/*
   Unix SMB/CIFS implementation.

   Copyright (C) Andrew Tridgell 2004

   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/>.
*/
/*
  directory listing functions for posix backend
*/

#include "includes.h"
#include "vfs_posix.h"
#include "system/dir.h"

#define NAME_CACHE_SIZE 100

struct name_cache_entry {
	char *name;
	off_t offset;
};

struct pvfs_dir {
	struct pvfs_state *pvfs;
	bool no_wildcard;
	char *single_name;
	const char *pattern;
	off_t offset;
	DIR *dir;
	const char *unix_path;
	bool end_of_search;
	struct name_cache_entry *name_cache;
	uint32_t name_cache_index;
};

/* these three numbers are chosen to minimise the chances of a bad
   interaction with the OS value for 'end of directory'. On IRIX
   telldir() returns 0xFFFFFFFF at the end of a directory, and that
   caused an infinite loop with the original values of 0,1,2

   On XFS on linux telldir returns 0x7FFFFFFF at the end of a
   directory. Thus the change from 0x80000002, as otherwise
   0x7FFFFFFF+0x80000002==1==DIR_OFFSET_DOTDOT
*/
#define DIR_OFFSET_DOT    0
#define DIR_OFFSET_DOTDOT 1
#define DIR_OFFSET_BASE   0x80000022

/*
  a special directory listing case where the pattern has no wildcard. We can just do a single stat()
  thus avoiding the more expensive directory scan
*/
static NTSTATUS pvfs_list_no_wildcard(struct pvfs_state *pvfs, struct pvfs_filename *name,
				      const char *pattern, struct pvfs_dir *dir)
{
	if (!name->exists) {
		return NT_STATUS_OBJECT_NAME_NOT_FOUND;
	}

	dir->pvfs = pvfs;
	dir->no_wildcard = true;
	dir->end_of_search = false;
	dir->unix_path = talloc_strdup(dir, name->full_name);
	if (!dir->unix_path) {
		return NT_STATUS_NO_MEMORY;
	}

	dir->single_name = talloc_strdup(dir, pattern);
	if (!dir->single_name) {
		return NT_STATUS_NO_MEMORY;
	}

	dir->dir = NULL;
	dir->offset = 0;
	dir->pattern = NULL;

	return NT_STATUS_OK;
}

/*
  destroy an open search
*/
static int pvfs_dirlist_destructor(struct pvfs_dir *dir)
{
	if (dir->dir) closedir(dir->dir);
	return 0;
}

/*
  start to read a directory

  if the pattern matches no files then we return NT_STATUS_OK, with dir->count = 0
*/
NTSTATUS pvfs_list_start(struct pvfs_state *pvfs, struct pvfs_filename *name,
			 TALLOC_CTX *mem_ctx, struct pvfs_dir **dirp)
{
	char *pattern;
	struct pvfs_dir *dir;

	(*dirp) = talloc_zero(mem_ctx, struct pvfs_dir);
	if (*dirp == NULL) {
		return NT_STATUS_NO_MEMORY;
	}

	dir = *dirp;

	/* split the unix path into a directory + pattern */
	pattern = strrchr(name->full_name, '/');
	if (!pattern) {
		/* this should not happen, as pvfs_unix_path is supposed to
		   return an absolute path */
		return NT_STATUS_UNSUCCESSFUL;
	}

	*pattern++ = 0;

	if (!name->has_wildcard) {
		return pvfs_list_no_wildcard(pvfs, name, pattern, dir);
	}

	dir->unix_path = talloc_strdup(dir, name->full_name);
	if (!dir->unix_path) {
		return NT_STATUS_NO_MEMORY;
	}

	dir->pattern = talloc_strdup(dir, pattern);
	if (dir->pattern == NULL) {
		return NT_STATUS_NO_MEMORY;
	}

	dir->dir = opendir(name->full_name);
	if (!dir->dir) {
		return pvfs_map_errno(pvfs, errno);
	}

	dir->pvfs = pvfs;
	dir->no_wildcard = false;
	dir->end_of_search = false;
	dir->offset = DIR_OFFSET_DOT;
	dir->name_cache = talloc_zero_array(dir,
					    struct name_cache_entry,
					    NAME_CACHE_SIZE);
	if (dir->name_cache == NULL) {
		talloc_free(dir);
		return NT_STATUS_NO_MEMORY;
	}

	talloc_set_destructor(dir, pvfs_dirlist_destructor);

	return NT_STATUS_OK;
}

/*
  add an entry to the local cache
*/
static void dcache_add(struct pvfs_dir *dir, const char *name)
{
	struct name_cache_entry *e;

	dir->name_cache_index = (dir->name_cache_index+1) % NAME_CACHE_SIZE;
	e = &dir->name_cache[dir->name_cache_index];

	if (e->name) talloc_free(e->name);

	e->name = talloc_strdup(dir->name_cache, name);
	e->offset = dir->offset;
}

/*
   return the next entry
*/
const char *pvfs_list_next(struct pvfs_dir *dir, off_t *ofs)
{
	struct dirent *de;
	enum protocol_types protocol = dir->pvfs->ntvfs->ctx->protocol;

	/* non-wildcard searches are easy */
	if (dir->no_wildcard) {
		dir->end_of_search = true;
		if (*ofs != 0) return NULL;
		(*ofs)++;
		return dir->single_name;
	}

	/* . and .. are handled separately as some unix systems will
	   not return them first in a directory, but windows client
	   may assume that these entries always appear first */
	if (*ofs == DIR_OFFSET_DOT) {
		(*ofs) = DIR_OFFSET_DOTDOT;
		dir->offset = *ofs;
		if (ms_fnmatch_protocol(dir->pattern, ".", protocol,
					false) == 0) {
			dcache_add(dir, ".");
			return ".";
		}
	}

	if (*ofs == DIR_OFFSET_DOTDOT) {
		(*ofs) = DIR_OFFSET_BASE;
		dir->offset = *ofs;
		if (ms_fnmatch_protocol(dir->pattern, "..", protocol,
					false) == 0) {
			dcache_add(dir, "..");
			return "..";
		}
	}

	if (*ofs == DIR_OFFSET_BASE) {
		rewinddir(dir->dir);
	} else if (*ofs != dir->offset) {
		seekdir(dir->dir, (*ofs) - DIR_OFFSET_BASE);
	}
	dir->offset = *ofs;

	while ((de = readdir(dir->dir))) {
		const char *dname = de->d_name;

		if (ISDOT(dname) || ISDOTDOT(dname)) {
			continue;
		}

		if (ms_fnmatch_protocol(dir->pattern, dname, protocol,
					false) != 0) {
			char *short_name = pvfs_short_name_component(dir->pvfs, dname);
			if (short_name == NULL ||
			    ms_fnmatch_protocol(dir->pattern, short_name,
						protocol, false) != 0) {
				talloc_free(short_name);
				continue;
			}
			talloc_free(short_name);
		}

		/* Casting is necessary to avoid signed integer overflow. */
		dir->offset = (unsigned long)telldir(dir->dir) + (unsigned long)DIR_OFFSET_BASE;
		(*ofs) = dir->offset;

		dcache_add(dir, dname);

		return dname;
	}

	dir->end_of_search = true;
	return NULL;
}

/*
  return unix directory of an open search
*/
const char *pvfs_list_unix_path(struct pvfs_dir *dir)
{
	return dir->unix_path;
}

/*
  return true if end of search has been reached
*/
bool pvfs_list_eos(struct pvfs_dir *dir, off_t ofs)
{
	return dir->end_of_search;
}

/*
  seek to the given name
*/
NTSTATUS pvfs_list_seek(struct pvfs_dir *dir, const char *name, off_t *ofs)
{
	struct dirent *de;
	int i;

	dir->end_of_search = false;

	if (ISDOT(name)) {
		dir->offset = DIR_OFFSET_DOTDOT;
		*ofs = dir->offset;
		return NT_STATUS_OK;
	}

	if (ISDOTDOT(name)) {
		dir->offset = DIR_OFFSET_BASE;
		*ofs = dir->offset;
		return NT_STATUS_OK;
	}

	for (i=dir->name_cache_index;i>=0;i--) {
		struct name_cache_entry *e = &dir->name_cache[i];
		if (e->name && strcasecmp_m(name, e->name) == 0) {
			*ofs = e->offset;
			return NT_STATUS_OK;
		}
	}
	for (i=NAME_CACHE_SIZE-1;i>dir->name_cache_index;i--) {
		struct name_cache_entry *e = &dir->name_cache[i];
		if (e->name && strcasecmp_m(name, e->name) == 0) {
			*ofs = e->offset;
			return NT_STATUS_OK;
		}
	}

	rewinddir(dir->dir);

	while ((de = readdir(dir->dir))) {
		if (strcasecmp_m(name, de->d_name) == 0) {
			/* Casting is necessary to avoid signed integer overflow. */
			dir->offset = (unsigned long)telldir(dir->dir) + (unsigned long)DIR_OFFSET_BASE;
			*ofs = dir->offset;
			return NT_STATUS_OK;
		}
	}

	dir->end_of_search = true;

	return NT_STATUS_OBJECT_NAME_NOT_FOUND;
}

/*
  seek to the given offset
*/
NTSTATUS pvfs_list_seek_ofs(struct pvfs_dir *dir, uint32_t resume_key, off_t *ofs)
{
	struct dirent *de;
	int i;

	dir->end_of_search = false;

	if (resume_key == DIR_OFFSET_DOT) {
		*ofs = DIR_OFFSET_DOTDOT;
		return NT_STATUS_OK;
	}

	if (resume_key == DIR_OFFSET_DOTDOT) {
		*ofs = DIR_OFFSET_BASE;
		return NT_STATUS_OK;
	}

	if (resume_key == DIR_OFFSET_BASE) {
		rewinddir(dir->dir);
		if ((de=readdir(dir->dir)) == NULL) {
			dir->end_of_search = true;
			return NT_STATUS_OBJECT_NAME_NOT_FOUND;
		}
		/* Casting is necessary to avoid signed integer overflow. */
		*ofs = (unsigned long)telldir(dir->dir) + (unsigned long)DIR_OFFSET_BASE;
		dir->offset = *ofs;
		return NT_STATUS_OK;
	}

	for (i=dir->name_cache_index;i>=0;i--) {
		struct name_cache_entry *e = &dir->name_cache[i];
		if (resume_key == (uint32_t)e->offset) {
			*ofs = e->offset;
			return NT_STATUS_OK;
		}
	}
	for (i=NAME_CACHE_SIZE-1;i>dir->name_cache_index;i--) {
		struct name_cache_entry *e = &dir->name_cache[i];
		if (resume_key == (uint32_t)e->offset) {
			*ofs = e->offset;
			return NT_STATUS_OK;
		}
	}

	rewinddir(dir->dir);

	while ((de = readdir(dir->dir))) {
		/* Casting is necessary to avoid signed integer overflow. */
		dir->offset = (unsigned long)telldir(dir->dir) + (unsigned long)DIR_OFFSET_BASE;
		if (resume_key == (uint32_t)dir->offset) {
			*ofs = dir->offset;
			return NT_STATUS_OK;
		}
	}

	dir->end_of_search = true;

	return NT_STATUS_OBJECT_NAME_NOT_FOUND;
}


/*
  see if a directory is empty
*/
bool pvfs_directory_empty(struct pvfs_state *pvfs, struct pvfs_filename *name)
{
	struct dirent *de;
	DIR *dir = opendir(name->full_name);
	if (dir == NULL) {
		return true;
	}

	while ((de = readdir(dir))) {
		if (!ISDOT(de->d_name) && !ISDOTDOT(de->d_name)) {
			closedir(dir);
			return false;
		}
	}

	closedir(dir);
	return true;
}
