import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
/**
 * This Applet demonstrates an inner class being used for data records
 * The inner class keeps data about video tapes
 *
 * @ Mr J
 * @ 20040308 
 */
public class VideoTapeInner extends Applet implements ActionListener
{
	// display fields for record data
	private TextField vtTitle = new TextField(25);
	private TextField vtLength = new TextField(6);
	private Checkbox vtLent = new Checkbox();
	private Choice vtType = new Choice();

	// labels for field data
	private Label fdTitle = new Label("Video title:", Label.RIGHT);
	private Label fdLength = new Label("Length (min):", Label.RIGHT);
	private Label fdLent = new Label("Lent:", Label.RIGHT);
	private Label fdType = new Label("Type:", Label.RIGHT);

	// control buttons
	private Button add = new Button("add tape");
	private Button next = new Button("next");
	private Button prev = new Button("previous");

	// system messages display
	private Label messages = new Label("System messages will appear here");

	// Set up an array to hold the tape collection
	private static final int MAX_TAPES = 5; 
	VideoTape[] collection = new VideoTape[MAX_TAPES];
	private int last = -1;         // pointer to last record in collection
	private int current = -1;      // pointer to record in display
	
	// define the possible movie types (could be more flexible):
	static final int ROMANCE = 0;
	static final int COMEDY = 1;
	static final int ACTION = 2;
	static final int[] TYPE = { ROMANCE, COMEDY, ACTION};
	static final String[] DESC = {"Romance", "Comedy", "Action"};
	static final char[] CODE = {'R', 'C', 'A'};
	// inner class definition
    class VideoTape
    {
      // data members
      private String title;
      private int length;
      private boolean lent;
      private char type;
      // Constructors
      public VideoTape() 
      { 
        super(); 
      }
      public VideoTape( String title, int length, boolean lent, char type ) 
      {
        setTitle( title );
        setLength( length );
        setLent( lent );
        setType( type );
      }
      // mutator methods
      public void setTitle( String title ) 
      { 
        this.title = title;
      }
      public void setLength( int length ) 
      { 
        this.length = length;
      }
      public void setLent( boolean lent ) 
      { 
        this.lent = lent; 
      }
      public void setType( char type ) 
      { 
        this.type = type; 
      }
      // accessor methods
      public String getTitle() { return this.title; }
      public int getLength() { return this.length; }
      public boolean isLent()  { return this.lent; }
      public char getType() { return this.type; }
    }; // end of inner class definition	
	/** 
	 * Add objects to the Applet
	 */
	public void init()
	{
	    Panel recordPanel = new Panel();
	    recordPanel.setLayout( new GridLayout(4, 2, 10, 10) );
        recordPanel.add(fdTitle);
        recordPanel.add(vtTitle);
        recordPanel.add(fdLength);
        recordPanel.add(vtLength);
        recordPanel.add(fdLent);
        recordPanel.add(vtLent);
        recordPanel.add(fdType);
        recordPanel.add(vtType);
        
        Panel buttonPanel = new Panel();
        buttonPanel.setLayout( new GridLayout(3, 1, 10, 10) );
        buttonPanel.add(add);
        buttonPanel.add(prev);
        buttonPanel.add(next);
        
        setLayout( new BorderLayout(25, 25) );
        setSize(400, 180);
        add(recordPanel, BorderLayout.CENTER);
        add(buttonPanel, BorderLayout.EAST);
        add(messages, BorderLayout.SOUTH);
        
        // Causes button presses to be detected
        add.addActionListener(this);
        prev.addActionListener(this);
        next.addActionListener(this);
        // set up the choice list
        setUpChoices();
	}
	/** 
	 * When an event occurs on an object with an ActionListener attached, this
	 * method is carried out.  
	 * 
	 * @param e carries details about the event that occurred
	 */
	public void actionPerformed(ActionEvent e)
	{
	  if (e.getSource() == add)
	  {
        // add a new video tape to the collection
        VideoTape theTape = getTapeDetails();
        if (theTape != null)
        {
          last = last + 1;
          if (last == MAX_TAPES)
          {
            messages.setText("No more space to store tapes");
          }
          else
          {
            collection[last] = theTape;
            current = last;
            messages.setText("tape added");
            clearDisplay();
          }
        }
        else
        {
          messages.setText("Invalid tape details");
        }
	  }
	  else if (e.getSource() == next)
	  {
        if (current < last)
        {
          current = current + 1;
          setDisplay(current);
          messages.setText("At tape " + (current + 1) + " of " + (last + 1));
        }
        else
        {
          messages.setText("At last record");
        }
	  }
	  else if (e.getSource() == prev)
	  {
        if (current > 0)
        {
          current = current - 1; 
          setDisplay(current);
          messages.setText("At tape " + (current + 1) + " of " + (last+1));
        }
        else
        {
          messages.setText("At first record");
        }
	  }
	}
	/**
	 * set up some types in the choice list
	 */
	private void setUpChoices()
	{
	  for (int i = 0; i < TYPE.length; i++)
	  {
	    vtType.addItem(DESC[i]);
      }
	}
	/** 
	 * collect tape details and create new tape
	 * 
	 * @return a VideoTape object - null if details are invalid
	 */
	private VideoTape getTapeDetails()
	{
	  try
	  {
	    String title = vtTitle.getText();
	    int length = Integer.parseInt(vtLength.getText());
	    boolean lent = vtLent.getState();
	    char type = vtType.getSelectedItem().charAt(0);
	  
	    if ( (title.length() == 0) || (length == 0) )
	    {
	      return null;
	    }
	    return new VideoTape(title, length, lent, type);	    
	  }
	  catch(Exception  e)
	  {
	    return null;
	  }	  
	}
	/** 
	 * display tape details
	 * 
	 * @param the current VideoTape object
	 */
	private void setDisplay(int current)
	{
	  vtTitle.setText(collection[current].getTitle());
	  vtLength.setText("" + collection[current].getLength());
	  vtLent.setState(collection[current].isLent());
	  vtType.select(getTypeDescription(collection[current].getType()));
	}
	/** 
	 * clear record display panel
	 */
	private void clearDisplay()
	{
	  vtTitle.setText("");
	  vtLength.setText("");
	  vtLent.setState(false);
	  vtType.select(0);
	}
	/** 
	 * Given a code, return the corresponding description
	 * 
	 * @param the code to look up
	 * @returns a String with the description 
	 */
	private String getTypeDescription(char code)
	{
	  int pos = 0;
	  boolean found = false;
	  while ( (pos < CODE.length) && !(found) )
	  {
	    found = (CODE[pos] == code);
	    pos = pos + 1;
	  }
	  if (!found)
	  {
	    return "none";
	  }
	  else
	  {
	    return DESC[pos-1];
	  }
	}
}