// header files
#include "Console_IO_Utility.h"
#include <math.h>
#include <stdio.h>

// global constants
const double PERCENTAGE_CONVERSION = .01;

const int MONTHS_IN_YEAR = 12;
const int TWO_DIGITS = 2;
const int TWO_ENDLINES = 2;

const char PERCENT_CHAR = '%';

// prototypes
   // none

// main program
int main()
   {
    // initialize function/variables

       // initialize variables
       double purchasePrice, downPayment, interestRate, borrowedAmount;
       double monthlyInterest, paymentNumerator, paymentDenominator;
       double monthlyPayment, totalOfPayments, interestPaid, totalPurchasePrice;
       int numYears, numPayments;

       // show title
          // function: printString, printEndline(s)
       printEndline();
       printString( "Monthly Payment Calculator" );
       printEndline();
       printString( "==========================" );
       printEndlines( TWO_ENDLINES );

    // get input

       // show data entry
          // function: printString, printEndline(s)
       printString( "Data Entry" );
       printEndline();
       printString( "----------" );
       printEndlines( TWO_ENDLINES);

       // get purchase price
          // function: promptForDouble
       purchasePrice = promptForDouble( "Enter the purchase price       ($): " );

       // get down payment
          // function: promptForDouble
       downPayment = promptForDouble(  "Enter the down payment         ($): " );

       // get annual interest rate
          // function: promptForDouble
       interestRate = promptForDouble(  "Enter the annual interest rate (%): " );

       // get number of years
          // function: promptForInteger
       numYears = promptForInteger(  "Enter the number of years      (Y): " );

    // COMPLETE: process data, calculate payment

       // calculate borrowed amount (aka principal),
       // using the purchasePrice and subtract the downPayment.
       borrowedAmount = purchasePrice - downPayment;

       // calculate monthly interest, dividing the annual interest rate by 12.
       monthlyInterest = (interestRate*PERCENTAGE_CONVERSION) / MONTHS_IN_YEAR;

       // calculate number of payments, using years times 12 for num payments.
       numPayments = numYears * MONTHS_IN_YEAR;

       // calculate payment numerator, using mortgage equation
       paymentNumerator = pow((1.0 + monthlyInterest), numPayments);

       // calculate payment denominator, using mortgage equation
          // function: pow
       paymentDenominator = pow((1.0 + monthlyInterest), numPayments) - 1.0;

       // calculate payment, dividing the rest of the loan between months.
       monthlyPayment = (borrowedAmount * monthlyInterest)
                   * (paymentNumerator/paymentDenominator);

       // calculate total of all payments,
       // multiply the monthly payment by the amount of payments
       totalOfPayments = monthlyPayment * numPayments;

       // calculate interest paid,
       // take the total payments and subtract the borrowed amount.
       interestPaid = totalOfPayments - borrowedAmount;

       // calculate total purchase price,
       // adding the amount of total of all payments, added to down payment.
       totalPurchasePrice = totalOfPayments + downPayment;

    // show results

       // show title
          // functions: printString, printEndline(s)
       printEndline();
       printString( "Calculation Results" );
       printEndline();
       printString( "-------------------" );
       printEndline();

       // show total purchase price
          // functions: printString, printDouble, printEndline(s)
       printEndline();
       printString( "Total Principal       : $" );
       printDouble( borrowedAmount, TWO_DIGITS );
       printEndline();

       // show down payment
          // functions: printString, printDouble, printEndline(s)
       printEndline();
       printString( "Down Payment          : $" );
       printDouble( downPayment, TWO_DIGITS );
       printEndline();

       // show annual interest rate
          // functions: printString, printDouble, printCharacter, printEndline(s)
       printEndline();
       printString( "Annual Interest Rate  : " );
       printDouble( interestRate, TWO_DIGITS );
       printCharacter( PERCENT_CHAR );
       printEndline();

       // show total number of payments
          // functions: printString, printInteger, printEndline(s)
       printEndline();
       printString( "Number of Payments    : " );
       printInteger( numPayments );
       printEndline();

       // show monthly payment
          // functions: printString, printDouble, printEndline(s)
       printEndline();
       printString( "Monthly Payment       : $" );
       printDouble( monthlyPayment, TWO_DIGITS );
       printEndline();

       // show total interest paid
          // functions: printString, printDouble, printEndline(s)
       printEndline();
       printString( "Total Interest Paid   : $" );
       printDouble( interestPaid, TWO_DIGITS );
       printEndline();

       // show total cost of loan
          // functions: printString, printDouble, printEndline(s)
       printEndline();
       printString( "Total Cost of Loan    : $" );
       printDouble( totalOfPayments, TWO_DIGITS );
       printEndline();

       // show total purchase price
          // functions: printString, printDouble, printEndline(s)
       printEndline();
       printString( "Total Purchase Price  : $" );
       printDouble( totalPurchasePrice, TWO_DIGITS );
       printEndline();

    // end program

       // show end program
          // function: printString, printEndline
       printEndline();
       printString( "End Program" );
       printEndline();

       // return program success
       return 0;
   }


// supporting functions
   // none