/*	$NetBSD: backupfile.c,v 1.13 2003/07/30 08:51:04 itojun Exp $	*/

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

   This program is free software; you can redistribute it and/or modify
   it without restriction.

   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.  */

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

#include <sys/cdefs.h>
#ifndef lint
__RCSID("$NetBSD: backupfile.c,v 1.13 2003/07/30 08:51:04 itojun Exp $");
#endif /* not lint */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <sys/types.h>

#include "EXTERN.h"
#include "common.h"
#include "util.h"
#include "backupfile.h"

#include <dirent.h>
#ifdef direct
#undef direct
#endif
#define direct dirent
#define NLENGTH(direct) (strlen((direct)->d_name))

#ifndef isascii
#define ISDIGIT(c) (isdigit ((unsigned char) (c)))
#else
#define ISDIGIT(c) (isascii (c) && isdigit ((unsigned char)c))
#endif

#include <unistd.h>

#define REAL_DIR_ENTRY(dp) ((dp)->d_fileno != 0)

/* Which type of backup file names are generated. */
enum backup_type backup_type = none;

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

/* backupfile.c */
static int max_backup_version(char *, char *);
static char *make_version_name(char *, int);
static int version_number(char *, char *, size_t);
static char *concat(const char *, const char *);
static char *dirname(const char *);
static int argmatch(char *, const char **);
static void invalid_arg(const char *, const char *, int);

/* Return the name of the new backup file for file FILE,
   allocated with malloc.
   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(char *file)
{
  char *dir;
  char *base_versions;
  int highest_backup;

  if (backup_type == simple)
    return concat (file, simple_backup_suffix);
  base_versions = concat (basename (file), ".~");
  if (base_versions == 0)
    return 0;
  dir = dirname (file);
  if (dir == 0)
    {
      free (base_versions);
      return 0;
    }
  highest_backup = max_backup_version (base_versions, dir);
  free (base_versions);
  free (dir);
  if (backup_type == numbered_existing && highest_backup == 0)
    return concat (file, simple_backup_suffix);
  return make_version_name (file, highest_backup + 1);
}

/* 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.
   FILE should already have ".~" appended to it. */

static int
max_backup_version(char *file, char *dir)
{
  DIR *dirp;
  struct direct *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) || 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;
    }
  closedir (dirp);
  return highest_version;
}

/* Return a string, allocated with malloc, containing
   "FILE.~VERSION~". */

static char *
make_version_name(char *file, int version)
{
  char *backup_name;

  backup_name = xmalloc(strlen (file) + 16);
  snprintf(backup_name, strlen(file) + 16, "%s.~%d~", file, version);
  return backup_name;
}

/* If BACKUP is a numbered backup of BASE, return its version number;
   otherwise return 0.  BASE_LENGTH is the length of BASE.
   BASE should already have ".~" appended to it. */

static int
version_number(char *base, char *backup, size_t base_length)
{
  int version;
  char *p;
  
  version = 0;
  if (!strncmp (base, backup, base_length) && ISDIGIT (backup[base_length]))
    {
      for (p = &backup[base_length]; ISDIGIT (*p); ++p)
	version = version * 10 + *p - '0';
      if (p[0] != '~' || p[1])
	version = 0;
    }
  return version;
}

/* Return the newly-allocated concatenation of STR1 and STR2. */

static char *
concat(const char *str1, const char *str2)
{
  char *newstr;
  size_t l = strlen(str1) + strlen(str2) + 1;

  newstr = xmalloc(l);
  snprintf(newstr, l, "%s%s", str1, str2);
  return newstr;
}

/* Return NAME with any leading path stripped off.  */

char *
basename(char *name)
{
  char *base;

  base = strrchr (name, '/');
  return base ? base + 1 : name;
}

/* Return the leading directories part of PATH,
   allocated with malloc.
   Assumes that trailing slashes have already been
   removed.  */

static char *
dirname(const char *path)
{
  char *newpath;
  char *slash;
  size_t length;    /* Length of result, not including NUL. */

  slash = strrchr (path, '/');
  if (slash == 0)
	{
	  /* File is in the current directory.  */
	  path = ".";
	  length = 1;
	}
  else
	{
	  /* Remove any trailing slashes from result. */
	  while (slash > path && *slash == '/')
		--slash;

	  length = slash - path + 1;
	}
  newpath = xmalloc(length + 1);
  strncpy(newpath, path, length);
  newpath[length] = 0;
  return newpath;
}

/* If ARG is an unambiguous match for an element of the
   null-terminated array OPTLIST, return the index in OPTLIST
   of the matched element, else -1 if it does not match any element
   or -2 if it is ambiguous (is a prefix of more than one element). */

static int
argmatch(char *arg, const char **optlist)
{
  int i;			/* Temporary index in OPTLIST. */
  size_t arglen;		/* Length of ARG. */
  int matchind = -1;		/* Index of first nonexact match. */
  int ambiguous = 0;		/* If nonzero, multiple nonexact match(es). */
  
  arglen = strlen (arg);
  
  /* Test all elements for either exact match or abbreviated matches.  */
  for (i = 0; optlist[i]; i++)
    {
      if (!strncmp (optlist[i], arg, arglen))
	{
	  if (strlen (optlist[i]) == arglen)
	    /* Exact match found.  */
	    return i;
	  else if (matchind == -1)
	    /* First nonexact match found.  */
	    matchind = i;
	  else
	    /* Second nonexact match found.  */
	    ambiguous = 1;
	}
    }
  if (ambiguous)
    return -2;
  else
    return matchind;
}

/* Error reporting for argmatch.
   KIND is a description of the type of entity that was being matched.
   VALUE is the invalid value that was given.
   PROBLEM is the return value from argmatch. */

static void
invalid_arg(const char *kind, const char *value, int problem)
{
  fprintf (stderr, "patch: ");
  if (problem == -1)
    fprintf (stderr, "invalid");
  else				/* Assume -2. */
    fprintf (stderr, "ambiguous");
  fprintf (stderr, " %s `%s'\n", kind, value);
}

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

static 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(char *version)
{
  int i;

  if (version == 0 || *version == 0)
    return numbered_existing;
  i = argmatch (version, backup_args);
  if (i >= 0)
    return backup_types[i];
  invalid_arg ("version control type", version, i);
  exit (1);
  /* NOTREACHED */
}