up

G102-sequence/offlineClient.js

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+"use strict";
+
+(function() {
+	
+	class OfflineClient
+	{
+		constructor()
+		{
+			// Create a BroadcastChannel, if supported.
+			this._broadcastChannel = (typeof BroadcastChannel === "undefined" ? null : new BroadcastChannel("offline"));
+			
+			// Queue of messages received before a message callback is set.
+			this._queuedMessages = [];
+			
+			// The message callback.
+			this._onMessageCallback = null;
+			
+			// If BroadcastChannel is supported, listen for messages.
+			if (this._broadcastChannel)
+				this._broadcastChannel.onmessage = (e => this._OnBroadcastChannelMessage(e));
+		}
+		
+		_OnBroadcastChannelMessage(e)
+		{
+			// Have a message callback set: just forward the call.
+			if (this._onMessageCallback)
+			{
+				this._onMessageCallback(e);
+				return;
+			}
+			
+			// Otherwise the app hasn't loaded far enough to set a message callback.
+			// Buffer the incoming messages to replay when the app sets a callback.
+			this._queuedMessages.push(e);
+		}
+		
+		SetMessageCallback(f)
+		{
+			this._onMessageCallback = f;
+			
+			// Replay any queued messages through the handler, then clear the queue.
+			for (let e of this._queuedMessages)
+				this._onMessageCallback(e);
+			
+			this._queuedMessages.length = 0;
+		}
+	};
+	
+	// Create the offline client ASAP so we receive and start queueing any messages the SW broadcasts.
+	window.OfflineClientInfo = new OfflineClient();
+	
+}());
+