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/* wydawca - automatic release submission daemon
   Copyright (C) 2011 Sergey Poznyakoff

   Wydawca is free software; you can redistribute it and/or modify it
   under the terms of the GNU General Public License as published by the
   Free Software Foundation; either version 3 of the License, or (at your
   option) any later version.

   Wydawca 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 General Public License for more details.

   You should have received a copy of the GNU General Public License along
   with wydawca. If not, see <http://www.gnu.org/licenses/>. */

#include "wydawca.h"

char const *simple_backup_suffix = "~";

static const char *
split_filename (char const *file, char **pdir)
{
  const char *p = strrchr (file, '/');

  if (!p)
    {
      *pdir = grecs_strdup (".");
      p = file;
    }
  else
    {
      size_t len = p - file; 
      char *dir = grecs_malloc (len + 1);
      memcpy (dir, file, len);
      dir[len] = 0;
      *pdir = dir;
      p++;
    }
  return p;
}

#define MINSUFSIZE 8
#define ISDIGIT(c) ('0' <= (c) && (c) <= '9')

static char *
get_backup_suffix (char const *file, enum backup_type type)
{
  char *dirname;
  const char *basename;
  size_t baselen;
  DIR *dir;
  struct dirent *ent;
  char *lastsuf = NULL;
  size_t lastsuflen = 0;
  size_t lastsufsize = 0;
  int carry;
  char *newsuf;
  char *q;
      
  if (type == simple_backups)
    return grecs_strdup (simple_backup_suffix);

  basename = split_filename (file, &dirname);
  baselen = strlen (basename);
  dir = opendir (dirname);
  if (!dir)
    {
      int ec = errno;
      free (dirname);
      errno = ec;
      return NULL;
    }
  
  while ((ent = readdir (dir)))
    {
      size_t len = strlen (ent->d_name);
      const char *p;
      size_t suflen;
      
      if (len < baselen + 4 || memcmp (ent->d_name, basename, baselen))
	continue;
      p = ent->d_name + baselen;
      suflen = len - baselen;
      if (p[0] == '.' && p[1] == '~' && p[suflen-1] == '~' &&
	  (suflen > lastsuflen
	   || (suflen == lastsuflen &&
	       memcmp (p, lastsuf, lastsuflen) > 0)))
	{
	  carry = 1;
	  for (q = (char*) p + suflen - 2; q > p + 1 && ISDIGIT (*q); q--)
	    if (*q != '9')
	      carry = 0;
	  q++;
	  if (!ISDIGIT (*q))
	    continue;
	  
	  if (suflen > lastsufsize)
	    {
	      lastsufsize = suflen;
	      if (!lastsuf)
		{
		  if (lastsufsize < MINSUFSIZE)
		    lastsufsize = MINSUFSIZE;
		  lastsuf = grecs_malloc (lastsufsize);
		}
	      else
		lastsuf = grecs_realloc (lastsuf, lastsufsize);
	    }
	  memcpy (lastsuf, p, suflen);
	  lastsuflen = suflen;
	}
    }
  closedir (dir);
  free (dirname);

  if (lastsuf)
    {
      size_t newsuflen;
      
      newsuflen = lastsuflen + carry;
      newsuf = grecs_malloc (newsuflen + 1);
      newsuf[0] = '.';
      newsuf[1] = '~';
      newsuf[2] = '0';
      memcpy (newsuf + 2 + carry, lastsuf + 2, lastsuflen - 3);
      newsuf[newsuflen-1] = '~';
      newsuf[newsuflen] = 0;
      
      for (q = newsuf + newsuflen - 2; *q == '9'; q--)
	*q = '0';
      ++*q;
      free (lastsuf);
    }
  else if (type == numbered_existing_backups)
    newsuf = grecs_strdup (simple_backup_suffix);
  else
    newsuf = grecs_strdup (".~1~");
  return newsuf;
}

char *
find_backup_file_name (char const *file, enum backup_type type)
{
  size_t flen;
  char *suffix;
  char *newname;
  
  if (type == no_backups)
    {
      errno = 0;
      return NULL;
    }

  suffix = get_backup_suffix (file, type);
  if (!suffix)
    return NULL;
  flen = strlen (file);
  newname = grecs_malloc (flen + strlen (suffix) + 1);
  memcpy (newname, file, flen);
  strcpy (newname + flen, suffix);
  free (suffix);
  /* FIXME: Check newname length */
  return newname;
}

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