// Make it easy to access packaged code.

import java.awt.*;
import java.awt.event.*;
import java.applet.*;

/**
 * This class subclasses Applet to define an applet for calculating and
 * displaying the result of compounding an investment. It implements the
 * ActionListener and ItemListener interfaces to respond to events.
 *
 * Written by: Jon Huhtala
 */

public class App extends Applet implements ActionListener, ItemListener {

  // Instance variables for the amount to be invested, the interest rate, and
  // the term in years.

  private double amount;
  private double rate;
  private int term;

  // Instance variables for referencing the amount heading and its text field.

  private Label amountHdg;
  private TextField amountField;

  // Instance variables for referencing the rate heading and its choices.

  private Label rateHdg;
  private Choice rateChoice;

  // Instance variables for referencing the term heading and its choices.

  private Label termHdg;
  private Choice termChoice;

  // Instance variable for referencing the graph to be displayed.

  private Graph graph;

  // This method defines initial (one-time) applet processing.

  public void init() {

    // Set the background color and size for the applet window.

    setSize(250, 350);
    setBackground(Color.lightGray);

    // Declare a label and a text field in which the user may enter the amount
    // to be invested. Add the components to the applet window and register a
    // listener to be notified whenever the user presses the "ENTER" key within
    // the text field.

    amountHdg = new Label("Amount invested");
    add(amountHdg);
    amountField = new TextField(5);
    add(amountField);
    amountField.addActionListener(this);

    // Declare a label and a menu of choices by which the user may select the
    // annual interest rate of the investment. Add the components to the applet
    // window and register a listener to be notified whenever the user makes a
    // selection. The default selection is 8 percent.

    rateHdg = new Label("Annual percentage rate");
    add(rateHdg);
    rateChoice = new Choice();
    rateChoice.addItem("2");
    rateChoice.addItem("3");
    rateChoice.addItem("4");
    rateChoice.addItem("5");
    rateChoice.addItem("6");
    rateChoice.addItem("7");
    rateChoice.addItem("8");
    rateChoice.addItem("9");
    rateChoice.addItem("10");
    rateChoice.addItem("11");
    rateChoice.addItem("12");
    add(rateChoice);
    rateChoice.addItemListener(this);
    rateChoice.select("8");
    rate = .08;

    // Declare a label and a menu of choices by which the user may select the
    // term of the investment. Add the components to the applet window and
    // register a listener to be notified whenever the user makes a selection.
    // The default selection is 10 years.

    termHdg = new Label("Term in years");
    add(termHdg);
    termChoice = new Choice();
    termChoice.addItem("1");
    termChoice.addItem("2");
    termChoice.addItem("3");
    termChoice.addItem("4");
    termChoice.addItem("5");
    termChoice.addItem("6");
    termChoice.addItem("7");
    termChoice.addItem("8");
    termChoice.addItem("9");
    termChoice.addItem("10");
    termChoice.addItem("15");
    termChoice.addItem("20");
    termChoice.addItem("25");
    termChoice.addItem("30");
    termChoice.addItem("35");
    termChoice.addItem("40");
    termChoice.addItem("45");
    termChoice.addItem("50");
    add(termChoice);
    termChoice.addItemListener(this);
    termChoice.select("10");
    term = 10;

    // Instantiate a graph object for displaying the result of compounding and
    // add it to the applet window.

    graph = new Graph();
    add(graph);
  }

  // This method implements the abstract event handler method of the
  // ActionListener interface to handle ActionEvents.

  public void actionPerformed(ActionEvent e) {

    // If the user pressed the "ENTER" key in the amount text field and the
    // field isn't empty, get the String from the field, strip leading and
    // trailing spaces, convert it to a primitive value, and store it.
    // Otherwise, set the amount to zero.

    if (e.getSource().equals(amountField)) {
      if (amountField.getText().trim().length() > 0) {
        amount = Double.parseDouble(amountField.getText().trim());
      }
      else {
        amount = 0;
      }
    }

    // Draw the graph.

    drawGraph();
  }

  // This method implements the abstract event handler method of the
  // ItemListener interface to handle ItemEvents (selections from a Choice).

  public void itemStateChanged(ItemEvent e) {

    // If the amount text field isn't empty, get the String from the amount
    // text field, strip leading and trailing spaces, convert it to a primitive
    // value, and store it. Otherwise, set the amount to zero.

    if (amountField.getText().trim().length() > 0) {
      amount = Double.parseDouble(amountField.getText().trim());
    }
    else {
      amount = 0;
    }

    // If the user selected an item from the rate menu choices, get the object,
    // convert it to a String with no leading or trailing spaces, convert it to
    // its primitive value, divide by 100 to convert to a percentage, and store
    // it.

    if (e.getSource().equals(rateChoice)) {
      rate = Double.parseDouble(rateChoice.getSelectedItem())/100;
    }

    // If the user selected an item from the term menu choices, get the object,
    // convert it to a String with no leading or trailing spaces, convert it to
    // its primitive value, and store it.

    if (e.getSource().equals(termChoice)) {
      term = Integer.parseInt(termChoice.getSelectedItem());
    }

    // Draw the graph.

    drawGraph();
  }

  // Draw a graph that shows the result of compounding the investment.

  private void drawGraph() {

    // Pass the original amount and the compounded amount to the graph object.
    // It will use the values to draw a stacked bar graph.

    graph.setValues(amount, amount * Math.pow(1+rate,term));

    // Force the graph to be re-painted.

    graph.repaint();
  }
}

// This class subclasses Canvas to draw a stacked bar graph.

class Graph extends Canvas {

  // Instance variables for holding the height and value of the lower (first)
  // portion of the stacked bar.

  private int bar1Height;
  private double bar1Value;

  // Instance variable for holding the height of the upper (second) portion of
  // the stacked bar.

  private int bar2Height;

  // Instance variable for holding the total value of the two bars.

  private double totalValue;

  // This method constructs a graph object.

  public Graph() {

    // Set the graph size.

    setSize(220, 240);

    // Initialize the lower bar and total bar values to zero.

    bar1Value = 0;
    totalValue = 0;
  }

  // This method may be called to set the lower bar and total bar values. The
  // values are then used to calculate the relative bar heights.

  public void setValues(double value1, double value2) {

    // Store the lower bar and total bar values.

    bar1Value = value1;
    totalValue = value2;

    // Calculate the relative bar heights.

    bar1Height = (int) (200 * (bar1Value / totalValue));
    bar2Height = 200 - bar1Height;

    // Re-paint the graph.

    repaint();
  }

  // This method is automatically called whenever the graph needs to be
  // rendered. It receives a Graphics object (its context) as a parameter.

  public void paint(Graphics g) {

    // Determine the size of the graph and fill it with black.

    Dimension graphSize = this.getSize();
    g.setColor(Color.black);
    g.fillRect(0, 0, graphSize.width, graphSize.height);

    // If the lower bar value and total bar value are valid, draw the bars and
    // display their values.

    if (bar1Value != 0 && totalValue >= 0) {

      // Set the color of the top bar, draw it, and display its value in
      // currency format.

      g.setColor(Color.green);
      g.fillRect(80, 20, 40, bar2Height);
      g.drawString(Utility.moneyFormat(totalValue), 130, 20);

      // Set the color of the lower bar, draw it, and display its value in
      // currency format.

      g.setColor(Color.red);
      g.fillRect(80, 20 + bar2Height, 40, bar1Height);
      g.drawString(Utility.moneyFormat(bar1Value), 10, 20 + bar2Height);
    }

    // Otherwise, display a message.

    else {
      g.setColor(Color.red);
      g.drawString("Enter an amount greater than zero", 18, 125);
    }
  }
}