import java.awt.*;					// To use Abstract Windows Toolkit classes.
import java.awt.event.*;				// To use Abstract Windows Toolkit event handling.
import javax.swing.*;					// To use Java swing classes.
import java.util.*;					// For date processing.
import java.text.*;					// For currency formatting.

/**
 * This class defines an applet to determine if a library book is late, and
 * if so, calculate the late fee to be assessed.  Internationalization is 
 * used so the user can choose a currency.  For this applet it will be the 
 * US Dollar and the British Pound.
 * 
 * As of November 13, 2000 the current rate of exchange is:
 * .25 United States Dollar is equal to 0.1739 British Pound 
 * 
 * Written by: David Nelson
 */

public class Ch12Applet extends JApplet implements ActionListener, ItemListener
{	
	// Object references for user interface components having a broad scope in this applet.
	
	JLabel dueDateHdg;				// For due date heading.
	JTextField dueDate;				// For due date text field.
	ButtonGroup currencySelect;		        // For radio button group of currency.
	JRadioButton item1;				// For US Dollar item.
	JRadioButton item2;				// For British Pound item.
	JLabel lateFeeHdg;				// For late fee heading.
	JTextField lateFee;				// For late fee text field (non editable).
	
	// Constants for currency choices.
	
	public static final String ITEM1 = "US Dollar";
	public static final String ITEM2 = "British £";
	
	// All other variables
	
	public double newLateFee = .25;

	// Construct number and date "formatters" for the default locale (USA).
	
	NumberFormat localCurrency = NumberFormat.getCurrencyInstance(Locale.US);
	DateFormat localDate = DateFormat.getDateInstance(DateFormat.SHORT, Locale.US);
	
	/**
	 * This method is automatically called when the browser loads the web page
	 * that launches the applet.  Its purpose is to perform applet initalization.
	 */
	
	public void init()
	{
		// Specify the applet's layout and background color.
		
		getContentPane().setLayout(new FlowLayout());
		getContentPane().setBackground(Color.lightGray);
	}
	
	/**
	 * This method is automatically called after init() and every time the 
	 * web page is revisited (due to surfing).  It adds components to the 
	 * applet window in the desired sequence.
	 */
	
	public void start()
	{
		// Declare a main heading, set its font, color, alignment, and add it
		// to the applet window.
		
		JLabel mainHdg = new JLabel("Library of Sorts");
		mainHdg.setFont(new Font("Arial", Font.BOLD, 20));
		mainHdg.setForeground(Color.blue);
		mainHdg.setHorizontalAlignment(SwingConstants.CENTER);
		getContentPane().add(mainHdg);
			
		// Instantiate an object representing the current date and time.
		
		GregorianCalendar today = new GregorianCalendar();
		
		// Construct a text field for the user to enter the due date.
		
		JLabel dueDateHdg = new JLabel("Due Date:");
		getContentPane().add(dueDateHdg);
		dueDate = new JTextField(" ", 10);
		getContentPane().add(dueDate);
		dueDate.addActionListener(this);
		
		// Construct a label heading for the currency selection.
		// Create a button group for the user to select between either the
		// US Dollar or the British Pound as the currency.	
		// Add the items to the button group. 
		// Add the radio buttons to the applet window and register a listener.
		
		JLabel currencyHdg = new JLabel("Currency:");
		getContentPane().add(currencyHdg);
		currencySelect = new ButtonGroup();
		item1 = new JRadioButton(ITEM1, true);
		currencySelect.add(item1);
		item2 = new JRadioButton(ITEM2, false);
		currencySelect.add(item2);
		getContentPane().add(item1);
		item1.addItemListener(this);
		JLabel blank2 = new JLabel("           ");
		getContentPane().add(blank2);
		getContentPane().add(item2);
		item2.addItemListener(this);
		
		// Construct a label and text box in which the late fee will be displayed.
		// Set its color scheme, alignment, mark it as non-editable. Add it
		// to the applet window.
		
		JLabel lateFeeHdg = new JLabel("Amount Due:");
		getContentPane().add(lateFeeHdg);
		lateFee = new JTextField(" ", 10);
		lateFee.setBackground(Color.black);
		lateFee.setForeground(Color.green);
		lateFee.setHorizontalAlignment(SwingConstants.CENTER);
		lateFee.setEditable(false);
		getContentPane().add(lateFee);	
	}
	
	/**
	 * This method is automatically called when the user is about to surf to
	 * another web page or closes the browser.  Its purpose is to stop applet
	 * execution.  It resets the applet for a smooth restart.
	 */
	
	public void stop()
	{
		// Remove all components so they can be re-added on a restart.
		
		getContentPane().removeAll();
	}
	
	/**
	 * This method is automatically called after stop() when the browser is being
	 * closed.  Its purpose is to allow the applet to perform termination processing.
	 * 
	 * This applet doesn't require the method, but a shell is coded for documentation
	 * and maintenance purposes.
	 */
	
	public void destroy()
	{
	}
	
	/**
	 * This method implements the abstract method of the ActionListener interface.
	 * 
	 * In this applet, the only event to be handled is the user specifying a
	 * due date for the borrowed library book.
	 */
	
	public void actionPerformed(ActionEvent e)
	{
		// Call an internal method that will trigger the late fee calculation.
		
		CalculateLateFee();
	}
			
	/**
	 * This method implements the abstract method of the ItemListener interface.
	 * 
	 * In this applet, the user has selected a different currency from the radio
	 * button group.
	 */
	
	public void itemStateChanged(ItemEvent e)
	{		
		// If a currency select radio button was clicked, determine which 
		// item was selected.
		
		if (e.getSource() instanceof JRadioButton)
		{
			if (e.getItem().equals(item1))
			{
				// Set late fee to US currency of 25 cents
				
				newLateFee = .25;
				
				// United States Currency
				
				localCurrency = NumberFormat.getCurrencyInstance(Locale.US);
				
				// Recalculate the late fee
				
				CalculateLateFee();
			}
			else if (e.getItem().equals(item2))
			{			
				// Set late fee to British currency equivalent of US 25 cents
				
				newLateFee = .1739;
				
				// British Pound Currency
				
				localCurrency = NumberFormat.getCurrencyInstance(Locale.UK);
				
				// Recalculate the late fee
				
				CalculateLateFee();
			}
		}
	}
	
	/**
	 * This method calculates the late fee which is determined by two things.
	 * First, the due date field will trigger the action. 
	 * Second, the selected currency will determine what currency to display
	 * the late fee in.
	 */
	
	public void CalculateLateFee()
	{
		// Construct an object representing the current date.
		
		GregorianCalendar currentDate = new GregorianCalendar();
		
		// "try" the block which converts the string in the due date text field to a
		// GregorianCalendar object to prepare to compare it to the current date.
		
		try
		{
			DateFormat localDate = DateFormat.getDateInstance
				(DateFormat.SHORT,Locale.US);
			GregorianCalendar due = new GregorianCalendar();
			due.setTime(localDate.parse(dueDate.getText().trim()));
				
			// Compare the due date to the current date.
		
			if (due.before(currentDate))
			{
				// If the due date is before the current date calculate and display the
				// late fee.  The daily late fee is equivalent to 25 cents per day. So
				// we multiplay the 25 cents per day by the number of days between the
				// current date and the due date.
			
				int days = currentDate.get(Calendar.DAY_OF_YEAR) - due.get(Calendar.DAY_OF_YEAR);
				double amtDue = newLateFee * days;
						   
				// Set the amount due in the late fee text box 
				// (formatted by the appropiate locale).
			
				lateFee.setText(localCurrency.format(amtDue));
			}
			else
			{
				// If the due date is equal to or after the current date the late fee 
				// will be zero.  So set the days to zero to force a return value for
				// amount due to display "0.00" as the late fee.
				
				int days = 0;
				double amtDue = newLateFee * days;
				lateFee.setText(localCurrency.format(amtDue));
			}
		}
		
		// Otherwise...
		
		catch(Exception err)
		{
		}
	}
}