/* wydawca - automatic release submission daemon
   Copyright (C) 2011,2013 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;
}