/*****************************************************************************
 *
 * Monitoring check_users plugin
 *
 * License: GPL
 * Copyright (c) 2000-2024 Monitoring Plugins Development Team
 *
 * Description:
 *
 * This file contains the check_users plugin
 *
 * This plugin checks the number of users currently logged in on the local
 * system and generates an error if the number exceeds the thresholds
 * specified.
 *
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *
 *****************************************************************************/

const char *progname = "check_users";
const char *copyright = "2000-2024";
const char *email = "devel@monitoring-plugins.org";

#include "common.h"
#include "utils.h"

#if HAVE_WTSAPI32_H
#	include <windows.h>
#	include <wtsapi32.h>
#	undef ERROR
#	define ERROR -1
#elif HAVE_UTMPX_H
#	include <utmpx.h>
#else
#	include "popen.h"
#endif

#ifdef HAVE_LIBSYSTEMD
#	include <systemd/sd-daemon.h>
#	include <systemd/sd-login.h>
#endif

#define possibly_set(a, b) ((a) == 0 ? (b) : 0)

static int process_arguments(int, char **);
static void print_help(void);
void print_usage(void);

static char *warning_range = NULL;
static char *critical_range = NULL;
static thresholds *thlds = NULL;

int main(int argc, char **argv) {
	int users = -1;
	int result = STATE_UNKNOWN;
#if HAVE_WTSAPI32_H
	WTS_SESSION_INFO *wtsinfo;
	DWORD wtscount;
	DWORD index;
#elif HAVE_UTMPX_H
	struct utmpx *putmpx;
#else
	char input_buffer[MAX_INPUT_BUFFER];
#endif

	setlocale(LC_ALL, "");
	bindtextdomain(PACKAGE, LOCALEDIR);
	textdomain(PACKAGE);

	/* Parse extra opts if any */
	argv = np_extra_opts(&argc, argv, progname);

	if (process_arguments(argc, argv) == ERROR)
		usage4(_("Could not parse arguments"));

	users = 0;

#ifdef HAVE_LIBSYSTEMD
	if (sd_booted() > 0)
		users = sd_get_sessions(NULL);
	else {
#endif
#if HAVE_WTSAPI32_H
		if (!WTSEnumerateSessions(WTS_CURRENT_SERVER_HANDLE, 0, 1, &wtsinfo, &wtscount)) {
			printf(_("Could not enumerate RD sessions: %d\n"), GetLastError());
			return STATE_UNKNOWN;
		}

		for (index = 0; index < wtscount; index++) {
			LPTSTR username;
			DWORD size;
			int len;

			if (!WTSQuerySessionInformation(WTS_CURRENT_SERVER_HANDLE, wtsinfo[index].SessionId, WTSUserName, &username, &size))
				continue;

			len = lstrlen(username);

			WTSFreeMemory(username);

			if (len == 0)
				continue;

			if (wtsinfo[index].State == WTSActive || wtsinfo[index].State == WTSDisconnected)
				users++;
		}

		WTSFreeMemory(wtsinfo);
#elif HAVE_UTMPX_H
	/* get currently logged users from utmpx */
	setutxent();

	while ((putmpx = getutxent()) != NULL)
		if (putmpx->ut_type == USER_PROCESS)
			users++;

	endutxent();
#else
	/* run the command */
	child_process = spopen(WHO_COMMAND);
	if (child_process == NULL) {
		printf(_("Could not open pipe: %s\n"), WHO_COMMAND);
		return STATE_UNKNOWN;
	}

	child_stderr = fdopen(child_stderr_array[fileno(child_process)], "r");
	if (child_stderr == NULL)
		printf(_("Could not open stderr for %s\n"), WHO_COMMAND);

	while (fgets(input_buffer, MAX_INPUT_BUFFER - 1, child_process)) {
		/* increment 'users' on all lines except total user count */
		if (input_buffer[0] != '#') {
			users++;
			continue;
		}

		/* get total logged in users */
		if (sscanf(input_buffer, _("# users=%d"), &users) == 1)
			break;
	}

	/* check STDERR */
	if (fgets(input_buffer, MAX_INPUT_BUFFER - 1, child_stderr))
		result = possibly_set(result, STATE_UNKNOWN);
	(void)fclose(child_stderr);

	/* close the pipe */
	if (spclose(child_process))
		result = possibly_set(result, STATE_UNKNOWN);
#endif
#ifdef HAVE_LIBSYSTEMD
	}
#endif

	/* check the user count against warning and critical thresholds */
	result = get_status((double)users, thlds);

	if (result == STATE_UNKNOWN)
		printf("%s\n", _("Unable to read output"));
	else {
		printf(_("USERS %s - %d users currently logged in |%s\n"), state_text(result), users,
			   sperfdata_int("users", users, "", warning_range, critical_range, true, 0, false, 0));
	}

	return result;
}

/* process command-line arguments */
int process_arguments(int argc, char **argv) {
	static struct option longopts[] = {{"critical", required_argument, 0, 'c'},
									   {"warning", required_argument, 0, 'w'},
									   {"version", no_argument, 0, 'V'},
									   {"help", no_argument, 0, 'h'},
									   {0, 0, 0, 0}};

	if (argc < 2)
		usage("\n");

	int option_char;
	while (true) {
		int option = 0;
		option_char = getopt_long(argc, argv, "+hVvc:w:", longopts, &option);

		if (option_char == -1 || option_char == EOF || option_char == 1)
			break;

		switch (option_char) {
		case '?': /* print short usage statement if args not parsable */
			usage5();
		case 'h': /* help */
			print_help();
			exit(STATE_UNKNOWN);
		case 'V': /* version */
			print_revision(progname, NP_VERSION);
			exit(STATE_UNKNOWN);
		case 'c': /* critical */
			critical_range = optarg;
			break;
		case 'w': /* warning */
			warning_range = optarg;
			break;
		}
	}

	option_char = optind;

	if (warning_range == NULL && argc > option_char)
		warning_range = argv[option_char++];

	if (critical_range == NULL && argc > option_char)
		critical_range = argv[option_char++];

	/* this will abort in case of invalid ranges */
	set_thresholds(&thlds, warning_range, critical_range);

	if (!thlds->warning) {
		usage4(_("Warning threshold must be a valid range expression"));
	}

	if (!thlds->critical) {
		usage4(_("Critical threshold must be a valid range expression"));
	}

	return OK;
}

void print_help(void) {
	print_revision(progname, NP_VERSION);

	printf("Copyright (c) 1999 Ethan Galstad\n");
	printf(COPYRIGHT, copyright, email);

	printf("%s\n", _("This plugin checks the number of users currently logged in on the local"));
	printf("%s\n", _("system and generates an error if the number exceeds the thresholds specified."));

	printf("\n\n");

	print_usage();

	printf(UT_HELP_VRSN);
	printf(UT_EXTRA_OPTS);

	printf(" %s\n", "-w, --warning=RANGE_EXPRESSION");
	printf("    %s\n", _("Set WARNING status if number of logged in users violates RANGE_EXPRESSION"));
	printf(" %s\n", "-c, --critical=RANGE_EXPRESSION");
	printf("    %s\n", _("Set CRITICAL status if number of logged in users violates RANGE_EXPRESSION"));

	printf(UT_SUPPORT);
}

void print_usage(void) {
	printf("%s\n", _("Usage:"));
	printf("%s -w <users> -c <users>\n", progname);
}
