create interface for storage and wrap in-memory implementation in it

src/server/db.js

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2017 Google Inc.
+ *
+ * Use of this source code is governed by a MIT-style
+ * license that can be found in the LICENSE file or at
+ * https://opensource.org/licenses/MIT.
+ */
+
+/**
+ * InMemory data storage.
+ */
+export class InMemory {
+  /**
+   * Creates a new InMemory storage.
+   * @param {function} reducer - The game reducer.
+   */
+  constructor(reducer) {
+    this.reducer = reducer;
+    this.obj = {};
+  }
+
+  /**
+   * Write the game state to the in-memory object.
+   * @param {string} id - The game id.
+   * @param {object} store - A Redux store to persist.
+   */
+  set(id, store) {
+    this.obj[id] = store;
+  }
+
+  /**
+   * Read the game state from the in-memory object.
+   * @param {string} id - The game id.
+   * @returns {object} - A Redux store with the game state, or null
+   *                     if no game is found with this id.
+   */
+  get(id) {
+    if (id in this.obj) {
+      return this.obj[id];
+    }
+    return null;
+  }
+}

src/server/db.test.js

@@ -0,0 +1,23 @@
+/*
+ * Copyright 2017 Google Inc.
+ *
+ * Use of this source code is governed by a MIT-style
+ * license that can be found in the LICENSE file or at
+ * https://opensource.org/licenses/MIT.
+ */
+
+import { InMemory } from './db';
+import * as Redux from 'redux';
+
+test('basic', () => {
+  const db = new InMemory();
+  const reducer = () => {};
+  const store = Redux.createStore(reducer);
+
+  // Must return null when no game exists.
+  expect(db.get('gameid')).toEqual(null);
+  // Create game.
+  db.set('gameid', store);
+  // Must return created game.
+  expect(db.get('gameid')).toEqual(store);
+});

src/server/index.js

@@ -9,10 +9,9 @@
 const Koa = require('koa');
 const IO = require('koa-socket');
 const Redux = require('redux');
+import { InMemory } from './db';
 import { createGameReducer } from '../both/reducer';
 
-const games = {};
-
 function Server({game, numPlayers}) {
   const app = new Koa();
   const io = new IO();
@@ -21,32 +20,37 @@ function Server({game, numPlayers}) {
   io.attach(app);
 
   const reducer = createGameReducer({game, numPlayers});
+  const db = new InMemory(reducer);
 
   io.on('connection', (ctx) => {
     const socket = ctx.socket;
 
     socket.on('action', action => {
       const gameid = action._gameid;
+      const store = db.get(gameid);
 
-      if (!(gameid in games)) {
+      if (store == null) {
         return { error: 'game not found' };
       }
 
-      const store = games[gameid];
       const state = store.getState();
 
       if (state._id == action._id) {
         store.dispatch(action);
         socket.broadcast.emit('action', action);
+        db.set(gameid, store);
       }
     });
 
     socket.on('sync', gameid => {
-      if (!(gameid in games)) {
-        games[gameid] = Redux.createStore(reducer);
+      let store = null;
+      if (db.get(gameid) == null) {
+        store = Redux.createStore(reducer);
+        db.set(gameid, store);
+      } else {
+        store = db.get(gameid);
       }
 
-      const store = games[gameid];
       const state = store.getState();
       socket.emit('sync', state);
     });

src/server/index.test.js

@@ -74,6 +74,8 @@ test('action', () => {
   io.socket.receive('action', action);
   expect(io.socket.broadcast.emit.mock.calls.length).toBe(0);
 
+  io.socket.receive('sync', 'gameid');
+
   // Actions are broadcasted.
   action._gameid = 'gameid';
   action._id = 0;