(define-module (game animation)
#:use-module (game tileset)
#:use-module (ice-9 match)
#:use-module (srfi srfi-9)
#:export (make-frame
frame?
frame-tile
frame-duration
make-animation
animation?
animation-tileset
animation-time
animation-frames
update-animation
draw-animation))
(define-record-type
(make-frame tile duration)
frame?
(tile frame-tile)
(duration frame-duration))
(define-record-type
(%make-animation tileset frames time frame-idx)
animation?
(tileset animation-tileset)
(frames animation-frames)
(time animation-time set-animation-time!)
(frame-idx animation-frame-idx set-animation-frame-idx!))
(define (make-animation tileset frames)
(%make-animation tileset frames 0.0 0))
(define (flonum? x)
(and (real? x) (inexact? x)))
(define (update-animation anim dt)
(unless (flonum? dt)
(error "not a flonum" dt))
(match anim
(($ tileset frames (? flonum? time) idx)
(let ((time* (+ time dt)))
(match (vector-ref frames idx)
(($ tile duration)
(cond
((>= time* duration)
(set-animation-frame-idx! anim (modulo (1+ idx) (vector-length frames)))
(set-animation-time! anim (- time* duration)))
(else
(set-animation-time! anim time*)))))))))
(define (draw-animation context anim x y)
(match anim
(($ tileset frames time idx)
(draw-tile context tileset (frame-tile (vector-ref frames idx)) x y))))