/*
 * Copyright © 2007 Alistair Crooks.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote
 *    products derived from this software without specific prior written
 *    permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
#include <sys/types.h>

#include <db.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <fuse.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

enum {
        BigEndian = 4321,
        LittleEndian = 1234
};

static struct stat      dbst;   /* stat info of database file */
static BTREEINFO        bt;     /* btree information */
static int              verbose; /* how chatty are we? */
static DB               *db;    /* data base operations struct */

/* perform the stat operation */
/* if this is the root, then just synthesise the data */
/* otherwise, retrieve the data, and be sure to fill in the size */
/* we use the mtime of the database file for each of the records */
static int 
dbfs_getattr(const char *path, struct stat *st)
{
        int     res = 0;
        DBT     k;
        DBT     v;

        (void) memset(st, 0x0, sizeof(*st));
        if (strcmp(path, "/") == 0) {
                st->st_mode = S_IFDIR | 0755;
                st->st_nlink = 2;
        } else {
                k.size = strlen(k.data = __UNCONST(path + 1));
                if ((*db->seq)(db, &k, &v, R_CURSOR) != 0) {
                        return -ENOENT;
                }
                st->st_mode = S_IFREG | 0444;
                st->st_nlink = 1;
                st->st_size = v.size;
                st->st_mtime = dbst.st_mtime;
                st->st_atime = dbst.st_atime;
                st->st_ctime = dbst.st_ctime;
                st->st_uid = dbst.st_uid;
                st->st_gid = dbst.st_gid;
        }
        return res;
}

/* readdir operation */
/* run through the database file, returning records by key */
static int 
dbfs_readdir(const char *path, void *buf, fuse_fill_dir_t filler,
              off_t offset, struct fuse_file_info * fi)
{
        static int      ret;
        static DBT      k;
        int     flag;
        DBT     v;
        (void) fi;

        if (offset == 0) {
                (void) memset(&k, 0x0, sizeof(k));
                (void) filler(buf, ".", NULL, 0);
                (void) filler(buf, "..", NULL, 0);
                flag = R_FIRST;
                ret = 0;
        } else {
                flag = R_CURSOR;
        }
        if (ret != 0) {
                return 0;
        }
        for ( ; (ret = (*db->seq)(db, &k, &v, flag)) == 0 ; flag = R_NEXT) {
                if (filler(buf, k.data, NULL, 0) != 0) {
                        return 0;
                }
        }
        return 0;
}

/* open the file in the file system */
/* use seq method to get the record - get doesn't seem to work */
static int 
dbfs_open(const char *path, struct fuse_file_info * fi)
{
        DBT     k;
        DBT     v;

        k.size = strlen(k.data = __UNCONST(path));
        if ((*db->get)(db, &k, &v, 0) != 0) {
                return -ENOENT;
        }

        if ((fi->flags & 3) != O_RDONLY) {
                return -EACCES;
        }
        return 0;
}

/* read the file's contents in the file system */
/* use seq method to get the record - get doesn't seem to work */
static int 
dbfs_read(const char *path, char *buf, size_t size, off_t offset,
           struct fuse_file_info * fi)
{
        size_t  len;
        DBT     k;
        DBT     v;
        (void) fi;

        k.size = strlen(k.data = __UNCONST(path + 1));
        if ((*db->seq)(db, &k, &v, R_CURSOR) != 0) {
                return -ENOENT;
        }
        len = v.size;
        if (offset < len) {
                if (offset + size > len) {
                        size = len - offset;
                }
                (void) memcpy(buf, (char *) v.data + offset, size);
                buf[size - 1] = '\n';
        } else {
                size = 0;
        }
        return size;
}

/* fill in the statvfs struct */
static int
dbfs_statfs(const char *path, struct statvfs *st)
{
        (void) memset(st, 0x0, sizeof(*st));
        st->f_blocks = dbst.st_size / dbst.st_blksize;
        st->f_bsize = st->f_frsize = st->f_iosize = dbst.st_blksize;
        st->f_owner = dbst.st_uid;
        st->f_files = 1;
        return 0;
}

/* operations struct */
static struct fuse_operations dbfs_oper = {
        .getattr = dbfs_getattr,
        .readdir = dbfs_readdir,
        .open = dbfs_open,
        .read = dbfs_read,
        .statfs = dbfs_statfs
};

int 
main(int argc, char **argv)
{
        int     i;

        while ((i = getopt(argc, argv, "v")) != -1) {
                switch(i) {
                case 'v':
                        verbose = 1;
                        break;
                }
        }
        if (stat(argv[optind], &dbst) != 0) {
                err(EXIT_FAILURE, "can't stat `%s'", argv[optind]);
        }
        bt.lorder = LittleEndian;
        if ((db = dbopen(argv[optind], O_RDONLY, 0666, DB_BTREE, &bt)) == NULL) {
                bt.lorder = BigEndian;
                db = dbopen(argv[optind], O_RDONLY, 0666, DB_BTREE, &bt);
                if (verbose) {
                        printf("Database not little endian - trying big endian now\n");
                }
        }
        if (db == NULL) {
                err(EXIT_FAILURE, "can't open db `%s'", argv[optind]);
        }
        return fuse_main(argc, argv, &dbfs_oper);
}