/*
 * This file Copyright (C) 2009 Charles Kerr <charles@transmissionbt.com>
 *
 * This file is licensed by the GPL version 2.  Works owned by the
 * Transmission project are granted a special exemption to clause 2(b)
 * so that the bulk of its code can remain under the MIT license.
 * This exemption does not extend to derived works not owned by
 * the Transmission project.
 *
 * $Id:$
 */

#include <assert.h>
#include <event.h> /* struct evbuffer */

#include "transmission.h"
#include "bencode.h"
#include "crypto.h"
#include "magnet.h"
#include "metainfo.h"
#include "torrent.h"
#include "torrent-magnet.h"
#include "utils.h"
#include "web.h"

#define dbgmsg( tor, ... ) \
    do { \
        if( tr_deepLoggingIsActive( ) ) \
            tr_deepLog( __FILE__, __LINE__, tor->info.name, __VA_ARGS__ ); \
    } while( 0 )

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

enum
{
    /* don't ask for the same metadata piece more than this often */
    MIN_REPEAT_INTERVAL_SECS = 3
};

struct metadata_node
{
    time_t requestedAt;
    int piece;
};

struct tr_incomplete_metadata
{
    uint8_t * metadata;
    int metadata_size;
    int pieceCount;

    /** sorted from least to most recently requested */
    struct metadata_node * piecesNeeded;
    int piecesNeededCount;
};

static void
incompleteMetadataFree( struct tr_incomplete_metadata * m )
{
    tr_free( m->metadata );
    tr_free( m->piecesNeeded );
    tr_free( m );
}

void
tr_torrentSetMetadataSizeHint( tr_torrent * tor, int size )
{
    if( !tr_torrentHasMetadata( tor ) )
    {
        if( tor->incompleteMetadata == NULL )
        {
            int i;
            struct tr_incomplete_metadata * m;
            int n = ( size + ( METADATA_PIECE_SIZE - 1 ) ) / METADATA_PIECE_SIZE;
            dbgmsg( tor, "there are %d pieces", n );

            m = tr_new( struct tr_incomplete_metadata, 1 );
            m->pieceCount = n;
            m->metadata = tr_new( uint8_t, size );
            m->metadata_size = size;
            m->piecesNeededCount = n;
            m->piecesNeeded = tr_new( struct metadata_node, n );

            for( i=0; i<n; ++i ) {
                m->piecesNeeded[i].piece = i;
                m->piecesNeeded[i].requestedAt = 0;
            }

            tor->incompleteMetadata = m;
        }
    }
}

void*
tr_torrentGetMetadataPiece( const tr_torrent * tor, int piece, int * len )
{
    char * ret = NULL;

    assert( tr_isTorrent( tor ) );
    assert( piece >= 0 );
    assert( len != NULL );

    if( tor->infoDictLength > 0 )
    {
        FILE * fp = fopen( tor->info.torrent, "rb" );
        if( fp != NULL )
        {
            const int offset = piece  * METADATA_PIECE_SIZE;

            if( !fseek( fp, tor->infoDictOffset + offset, SEEK_SET ) )
            {
                const int l = offset + METADATA_PIECE_SIZE <= tor->infoDictLength
                            ? METADATA_PIECE_SIZE
                            : tor->infoDictLength - offset;
                char * buf = tr_new( char, l );
                const int n = fread( buf, 1, l, fp );
                if( n != l )
                {
                    *len = l;
                    ret = buf;
                    buf = NULL;
                }

                tr_free( buf );
            }

            fclose( fp );
        }
    }

    return ret;
}

void
tr_torrentSetMetadataPiece( tr_torrent  * tor,
                            int           piece,
                            const void  * data,
                            int           len )
{
    int i;
    struct tr_incomplete_metadata * m;
    const int offset = piece * METADATA_PIECE_SIZE;

    assert( tr_isTorrent( tor ) );

    dbgmsg( tor, "got metadata piece %d", piece );

    /* are we set up to download metadata? */
    m = tor->incompleteMetadata;
    if( m == NULL )
        return;

    /* does this data pass the smell test? */
    if( offset + len > m->metadata_size )
        return;

    /* do we need this piece? */
    for( i=0; i<m->piecesNeededCount; ++i )
        if( m->piecesNeeded[i].piece == piece )
            break;
    if( i==m->piecesNeededCount )
        return;

    memcpy( m->metadata + offset, data, len );

    tr_removeElementFromArray( m->piecesNeeded, i,
                               sizeof( struct metadata_node ),
                               m->piecesNeededCount-- );

    dbgmsg( tor, "saving metainfo piece %d... %d remain", piece, m->piecesNeededCount );

    /* are we done? */
    if( m->piecesNeededCount == 0 )
    {
        tr_bool success = FALSE;
        uint8_t sha1[SHA_DIGEST_LENGTH];
        dbgmsg( tor, "metainfo piece %d was the last one", piece );
        tr_sha1( sha1, m->metadata, m->metadata_size, NULL );
        if( !memcmp( sha1, tor->info.hash, SHA_DIGEST_LENGTH ) )
        {
            int err;
            tr_benc dict;
            struct evbuffer * buf = evbuffer_new( );
            dbgmsg( tor, "metadata checksum passed!  (length: %d)", (int)m->metadata_size );

            /* add a wrapper dictionary to the benc.
             * include the announce-list too,
             * so we can save it in the .torrent for future sessions */
            evbuffer_add_printf( buf, "d" );
            evbuffer_add_printf( buf, "13:announce-list" );
            evbuffer_add_printf( buf, "l" );
            for( i=0; i<tor->info.trackerCount; ++i ) {
                const char * url = tor->info.trackers[i].announce;
                evbuffer_add_printf( buf, "l%zu:%se", strlen( url ), url );
            }
            evbuffer_add_printf( buf, "e" );
            evbuffer_add_printf( buf, "4:info" );
            evbuffer_add( buf, m->metadata, m->metadata_size );
            evbuffer_add_printf( buf, "e" );

            /* does it parse? */
            err = tr_bencLoad( EVBUFFER_DATA( buf ), EVBUFFER_LENGTH( buf ), &dict, NULL );
            dbgmsg( tor, "err is %d", err );
            if( !err )
            {
                if( tr_metainfoParse( tor->session,
                                      &tor->info,
                                      &tor->infoDictLength,
                                      &tor->infoDictOffset,
                                      &dict ) )
                {
                    const char * path = tor->info.torrent;
                    dbgmsg( tor, "saving completed metadata to \"%s\"", path );

                    success = TRUE;
                    tr_torrentGotNewInfoDict( tor );

                    tr_bencToFile( &dict, TR_FMT_BENC, path );
                    tr_sessionSetTorrentFile( tor->session,
                                              tor->info.hashString, path );
                    tr_torrentSetDirty( tor );
                }

                tr_bencFree( &dict );
            }

            evbuffer_free( buf );
        }

        if( success )
        {
            incompleteMetadataFree( tor->incompleteMetadata );
            tor->incompleteMetadata = NULL;
        }
        else /* drat. */
        {
            const int n = m->pieceCount;
            for( i=0; i<n; ++i ) {
                m->piecesNeeded[i].piece = i;
                m->piecesNeeded[i].requestedAt = 0;
            }
            m->piecesNeededCount = n;
            dbgmsg( tor, "metadata error; trying again. %d pieces left", n );
        }
    }
}

tr_bool
tr_torrentGetNextMetadataRequest( tr_torrent * tor, time_t now, int * setme_piece )
{
    tr_bool have_request = FALSE;
    struct tr_incomplete_metadata * m;

    assert( tr_isTorrent( tor ) );

    m = tor->incompleteMetadata;

    if( ( m != NULL )
        && ( m->piecesNeededCount > 0 )
        && ( m->piecesNeeded[0].requestedAt + MIN_REPEAT_INTERVAL_SECS < now ) )
    {
        int i;
        const int piece = m->piecesNeeded[0].piece;

        tr_removeElementFromArray( m->piecesNeeded, 0,
                                   sizeof( struct metadata_node ),
                                   m->piecesNeededCount-- );

        i = m->piecesNeededCount++;
        m->piecesNeeded[i].piece = piece;
        m->piecesNeeded[i].requestedAt = now;

        dbgmsg( tor, "next piece to request: %d", piece );
        *setme_piece = piece;
        have_request = TRUE;
    }

    return have_request;
}

float
tr_torrentGetMetadataPercent( const tr_torrent * tor )
{
    float ret;

    if( tr_torrentHasMetadata( tor ) )
        ret = 1.0;
    else {
        const struct tr_incomplete_metadata * m = tor->incompleteMetadata;
        if( m == NULL )
            ret = 0.0;
        else
            ret = (m->pieceCount - m->piecesNeededCount) / (float)m->pieceCount;
    }

    return ret;
}