/*
 * 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 "log.h"
#include "session.h"
#include "makemeta.h"
#include "platform.h" /* threads, locks */
#include "utils.h" /* buildpath */
#include "variant.h"
#include "version.h"

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

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

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

  sb.st_size = 0;

  buf = tr_buildPath (dir, base, NULL);
  i = stat (buf, &sb);
  if (i)
    {
      tr_logAddError (_("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);

  tr_metaInfoBuilderSetPieceSize (ret, bestPieceSize (ret->totalSize));

  return ret;
}

void
tr_metaInfoBuilderSetPieceSize (tr_metainfo_builder * b,
                                uint32_t              bytes)
{
  b->pieceSize = bytes;

  b->pieceCount = (int)(b->totalSize / b->pieceSize);
  if (b->totalSize % b->pieceSize)
    ++b->pieceCount;
}


void
tr_metaInfoBuilderFree (tr_metainfo_builder * builder)
{
  if (builder)
    {
      int i;
      tr_file_index_t t;

      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)
{
  char * base;
  uint8_t * pch;

  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 = true;
}

/***
****
****  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,
                 bool                    isPrivate)
{
  int i;
  tr_lock * lock;

  assert (tr_isBool (isPrivate));

  /* 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 = false;
  builder->result = 0;
  builder->isDone = false;
  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);
}