///////////////////////////////////
//
// program_4 project
//
// created 8/12/21 by tj
// rev 0
//
///////////////////////////////////
//
// Program to provide various calculations w/ functions w/pointers
//
// Reads in a values for val1 and val2
// Reads in the desired operation
// Provides the result
//
// inputs: 2 values for val1 and val2, a character for the operation
// outputs: prints result of val1 operation val2
//
///////////////////////////////////

#include "mbed.h"
#include <stdio.h>                      // only needed when printing
#include <math.h>                       // needed for NaN

// function prototypes
void get_vals(float * value_l, float * value_r);
void get_op(char * op);
uint8_t check_op(char op);
void calc_result(float val_l, float val_r, char oper, float * result);
void print_results(float val_l, float val_r, char oper, float result);

int main(void){
    setbuf(stdout, NULL);  // disable buffering when printing

    // splash 
    printf("\n\nprogram_4\n");
    printf("Using Mbed OS version %d.%d.%d\n\n", 
            MBED_MAJOR_VERSION, MBED_MINOR_VERSION, MBED_PATCH_VERSION);
    printf("Welcome to my calculator program (using functions and pointers)\n\n");
    
    float val1;
    float val2;
    char operation;
    uint8_t legal;
    float answer;

    // infinte loop
    while(1){       
        // ask for and read in values and operation
        get_vals(&val1, &val2);
        get_op(&operation);
        
        // check if operation is legal
        legal = check_op(operation);
        
        // control printing
        if(legal){
            // perform the calculation
            calc_result(val1, val2, operation, &answer);
        
            // print the eqn and results
            print_results(val1, val2, operation, answer);
        } else {
            printf("illegal operation\n\n");
        }// end if

    }// end while
            
   return 0;
}// end main

void get_vals(float * value_l, float * value_r){
    
    // ask for and read in values
    printf("Please enter a value for the left side of the operation ");
    scanf("%f", value_l);
    printf("Please enter a value for the right side of the operation ");
    scanf("%f", value_r); 
       
    return ;
}// end get_val

void get_op(char * op){
    
    // ask for and read in operation
    printf("Please enter the operation requested \(+ - * /): ");
    scanf(" %c", op);
    
    return;
}// end get_op

uint8_t check_op(char op){
    // return 1 if legal, 0 if not
    if(op == '+' || op == '-' || op == '*' || op == '/')
        return 1;
    else
        return 0;
}// end check_op

void calc_result(float val_l, float val_r, char oper, float * result){
    // select the calculation and execute
    switch(oper){
        case '+':
            *result = val_l + val_r;
            break;
        case '-':
            *result = val_l - val_r;
            break;
        case '*':
            *result = val_l * val_r;
            break;
        case '/':
            *result = val_l / val_r;
            break;
        default:
            *result = 0;
            break;
    } // end switch 
    
    return;
}// end calc_results   
    
void print_results(float val_l, float val_r, char oper, float result){
    
    printf("%f %c %f = %f\n\n", val_l, oper, val_r, result);

    return;
}// end print_results