/* xgetcwd.c: a from-scratch version of getwd.  Ideas from tcsh 5.20 source.

   Copyright 1992, 1994, 1996, 2008 Karl Berry.
   Copyright 2005 Olaf Weber.

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   This library 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
   Lesser General Public License for more details.

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

#include <kpathsea/config.h>

#if defined (HAVE_GETCWD) || defined (HAVE_GETWD)
#include <kpathsea/c-pathmx.h>
#else /* not HAVE_GETCWD && not HAVE_GETWD*/
#include <kpathsea/c-dir.h>
#include <kpathsea/xopendir.h>
#include <kpathsea/xstat.h>


static void
xchdir (string dirname)
{
    if (chdir(dirname) != 0)
        _PERROR(dirname);
}

#endif /* not HAVE_GETCWD && not HAVE_GETWD */


/* Return the pathname of the current directory, or give a fatal error.  */

string
xgetcwd (void)
{
    /* If the system provides getcwd, use it.  If not, use getwd if
       available.  But provide a way not to use getcwd: on some systems
       getcwd forks, which is expensive and may in fact be impossible for
       large programs like tex.  If your system needs this define and it
       is not detected by configure, let me know.
                                       -- Olaf Weber <infovore@xs4all.nl */
#if defined (HAVE_GETCWD) && !defined (GETCWD_FORKS)
    string path = (string)xmalloc(PATH_MAX + 1);

    if (getcwd (path, PATH_MAX + 1) == 0) {
        fprintf(stderr, "getcwd: %s", path);
        exit(EXIT_FAILURE);
    }

    return path;
#elif defined (HAVE_GETWD)
    string path = (string)xmalloc(PATH_MAX + 1);

    if (getwd (path) == 0) {
        fprintf(stderr, "getwd: %s", path);
        exit(EXIT_FAILURE);
    }

    return path;
#else /* not HAVE_GETCWD && not HAVE_GETWD */
    struct stat root_stat, cwd_stat;
    string cwd_path = (string)xmalloc(2); /* In case we assign "/" below.  */

    *cwd_path = 0;

    /* Find the inodes of the root and current directories.  */
    root_stat = xstat("/");
    cwd_stat  = xstat(".");

    /* Go up the directory hierarchy until we get to root, prepending each
       directory we pass through to `cwd_path'.  */
    while (!SAME_FILE_P(root_stat, cwd_stat)) {
        struct dirent *e;
        DIR *parent_dir;
        boolean found = false;

        xchdir("..");
        parent_dir = xopendir(".");

        /* Look through the parent directory for the entry with the same
           inode, so we can get its name.  */
        while ((e = readdir (parent_dir)) != NULL && !found) {
            struct stat test_stat;
            test_stat = xlstat(e->d_name);

            if (SAME_FILE_P(test_stat, cwd_stat)) {
                /* We've found it.  Prepend the pathname.  */
                string temp = cwd_path;
                cwd_path = concat3("/", e->d_name, cwd_path);
                free(temp);

                /* Set up to test the next parent.  */
                cwd_stat = xstat(".");

                /* Stop reading this directory.  */
                found = true;
            }
        }
        if (!found)
            LIB_FATAL2("No inode %d/device %d in parent directory",
                   cwd_stat.st_ino, cwd_stat.st_dev);

        xclosedir(parent_dir);
    }

    /* If the current directory is the root, cwd_path will be the empty
       string, and we will have not gone through the loop.  */
    if (*cwd_path == 0)
        strcpy(cwd_path, "/");
    else
        /* Go back to where we were.  */
        xchdir(cwd_path);

#ifdef DOSISH
    /* Prepend the drive letter to CWD_PATH, since this technique
       never tells us what the drive is.

       Note that on MS-DOS/MS-Windows, the branch that works around
       missing `getwd' will probably only work for DJGPP (which does
       have `getwd'), because only DJGPP reports meaningful
       st_ino numbers.  But someday, somebody might need this...  */
    {
        char drive[3];
        string temp = cwd_path;

        /* Make the drive letter lower-case, unless it is beyond Z: (yes,
           there ARE such drives, in case of Novell Netware on MS-DOS).  */
        drive[0] = root_stat.st_dev + (root_stat.st_dev < 26 ? 'a' : 'A');
        drive[1] = ':';
        drive[2] = '\0';

        cwd_path = concat(drive, cwd_path);
        free(temp);
    }
#endif

    return cwd_path;
#endif /* not HAVE_GETCWD && not HAVE_GETWD */
}