/*

  Copyright (C) 2010, 2011

  Rocky Bernstein <rocky@gnu.org>

  Diego 'Flameeyes' Pettenò 

  Thomas Schmitt

  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 3 of the License, 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.  If not, see <http://www.gnu.org/licenses/>.

*/

/*

  POSIX realpath if that's around, and something like it if not.

  To compile as a standalone program:

  gcc -Wall -g -I../.. -DHAVE_CONFIG_H -DSTANDALONE -o realpath realpath.c

*/

/*

  Make sure we handle:

  - resolve relative links like  /dev/cdrom -> sr2

  - abort on cyclic linking like /dev/cdrom -> /dev/cdrom

*/

#ifdef HAVE_CONFIG_H

# include "config.h"

# define __CDIO_CONFIG_H__ 1

#endif

#include <ctype.h>

#ifdef HAVE_STDLIB_H

# include <stdlib.h>

#endif

#ifdef HAVE_STDIO_H

# include <stdio.h>

#endif

#ifdef HAVE_STRING_H

# include <string.h>

#endif

#ifdef HAVE_UNISTD_H /* readlink */

# include <unistd.h>

#endif

#ifdef HAVE_INTTYPES_H

# include "inttypes.h"

#endif

#ifdef HAVE_LIMITS_H

# include <limits.h>

#endif

#ifndef PATH_MAX

#define PATH_MAX 4096

#endif

#include <cdio/util.h>

/*!  cdio_realpath() same as POSIX.1-2001 realpath if that's

around. If not we do poor-man's simulation of that behavior.  */

char *cdio_realpath (const char *psz_src_path, char *psz_resolved_path) {

#ifdef HAVE_REALPATH

  psz_resolved_path = realpath(psz_src_path, psz_resolved_path);

#elif defined(HAVE_READLINK)

  char tmp_src[PATH_MAX+1];

  char tmp_dst[PATH_MAX+1];

  char *p_adr;

  int i, len;

  const int loop_limit = 100;

  strcpy(tmp_src, psz_src_path);

  /* FIXME: 

     remove loop and change with stat before and after readlink 

     which looks direct symlink. Rely on errno to figure out other

     non-existent or looped symlinks. 

  */

  for(i = 0; i < loop_limit; i++) {

    len = readlink(tmp_src, tmp_dst, PATH_MAX);

    if (-1 == len) {

	/* Right now we expect a "not symlink" error. However after

	   we put in the stat() suggested above, there won't be a symlink

	   error and we should start reporting what the failure is.

	*/

	break;

    } else {

	tmp_dst[len] = '\0';

	if (tmp_dst[0] != '/') {

	    /* Take care of relative link like  /dev/cdrom -> sr2 */

	    p_adr = strrchr(tmp_src, '/');

	    if (p_adr != NULL) {

		strncpy(p_adr + 1, tmp_dst, PATH_MAX - (p_adr + 1 - tmp_src));

	    } else {

		strncpy(tmp_src, tmp_dst, PATH_MAX);

	    }

	} else {

	    strncpy(tmp_src, tmp_dst, PATH_MAX);

	}

	tmp_src[PATH_MAX - 1] = 0; /* strncpy() does not always set a 0 */

    }

  }

  strncpy(psz_resolved_path, tmp_src, PATH_MAX);

#else

  strncpy(psz_resolved_path, psz_src_path, PATH_MAX);

#endif

  return psz_resolved_path;

}

#ifdef STANDALONE

int main(int argc, char **argv)

{

  int i;

  char dest[PATH_MAX];

  if (argc < 2) {

    fprintf(stderr, "Usage: %s  path [path ...]\n", argv[0]);

    fprintf(stderr,

     "       Resolve symbolic links\n");

    exit(1);

  }

  for (i= 1; i < argc; i++) {

    dest[0] = 0;

    cdio_realpath (argv[i], dest);

    printf("%s -> %s\n", argv[i], dest);

  }

  exit(0);

}

#endif