/*
   asst04.cpp
   7/6/2005
   CIS 150
   David G. Klick
   
   Solution to assignment #4.
*/

#include <iostream>
#include <iomanip>
using std::cin;
using std::cout;
using std::fixed;
using std::showpoint;
using std::setprecision;

// function prototypes
char getChoice(char* prompt, char* allowed);
void displayMenu(char* menu);
double calcRectangle();
double calcTriangle();
double calcCircle();
double calcHexagon();
double getDouble(char* prompt, double min, double max);

int main(void) {
   char choice;
   double area;
   bool valid;
   
   char *menu = "Area Calculator Menu:\n\n"
      "   (R)ectangle\n\n"
      "   (C)ircle\n\n"
      "   (H)exagon\n\n"
      "   (T)riangle\n\n"
      "   E(x)it\n\n";
   
   do {
      // display menu
      displayMenu(menu);
	  
      // get user choice
      choice = getChoice("Enter choice: ", "RrCcTtHhXx");
      choice = toupper(choice);
      valid = true;
	  
      // process choice
      switch (choice) {
      case 'R':
         area = calcRectangle();
         break;
	   case 'C': 
         area = calcCircle();
         break;
      case 'H':
         area = calcHexagon();
         break;
      case 'T':
         area = calcTriangle();
         break;
      default:
         valid = false;
      }

      // display area if appropriate
      if (valid) {
         cout << "The area is " << fixed << showpoint
              << setprecision(2) << area << "\n\n";
      }

   // continue while user did not choose to exit
   } while (choice != 'X');

   return 0;
}

void displayMenu(char *mnu) {
   cout << mnu;
}	

char getChoice(char *prompt, char *allowed) {
   char ch;
   char *ptr;
   do {
      cout << prompt;
      cin >> ch;
      ptr = strchr(allowed, (int)ch);
      if (ptr == NULL) {
         cout << "Error: Invalid choice\n";
      }
   } while (ptr == NULL);
   return ch;
}

double calcRectangle() {
   double length, width;
   length = getDouble("Enter length (0-300): ", 0.0, 300.0);
   width = getDouble("Enter width (0-300): ", 0.0, 300.0);
   return length * width;
}   

double calcTriangle() {
   double height, base;
   height = getDouble("Enter height (0-200): ", 0.0, 200.0);
   base = getDouble("Enter base (0-200): ", 0.0, 200.0);
   return 0.5 * height * base;
}   

double calcCircle() {
   const double PI = 3.1415926536;
   double radius;
   radius = getDouble("Enter radius (0-250): ", 0.0, 250.0);
   return PI * radius * radius;
}   

double calcHexagon() {
   double side;
   side = getDouble("Enter side (0-200): ", 0.0, 200.0);
   return side * side * 2.598075;
}   

double getDouble(char *prompt, double min, double max) {
   double num;
   do {
      cout << prompt;
      cin >> num;
      if (num<min) {
         cout << "Error: Input below minimum\n";
      } else if (num>max) {
         cout << "Error: Input above maximum\n";
      }
   } while (num<min || num>max);
   return num;
}