MongoDB connector

package.json

@@ -87,6 +87,7 @@
     "koa-helmet": "^3.2.0",
     "koa-webpack": "^1.0.0",
     "lint-staged": "^6.0.1",
+    "mongo-mock": "^3.1.0",
     "open-browser-webpack-plugin": "0.0.5",
     "prettier": "^1.10.2",
     "react": "^16.0.0",
@@ -113,6 +114,8 @@
     "koa-router": "^7.2.1",
     "koa-socket": "^4.4.0",
     "koa-static": "^4.0.1",
+    "lru-native": "^0.4.0",
+    "mongodb": "^3.0.3",
     "mousetrap": "^1.6.1",
     "prop-types": "^15.5.10",
     "react-json-view": "^1.13.0",

src/client/multiplayer/multiplayer.js

@@ -58,7 +58,7 @@ export class Multiplayer {
         this.socket.emit(
           'action',
           action,
-          state._id,
+          state._stateID,
           this.gameID,
           this.playerID
         );

src/core/reducer.js

@@ -36,7 +36,7 @@ export function createGameReducer({ game, numPlayers, multiplayer }) {
     // A monotonically non-decreasing ID to ensure that
     // state updates are only allowed from clients that
     // are at the same version that the server.
-    _id: 0,
+    _stateID: 0,
 
     // A snapshot of this object so that actions can be
     // replayed over it to view old snapshots.
@@ -84,7 +84,7 @@ export function createGameReducer({ game, numPlayers, multiplayer }) {
         ctx = { ...ctx, _random: PRNGState.get() };
 
         const log = [...state.log, action];
-        return { ...state, G, ctx, log, _id: state._id + 1 };
+        return { ...state, G, ctx, log, _stateID: state._stateID + 1 };
       }
 
       case Actions.MAKE_MOVE: {
@@ -110,7 +110,7 @@ export function createGameReducer({ game, numPlayers, multiplayer }) {
         }
 
         const log = [...state.log, action];
-        state = { ...state, G, ctx, log, _id: state._id + 1 };
+        state = { ...state, G, ctx, log, _stateID: state._stateID + 1 };
 
         // If we're on the client, just process the move
         // and no triggers in multiplayer mode.

src/core/reducer.test.js

@@ -23,15 +23,15 @@ const game = Game({
 
 const endTurn = () => gameEvent('endTurn');
 
-test('_id is incremented', () => {
+test('_stateID is incremented', () => {
   const reducer = createGameReducer({ game });
 
   let state = undefined;
 
   state = reducer(state, makeMove('unknown'));
-  expect(state._id).toBe(1);
+  expect(state._stateID).toBe(1);
   state = reducer(state, endTurn());
-  expect(state._id).toBe(2);
+  expect(state._stateID).toBe(2);
 });
 
 test('makeMove', () => {

src/server/db.js

@@ -6,6 +6,9 @@
  * https://opensource.org/licenses/MIT.
  */
 
+const MongoClient = require('mongodb').MongoClient;
+const LRUCache = require('lru-native');
+
 /**
  * InMemory data storage.
  */
@@ -17,6 +20,14 @@ export class InMemory {
     this.games = new Map();
   }
 
+  /**
+   * Connect.
+   * No-op for the InMemory instance.
+   */
+  async connect() {
+    return;
+  }
+
   /**
    * Write the game state to the in-memory object.
    * @param {string} id - The game id.
@@ -35,12 +46,96 @@ export class InMemory {
   async get(id) {
     return await this.games.get(id);
   }
+
   /**
-   * Read the game state from the in-memory object.
+   * Check if a particular game id exists.
    * @param {string} id - The game id.
    * @returns {boolean} - True if a game with this id exists.
    */
   async has(id) {
     return await this.games.has(id);
   }
 }
+
+/**
+ * MongoDB connector.
+ */
+export class Mongo {
+  /**
+   * Creates a new Mongo connector object.
+   */
+  constructor({ url, dbname, cacheSize, mockClient }) {
+    if (cacheSize === undefined) cacheSize = 1000;
+
+    this.client = mockClient || MongoClient;
+    this.url = url;
+    this.dbname = dbname;
+    this.cache = new LRUCache({ maxElements: cacheSize });
+  }
+
+  /**
+   * Connect to the instance.
+   */
+  async connect() {
+    const c = await this.client.connect(this.url);
+    this.db = c.db(this.dbname);
+    return;
+  }
+
+  /**
+   * Write the game state.
+   * @param {string} id - The game id.
+   * @param {object} store - A game state to persist.
+   */
+  async set(id, state) {
+    this.cache.set(id, state);
+
+    const col = this.db.collection(id);
+    delete state._id;
+    await col.insert(state);
+
+    return;
+  }
+
+  /**
+   * Read the game state.
+   * @param {string} id - The game id.
+   * @returns {object} - A game state, or undefined
+   *                     if no game is found with this id.
+   */
+  async get(id) {
+    const item = this.cache.get(id);
+    if (item !== undefined) {
+      return item;
+    }
+
+    const col = this.db.collection(id);
+    const docs = await col
+      .find()
+      .sort({ _id: -1 })
+      .limit(1)
+      .toArray();
+
+    this.cache.set(id, docs[0]);
+    return docs[0];
+  }
+
+  /**
+   * Check if a particular game exists.
+   * @param {string} id - The game id.
+   * @returns {boolean} - True if a game with this id exists.
+   */
+  async has(id) {
+    const item = this.cache.get(id);
+    if (item !== undefined) {
+      return true;
+    }
+
+    const col = this.db.collection(id);
+    const docs = await col
+      .find()
+      .limit(1)
+      .toArray();
+    return docs.length > 0;
+  }
+}