/*
 *
 * dirmod.c
 *	  directory handling functions
 *
 * Copyright (C) 2ndQuadrant, 2010-2016
 *
 * Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * 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/>.
 *
 */

#include "postgres_fe.h"

/* Don't modify declarations in system headers */

#include <unistd.h>
#include <dirent.h>
#include <sys/stat.h>

/*
 * pgfnames
 *
 * return a list of the names of objects in the argument directory.  Caller
 * must call pgfnames_cleanup later to free the memory allocated by this
 * function.
 */
char	  **
pgfnames(const char *path)
{
	DIR		   *dir;
	struct dirent *file;
	char	  **filenames;
	int			numnames = 0;
	int			fnsize = 200;	/* enough for many small dbs */

	dir = opendir(path);
	if (dir == NULL)
	{
		return NULL;
	}

	filenames = (char **) palloc(fnsize * sizeof(char *));

	while (errno = 0, (file = readdir(dir)) != NULL)
	{
		if (strcmp(file->d_name, ".") != 0 && strcmp(file->d_name, "..") != 0)
		{
			if (numnames + 1 >= fnsize)
			{
				fnsize *= 2;
				filenames = (char **) repalloc(filenames,
											   fnsize * sizeof(char *));
			}
			filenames[numnames++] = pstrdup(file->d_name);
		}
	}

	if (errno)
	{
		fprintf(stderr, _("could not read directory \"%s\": %s\n"),
				path, strerror(errno));
	}

	filenames[numnames] = NULL;

	if (closedir(dir))
	{
		fprintf(stderr, _("could not close directory \"%s\": %s\n"),
				path, strerror(errno));
	}

	return filenames;
}


/*
 *	pgfnames_cleanup
 *
 *	deallocate memory used for filenames
 */
void
pgfnames_cleanup(char **filenames)
{
	char	  **fn;

	for (fn = filenames; *fn; fn++)
		pfree(*fn);

	pfree(filenames);
}


/*
 *	rmtree
 *
 *	Delete a directory tree recursively.
 *	Assumes path points to a valid directory.
 *	Deletes everything under path.
 *	If rmtopdir is true deletes the directory too.
 *	Returns true if successful, false if there was any problem.
 *	(The details of the problem are reported already, so caller
 *	doesn't really have to say anything more, but most do.)
 */
bool
rmtree(const char *path, bool rmtopdir)
{
	bool		result = true;
	char		pathbuf[MAXPGPATH];
	char	  **filenames;
	char	  **filename;
	struct stat statbuf;

	/*
	 * we copy all the names out of the directory before we start modifying
	 * it.
	 */
	filenames = pgfnames(path);

	if (filenames == NULL)
		return false;

	/* now we have the names we can start removing things */
	for (filename = filenames; *filename; filename++)
	{
		snprintf(pathbuf, MAXPGPATH, "%s/%s", path, *filename);

		/*
		 * It's ok if the file is not there anymore; we were just about to
		 * delete it anyway.
		 *
		 * This is not an academic possibility. One scenario where this
		 * happens is when bgwriter has a pending unlink request for a file in
		 * a database that's being dropped. In dropdb(), we call
		 * ForgetDatabaseFsyncRequests() to flush out any such pending unlink
		 * requests, but because that's asynchronous, it's not guaranteed that
		 * the bgwriter receives the message in time.
		 */
		if (lstat(pathbuf, &statbuf) != 0)
		{
			if (errno != ENOENT)
			{
				result = false;
			}
			continue;
		}

		if (S_ISDIR(statbuf.st_mode))
		{
			/* call ourselves recursively for a directory */
			if (!rmtree(pathbuf, true))
			{
				/* we already reported the error */
				result = false;
			}
		}
		else
		{
			if (unlink(pathbuf) != 0)
			{
				if (errno != ENOENT)
				{
					result = false;
				}
			}
		}
	}

	if (rmtopdir)
	{
		if (rmdir(path) != 0)
		{
			result = false;
		}
	}

	pgfnames_cleanup(filenames);

	return result;
}