//
// Program name:  modified_quiz05_pgm
// Author:  B. Massingill
//
// Purpose:  compute perimeter of a triangle with vertices specified
//	as points in 2D space
//
// Input:  
//	three pairs of (x, y) coordinates representing three points in
//	2D space
// Output:  
//	perimeter of the triangle formed by the three points
//
#include <iostream.h>

// **** function prototypes and comments ****

// function to obtain two integers from standard input, prompting user
// precondition:
//	msg = string to use in prompting user
// postcondition:
//	x, y are integers read from standard input
// notes:
//	user is prompted with message "Please enter " plus msg.
//	if what is entered is not two integers, program displays
//	error message and tries again, continuing until it obtains
//	two integers.
void obtain2Integers(const char msg[], int& x, int& y);

// function to compute 2D distance
// precondition:
//	(x1, y1) and (x2, y2) are coordinates of two points in
//	2D space
// postcondition:
//	return value is distance between (x1, y1) and (x2, y2)
double twoDdistance(int x1, int y1, int x2, int y2);

// helper function for obtain2Integers
// precondition:
//	none
// postcondition:
//	return value is an integer read from standard input
// notes:
//	if next thing read is not an integer, program displays error
//	message and tries again, continuing until it reads an integer.
int obtainInteger(void);

// **** main program ****

int main()
{
	int x1, y1, x2, y2, x3, y3;

	obtain2Integers("x, y coordinates for point 1", x1, y1);
	obtain2Integers("x, y coordinates for point 2", x2, y2);
	obtain2Integers("x, y coordinates for point 3", x3, y3);

	cout << "perimeter is " <<
		twoDdistance(x1, y1, x2, y2) +
		twoDdistance(x2, y2, x3, y3) +
		twoDdistance(x3, y3, x1, y1) << endl;

	return 0 ;
}

// **** function definitions ****

void obtain2Integers(const char msg[], int& x, int& y)
{	
	cout << "Please enter " << msg << ":  ";
	x = obtainInteger();
	y = obtainInteger();
}

// modified version of obtainInteger from ASCII art program
int obtainInteger(void)
{
    int c;
    char ignoredChar;
    bool goodInput = false;
    do {
      if (cin >> c) {
	goodInput = true;
      }
      else {
	cerr << "Please enter an integer!\n";
	if (cin.eof())		// received Control-D!
	  cin.clear();
	else {			// received a non-integer
	  cin.clear();
	  cin.get(ignoredChar);
	}
      }
    } while (!goodInput);
    return c;
}

double twoDdistance(int x1, int y1, int x2, int y2)
{
	return sqrt((x1-x2)*(x1-x2) + (y1-y2)*(y1-y2));
}