/*
	Programmer: Chris Gountanis
	Date: 02/08/2008
	Program Name: LoanCalculator.java for Week 3 IA
	Description: Program asks user for input amount of the loan, 
		the interest rate and the number of years. The program 
		validates the input checking for valid numeric data before 
		continuing. If the interest rate was entered in percentage 
		form it converts to decimal before calculation process. The 
		program then calculates the monthly payment. Input values and
		payment total are displayed rounded to the second decimal place.
*/

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class LoanCalculator {
	public static void main(String[] args) throws IOException {
		
		//declarations
		BufferedReader dataIn = new BufferedReader(new  InputStreamReader(System.in));
		double payment=0, interestrate=0, loanamount=0, years=0;
		String inputvalue="";
		
		//get input for loan amount
		while (!isNumeric(inputvalue)) {
			System.out.println("Loan Amount? ");
			inputvalue = dataIn.readLine();
		}
		loanamount = Float.parseFloat(inputvalue);
		
		//get input for interest rate
		inputvalue="";
		while (!isNumeric(inputvalue)) {
			System.out.println("What is the Annual Interest Rate? ");
			inputvalue = dataIn.readLine();
		}
		interestrate = Float.parseFloat(inputvalue);
		
		//get input for the number of years
		inputvalue="";
		while (!isNumeric(inputvalue)) {
			System.out.println("How many Years? ");
			inputvalue = dataIn.readLine();
		}
		years = Float.parseFloat(inputvalue);
		
		//if the interest rate was entered in as percentage convert to decimal
		if (interestrate > 1) {
			interestrate = interestrate / 100;
		}

		//calculate the monthly payment total
		payment =  (interestrate * loanamount / 12) / (1.0 - Math.pow(((interestrate / 12) + 1.0), (-(12 * years))));

		//output the total and input values
		System.out.print("\nThe Loan Amount:\t\t$" + loanamount);
		System.out.print("\nThe Interest Rate:\t\t" + Round(interestrate * 100, 2) + "%");
		System.out.print("\nThe Number of Years:\t\t" + years + " (Months: " + years * 12 + ")");
		System.out.print("\n\nThe Monthly Payment:\t\t$" + Round(payment, 2));
	}

	//used to validate for numeric data
	private static boolean isNumeric(String str){
		try {
			Float.parseFloat(str);
			return true;
		} catch (NumberFormatException nfe){
			return false;
		}
	}
	
	//used to round to a certain number of decimal places
	public static float Round(double Rval, int Rpl) {
		float p = (float)Math.pow(10, Rpl);
		Rval = Rval * p;
		float tmp = Math.round(Rval);
		return (float)tmp/p;
	}
}