Add a cache module

src/index.html

@@ -7,6 +7,7 @@
 		<script src="js/session.js"></script>
 		<script src="js/async.js"></script>
 		<script src="js/dom.js"></script>
+		<script src="js/cache.js"></script>
 		<script src="js/screen.js"></script>
 		<script src="js/buttons.js"></script>
 		<script src="js/messaging.js"></script>

src/js/automaton.js

@@ -1,4 +1,4 @@
-function Automaton(async, dom, messaging, screen, session, ui) {
+function Automaton(async, cache, dom, messaging, screen, session, ui) {
 	var menus = {
 		start: {
 			entries: [
@@ -56,6 +56,15 @@ function Automaton(async, dom, messaging, screen, session, ui) {
 			name: 'textSpeed'
 		}
 	};
+	var areas = new cache.make(function(key) {
+		messaging.send({tag: 'Load', area: key});
+		return async.bind(
+			messaging.receive(function(message) {
+				return message.tag == 'Area';
+			}),
+			function(message) { return async.wrap(message.contents); }
+		);
+	});
 	var game = session.get('game');
 	if(game != undefined) {
 		menus.start.entries.unshift(

src/js/cache.js

@@ -0,0 +1,54 @@
+function Cache(async) {
+	function Cache(loader) {
+		this.loader = loader;
+		this.loaded = {};
+		this.loading = {};
+	}
+
+	Cache.prototype.get = function(key) {
+		return function(f) {
+			if(this.loaded[key] != undefined) {
+				f(this.loaded[key]);
+			} else {
+				this.startLoading(key);
+				this.loading[key].push(f);
+				this.loader(key)(this.store(key));
+			}
+		}.bind(this);
+	};
+
+	Cache.prototype.warmUp = function(key) {
+		if(this.loaded[key] == undefined) {
+			this.startLoading(key);
+			this.loader(key)(this.store(key));
+		}
+	};
+
+	Cache.prototype.startLoading = function(key) {
+		if(this.loading[key] == undefined) {
+			this.loading[key] = [];
+		}
+	};
+
+	Cache.prototype.store = function(key) {
+		return function(value) {
+			this.loaded[key] = value;
+			for(var i = 0; i < this.loading[key].length; i++) {
+				this.loading[key][i](value);
+			}
+			this.loading[key] = null;
+		}.bind(this);
+	};
+
+	return {
+		make: make
+	};
+
+	function make(loader) {
+		var cache = new Cache(loader);
+		return {
+			get: cache.get.bind(cache),
+			warmUp: cache.warmUp.bind(cache)
+		};
+	}
+}

src/js/main.js

@@ -4,7 +4,8 @@ window.addEventListener('load', function() {
 	dom = Dom();
 	screen = Screen(dom);
 	session = Session(async);
+	cache = Cache(async);
 	buttons = Buttons(session);
 	ui = UI(async, buttons, dom, screen, session);
-	automaton = Automaton(async, dom, messaging, screen, session, ui);
+	automaton = Automaton(async, cache, dom, messaging, screen, session, ui);
 });