//
// Example 5.19. This program computes the amount of money in
// the bank after a certain number of years. It also computes
// how many years it would take to arrive at a given amount.
// The bank compounds interest annually.
//

#include <iostream>
#include <cmath>

using namespace std;

#include "Money.h"

Money readPrincipal();
float readRate();

int main()
{
   int  menu(); 	  // prototypes
   void findAmount();
   void findYears();
   void 	error(int choice);

   int choice; 	          // menu choice

   choice = menu();
   switch (choice)
   {
       case 1:  findAmount();
                break;
       case 2:  	findYears();
                break;
       default: error(choice);
   }

   return 0;
}

//
// This function prints a menu of choices, reads and
// returns the user's integer choice, 1 or 2; all other
// choices are in error.
// Pre: none
// Post: Function has returned user's choice from the menu.
//

int menu()
{
   int choice; 	// menu choice

   cout << "This program makes savings computations for an" << endl;
   cout << "account with interest compounded annually. It will" << endl;
   cout << "ask you the one-time deposit amount and the annual" << endl;
   cout << "interest rate. You have two choices: Given a number" << endl;
   cout << "of years, the program will return the final amount;" << endl;
   cout << "given a final amount, the program will tell the" << endl;
   cout << "number of years you must leave the money in the bank." << endl;
   cout << "Choose from the following: " << endl << endl;
   cout << "1. Given a number of years, calculate amount" << endl;
   cout << "2. Given a desired amount, calculate years" << endl << endl;
   cout << "Your choice: ";

   cin >> choice;
   return choice;
}

//
// This function obtains principal, interest rate, and years of
// deposit; determines if an input error occurs; and if
// not, calculates and prints final amount.
//    amount = principal * (1 + rate)^years
// Pre:  none
// Post: If no errors, final amount has been displayed.
//

void findAmount()
{
   int   readYears();	// prototype
   float rate;			// interest rate
   int   years;			// number of years in bank
   Money principal;			// object for original deposit
   Money zeroDollars;	// object representing $0.00

   principal = readPrincipal();
   rate      = readRate();
   years     = readYears();

   if (principal.lessThan(zeroDollars)  ||
         principal.equalTo(zeroDollars) ||
         (rate <= 0)                    ||
         (years <= 0) )                      //error
	cout << endl << "Invalid input. Run program again." << endl;
   else
   {
	principal.multiplyBy(pow(1 + rate, years));
	cout << endl << "You will have $";
	principal.display();
	cout << " in the bank." << endl;
   }
}

//
// This function obtains principal, interest rate, and amount
// desired; determines if an input error occurs; and if
// not, calculates and prints number of years needed.
//    years = smallest integer greater than or equal to
// 	  log(amount/principal)/log(1 + rate)
// Pre:  none
// Post: The number of years needed or an error message
// 	has been displayed.
//

void findYears()
{
   Money readAmount(void);  // prototype
   float rate;              // interest rate
   int   years;             // number of years in bank
   Money amount;            // final amount in bank
   Money principal;         // original deposit
   Money zeroDollars;       // object representing $0.00

   principal = readPrincipal();
   rate      = readRate();
   amount    = readAmount();

   if ((!principal.lessThan(amount))     ||
         principal.equalTo(zeroDollars)  ||
         principal.lessThan(zeroDollars) ||
         (rate <= 0)) 	        //error
	cout << endl << "Invalid input. Run program again" << endl;
   else
   {
       years = ceil(log(amount.quotient(principal))
                  / log(1 + rate));
       cout << endl << "You will need the account for "
             << years << " years." << endl;
   }
}

//
// This function reads and returns principal
// Pre:  none
// Post: The Money object for the principal was returned.

Money readPrincipal()
{
   double deposit; // principal as a double


   cout << endl << "Give the original deposit: ";
   cin  >> deposit;
   Money principal(deposit); // original deposit object
   return principal;
}


//
// This function reads and returns interest rate, -1 in
// case of error
// Pre:  none
// Post: Floating point interest rate has been returned, -1
// 	in case of error.
//

float readRate()
{
   float rate; 	// interest rate


   cout << "Give the interest rate as a decimal number" << endl;
   cout << " 	For example, for 6.25% type 0.0625: ";
   cin  >> rate;
   if ((rate <= 0.0) || (rate >= 0.2)) 	// error
	rate = -1;
   return rate;
}

//
// This function reads and returns years of deposit
// Pre:  none
// Post: Years of deposit have been returned.
//

int readYears()
{
   int years; 	// number of years in bank


   cout << "Number of years to leave in bank: ";
   cin  >> years;
   return years;
}

//
// This function reads and returns the amount desired
// Pre:   none
// Post: The Money object for the amount desired was returned.
//

Money readAmount()
{
   double desired;  	// amount desired


   cout << "Give the amount desired: ";
   cin  >> desired;
   Money amount(desired); // object for amount desired
   return amount;
}

//
// This function prints an error message for an invalid
// menu choice
// Pre: 	 choice has an invalid value.
// Post: Error message is displayed.
//

void error(int choice)
{
   cout << choice << " is an invalid choice. Please run again." << endl;
}