/*
 * 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 <err.h>
#include <errno.h>
#include <fcntl.h>
#include <fuse.h>
#include <regex.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "virtdir.h"
#include "defs.h"

static int               verbose; /* how chatty are we? */

static virtdir_t         pci;

/* a device node describes the device that is printed in the dmesg */
typedef struct devicenode_t {
        char    *dev;           /* device name */
        int      devlen;        /* length of name */
        char    *parent;        /* its parent device name */
        int      parentlen;     /* length of parent name */
        char    *descr;         /* description of the device itself */
        int      descrlen;      /* length of description */
        int      p;             /* device node subscript of parent */
        int      dir;           /* nonzero if this is a directory */
} devicenode_t;

DEFINE_ARRAY(devices_t, devicenode_t);

static devices_t        devices;


/* perform the stat operation */
/* if this is the root, then just synthesise the data */
static int 
dmesgfs_getattr(const char *path, struct stat *st)
{
        virt_dirent_t   *ep;

        if (strcmp(path, "/") == 0) {
                (void) memset(st, 0x0, sizeof(*st));
                st->st_mode = (S_IFDIR | 0755);
                st->st_nlink = 2;
                return 0;
        }
        if ((ep = virtdir_find(&pci, path, strlen(path))) == NULL) {
                return -ENOENT;
        }
        switch(ep->type) {
        case 'f':
                (void) memcpy(st, &pci.file, sizeof(*st));
                st->st_size = ep->tgtlen;
                st->st_mode = S_IFREG | 0644;
                break;
        case 'd':
                (void) memcpy(st, &pci.dir, sizeof(*st));
                break;
        case 'l':
                (void) memcpy(st, &pci.lnk, sizeof(*st));
                st->st_size = ep->tgtlen;
                st->st_mode = S_IFLNK | 0755;
                break;
        }
        st->st_ino = virtdir_offset(&pci, ep) + 10;
        return 0;
}

/* readdir operation */
static int 
dmesgfs_readdir(const char *path, void *buf, fuse_fill_dir_t filler,
              off_t offset, struct fuse_file_info * fi)
{
        static VIRTDIR  *dirp;
        virt_dirent_t   *dp;

        if (offset == 0) {
                if ((dirp = openvirtdir(&pci, path)) == NULL) {
                        return 0;
                }
                filler(buf, ".", NULL, 0);
                filler(buf, "..", NULL, 0);
        }
        while ((dp = readvirtdir(dirp)) != NULL) {
                if (filler(buf, dp->d_name, NULL, 0) != 0) {
                        return 0;
                }
        }
        closevirtdir(dirp);
        dirp = NULL;
        return 0;
}

/* open the file in the file system */
static int 
dmesgfs_open(const char *path, struct fuse_file_info * fi)
{
        return 0;
}

/* read the file's contents in the file system */
static int 
dmesgfs_read(const char *path, char *buf, size_t size, off_t offset,
           struct fuse_file_info * fi)
{
        virt_dirent_t   *ep;

        if ((ep = virtdir_find(&pci, path, strlen(path))) == NULL) {
                return -ENOENT;
        }
        if (ep->tgt == NULL) {
                return -ENOENT;
        }
        (void) memcpy(buf, &ep->tgt[offset], size);
        return ep->tgtlen;
}

/* fill in the statvfs struct */
static int
dmesgfs_statfs(const char *path, struct statvfs *st)
{
        (void) memset(st, 0x0, sizeof(*st));
        return 0;
}

/* read the symbolic link */
static int
dmesgfs_readlink(const char *path, char *buf, size_t size)
{
        virt_dirent_t   *ep;

        if ((ep = virtdir_find(&pci, path, strlen(path))) == NULL) {
                return -ENOENT;
        }
        if (ep->tgt == NULL) {
                return -ENOENT;
        }
        (void) strlcpy(buf, ep->tgt, size);
        return 0;
}

/* operations struct */
static struct fuse_operations dmesgfs_oper = {
        .getattr = dmesgfs_getattr,
        .readlink = dmesgfs_readlink,
        .readdir = dmesgfs_readdir,
        .open = dmesgfs_open,
        .read = dmesgfs_read,
        .statfs = dmesgfs_statfs
};

/* save `n' chars of `s' in malloc'd memory */
static char *
strnsave(const char *s, int n)
{
        char    *cp;

        if (n < 0) {
                n = strlen(s);
        }
        NEWARRAY(char, cp, n + 1, "strnsave", exit(EXIT_FAILURE));
        (void) memcpy(cp, s, n);
        cp[n] = 0x0;
        return cp;
}

/* find a device in the device node tree */
static int
finddev(const char *s, int len, int updir)
{
        int     i;

        for (i = 0 ; i < devices.c ; i++) {
                if (strncmp(devices.v[i].dev, s, len) == 0 &&
                    devices.v[i].devlen == len) {
                        if (updir) {
                                devices.v[i].dir = 1;
                        }
                        return i;
                }
        }
        return -1;
}

/* add a device to the device node tree */
static void
add_dev(const char *dev, int len, const char *parent, int parentlen, const char *descr, int descrlen)
{
        int     d;

        if ((d = finddev(dev, len, 0)) < 0) {
                ALLOC(devicenode_t, devices.v, devices.size, devices.c, 10, 10, "add_dev", exit(EXIT_FAILURE));
                devices.v[devices.c].dev = strnsave(dev, len);
                devices.v[devices.c].devlen = len;
                devices.v[devices.c].parent = strnsave(parent, parentlen);
                devices.v[devices.c].parentlen = parentlen;
                devices.v[devices.c].descr = strnsave(descr, descrlen);
                devices.v[devices.c].descrlen = descrlen;
                devices.c += 1;
        }
}

/* print the parent device pathname */
static int
pparent(int d, char *buf, size_t size)
{
        int     cc;

        if (d != 0) {
                cc = pparent(devices.v[d].p, buf, size);
                size -= cc;
        }
        (void) strlcat(buf, "/", size);
        (void) strlcat(buf, devices.v[d].dev, size - 1);
        return devices.v[d].devlen + 1;
}

#define NEXUS_DESCRIPTION       "Nexus - the root of everything"

/* build up a fuse_tree from the information in the database */
static int
build_tree(virtdir_t *tp, const char *nexus, char type)
{
        struct stat      dir;
        struct stat      f;
        regmatch_t       matchv[10];
        regex_t          r;
        FILE            *pp;
        char             buf[BUFSIZ];
        int              i;
        int              p;

        (void) stat(".", &dir);
        (void) memcpy(&f, &dir, sizeof(f));
        f.st_mode = S_IFREG | 0644;
        if (regcomp(&r, "^([a-z0-9]+) at ([a-z0-9]+)(.*)", REG_EXTENDED) != 0) {
                warn("can't compile regular expression\n");
                return 0;
        }
        if ((pp = popen("dmesg", "r")) == NULL) {
                return 0;
        }
        add_dev(nexus, strlen(nexus), nexus, strlen(nexus), NEXUS_DESCRIPTION,
                strlen(NEXUS_DESCRIPTION));
        while (fgets(buf, sizeof(buf), pp) != NULL) {
                if (type == 'l') {
                        buf[strlen(buf) - 1] = 0x0;
                }
                if (regexec(&r, buf, 10, matchv, 0) == 0) {
                        add_dev(&buf[matchv[1].rm_so],
                                matchv[1].rm_eo - matchv[1].rm_so,
                                &buf[matchv[2].rm_so],
                                matchv[2].rm_eo - matchv[2].rm_so,
                                buf,
                                matchv[0].rm_eo - matchv[0].rm_so);
                }
        }
        printf("%d devices\n", devices.c);
        (void) pclose(pp);
        for (i = 0 ; i < devices.c ; i++) {
                if ((p = finddev(devices.v[i].parent, devices.v[i].parentlen, 1)) < 0) {
                        warn("No parent device for %s\n", devices.v[i].dev);
                }
                devices.v[i].p = p;
        }
        for (i = 0 ; i < devices.c ; i++) {
                pparent(i, buf, sizeof(buf));
                virtdir_add(tp, buf, strlen(buf),
                        (devices.v[i].dir) ? 'd' : type,
                        devices.v[i].descr, devices.v[i].descrlen);
                if (devices.v[i].dir) {
                        (void) strlcat(buf, "/", sizeof(buf));
                        (void) strlcat(buf, "Description", sizeof(buf));
                        virtdir_add(tp, buf, strlen(buf), type,
                                devices.v[i].descr, devices.v[i].descrlen);
                }
                if (verbose) {
                        printf("dmesgfs: adding %s `%s' -> `%s'\n",
                                (type == 'l') ? "symbolic link" : "file",
                                buf, devices.v[i].descr);
                }
                buf[0] = 0x0;
        }
        return 1;
}

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

        nexus = NULL;
        type = 'l';
        while ((i = getopt(argc, argv, "fln:v")) != -1) {
                switch(i) {
                case 'f':
                        type = 'f';
                        break;
                case 'l':
                        type = 'l';
                        break;
                case 'n':
                        nexus = optarg;
                        break;
                case 'v':
                        verbose += 1;
                        break;
                }
        }
        if (!build_tree(&pci, (nexus) ? nexus : "mainbus0", type)) {
                exit(EXIT_FAILURE);
        }
        return fuse_main(argc, argv, &dmesgfs_oper, NULL);
}