// Store data about the student and provide the student's interface to the
// system.
import java.util.*;

public abstract class Student {
    public Student() {}

    public Student (String aName, DirectorOfStudies aDos) {
        name = aName;
        director = aDos;
    }

// All students have to do 6 modules; subclasses may impose extra conditions.
    boolean validateChoices() {
       return (modules.size() == 6);
    }

    void registerForModule (Module m) {
       modules.add(m);
       m.registerStudent(this);
    }

    boolean deregisterFromModule (Module m) {
	m.deregisterStudent(this);
	return (modules.remove(m));
    }

    // really simple menu interface for now
    public void interact(java.io.BufferedReader d) 
	throws java.io.IOException {
	System.out.println (name + " is currently registered for:");
	Iterator i = modules.iterator();
	Module m;
	while (i.hasNext()) {
	    m = (Module)i.next();
	    System.out.println (m.name);
	}
	int entry = 0;
	String menu = "Enter:\n" +
	    "0 to register for a module;\n" +
	    "1 to deregister from a module;\n" +
	    "2 to check the acceptability of your current set of courses\n" +
	    "3 to quit:\n";
	while (entry != 3) {
	    System.out.print(menu);
	    entry = Integer.parseInt(d.readLine());
	    switch(entry) {
	    case 0:
		chooseModule(d);
		break;
	    case 1:
		unchooseModule(d);
		break;
	    case 2:
		if (validateChoices()) {
		    System.out.println("Valid");
		} else {
		    System.out.println("Invalid");
		}
		break;
	    case 3: 
		break;
	    default: 
		System.out.println("Unrecognised option.");
	    }
	}
    }

    public abstract void chooseModule(java.io.BufferedReader d) 
	throws java.io.IOException; 

    // Currently no warning if you deregister from something you're not
    // registered for in the first place -- silly?
    public void unchooseModule(java.io.BufferedReader d) 
	throws java.io.IOException {
	System.out.println("Deregister from which module?");
	Module m = Registry.getModule(d.readLine());
	if (null != m) {
	    if (!deregisterFromModule(m)) {
		System.out.println ("You weren't registered for that!");
	    }
	} else {
	    System.out.println ("Not a module!");
	}
    }

    public String name;
    protected HashSet modules = new HashSet();
    public DirectorOfStudies director;
}