#define _GNU_SOURCE
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

int main(int argc, char **argv)
{
    const char *path = "/zvfs/func_test.dat";
    if (argc > 2 && strcmp(argv[1], "-f") == 0) path = argv[2];
    setenv("ZVFS_ROOT", "/zvfs", 0);

    printf("open: %s\n", path);
    int fd = open(path, O_CREAT|O_RDWR, 0644);
    if (fd < 0) { perror("open"); return 1; }

    const char *msg = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    ssize_t w = write(fd, msg, strlen(msg));
    if (w < 0) { perror("write"); return 2; }
    printf("write: %zd\n", w);

    /* Rewind by closing and reopening for read */
    close(fd);
    fd = open(path, O_RDONLY);
    if (fd < 0) { perror("open R"); return 3; }

    char buf[256]; memset(buf, 0, sizeof(buf));
    ssize_t r = read(fd, buf, sizeof(buf));
    if (r < 0) { perror("read"); return 4; }
    printf("read: %zd bytes: %.*s\n", r, (int)r, buf);
    close(fd);

    if (unlink(path) != 0) { perror("unlink"); return 5; }
    printf("unlink: ok\n");
    return 0;
}