From 0cf99813777069f2fce8fe895fbbdcaaf98699eb Mon Sep 17 00:00:00 2001
From: Javier Sancho <jsf@jsancho.org>
Date: Sun, 17 Nov 2013 08:32:23 +0100
Subject: [PATCH] Engine Execution

* src/engine.scm: Engine execution with inner properties for looping
                  delay and other future parameters. Mutexes are used
                  to prevent accessing entities and engines in an
                  undesired way.
---
 src/engine.scm | 65 ++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 61 insertions(+), 4 deletions(-)

diff --git a/src/engine.scm b/src/engine.scm
index 0770e09..4e311a0 100644
--- a/src/engine.scm
+++ b/src/engine.scm
@@ -25,21 +25,30 @@
 
 ;;; Engine definitions
 
+(define (default-delay) 0.1)
+
+(define-component engine-inner-properties
+  delay)
+
 (define-record-type engine
-  (make-engine-record entities mutex system)
+  (make-engine-record entities mutex running-mutex system)
   engine?
   (entities engine-entities set-engine-entities!)
   (mutex engine-mutex set-engine-mutex!)
+  (running-mutex engine-running-mutex set-engine-running-mutex!)
   (system engine-system set-engine-system!))
 
 (set-record-type-printer! engine
   (lambda (record port)
-    (format port "#<[engine] entities: ~a>"
+    (format port "#<[engine] state: ~a, entities: ~a>"
+	    (if (engine-running? record) "Running" "Stopped")
 	    (length (car (engine-entities record))))))
 
 (define (make-engine . systems)
   (make-engine-record
-   '(() ())
+   (receive (e c) ((new-entity (make-engine-inner-properties (default-delay))) '() '())
+     (list e c))
+   (make-mutex)
    (make-mutex)
    (if (not (= (length systems) 1))
        (join-systems systems)
@@ -51,8 +60,14 @@
      (define name
        (make-engine system ...)))))
 
+(define (engine-running? engine)
+  (mutex-locked? (engine-running-mutex engine)))
+
 (export make-engine
-	define-engine)
+	define-engine
+	engine-running?)
+
+(export-component engine-inner-properties)
 
 
 ;;; Engine Access Protocol Interface
@@ -75,6 +90,11 @@
 (define* (get-entity key #:key (engine (current-engine)))
   (assoc key (car (engine-entities engine))))
 
+(define* (get-entities-by-components component-types #:key (engine (current-engine)))
+  (map (lambda (e)
+	 (get-entity e #:engine engine))
+       (find-entities-by-components (cadr (engine-entities engine)) component-types)))
+
 (define-syntax define-entity-setter
   (syntax-rules ()
     ((_ name! name)
@@ -105,9 +125,46 @@
 (export current-engine
 	set-current-engine!
 	get-entity
+	get-entities-by-components
 	new-entity!
 	remove-entity!
 	set-entity!
 	set-entity-components!
 	remove-entity-components!
 	with-engine)
+
+
+;;; Engine execution
+
+(define (start-engine engine)
+  (cond ((not (engine-running? engine))
+	 (with-mutex (engine-running-mutex engine)
+	   (let loop ()
+	     (let ((delay 0))
+	       (with-engine engine
+	         (receive (e c) ((apply (engine-system engine) (engine-entities engine)))
+		   (set-engine-entities! engine (list e c)))
+		 (set! delay (engine-inner-properties-delay (get-component 'engine-inner-properties (car (get-entities-by-components '(engine-inner-properties)))))))
+	       (usleep (inexact->exact (* delay 1000000))))
+	     (if (not (engine-stopping? engine #:clean #t))
+		 (loop)))))))
+
+(define (stop-engine engine)
+  (with-engine engine
+    (new-entity! '(engine-halt . #t)))
+  'engine-halt)
+
+(define* (engine-stopping? engine #:key (clean #f))
+  (let ((halt #f))
+    (with-engine engine
+      (let halt-engine ((halts (get-entities-by-components '(engine-halt))))
+	(cond ((not (null? halts))
+	       (set! halt #t)
+	       (cond (clean
+		      (remove-entity! (caar halts))
+		      (halt-engine (cdr halts))))))))
+    halt))
+
+(export start-engine
+	stop-engine
+	engine-stopping?)
-- 
2.39.2