#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <setjmp.h>

/*
 * SIGFPE bisa nempel di CPU, perlu dicari solusi
 * Test openssl lewat socat
 */

void signal_handler(int sig)
{
    signal(SIGFPE, signal_handler);
    system("/bin/sh");
    exit(1);
}

int main(int argc, char const *argv[])
{
    int i_a = 0;
    int i_b = 0;
    int total = 0;

    setvbuf(stdin, NULL, _IONBF, 0);
    setvbuf(stdout, NULL, _IONBF, 0);
    setvbuf(stderr, NULL, _IONBF, 0);
    
    signal(SIGFPE, signal_handler);

    puts("Welcome to Online Calculator v3.1");
    puts("");
    puts("Operator supported: + - * /");
    puts("ex: 2 + 2");
    puts("ex: 2 + a  //'a' to use last results");
    puts("");
    puts("------------------------------------");

    while (1)
    {
        char c_a[11] = "";
        char c_b[11] = "";
        char opt = 0;
        printf(">");

        if (scanf("%10s %c %10s", c_a, &opt, c_b) < 3)
        {
            puts("Failed to parse expression!");
            return 0;
        }
        else
        {
            int r1_a = sscanf(c_a, "%d", &i_a);
            int r2_a = strcmp("a", c_a) == 0;
            int r1_b = sscanf(c_b, "%d", &i_b);
            int r2_b = strcmp("a", c_b) == 0;

            if ((i_b == 0 && r2_a) && opt == '/')
            {
                puts("Floating point exception (core dumped)");
                return 0;
            }

            if (r2_a)
            {
                i_a = total;
            }

            if (r2_b)
            {
                i_b = total;
            }

            if ((r1_a || r2_a) && (r1_b || r2_b))
            {
                switch (opt)
                {
                case '+':
                    total = i_a + i_b;
                    break;
                case '-':
                    total = i_a - i_b;
                    break;
                case '*':
                    total = i_a * i_b;
                    break;
                case '/':
                    total = i_a / i_b;
                    break;
                default:
                    puts("Unknown operator!");
                    return 0;
                }
                printf("=%d\n", total);
            }
            else
            {
                puts("Failed to parse operand!");
                return 0;
            }
        }
    }
    return 0;
}