import java.awt.*;
import java.util.*;
import java.applet.Applet;
import Queue.*;

public class QueueDemo extends Applet
{
  protected TextField input_field;

  protected Button enqueue_but;

  protected Button dequeue_but;

  protected TextArea status_area;

  protected Label output_label;

  protected Queue the_queue;

  public void init()
  {
    setLayout(new BorderLayout());
    add("North", this.input_field = new TextField("item1"));
    add("South", this.output_label = new Label(""));
    add("West", this.enqueue_but = new Button("Enqueue"));
    add("East", this.dequeue_but = new Button("Dequeue"));
    this.status_area = new TextArea(
      "Type in some text in the field above,\n" +
      "then press the 'Enqueue' button.\n" +
      "Enqueue some more different items,\n" +
      "then press the 'Dequeue' button to remove them.");
    this.status_area.setEditable(false);
    add("Center", this.status_area);
    this.the_queue = new QImpl();
  }

  public void refresh_queue_display()
  {
    String result_str = "";
    String item_str;

    Enumeration the_list = this.the_queue.elements();
    while (the_list.hasMoreElements())
    {
      item_str = (String) the_list.nextElement();
      result_str = result_str + item_str + "\n";
    }
    this.status_area.setText(result_str);
  }

  public void enqueue_pressed()
  {
    String input_str = this.input_field.getText();
    if (input_str.length() == 0)
    {
      this.output_label.setText("Please type in some text first.");
      this.input_field.setText("");
    }
    else
    {
      this.the_queue.insertFirst(input_str);
      this.output_label.setText(input_str + " enqueued.");
      this.input_field.setText("");
      this.refresh_queue_display();
    }
    this.repaint();
  }

  public void dequeue_pressed()
  {
    Object removed_item;

    try
    {
      removed_item = this.the_queue.removeLast();
    }
    catch (Exception e)
    {
      this.output_label.setText("Queue is empty.");
      return;
    }
    this.output_label.setText((String) removed_item + " dequeued.");
    this.refresh_queue_display();
    this.repaint();
  }

  public boolean action(Event event, Object arg)
  {
    if (event.target == enqueue_but)
    {
      this.enqueue_pressed();
      return true;
    }
    else if (event.target == dequeue_but)
    {
      this.dequeue_pressed();
      return true;
    }
    else
      return super.action(event, arg);
  }
}