/*
   UnDel File System: Midnight Commander file system.

   This file system is intended to be used together with the
   ext2fs library to recover files from ext2fs file systems.

   Parts of this program were taken from the lsdel.c and dump.c files
   written by Ted Ts'o (tytso@mit.edu) for the ext2fs package.

   Copyright (C) 1995-2015
   Free Software Foundation, Inc.

   Written by:
   Miguel de Icaza, 1995
   Norbert Warmuth, 1997
   Pavel Machek, 2000

   This file is part of the Midnight Commander.

   The Midnight Commander 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.

   The Midnight Commander 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/>.
 */

/**
 * \file
 * \brief Source: UnDel File System
 *
 * Assumptions:
 *
 * 1. We don't handle directories (thus undelfs_get_path is easy to write).
 * 2. Files are on the local file system (we do not support vfs files
 *    because we would have to provide an io_manager for the ext2fs tools,
 *    and I don't think it would be too useful to undelete files
 */

#include <config.h>

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>

#ifdef HAVE_EXT2FS_EXT2_FS_H
#include <ext2fs/ext2_fs.h>
#else
/* asm/types.h defines its own umode_t */
#undef umode_t
#include <linux/ext2_fs.h>
#endif

#include <ext2fs/ext2fs.h>
#include <ctype.h>

#include "lib/global.h"

#include "lib/util.h"
#include "lib/widget.h"         /* message() */
#include "lib/vfs/utilvfs.h"
#include "lib/vfs/vfs.h"

#include "undelfs.h"

/*** global variables ****************************************************************************/

/*** file scope macro definitions ****************************************************************/

/* To generate the . and .. entries use -2 */
#define READDIR_PTR_INIT 0

#define undelfs_stat undelfs_lstat

/*** file scope type declarations ****************************************************************/

struct deleted_info
{
    ext2_ino_t ino;
    unsigned short mode;
    unsigned short uid;
    unsigned short gid;
    unsigned long size;
    time_t dtime;
    int num_blocks;
    int free_blocks;
};

struct lsdel_struct
{
    ext2_ino_t inode;
    int num_blocks;
    int free_blocks;
    int bad_blocks;
};

typedef struct
{
    int f_index;                /* file index into delarray */
    char *buf;
    int error_code;             /*  */
    off_t pos;                  /* file position */
    off_t current;              /* used to determine current position in itereate */
    gboolean finished;
    ext2_ino_t inode;
    int bytes_read;
    off_t size;

    /* Used by undelfs_read: */
    char *dest_buffer;          /* destination buffer */
    size_t count;               /* bytes to read */
} undelfs_file;

/*** file scope variables ************************************************************************/

/* We only allow one opened ext2fs */
static char *ext2_fname;
static ext2_filsys fs = NULL;
static struct lsdel_struct lsd;
static struct deleted_info *delarray;
static int num_delarray, max_delarray;
static char *block_buf;
static const char *undelfserr = N_("undelfs: error");
static int readdir_ptr;
static int undelfs_usage;
static struct vfs_class vfs_undelfs_ops;

/*** file scope functions ************************************************************************/
/* --------------------------------------------------------------------------------------------- */

static void
undelfs_shutdown (void)
{
    if (fs)
        ext2fs_close (fs);
    fs = NULL;
    MC_PTR_FREE (ext2_fname);
    MC_PTR_FREE (delarray);
    MC_PTR_FREE (block_buf);
}

/* --------------------------------------------------------------------------------------------- */

static void
undelfs_get_path (const vfs_path_t * vpath, char **fsname, char **file)
{
    const char *p, *dirname;
    const vfs_path_element_t *path_element;

    path_element = vfs_path_get_by_index (vpath, -1);

    /* To look like filesystem, we have virtual directories
       undel://XXX, which have no subdirectories. XXX is replaced with
       hda5, sdb8 etc, which is assumed to live under /dev. 
       -- pavel@ucw.cz */

    dirname = path_element->path;

    *fsname = NULL;

    if (strncmp (dirname, "undel://", 8) != 0)
        return;

    dirname += 8;

    /* Since we don't allow subdirectories, it's easy to get a filename,
     * just scan backwards for a slash */
    if (*dirname == 0)
        return;

    p = dirname + strlen (dirname);
#if 0
    /* Strip trailing ./
     */
    if (p - dirname > 2 && IS_PATH_SEP (p[-1]) && p[-2] == '.')
        *(p = p - 2) = 0;
#endif

    while (p > dirname)
    {
        if (IS_PATH_SEP (*p))
        {
            char *tmp;

            *file = g_strdup (p + 1);
            tmp = g_strndup (dirname, p - dirname);
            *fsname = g_strconcat ("/dev/", tmp, (char *) NULL);
            g_free (tmp);
            return;
        }
        p--;
    }
    *file = g_strdup ("");
    *fsname = g_strconcat ("/dev/", dirname, (char *) NULL);
}

/* --------------------------------------------------------------------------------------------- */

static int
undelfs_lsdel_proc (ext2_filsys _fs, blk_t * block_nr, int blockcnt, void *private)
{
    struct lsdel_struct *_lsd = (struct lsdel_struct *) private;
    (void) blockcnt;
    _lsd->num_blocks++;

    if (*block_nr < _fs->super->s_first_data_block || *block_nr >= _fs->super->s_blocks_count)
    {
        _lsd->bad_blocks++;
        return BLOCK_ABORT;
    }

    if (!ext2fs_test_block_bitmap (_fs->block_map, *block_nr))
        _lsd->free_blocks++;

    return 0;
}

/* --------------------------------------------------------------------------------------------- */
/**
 * Load information about deleted files.
 * Don't abort if there is not enough memory - load as much as we can.
 */

static int
undelfs_loaddel (void)
{
    int retval, count;
    ext2_ino_t ino;
    struct ext2_inode inode;
    ext2_inode_scan scan;

    max_delarray = 100;
    num_delarray = 0;
    delarray = g_try_malloc (sizeof (struct deleted_info) * max_delarray);
    if (!delarray)
    {
        message (D_ERROR, undelfserr, _("not enough memory"));
        return 0;
    }
    block_buf = g_try_malloc (fs->blocksize * 3);
    if (!block_buf)
    {
        message (D_ERROR, undelfserr, _("while allocating block buffer"));
        goto free_delarray;
    }
    retval = ext2fs_open_inode_scan (fs, 0, &scan);
    if (retval != 0)
    {
        message (D_ERROR, undelfserr, _("open_inode_scan: %d"), retval);
        goto free_block_buf;
    }
    retval = ext2fs_get_next_inode (scan, &ino, &inode);
    if (retval != 0)
    {
        message (D_ERROR, undelfserr, _("while starting inode scan %d"), retval);
        goto error_out;
    }
    count = 0;
    while (ino)
    {
        if ((count++ % 1024) == 0)
            vfs_print_message (_("undelfs: loading deleted files information %d inodes"), count);
        if (inode.i_dtime == 0)
            goto next;

        if (S_ISDIR (inode.i_mode))
            goto next;

        lsd.inode = ino;
        lsd.num_blocks = 0;
        lsd.free_blocks = 0;
        lsd.bad_blocks = 0;

        retval = ext2fs_block_iterate (fs, ino, 0, block_buf, undelfs_lsdel_proc, &lsd);
        if (retval)
        {
            message (D_ERROR, undelfserr, _("while calling ext2_block_iterate %d"), retval);
            goto next;
        }
        if (lsd.free_blocks && !lsd.bad_blocks)
        {
            if (num_delarray >= max_delarray)
            {
                struct deleted_info *delarray_new = g_try_realloc (delarray,
                                                                   sizeof (struct deleted_info) *
                                                                   (max_delarray + 50));
                if (!delarray_new)
                {
                    message (D_ERROR, undelfserr, _("no more memory while reallocating array"));
                    goto error_out;
                }
                delarray = delarray_new;
                max_delarray += 50;
            }

            delarray[num_delarray].ino = ino;
            delarray[num_delarray].mode = inode.i_mode;
            delarray[num_delarray].uid = inode.i_uid;
            delarray[num_delarray].gid = inode.i_gid;
            delarray[num_delarray].size = inode.i_size;
            delarray[num_delarray].dtime = inode.i_dtime;
            delarray[num_delarray].num_blocks = lsd.num_blocks;
            delarray[num_delarray].free_blocks = lsd.free_blocks;
            num_delarray++;
        }

      next:
        retval = ext2fs_get_next_inode (scan, &ino, &inode);
        if (retval)
        {
            message (D_ERROR, undelfserr, _("while doing inode scan %d"), retval);
            goto error_out;
        }
    }
    readdir_ptr = READDIR_PTR_INIT;
    ext2fs_close_inode_scan (scan);
    return 1;

  error_out:
    ext2fs_close_inode_scan (scan);
  free_block_buf:
    MC_PTR_FREE (block_buf);
  free_delarray:
    MC_PTR_FREE (delarray);
    return 0;
}

/* --------------------------------------------------------------------------------------------- */

static void *
undelfs_opendir (const vfs_path_t * vpath)
{
    char *file, *f = NULL;
    const vfs_path_element_t *path_element;

    path_element = vfs_path_get_by_index (vpath, -1);
    undelfs_get_path (vpath, &file, &f);
    if (file == NULL)
    {
        g_free (f);
        return 0;
    }

    /* We don't use the file name */
    g_free (f);

    if (!ext2_fname || strcmp (ext2_fname, file))
    {
        undelfs_shutdown ();
        ext2_fname = file;
    }
    else
    {
        /* To avoid expensive re-scannings */
        readdir_ptr = READDIR_PTR_INIT;
        g_free (file);
        return fs;
    }

    if (ext2fs_open (ext2_fname, 0, 0, 0, unix_io_manager, &fs))
    {
        message (D_ERROR, undelfserr, _("Cannot open file %s"), ext2_fname);
        return 0;
    }
    vfs_print_message ("%s", _("undelfs: reading inode bitmap..."));
    if (ext2fs_read_inode_bitmap (fs))
    {
        message (D_ERROR, undelfserr, _("Cannot load inode bitmap from:\n%s"), ext2_fname);
        goto quit_opendir;
    }
    vfs_print_message ("%s", _("undelfs: reading block bitmap..."));
    if (ext2fs_read_block_bitmap (fs))
    {
        message (D_ERROR, undelfserr, _("Cannot load block bitmap from:\n%s"), ext2_fname);
        goto quit_opendir;
    }
    /* Now load the deleted information */
    if (!undelfs_loaddel ())
        goto quit_opendir;
    vfs_print_message (_("%s: done."), path_element->class->name);
    return fs;
  quit_opendir:
    vfs_print_message (_("%s: failure"), path_element->class->name);
    ext2fs_close (fs);
    fs = NULL;
    return 0;
}

/* --------------------------------------------------------------------------------------------- */

static void *
undelfs_readdir (void *vfs_info)
{
    static union vfs_dirent undelfs_readdir_data;
    static char *const dirent_dest = undelfs_readdir_data.dent.d_name;

    if (vfs_info != fs)
    {
        message (D_ERROR, undelfserr, _("vfs_info is not fs!"));
        return NULL;
    }
    if (readdir_ptr == num_delarray)
        return NULL;
    if (readdir_ptr < 0)
        strcpy (dirent_dest, readdir_ptr == -2 ? "." : "..");
    else
        g_snprintf (dirent_dest, MC_MAXPATHLEN, "%ld:%d",
                    (long) delarray[readdir_ptr].ino, delarray[readdir_ptr].num_blocks);
    readdir_ptr++;

    return &undelfs_readdir_data;
}

/* --------------------------------------------------------------------------------------------- */

static int
undelfs_closedir (void *vfs_info)
{
    (void) vfs_info;
    return 0;
}

/* --------------------------------------------------------------------------------------------- */
/* We do not support lseek */

static void *
undelfs_open (const vfs_path_t * vpath, int flags, mode_t mode)
{
    char *file, *f = NULL;
    ext2_ino_t inode, i;
    undelfs_file *p = NULL;
    (void) flags;
    (void) mode;

    /* Only allow reads on this file system */
    undelfs_get_path (vpath, &file, &f);
    if (file == NULL)
    {
        g_free (f);
        return 0;
    }

    if (!ext2_fname || strcmp (ext2_fname, file))
    {
        message (D_ERROR, undelfserr, _("You have to chdir to extract files first"));
        g_free (file);
        g_free (f);
        return 0;
    }
    inode = atol (f);

    /* Search the file into delarray */
    for (i = 0; i < (ext2_ino_t) num_delarray; i++)
    {
        if (inode != delarray[i].ino)
            continue;

        /* Found: setup all the structures needed by read */
        p = (undelfs_file *) g_try_malloc (((gsize) sizeof (undelfs_file)));
        if (!p)
        {
            g_free (file);
            g_free (f);
            return 0;
        }
        p->buf = g_try_malloc (fs->blocksize);
        if (!p->buf)
        {
            g_free (p);
            g_free (file);
            g_free (f);
            return 0;
        }
        p->inode = inode;
        p->finished = FALSE;
        p->f_index = i;
        p->error_code = 0;
        p->pos = 0;
        p->size = delarray[i].size;
    }
    g_free (file);
    g_free (f);
    undelfs_usage++;
    return p;
}

/* --------------------------------------------------------------------------------------------- */

static int
undelfs_close (void *vfs_info)
{
    undelfs_file *p = vfs_info;
    g_free (p->buf);
    g_free (p);
    undelfs_usage--;
    return 0;
}

/* --------------------------------------------------------------------------------------------- */

static int
undelfs_dump_read (ext2_filsys param_fs, blk_t * blocknr, int blockcnt, void *private)
{
    int copy_count;
    undelfs_file *p = (undelfs_file *) private;

    if (blockcnt < 0)
        return 0;

    if (*blocknr)
    {
        p->error_code = io_channel_read_blk (param_fs->io, *blocknr, 1, p->buf);
        if (p->error_code)
            return BLOCK_ABORT;
    }
    else
        memset (p->buf, 0, param_fs->blocksize);

    if (p->pos + (off_t) p->count < p->current)
    {
        p->finished = TRUE;
        return BLOCK_ABORT;
    }
    if (p->pos > p->current + param_fs->blocksize)
    {
        p->current += param_fs->blocksize;
        return 0;               /* we have not arrived yet */
    }

    /* Now, we know we have to extract some data */
    if (p->pos >= p->current)
    {

        /* First case: starting pointer inside this block */
        if (p->pos + (off_t) p->count <= p->current + param_fs->blocksize)
        {
            /* Fully contained */
            copy_count = p->count;
            p->finished = (p->count != 0);
        }
        else
        {
            /* Still some more data */
            copy_count = param_fs->blocksize - (p->pos - p->current);
        }
        memcpy (p->dest_buffer, p->buf + (p->pos - p->current), copy_count);
    }
    else
    {
        /* Second case: we already have passed p->pos */
        if (p->pos + (off_t) p->count < p->current + param_fs->blocksize)
        {
            copy_count = (p->pos + p->count) - p->current;
            p->finished = (p->count != 0);
        }
        else
        {
            copy_count = param_fs->blocksize;
        }
        memcpy (p->dest_buffer, p->buf, copy_count);
    }
    p->dest_buffer += copy_count;
    p->current += param_fs->blocksize;
    if (p->finished)
    {
        return BLOCK_ABORT;
    }
    return 0;
}

/* --------------------------------------------------------------------------------------------- */

static ssize_t
undelfs_read (void *vfs_info, char *buffer, size_t count)
{
    undelfs_file *p = vfs_info;
    int retval;

    p->dest_buffer = buffer;
    p->current = 0;
    p->finished = FALSE;
    p->count = count;

    if (p->pos + (off_t) p->count > p->size)
    {
        p->count = p->size - p->pos;
    }
    retval = ext2fs_block_iterate (fs, p->inode, 0, NULL, undelfs_dump_read, p);
    if (retval)
    {
        message (D_ERROR, undelfserr, _("while iterating over blocks"));
        return -1;
    }
    if (p->error_code && !p->finished)
        return 0;
    p->pos = p->pos + (p->dest_buffer - buffer);
    return p->dest_buffer - buffer;
}

/* --------------------------------------------------------------------------------------------- */

static long
undelfs_getindex (char *path)
{
    ext2_ino_t inode = atol (path);
    int i;

    for (i = 0; i < num_delarray; i++)
    {
        if (delarray[i].ino == inode)
            return i;
    }
    return -1;
}

/* --------------------------------------------------------------------------------------------- */

static int
undelfs_stat_int (int inode_index, struct stat *buf)
{
    buf->st_dev = 0;
    buf->st_ino = delarray[inode_index].ino;
    buf->st_mode = delarray[inode_index].mode;
    buf->st_nlink = 1;
    buf->st_uid = delarray[inode_index].uid;
    buf->st_gid = delarray[inode_index].gid;
    buf->st_size = delarray[inode_index].size;
    buf->st_atime = delarray[inode_index].dtime;
    buf->st_ctime = delarray[inode_index].dtime;
    buf->st_mtime = delarray[inode_index].dtime;
    return 0;
}

/* --------------------------------------------------------------------------------------------- */

static int
undelfs_lstat (const vfs_path_t * vpath, struct stat *buf)
{
    int inode_index;
    char *file, *f = NULL;

    undelfs_get_path (vpath, &file, &f);
    if (file == NULL)
    {
        g_free (f);
        return 0;
    }

    /* When called from save_cwd_stats we get an incorrect file and f here:
       e.g. incorrect                         correct
       path = "undel:/dev/sda1"          path="undel:/dev/sda1/401:1"
       file = "/dev"                     file="/dev/sda1"
       f    = "sda1"                     f   ="401:1"
       If the first char in f is no digit -> return error */
    if (!isdigit (*f))
    {
        g_free (file);
        g_free (f);
        return -1;
    }

    if (!ext2_fname || strcmp (ext2_fname, file))
    {
        message (D_ERROR, undelfserr, _("You have to chdir to extract files first"));
        g_free (file);
        g_free (f);
        return 0;
    }
    inode_index = undelfs_getindex (f);
    g_free (file);
    g_free (f);

    if (inode_index == -1)
        return -1;

    return undelfs_stat_int (inode_index, buf);
}

/* --------------------------------------------------------------------------------------------- */

static int
undelfs_fstat (void *vfs_info, struct stat *buf)
{
    undelfs_file *p = vfs_info;

    return undelfs_stat_int (p->f_index, buf);
}

/* --------------------------------------------------------------------------------------------- */

static int
undelfs_chdir (const vfs_path_t * vpath)
{
    char *file, *f = NULL;
    int fd;

    undelfs_get_path (vpath, &file, &f);
    if (file == NULL)
    {
        g_free (f);
        return (-1);
    }

    /* We may use access because ext2 file systems are local */
    /* this could be fixed by making an ext2fs io manager to use */
    /* our vfs, but that is left as an exercise for the reader */
    fd = open (file, O_RDONLY);
    if (fd == -1)
    {
        message (D_ERROR, undelfserr, _("Cannot open file \"%s\""), file);
        g_free (f);
        g_free (file);
        return -1;
    }
    close (fd);
    g_free (f);
    g_free (file);
    return 0;
}

/* --------------------------------------------------------------------------------------------- */

/* this has to stay here for now: vfs layer does not know how to emulate it */
static off_t
undelfs_lseek (void *vfs_info, off_t offset, int whence)
{
    (void) vfs_info;
    (void) offset;
    (void) whence;

    return -1;
}

/* --------------------------------------------------------------------------------------------- */

static vfsid
undelfs_getid (const vfs_path_t * vpath)
{
    char *fname = NULL, *fsname;
    gboolean ok;

    undelfs_get_path (vpath, &fsname, &fname);
    ok = fsname != NULL;

    g_free (fname);
    g_free (fsname);

    return ok ? (vfsid) fs : NULL;
}

/* --------------------------------------------------------------------------------------------- */

static int
undelfs_nothingisopen (vfsid id)
{
    (void) id;

    return !undelfs_usage;
}

/* --------------------------------------------------------------------------------------------- */

static void
undelfs_free (vfsid id)
{
    (void) id;

    undelfs_shutdown ();
}

/* --------------------------------------------------------------------------------------------- */

#ifdef ENABLE_NLS
static int
undelfs_init (struct vfs_class *me)
{
    (void) me;

    undelfserr = _(undelfserr);
    return 1;
}
#else
#define undelfs_init NULL
#endif

/* --------------------------------------------------------------------------------------------- */
/*** public functions ****************************************************************************/
/* --------------------------------------------------------------------------------------------- */
/**
 * This function overrides com_err() from libcom_err library.
 * It is used in libext2fs to report errors.
 */

void
com_err (const char *whoami, long err_code, const char *fmt, ...)
{
    va_list ap;
    char *str;

    va_start (ap, fmt);
    str = g_strdup_vprintf (fmt, ap);
    va_end (ap);

    message (D_ERROR, _("Ext2lib error"), "%s (%s: %ld)", str, whoami, err_code);
    g_free (str);
}

/* --------------------------------------------------------------------------------------------- */

void
init_undelfs (void)
{
    vfs_undelfs_ops.name = "undelfs";
    vfs_undelfs_ops.prefix = "undel";
    vfs_undelfs_ops.init = undelfs_init;
    vfs_undelfs_ops.open = undelfs_open;
    vfs_undelfs_ops.close = undelfs_close;
    vfs_undelfs_ops.read = undelfs_read;
    vfs_undelfs_ops.opendir = undelfs_opendir;
    vfs_undelfs_ops.readdir = undelfs_readdir;
    vfs_undelfs_ops.closedir = undelfs_closedir;
    vfs_undelfs_ops.stat = undelfs_stat;
    vfs_undelfs_ops.lstat = undelfs_lstat;
    vfs_undelfs_ops.fstat = undelfs_fstat;
    vfs_undelfs_ops.chdir = undelfs_chdir;
    vfs_undelfs_ops.lseek = undelfs_lseek;
    vfs_undelfs_ops.getid = undelfs_getid;
    vfs_undelfs_ops.nothingisopen = undelfs_nothingisopen;
    vfs_undelfs_ops.free = undelfs_free;
    vfs_register_class (&vfs_undelfs_ops);
}

/* --------------------------------------------------------------------------------------------- */
