Added cloud functions to remove old signals/events

functions/index.js

-// const functions = require("firebase-functions");
+const functions = require("firebase-functions");
+const admin = require("firebase-admin");
+admin.initializeApp(functions.config().firebase);
 
-// // Create and Deploy Your First Cloud Functions
-// // https://firebase.google.com/docs/functions/write-firebase-functions
-//
-// exports.helloWorld = functions.https.onRequest((request, response) => {
-//   functions.logger.info("Hello logs!", {structuredData: true});
-//   response.send("Hello from Firebase!");
-// });
+/* Delete signals older than 15m */
+exports.deleteOldSignals = functions.pubsub
+    .schedule("* * * * *").onRun(() => {
+      const ref = admin.database().ref("signals"); // reference to the items
+      const now = Date.now();
+      const cutoff = now - 2 * 60 * 1000; // 2m
+      const oldItemsQuery = ref.orderByChild("timestamp").endAt(cutoff);
+      return oldItemsQuery.once("value", function(snapshot) {
+        // create a map with all children that need to be removed
+        const updates = {};
+        snapshot.forEach(function(child) {
+          updates[child.key] = null;
+        });
+        // execute all updates in one go and return the result
+        return ref.update(updates);
+      });
+    });
+
+/* Delete events older than 5 hours */
+exports.deleteOldEvents = functions.pubsub
+    .schedule("0 * * * *").onRun(() => {
+      const ref = admin.database().ref("events"); // reference to the items
+      const now = Date.now();
+      const cutoff = now - 5 * 60 * 60 * 1000;
+      const oldItemsQuery = ref.orderByChild("timestamp").endAt(cutoff);
+      return oldItemsQuery.once("value", function(snapshot) {
+        // create a map with all children that need to be removed
+        const updates = {};
+        snapshot.forEach(function(child) {
+          updates[child.key] = null;
+        });
+        // execute all updates in one go and return the result
+        return ref.update(updates);
+      });
+    });