package horstmann.ch05_invoice;
import java.util.ArrayList;
import java.util.Iterator;

import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;

/**
   An invoice for a sale, consisting of line items.
 */
public class Invoice
{
	/**
      Constructs a blank invoice.
	 */
	public Invoice()
	{
		items = new ArrayList<LineItem>();
		listeners = new ArrayList<ChangeListener>();
	}

	/**
      Adds an item to the invoice.
      @param item the item to add
	 */
	public void addItem(LineItem item)
	{
		items.add(item);
		// Notify all observers of the change to the invoice
		ChangeEvent event = new ChangeEvent(this);
		for (ChangeListener listener : listeners)
			listener.stateChanged(event);
	}

	/**
      Adds a change listener to the invoice.
      @param listener the change listener to add
	 */
	public void addChangeListener(ChangeListener listener)
	{
		listeners.add(listener);
	}

	/**
      Gets an iterator that iterates through the items.
      @return an iterator for the items
	 */
	public Iterator<LineItem> getItems()
	{
		return new
				Iterator<LineItem>()
		{
			public boolean hasNext()
			{
				return current < items.size();
			}

			public LineItem next()
			{
				return items.get(current++);
			}

			public void remove()
			{
				throw new UnsupportedOperationException();
			}

			private int current = 0;
		};
	}

	public String format(InvoiceFormatter formatter)
	{
		String r = formatter.formatHeader();
		Iterator<LineItem>iter = getItems();
		while (iter.hasNext())
			r += formatter.formatLineItem(iter.next());
		return r + formatter.formatFooter();
	}

	private ArrayList<LineItem> items;
	private ArrayList<ChangeListener> listeners;
}