(use-modules (reactive)
             (hoot ffi))

(define-foreign get-element-by-id
  "document" "getElementById"
  (ref string) -> (ref null extern))

(define-foreign element-inner-text
  "element" "innerText"
  (ref null extern) -> (ref string))
(define-foreign set-element-inner-text!
  "element" "setInnerText"
  (ref null extern) (ref string) -> none)

(define-foreign add-event-listener!
  "element" "addEventListener"
  (ref null extern) (ref string) (ref null extern) -> none)


(define cell-a (make-cell 42))
(format #t "~s\n" (! cell-a))
(define deriv-a (~ (format #f "value is: ~s" (! cell-a))))

(format #t "~a\n" (! deriv-a))

(! cell-a 56)

(format #t "~a\n" (! deriv-a))

(define counter-cell (make-cell 0))

(define button-elem (get-element-by-id "button"))
(add-event-listener!
 button-elem
 "click"
 (procedure->external
  (lambda (e) (! counter-cell (1+ (! counter-cell))))))

(define counter-elem (get-element-by-id "counter"))
(define counter-deriv (~ (set-element-inner-text! counter-elem (number->string (! counter-cell))) #f))