System addition/removal. I'm not doing topo sort (today)

engine/core.scm

@@ -1,7 +1,7 @@
-(module (engine core)
-(add-entity add-named-entity remove-entity)
+(module (engine core) ()
 (import scheme
 	(chicken base)
+	(chicken module)
 	;; raylib
 	(srfi 1)
 	(srfi 69)
@@ -89,6 +89,14 @@
    del-entity-queue)
   (set! del-entity-queue '()))
 
+;; Resolve all queued entity changes
+(define (resolve-entity-queue)
+  (remove-queued-entities)
+  (add-queued-entities))
+
+;; Entity creation/removal interface
+(export add-named-entity add-entity remove-entity)
+
 ;; Create an entity in the world and return it's ID
 (define (add-named-entity id . components)
   (assert (symbol? id))
@@ -105,4 +113,111 @@
   (assert (symbol? id))
   (queue-del-entity id)
   id)
+
+;; System record interface
+(export make-system system? system-name system-rendering
+	system-priority set-system-priority! system-criteria
+	set-system-criteria! system-process set-system-process!)
+
+;; The system record
+(define-record-type <system>
+  (internal-make-system name rendering priority criteria process)
+  system?
+  (name system-name)
+  (rendering system-rendering)
+  (priority system-priority internal-set-system-priority!)
+  (criteria system-criteria internal-set-system-criteria!)
+  (process system-process internal-set-system-process!))
+
+;; Type-checked system constructor wrapper
+(define (make-system name rendering priority criteria process)
+  (assert (symbol? name))
+  (assert (and (symbol? rendering) (member rendering '(3d 2d screen none))))
+  (assert (integer? priority))
+  (assert (every symbol? criteria))
+  (assert (procedure? process))
+  (internal-make-system name rendering priority criteria process))
+
+;; Type-checked system priority mutator
+(define (set-system-priority! system priority)
+  (assert (system? system))
+  (assert (integer? priority))
+  (internal-set-system-priority! system priority))
+
+;; Type-checked system criteria mutator
+(define (set-system-criteria! system criteria)
+  (assert (system? system))
+  (assert (every symbol? criteria))
+  (internal-set-system-criteria! system criteria))
+
+;; Type-checked system process mutator
+(define (set-system-process! system process)
+  (assert (system? system))
+  (assert (procedure? process))
+  (internal-set-system-process! system process))
+
+;; The systems list
+(define systems '())
+
+;; Immediately add a new system
+(define (add-system-now system)
+  (set! systems
+    (append systems (list system))))
+
+;; Immediately remove a new system
+(define (remove-system-now name)
+  (set! systems
+    (delete name systems
+	    (lambda (n el)
+	      (eqv? n (system-name el))))))
+
+;; System addition/deletion queues
+(define add-system-queue '())
+(define del-system-queue '())
+
+;; Add a system to the incoming queue
+(define (queue-add-system system)
+  (set! add-system-queue
+    (append add-system-queue (list system))))
+
+;; Add a system to the deletion queue
+(define (queue-del-system name)
+  (set! del-system-queue
+    (append del-system-queue (list name))))
+
+;; Resolve all new system creations
+(define (add-queued-systems)
+  (for-each
+   (lambda (system)
+     (add-system-now system))
+   add-system-queue)
+  (set! add-system-queue '()))
+
+;; Resolve all queued system deletions
+(define (remove-queued-systems)
+  (for-each
+   (lambda (system-name)
+     (remove-system-now system-name))
+   del-system-queue)
+  (set! del-system-queue '()))
+
+;; Resolve all queued system changes
+(define (resolve-system-queue)
+  (remove-queued-systems)
+  (add-queued-systems))
+
+;; System creation/removal interface
+(export add-system remove-system)
+
+;; Add a system to the state processing and return its name
+(define (add-system system)
+  (assert (system? system))
+  (queue-add-system system)
+  (system-name system))
+
+;; Remove a system from process 
+(define (remove-system name)
+  (assert (symbol? name))
+  (queue-del-system name)
+  name)
 )