;;-*-Lisp-*-
(in-package goal)

;; name: smush-control-h.gc
;; name in dgo: smush-control-h
;; dgos: GAME, ENGINE

;; A "smush-control" generates a damped sinusoidal floating point value.
;;  - on each full period, the amplitude and period are changed (multiplied)
;;  - there is a maximum duration.
;;  - the amplitude is additionally linearly scaled to go to zero over the duration.

(deftype smush-control (structure)
  ((start-time  time-frame  :offset-assert 0)
   (period      float  :offset-assert 8)
   (duration    float  :offset-assert 12)
   (amp         float  :offset-assert 16)
   (damp-amp    float  :offset-assert 20)
   (damp-period float  :offset-assert 24) ;; set a negative value here to flag as die on next update
   (ticks       float  :offset-assert 28)
   )
  :pack-me
  :method-count-assert 15
  :size-assert         #x20
  :flag-assert         #xf00000020
  (:methods
   (set-zero! (_type_) _type_ 9)
   (update! (_type_) float 10)
   (get-no-update (_type_) float 11)
   (activate! (_type_ float int int float float) _type_ 12)
   (nonzero-amplitude? (_type_) symbol 13)
   (die-on-next-update! (_type_) _type_ 14)
   )
  )

(defmethod nonzero-amplitude? smush-control ((obj smush-control))
  "Return #t if amp is not zero, #f otherwise"
  (declare (inline))
  
  (!= (-> obj amp) 0.0)
  )

(defmethod set-zero! smush-control ((obj smush-control))
  (set! (-> obj period) 0.0)
  (set! (-> obj duration) 0.0)
  (set! (-> obj amp) 0.0)
  (set! (-> obj damp-amp) 0.0)
  (set! (-> obj damp-period) 0.0)
  (set! (-> obj ticks) 0.0)
  obj
  )

(defmethod update! smush-control ((obj smush-control))
  "Run the smush control and return the result. Updates the internal state."

  (cond
    ((nonzero-amplitude? obj)
     (let* ((time-since-start (the float (- (-> *display* base-frame-counter) (-> obj start-time))))
            ;; use float to int rounding to figure out offset into the current period.
            (time-since-period-start (- time-since-start (* (the float (the int (/ time-since-start (-> obj period)))) (-> obj period))))
            )
         ;; we completed a new period!
         (when (>= (- time-since-start (-> obj ticks)) (-> obj period))
           ;; once per period updates of amp/period
           (set! (-> obj amp) (* (-> obj amp) (-> obj damp-amp)))
           (set! (-> obj period) (* (-> obj period) (-> obj damp-period)))
           ;; store the ticks that we did this on
           (set! (-> obj ticks) time-since-start)
           ;; you can set damp-period to a negative number to indicate
           ;; that it should die on the next update. Do that here.
           (if (< (-> obj damp-period) 0.0)
             (set-zero! obj)
             )
           )

         ;; absolute duraction check
         (if (>= time-since-start (-> obj duration))
           (set-zero! obj)
           )
         ;; sine term multiplied by amplitude, and scaled by how much is left to go.
         (* (sin (/ (* DEGREES_PER_ROT time-since-period-start) (-> obj period)))
            (* (-> obj amp)
               (/ (- (-> obj duration) time-since-start) (-> obj duration)))
            )
         )
     )
    ;; amplitude = 0, die.
    (else 0.0)
    )
  )

(defmethod get-no-update smush-control ((obj smush-control))
  "Get the value, but don't update internal state"

  (cond
    ((nonzero-amplitude? obj)
     (let* ((time-since-start (the float (- (-> *display* base-frame-counter) (-> obj start-time))))
            (time-since-period-start (- time-since-start (* (the float (the int (/ time-since-start (-> obj period)))) (-> obj period))))
            )
         (* (sin (/ (* DEGREES_PER_ROT time-since-period-start) (-> obj period)))
            (* (-> obj amp)
               (/ (- (-> obj duration) time-since-start) (-> obj duration)))
            )
         )
     )
    ;; amplitude = 0, die.
    (else 0.0)
    )
  )

(defmethod die-on-next-update! smush-control ((obj smush-control))
  "On the next call to update!, zero everything.
   Calls to get-no-update will still work."

  (if (nonzero-amplitude? obj)
    (set! (-> obj damp-period) -1.0)
    )
  obj
  )

(defmethod activate! smush-control ((obj smush-control)
                                    (arg0 float)
                                    (arg1 int)
                                    (arg2 int)
                                    (arg3 float)
                                    (arg4 float)
                                    )
  "Activate the smush! This only activates if the ongoing smush is mostly done."

  (when (>= (fabs (* 0.2 (-> obj amp)))
            (fabs (get-no-update obj))
            )
    (set! (-> obj amp) arg0)
    (set! (-> obj period) (the float arg1))
    (set! (-> obj duration) (the float arg2))
    (set! (-> obj damp-amp) arg3)
    (set! (-> obj damp-period) arg4)
    (set! (-> obj ticks) 0.0)
    (set! (-> obj start-time) (-> *display* base-frame-counter))
    )
  obj
  )