/* 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"

struct saved_dir
{
  struct saved_dir *prev;
  int fd;
  char *name;
};

struct saved_dir *dir_stack;

#ifndef O_SEARCH
# define O_SEARCH 0
#endif

char *
getcwd_alloc (void)
{
  size_t size = 0;
  char *buf = NULL;
  char *p;
  
  do
    {
      if (!buf)
	{
	  size = 64;
	  buf = malloc (size);
	}
      else
	{
	  char *np;
	  size_t ns = 2 * size;
	  if (ns < size)
	    {
	      free (buf);
	      errno = ENOMEM;
	      return NULL;
	    }
	  size = ns;
	  np = realloc (buf, size);
	  if (!np)
	    free (buf);
	  buf = np;
	}
      if (!buf)
	return NULL;
    }
  while ((p = getcwd (buf, size)) == NULL && errno == ERANGE);
  if (!p)
    {
      int ec = errno;
      free (buf);
      buf = NULL;
      errno = ec;
    }
  return buf;
}

static int
_save_dir (struct saved_dir *sd)
{
  int fd;
  
#ifdef HAVE_FCHDIR
  fd = open (".", O_SEARCH);
#else
  fd = -1;
#endif
  if (fd == -1)
    {
      sd->name = getcwd_alloc ();
      if (!sd->name)
	return errno;
    }
  else
    sd->name = NULL;
  sd->fd = fd;
  return 0;
}

static void
_drop_dir (struct saved_dir *sd)
{
  if (sd->fd != -1)
    close (sd->fd);
  free (sd->name);
  free (sd);
}

static int
_push_dir (struct saved_dir *sd, const char *dirname)
{
  int rc = _save_dir (sd);
  if (rc)
    return rc;
  if (dirname && chdir (dirname))
    {
      rc = errno;
      _drop_dir (sd);
      return rc;
    }
  return 0;
}

int
push_dir (const char *dirname)
{
  int rc;
  struct saved_dir *sd = malloc (sizeof (*sd));
  
  if (!sd)
    return errno;
  rc = _push_dir (sd, dirname);
  if (rc)
    {
      errno = rc;
      return -1;
    }
  sd->prev = dir_stack;
  dir_stack = sd;
  return 0;
}

int
pop_dir ()
{
  struct saved_dir *sd = dir_stack;
  int rc;
  
  if (!sd)
    {
      errno = ENOENT;
      return -1;
    }
  dir_stack = sd->prev;
  if (sd->fd != -1)
    rc = fchdir (sd->fd);
  else
    rc = chdir (sd->name);
  if (rc)
    rc = errno;
  _drop_dir (sd);
  errno = rc;
  return rc;
}