+
+
+;;; Entities and components
+
+(define (normalize-components components)
+ (map
+ (lambda (c)
+ (if (record? c)
+ `(,(get-component-type c) . ,c)
+ c))
+ components))
+
+(define (register-components entity components clist)
+ (cond ((null? components) clist)
+ (else
+ (let* ((type (car components))
+ (elist (assoc-ref clist type)))
+ (register-components entity (cdr components)
+ (assoc-set! clist type
+ (cond (elist
+ (lset-adjoin eq? elist entity))
+ (else
+ (list entity)))))))))
+
+(define (unregister-components entity components clist)
+ (cond ((null? components) clist)
+ (else
+ (let* ((type (car components))
+ (elist (lset-difference eq? (assoc-ref clist type) (list entity))))
+ (unregister-components entity (cdr components)
+ (cond ((null? elist)
+ (assoc-remove! clist type))
+ (else
+ (assoc-set! clist type elist))))))))
+
+(define (new-entity new-components entities components)
+ (let ((key (gensym))
+ (nc (normalize-components new-components)))
+ (values
+ (acons key nc entities)
+ (register-components key
+ (map (lambda (c) (car c)) nc)
+ components)
+ key)))
+
+(define (remove-entity key entities components)
+ (let ((clist (map (lambda (c) (car c)) (assoc-ref entities key))))
+ (values
+ (assoc-remove! entities key)
+ (unregister-components key clist components))))
+
+(define (set-entity key new-components entities components)
+ (let* ((nc (normalize-components new-components))
+ (clist (map (lambda (c) (car c)) (assoc-ref entities key)))
+ (nclist (map (lambda (c) (car c)) nc)))
+ (values
+ (assoc-set! entities key nc)
+ (register-components key (lset-difference eq? nclist clist)
+ (unregister-components key (lset-difference eq? clist nclist) components)))))
+
+(define (set-entity-components key new-components entities components)
+ (define (set-components clist new-components)
+ (cond ((null? new-components)
+ clist)
+ (else
+ (set-components
+ (if (cdar new-components)
+ (assoc-set! clist (caar new-components) (cdar new-components))
+ (assoc-remove! clist (caar new-components)))
+ (cdr new-components)))))
+ (set-entity key (set-components (alist-copy (assoc-ref entities key)) (normalize-components new-components)) entities components))
+
+(define (set-entities new-entities entities components)
+ (cond ((null? new-entities)
+ (values entities components))
+ (else
+ (cond ((not (caar new-entities))
+ (receive (e c k) (new-entity (cdar new-entities) entities components)
+ (set-entities (cdr new-entities) e c)))
+ ((not (cdar new-entities))
+ (receive (e c) (remove-entity (caar new-entities) entities components)
+ (set-entities (cdr new-entities) e c)))
+ (else
+ (receive (e c) (set-entity-components (caar new-entities) (cdar new-entities) entities components)
+ (set-entities (cdr new-entities) e c)))))))
+
+
+(export new-entity
+ remove-entity
+ set-entity
+ set-entity-components
+ set-entities)
+
+
+;;; Making systems
+
+(define* (find-entities-by-components c t)
+ (cond ((null? t) '())
+ (else
+ (let* ((e (assoc-ref c (car t)))
+ (e* (if e e '())))
+ (cond ((null? (cdr t)) e*)
+ (else
+ (lset-intersection eq? e* (find-entities-by-components c (cdr t)))))))))
+
+
+(define (make-system component-types system-fun)
+ (lambda (entities components)
+ (let* ((e (find-entities-by-components components component-types))
+ (e* (map (lambda (x) (assoc x entities)) e))
+ (e** (map (lambda (x) (cons (car x) (filter (lambda (x) (memq (car x) component-types)) (cdr x)))) e*))
+ (res (system-fun e**)))
+ (lambda* (#:optional (entities2 #f) (components2 #f))
+ (let ((e (if (and entities2 components2) entities2 entities))
+ (c (if (and entities2 components2) components2 components)))
+ (set-entities res e c))))))
+
+
+(export find-entities-by-components
+ make-system)