import java.util.Scanner;

/*********************************************************************
 *
 * @author Duncan Buell
**/
public class Loan
{
  private double monthlyPayment,principal,rate;

/*********************************************************************
 * This is the standard constructor, which ought for good form's sake
 * to explicitly initialize the instance variables for the class. 
**/
  public Loan()
  {
    this.monthlyPayment = 0.0;
    this.principal = 0.0;
    this.rate = 0.0;
  } // public Loan()

/*********************************************************************
 * accessor methods for the instance variables
**/
/*********************************************************************
 * This method simply returns the double precision value of the 
 * monthly payment.
 *
 * @return The double value that is the monthly loan payment.
**/
  public double getMonthlyPayment()
  {
    return(this.monthlyPayment);
  }

/*********************************************************************
 * This method simply returns the double precision value of the current
 * loan principal.
 *
 * @return The double value that is the current loan principal.
**/
  public double getPrincipal()
  {
    return(this.principal);
  }

/*********************************************************************
 * This method simply returns the double precision value of the loan
 * interest rate.
 *
 * @return The double value that is the loan interest rate.
**/
  public double getRate()
  {
    return(this.rate);
  }

/*********************************************************************
 * mutator methods for the instance variables
**/
/*********************************************************************
 * This method takes an input string, converts to a double, and sets
 * that double value as the monthly payment amount of the loan.
 * It SHOULD be the case that extensive error testing is done in this
 * method to determine that in fact the input string represents a legal
 * value for a double.  However, we don't do that here.
 *
 * @param The (String) value of what is supposed to be a double.
 * @return A boolean false if the input was illegal, else true.
**/
  public boolean setMonthlyPayment(String inString)
  {
    boolean returnValue;
    double convertedValue;

    convertedValue = Double.valueOf(inString);
    returnValue = false;
    if(convertedValue > 0.0)
    {
      this.monthlyPayment = convertedValue;
      returnValue = true;
    }

    return(returnValue);
  } // public boolean setMonthlyPayment(String inString)

/*********************************************************************
 * This method takes an input string, converts to a double, and sets
 * that double value as the prinicpal amount of the loan.
 * Same comments about error checking as for the monthly payment.
 *
 * @param The (String) value of what is supposed to be a double.
 * @return A boolean false if the input was illegal, else true.
**/
  public boolean setPrincipal(String inString)
  {
    boolean returnValue;
    double convertedValue;

    convertedValue = Double.valueOf(inString);
    returnValue = false;
    if(convertedValue > 0.0)
    {
      this.principal = convertedValue;
      returnValue = true;
    }

    return(returnValue);
  } // public boolean setPrincipal(String inString)

/*********************************************************************
 * This method takes an input string, converts to a double, and sets
 * that double value as the interest rate of the loan.
 * Same comments about error checking as for the monthly payment.
 *
 * @param The (String) value of what is supposed to be a double.
 * @return A boolean false if the input was illegal, else true.
**/
  public boolean setRate(String inString)
  {
    boolean returnValue;
    double convertedValue;

    convertedValue = Double.valueOf(inString);
    returnValue = false;
    if(convertedValue > 0.0)
    {
      this.rate = convertedValue;
      returnValue = true;
    }

    return(returnValue);
  } // public boolean setRate(String inString)

/*********************************************************************
 * general methods
**/
/*********************************************************************
 * This method amortizes the loan until the principal balance is zero.
 * NOTE: This assumes monthly calculation of interest, without regard
 * to the number of days in a month, etc.
**/
  public void amortize()
  {
    int month;
    double interestThisMonth,newPrincipal;

    System.out.printf("Mon OldPrinc     Int  NewPrinc%n");
    month = 0;
    while(this.principal > 0.0)
    {
      ++month;
      interestThisMonth = this.principal * (this.rate/100.0) / 12.0;
      newPrincipal = this.principal + interestThisMonth - this.monthlyPayment;
      System.out.printf("%3d %10.2f %10.2f %10.2f%n",
                         month,principal,interestThisMonth,newPrincipal);
      this.principal = newPrincipal;

      if(month > 360)
      {
        System.out.printf("ERROR:  Number of months is > 360.  ");
        System.out.printf("This program only works for loans of 30 years or less%3n");
        System.exit(0);
      }
    }
  } // public void amortize()

/*********************************************************************
 * This method gets the monthly payment amount from the input console.
 * Note that the input value is checked for validity.
**/
  public void inputMonthlyPayment(Scanner console)
  {
    boolean goodData;
    String inputString = null;

    System.out.printf("Input loan payoff in dollars: ");
    inputString = console.next();
    goodData = this.setMonthlyPayment(inputString);
    if(false == goodData)
    {
      System.out.println("ERROR: input value " + inputString + " is not valid for the payoff");
      System.exit(0);
    }
    else
    {
      System.out.println("Loan payoff is: " + this.getMonthlyPayment());
    }

  } // public void inputMonthlyPayment(Scanner console)

/*********************************************************************
 * This method gets the principal amount from the input console.
 * Note that the input value is checked for validity.
**/
  public void inputPrincipal(Scanner console)
  {
    boolean goodData;
    String inputString = null;

    System.out.printf("Input loan principal in dollars: ");
    inputString = console.next();
    goodData = this.setPrincipal(inputString);
    if(false == goodData)
    {
      System.out.println("ERROR: input value " + inputString + " is not valid for the principal");
      System.exit(0);
    }
    else
    {
      System.out.println("Loan principal is: " + this.getPrincipal());
    }
  } // public void inputPrincipal(Scanner console)

/*********************************************************************
 * This method gets the loan rate from the input console.
 * Note that the input value is checked for validity.
**/
  public void inputRate(Scanner console)
  {
    boolean goodData;
    String inputString = null;

    System.out.printf("Input loan rate (input '5' for '5.0%%': ");
    inputString = console.next();
    goodData = this.setRate(inputString);
    if(false == goodData)
    {
      System.out.println("ERROR: input value " + inputString + " is not valid for the rate");
      System.exit(0);
    }
    else
    {
      System.out.println("Loan rate is: " + this.getRate());
    }
  } // public void inputRate(Scanner console)

} // public class Loan