import java.awt.*;
import java.applet.*;
import java.util.*;
import java.awt.event.*;
import java.io.*;
import java.net.*;

public class ADTLinkedListStudentDBTester extends Applet 
                           implements ItemListener,
				      ActionListener  { 

  LinkedList studentDB;

  TextArea result;
  TextField tfNumber;
  Choice fileURL;
  Label label1,label2;

  String datafile[] = {	"studfile1.html",
			"studfile2.html",
			"studfile3.html",
			"studfile4.html" };

  public void init() {


    result = new TextArea(12,80);
    label1 = new Label("Test Case");
    label2 = new Label("Remove Student");
    tfNumber = new TextField(10);
 

    fileURL = new Choice();

    for (int i = 0; i < datafile.length; i++)
	fileURL.add(datafile[i]);

    add(label1);
    add(fileURL);
    add(label2);
    add(tfNumber);
    add(result);
     
    fileURL.addItemListener(this);
    tfNumber.addActionListener(this);
  }

  public void itemStateChanged(ItemEvent ie) {

    studentDB = new LinkedList();

    try {
    	URL url = new URL("http://personal.cityu.edu.hk/~dcywchan/2003dco10103/" +
                           fileURL.getSelectedItem());
	URLConnection data = url.openConnection();
        BufferedReader inFile = new BufferedReader(new InputStreamReader(data.getInputStream()));

        String textLine;
  
        while((textLine = inFile.readLine()) != null) {

          StringTokenizer  st = new  StringTokenizer(textLine, "_");

	  StudentNode stdNode = new StudentNode(Integer.parseInt(st.nextToken()),
                                                st.nextToken(),
					        Integer.parseInt(st.nextToken()));

          if (studentDB.size() == 0)
             studentDB.addFirst(stdNode);          
          else if (! studentDB.contains(stdNode)) {

                  StudentNode p = (StudentNode) studentDB.getFirst();

                  while ((p != null) && (p.compareTo(stdNode) > 0)) 
                        p = p.getNext();

                  if (p == null) {
                        ((StudentNode) studentDB.getLast()).setNext(stdNode);
                        studentDB.addLast(stdNode);
                  } else if (p == (StudentNode) studentDB.getFirst()) {
                          stdNode.setNext(p);
                          studentDB.addFirst(stdNode);
                       } else {
                              StudentNode q = (StudentNode) studentDB.getFirst();
                              while (q.getNext() !=  p) q = q.getNext();

                              studentDB.add(studentDB.indexOf(p),stdNode);
			
                              q.setNext(stdNode);
                              stdNode.setNext(p);
                         }
                 }
         }

        result.setText(toString());
        inFile.close();
    } catch(MalformedURLException mue) {}
      catch(IOException ioe) {}
  }

  public void actionPerformed(ActionEvent e) {

     studentDB.remove(new StudentNode(Integer.parseInt(tfNumber.getText())));
     result.setText(toString());
  }

  public String  toString()  {

      String s = "";

      Iterator itr = studentDB.iterator();

      while (itr.hasNext())
        s += ((StudentNode) itr.next()).toString() + '\n';

      return  s; 
   }
}