feat: add option to allow usage of custom parser (#121)

This PR adds a new parser option to the adapter constructor to allow
setting a custom parser to use, defaulting to using notepack.io. This
would allow someone to use a different msgpack library if they wanted,
or even an entirely different protocol altogether (e.g. protobuf).

Related: socketio/socket.io-redis-adapter@73f6320

Signed-off-by: Matthew Peveler <matt@popsql.com>

Readme.md

@@ -161,6 +161,7 @@ option set to `true`.
 The following options are allowed:
 
 - `key`: the name of the key to pub/sub events on as prefix (`socket.io`)
+- `parser`: parser to use for encoding messages to Redis ([`notepack.io](https://www.npmjs.com/package/notepack.io))
 
 ### Emitter#to(room:String):BroadcastOperator
 ### Emitter#in(room:String):BroadcastOperator

lib/index.ts

@@ -27,17 +27,27 @@ enum RequestType {
   SERVER_SIDE_EMIT = 6,
 }
 
+interface Parser {
+  encode: (msg: any) => any;
+}
+
 export interface EmitterOptions {
   /**
    * @default "socket.io"
    */
   key?: string;
+  /**
+   * The parser to use for encoding messages sent to Redis.
+   * Defaults to notepack.io, a MessagePack implementation.
+   */
+  parser?: Parser;
 }
 
 interface BroadcastOptions {
   nsp: string;
   broadcastChannel: string;
   requestChannel: string;
+  parser: Parser;
 }
 
 interface BroadcastFlags {
@@ -57,13 +67,15 @@ export class Emitter<EmitEvents extends EventsMap = DefaultEventsMap> {
     this.opts = Object.assign(
       {
         key: "socket.io",
+        parser: msgpack,
       },
       opts
     );
     this.broadcastOptions = {
       nsp,
       broadcastChannel: this.opts.key + "#" + nsp + "#",
       requestChannel: this.opts.key + "-request#" + nsp + "#",
+      parser: this.opts.parser,
     };
   }
 
@@ -366,7 +378,7 @@ export class BroadcastOperator<EmitEvents extends EventsMap>
       except: [...this.exceptRooms],
     };
 
-    const msg = msgpack.encode([UID, packet, opts]);
+    const msg = this.broadcastOptions.parser.encode([UID, packet, opts]);
     let channel = this.broadcastOptions.broadcastChannel;
     if (this.rooms && this.rooms.size === 1) {
       channel += this.rooms.keys().next().value + "#";