len = FR_PROGRESS_LEN( tor );
    uint8_t * buf = calloc( len, 1 );
    uint8_t * walk = buf;

    if( len != fread( buf, 1, len, file ) ) {
        tr_inf( "Couldn't read from resume file" );
        free( buf );
        return TR_ERROR_IO_OTHER;
    }

    /* compare file mtimes */
    if (1) {
        int i, n;
        tr_time_t * curMTimes = getMTimes( tor, &n );
        const tr_time_t * oldMTimes = (const tr_time_t *) walk;
        for( i=0; i<n; ++i ) {
            if ( !curMTimes[i] || ( curMTimes[i]!=oldMTimes[i] ) ) {
                const tr_file_t * file = &tor->info.files[i];
                tr_inf( "File '%s' mtimes differ-- flaggin pieces [%d..%d]",
                        file->name, file->firstPiece, file->lastPiece);
                tr_bitfieldAddRange( uncheckedPieces, 
                                     file->firstPiece, file->lastPiece );
            }
        }
        free( curMTimes );
        walk += n * sizeof(tr_time_t);
    }

    /* get the completion bitfield */
    if (1) {
        tr_bitfield_t bitfield;
        memset( &bitfield, 0, sizeof bitfield );
        bitfield.len = FR_BLOCK_BITFIELD_LEN( tor );
        bitfield.bits = walk;
        tr_cpBlockBitfieldSet( tor->completion, &bitfield );
    }

    free( buf );
    return TR_OK;
}

static int
fastResumeLoadOld( tr_torrent_t   * tor,
                   tr_bitfield_t  * uncheckedPieces, 
                   FILE           * file )
{
    /* Check the size */
    const int size = 4 + FR_PROGRESS_LEN( tor );
    fseek( file, 0, SEEK_END );
    if( ftell( file ) != size )
    {
        tr_inf( "Wrong size for resume file (%d bytes, %d expected)",
                (int)ftell( file ), size );
        fclose( file );
        return 1;
    }

    /* load progress information */
    fseek( file, 4, SEEK_SET );
    if( fastResumeLoadProgress( tor, uncheckedPieces, file ) )
    {
        fclose( file );
        return 1;
    }

    fclose( file );

    tr_inf( "Fast resuming successful (version 0)" );
    
    return 0;
}

int
fastResumeLoad( tr_torrent_t   * tor,
                tr_bitfield_t  * uncheckedPieces )
{
    char      path[MAX_PATH_LENGTH];
    FILE    * file;
    int       version = 0;
    uint8_t   id;
    uint32_t  len;
    int       ret;

    assert( tor != NULL );
    assert( uncheckedPieces != NULL );

    /* Open resume file */
    fastResumeFileName( path, sizeof path, tor, 1 );
    file = fopen( path, "r" );
    if( NULL == file )
    {
        if( ENOENT == errno )
        {
            fastResumeFileName( path, sizeof path, tor, 0 );
            file = fopen( path, "r" );
            if( NULL != file )
            {
                goto good;
            }
            fastResumeFileName( path, sizeof path, tor, 1 );
        }
        tr_inf( "Could not open '%s' for reading", path );
        return 1;
    }
  good:
    tr_dbg( "Resume file '%s' loaded", path );

    /* Check format version */
    fread( &version, 4, 1, file );
    if( 0 == version )
    {
        return fastResumeLoadOld( tor, uncheckedPieces, file );
    }
    if( 1 != version )
    {
        tr_inf( "Resume file has version %d, not supported", version );
        fclose( file );
        return 1;
    }

    ret = 1;
    /* read each block of data */
    while( 1 == fread( &id, 1, 1, file ) && 1 == fread( &len, 4, 1, file ) )
    {
        switch( id )
        {
            case FR_ID_PROGRESS:
                /* read progress data */
                if( (uint32_t)FR_PROGRESS_LEN( tor ) == len )
                {
                    if( fastResumeLoadProgress( tor, uncheckedPieces, file ) )
                    {
                        if( feof( file ) || ferror( file ) )
                        {
                            fclose( file );
                            return 1;
                        }
                    }
                    else
                    {
                        ret = 0;
                    }
                    continue;
                }
                break;

            case FR_ID_DOWNLOADED:
                /* read download total */
                if( 8 == len)
                {
                    if( 1 != fread( &tor->downloadedPrev, 8, 1, file ) )
                    {
                        fclose( file );
                        return 1;
                    }
                    continue;
                }
                break;

            case FR_ID_UPLOADED:
                /* read upload total */
                if( 8 == len)
                {
                    if( 1 != fread( &tor->uploadedPrev, 8, 1, file ) )
                    {
                        fclose( file );
                        return 1;
                    }
                    continue;
                }
                break;

            case FR_ID_PEERS:
                if( !( TR_FLAG_PRIVATE & tor->info.flags ) )
                {
                    int used;
                    uint8_t * buf = malloc( len );
                    if( 1 != fread( buf, len, 1, file ) )
                    {
                        free( buf );
                        fclose( file );
                        return 1;
                    }
                    used = tr_torrentAddCompact( tor, TR_PEER_FROM_CACHE,
                                                 buf, len / 6 );
                    tr_dbg( "found %i peers in resume file, used %i",
                            len / 6, used );
                    free( buf );
                }
                continue;

            default:
                break;
        }

        /* if we didn't read the data, seek past it */
        tr_inf( "Skipping resume data type %02x, %u bytes", id, len );
        fseek( file, len, SEEK_CUR );
    }

    fclose( file );

    if( !ret )
    {
        tr_inf( "Fast resuming successful" );
    }
    
    return ret;
}

void
fastResumeRemove( tr_torrent_t * tor )
{
    char file[MAX_PATH_LENGTH];
    fastResumeFileName( file, sizeof file, tor, NULL != tor->handle->tag );
    
    if ( unlink( file ) )
    {
        tr_inf( "Removing fast resume file failed" );
    }
}