/* $Id$
 * UDP Gateway single-file bundle utility functions
 * Copyright (C) 2004 Jan Kratochvil <project-udpgate@jankratochvil.net>
 * 
 * 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; exactly version 2 of June 1991 is required
 * 
 * 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, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */


#include "config.h"

#include <glib/gmessages.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <glib/gmem.h>
#include <unistd.h>
#include <string.h>
#include <time.h>
#include <stdio.h>

#include "bundle-util.h"	/* self */
#include "bundle.h"
#include "main.h"


static G_CONST_RETURN guint8 *bundle_util_file_retrieve(guint32 *data_length_return,const gchar *basename)
{
const guint8 *data;

	g_return_val_if_fail(data_length_return!=NULL,NULL);
	g_return_val_if_fail(basename!=NULL,NULL);

	if (optarg_verbose)
		g_message(_("Retrieving internally stored: %s"),basename);
	data=g_hash_table_lookup(bundle_hash_new(),basename);
	g_return_val_if_fail(data!=NULL,NULL);
	*data_length_return=GUINT32_FROM_BE(*(guint32 *)data);
	data+=sizeof(*data_length_return);

	return data;
}

/* Returns TRUE if it safe to overwrite/unlink the file.
 */
static gboolean bundle_util_file_backup_conditional(const gchar *pathname,const gchar *basename)
{
const guint8 *data;
guint32 data_length;
int fd;
guint8 *data_found;
int got;
char strftime_buffer[LINE_MAX];
const gchar *destination;
time_t time_current;

	g_return_val_if_fail(pathname!=NULL,FALSE);
	g_return_val_if_fail(basename!=NULL,FALSE);

	if (!(data=bundle_util_file_retrieve(&data_length,basename)))
		return FALSE;

	if (-1==(fd=open(pathname,O_RDONLY))) {
		if (errno==ENOENT)
			return TRUE;
		else {
			g_warning(_("Error checking file modifications of \"%s\": %m"),pathname);
			return FALSE;
			}
		}

	/* WARNING: 'data_found' allocated in this block! */
	data_found=g_malloc(data_length+1);
	if (-1==(got=read(fd,data_found,data_length+1)))
		g_warning(_("Error reading during the check of file modifications of \"%s\": %m"),pathname);
	if (close(fd))
		g_warning(_("Error closing the file \"%s\" during the check of its modifications: %m"),pathname);
	/* memcmp(3) requires 'data_found'! */
	if (got==(int)data_length && !memcmp(data_found,data,data_length)) {
		g_free(data_found);
		return TRUE;
		}
	g_free(data_found);

	time_current=time(NULL);	/* It is segfault to gmtime(NULL). */
	if (!strftime(strftime_buffer,sizeof(strftime_buffer),"GMT%FT%T",gmtime(&time_current))) {
		g_warning("strftime(3): %m");	/* shouldn't happen */
		return FALSE;
		}
	destination=udpgate_printf_alloca("%s-%s-%d",pathname,strftime_buffer,(int)getpid());
	if (rename(pathname,destination)) {
		g_warning(_("Error renaming your modified file \"%s\" to the backup \"%s\", giving up: %m"),
				pathname,destination);
		return FALSE;
		}

	return TRUE;
}

gboolean bundle_util_file_remove(const gchar *pathname,const gchar *basename)
{
	g_return_val_if_fail(pathname!=NULL,FALSE);
	g_return_val_if_fail(basename!=NULL,FALSE);

	if (!bundle_util_file_backup_conditional(pathname,basename))
		return FALSE;

	if (unlink(pathname) && errno!=ENOENT) {
		g_warning(_("Error removing the file \"%s\": %m"),pathname);
		return FALSE;
		}
	
	return TRUE;
}

gboolean bundle_util_file_write(const gchar *pathname,const gchar *basename,mode_t pathname_mode,gboolean pathname_backup)
{
const guint8 *data;
guint32 data_length;
int fd;

	g_return_val_if_fail(pathname!=NULL,FALSE);
	g_return_val_if_fail(basename!=NULL,FALSE);

	if (!(data=bundle_util_file_retrieve(&data_length,basename)))
		return FALSE;

	if (pathname_backup && !bundle_util_file_backup_conditional(pathname,basename))
		return FALSE;

	if (-1==(fd=open(pathname,O_WRONLY|O_CREAT|O_TRUNC,pathname_mode))) {
		g_warning(_("Error opening the file \"%s\" for rewrite: %m"),pathname);
		return FALSE;
		}
	if ((int)data_length!=write(fd,data,data_length)) {
		g_warning(_("Error writing the data of the file \"%s\" being overwritten: %m"),pathname);
		close(fd);	/* errors ignored */
		return FALSE;
		}
	if (close(fd)) {
		g_warning(_("Error closing the file \"%s\" after its rewrite: %m"),pathname);
		return FALSE;
		}
	return TRUE;
}