/*
 *        Names: Sheila Marie George, Mang-Fai Ma, Jun Shen
 *               Yu Su, Xiyou Wang, John Woods,
 *               Nelson Zhan, Zhengrong Zuo
 *
 *       Course: IS 2470, Interactive System Design
 *
 *      Project: Course Scheduler (Group 2)
 *
 *          Due: June 18, 1998
 *
 */

/**
 * An applet includes 3 applets to help students/advisors in the
 * Department of Information Science choose courses. This applet
 * accesses course offerings, course descriptions, and course
 * requirement from school webpages and provide an interactive
 * planning aid for class scheduling.
 *
 * @version 1.0 18 June 1998
 */

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

// This is the main applet for Course Scheduler
public class CourseScheduler extends Applet
{
   // Use CardLayout to switch from one window to another
   CardLayout card_layout = new CardLayout();
   Applet a1 = new Window1();
   Applet a2 = new Window2();
   Applet a3 = new Window3();
   Panel windows = new Panel();
   
   public int[] selectedlist1;
   public int[] selectedlist2;
   public int[] vtorIndex = new int[50];
   public List courselist1;
   public List courselist2;
   public List crnlist;
   public List prereqlist1;
   public int validcoursecount;
   public Checkbox cb1, cb2, cb3, cb4;
   public Vector coursevtor = new Vector();
   
   // Initialization for CourseScheduler applet class
   public void init()
   {
      // Layout manager for CourseScheduler is BorderLayout
      setLayout(new BorderLayout());
      
      windows.setLayout(card_layout);
      // Display a message when data is loading from webpages
      MsgDialog d = new MsgDialog(getFrame());
      d.MsgDisplay(true, "Loading... Please wait...");
      a1.init();   // Initialize the first window
      a2.init();   // Initialize the second window
      a3.init();   // Initialize the third window
      windows.add("Window 1", a1);
      windows.add("Window 2", a2);
      windows.add("Window 3", a3);
      add("Center", windows);
      d.MsgDisplay(false, "");
   }

   // An inner class to define the structure of Course Information
   class CourseInfo {
      public String id;               // Course number
      public String instructor;       // Instructor
      public String title;            // Course title
      public String timecategory;     // Categorize the time
      public String begintime;        // Course begin time
      public String endtime;          // Course end time
      public String description;      // Description about the course
      public String crn;              // CRN of the course
      public String link;             // Link to department's webpage
      public String days;             // Days for the class
      public String place;            // Place for the class
      public String prerequirement;   // Prerequisite for the class
   }

   // An inner class to pop up a dialog window of error
   class ErrorDialog extends Dialog
   {
      private Frame thisFrame;
     
      public ErrorDialog(Frame f, String info)
      {
         super(f, "Course Scheduler", false);
        
         thisFrame = f;
        
         this.resize(300, 200);
        
         Panel info_panel = new Panel();
         Panel ok_panel = new Panel();
        
         info_panel.setLayout(new FlowLayout());
         info_panel.add(new Label(info, Label.CENTER));
         add("Center", info_panel);
        
         ok_panel.add(new Button("OK"));
         add("South", ok_panel);
        
         thisFrame.disable();
         this.pack();
         this.move(512, 384);
         this.show();
      }
     
      public boolean action(Event evt, Object arg)
      {
         if (evt.target instanceof Button)
         {
            thisFrame.enable();
            this.hide();
            this.dispose();
            return true;
         }
         return false;
      }
   }
  
   // An inner class for pop-up messages
   class MsgDialog extends Dialog
   {
      private Frame thisFrame;
     
      public MsgDialog(Frame f)
      {
         super(f, "Course Scheduler", false);
        
         thisFrame = f;
        
         this.resize(300, 200);
      }
        
      public void MsgDisplay(boolean on, String info)
      {
         if (on)
         {
            Panel info_panel = new Panel();
        
            info_panel.setLayout(new FlowLayout());
            info_panel.add(new Label(info, Label.CENTER));
            add("Center", info_panel);
           
            thisFrame.disable();
            this.pack();
            this.move(512, 384);
            this.show();
         }
         else
         {
            thisFrame.enable();
            this.hide();
            this.dispose();
         }
      }
   }
  
   // This method helps to get right frame to display dialog windows
   public Frame getFrame()
   {
      Component c = (Component)this;
      Frame theFrame = null;
      Component parent = (Component)this;
      while (parent != null)
      {
         if (parent instanceof Frame)
         {
            theFrame = (Frame)parent;
            break;
         }
         parent = parent.getParent();
      }
      return theFrame;
   }

   // An applet for the first window
   class Window1 extends Applet
   {
      Socket c;
      DataInputStream in;
      PrintStream out;
      
      public void init()
      { 
         try {
            // Create a socket to communicate with the course server
            c = new Socket(InetAddress.getLocalHost(), 7147);
//            c = new Socket("www2.sis.pitt.edu", 7147);
            in = new DataInputStream(c.getInputStream());
            out = new PrintStream(c.getOutputStream());

            // Layout manager for the first window is BorderLayout
            setLayout(new BorderLayout(20,0));
         
            Label l1 = new Label();
            l1.setText(" Please choose courses you have taken.");
            l1.setFont(new Font("TimesRoman", Font.BOLD, 14));
            add("North", l1);
         
            courselist1 = new List(30, true);
            courselist1.setFont(new Font("Courier", Font.PLAIN, 12));
            add("Center", courselist1);

            Panel p2 = new Panel();
            p2.setLayout(new GridLayout(16,1,3,2));
            for (int i = 0; i < 3; i++)
               p2.add(new Label());
            p2.setFont(new Font("TimesRoman", Font.BOLD, 14));
            Label l2 = new Label();
            l2.setText("Your available time");
            p2.add(l2);
            Label l3 = new Label();
            l3.setText("next term");
            p2.add(l3);
            p2.add(new Label());

            cb1 = new Checkbox();
            cb1.setLabel("Morning");
            cb1.setFont(new Font("TimesRoman", Font.PLAIN, 14));
            p2.add(cb1);
            cb2 = new Checkbox();
            cb2.setLabel("Afternoon");
            cb2.setFont(new Font("TimesRoman", Font.PLAIN, 14));
            p2.add(cb2);
            cb3 = new Checkbox();
            cb3.setLabel("Evening");
            cb3.setFont(new Font("TimesRoman", Font.PLAIN, 14));
            p2.add(cb3);
            cb4 = new Checkbox();
            cb4.setLabel("Weekend");
            cb4.setFont(new Font("TimesRoman", Font.PLAIN, 14));
            p2.add(cb4);
            for (int i = 0; i < 6; i++)
               p2.add(new Label());
            add("East", p2);
         
            Panel p3 = new Panel();
            p3.setLayout(new GridLayout(1, 14, 3, 3));
            for (int i = 0; i < 6; i++)
               p3.add(new Label());
            Button b1 = new Button();
            Button b2 = new Button();
            b2.setFont(new Font("TimesRoman", Font.BOLD, 16));
            b2.setLabel("Next >");
            p3.add(b2);
            for (int i = 0; i < 3; i++)
               p3.add(new Label());
            b1.setFont(new Font("TimesRoman", Font.BOLD, 16));
            b1.setLabel("Clear");
            p3.add(b1);
            for (int i = 0; i < 3; i++)
               p3.add(new Label());
            add("South", p3);

            // Extract course information from the course description
            // webpage of the department of Information Science
            InitCourse();         
         }
         catch(IOException e) 
         {
            System.out.println("Error" + e);
         }
      }

      // Detect the action from the user
      public boolean action(Event evt, Object arg)
      {
         if (arg instanceof String)
         {
            String s = (String) arg;

            if (arg.equals("Clear")) 
            {
            // Clear all information in this page
               cb1.setState(false);
               cb2.setState(false);
               cb3.setState(false);
               cb4.setState(false);
               selectedlist1 = courselist1.getSelectedIndexes();
               for (int i = 0; i < selectedlist1.length; i++)
                  courselist1.deselect(selectedlist1[i]);
            }
            else if (arg.equals("Next >")) 
            {
               // Check if the user choose as least one time constraint
               if (!(cb1.getState() || cb2.getState() 
                   || cb3.getState() || cb4.getState()))
               {
                  ErrorDialog ed = new ErrorDialog(getFrame(),
                           "Please select at least one time constraint");
               }
               else   
               {
                  // Jump to the second window
                  selectedlist1 = courselist1.getSelectedIndexes();
                  a2.start();
                  card_layout.show(windows, "Window 2");
               }
            }
            return super.action(evt, arg);
         }
         return true;
      }

      // Extract course information from department's webpage
      public void InitCourse() 
      {
         try 
         {
            // Send an URL string to course server
            out.println("http://www.sis.pitt.edu/~isdept/isgradcrs.html");
      
            String line,coursenumber,coursetitle;
            int i,j;
      
            // Analyze each line in the HTML file
            while (!(line = in.readLine()).equals("+++"))  
            {
               i = line.indexOf("INFSCI2",0);
               j = line.indexOf("INFSCI3",0);
               coursenumber="";
               coursetitle="";
               if (( i>-1)) 
               {
                  coursenumber=line.substring(i, i+10);
                  if (line.indexOf("/B",0)<0) 
                  {
                     coursetitle=line.substring(line.indexOf("/A")+3, 
                                                line.length());
                     line=in.readLine();
                     if (line.indexOf("/B",0)>-1) 
                     {
                        coursetitle = coursetitle + " " 
                                      + line.substring(0, 
                                           line.indexOf("/B",0)-1);
                     }
                     else 
                     {
                        coursetitle = coursetitle + " "
                                      + line.substring(0, line.length());
                     }
                  }
                  else 
                  {
                     coursetitle = line.substring(line.indexOf("/A")+3, 
                                    line.indexOf("/B",0)-1);
                  } 

                  if (coursetitle.indexOf("INFSCI 2",0)>-1) 
                  {
                     coursetitle = 
                        coursetitle.substring(
                           coursetitle.indexOf("INFSCI 2",0), 
                           coursetitle.indexOf("INFSCI 2",0)+6)
                        + coursetitle.substring(
                           coursetitle.indexOf("INFSCI 2",0)+7, 
                           coursetitle.length());
                  }
                  else 
                  {
                     coursetitle=coursenumber+" "+coursetitle;
                  }
                  courselist1.addItem(coursetitle);
               }
               if( j>-1) 
               {
                  coursenumber=line.substring(j, j+10);
                  if (line.indexOf("/B",0)<0) 
                  {
                     coursetitle = line.substring(line.indexOf("/A")+3, 
                                   line.length());
                     line = in.readLine();
                     if (line.indexOf("/B",0)>-1) 
                     {
                        coursetitle = coursetitle + " "
                           + line.substring(0, line.indexOf("/B",0)-1);
                     }
                     else 
                     {
                        coursetitle = coursetitle + " "
                           + line.substring(0, line.length());
                     }
                  }
                  else 
                  {
                     coursetitle = line.substring(line.indexOf("/A")+3, 
                        line.indexOf("/B",0)-1);
                  } 

                  if (coursetitle.indexOf("INFSCI 3",0)>-1) 
                  {
                     coursetitle = 
                        coursetitle.substring(
                           coursetitle.indexOf("INFSCI 3",0), 
                           coursetitle.indexOf("INFSCI 3",0)+6)
                        + coursetitle.substring(
                           coursetitle.indexOf("INFSCI 3",0)+7, 
                           coursetitle.length());
                  }
                  else 
                  {
                     coursetitle=coursenumber+" "+coursetitle;
                  }
                  if (coursetitle.indexOf("3951",0)==-1) 
                     courselist1.addItem(coursetitle);
               }
            } 
         }
         catch(IOException e)    
         {
            System.out.println("Error: " + e.getMessage());
         }
      }
   }

   // An applet for the second window
   class Window2 extends Applet
   {
      Socket c;
      DataInputStream in;
      PrintStream out;
   
      // Initialization for the second window
      public void init()
      { 
         try 
         {
            // Create a socket to the course server
            c = new Socket(InetAddress.getLocalHost(), 7147);
//            c = new Socket("www2.sis.pitt.edu", 7147);
            in = new DataInputStream(c.getInputStream());
            out = new PrintStream(c.getOutputStream());

            // Use BorderLayout as layout manager for the second window
            setLayout(new BorderLayout());
          
            Panel p1 = new Panel();
            p1.setLayout(new GridLayout(2,1));
            Label l1 = new Label();
            l1.setText(" Please select courses you wish to take next term.");
            l1.setFont(new Font("TimesRoman", Font.BOLD, 14));
            p1.add(l1);
            Label l2 = new Label();
            l2.setText(" Note: this list does not include"
                       + " the courses you've already taken.");
            l2.setFont(new Font("TimesRoman", Font.BOLD, 14));
            p1.add(l2);
            add("North", p1);
         
            courselist2 = new List(30, true);
            courselist2.setFont(new Font("Courier", Font.PLAIN, 12));
            add("Center", courselist2);

            Panel p2 = new Panel();
            p2.setLayout(new GridLayout(1, 14, 3, 3));
            for (int i = 0; i < 5; i++)
               p2.add(new Label());
            Button b1 = new Button();
            b1.setFont(new Font("TimesRoman", Font.BOLD, 16));
            b1.setLabel("< Back");
            p2.add(b1);
            Button b3 = new Button();
            b3.setFont(new Font("TimesRoman", Font.BOLD, 16));
            b3.setLabel("Next >");
            p2.add(b3);
            for (int i = 0; i < 3; i++)
               p2.add(new Label());
            Button b2 = new Button();
            b2.setFont(new Font("TimesRoman", Font.BOLD, 16));
            b2.setLabel("Clear");
            p2.add(b2);
            for (int i = 0; i < 3; i++)
               p2.add(new Label());
            add("South", p2);

            crnlist = new List();      // List for CRN numbers
            prereqlist1 = new List();  // List for prerequisite
            // Extract class schedule from University of Pittsbrugh's
            //   class schedule webpage
            InitCourse();              
         }
         catch(IOException e) 
         {
            System.out.println("Error" + e);
         }
      }

      // This start method is called by the first and third windows
      public void start()
      {
         ListCourse();
      }
   
      // Detect the action from the user
      public boolean action(Event evt, Object arg)
      {
         if (arg instanceof String)
         {
            String s = (String) arg;

            if (arg.equals("< Back")) 
            {
               // Go back to the previous page
               card_layout.show(windows, "Window 1");
            }
            else if (arg.equals("Clear")) 
            {
               // Reset all information in this page
               selectedlist2 = courselist2.getSelectedIndexes();
               for (int i = 0; i < selectedlist2.length; i++)
                  courselist2.deselect(selectedlist2[i]);
            }
            else if (arg.equals("Next >")) 
            {
               selectedlist2 = courselist2.getSelectedIndexes();
               if (selectedlist2.length == 0)
               {
                  // Ask the user to choose at least one course 
                  //   from this window. Otherwise, there is no
                  //   reason to do any analysis or schedule course
                  ErrorDialog ed = new ErrorDialog(getFrame(),
                            "Please select at least one course");
               }
               else
               {
                  // Display a message to ask the user to wait
                  //   before the third window is displayed
                  MsgDialog d = new MsgDialog(getFrame());
                  d.MsgDisplay(true, "Analyzing... Please wait...");
                  getPrereq();
                  a3.start();
                  d.MsgDisplay(false, "");
                  card_layout.show(windows, "Window 3");
                  if (validcoursecount > 5)
                  {
                     ErrorDialog ed = new ErrorDialog(getFrame(), 
                        "Warning: You have chosen more than 5 courses");
                  }
               }
            }
            return super.action(evt, arg);
         }
         return true;
      }

      // This method is to list all courses that satisfied the time
      //   constraint from the first window. This list also does not
      //   include any courses the student have already been taken.
      public void ListCourse()
      {
         courselist2.clear();
         String time = "";
         CourseInfo ci = new CourseInfo();
         Vector cid = new Vector();
         boolean addcourse;
         int i, j, k;
      
         k = 0;

         if (cb1.getState()) 
            time = time + "A";
         if (cb2.getState()) 
            time = time + "P";
         if (cb3.getState()) 
            time = time + "E";
         if (cb4.getState()) 
            time = time + "W";
            
      // List all the courses the student can take.
         for (i = 0; i < coursevtor.size(); i++) 
         {
            addcourse = true;
            ci = (CourseInfo) coursevtor.elementAt(i);
            for (j = 0; j < selectedlist1.length; j++)
            {
               if (courselist1.getItem(
                      selectedlist1[j]).substring(6, 10).equals(ci.id))
                  addcourse = false;
            }

            if ((!ci.timecategory.equals("BY APP")) 
                && (time.indexOf(ci.timecategory) == -1))
               addcourse = false;
            
            if (addcourse)
            {
               vtorIndex[k] = i;
               k++;
               crnlist.addItem(ci.crn);
               courselist2.addItem("INFSCI "
                           + ci.id + "  "
                           + ci.title + "  "
                           + ci.days + "  "
                           + ci.begintime + "  "
                           + ci.endtime + "  "
                           + ci.place + "  "
                           + ci.instructor);
            }
         }
      }
    
      // This method is to get the prerequisite of each courses that
      //   the user can take in next term. This information is taken
      //   from the department's fall term courses webpage
      public void getPrereq()
      {
         prereqlist1.clear();
         try
         {
            // Send an URL string to the course server
            out.println("http://www2.sis.pitt.edu/courses/distfall98.html");
            String line, prerequisite;
         
            for (int i = 0; i < selectedlist2.length; i++)
            {
               String courseNum = 
                  courselist2.getItem(selectedlist2[i]).substring(7, 11) 
                     + ":";
               // Search for the course number from the HTML file
               while ((line = in.readLine()).indexOf(courseNum) == -1) ;
               
               if (courseNum.equals("2905:"))
                  prereqlist1.addItem("2905 None");
               else
               {
                  // Search for the string "Pre//Co:"
                  while ((line = in.readLine()).indexOf("Pre//Co:") == -1) ;
                  prerequisite = line;
                  // Extract the prerequisite information
                  while (line.indexOf("") == -1)
                  {
                     line = in.readLine();
                     prerequisite = prerequisite + " " + line;
                  }
                  if (courseNum.equals("2540:"))
                     prereqlist1.addItem(courseNum.substring(0, 4) 
                     + prerequisite.substring(
                          prerequisite.indexOf("Pre//Co:")+9, 
                          prerequisite.indexOf("
")));
                  else  
                     prereqlist1.addItem(courseNum.substring(0, 4) 
                     + prerequisite.substring(
                          prerequisite.indexOf("Pre//Co:")+8, 
                          prerequisite.indexOf("")));
               }
            }
            while (!(line = in.readLine()).equals("+++")) ;
      
         }
         catch(IOException e)
         {
            System.out.println("Error: " + e.getMessage());
         }
      }
    
      // This method is to extract class schedule information from
      //   University of Pittsburgh's class schedule webpage
      public void InitCourse()
      {
         try 
         {
            // Send an URL string to the course server
            out.println("http://www.pitt.edu/~srfsweb/tsch_fal/ts76.htm#infsci");
      
            boolean hasInfo = false;
            String line;

            while (!(line = in.readLine()).equals("+++"))
            {
               // Search for the Graduate course offerings
               if (line.indexOf(">GRADUATE COURSE OFFERINGS") != -1)
               {
                  hasInfo = true;
                  break;
               }
            }

            if (!hasInfo)
            {
               System.out.println("There is not infomation available.\n");
            }
            else 
            {
               while (!(line = in.readLine()).equals("+++"))
               {
                  CourseInfo courseinfo = new CourseInfo();
                  // Search for the string "INFSCI"
                  if (line.indexOf("INFSCI") == -1)
                     continue;
                  else 
                  {
                     // Extract information from the HTML file and
                     //   do the necessary analysis on each line
                     courseinfo.id = line.substring(36, 40);
                     courseinfo.title = line.substring(40, 72);
                     line = in.readLine();
                     courseinfo.crn = line.substring(4,9);
                     courseinfo.days = line.substring(10, 16);

                     if(courseinfo.days.indexOf("BY APP") == -1)
                     {
                        courseinfo.begintime = line.substring(18, 24);
                        courseinfo.endtime = line.substring(25, 31);
                     }
                     else 
                     {
                        courseinfo.begintime = "      ";
                        courseinfo.endtime="      ";
                     }
                     String timecat = courseinfo.begintime.substring(5,6);
                     if (courseinfo.begintime.equals("      "))
                        courseinfo.timecategory = "BY APP";
                     else
                     {
                     int hour = 
                   Character.digit(line.substring(19, 20).charAt(0), 10); 
                     if (courseinfo.days.charAt(5) == 'S')
                        courseinfo.timecategory = "W";
                     else if (timecat.equals("A"))
                        courseinfo.timecategory = "A";
                     else if (timecat.equals("P") && (hour > 4))
                        courseinfo.timecategory = "E";
                     else
                        courseinfo.timecategory = "P";
                     }                  
                     courseinfo.place = line.substring(32, 41);
                     courseinfo.instructor = line.substring(62, 92);                 
                     coursevtor.addElement(courseinfo);                  
                  }
               }
            }
         }      
         catch(IOException e)
         {
            System.out.println("Error: " + e.getMessage());
         }     
      }
   }

   // An applet for the third window
   class Window3 extends Applet 
   {
      TextArea messagebox, validclasses;

      private int messageIndex;
      private int el, mff, csci, csys, st;
      private boolean[] validlist;      
   
      public void init() 
      {  
         // The layout for this window is a BorderLayout
         setLayout(new BorderLayout());

         Panel p = new Panel();
         p.setLayout(new GridLayout(2,1));

         Panel p0 = new Panel();       
         p0.setLayout(new BorderLayout());
         Label l1 = new Label();
         l1.setText("The Valid Selections Are:");
         l1.setFont(new Font("TimesRoman", Font.BOLD, 14));
         p0.add("North", l1);
         validclasses = new TextArea(15,40);
         validclasses.setEditable(false);
         validclasses.setFont(new Font("Courier", Font.PLAIN, 12));
         p0.add("Center", validclasses);
         p.add(p0);
      
         Panel p1 = new Panel();
         p1.setLayout(new BorderLayout());
         Label l2 = new Label();
         l2.setText("Messages:");
         l2.setFont(new Font("TimesRoman", Font.BOLD, 14));    
         p1.add("North", l2);     
         messagebox = new TextArea(15,40);
         messagebox.setEditable(false);
         messagebox.setFont(new Font("Courier", Font.PLAIN, 12));
         p1.add("Center", messagebox);   
         p.add(p1);
      
         add("Center", p);

         Panel p2 = new Panel();
         p2.setLayout(new GridLayout(1, 14, 3, 3));
         for (int i = 0; i < 5; i++)
            p2.add(new Label());
         Button b1 = new Button();
         b1.setFont(new Font("TimesRoman", Font.BOLD, 16));
         b1.setLabel("< Back");
         p2.add(b1);
         for (int i = 0; i < 3; i++)
            p2.add(new Label());
         Button b2 = new Button();
         b2.setFont(new Font("TimesRoman", Font.BOLD, 16));
         b2.setLabel("Restart");
         p2.add(b2);
         for (int i = 0; i < 4; i++)
            p2.add(new Label());
         add("South", p2);
      }
      
      // Detect the action from the user
      public boolean action(Event evt, Object arg) 
      {
         if (arg instanceof String) 
         {
            String s = (String) arg;
            if (arg.equals("< Back")) 
            {
               // Go back to the previous page
               card_layout.show(windows, "Window 2");
            }
            else if (arg.equals("Restart")) 
            {
               // Go to the first page and restart again
               cb1.setState(false);
               cb2.setState(false);
               cb3.setState(false);
               cb4.setState(false);
               for (int i = 0; i < selectedlist1.length; i++)
                  courselist1.deselect(selectedlist1[i]);
               card_layout.show(windows, "Window 1");
            }
            return super.action(evt, arg);
         }
         return true;
      } 
   
      // This method is called from the second window
      public void start() 
      {
         validlist = new boolean[selectedlist2.length];
         for (int i = 0; i < selectedlist2.length; i++)
            validlist[i] = true;
         messageIndex = 1;
         el = mff = csci = csys = st = 0;
         validclasses.setText("    CRN  " + "   Course    " 
                   + "             Title                "
                   + " Day    " + "B.Time  " + "E.Time  " + "  Place    "
                   + "          Instructor          "
                   + "\n");
         messagebox.setText("");
         CompareTime();
         IsPreRequisiteTaken();
         DisplayResults();
         StudyPlan();
      }
   
      // Compare two courses if they have time conflict
      public void CompareTime() 
      {  
         for (int i = 0; i < (selectedlist2.length - 1); i++) 
         {
            String icoursedays = 
               courselist2.getItem(selectedlist2[i]).substring(47, 53);
            if (!(icoursedays.equals("BY APP")))
            {
               String icoursebegintime = 
                  courselist2.getItem(selectedlist2[i]).substring(55, 61);
               String icourseendtime = 
                  courselist2.getItem(selectedlist2[i]).substring(63, 69);

               for (int j = i + 1; j < selectedlist2.length; j++) 
               {  
                  String jcoursedays = 
                     courselist2.getItem(selectedlist2[j]).substring(47, 53);
                  if (!(jcoursedays.equals("BY APP")))
                  {
                     String jcoursebegintime =
                        courselist2.getItem(
                           selectedlist2[j]).substring(55, 61);
                     String jcourseendtime =
                        courselist2.getItem(
                           selectedlist2[j]).substring(63, 69);
                     // if two classes are on the same day, check their time
                     if (SameDate(icoursedays, jcoursedays))
                     {
                        if (icoursebegintime.equals(jcoursebegintime)
                           || icourseendtime.equals(jcourseendtime)
                           || (TimeLessThan(icoursebegintime,
                                            jcoursebegintime)
                              && TimeLessThan(jcoursebegintime, 
                                              icourseendtime))
                           || (TimeLessThan(jcoursebegintime, 
                                            icoursebegintime)
                              && TimeLessThan(icoursebegintime, 
                                              jcourseendtime))) 
                        { 
                           DisplayMessage(
                              courselist2.getItem(
                                 selectedlist2[i]).substring(0, 11),
                              courselist2.getItem(
                                 selectedlist2[j]).substring(0, 11),
                              1, "");
                           validlist[i] = false;
                           validlist[j] = false;
                        }
                     }
                  }
               }
            }
         }
      }

      // Return true if the 2 course strings have days in common
      public boolean SameDate(String A, String B) 
      {
         for (int i = 0; i < 6; i++)
         {
            if ((A.charAt(i) != ' ') && 
                (A.charAt(i) == B.charAt(i)))
               return true;
         }
         return false;     
      }

      // Return true if time s is less than time t
      public boolean TimeLessThan(String s, String t) 
      {
         // Time is in the format: hh:mmA/P where hh <= 12

         char chs = s.charAt(5);
         char cht = t.charAt(5);

         if (chs == 'A' && cht == 'P') 
            return true;
         else if (chs == 'P' && cht == 'A') 
            return false;
   
         // Change the hours before comparing them
         int shour = Character.digit(s.charAt(0), 10) * 10 
                     + Character.digit(s.charAt(1), 10);
         if ((chs == 'P') && (shour != 12))
            shour += 12;
         int thour = Character.digit(t.charAt(0), 10) * 10 
                     + Character.digit(t.charAt(1), 10);
         if ((cht == 'P') && (thour != 12))
            thour += 12;

         if (shour < thour) 
            return true;
         else if (shour > thour) 
            return false;
         else if (s.substring(3,5).compareTo(t.substring(3,5)) <= 0) 
            return true;
         else 
            return false;
      }

      // A method to display a message in the message box
      public void DisplayMessage(String courseA, String courseB, 
                                 int k, String m) 
      {
         String message = null;
         if (k == 1) // Time conflict
         { 
            message = messageIndex + ". Course " + courseA 
                      + " and course " + courseB 
                      + " have a time conflict\n";
         }       
         else if (k == 2) // Additional requirement
         {
            message = messageIndex + ". Course " + courseA 
                      + " has additional requirement\n" 
                      + "    Pre//Co: " + m + "\n";
         }
         else if (k == 3) // Prerequisite conflict
         {
            message = messageIndex + ". Course " + courseA
                      + "'s pre-requisite has not been taken\n"
                      + "    Pre//Co: " + m + "\n";
         }
         messagebox.appendText(message);
         messageIndex++;
      } 

      // A method to check if the course's prerequisite was taken
      public void IsPreRequisiteTaken()
      {
         for (int i = 0; i < validlist.length; i++)
         {
            if (validlist[i])
            {
               String iprerequisite = prereqlist1.getItem(i);
               int n = iprerequisite.indexOf("INFSCI");

               if (n == -1)
               {
                  if (!(iprerequisite.substring(5, 9).equals("None")))
                     DisplayMessage(iprerequisite.substring(0, 4), "",
                                    2, iprerequisite.substring(5));
               }
               else
               {
                  n += 7;
                  String precourse1 = iprerequisite.substring(n, n+4);
                  if (iprerequisite.length() == (n+4))
                  {
                     if (!TakenBefore(precourse1))
                     {
                        DisplayMessage(iprerequisite.substring(0, 4), "", 
                                       3, iprerequisite.substring(5));
                        validlist[i] = false;
                     }
                  }
                  else
                  {
                     char ch1 = iprerequisite.charAt(n+4);
                     if (ch1 == '/')
                     {
                        String precourse2 = 
                                  iprerequisite.substring(n+5, n+9);
                        if (!(TakenBefore(precourse1) 
                      || TakenBefore(precourse2)))
                        {
                           DisplayMessage(iprerequisite.substring(0, 4), "", 
                                          3, iprerequisite.substring(5));
                           validlist[i] = false;
                        }
                     }
                     else
                     {
                        if (!TakenBefore(precourse1))
                        {
                           DisplayMessage(iprerequisite.substring(0, 4), "", 
                                          3, iprerequisite.substring(5));
                           validlist[i] = false;
                        }
                     }
                
                     if (validlist[i])
                     {
                        if (ch1 == ',')
                        {
                           char ch2 = iprerequisite.charAt(n+6);
                           if (Character.isDigit(ch2))
                           {
                              String precourse2 = 
                                 iprerequisite.substring(n+6, n+10);
                              if (!TakenBefore(precourse2))
                              {
                                 DisplayMessage(iprerequisite.substring(0, 4), 
                                     "", 3, iprerequisite.substring(5));
                                 validlist[i] = false;
                              }
                           }
                           else
                           {
                              if (iprerequisite.lastIndexOf("INFSCI") > n)
                              {
                                 String precourse2 = 
                                       iprerequisite.substring(
                                       iprerequisite.lastIndexOf("INFSCI")+7,
                                       iprerequisite.lastIndexOf("INFSCI")+11);
                                 if (!TakenBefore(precourse2))
                                 {
                                    DisplayMessage(
                                       iprerequisite.substring(0, 4), 
                                       "", 3, iprerequisite.substring(5));
                                    validlist[i] = false;
                                 }
                              }
                              else
                              {
                                 DisplayMessage(iprerequisite.substring(0, 4), 
                                    "", 2, iprerequisite.substring(5));
                              }
                           }
                        }
                        else
                        {
                           if (iprerequisite.lastIndexOf("INFSCI") > n)
                           {
                              String precourse2 = 
                                 iprerequisite.substring(
                                    iprerequisite.lastIndexOf("INFSCI")+7,
                                    iprerequisite.lastIndexOf("INFSCI")+11);
                              if (!TakenBefore(precourse2))
                              {
                                 DisplayMessage(iprerequisite.substring(0, 4), 
                                    "", 3, iprerequisite.substring(5));
                                 validlist[i] = false;
                              }
                           }
                           else
                           {
                              DisplayMessage(iprerequisite.substring(0, 4), 
                                 "", 2, iprerequisite.substring(5));
                           }
                        }
                     }
                  }
               }
            }
         }
      }

      // A method to check if the course was taken by using 
      //   the information obtained from the first window
      public boolean TakenBefore(String course)
      {
         for (int i = 0; i < selectedlist1.length; i++)
         {
            if (courselist1.getItem(
                   selectedlist1[i]).substring(6, 10).equals(course))
               return true;
         }
         return false;
      }
                  
      // A method to display the valid courses for the student
      public void DisplayResults() 
      {
         validcoursecount = 0;
         for (int i = 0; i < validlist.length; i++) 
         {
            if (validlist[i]) 
            { 
               validcoursecount++;
               String message = validcoursecount + ". " 
                      + crnlist.getItem(selectedlist2[i])
                      + " "
                      + courselist2.getItem(selectedlist2[i]) 
                      + "\n"; 
               validclasses.appendText(message);
            }   
         }
      }
      
      // A method to calculate total number of courses taken
      //   in each study area
      public void StudyPlan()
      {
         int i;
         String message;
         for (i = 0; i < selectedlist1.length; i++)
            CheckCourseCategory(courselist1.getItem(
                  selectedlist1[i]).substring(6, 10));
         for (i = 0; i < validlist.length; i++)
            if (validlist[i])
               CheckCourseCategory(courselist2.getItem(
                     selectedlist2[i]).substring(7, 11));
         message = messageIndex 
            + ". Including the above courses, you have:\n"
            + "     " + mff 
            + " Mathematical and Formal Foundations courses\n"
            + "     " + csci
            + " Cognitive Science courses\n"
            + "     " + csys
            + " Cognitive Systems courses\n"
            + "     " + st
            + " Systems and Technology courses\n"
            + "     " + el
            + " Electives\n";
         messagebox.appendText(message);
         messageIndex++;
      }

      // A method to categorize the course
      public void CheckCourseCategory(String course)
      {
         String courseprefix = course.substring(0, 2);

         if (course.equals("2600") || course.equals("2901") 
             || course.equals("2940") || course.equals("2950"))
            el++;
         else if (courseprefix.equals("20") || courseprefix.equals("21")
             || course.equals("2921") || course.equals("2931"))
            mff++;
         else if (courseprefix.equals("23")
             || course.equals("2923") || course.equals("2933"))
            csci++;
         else if (courseprefix.equals("24")
             || course.equals("2924") || course.equals("2934"))
            csys++;
         else if (courseprefix.equals("25") || courseprefix.equals("26")
             || courseprefix.equals("27") || courseprefix.equals("28")
             || course.equals("2925") || course.equals("2935")
             || course.equals("2926") || course.equals("2936")
             || course.equals("2927") || course.equals("2937")
             || course.equals("2928") || course.equals("2938"))
            st++;
      }   
   }
}