package Info;
import java.util.Collection;

/** Represents a group of classes, representing the top level of a users gradebook. */
public abstract class ClassGroup {
	/**
	 * The collection of user classes.
	 */
	public Collection<UserClass> classes;

	/**
	 * The user of this class group.
	 */
	public User user;

	/**
	 * Add the given UserClass to the given ClassGroup. The class name
	 * must not be the same as a UserClass already in the ClassGroup.
	 */
	/*@
	  requires
	     //
	     // There is no user class in the input ClassGroup
	     // with the same class name as the user class to be added.
	     //
	     (! (\exists UserClass aClass ;
	     	classes.contains(aClass) ;
			aClass.basicInfo.className.equals(newClass.basicInfo.className)));

	  ensures
	    //
	    // If preconditions are met, a user class is in the output classes if and only
	    // if it is the new class to be added or it is in the input classes.
	    //
	    (\forall UserClass aClass ;
            (classes.contains(aClass)) <==>
                aClass.equals(newClass) || \old(classes).contains(aClass));
	@*/
	public abstract void addClass(UserClass newClass);

	/**
	 * Deletes the given UserClass from the given ClassGroup.
	 */
	/*@
	  requires
	     //
	     // The passed user class to be deleted is a user class in the input ClassGroup.
	     //
	     ((\exists UserClass aClass ;
	     	classes.contains(aClass) ;
			aClass.equals(toRemove)));

	  ensures
	    //
	    // If preconditions are met, a user class is in the output classes if and only
	    // if it is not the existing class to be deleted or it is in the input classes.
	    //
	    (\forall UserClass aClass ;
            (classes.contains(aClass)) <==>
                !aClass.equals(toRemove) && \old(classes).contains(aClass));
	@*/
	public abstract void deleteClass(UserClass toRemove);
   }