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(module downstroke-animation *
(import scheme
(chicken base)
(chicken keyword)
downstroke-entity
downstroke-world)
;; ---- Animation data accessors ----
(define (animation-frames anim) (get-keyword #:frames anim))
(define (animation-duration anim) (get-keyword #:duration anim))
;; ---- frame->tile-id ----
;; Given a frames list and frame index, return the tile ID (1-indexed).
(define (frame->tile-id frames frame-idx)
(+ 1 (list-ref frames (modulo frame-idx (length frames)))))
;; ---- set-animation ----
;; Switch to a new animation, resetting frame and tick counters.
;; No-op if the animation is already active (avoids restart mid-loop).
(define (set-animation entity name)
(if (eq? (entity-ref entity #:anim-name #f) name)
entity
(entity-set (entity-set (entity-set entity #:anim-name name)
#:anim-frame 0)
#:anim-tick 0)))
;; ---- animate-entity ----
;; Advance the animation tick/frame counter for one game tick.
;; Pass the animation table for this entity's type.
;; Entities without #:anim-name are returned unchanged.
(define (advance-animation entity anim)
(let* ((tick (+ 1 (entity-ref entity #:anim-tick 0)))
(duration (animation-duration anim))
(frames (animation-frames anim))
(frame (entity-ref entity #:anim-frame 0)))
(if (>= tick duration)
(let ((new-frame (modulo (+ frame 1) (length frames))))
(entity-set (entity-set (entity-set entity
#:anim-tick 0)
#:anim-frame new-frame)
#:tile-id (frame->tile-id frames new-frame)))
(entity-set (entity-set entity #:anim-tick tick)
#:tile-id (frame->tile-id frames frame)))))
(define (animate-entity entity animations)
(let* ((anim-name (entity-ref entity #:anim-name #f))
(entry (and anim-name (assq anim-name animations)))
(anim (and entry (cdr entry))))
(if anim
(advance-animation entity anim)
entity)))
) ;; End of animation module
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