Refactor Simulation to be List of dumb cells

Cells are now only an empty struct, they carry no information beyond needing to be re-rendered. All Simulation logic is handled in the Simulation Class.

lib/src/Cell.dart

@@ -1,36 +1,6 @@
 import 'package:rules_of_living/src/Rule.dart';
 
 class Cell {
-  bool state;
-  bool nextState = false;
-  List<Rule> surviveRules = new List<Rule>();
-  List<Rule> birthRules = new List<Rule>();
-
   /// For determining if render updates are necessary in [Grid].render() function
   bool dirty = false;
-
-  Cell([bool state = false]) : this.state = state;
-
-  // Sets the actual state to what it should be next update
-  // Returns the newly assumed actual state of the cell.
-  bool advanceState() {
-    this.state = this.nextState;
-    this.nextState = false;
-
-    this.dirty = true;
-
-    return this.state;
-  }
-
-  void update(int neighbors) {
-    if (state == true) {
-      surviveRules.forEach((Rule rule) {
-        if (rule.evaluate(neighbors) == true) this.nextState = true;
-      });
-    } else {
-      birthRules.forEach((Rule rule) {
-        if (rule.evaluate(neighbors) == true) this.nextState = true;
-      });
-    }
-  }
 }

lib/src/Simulation.dart

@@ -3,7 +3,6 @@ import 'dart:math' as math;
 
 import 'package:rules_of_living/src/Cell.dart';
 import 'package:rules_of_living/src/Grid.dart';
-import 'package:rules_of_living/src/Rule.dart';
 
 enum CellPattern { SpaceShip, Blinker }
 
@@ -31,18 +30,7 @@ class Simulation {
   }
 
   Cell _getGOLCell([bool defaultState = false]) {
-    Cell cell = Cell(defaultState);
-    Rule threeTrue = new Rule((int n) {
-      if (n == 3) return true;
-      return false;
-    });
-    Rule twoTrue = new Rule((int n) {
-      if (n == 2) return true;
-      return false;
-    });
-    cell.surviveRules.add(twoTrue);
-    cell.surviveRules.add(threeTrue);
-    cell.birthRules.add(threeTrue);
+    Cell cell = Cell();
     return cell;
   }
 
@@ -117,12 +105,15 @@ class Simulation {
   }
 
   void setCellState(int x, int y, bool state) {
-    if (y < map.height && x < map.width) map.get(x, y).state = state;
+    if (y >= map.height || x >= map.width) return;
+
+    state ? map.set(x, y, Cell()) : map.set(x, y, null);
   }
 
   bool getCellState(int x, int y) {
-    if (y < map.height && x < map.width) return map.get(x, y).state;
-    return null;
+    if (y >= map.height || x >= map.width) return null;
+
+    return map.get(x, y) == null ? false : true;
   }
 
   Map<int, Cell> update() {
@@ -131,10 +122,15 @@ class Simulation {
     for (int i = 0; i < map.length; i++) {
       math.Point p = map.toCoordinates(i);
       Cell el = map[i];
-      el.update(getSurroundingNeighbors(p.x, p.y, 1));
-      stateChanges[i] = el;
+      bool changed = false;
+      int neighbors = getSurroundingNeighbors(p.x, p.y, 1);
+      if (el == null && neighbors == 3) {
+        stateChanges[i] = Cell();
+      } else if (el != null && neighbors != 2 && neighbors != 3) {
+        stateChanges[i] = null;
+      }
     }
-    stateChanges.forEach((_, el) => el.advanceState());
+    stateChanges.forEach((i, el) => map[i] = el);
     stateChanges.length != 0 ? _dirty = true : false;
     return stateChanges;
   }
@@ -147,7 +143,7 @@ class Simulation {
             iy >= 0 &&
             ix < map.width &&
             iy < map.height &&
-            map.get(ix, iy).state == true &&
+            map.get(ix, iy) != null &&
             !(x == ix && y == iy)) count++;
       }
     }
@@ -169,7 +165,7 @@ class Simulation {
         ctx.strokeRect(p.x * brickW, p.y * brickH, brickW, brickH);
       }
 
-      if (map[i].state == true)
+      if (map[i] != null)
         ctx.setFillColorRgb(155, 155, 255);
       else
         ctx.setFillColorRgb(0, 0, 0);