// From "Professional Java Server Programming", Patzer et al.,
// pg 51.

// Import Servlet Libraries
import javax.servlet.*;
import javax.servlet.http.*;

// Import Java Libraries
import java.io.*;

// Import html and loan helper classes
// import com.wrox.util.*;

public class JO_LoanCalculator extends HttpServlet
{
   public void doGet (HttpServletRequest req, HttpServletResponse res)
       throws ServletException, IOException
   {

      // retrieve parameter values as strings
      String principalAsString = req.getParameter ("principal");
      String interestAsString  = req.getParameter ("interest");
      String paymentAsString   = req.getParameter ("payment");

      //  initialize variables to hold floating point values
      float principal, interest, payment;

      //  initialize a variable to hold the loan repayment period
      int months;

      try
      {
         // use the JO_LoanTools class to obtain floating point values
         // stringToFloat throws a NumberFormatException, so we'll have
         // to catch it.
         principal = JO_LoanTools.stringToFloat (principalAsString);
         interest  = JO_LoanTools.stringToFloat (interestAsString);
         payment   = JO_LoanTools.stringToFloat (paymentAsString);

         //  use the JO_LoanTools class to calculate the loan period
         //  the method throws an IllegalArgumentException, so we'll have to catch it
         months = JO_LoanTools.calculateLoanPeriod (principal, interest,
                                                    payment);
      }

      // If a NumberFormatException was thrown, we want to
      // replace the error message with something more helpful.
      catch (NumberFormatException e)
      {
         handleError (new NumberFormatException
                     ("Check that the values entered are numeric"), res);
         return;
      }

      // If any other kind of exception was thrown, we catch it here.
      catch (Exception e)
      {
         handleError (e, res);
         return;
      }

      // If no exceptions were thrown, the code continues here
      // so we can send an acknowledgment to the browser.

      res.setContentType ("text/html");
      PrintWriter out = res.getWriter ();

      JO_HTML h = new JO_HTML ("Loan Calculator: Results\n");
      h.add (JO_HTML.HEADING, "Loan Calculator Results", false);
      h.add (JO_HTML.LINE, "", false);
      h.add (JO_HTML.NORMAL, "Principal Amount: $", false);
      h.add (JO_HTML.NORMAL, Float.toString (principal), true);
      h.add (JO_HTML.NORMAL, "Interest:  ", false);
      h.add (JO_HTML.NORMAL, Float.toString (interest), true);
      h.add (JO_HTML.NORMAL, "Payment: $", false);
      h.add (JO_HTML.NORMAL, Float.toString (payment), true);
      h.add (JO_HTML.NORMAL, "Months Until Payoff: ", false);
      h.add (JO_HTML.NORMAL, Integer.toString (months), true);
      out.println (h.getPage ());
      out.close ();

      // The following lines demonstrate logging via
      // the ServletContext log() method

      // ServletContext sc = getServletContext ();
      // sc.log ("Loan period calculated: " + Integer.toString (months));

      // The following line demonstrates logging via
      // the GenericServlet log() method
      // log ("Loan period calculated: " + Integer.toString (months));

   }

   // This version of handleError() sends plain HTML to inform
   // the client of the error.
   private void handleError (Exception e, HttpServletResponse res)
   {

      // You can use res.setStatus () here to inform the client's browser
      // that this response represents an error, not a successful request
      // res.setStatus (400);

      res.setContentType ("text/html");
      try
      {
         PrintWriter out = res.getWriter ();

         JO_HTML h = new JO_HTML ("Loan Calculator: Error");
         h.add (JO_HTML.HEADING, "An error has occured...", false);
         h.add (JO_HTML.LINE, "", false);
         h.add (JO_HTML.NORMAL, e.getMessage (), false);
         out.println (h.getPage ());
         out.close ();
      }
      catch (Exception e1)
      {  // had to add this catch as exception needs to be handled.
         e1.printStackTrace ();
      }
   }

   // This version of handleError () sends an HTTP Error code to inform
   // the client and server of the error.
// private void handleError (Exception e, HttpServletResponse res)
//         throws IOException
// {
//    res.sendError (400, e.getMessage ());
// }

   // This version of handleError () throws a ServletException to inform
   // the client and server of the error.
// private void handleError (Exception e, HttpServletResponse res)
//         throws ServletException
// {
//    throw new ServletException ("Error in Loan Calculator Servlet", e);
// }

}