#|
Bug:  this teachpack provides procedures that
      do not check for 1st-order usage.
|#
(module world mzscheme
  (require (lib "unit.ss")
           (only (lib "htdp-beginner.ss" "lang")
                 image?)
           ;(lib "world.ss" "htdp")
           (prefix world: (lib "world.ss" "htdp"))
           (file "posn.scm")) 
  (define-signature world^
    [empty-scene place-image add-line
     ;(struct color (red green blue))
     make-color color-red color-green color-blue color?
     image-color?
     rectangle circle text image-width image-height overlay overlay/xy
     end-of-time

     make-posn posn? weak-posn? posn-x posn-y
     
     (define-syntaxes (on-tick-event on-key-event on-redraw on-mouse-event big-bang)
       (values 
        (lambda (stx)
          (syntax-case stx ()
            [(_ cb-name) #'(begin (world:on-tick-event (lambda (w) (cb-name w))) 't)]))
        (lambda (stx)
          (syntax-case stx ()
            [(_ cb-name) #'(begin (world:on-key-event (lambda (k w) (cb-name k w))) 't)]))
        (lambda (stx)
          (syntax-case stx ()
            [(_ cb-name) #'(begin (world:on-redraw (lambda (w) (cb-name w))) 't)]))
        (lambda (stx)
          (syntax-case stx ()
            [(_ cb-name) #'(begin (world:on-mouse-event 
                                   (lambda (w x y evt) 
                                     (cb-name w x y evt)))
                                  't)]))
        (lambda (stx)
          (syntax-case stx ()
            [(_ width height freq w0)
             #'(begin (world:big-bang width height freq w0)
                      't)]
            [_ (raise-syntax-error #f "big-bang is a procedure that expects 4 arguments" stx)]))))])
  
  ;(define-unit-from-context world@ world^)
  (provide world^ world@)
  (define-unit world@
    (import)
    (export world^)
    ;; these need to be syntax that check for 1st order use.
    (define empty-scene world:empty-scene)
    (define place-image world:place-image)
    (define add-line world:add-line)
    (define make-color world:make-color)
    (define color-red world:color-red)
    (define color-green world:color-green)
    (define color-blue world:color-blue)
    (define color? world:color?)
    (define image-color? world:image-color?)
    (define rectangle world:nw:rectangle)
    (define circle world:circle)
    (define text world:text)
    (define image-width world:image-width)
    (define image-height world:image-height)
    (define overlay world:overlay)
    (define overlay/xy world:overlay/xy)
    (define end-of-time world:end-of-time)

    (define (make-posn x y)
      `(make-posn ,x ,y))

    (define (posn? v)
      (if (and (list? v)
               (= (length v) 3)
               (eq? (car v) 'make-posn)
               (integer? (cadr v))
               (integer? (caddr v)))
          't
          '()))

    (define (weak-posn? v)
      (if (and (list? v)
               (= (length v) 3)
               (eq? (car v) 'make-posn))
          't
          '()))

    (define (posn-x p)
      (cadr p))

    (define (posn-y p)
      (caddr p))
    
    )
  
  #|
  (require (only (lib "htdp-beginner.ss" "lang")
                 image?)
           (lib "world.ss" "htdp")
           (file "posn.scm")) ;; posns are in here.
  
  (provide (all-from-except (lib "world.ss" "htdp")
                            shrink-tl shrink-tr
                            shrink-bl shrink-br
                            shrink
                            rectangle 
                            nw:rectangle
                            image->alpha-color-list
                            alpha-color-list->image
                            make-alpha-color
                            alpha-color?
                            alpha-color-alpha
                            alpha-color-red
                            alpha-color-green
                            alpha-color-blue
                            
                            ;; These produce #t; we want T instead
                            on-tick-event
                            on-key-event
                            on-mouse-event
                            big-bang
                            on-redraw)
           (all-from (file "posn.scm")))
  
  (provide (rename acl2:image? image?)
           (rename nw:rectangle rectangle)
           (rename acl2:on-tick-event on-tick-event)
           (rename acl2:on-key-event on-key-event)
           (rename acl2:on-mouse-event on-mouse-event)
           (rename acl2:on-redraw on-redraw)
           (rename acl2:big-bang big-bang))

  (define (acl2:image? x)
    (if (image? x) 't '()))
  
  (define-syntax (acl2:on-tick-event stx)
    (syntax-case stx ()
      [(_ cb-name) #'(begin (on-tick-event (lambda (w) (cb-name w))) 't)]))
  
  (define-syntax (acl2:on-key-event stx)
    (syntax-case stx ()
      [(_ cb-name) #'(begin (on-key-event (lambda (k w) (cb-name k w))) 't)]))
  
  (define-syntax (acl2:on-mouse-event stx)
    (syntax-case stx ()
      [(_ cb-name) #'(begin (on-mouse-event (lambda (w x y evt) 
                                              (cb-name w x y evt))) 't)]))
  
  (define-syntax (acl2:on-redraw stx)
    (syntax-case stx ()
      [(_ cb-name) #'(begin (on-redraw (lambda (w) (cb-name w))) 't)]))
  
  (define-syntax (acl2:big-bang stx)
    (syntax-case stx ()
      [(_ width height freq w0)
       #'(begin (big-bang width height freq w0)
                't)]
      [_ (raise-syntax-error #f "big-bang is a procedure that expects 4 arguments" stx)]))
  |#
  #;
  (define (acl2:big-bang width height freq w0) 
    (big-bang width height freq w0)
    't)
  
  )