Convert entities to alists

1 files changed, 23 insertions, 14 deletions

diff --git a/animation.scm b/animation.scm
index 0d961a1..8843512 100644
--- a/animation.scm
+++ b/animation.scm
@@ -1,18 +1,25 @@
 (module downstroke-animation *
 (import scheme
         (chicken base)
-        (chicken keyword)
 	(chicken pretty-print)
 	(only srfi-1 filter)
         downstroke-entity
         downstroke-world)
 
-;; ---- Animation data accessors ----
+;; Animation definitions are alists (converted from plist form in the user's
+;; prefab data file by load-prefabs). Each animation is an alist with keys
+;; #:name, #:frames, optional #:duration.
 
-(define (animation-frames anim)
-  (get-keyword #:frames anim))
-(define (animation-duration anim)
-  (get-keyword #:duration anim))
+;; Look up a key in an animation alist. Mirrors entity-ref:
+;; a non-procedure default is returned as-is on miss; a procedure default
+;; is invoked as a thunk.
+(define (animation-ref anim key #!optional default)
+  (cond ((assq key anim) => cdr)
+        ((procedure? default) (default))
+        (else default)))
+
+(define (animation-frames anim) (animation-ref anim #:frames))
+(define (animation-duration anim) (animation-ref anim #:duration))
 
 (define (frame-by-idx frames frame-idx)
   (list-ref frames (modulo frame-idx (length frames))))
@@ -43,8 +50,10 @@
 
 
 (define (animation-by-name animations name)
-  (let ((matching-anims (filter (lambda (anim) (eq? (get-keyword #:name anim) name)) animations)))
-    (if matching-anims
+  (let ((matching-anims
+         (filter (lambda (anim) (eq? (animation-ref anim #:name) name))
+                 animations)))
+    (if (pair? matching-anims)
 	(car matching-anims)
 	#f)))
 
@@ -61,13 +70,13 @@
     (if (>= tick duration)
         (let ((new-frame-id (modulo (+ frame 1) (length frames))))
           (entity-set-many entity
-			   (list (cons #:anim-tick 0)
-				 (cons #:anim-frame new-frame-id)
-				 (cons #:tile-id (frame->tile-id frames new-frame-id))
-				 (cons #:duration (frame->duration frames new-frame-id)))))
+			   `((#:anim-tick . 0)
+			     (#:anim-frame . ,new-frame-id)
+			     (#:tile-id . ,(frame->tile-id frames new-frame-id))
+			     (#:duration . ,(frame->duration frames new-frame-id)))))
         (entity-set-many entity
-			 (list (cons #:anim-tick tick)
-			       (cons #:tile-id (frame->tile-id frames frame)))))))
+			 `((#:anim-tick . ,tick)
+			   (#:tile-id . ,(frame->tile-id frames frame)))))))
 
 (define (animate-entity entity animations)
   (let* ((anim-name (entity-ref entity #:anim-name #f))