/*
 * This file Copyright (C) Mnemosyne LLC
 *
 * 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 <errno.h>
#include <stdio.h> /* FILE, stderr */
#include <stdlib.h> /* qsort */
#include <string.h> /* strcmp, strlen */

#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h> /* read () */
#include <dirent.h>

#include <event2/util.h> /* evutil_ascii_strcasecmp () */

#include "transmission.h"
#include "crypto.h" /* tr_sha1 */
#include "fdlimit.h" /* tr_open_file_for_scanning () */
#include "session.h"
#include "makemeta.h"
#include "platform.h" /* threads, locks */
#include "utils.h" /* buildpath */
#include "variant.h"
#include "version.h"

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

struct FileList
{
    struct FileList *  next;
    uint64_t           size;
    char *             filename;
};

static struct FileList*
getFiles (const char *      dir,
          const char *      base,
          struct FileList * list)
{
    int         i;
    char        * buf;
    struct stat sb;
    DIR *       odir = NULL;

    sb.st_size = 0;

    buf = tr_buildPath (dir, base, NULL);
    i = stat (buf, &sb);
    if (i)
    {
        tr_err (_("Torrent Creator is skipping file \"%s\": %s"),
                buf, tr_strerror (errno));
        tr_free (buf);
        return list;
    }

    if (S_ISDIR (sb.st_mode) && ((odir = opendir (buf))))
    {
        struct dirent *d;
        for (d = readdir (odir); d != NULL; d = readdir (odir))
            if (d->d_name && d->d_name[0] != '.') /* skip dotfiles */
                list = getFiles (buf, d->d_name, list);
        closedir (odir);
    }
    else if (S_ISREG (sb.st_mode) && (sb.st_size > 0))
    {
        struct FileList * node = tr_new (struct FileList, 1);
        node->size = sb.st_size;
        node->filename = tr_strdup (buf);
        node->next = list;
        list = node;
    }

    tr_free (buf);
    return list;
}

static uint32_t
bestPieceSize (uint64_t totalSize)
{
    const uint32_t KiB = 1024;
    const uint32_t MiB = 1048576;
    const uint32_t GiB = 1073741824;

    if (totalSize >= (2 * GiB)) return   2 * MiB;
    if (totalSize >= (1 * GiB)) return   1 * MiB;
    if (totalSize >= (512 * MiB)) return 512 * KiB;
    if (totalSize >= (350 * MiB)) return 256 * KiB;
    if (totalSize >= (150 * MiB)) return 128 * KiB;
    if (totalSize >= (50 * MiB)) return  64 * KiB;
    return 32 * KiB;  /* less than 50 meg */
}

static int
builderFileCompare (const void * va, const void * vb)
{
    const tr_metainfo_builder_file * a = va;
    const tr_metainfo_builder_file * b = vb;

    return evutil_ascii_strcasecmp (a->filename, b->filename);
}

tr_metainfo_builder*
tr_metaInfoBuilderCreate (const char * topFileArg)
{
    int i;
    struct FileList * files;
    struct FileList * walk;
    char topFile[TR_PATH_MAX];
    tr_metainfo_builder * ret = tr_new0 (tr_metainfo_builder, 1);

    tr_realpath (topFileArg, topFile);

    ret->top = tr_strdup (topFile);

    {
        struct stat sb;
        stat (topFile, &sb);
        ret->isSingleFile = !S_ISDIR (sb.st_mode);
    }

    /* build a list of files containing topFile and,
       if it's a directory, all of its children */
    {
        char * dir = tr_dirname (topFile);
        char * base = tr_basename (topFile);
        files = getFiles (dir, base, NULL);
        tr_free (base);
        tr_free (dir);
    }

    for (walk = files; walk != NULL; walk = walk->next)
        ++ret->fileCount;

    ret->files = tr_new0 (tr_metainfo_builder_file, ret->fileCount);

    for (i = 0, walk = files; walk != NULL; ++i)
    {
        struct FileList *          tmp = walk;
        tr_metainfo_builder_file * file = &ret->files[i];
        walk = walk->next;
        file->filename = tmp->filename;
        file->size = tmp->size;
        ret->totalSize += tmp->size;
        tr_free (tmp);
    }

    qsort (ret->files,
           ret->fileCount,
           sizeof (tr_metainfo_builder_file),
           builderFileCompare);

    ret->pieceSize = bestPieceSize (ret->totalSize);
    ret->pieceCount = (int)(ret->totalSize / ret->pieceSize);
    if (ret->totalSize % ret->pieceSize)
        ++ret->pieceCount;

    return ret;
}

void
tr_metaInfoBuilderFree (tr_metainfo_builder * builder)
{
    if (builder)
    {
        tr_file_index_t t;
        int             i;
        for (t = 0; t < builder->fileCount; ++t)
            tr_free (builder->files[t].filename);
        tr_free (builder->files);
        tr_free (builder->top);
        tr_free (builder->comment);
        for (i = 0; i < builder->trackerCount; ++i)
            tr_free (builder->trackers[i].announce);
        tr_free (builder->trackers);
        tr_free (builder->outputFile);
        tr_free (builder);
    }
}

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

static uint8_t*
getHashInfo (tr_metainfo_builder * b)
{
    uint32_t fileIndex = 0;
    uint8_t *ret = tr_new0 (uint8_t, SHA_DIGEST_LENGTH * b->pieceCount);
    uint8_t *walk = ret;
    uint8_t *buf;
    uint64_t totalRemain;
    uint64_t off = 0;
    int fd;

    if (!b->totalSize)
        return ret;

    buf = tr_valloc (b->pieceSize);
    b->pieceIndex = 0;
    totalRemain = b->totalSize;
    fd = tr_open_file_for_scanning (b->files[fileIndex].filename);
    if (fd < 0)
    {
        b->my_errno = errno;
        tr_strlcpy (b->errfile,
                    b->files[fileIndex].filename,
                    sizeof (b->errfile));
        b->result = TR_MAKEMETA_IO_READ;
        tr_free (buf);
        tr_free (ret);
        return NULL;
    }
    while (totalRemain)
    {
        uint8_t * bufptr = buf;
        const uint32_t thisPieceSize = (uint32_t) MIN (b->pieceSize, totalRemain);
        uint32_t leftInPiece = thisPieceSize;

        assert (b->pieceIndex < b->pieceCount);

        while (leftInPiece)
        {
            const size_t n_this_pass = (size_t) MIN ((b->files[fileIndex].size - off), leftInPiece);
            const ssize_t n_read = read (fd, bufptr, n_this_pass);
            bufptr += n_read;
            off += n_read;
            leftInPiece -= n_read;
            if (off == b->files[fileIndex].size)
            {
                off = 0;
                tr_close_file (fd);
                fd = -1;
                if (++fileIndex < b->fileCount)
                {
                    fd = tr_open_file_for_scanning (b->files[fileIndex].filename);
                    if (fd < 0)
                    {
                        b->my_errno = errno;
                        tr_strlcpy (b->errfile,
                                    b->files[fileIndex].filename,
                                    sizeof (b->errfile));
                        b->result = TR_MAKEMETA_IO_READ;
                        tr_free (buf);
                        tr_free (ret);
                        return NULL;
                    }
                }
            }
        }

        assert (bufptr - buf == (int)thisPieceSize);
        assert (leftInPiece == 0);
        tr_sha1 (walk, buf, thisPieceSize, NULL);
        walk += SHA_DIGEST_LENGTH;

        if (b->abortFlag)
        {
            b->result = TR_MAKEMETA_CANCELLED;
            break;
        }

        totalRemain -= thisPieceSize;
        ++b->pieceIndex;
    }

    assert (b->abortFlag
          || (walk - ret == (int)(SHA_DIGEST_LENGTH * b->pieceCount)));
    assert (b->abortFlag || !totalRemain);

    if (fd >= 0)
        tr_close_file (fd);

    tr_free (buf);
    return ret;
}

static void
getFileInfo (const char *                     topFile,
             const tr_metainfo_builder_file * file,
             tr_variant *                        uninitialized_length,
             tr_variant *                        uninitialized_path)
{
    size_t offset;

    /* get the file size */
    tr_variantInitInt (uninitialized_length, file->size);

    /* how much of file->filename to walk past */
    offset = strlen (topFile);
    if (offset>0 && topFile[offset-1]!=TR_PATH_DELIMITER)
        ++offset; /* +1 for the path delimiter */

    /* build the path list */
    tr_variantInitList (uninitialized_path, 0);
    if (strlen (file->filename) > offset) {
        char * filename = tr_strdup (file->filename + offset);
        char * walk = filename;
        const char * token;
        while ((token = tr_strsep (&walk, TR_PATH_DELIMITER_STR)))
            tr_variantListAddStr (uninitialized_path, token);
        tr_free (filename);
    }
}

static void
makeInfoDict (tr_variant *             dict,
              tr_metainfo_builder * builder)
{
    uint8_t * pch;
    char    * base;

    tr_variantDictReserve (dict, 5);

    if (builder->isSingleFile)
    {
        tr_variantDictAddInt (dict, TR_KEY_length, builder->files[0].size);
    }
    else /* root node is a directory */
    {
        uint32_t  i;
        tr_variant * list = tr_variantDictAddList (dict, TR_KEY_files,
                                             builder->fileCount);
        for (i = 0; i < builder->fileCount; ++i)
        {
            tr_variant * d = tr_variantListAddDict (list, 2);
            tr_variant * length = tr_variantDictAdd (d, TR_KEY_length);
            tr_variant * pathVal = tr_variantDictAdd (d, TR_KEY_path);
            getFileInfo (builder->top, &builder->files[i], length, pathVal);
        }
    }

    base = tr_basename (builder->top);
    tr_variantDictAddStr (dict, TR_KEY_name, base);
    tr_free (base);

    tr_variantDictAddInt (dict, TR_KEY_piece_length, builder->pieceSize);

    if ((pch = getHashInfo (builder)))
    {
        tr_variantDictAddRaw (dict, TR_KEY_pieces, pch,
                              SHA_DIGEST_LENGTH * builder->pieceCount);
        tr_free (pch);
    }

    tr_variantDictAddInt (dict, TR_KEY_private, builder->isPrivate ? 1 : 0);
}

static void
tr_realMakeMetaInfo (tr_metainfo_builder * builder)
{
    int     i;
    tr_variant top;

    /* allow an empty set, but if URLs *are* listed, verify them. #814, #971 */
    for (i = 0; i < builder->trackerCount && !builder->result; ++i) {
        if (!tr_urlIsValidTracker (builder->trackers[i].announce)) {
            tr_strlcpy (builder->errfile, builder->trackers[i].announce,
                       sizeof (builder->errfile));
            builder->result = TR_MAKEMETA_URL;
        }
    }

    tr_variantInitDict (&top, 6);

    if (!builder->fileCount || !builder->totalSize ||
        !builder->pieceSize || !builder->pieceCount)
    {
        builder->errfile[0] = '\0';
        builder->my_errno = ENOENT;
        builder->result = TR_MAKEMETA_IO_READ;
        builder->isDone = true;
    }

    if (!builder->result && builder->trackerCount)
    {
        int       prevTier = -1;
        tr_variant * tier = NULL;

        if (builder->trackerCount > 1)
        {
            tr_variant * annList = tr_variantDictAddList (&top, TR_KEY_announce_list, 0);
            for (i = 0; i < builder->trackerCount; ++i)
            {
                if (prevTier != builder->trackers[i].tier)
                {
                    prevTier = builder->trackers[i].tier;
                    tier = tr_variantListAddList (annList, 0);
                }
                tr_variantListAddStr (tier, builder->trackers[i].announce);
            }
        }

        tr_variantDictAddStr (&top, TR_KEY_announce, builder->trackers[0].announce);
    }

    if (!builder->result && !builder->abortFlag)
    {
        if (builder->comment && *builder->comment)
            tr_variantDictAddStr (&top, TR_KEY_comment, builder->comment);
        tr_variantDictAddStr (&top, TR_KEY_created_by,
                           TR_NAME "/" LONG_VERSION_STRING);
        tr_variantDictAddInt (&top, TR_KEY_creation_date, time (NULL));
        tr_variantDictAddStr (&top, TR_KEY_encoding, "UTF-8");
        makeInfoDict (tr_variantDictAddDict (&top, TR_KEY_info, 666), builder);
    }

    /* save the file */
    if (!builder->result && !builder->abortFlag)
    {
        if (tr_variantToFile (&top, TR_VARIANT_FMT_BENC, builder->outputFile))
        {
            builder->my_errno = errno;
            tr_strlcpy (builder->errfile, builder->outputFile,
                       sizeof (builder->errfile));
            builder->result = TR_MAKEMETA_IO_WRITE;
        }
    }

    /* cleanup */
    tr_variantFree (&top);
    if (builder->abortFlag)
        builder->result = TR_MAKEMETA_CANCELLED;
    builder->isDone = 1;
}

/***
****
****  A threaded builder queue
****
***/

static tr_metainfo_builder * queue = NULL;

static tr_thread *           workerThread = NULL;

static tr_lock*
getQueueLock (void)
{
    static tr_lock * lock = NULL;

    if (!lock)
        lock = tr_lockNew ();

    return lock;
}

static void
makeMetaWorkerFunc (void * unused UNUSED)
{
    for (;;)
    {
        tr_metainfo_builder * builder = NULL;

        /* find the next builder to process */
        tr_lock * lock = getQueueLock ();
        tr_lockLock (lock);
        if (queue)
        {
            builder = queue;
            queue = queue->nextBuilder;
        }
        tr_lockUnlock (lock);

        /* if no builders, this worker thread is done */
        if (builder == NULL)
            break;

        tr_realMakeMetaInfo (builder);
    }

    workerThread = NULL;
}

void
tr_makeMetaInfo (tr_metainfo_builder *   builder,
                 const char *            outputFile,
                 const tr_tracker_info * trackers,
                 int                     trackerCount,
                 const char *            comment,
                 int                     isPrivate)
{
    int       i;
    tr_lock * lock;

    /* free any variables from a previous run */
    for (i = 0; i < builder->trackerCount; ++i)
        tr_free (builder->trackers[i].announce);
    tr_free (builder->trackers);
    tr_free (builder->comment);
    tr_free (builder->outputFile);

    /* initialize the builder variables */
    builder->abortFlag = 0;
    builder->result = 0;
    builder->isDone = 0;
    builder->pieceIndex = 0;
    builder->trackerCount = trackerCount;
    builder->trackers = tr_new0 (tr_tracker_info, builder->trackerCount);
    for (i = 0; i < builder->trackerCount; ++i) {
        builder->trackers[i].tier = trackers[i].tier;
        builder->trackers[i].announce = tr_strdup (trackers[i].announce);
    }
    builder->comment = tr_strdup (comment);
    builder->isPrivate = isPrivate;
    if (outputFile && *outputFile)
        builder->outputFile = tr_strdup (outputFile);
    else
        builder->outputFile = tr_strdup_printf ("%s.torrent", builder->top);

    /* enqueue the builder */
    lock = getQueueLock ();
    tr_lockLock (lock);
    builder->nextBuilder = queue;
    queue = builder;
    if (!workerThread)
        workerThread = tr_threadNew (makeMetaWorkerFunc, NULL);
    tr_lockUnlock (lock);
}