extract the grid to its own class

js/game_manager.js

@@ -3,81 +3,40 @@ function GameManager(size, actuator) {
   this.actuator   = actuator;
 
   this.startTiles = 2;
-  this.grid       = [];
+  this.grid       = new Grid(this.size);
 
   this.setup();
 }
 
 // Set up the game
 GameManager.prototype.setup = function () {
-  this.buildGrid();
   this.addStartTiles();
 
   // Update the actuator
-  this.update();
-};
-
-// Build a grid of the specified size
-GameManager.prototype.buildGrid = function () {
-  for (var y = 0; y < this.size; y++) {
-    this.grid[y] = [];
-    for (var x = 0; x < this.size; x++) {
-      this.grid[y].push(null);
-    }
-  }
+  this.actuate();
 };
 
 // Set up the initial tiles to start the game with
 GameManager.prototype.addStartTiles = function () {
   for (var i = 0; i < this.startTiles; i++) {
-    this.addTile();
+    this.addRandomTile();
   }
 };
 
 // Adds a tile in a random position
-GameManager.prototype.addTile = function () {
-  this.insertTile(new Tile(this.randomCell()));
-};
-
-// Find the first available random position
-GameManager.prototype.randomCell = function () {
-  // TODO: build a map of available positions and choose from it
-  var self = this;
-
-  var position;
-
-  function randomPosition() {
-    return Math.floor(Math.random() * self.size);
-  }
-
-  do {
-    position = {
-      x: randomPosition(),
-      y: randomPosition()
-    };
-  } while (this.cellOccupied(position));
-
-  return position;
-};
-
-// Check if the specified cell is taken
-GameManager.prototype.cellOccupied = function (cell) {
-  return !!this.grid[cell.x][cell.y];
-};
-
-// Insert a tile at the specified position
-GameManager.prototype.insertTile = function (tile) {
-  this.grid[tile.x][tile.y] = tile;
+GameManager.prototype.addRandomTile = function () {
+  var tile = new Tile(this.grid.randomAvailableCell());
+  this.grid.insertTile(tile);
 };
 
 // Sends the updated grid to the actuator
-GameManager.prototype.update = function () {
-  this.actuator.update(this.grid);
+GameManager.prototype.actuate = function () {
+  this.actuator.actuate(this.grid);
 };
 
 // Move the grid in the specified direction
 GameManager.prototype.move = function (direction) {
   // 0: up, 1: right, 2:down, 3: left
 
-  this.update();
+  this.actuate();
 };