stage1.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <time.h>
#include <termios.h>
#include <signal.h>
#include <string.h>

static struct termios old_termios, new_termios;

void reset_terminal() {
    printf("\e[m"); // reset color changes
    printf("\e[?25h"); // show cursor
    fflush(stdout);
    tcsetattr(STDIN_FILENO, TCSANOW, &old_termios);
}

void configure_terminal() {
    tcgetattr(STDIN_FILENO, &old_termios);
	new_termios = old_termios; // save it to be able to reset on exit
    
    new_termios.c_lflag &= ~(ICANON | ECHO); // turn off echo + non-canonical mode
    new_termios.c_cc[VMIN] = 0;
    new_termios.c_cc[VTIME] = 0;

    tcsetattr(STDIN_FILENO, TCSANOW, &new_termios);

    printf("\e[?25l"); // hide cursor
    atexit(reset_terminal);
}

static int exit_loop;

void signal_handler(__attribute__((unused)) int signum) {
    exit_loop = 1;
}

int read_key(char* buf, int k) {
    if (buf[k] == '\033' && buf[k + 1] == '[') {
		switch (buf[k + 2]) {
			case 'A': return 1; // UP
			case 'B': return 2; // DOWN
			case 'C': return 3; // RIGHT
			case 'D': return 4; // LEFT
		}
	}
	return 0;
}

int read_input() {
   	char buf[4096]; // maximum input buffer
	int n = read(STDIN_FILENO, buf, sizeof(buf));
	int final_key = 0;
    // it's okay if we miss some keys
    // we will correct it on next frame
	for (int k = 0; k <= n - 3; k += 3) {
		int key = read_key(buf, k);
		if (key == 0) continue;
		final_key = key;
	}
	return final_key;
}

void print_key(int key) {
   	if (key == 1) printf("Up\n");
	if (key == 2) printf("Down\n");
	if (key == 3) printf("Right\n");
	if (key == 4) printf("Left\n");
}

int main() {
    configure_terminal();

    signal(SIGINT, signal_handler);

   	struct timespec req = {};
	struct timespec rem = {};

    while (!exit_loop) {
        int key = read_input();
        print_key(key);

        req.tv_nsec = 0.1 * 1000000000; // 0.1 seconds
        nanosleep(&req, &rem);
    }
}