Add update checker and notifier for Interface.

scripts/system/checkForUpdates.js

@@ -0,0 +1,54 @@
+//  checkForUpdates.js
+//
+//  Created by Kalila L. on 8/27/20
+//  Copyright 2020 Vircadia contributors.
+//
+//  Distributed under the Apache License, Version 2.0.
+//  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
+
+Script.include("/~/system/libraries/utils.js");
+var networkingConstants = Script.require("./libraries/networkingConstants.js");
+
+// We'll want a way to specify this later, auto detection can also be a thing, but strictly optional.
+var currentBuildType = "latest";
+var currentVersion = HifiAbout.buildVersion; 
+
+// Notification Variables
+var NOTIFICATION_CHANNEL = "System-Notifications";
+var NOTIFICATION_TYPE = "Update-Notification";
+var NOTIFICATION_CATEGORY = "Interface";
+var notificationText = "An update is available: ";
+var notificationColor = { red: 137, green: 63, blue: 255 };
+
+function retrieveMetadata() {
+    var requireMetadata = Script.require(networkingConstants.interfaceMetadataSource + '?' + Date.now());
+    
+    if (requireMetadata) {
+        return requireMetadata;
+    } else {
+        return false;
+    }
+}
+
+function checkForUpdates() {
+    var retrievedMetadata = retrieveMetadata();
+    
+    // Don't check for updates on a dev build.
+    if (retrievedMetadata && currentVersion !== "dev") {
+        var checkVersion = semanticVersionCompare(currentVersion, retrievedMetadata[currentBuildType].version);
+        
+        // An update is available!
+        if (checkVersion === -1) {
+            Messages.sendMessage(NOTIFICATION_CHANNEL, JSON.stringify({
+                type: NOTIFICATION_TYPE,
+                category: NOTIFICATION_CATEGORY,
+                channel: "Local",
+                position: MyAvatar.position,
+                colour: notificationColor,
+                message: notificationText + retrievedMetadata[currentBuildType].version,
+            }));
+        }
+    }
+}
+
+checkForUpdates();