#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <time.h>
/*
Demonstrates a 2 level menu with
a simple data processing cycle

When faced with the main menu, select 1 then 1 again to
execute the process of calculating area.


Author: Vedesh Kungebeharry
*/


//constants
const double Pi=3.14;


//global static  variables
char choice;


//function declarations
void    initialization();
void    showMainMenu();
void    showMathMenu();
void    runMainMenu();
void    runMathMenu();
void    pause();
void    exitProgram();
void    AreaOfCircleUserInteraction();
double  AreaOfCircle(double radius);

//main flow of control from process to process
int main()
{

    initialization();
    runMainMenu();
    exitProgram();

    return 0;
}


/*
*initialize all instance variables and arrays here
*
*/
void initialization()
{
    choice = '_';
}

//displays the main menu and accepts input
void runMainMenu()
{
    int sentinel=0;//used to break  out of our menu loop
    while (sentinel>=0)//loop menu here
    {
        showMainMenu();//display menu text

        choice = getch();//get a character from the input buffer

        system("@cls");// clear screen after getting input

        switch (choice)//based on the choice take the desired action
        {
            case '1':   printf("\nYou chose Option 1: Math Calculations\n");
                        runMathMenu();//displays the math sub menu and accepts input
                        break;
            case '2':   printf("\nYou chose option 2\n");
                        break;
            case '3':   printf("\nYou chose option 3\n");
                        break;
            case 'q':   printf("\nYou chose to quit\n");
                        sentinel=-1;//update the sentinel so that looping will cease
                        break;
            case 'Q':   printf("\nYou chose to quit\n");//cease if upper case
                        sentinel=-1;
                    break;
            default:
                    printf("\nYou have entered an option that is not in the menu\n");
                    break;


        }
        if(sentinel>=0)//if we have continued regular execution , continue looping
        {
            printf("\nreturning to main menu in 2 seconds...\n");
            pause(2000);
            system("@cls");
        }

    }



}

//shows and accepts input for the math sub menu
void runMathMenu()
{
    int sentinel=0;
    while (sentinel>=0)
    {
        showMathMenu();//show options

        choice = getch();//get a character from the input buffer

        system("@cls");

        switch (choice)
        {
            case '1':   printf("\nYou chose option 1: Area\n");
                        AreaOfCircleUserInteraction();//start interaction to calculate area
                        break;
            case '2':   printf("\nYou chose option 2\n");
                        break;
            case 'r':   printf("\nYou chose to quit\n");
                        sentinel=-1;
                        break;
            case 'R':   printf("\nYou chose to quit\n");
                        sentinel=-1;
                        break;
            default:
                    printf("\nYou have entered an option that is not in the menu\n");
                    break;


        }
        printf("\nreturning to Math menu in 2 seconds...\n");
        pause(2000);
        system("@cls");
    }

}

void showMainMenu()
{
    printf("1. Option 1: Math Calculations\n");
    printf("2. Option 2\n");
    printf("3. Option 3\n");
    printf("Q. Quit    \n");
    printf("\nPlease select an option...");
}

void showMathMenu()
{
    printf("1. Area of circle\n");
    printf("2. Volume of Circle\n");
    printf("R. Return to main menu    \n");
    printf("\nPlease select an option...");
}

//pauses execution
void pause(int milliseconds)
{
    clock_t now = clock();
    while(clock()< now+milliseconds);

}
//prompt user to enter data and output results
void AreaOfCircleUserInteraction()
{
    double area,radius=-999.99;
    printf("Enter the radius...");
    scanf(" %lf", &radius);
    area=AreaOfCircle(radius);
    printf("\nThe area of a circle of radius \t%.2lf is \t%.2lf\n\n",radius,area);
    system("pause");

}
//helper function to calculate area
double AreaOfCircle(double radius)
{
    return Pi*radius*radius;
}
//exit gracefully
void exitProgram()
{
    printf("\nExiting program in 2 seconds...\n");
    pause(2000);

}