#lang racket

;; interfaces and constants needed by more than one class.

(provide SWorld<%> Widget<%> SWidget<%> SWidgetListener<%>
         SWidgetPublisher<%>)  
(provide CANVAS-WIDTH CANVAS-HEIGHT)

;; CONSTANTS needed by more than one class.

(define CANVAS-WIDTH 400)
(define CANVAS-HEIGHT 300)


;; INTERFACES

;; An SWorld is an object of any class that implements SWorld<%>

(define SWorld<%>
  (interface ()

    ; -> Void
    ; GIVEN: no arguments
    ; EFFECT: updates this world to its state after a tick
    after-tick          

    ; Integer Integer MouseEvent-> Void
    ; GIVEN: an (x,y) location
    ; EFFECT: updates this world to the state that should follow the
    ; given mouse event at the given location.
    after-mouse-event

    ; KeyEvent : KeyEvent -> Void
    ; GIVEN: a key event
    ; EFFECT: updates this world to the state that should follow the
    ; given key event
    after-key-event     

    ; -> Scene
    ; GIVEN: a scene
    ; RETURNS: a scene that depicts this World
    to-scene

   ; Widget -> Void
   ; GIVEN: A widget
   ; EFFECT: add the given widget to the world
   add-widget

   ; SWidget -> Void
   ; GIVEN: A stateful widget
   ; EFFECT: add the given widget to the world
   add-stateful-widget

    ))

;; A Widget is an object of any class that implements Widget<%>

(define Widget<%>
  (interface ()

    ; -> Widget
    ; GIVEN: no arguments
    ; RETURNS: the state of this object that should follow at time t+1.
    after-tick          

    ; Integer Integer -> Widget
    ; GIVEN: an (x,y) location
    ; RETURNS: the state of this object that should follow the
    ; specified mouse event at the given location.
    after-button-down
    after-button-up
    after-drag

    ; KeyEvent -> Widget
    ; GIVEN: a key event and a time
    ; RETURNS: the state of this object that should follow the
    ; given key event
    after-key-event     

    ; Scene -> Scene
    ; GIVEN: a scene
    ; RETURNS: a scene like the given one, but with this object
    ; painted on it.
    add-to-scene
    ))

;; An SWidget is an object of any class that implements the SWidget<%>
;; interface.

;; A SWidget is like a Widget, but it is stable (stateful).

(define SWidget<%>
  (interface ()

    ; -> Void
    ; GIVEN: no arguments
    ; EFFECT: updates this widget to the state it should have
    ; following a tick.
    after-tick          

    ; Integer Integer -> Void
    ; GIVEN: a location
    ; EFFECT: updates this widget to the state it should have
    ; following the specified mouse event at the given location.
    after-button-down
    after-button-up
    after-drag

    ; KeyEvent : KeyEvent -> Void
    ; GIVEN: a key event
    ; EFFECT: updates this widget to the state it should have
    ; following the given key event
    after-key-event     

    ; Scene -> Scene
    ; GIVEN: a scene
    ; RETURNS: a scene like the given one, but with this object
    ; painted on it.
    add-to-scene
    ))

;; while we're at it, we'll rename the interfaces to reflect their
;; generic nature.

;; Additional method for SBall% and other classes that receive messages
;; from the wall:

(define SWidgetListener<%>
  (interface (SWidget<%>)

    ; Int -> Void
    ; EFFECT: updates the ball's cached value of the wall's position
    update-wall-pos

    ))

;; Additional method for classes that send messages to
;; SWidgetListeners. In our example, SWall% is the only such class. 

(define SWidgetPublisher<%>
  (interface (SWidget<%>)

    ; SWidgetListener -> Int
    ; GIVEN: An SWidgetListener
    ; EFFECT: registers the listener to receive position updates from this wall.
    ; RETURNS: the current x-position of the wall
    register

    ))