// Program 4.4; Calculator with for loop
#include <stdio.h>
#include <ctype.h>
#include <stdbool.h>

bool first = true;
bool exited = false;

long double eq = 0.0L;
double op = 0.0;

char operation, choice;

long double calculate(long double eq, double op, char operation);
bool cont();

int main(void){
    // Welcome words
    printf("Hello, it\'s my calculator on C via for loop.\n");
    printf("Please choice your opeartion to do");

    for( ;; ){
        // Loop to choose operation
        printf("\n\t1. Plus\n\t2. Minus\n\t3. Multiplication\n\t4. Division\n\t5. Exit\nYour choice: ");
        scanf("%c", &operation);
        // Exit if user decided it
        if(operation == '5') {
            printf("\nBye :c\n");
            return 0;
        }

        for( ;; ) {
            // Main loop of calculations
            if((operation >= '6') || (operation <= '0')) {
                // Check on false operations
                printf("\nI don\'t know that command.\n");
                break;
            }
            if(first) {
                // Entering first number
                printf("\nEnter first value: ");
                scanf("%Lf", &eq);
                first = false;
            }
            // Entering second (next) number
            printf("\nAnd: ");
            scanf("%lf", &op);
            // Calculating
            eq = calculate(eq, op, operation);

            printf("\n = %Lf\n", eq);
            exited = cont();
            if(exited) {
                op = 0.0;
                eq = 0.0L;
                first = true;
                break;
            }
        }
    }
    return 0;
}

long double calculate(long double eq, double op, char operation) {
    switch(operation) {
        case '1':
            eq += op;
            break;
        case '2':
            eq -= op;
            break;
        case '3':
            eq *= op;
            break;
        case '4':
            eq /= op;
            break;
    }
    return eq;
}

bool cont() {
    printf("Do you want to continue? [n|y] ");
    scanf("%c", &choice);

    switch(tolower(choice)) {
        case 'y':
            exited = false;
            break;
        case 'n':
            exited = true;
            break;
        default:
            printf("\nI don\'t know that choice, try again.\n");
            cont();
            break;
    }
    return exited;
}