/* backupfile.c -- make Emacs style backup file names
   Copyright (C) 1990-1997, 1998 Free Software Foundation, Inc.

   This program 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 2, or (at your option)
   any later version.

   This program 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 this program; see the file COPYING.
   If not, write to the Free Software Foundation,
   59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */

/* Written by David MacKenzie <djm@gnu.ai.mit.edu>.
   Some algorithms adapted from GNU Emacs. */

#if HAVE_CONFIG_H
# include <config.h>
#endif

/* FIXME!! */
#ifdef __DJGPP__
#define HAVE_DOS_FILE_NAMES 1
#endif

#ifndef HAVE_DOS_FILE_NAMES
#define HAVE_DOS_FILE_NAMES 0
#endif

#ifdef __DJGPP__
#define ISUPPER(c)  ((c) >= 'A' && (c) <= 'Z')
#define FILECHARCASEEQ(c1,c2) \
  ((ISUPPER(c1) ? tolower(c1) : (c1)) == (ISUPPER(c2) ? tolower(c2) : (c2)))
#endif

#ifndef FILECHARCASEEQ
#define FILECHARCASEEQ(c1,c2)  ((c1) == (c2))
#endif

char *basename (const char *);	/* FIXME! */

#include <argmatch.h>
#include <backupfile.h>

#include <stdio.h>
#include <ctype.h>
#include <sys/types.h>
#if HAVE_STRING_H
# include <string.h>
#else
# include <strings.h>
#endif

#if HAVE_DIRENT_H
# include <dirent.h>
# define NLENGTH(direct) strlen ((direct)->d_name)
#else
# define dirent direct
# define NLENGTH(direct) ((size_t) (direct)->d_namlen)
# if HAVE_SYS_NDIR_H
#  include <sys/ndir.h>
# endif
# if HAVE_SYS_DIR_H
#  include <sys/dir.h>
# endif
# if HAVE_NDIR_H
#  include <ndir.h>
# endif
#endif

#if CLOSEDIR_VOID
/* Fake a return value. */
# define CLOSEDIR(d) (closedir (d), 0)
#else
# define CLOSEDIR(d) closedir (d)
#endif

#if STDC_HEADERS
# include <stdlib.h>
#else
char *malloc ();
#endif

#if HAVE_DIRENT_H || HAVE_NDIR_H || HAVE_SYS_DIR_H || HAVE_SYS_NDIR_H
# define HAVE_DIR 1
#else
# define HAVE_DIR 0
#endif

#if HAVE_LIMITS_H
# include <limits.h>
#endif
#ifndef CHAR_BIT
# define CHAR_BIT 8
#endif
/* Upper bound on the string length of an integer converted to string.
   302 / 1000 is ceil (log10 (2.0)).  Subtract 1 for the sign bit;
   add 1 for integer division truncation; add 1 more for a minus sign.  */
#define INT_STRLEN_BOUND(t) ((sizeof (t) * CHAR_BIT - 1) * 302 / 1000 + 2)

/* ISDIGIT differs from isdigit, as follows:
   - Its arg may be any int or unsigned int; it need not be an unsigned char.
   - It's guaranteed to evaluate its argument exactly once.
   - It's typically faster.
   Posix 1003.2-1992 section 2.5.2.1 page 50 lines 1556-1558 says that
   only '0' through '9' are digits.  Prefer ISDIGIT to isdigit unless
   it's important to use the locale's definition of `digit' even when the
   host does not conform to Posix.  */
#define ISDIGIT(c) ((unsigned) (c) - '0' <= 9)

#if D_INO_IN_DIRENT
# define REAL_DIR_ENTRY(dp) ((dp)->d_ino != 0)
#else
# define REAL_DIR_ENTRY(dp) 1
#endif

/* The extension added to file names to produce a simple (as opposed
   to numbered) backup file name. */
const char *simple_backup_suffix = "~";

static int max_backup_version PARAMS ((const char *, const char *));
static int version_number PARAMS ((const char *, const char *, size_t));

/* Return the name of the new backup file for file FILE,
   allocated with malloc.  Return 0 if out of memory.
   FILE must not end with a '/' unless it is the root directory.
   Do not call this function if backup_type == none. */

char *
find_backup_file_name (const char *file, enum backup_type backup_type)
{
  size_t backup_suffix_size_max;
  size_t file_len = strlen (file);
  size_t numbered_suffix_size_max = INT_STRLEN_BOUND (int) + 4;
  char *s;
  const char *suffix = simple_backup_suffix;

  /* Allow room for simple or `.~N~' backups.  */
  backup_suffix_size_max = strlen (simple_backup_suffix) + 1;
  if (HAVE_DIR && backup_suffix_size_max < numbered_suffix_size_max)
    backup_suffix_size_max = numbered_suffix_size_max;

  s = malloc (file_len + backup_suffix_size_max + numbered_suffix_size_max);
  if (s)
    {
      strcpy (s, file);

#if HAVE_DIR
      if (backup_type != simple)
	{
	  int highest_backup;
	  size_t dir_len = basename (s) - s;

	  strcpy (s + dir_len, ".");
	  highest_backup = max_backup_version (file + dir_len, s);
	  if (! (backup_type == numbered_existing && highest_backup == 0))
	    {
	      char *numbered_suffix = s + (file_len + backup_suffix_size_max);
	      sprintf (numbered_suffix, ".~%d~", highest_backup + 1);
	      suffix = numbered_suffix;
	    }
	  strcpy (s, file);
	}
#endif /* HAVE_DIR */

      addext (s, suffix, '~');
    }
  return s;
}

#if HAVE_DIR

/* Return the number of the highest-numbered backup file for file
   FILE in directory DIR.  If there are no numbered backups
   of FILE in DIR, or an error occurs reading DIR, return 0.
   */

static int
max_backup_version (const char *file, const char *dir)
{
  DIR *dirp;
  struct dirent *dp;
  int highest_version;
  int this_version;
  size_t file_name_length;

  dirp = opendir (dir);
  if (!dirp)
    return 0;

  highest_version = 0;
  file_name_length = strlen (file);

  while ((dp = readdir (dirp)) != 0)
    {
      if (!REAL_DIR_ENTRY (dp)
	  || (! HAVE_DOS_FILE_NAMES && NLENGTH (dp) < file_name_length + 4)
	  || NLENGTH (dp) < file_name_length)
	continue;

      this_version = version_number (file, dp->d_name, file_name_length);
      if (this_version > highest_version)
	highest_version = this_version;
    }
  if (CLOSEDIR (dirp))
    return 0;
  return highest_version;
}

/* If BACKUP is a numbered backup of BASE, return its version number;
   otherwise return 0.  BASE_LENGTH is the length of BASE.
   */

static int
version_number (const char *base, const char *backup, size_t base_length)
{
  int version;
  const char *s = base;
  const char *s_end = base + base_length;
  const char *p = backup;

  version = 0;

  /* This could use `strncmp', but under HAVE_DOS_FILE_NAMES the two
     files need not compare equal to the full extent of BASE_LENGTH.  */
  if (! FILECHARCASEEQ (*p, *s))
    return 0;
  for ( ; s < s_end && FILECHARCASEEQ (*p, *s); p++, s++)
    ;
  if (p[0] == '.' && p[1] == '~')
    p += 2;
  else if (! HAVE_DOS_FILE_NAMES)
    return 0;
  else if (*p == '.')	/* the case of foo.99~ */
    p++;

  for ( ; ISDIGIT (*p); ++p)
    version = version * 10 + *p - '0';
  if (p[0] != '~' || p[1])
    version = 0;
  return version;
}
#endif /* HAVE_DIR */

static const char * const backup_args[] =
{
  "never", "simple", "nil", "existing", "t", "numbered", 0
};

static const enum backup_type backup_types[] =
{
  simple, simple, numbered_existing, numbered_existing, numbered, numbered
};

/* Return the type of backup indicated by VERSION.
   Unique abbreviations are accepted. */

enum backup_type
get_version (const char *version)
{
  int i;

  if (version == 0 || *version == 0)
    return numbered_existing;
  i = argmatch (version, backup_args);
  if (i < 0)
    {
      invalid_arg ("version control type", version, i);
      exit (2);
    }
  return backup_types[i];
}

#ifdef TEST

#include <stdio.h>

char *program_name;

int main (int argc, char *argv[])
{
  program_name = argv[0];

  if (argc > 1)
    {
      printf ("Simple: `%s' will be backed up on `%s'\n",
	      argv[1],
	      find_backup_file_name (argv[1], backup_types[0]));
      printf ("Numbered-existing: `%s' will be backed up on `%s'\n",
	      argv[1],
	      find_backup_file_name (argv[1], backup_types[2]));
      printf ("Numbered: `%s' will be backed up on `%s'\n",
	      argv[1],
	      find_backup_file_name (argv[1], backup_types[4]));
    }
  return 0;
}

#endif

