Implement TypedEventEmitter for better TS support (#2018)

We're using stringly typed events everywhere, this is the first step for
better typescript support with our event emitters before we replace it
with something much better for React support.

src/models/base-model.ts

@@ -0,0 +1,51 @@
+/*
+Copyright 2021 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import { EventEmitter } from "events";
+
+/**
+ * Typed Event Emitter class which can act as a Base Model for all our model
+ * and communication events.
+ * This makes it much easier for us to distinguish between events, as we now need
+ * to properly type this, so that our events are not stringly-based and prone
+ * to silly typos.
+ */
+export abstract class BaseModel<Events extends string> extends EventEmitter {
+    public on(event: Events, listener: (...args: any[]) => void): this {
+        super.on(event, listener);
+        return this;
+    }
+
+    public once(event: Events, listener: (...args: any[]) => void): this {
+        super.once(event, listener);
+        return this;
+    }
+
+    public off(event: Events, listener: (...args: any[]) => void): this {
+        super.off(event, listener);
+        return this;
+    }
+
+    public addListener(event: Events, listener: (...args: any[]) => void): this {
+        super.addListener(event, listener);
+        return this;
+    }
+
+    public removeListener(event: Events, listener: (...args: any[]) => void): this {
+        super.removeListener(event, listener);
+        return this;
+    }
+}

src/models/thread.ts

@@ -14,12 +14,12 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import { EventEmitter } from "events";
 import { MatrixClient } from "../matrix";
 import { MatrixEvent } from "./event";
 import { EventTimeline } from "./event-timeline";
 import { EventTimelineSet } from './event-timeline-set';
 import { Room } from './room';
+import { BaseModel } from "./base-model";
 
 export enum ThreadEvent {
     New = "Thread.new",
@@ -30,7 +30,7 @@ export enum ThreadEvent {
 /**
  * @experimental
  */
-export class Thread extends EventEmitter {
+export class Thread extends BaseModel<ThreadEvent> {
     /**
      * A reference to the event ID at the top of the thread
      */
@@ -183,29 +183,4 @@ export class Thread extends EventEmitter {
     public has(eventId: string): boolean {
         return this.timelineSet.findEventById(eventId) instanceof MatrixEvent;
     }
-
-    public on(event: ThreadEvent, listener: (...args: any[]) => void): this {
-        super.on(event, listener);
-        return this;
-    }
-
-    public once(event: ThreadEvent, listener: (...args: any[]) => void): this {
-        super.once(event, listener);
-        return this;
-    }
-
-    public off(event: ThreadEvent, listener: (...args: any[]) => void): this {
-        super.off(event, listener);
-        return this;
-    }
-
-    public addListener(event: ThreadEvent, listener: (...args: any[]) => void): this {
-        super.addListener(event, listener);
-        return this;
-    }
-
-    public removeListener(event: ThreadEvent, listener: (...args: any[]) => void): this {
-        super.removeListener(event, listener);
-        return this;
-    }
 }