/**
 * StudentList.java
 * 
 * @author Mr J 
 * @version 20050209
 */
import java.applet.*;
import java.awt.*;   
import java.awt.event.*;

public class StudentList extends Applet implements ActionListener
{
   //  Using a defined StudentRecordNode class
 	private StudentRecordNode root; // first item in list;

	TextArea textWindow = new TextArea("This is where the outputs will appear\n", 20, 30);

	// fields and labels for data entry
	Label  nameLabel = new Label("Student name: ");
	Label tutorLabel = new Label("Tutor group: ");
	TextField  nameField = new TextField(30);
	TextField tutorField = new TextField( 3);	
 	// action buttons
	Button addButton  = new Button("Add");
	Button lstButton  = new Button("List");
    /**
     * This method sets uo the GUI objects 
     */
    public void init() 
    {	
	  addButton.addActionListener(this);
	  lstButton.addActionListener(this);
      // text objects	
	  add(nameLabel);  
	  add(nameField);
	  add(tutorLabel); 
	  add(tutorField);	

	  add(addButton);
	  add(lstButton);

	  add(textWindow);
  }
  /**
   * This method detects button events
   * 
   * @param ActionEvent - the action that triggered the call to this method
   */
  public void actionPerformed(ActionEvent e)
  {
	// React to the button presses

	if (e.getSource() == addButton)
	{
   	    addNode();
   	}
   	else
   	{
		displayList();
	}
  }
  /**
   * Adds a node to the head of the linked list
   */
  public void addNode() 
  {
    // create a new node using the constructor of Class StudentRecordNode
    // this node has its reference field pointed to root
	StudentRecordNode theNode = new StudentRecordNode( nameField.getText(),
	                                                   tutorField.getText(), 
	                                                   root                );
    // now we point the root pointer to this node 	
	root = theNode;
    // clear the fields of text for convenience
	nameField.setText("");
	tutorField.setText("");
	// put the cursor in the name field
	nameField.requestFocus();
  }
  /**
   * A method to display the linked list of nodes in the text area window
  */
  public void displayList() 
  {
    // a temporary pointer to hold the reference of each node of the list in turn
	StudentRecordNode temp;
	int numInList=1;
	// start at thr root
	temp = root;
	textWindow.append( "\n head of list \n ------------\n" );
	// "walk" down the list, using the temp pointer
	while (temp != null)
	{
		textWindow.append( "Number: " + numInList++     + "\n" );
		textWindow.append( "Name:   " + temp.getName()  + "\n" );
		textWindow.append( "Tutor:  " + temp.getTutor() + "\n" );
		textWindow.append( "\n--------------------\n" );
		temp = temp.getNext();
	}
  }
}