#include <err.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>

#include <sys/event.h>
#include <sys/time.h>

/*
 * External test set-up code is expected to do the equivalent of
 *      cd $TOPDIR
 *      mkdir realdir
 *      mkdir nulldir
 *      mount -t null $TOPDIR/realdir $TOPDIR/nulldir
 *      rm -f $TOPDIR/realdir/afile
 *      touch $TOPDIR/realdir/afile
 * then execute this test program:
 *      ./h_nullmnt $TOPDIR/realdir/afile $TOPDIR/nulldir/afile
 *
 * The expected result is that the write() to the nullfile will
 * queue up a preexisting kevent which will then be detected by
 * the (second) call to kevent(); the failure mode is that the
 * write()'s extension to the file is not seen, and the kevent
 * call times out after 5 seconds.
 *
 * Clean-up code should undo the null mount and delete everything
 * in the test directory.
 */

int main(int argc, char **argv)
{
        int watch_file, write_file;
        int kq, nev, rsize;
        struct timespec timeout;
        struct kevent eventlist;
        const char outbuf[] = "new\n";
        char inbuf[20];

        if (argc <= 2)
                errx(EXIT_FAILURE, "insufficient args %d", argc);

        watch_file = open(argv[1], O_RDONLY);
        if (watch_file == -1)
                err(EXIT_FAILURE, "failed to open watch_file %s",
                    argv[1]);

        write_file = open(argv[2], O_WRONLY, O_APPEND);
        if (write_file == -1)
                err(EXIT_FAILURE, "failed to open write_file %s",
                    argv[2]);

        if ((kq = kqueue()) == -1)
                err(EXIT_FAILURE, "Cannot create kqueue");

        timeout.tv_sec = 5;
        timeout.tv_nsec = 0;

        EV_SET(&eventlist, watch_file,
            EVFILT_VNODE, EV_ADD | EV_ENABLE | EV_CLEAR,
            NOTE_WRITE | NOTE_EXTEND, 0, 0);
        if (kevent(kq, &eventlist, 1, NULL, 0, NULL) == -1)
                err(EXIT_FAILURE, "Failed to set eventlist for fd %d",
                    watch_file);

        rsize = read(watch_file, &inbuf, sizeof(inbuf));
        if (rsize)
                errx(EXIT_FAILURE, "Ooops we got %d bytes of data!\n", rsize);

        write(write_file, &outbuf, sizeof(outbuf) - 1);

        nev = kevent(kq, NULL, 0, &eventlist, 1, &timeout);
        if (nev == -1)
                err(EXIT_FAILURE, "Failed to retrieve event");

        errx((nev == 0) ? EXIT_FAILURE : EXIT_SUCCESS,
            "Retrieved %d events, first 0x%x", nev, eventlist.flags);
}