/*
**	ENGR 131, Monday 3:30 Recitation (Amanda Rohn)
**	Homework #3 - Unit Converter
**
**	Solution
*/

#include <iostream>

using std::cout;
using std::cin;
using std::endl;

int main()
{
	cout << "Welcome to the Unit Converter!\n";

	int choice;		//holds user's choice from menus
	char yn;		//holds user's choice of whether to quit ('y','Y','n', or 'N')
	double length;	//holds value in original unit

	do	//main program loop
	{
		for(;;)	//input loop
		{
			cout << "\nWhat unit would you like to convert?\n"
				 << "1. Meters (m)\n"
				 << "2. Miles (mi)\n"
				 << "3. Kilometers (km)\n"
				 << "4. Feet (ft)\n"
				 << "Enter choice: ";

			cin >> choice;

			if(choice >= 1 && choice <= 4) //if choice is valid, go on with program
				break;
			else
				cout << "\nThat was an invalid choice. Try again.\n";
		}	//end input loop

		switch(choice)	//main (choice-to-x) conversion switch statement
		{
		case 1:	//meters
				cout << "\nEnter length in meters: ";
				cin >> length;	//assume user enters a number
			
				for(;;)	//input loop
				{
					cout << "\nWhat unit would you like to convert meters to?\n"
						 << "1. Miles (mi)\n"
						 << "2. Kilometers (km)\n"
						 << "3. Feet (ft)\n"
						 << "Enter choice: ";

					cin >> choice;	//recycle variable
					
					if(choice >= 1 && choice <= 3)
						break;
					else
						cout << "\nInvalid choice. Try again.\n";
				}	//end input loop

				switch(choice)	//meters-to-choice conversion
				{
				case 1:	cout << endl << length << " meters = "
							 << length * .000621	//1 m = .000621 mi
							 << " miles\n\n";
						break;
				case 2:	cout << endl << length << " meters = "
							 << length * .001	//1 m = .001 km
							 << " kilometers\n\n";
						break;
				case 3:	cout << endl << length << " meters = "
							 << length * 3.28	//1 m = 3.28 ft
							 << " feet\n\n";
						break;
				default: cout << "Can't happen!";	//error-checking should've caught this case
				}	//end meters-to-choice conversion

				break;	//end meters case

		case 2: //miles
				cout << "\nEnter length in miles: ";
				cin >> length;	//assume user enters a number
			
				for(;;)	//input loop
				{
					cout << "\nWhat unit would you like to convert miles to?\n"
						 << "1. Meters (m)\n"
						 << "2. Kilometers (km)\n"
						 << "3. Feet (ft)\n"
						 << "Enter choice: ";

					cin >> choice;	//recycle variable
					
					if(choice >= 1 && choice <= 3)
						break;
					else
						cout << "\nInvalid choice. Try again.\n";
				}	//end input loop

				switch(choice)	//miles-to-choice conversion
				{
				case 1:	cout << endl << length << " miles = "
							 << length * 1609	// 1 mi = 1609 m
							 << " meters\n\n";
						break;
				case 2:	cout << endl << length << " miles = "
							 << length * 1.61	// 1 mi = 1.61 km
							 << " kilometers\n\n";
						break;
				case 3:	cout << endl << length << " miles = "
							 << length * 5280	// 1 mi = 5280 ft
							 << " feet\n\n";
						break;
				default: cout << "Can't happen!";	//error-checking should've caught this case
				}	//end miles-to-choice conversion

				break;	//end miles case

		case 3: //kilometers
				cout << "\nEnter length in kilometers: ";
				cin >> length;	//assume user enters a number
			
				for(;;)	//input loop
				{
					cout << "\nWhat unit would you like to convert kilometers to?\n"
						 << "1. Meters (in)\n"
						 << "2. Miles (m)\n"
						 << "3. Feet (ft)\n"
						 << "Enter choice: ";

					cin >> choice;	//recycle variable
					
					if(choice >= 1 && choice <= 3)
						break;
					else
						cout << "\nInvalid choice. Try again.\n";
				}	//end input loop

				switch(choice)	//kilometers-to-choice conversion
				{
				case 1:	cout << endl << length << " kilometers = "
							 << length * 1000	// 1 km = 1000 m
							 << " meters\n\n";
						break;
				case 2:	cout << endl << length << " kilometers = "
							 << length * .62	// 1 km = .62 mi
							 << " miles\n\n";
						break;
				case 3:	cout << endl << length << " kilometers = "
							 << length * 3280	// 1 km = 3280 ft
							 << " feet\n\n";
						break;
				default: cout << "Can't happen!";	//error-checking should've caught this case
				}	//end kilometers-to-choice conversion

				break;	//end kilometers case

		case 4:	//feet
				cout << "\nEnter length in feet: ";
				cin >> length;	//assume user enters a number
			
				for(;;)	//input loop
				{
					cout << "\nWhat unit would you like to convert feet to?\n"
						 << "1. Meters (in)\n"
						 << "2. Miles (m)\n"
						 << "3. Kilometers (km)\n"
						 << "Enter choice: ";

					cin >> choice;	//recycle variable
					
					if(choice >= 1 && choice <= 3)
						break;
					else
						cout << "\nInvalid choice. Try again.\n";
				}	//end input loop

				switch(choice)	//feet-to-choice conversion
				{
				case 1:	cout << endl << length << " feet = "
							 << length / 3.28	// 1 ft = 1/3.28 m
							 << " meters\n\n";
						break;
				case 2:	cout << endl << length << " feet = "
							 << length / 5280	// 1 ft = 1/5280 mi
							 << " miles\n\n";
						break;
				case 3:	cout << endl << length << " feet = "
							 << length / 3280	// 1 ft = 1/3280 km
							 << " kilometers\n\n";
						break;
				default: cout << "Can't happen!";	//error-checking should've caught this case
				}	//end feet-to-choice conversion

				break;	//end feet case

		default: //can't happen 
				cout << "Can't happen";
		}	//end choice-to-x conversion switch statement

	for(;;)
	{
		cout << "Would you like to do another conversion? (Y/N): ";
		cin >> yn;

		if(yn == 'y' || yn == 'Y' || yn == 'n' || yn == 'N')	//valid input
			break;
		else
			cout << "That wasn't a valid answer.\n";	//ask again
	}
		

	}while(yn == 'y' || yn == 'Y');	//end main loop

	cout << "\nThank you for using the Unit Converter\n";

	return 0;
}	//end program