+
+
+;;; 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)
+ (lambda (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)
+ (cons key nc)))))
+
+(define (remove-entity key)
+ (lambda (entities components)
+ (let ((clist (map (lambda (c) (car c)) (assoc-ref entities key)))
+ (entity (assoc key entities)))
+ (values
+ (assoc-remove! entities key)
+ (unregister-components key clist components)
+ entity))))
+
+(define (set-entity key . new-components)
+ (lambda (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))
+ (cons key nc)))))
+
+(define (set-entity-components key . new-components)
+ (lambda (entities components)
+ (let ((nc (normalize-components new-components))
+ (clist (alist-copy (assoc-ref entities key))))
+ (for-each
+ (lambda (c)
+ (assoc-set! clist (car c) (cdr c)))
+ nc)
+ (values
+ (assoc-set! entities key clist)
+ (register-components key (map (lambda (c) (car c)) nc) components)
+ (cons key clist)))))
+
+(define (remove-entity-components key . old-components)
+ (lambda (entities components)
+ (let ((clist (alist-copy (assoc-ref entities key))))
+ (for-each
+ (lambda (c)
+ (assoc-remove! clist c))
+ old-components)
+ (values
+ (assoc-set! entities key clist)
+ (unregister-components key old-components components)
+ (cons key clist)))))
+
+(define (modify-entities changes entities components)
+ (cond ((null? changes)
+ (values entities components))
+ (else
+ (receive (e c) ((car changes) entities components)
+ (modify-entities (cdr changes) e c)))))
+
+(export new-entity
+ remove-entity
+ set-entity
+ set-entity-components
+ remove-entity-components
+ modify-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-syntax make-system
+ (syntax-rules ()
+ ((_ ((name (component-type ...)) ...) form ...)
+ (lambda (entities components)
+ (let ((name (map (lambda (x)
+ (cons (car x)
+ (filter (lambda (x)
+ (memq (car x) '(component-type ...)))
+ (cdr x))))
+ (map (lambda (x)
+ (assoc x entities))
+ (find-entities-by-components components '(component-type ...)))))
+ ...)
+ (let ((res (begin form ...)))
+ (lambda* (#:optional (entities2 #f) (components2 #f))
+ (let ((e (if (and entities2 components2) entities2 entities))
+ (c (if (and entities2 components2) components2 components)))
+ (modify-entities res e c)))))))))
+
+(define-syntax define-system
+ (syntax-rules ()
+ ((_ system-name ((name (component-type ...)) ...) form ...)
+ (define system-name
+ (make-system ((name (component-type ...)) ...)
+ form
+ ...)))))
+
+(define (join-systems . systems)
+ (lambda (entities components)
+ (let run ((s systems) (e entities) (c components))
+ (cond ((null? s)
+ (values e c))
+ (else
+ (receive (e2 c2) (((car s) e c))
+ (run (cdr s) e2 c2)))))))
+
+(define (threaded-systems . systems)
+ (lambda (entities components)
+ (let run-wait ((thd
+ (map
+ (lambda (s)
+ (call-with-new-thread
+ (lambda () (s entities components))))
+ systems))
+ (e entities) (c components))
+ (cond ((null? thd)
+ (values e c))
+ (else
+ (receive (e2 c2) ((join-thread (car thd)) e c)
+ (run-wait (cdr thd) e2 c2)))))))
+
+(define (group-systems . systems)
+ (cond ((null? systems)
+ (make-system ()))
+ ((= (length systems) 1)
+ (car systems))
+ (else
+ (join-systems systems))))
+
+(export find-entities-by-components
+ define-system
+ make-system
+ join-systems
+ threaded-systems
+ group-systems)
+
+
+;;; Entities and components access inside systems
+
+(define (get-key entity)
+ (car entity))
+
+(define (get-component component-name entity)
+ (assoc-ref (cdr entity) component-name))
+
+(export get-key
+ get-component)