// This file contains excerpts from the textbook Concrete
// Abstractions: An Introduction to Computer Science Using Scheme, by
// Max Hailperin, Barbara Kaiser, and Karl Knight, Copyright (c) 1998
// by the authors. Full text is available for free at
// http://www.gustavus.edu/+max/concrete-abstractions.html

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

public class Compounder extends java.applet.Applet implements ItemListener {

  private TextArea outputArea;
  private CompoundingThread compThread;
  private Checkbox runCheckbox;

  public Compounder(){
    compThread = new CompoundingThread(this);
    
    setLayout(new BorderLayout());
    Panel controlPanel = new Panel();
    add("North", controlPanel);
    outputArea = new TextArea();
    outputArea.setEditable(false);
    add("Center", outputArea);

    controlPanel.add(new Label("Initial amount:", Label.RIGHT));
    controlPanel.add(new InitialAmountField(1000.00, compThread));
    controlPanel.add(new Label("Interest rate:", Label.RIGHT));
    controlPanel.add(new InterestRateField(.05, compThread));
    runCheckbox = new Checkbox("Run");
    runCheckbox.addItemListener(this);
    controlPanel.add(runCheckbox);

    compThread.start();
  }

  public void outputLine(String line){
    outputArea.append(line + "\n");
  }

  public void clearOutput(){
    outputArea.setText("");
  }

  public void stop(){
    compThread.disable();
  }

  public void start(){
    if(runCheckbox.getState()){
      compThread.enable();
    }
  }

  public void destroy(){
    compThread.stop();
  }

  public void itemStateChanged(ItemEvent evt){
    if(evt.getStateChange() == ItemEvent.SELECTED){
      compThread.enable();
    } else {
      compThread.disable();
    }
  }
}