package database;

import java.util.Collection;

/**
 * This class is derived from section 2.3.2.
 * 
 * CourseList is the repository of Course information.
 * @author kdavis22
 */
abstract class CourseList {

   /**
    * The collection of Courses.
    */
   Collection<Course> data; 

   /**
    * Add the given Course to the given CourseList. The courseNumber of the given Course
    * must not be the same as a Course already on the CourseList. The Course must have a 
    * CourseType, department, name, wtus and credits.
    */
    /*@
     ensures
       //
       // A Course is on the output CourseList if and only if it is the new Course
       // to be added or it is in the input CourseList.
       //
       (\forall Course courOther ;
           data.contains(courOther) <==>
               courOther.equals(cour) || \old(data).contains(courOther));
     @*/
   abstract void add(Course cour);

   /**
    * Remove the given Course from the given CourseList. The given Course must already be
    * on the CourseList. 
    */
   /*@
      requires
        //
        // The given Course is in the given CourseList.
        //
        data.contains(cour);

      ensures
        //
        // A Course is in the output CourseList if and only if it is not the existing
        // Course to be deleted and it is in the input CourseList.
        //
        (\forall Course courOther ;
            data.contains(courOther) <==>
                !courOther.equals(cour) && \old(data).contains(courOther));
     @*/
   abstract void remove(Course cour);
   
   /**
    * Change the old Course to the new Course. The old and new Courses must not be the 
    * same. The old Record must already be on the CourseList. The new Course must meet 
    * the same conditions as for the input to the AddCourse operation.
    */
   /*@
      requires
        //
        // The old and new Courses are not the same.
        //
        !oldCour.equals(newCour);

       ensures
         //
         // A Course is in the output CourseList if and only if it is the new Course
         // to be added or it is in the input CourseList, and it is not the old Course.
         //
         (\forall Course courOther ;
             data.contains(courOther) <==>
                courOther.equals(newCour) || 
                    \old(data).contains(courOther) &&
                        !courOther.equals(oldCour));
     @*/
   abstract void change(Course oldCour, Course newCour);
}