#define FUSE_USE_VERSION 30
#include <fuse.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#include <dirent.h>
#include <unistd.h>

#ifndef PATH_MAX
#define PATH_MAX 4096
#endif

static const char *basedir;
static char mountpoint[PATH_MAX];

static int simplefs_getattr(const char *path, struct stat *stbuf)
{
    int res = 0;
    char full_path[PATH_MAX];
    snprintf(full_path, sizeof(full_path), "%s%s", basedir, path);

    res = lstat(full_path, stbuf);
    if (res == -1)
        return -errno;

    return 0;
}

static int simplefs_readdir(const char *path, void *buf, fuse_fill_dir_t filler,
                            off_t offset, struct fuse_file_info *fi)
{
    DIR *dp;
    struct dirent *de;

    (void)offset;
    (void)fi;

    char full_path[PATH_MAX];
    snprintf(full_path, sizeof(full_path), "%s%s", basedir, path);

    dp = opendir(full_path);
    if (dp == NULL)
        return -errno;

    filler(buf, ".", NULL, 0);
    filler(buf, "..", NULL, 0);

    while ((de = readdir(dp)) != NULL) {
        filler(buf, de->d_name, NULL, 0);
    }

    closedir(dp);
    return 0;
}

static int simplefs_read(const char *path, char *buf, size_t size, off_t offset,
                         struct fuse_file_info *fi)
{
    int fd;
    int res;
    char full_path[PATH_MAX];
    snprintf(full_path, sizeof(full_path), "%s%s", basedir, path);

    (void)fi;
    fd = open(full_path, O_RDONLY);
    if (fd == -1)
        return -errno;

    res = pread(fd, buf, size, offset);
    if (res == -1)
        res = -errno;

    close(fd);
    return res;
}

static int simplefs_write(const char *path, const char *buf, size_t size,
                          off_t offset, struct fuse_file_info *fi)
{
    int fd;
    int res;
    char full_path[PATH_MAX];
    snprintf(full_path, sizeof(full_path), "%s%s", basedir, path);

    (void)fi;
    fd = open(full_path, O_WRONLY);
    if (fd == -1)
        return -errno;

    res = pwrite(fd, buf, size, offset);
    if (res == -1)
        res = -errno;

    close(fd);
    return res;
}

static int simplefs_mkdir(const char *path, mode_t mode)
{
    int res;
    char full_path[PATH_MAX];
    snprintf(full_path, sizeof(full_path), "%s%s", basedir, path);

    res = mkdir(full_path, mode);
    if (res == -1)
        return -errno;

    return 0;
}

static int simplefs_rmdir(const char *path)
{
    int res;
    char full_path[PATH_MAX];
    snprintf(full_path, sizeof(full_path), "%s%s", basedir, path);

    res = rmdir(full_path);
    if (res == -1)
        return -errno;

    return 0;
}

static int simplefs_unlink(const char *path)
{
    int res;
    char full_path[PATH_MAX];
    snprintf(full_path, sizeof(full_path), "%s%s", basedir, path);

    res = unlink(full_path);
    if (res == -1)
        return -errno;

    return 0;
}

static struct fuse_operations simplefs_operations = {
    .getattr = simplefs_getattr,
    .readdir = simplefs_readdir,
    .read = simplefs_read,
    .write = simplefs_write,
    .mkdir = simplefs_mkdir,
    .rmdir = simplefs_rmdir,
    .unlink = simplefs_unlink,
};

int main(int argc, char *argv[])
{
    if (argc != 3) {
        fprintf(stderr, "Usage: %s <mountpoint> <basedir>\n", argv[0]);
        return EXIT_FAILURE;
    }

    basedir = realpath(argv[2], NULL);
    if (basedir == NULL) {
        perror("Error getting realpath");
        return EXIT_FAILURE;
    }

    strcpy(mountpoint, argv[1]);
    strcat(mountpoint, "1");

    return fuse_main(argc - 1, argv + 1, &simplefs_operations, NULL);
}