Fixed onDisconnect logic to use deviceId

presence-firestore/README.md

@@ -38,7 +38,7 @@ To deploy the sample to your Firebase app,
 1. Run `npm install` to install dependencies for the server-side [functions](functions/) as detailed above.
 2. From this top-level sample directory, deploy the `Realtime Database` trigger defined in [functions](functions/) to `Firebase Functions` and the [public](public/) directory app to `Firebase Hosting`.
 
-Assumimg you've created a Firebase application called `firebase-example-123` (make sure it's upgraded to the Spark plan and that `Anonymous Authentication` are enabled).
+Assumimg you've created a Firebase application called `firebase-example-123` (make sure it's upgraded to the Blaze plan and that `Anonymous Authentication` are enabled).
 
 ```sh
 firebase use --add firebase-example-123

presence-firestore/functions/index.js

@@ -24,16 +24,20 @@ admin.initializeApp();
 // detects authentication from the environment.
 const firestore = admin.firestore();
 
-// Create a new function which is triggered on changes to /status/{uid}
+// Create a new function which is triggered on changes to /status/{uid}/sessions/{sessionId}
 // Note: This is a Realtime Database trigger, *not* Firestore.
-exports.onUserStatusChanged = functions.database.ref('/status/{uid}').onUpdate(
+exports.onUserStatusChanged = functions.database.ref('/status/{uid}/sessions/{sessionId}').onUpdate(
     async (change, context) => {
       // Get the data written to Realtime Database
       const eventStatus = change.after.val();
 
+      const sessionId = context.params.sessionId;
+
       // Then use other event data to create a reference to the
       // corresponding Firestore document.
-      const userStatusFirestoreRef = firestore.doc(`status/${context.params.uid}`);
+      const userFirestoreRef = firestore.doc(`status/${context.params.uid}`);
+      const userSessionCollectionRef = userFirestoreRef.collection('sessions');
+      const sessionStatusFirestoreRef = userSessionCollectionRef.doc(sessionId);
 
       // It is likely that the Realtime Database change that triggered
       // this event has already been overwritten by a fast change in
@@ -47,11 +51,20 @@ exports.onUserStatusChanged = functions.database.ref('/status/{uid}').onUpdate(
       if (status.last_changed > eventStatus.last_changed) {
         return null;
       }
-
       // Otherwise, we convert the last_changed field to a Date
       eventStatus.last_changed = new Date(eventStatus.last_changed);
 
-      // ... and write it to Firestore.
-      return userStatusFirestoreRef.set(eventStatus);
+      if(status.state === 'offline') {
+        // ... and write it to Firestore.
+        await sessionStatusFirestoreRef.delete();
+
+        if ((await userSessionCollectionRef.get()).empty) {
+          return userFirestoreRef.delete();
+        }
+      } else { // TODO(mtewani): Do we really need to handle this?
+        await userFirestoreRef.set({ uid: context.params.uid });
+        return sessionStatusFirestoreRef.set(status);
+      }
+      return null;
     });
 // [END presence_sync_function]

presence-firestore/public/index.js

@@ -21,10 +21,11 @@ function rtdb_presence() {
 
     // Create a reference to this user's specific status node.
     // This is where we will store data about being online/offline.
-    var userStatusDatabaseRef = firebase.database().ref('/status/' + uid);
+    // `push()` will add a new key to the user's path, acting as a sessionId
+    var sessionStatusDatabaseRef = firebase.database().ref('/status/' + uid + '/sessions').push();
 
     // We'll create two constants which we will write to 
-    // the Realtime database when this device is offline
+    // the Realtime database when this session is offline
     // or online.
     var isOfflineForDatabase = {
         state: 'offline',
@@ -49,25 +50,26 @@ function rtdb_presence() {
         // method to add a set which will only trigger once this 
         // client has disconnected by closing the app, 
         // losing internet, or any other means.
-        userStatusDatabaseRef.onDisconnect().set(isOfflineForDatabase).then(function() {
+        sessionStatusDatabaseRef.onDisconnect().set(isOfflineForDatabase).then(function() {
             // The promise returned from .onDisconnect().set() will
             // resolve as soon as the server acknowledges the onDisconnect() 
             // request, NOT once we've actually disconnected:
             // https://firebase.google.com/docs/reference/js/firebase.database.OnDisconnect
 
             // We can now safely set ourselves as 'online' knowing that the
             // server will mark us as offline once we lose connection.
-            userStatusDatabaseRef.set(isOnlineForDatabase);
+            sessionStatusDatabaseRef.set(isOnlineForDatabase);
         });
     });
     // [END rtdb_presence]
 }
 
-function rtdb_and_local_fs_presence() {
+async function rtdb_and_local_fs_presence() {
     // [START rtdb_and_local_fs_presence]
     // [START_EXCLUDE]
     var uid = firebase.auth().currentUser.uid;
-    var userStatusDatabaseRef = firebase.database().ref('/status/' + uid);
+    var sessionStatusDatabaseRef = await firebase.database().ref('/status/' + uid + '/sessions').push();
+    var sessionId = sessionStatusDatabaseRef.key;
 
     var isOfflineForDatabase = {
         state: 'offline',
@@ -80,34 +82,43 @@ function rtdb_and_local_fs_presence() {
     };
 
     // [END_EXCLUDE]
-    var userStatusFirestoreRef = firebase.firestore().doc('/status/' + uid);
+    var userFirestoreRef = firebase.firestore().collection('status').doc(uid);
+    await userFirestoreRef.set({ uid }); // In case the user's id document doesn't already exist.
+
+    var sessionsCollectionRef = userFirestoreRef.collection('sessions');
+    var sessionStatusFirestoreRef = sessionsCollectionRef.doc(sessionId);
+
 
     // Firestore uses a different server timestamp value, so we'll 
     // create two more constants for Firestore state.
-    var isOfflineForFirestore = {
-        state: 'offline',
-        last_changed: firebase.firestore.FieldValue.serverTimestamp(),
-    };
-
     var isOnlineForFirestore = {
         state: 'online',
         last_changed: firebase.firestore.FieldValue.serverTimestamp(),
     };
 
-    firebase.database().ref('.info/connected').on('value', function(snapshot) {
-        if (snapshot.val() == false) {
-            // Instead of simply returning, we'll also set Firestore's state
-            // to 'offline'. This ensures that our Firestore cache is aware
-            // of the switch to 'offline.'
-            userStatusFirestoreRef.set(isOfflineForFirestore);
+    // When a user goes offline, it reads from the cache to know how many sessions are left.
+    // This listener is to ensure that the full session cache is populated and can be read from when offline.
+    sessionsCollectionRef.onSnapshot(() => {});
+
+    firebase.database().ref('.info/connected').on('value', async function(snapshot) {
+        if (snapshot.val() === false) {
+            // Instead of simply returning, we'll also remove the session id from the user, 
+            // and if no sessions are left, we should delete the user as well.
+            // This ensures that our Firestore cache is aware that the session and/or user has been deleted
+            sessionStatusFirestoreRef.delete();
+            const sessionCollection = await sessionsCollectionRef.get();
+            if(sessionCollection.empty) {
+                userFirestoreRef.delete();
+            }
             return;
         };
 
-        userStatusDatabaseRef.onDisconnect().set(isOfflineForDatabase).then(function() {
-            userStatusDatabaseRef.set(isOnlineForDatabase);
+        sessionStatusDatabaseRef.onDisconnect().set(isOfflineForDatabase).then(function() {
+            sessionStatusDatabaseRef.set(isOnlineForDatabase);
 
             // We'll also add Firestore set here for when we come online.
-            userStatusFirestoreRef.set(isOnlineForFirestore);
+            userFirestoreRef.set({ uid });
+            sessionStatusFirestoreRef.set(isOnlineForFirestore);
         });
     });
     // [END rtdb_and_local_fs_presence]
@@ -116,7 +127,7 @@ function rtdb_and_local_fs_presence() {
 function fs_listen() {
     // [START fs_onsnapshot]
     userStatusFirestoreRef.onSnapshot(function(doc) {
-        var isOnline = doc.data().state == 'online';
+        var isOnline = !doc.empty;
         // ... use isOnline
     });
     // [END fs_onsnapshot]
@@ -126,7 +137,6 @@ function fs_listen_online() {
     var history = document.querySelector('#history');
     // [START fs_onsnapshot_online]
     firebase.firestore().collection('status')
-        .where('state', '==', 'online')
         .onSnapshot(function(snapshot) {
             snapshot.docChanges().forEach(function(change) {
                 if (change.type === 'added') {