package presentation;

import java.util.Collection;
import java.util.List;
import format.*;

/**
 * A Slide is the unit of the presentation that is displayed on screen.
 * A Slide is displayed in a fixed-aspect-ratio viewport, and the
 * presentation building procedures, for the most part, limit the content
 * on a slide to what will fit in the viewport. However, topics
 * that are expandable or have extended associated content may cause a
 * scrollbar to appear.
 * <p>
 * A Slide contains one or more topics, whose name and any associated
 * content are displayed on the slide.
 */
public abstract class Slide {
    /** Topics displayed on the slide. */
    List<Topic> topics;

    /** Whether drawing tools can currently be used on the slide. */
    boolean drawable;

   /**
    * Expands the current topic in the slide.
    */
   /*@
     requires
      //
      //The topic is expandable
      //
         (topic.expandable == true)
         &&
      //
      //The topic is currently collapsed
      //
         (topic.expandedInSlide == false);


      ensures
      //
      //If the topic is expandable and not already expanded, it gets expanded in the slide
      //
         (topic.expandedInSlide)
         &&
      //
      // The slide cannot be drawn on while the topic is expanded
      //
         (!drawable);
   */
   abstract void expandTopic(Topic topic);

   /**
    * Collapses the current topic in the slide.
    */
   /*@
     requires
      //
      //The topic is expandable
      //
         (topic.expandable == true)
         &&
      //
      //The topic is already expanded
      //
         (topic.expandedInSlide);

      ensures
      //
      //If the topic is expandable and already expanded, it gets collapsed in the slide
      //
         (topic.expandedInSlide == false)
         &&
      //
      //If no other topics are expanded, the slide can be drawn on
      //
      (drawable <==> (\forall Topic t; topics.contains(t); !t.expandedInSlide)) ;
   */
   abstract void collapseTopic(Topic topic);
}