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README.org

@@ -8,8 +8,8 @@ Imugi is an ECS engine.
 ** Entities
 Entities are game objects stored in an SRFI-69 hash table. A hash table is used for O(1) lookup.
 Entity keys within the hash table are symbols, either set intentionally or automatically generated via gensym.
-Entities are identified by their hash, and are each a list of components.
+Entities are identified by their key, and are each a list of components.
-Entities are queued for addition and removal to/form the hash table ~world~.
+Entities are queued for addition and removal to/from the hash table ~world~.
 Entity removal and addition is performed at the beginning of each frame, with removal occuring first.
 
 There exists a hash map of SRFI-113 sets, ~component-sets~.

engine/core.scm

@@ -0,0 +1,104 @@
+(module (engine core) *
+(import scheme
+	(chicken base)
+	raylib
+	(srfi 69)
+	(srfi 99)
+	(srfi 113)
+	(srfi 128))
+
+;; The world hash table
+(define world (make-hash-table))
+;; The component-sets hash table
+(define component-sets (make-hash-table))
+
+;; Insert an entity into component-sets, either creating
+;; a new set or updating an existing one for the component
+;; type provided.
+(define (classify-entity-by id component)
+  (let ((component-type (rtd-name (record-rtd component))))
+    (if (hash-table-exists? component-sets component-type)
+	(let ((component-set (hash-table-ref component-sets component-type)))
+	  ;; TODO: this could be nicer with set-adjoin! but I'm not sure if hash-table-ref is locative
+	  (hash-table-set! component-sets
+			   component-type
+			   (set-adjoin component-set
+				       id)))
+	(hash-table-set! component-sets
+			 component-type
+			 (set (make-eq-comparator) id)))))
+
+;; Create an entity in the world immediately,
+;; and add it to the requisite component-sets
+(define (create-entity id components)
+  (hash-table-set! world id components)
+  (for-each
+   (lambda (component)
+     (classify-entity-by id component))
+   components))
+
+;; Remove a single matching item from a set
+(define (set-remove! set element)
+  (set-search! set element
+	       (lambda (insert ignore)
+		 (ignore #f))
+	       (lambda (old update remove)
+		 (remove old))))
+
+;; Remove an entity from the world immediately,
+;; as well as from all component sets.
+(define (remove-entity id)
+  (hash-table-delete! world id)
+  (for-each
+   (lambda (set)
+     (set-remove! set id))
+   (hash-table-values component-sets)))
+
+;; Queues for entity creation and deletion
+(define add-entity-queue '())
+(define del-entity-queue '())
+
+;; Add an entity to the incoming queue
+;; TODO: append! doesn't work here and IDK why
+(define (queue-add-entity id components-lst)
+  (set! add-entity-queue
+    (append add-entity-queue (list (cons id components-lst)))))
+
+;; Add an entity to the deletion queue
+(define (queue-del-entity id)
+  (set! del-entity-queue
+    (append del-entity-queue (list id))))
+
+;; Resolve all new entity creations
+(define (add-queued-entities)
+  (for-each
+   (lambda (entity)
+     (let ((id (car entity))
+	   (components (cdr entity)))
+       (create-entity id components)))
+   add-entity-queue)
+  (set! add-entity-queue '()))
+
+;; Resolve all queued entity deletions
+(define (remove-queued-entities)
+  (for-each
+   (lambda (id)
+     (remove-entity id))
+   del-entity-queue)
+  (set! del-entity-queue '()))
+
+;; Create an instance of an entity in the world and return it's ID
+(define (add-instance-named id . components)
+  (queue-add-entity id components)
+  id)
+
+;; Shortcut for anonymous instancing
+(define (add-instance . components)
+  (apply add-instance-named (gensym) components))
+
+;; Remove an instance from the world
+(define (remove-instance id)
+  (queue-del-entity id)
+  id)
+
+)