Extract EngineService into separate service

lib/service/configuration_service.dart

@@ -3,7 +3,7 @@ import 'dart:math';
 import 'package:rules_of_living/service/engine_service.dart';
 
 class ConfigurationService {
-  final EngineService engineService;
+  final EngineService _es;
 
   bool showGrid;
 
@@ -17,10 +17,10 @@ class ConfigurationService {
   int get simSpeed => _simSpeed;
   void set simSpeed(int val) {
     _simSpeed = val;
-    engineService.engine.stepsPerSecond = simSpeed;
+    _es.engine.stepsPerSecond = simSpeed;
   }
 
-  ConfigurationService(this.engineService) {
+  ConfigurationService(this._es) {
     showGrid = false;
     simSpeed = 5;
   }
@@ -30,8 +30,8 @@ class ConfigurationService {
   }
 
   void setGridSize({int x, int y}) {
-    x = x ?? engineService.engine.gridSize.x;
-    y = y ?? engineService.engine.gridSize.y;
-    engineService.engine.gridSize = Point(x, y);
+    x = x ?? _es.engine.gridSize.x;
+    y = y ?? _es.engine.gridSize.y;
+    _es.engine.gridSize = Point(x, y);
   }
 }

lib/service/control_service.dart

@@ -0,0 +1,43 @@
+import 'dart:html' as html;
+
+import 'package:rules_of_living/service/engine_service.dart';
+
+class ControlService {
+  EngineService _es;
+
+  ControlService(this._es);
+
+  void set canvas(html.CanvasElement canvas) => _es.engine.canvas = canvas;
+  html.CanvasElement get canvas => _es.engine.canvas;
+
+  void run() {
+    _es.engine.running = true;
+  }
+
+  void stop() {
+    _es.engine.running = false;
+  }
+
+  void toggleRunning() {
+    _es.engine.running = !_es.engine.running;
+  }
+
+  void step() {
+    _es.engine.step();
+  }
+
+  void reset() {
+    _es.engine.reset();
+  }
+
+  void addRandomPattern() {
+    _es.engine.running = false;
+    _es.engine.addPattern();
+  }
+
+  void clear() {
+    _es.engine.clear();
+  }
+
+  bool get isRunning => _es.engine.running;
+}

lib/service/engine_service.dart

@@ -1,48 +1,15 @@
-import 'dart:html' as html;
-
 import 'package:rules_of_living/src/Engine.dart';
 
 class EngineService {
-  Engine _engine;
+  Engine _uncachedEngineAccess;
 
-  Engine get engine => _engine ?? getEngine(Engine());
-
-  Engine getEngine(Engine engine) {
-    _engine = engine;
-    return _engine;
+  Engine get engine => _uncachedEngineAccess ?? _setCachedAndReturn(Engine());
+  void set engine(Engine newEngine) {
+    _uncachedEngineAccess = newEngine;
   }
 
-  void set canvas(html.CanvasElement canvas) => engine.canvas = canvas;
-  html.CanvasElement get canvas => engine.canvas;
-
-  void run() {
-    engine.running = true;
+  Engine _setCachedAndReturn(Engine newEngine) {
+    engine = newEngine;
+    return newEngine;
   }
-
-  void stop() {
-    engine.running = false;
-  }
-
-  void toggleRunning() {
-    engine.running = !engine.running;
-  }
-
-  void step() {
-    engine.step();
-  }
-
-  void reset() {
-    engine.reset();
-  }
-
-  void addRandomPattern() {
-    engine.running = false;
-    engine.addPattern();
-  }
-
-  void clear() {
-    engine.clear();
-  }
-
-  bool get isRunning => engine.running;
 }