desk-reminder/desk_reminder.c

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <linux/input.h>
#include <sys/ioctl.h>
#include <openssl/sha.h>
#include <time.h>
#include <pthread.h>
#include <ctype.h>

// Interval in seconds between reminders (default 20 minutes),
// can be overridden with -i (supports optional s/m suffix).
static unsigned long long interval_seconds = 20ULL * 60ULL;

// Shared timestamp of when the "standing" event last occurred.
static unsigned long long last_time_standing = 0;

// Map a subset of key codes (digits and Enter) to characters.
static char keycode_to_char(unsigned short code)
{
	switch (code) {
	case KEY_0: return '0';
	case KEY_1: return '1';
	case KEY_2: return '2';
	case KEY_3: return '3';
	case KEY_4: return '4';
	case KEY_5: return '5';
	case KEY_6: return '6';
	case KEY_7: return '7';
	case KEY_8: return '8';
	case KEY_9: return '9';
	default:	return '\0';
	}
}

// Thread that once per second prints how long it has been since
// last_time_standing was updated.
static void *time_watcher_thread(void *arg)
{
	(void)arg;
	for (;;) {
		sleep(1);
		unsigned long long now = (unsigned long long)time(NULL);
		 if (last_time_standing != 0) {
			 unsigned long long delta = now - last_time_standing;
			 printf("Seconds since last_time_standing: %llu (interval=%llus)\n",
				 delta, interval_seconds);
			fflush(stdout);
			 // If we've exceeded the configured interval, lock the screen
			 if (delta >= interval_seconds) {
				// Use xinput to disable all keyboard-like devices until user stands again.
				// This pipeline lists input devices, filters keyboards (excluding XTEST),
				// extracts their IDs, and disables each one.
				system("xinput --list --short | "
					   "grep -i 'keyboard' | grep -v 'XTEST' | "
					   "sed -E 's/.*id=([0-9]+).*/\\1/' | "
					   "xargs -r -n1 xinput disable");

				system("i3lock -n -i /usr/local/share/lockscreens/standing_gopher.png");
			}
		}
	}
	return NULL;
}

int main(int argc, char **argv) {
	// Replace with the specific event node for your keyboard
	// Use 'lsusb' and 'cat /proc/bus/input/devices' to find the right one
	const char *dev = "/dev/input/by-id/usb-IC_Reader_IC_Reader_08FF20171101-event-kbd";
	struct input_event ev;
	int fd;

	// Optional: -i <interval>[s|m] to override interval_seconds
	int opt;
	while ((opt = getopt(argc, argv, "i:")) != -1) {
		switch (opt) {
		case 'i': {
			char *end = NULL;
			unsigned long long v = strtoull(optarg, &end, 10);
			if (!optarg[0] || end == optarg || v == 0) {
				fprintf(stderr, "Invalid interval '%s' for -i (must start with positive integer)\n", optarg);
				return EXIT_FAILURE;
			}

			char unit = 'm'; // default unit: minutes
			if (*end != '\0') {
				// Allow a single unit character 's' or 'm'
				if (end[1] != '\0') {
					fprintf(stderr, "Invalid interval suffix in '%s' (use optional 's' or 'm')\n", optarg);
					return EXIT_FAILURE;
				}
				unit = (char)tolower((unsigned char)*end);
				if (unit != 's' && unit != 'm') {
					fprintf(stderr, "Unknown interval unit '%c' in '%s' (use 's' or 'm')\n", *end, optarg);
					return EXIT_FAILURE;
				}
			}

			if (unit == 's') {
				interval_seconds = v;
			} else { // 'm'
				interval_seconds = v * 60ULL;
			}
			break;
		}
		default:
			fprintf(stderr, "Usage: %s [-i interval{s|m}]\n", argv[0]);
			return EXIT_FAILURE;
		}
	}

	fd = open(dev, O_RDONLY);
	if (fd == -1) {
		perror("Cannot open device");
		return EXIT_FAILURE;
	}

	// Grab the device: This blocks all other apps from seeing these keystrokes
	if (ioctl(fd, EVIOCGRAB, 1) == -1) {
		perror("Could not grab device");
		close(fd);
		return EXIT_FAILURE;
	}

	printf("Input blocked from %s. Press Ctrl+C in this terminal to stop.\n", dev);

	// Buffer to accumulate the characters the reader "types"
	char buf_str[128];
	size_t buf_len = 0;

	// Initialize last_time_standing and start the watcher thread
	last_time_standing = (unsigned long long)time(NULL);
	pthread_t watcher;
	if (pthread_create(&watcher, NULL, time_watcher_thread, NULL) != 0) {
		perror("Failed to create watcher thread");
		ioctl(fd, EVIOCGRAB, 0);
		close(fd);
		return EXIT_FAILURE;
	}
	pthread_detach(watcher);
	// Continuous loop to capture events
	while (1) {
		ssize_t n = read(fd, &ev, sizeof(ev));
		if (n == (ssize_t)-1) {
			perror("Read error");
			break;
		} else if (n != sizeof(ev)) {
			continue;
		}
		// Process only key events (type 1)
		if (ev.type == EV_KEY) {
			if (ev.value == 1) { // key press
				if (ev.code == KEY_ENTER || ev.code == KEY_KPENTER) {
					// End of the "typed" sequence: print the accumulated string
					if (buf_len > 0) {
						buf_str[buf_len] = '\0';
						long long val = strtoll(buf_str, NULL, 10);
						// Get the SHA-256 hash of the value
						unsigned char hash[SHA256_DIGEST_LENGTH];
						SHA256((unsigned char*)buf_str, buf_len, hash);
						printf("SHA-256: ");
						unsigned long long hash_val = 0;
						for (int i = 0; i < 8; i++) {
							hash_val = (hash_val << 8) | hash[i];
						}
						printf(" (as number: %llu)", hash_val);
						printf("\n");
						printf("Typed: %s (as number: %lld)\n", buf_str, val);
						buf_len = 0;
						if (hash_val == 4798061567229363866L) {
							last_time_standing = (unsigned long long)time(NULL);
							printf("Desk reminder timer reset at %llu seconds since epoch.\n", last_time_standing);
							system("pkill i3lock");
							system("xinput --list --short | "
								   "grep -i 'keyboard' | grep -v 'XTEST' | "
								   "sed -E 's/.*id=([0-9]+).*/\\1/' | "
								   "xargs -r -n1 xinput enable");
						}
					}
				} else {
					char c = keycode_to_char(ev.code);
					if (c != '\0' && buf_len + 1 < sizeof(buf_str))
						buf_str[buf_len++] = c;
				}
			}
		}
	}

	// Release the grab before exiting
	ioctl(fd, EVIOCGRAB, 0);
	close(fd);
	return 0;
}