// SPDX-License-Identifier: GPL-2.0

#include <errno.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <unistd.h>
#include <linux/limits.h>

#include "kselftest.h"

#define MIN_TTY_PATH_LEN 8

static bool tty_valid(char *tty)
{
        if (strlen(tty) < MIN_TTY_PATH_LEN)
                return false;

        if (strncmp(tty, "/dev/tty", MIN_TTY_PATH_LEN) == 0 ||
            strncmp(tty, "/dev/pts", MIN_TTY_PATH_LEN) == 0)
                return true;

        return false;
}

static int write_dev_tty(void)
{
        FILE *f;
        int r = 0;

        f = fopen("/dev/tty", "r+");
        if (!f)
                return -errno;

        r = fprintf(f, "hello, world!\n");
        if (r != strlen("hello, world!\n"))
                r = -EIO;

        fclose(f);
        return r;
}

int main(int argc, char **argv)
{
        int r;
        char tty[PATH_MAX] = {};
        struct stat st1, st2;
        int result = KSFT_FAIL;

        ksft_print_header();
        ksft_set_plan(1);

        r = readlink("/proc/self/fd/0", tty, PATH_MAX);
        if (r < 0) {
                ksft_print_msg("readlink on /proc/self/fd/0 failed: %m\n");
                goto out;
        }

        if (!tty_valid(tty)) {
                ksft_print_msg("invalid tty path '%s'\n", tty);
                result = KSFT_SKIP;
                goto out;

        }

        r = stat(tty, &st1);
        if (r < 0) {
                ksft_print_msg("stat failed on tty path '%s': %m\n", tty);
                goto out;
        }

        /* We need to wait at least 8 seconds in order to observe timestamp change */
        /* https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=fbf47635315ab308c9b58a1ea0906e711a9228de */
        sleep(10);

        r = write_dev_tty();
        if (r < 0) {
                ksft_print_msg("failed to write to /dev/tty: %s\n",
                               strerror(-r));
                goto out;
        }

        r = stat(tty, &st2);
        if (r < 0) {
                ksft_print_msg("stat failed on tty path '%s': %m\n", tty);
                goto out;
        }

        /* We wrote to the terminal so timestamps should have been updated */
        if (st1.st_atim.tv_sec == st2.st_atim.tv_sec &&
            st1.st_mtim.tv_sec == st2.st_mtim.tv_sec) {
                ksft_print_msg("tty timestamps not updated\n");
                goto out;
        }

        ksft_print_msg(
                "timestamps of terminal '%s' updated after write to /dev/tty\n", tty);
        result = KSFT_PASS;

out:
        ksft_test_result_report(result, "tty_tstamp_update\n");

        ksft_finished();
}