#include <stdio.h>
#include <stdlib.h>

double celToKel(double cel){
    return cel + 273.0;
}

double kelToCel(double kel){
    return kel - 273.0;
}

double celToFahr(double cel){
    return cel * 1.8 + 32.0;
}

double fahrToCel(double fahr){
    return (fahr - 32) / 1.8;
}

void absoluteZero(double kelvin){
    if(kelvin < 0){
        printf("WARNING! %.2f is below 0 Kelvin which is impossible - 0 Kelvin is Absolute Zero!\n Where molecules don't move.", kelvin);
        exit(1);
    }
}

void usage(char * app){
    printf("USAGE:\n\t%s <temperature value> [c|C|f|F|k|k]\n", app);
    exit(1);
}

int main(int argc, char * argv[]) {
    if(argc != 3){
        usage(argv[0]);
    }

    double inputTemp = atof(argv[1]);
    double fahrenheit = 0.0;
    double celsius = 0.0;
    double kelvin = 0.0;

    switch (argv[2][0]){
        case 'c':
        case 'C':
            celsius = inputTemp;
            fahrenheit = celToFahr(celsius);
            kelvin = celToKel(celsius);
            absoluteZero(kelvin);
            break;
        case 'f':
        case 'F':
            fahrenheit = inputTemp;
            celsius = fahrToCel(fahrenheit);
            kelvin = celToKel(celsius);
            absoluteZero(kelvin);
            break;
        case 'k':
        case 'K':
            kelvin = inputTemp;
            absoluteZero(kelvin);
            celsius = kelToCel(kelvin);
            fahrenheit = celToFahr(celsius);
            break;
        default:
            usage(argv[0]);
    }

    printf("temperature:\n\t%.2f Kelvin\n\t%.2f Celsius\n\t%.2f Fahrenheit\n", kelvin, celsius, fahrenheit);
    return 0;
}