feat: support resume urls (#8784)

Co-authored-by: Almeida <almeidx@pm.me>

packages/discord.js/src/client/websocket/WebSocketShard.js

@@ -64,6 +64,13 @@ class WebSocketShard extends EventEmitter {
      */
     this.sessionId = null;
 
+    /**
+     * The resume url for this shard
+     * @type {?string}
+     * @private
+     */
+    this.resumeURL = null;
+
     /**
      * The previous heartbeat ping of the shard
      * @type {number}
@@ -193,12 +200,14 @@ class WebSocketShard extends EventEmitter {
    * or reject if we couldn't connect
    */
   connect() {
-    const { gateway, client } = this.manager;
+    const { client } = this.manager;
 
     if (this.connection?.readyState === WebSocket.OPEN && this.status === Status.Ready) {
       return Promise.resolve();
     }
 
+    const gateway = this.resumeURL ?? this.manager.gateway;
+
     return new Promise((resolve, reject) => {
       const cleanup = () => {
         this.removeListener(WebSocketShardEvents.Close, onClose);
@@ -416,9 +425,10 @@ class WebSocketShard extends EventEmitter {
         this.emit(WebSocketShardEvents.Ready);
 
         this.sessionId = packet.d.session_id;
+        this.resumeURL = packet.d.resume_gateway_url;
         this.expectedGuilds = new Set(packet.d.guilds.map(d => d.id));
         this.status = Status.WaitingForGuilds;
-        this.debug(`[READY] Session ${this.sessionId}.`);
+        this.debug(`[READY] Session ${this.sessionId} | Resume url ${this.resumeURL}.`);
         this.lastHeartbeatAcked = true;
         this.sendHeartbeat('ReadyHeartbeat');
         break;
@@ -847,10 +857,11 @@ class WebSocketShard extends EventEmitter {
     // Step 4: Cache the old sequence (use to attempt a resume)
     if (this.sequence !== -1) this.closeSequence = this.sequence;
 
-    // Step 5: Reset the sequence and session id if requested
+    // Step 5: Reset the sequence, resume url and session id if requested
     if (reset) {
       this.sequence = -1;
       this.sessionId = null;
+      this.resumeURL = null;
     }
 
     // Step 6: reset the rate limit data

packages/discord.js/typings/index.d.ts

@@ -2995,6 +2995,7 @@ export class WebSocketShard extends EventEmitter {
   private sequence: number;
   private closeSequence: number;
   private sessionId: string | null;
+  private resumeURL: string | null;
   private lastPingTimestamp: number;
   private lastHeartbeatAcked: boolean;
   private readonly ratelimit: {