/*-
 * Copyright (c) 2022 Netflix, Inc
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <sys/types.h>
#include "stand.h"
#include "host_syscall.h"
#include "kboot.h"

#define HOST_PATH_MAX   1025

extern struct devsw host_dev;

const char *hostfs_root = "/";

enum FTYPE {
        regular,
        dir,
};

typedef struct _hostfs_file {
        enum FTYPE      hf_type;
        int             hf_fd;
        /* The following are only used for FTYPE == dir */
        char            hf_dents[2048];
        char            *hf_curdent;
        int             hf_dentlen;     /* Valid part of hf_dents */
} hostfs_file;

static hostfs_file *
hostfs_alloc(void)
{
        hostfs_file *hf;

        hf = malloc(sizeof(*hf));
        if (hf != NULL)
                memset(hf, 0, sizeof(*hf));
        return (hf);
}

static void
hostfs_free(hostfs_file *hf)
{
        free(hf);
}

static int
hostfs_open(const char *fn, struct open_file *f)
{
        hostfs_file *hf;
        struct host_kstat ksb;
        char path[HOST_PATH_MAX];

        if (f->f_dev != &host_dev) {
                return (EINVAL);
        }

        /*
         * Normally, we root everything at hostfs_root. However, there are two
         * exceptions that make it easier to write code. First is /sys and /proc
         * are special Linux filesystems, so we pass those paths
         * through. Second, if the path starts with //, then we strip off the
         * first / and pass it through (in a weird way, this is actually in
         * POSIX: hosts are allowed to do specail things with paths that start
         * with two //, but one or three or more are required to be treated as
         * one).
         */
        if (strncmp("/sys/", fn, 5) == 0 || strncmp("/proc/", fn, 6) == 0)
                strlcpy(path, fn, sizeof(path));
        else if (fn[0] == '/' && fn[1] == '/' && fn[2] != '/')
                strlcpy(path, fn + 1, sizeof(path));
        else
                snprintf(path, sizeof(path), "%s/%s", hostfs_root, fn);
        hf = hostfs_alloc();
        hf->hf_fd = host_open(path, HOST_O_RDONLY, 0);
        if (hf->hf_fd < 0) {
                hostfs_free(hf);
                return (EINVAL);
        }

        if (host_fstat(hf->hf_fd, &ksb) < 0) {
                hostfs_free(hf);
                return (EINVAL);
        }
        if (S_ISDIR(hf->hf_fd)) {
                hf->hf_type = dir;
        } else {
                hf->hf_type = regular;
        }
        f->f_fsdata = hf;
        return (0);
}

static int
hostfs_close(struct open_file *f)
{
        hostfs_file *hf = f->f_fsdata;

        host_close(hf->hf_fd);
        hostfs_free(hf);
        f->f_fsdata = NULL;

        return (0);
}

static int
hostfs_read(struct open_file *f, void *start, size_t size, size_t *resid)
{
        hostfs_file *hf = f->f_fsdata;
        ssize_t sz;

        sz = host_read(hf->hf_fd, start, size);
        if (sz < 0)
                return (host_to_stand_errno(sz));
        *resid = size - sz;

        return (0);
}

static off_t
hostfs_seek(struct open_file *f, off_t offset, int whence)
{
        hostfs_file *hf = f->f_fsdata;
        uint32_t offl, offh;
        long err;
        uint64_t res;

        /*
         * Assumes Linux host with 'reduced' system call wrappers. Also assume
         * host and libstand have same whence encoding (safe since it all comes
         * from V7 later ISO-C). Also assumes we have to support powerpc still,
         * it's interface is weird for legacy reasons....
         */
        res = (uint64_t)offset;
        offl = res & 0xfffffffful;
        offh = (res >> 32) & 0xfffffffful;
        err = host_llseek(hf->hf_fd, offh, offl, &res, whence);
        /*
         * Since we're interfacing to the raw linux system call, we have to
         * carefully check. We have to translate the errno value from the host
         * to libsa's conventions.
         */
        if (is_linux_error(err)) {
                errno = host_to_stand_errno(err);
                return (-1);
        }
        return (res);
}

static int
hostfs_stat(struct open_file *f, struct stat *sb)
{
        struct host_kstat ksb;
        hostfs_file *hf = f->f_fsdata;

        if (host_fstat(hf->hf_fd, &ksb) < 0)
                return (EINVAL);
        /*
         * Translate Linux stat info to lib stand's notion (which uses FreeBSD's
         * stat structure, missing fields are zero and commented below).
         */
        memset(sb, 0, sizeof(*sb));
        sb->st_dev              = ksb.st_dev;
        sb->st_ino              = ksb.st_ino;
        sb->st_nlink            = ksb.st_nlink;
        sb->st_mode             = ksb.st_mode;
        sb->st_uid              = ksb.st_uid;
        sb->st_gid              = ksb.st_gid;
        sb->st_rdev             = ksb.st_rdev;
        /* No st_?time_ext on i386 */
        sb->st_atim.tv_sec      = ksb.st_atime_sec;
        sb->st_atim.tv_nsec     = ksb.st_atime_nsec;
        sb->st_mtim.tv_sec      = ksb.st_mtime_sec;
        sb->st_mtim.tv_nsec     = ksb.st_mtime_nsec;
        sb->st_ctim.tv_sec      = ksb.st_ctime_sec;
        sb->st_ctim.tv_nsec     = ksb.st_ctime_nsec;
        /* No st_birthtim */
        sb->st_size             = ksb.st_size;
        sb->st_blocks           = ksb.st_blocks;
        sb->st_blksize          = ksb.st_blksize;
        /* no st_flags */
        /* no st_get */

        return (0);
}

static int
hostfs_readdir(struct open_file *f, struct dirent *d)
{
        hostfs_file *hf = f->f_fsdata;
        int dentlen;
        struct host_dirent64 *dent;

        if (hf->hf_curdent == NULL) {
                dentlen = host_getdents64(hf->hf_fd, hf->hf_dents, sizeof(hf->hf_dents));
                if (dentlen <= 0)
                        return (EINVAL);
                hf->hf_dentlen = dentlen;
                hf->hf_curdent = hf->hf_dents;
        }
        dent = (struct host_dirent64 *)hf->hf_curdent;
        d->d_fileno = dent->d_ino;
        d->d_type = dent->d_type;       /* HOST_DT_XXXX == DX_XXXX for all values */
        strlcpy(d->d_name, dent->d_name, sizeof(d->d_name)); /* d_name is NUL terminated */
        d->d_namlen = strlen(d->d_name);
        hf->hf_curdent += dent->d_reclen;
        if (hf->hf_curdent >= hf->hf_dents + hf->hf_dentlen) {
                hf->hf_curdent = NULL;
                hf->hf_dentlen = 0;
        }

        return (0);
}

struct fs_ops hostfs_fsops = {
        .fs_name = "host",
        .fo_open = hostfs_open,
        .fo_close = hostfs_close,
        .fo_read = hostfs_read,
        .fo_write = null_write,
        .fo_seek = hostfs_seek,
        .fo_stat = hostfs_stat,
        .fo_readdir = hostfs_readdir
};

/*
 * Generic "null" host device. This goes hand and hand with the host fs object
 *
 * XXXX This and userboot for bhyve both use exactly the same code, modulo some
 * formatting nits. Make them common. We mostly use it to 'gate' the open of the
 * filesystem to only this device.
 */

static int
host_dev_init(void)
{
        return (0);
}

static int
host_dev_print(int verbose)
{
        char line[80];

        printf("%s devices:", host_dev.dv_name);
        if (pager_output("\n") != 0)
                return (1);

        snprintf(line, sizeof(line), "    host%d:   Host filesystem\n", 0);
        return (pager_output(line));
}

/*
 * 'Open' the host device.
 */
static int
host_dev_open(struct open_file *f, ...)
{
        return (0);
}

static int
host_dev_close(struct open_file *f)
{
        return (0);
}

static int
host_dev_strategy(void *devdata, int rw, daddr_t dblk, size_t size,
    char *buf, size_t *rsize)
{
        return (ENOSYS);
}

struct devsw host_dev = {
        .dv_name = "host",
        .dv_type = DEVT_NET,
        .dv_init = host_dev_init,
        .dv_strategy = host_dev_strategy,
        .dv_open = host_dev_open,
        .dv_close = host_dev_close,
        .dv_ioctl = noioctl,
        .dv_print = host_dev_print,
        .dv_cleanup = NULL
};