Add QueuedEventEmitter, use it for GuildSavedMessages events

src/Queue.ts

@@ -0,0 +1,36 @@
+type QueueFn = (...args: any[]) => Promise<any>;
+
+export class Queue {
+  protected running: boolean = false;
+  protected queue: QueueFn[] = [];
+  protected timeout: number = 10 * 1000;
+
+  public add(fn) {
+    const promise = new Promise(resolve => {
+      this.queue.push(async () => {
+        await fn();
+        resolve();
+      });
+
+      if (!this.running) this.next();
+    });
+
+    return promise;
+  }
+
+  public next() {
+    this.running = true;
+
+    if (this.queue.length === 0) {
+      this.running = false;
+      return;
+    }
+
+    const fn = this.queue.shift();
+    new Promise(resolve => {
+      // Either fn() completes or the timeout is reached
+      fn().then(resolve);
+      setTimeout(resolve, this.timeout);
+    }).then(() => this.next());
+  }
+}

src/QueuedEventEmitter.ts

@@ -0,0 +1,38 @@
+import { Queue } from "./Queue";
+
+type Listener = (...args: any[]) => void;
+
+export class QueuedEventEmitter {
+  protected listeners: Map<string, Listener[]>;
+  protected queue: Queue;
+
+  constructor() {
+    this.listeners = new Map();
+    this.queue = new Queue();
+  }
+
+  on(eventName: string, listener: Listener) {
+    if (!this.listeners.has(eventName)) {
+      this.listeners.set(eventName, []);
+    }
+
+    this.listeners.get(eventName).push(listener);
+  }
+
+  off(eventName: string, listener: Listener) {
+    if (!this.listeners.has(eventName)) {
+      return;
+    }
+
+    const listeners = this.listeners.get(eventName);
+    listeners.splice(listeners.indexOf(listener), 1);
+  }
+
+  emit(eventName: string, args: any[] = []) {
+    const listeners = [...(this.listeners.get(eventName) || []), ...(this.listeners.get("*") || [])];
+
+    listeners.forEach(listener => {
+      this.queue.add(listener.bind(null, args));
+    });
+  }
+}

src/data/GuildSavedMessages.ts

@@ -1,7 +1,7 @@
 import { Brackets, getRepository, Repository } from "typeorm";
 import { BaseRepository } from "./BaseRepository";
 import { ISavedMessageData, SavedMessage } from "./entities/SavedMessage";
-import EventEmitter from "events";
+import { QueuedEventEmitter } from "../QueuedEventEmitter";
 import { GuildChannel, Message } from "eris";
 import moment from "moment-timezone";
 
@@ -11,12 +11,12 @@ const RETENTION_PERIOD = 7 * 24 * 60 * 60 * 1000; // 1 week
 
 export class GuildSavedMessages extends BaseRepository {
   private messages: Repository<SavedMessage>;
-  public events: EventEmitter;
+  public events: QueuedEventEmitter;
 
   constructor(guildId) {
     super(guildId);
     this.messages = getRepository(SavedMessage);
-    this.events = new EventEmitter();
+    this.events = new QueuedEventEmitter();
 
     this.cleanup();
     setInterval(() => this.cleanup(), CLEANUP_INTERVAL);